🛡️ Sentinel: [CRITICAL] Fix local code execution via malicious git config

.jules/sentinel.md

@@ -0,0 +1,4 @@
+## 2025-06-25 - Prevent Git Core fsmonitor Local Code Execution
+**Vulnerability:** Running `git` commands (like `rev-parse`, `diff`, `ls-files`) via `subprocess.run` inside an untrusted directory can lead to arbitrary code execution if the directory contains a malicious `.git/config` configuring `core.fsmonitor` to run a malicious executable.
+**Learning:** `git` executes commands specified in the repository's configuration under `core.fsmonitor` upon certain operations, which inherently executes code when operating on untrusted repositories without proper safety checks.
+**Prevention:** Always invoke `git` operations via `subprocess` against potentially untrusted directories with the explicit configuration `("-c", "core.fsmonitor=false")` (typically defined as `_SAFE_GIT_CONFIG`) to suppress arbitrary code execution via malicious `.git/config` settings.

src/wardline/core/delta.py

@@ -12,6 +12,9 @@
     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)
     that have changed since `ref`, including staged, unstaged, and untracked changes.
@@ -22,7 +25,7 @@ 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 +41,7 @@ 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 +57,7 @@ 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 +71,7 @@ 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

@@ -55,6 +55,7 @@
 
 LEGIS_ARTIFACT_KEY_ENV = "WARDLINE_LEGIS_ARTIFACT_KEY"
 SIG_PREFIX = "hmac-sha256:v2:"
+_SAFE_GIT_CONFIG = ("-c", "core.fsmonitor=false")
 ARTIFACT_SIGNATURE_FIELD = "artifact_signature"
 
 # Cross-member scan-artifact keys that legis reads with a DEFAULT, not a hard
@@ -199,7 +200,7 @@ 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 +216,7 @@ 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")