🛡️ Sentinel: [CRITICAL/HIGH] Fix git fsmonitor RCE vulnerability

.jules/sentinel.md

@@ -0,0 +1,4 @@
+## $(date +%Y-%m-%d) - Prevent RCE via malicious .git/config core.fsmonitor
+**Vulnerability:** Invoking `git` operations (like `diff` or `ls-files`) programmatically in untrusted repositories without overriding configuration can allow arbitrary command execution via a malicious `.git/config` setting `core.fsmonitor`.
+**Learning:** `subprocess.run(["git", ...])` is not completely safe, even for seemingly innocuous commands like `git diff` or `git rev-parse`. A repository downloaded from an untrusted source might carry a customized configuration that points to an executable bundled with the repository.
+**Prevention:** When invoking `git` via `subprocess` against potentially untrusted directories, always apply the configuration `("-c", "core.fsmonitor=false")` (typically defined as `_SAFE_GIT_CONFIG`) directly in the command arguments.

src/wardline/core/delta.py

@@ -11,6 +11,8 @@
 if TYPE_CHECKING:
     from wardline.scanner.index import Entity
 
+_SAFE_GIT_CONFIG = ("-c", "core.fsmonitor=false")
+
 
 def get_changed_files_since(ref: str, root: Path) -> set[str]:
     """Get the set of file paths (repo-relative, POSIX-style matching Location.path)
@@ -22,7 +24,7 @@ def get_changed_files_since(ref: str, root: Path) -> set[str]:
     # 1. Get the git toplevel directory.
     try:
         res = subprocess.run(
-            ["git", "rev-parse", "--show-toplevel"],
+            ["git", *_SAFE_GIT_CONFIG, "rev-parse", "--show-toplevel"],
             cwd=root,
             capture_output=True,
             text=True,
@@ -38,7 +40,7 @@ def get_changed_files_since(ref: str, root: Path) -> set[str]:
     # 2. Resolve ref to a verified object id before passing it to git diff.
     try:
         res = subprocess.run(
-            ["git", "rev-parse", "--verify", "--end-of-options", ref],
+            ["git", *_SAFE_GIT_CONFIG, "rev-parse", "--verify", "--end-of-options", ref],
             cwd=git_toplevel,
             capture_output=True,
             text=True,
@@ -54,7 +56,7 @@ def get_changed_files_since(ref: str, root: Path) -> set[str]:
     # 3. Get changed files since ref (committed since ref, staged, unstaged).
     try:
         res = subprocess.run(
-            ["git", "diff", "--name-only", verified_ref, "--"],
+            ["git", *_SAFE_GIT_CONFIG, "diff", "--name-only", verified_ref, "--"],
             cwd=git_toplevel,
             capture_output=True,
             text=True,
@@ -68,7 +70,7 @@ def get_changed_files_since(ref: str, root: Path) -> set[str]:
     # 4. Get untracked files.
     try:
         res = subprocess.run(
-            ["git", "ls-files", "--others", "--exclude-standard"],
+            ["git", *_SAFE_GIT_CONFIG, "ls-files", "--others", "--exclude-standard"],
             cwd=git_toplevel,
             capture_output=True,
             text=True,

src/wardline/core/legis.py

@@ -73,6 +73,8 @@
 SCAN_SCOPE_FIELD = "scan_scope"
 SCAN_SCOPE_SCHEMA = "wardline-legis-scan-scope-1"
 
+_SAFE_GIT_CONFIG = ("-c", "core.fsmonitor=false")
+
 # The one shared vocabulary — legis carries these 8 tiers verbatim (TRUST_TIERS in
 # legis ingest.py). Sourced from the lattice so the two can never drift.
 TRUST_TIERS: frozenset[str] = frozenset(t.value for t in TaintState)
@@ -199,7 +201,7 @@ def _git_tree_sha(root: Path) -> str | None:
     """
     try:
         rev = subprocess.run(
-            ["git", "rev-parse", "HEAD^{tree}"],
+            ["git", *_SAFE_GIT_CONFIG, "rev-parse", "HEAD^{tree}"],
             cwd=root,
             capture_output=True,
             text=True,
@@ -215,7 +217,7 @@ def _git_repo_root(root: Path) -> Path | None:
     """The containing git repository root, or None when unavailable."""
     try:
         rev = subprocess.run(
-            ["git", "rev-parse", "--show-toplevel"],
+            ["git", *_SAFE_GIT_CONFIG, "rev-parse", "--show-toplevel"],
             cwd=root,
             capture_output=True,
             text=True,

tests/unit/core/test_delta.py

@@ -43,8 +43,24 @@ def run_dispatch(args, **kwargs):
     res = get_changed_files_since("HEAD~1", root)
 
     assert res == {"foo.py", "bar.py", "baz.py"}
-    assert mock_run.call_args_list[1].args[0] == ["git", "rev-parse", "--verify", "--end-of-options", "HEAD~1"]
-    assert mock_run.call_args_list[2].args[0] == ["git", "diff", "--name-only", "abc123", "--"]
+    assert mock_run.call_args_list[1].args[0] == [
+        "git",
+        "-c",
+        "core.fsmonitor=false",
+        "rev-parse",
+        "--verify",
+        "--end-of-options",
+        "HEAD~1",
+    ]
+    assert mock_run.call_args_list[2].args[0] == [
+        "git",
+        "-c",
+        "core.fsmonitor=false",
+        "diff",
+        "--name-only",
+        "abc123",
+        "--",
+    ]
 
 
 @patch("subprocess.run")