fix(security): close CodeQL go/command-injection in runGit (#55)

CodeQL alert #33 (Critical): exec.Command("git", ...) in runGit
received user-controlled strings (commit message bytes from author /
subject, and paths from note keys). Although exec.Command uses argv
(no shell) which makes the standard shell-injection vector inert, git
itself has flag-based attack surface (e.g. `--upload-pack=cmd`,
`-c core.sshCommand=...`) that CodeQL is right to flag.

Defense in depth:

1. `runGit` now enforces:
   - notesDir must be non-empty and must not start with "-" (prevents
     it being parsed as a git top-level flag).
   - args[0] must be in a closed allow-list of subcommands (init /
     config / add / log). Commit is deliberately routed elsewhere
     (see #2).
   - Any arg after a literal "--" must satisfy filepath.IsLocal —
     this continues the sanitiser from PR #44 and is what CodeQL
     recognises.

2. `gitCommit` is a new helper that runs `git commit --no-gpg-sign
   -F -` and pipes the message via stdin. The message bytes therefore
   never appear in argv, cutting the only remaining taint flow from
   user input to exec.Command args.

3. autoCommit's commit call switched from runGit(..., "commit", "-m",
   msg) to gitCommit(notesDir, msg).

Tested locally: 104/104 tests passing in internal/notes/.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aksOps

internal/notes/history.go

@@ -100,8 +100,51 @@ func initRepo(notesDir string) error {
 	return nil
 }
 
+// allowedGitSubcommands is the closed set of git subcommands runGit
+// will invoke. This keeps future callers from accidentally passing a
+// user-controlled string in the subcommand slot, and gives CodeQL a
+// recognizable allow-list sanitizer for the go/command-injection rule.
+var allowedGitSubcommands = map[string]bool{
+	"init":   true,
+	"config": true,
+	"add":    true,
+	"log":    true,
+}
+
 // runGit invokes `git -C <notesDir> <args>` and returns combined output.
+//
+// Security:
+//   - No shell — exec.Command takes argv directly.
+//   - notesDir must be non-empty and must not begin with "-" (which
+//     would let it be parsed as a git top-level flag).
+//   - args[0] must be in allowedGitSubcommands.
+//   - Any arg that follows a literal "--" separator must satisfy
+//     filepath.IsLocal — it's expected to be an in-tree relative path.
+//
+// runGit deliberately does NOT handle `commit`. Commit messages come
+// from user input; they're routed through gitCommit which pipes the
+// message via stdin so it never touches argv (see gitCommit below).
 func runGit(notesDir string, args ...string) (string, error) {
+	if notesDir == "" || strings.HasPrefix(notesDir, "-") {
+		return "", fmt.Errorf("runGit: invalid notesDir")
+	}
+	if len(args) == 0 {
+		return "", fmt.Errorf("runGit: no subcommand")
+	}
+	if !allowedGitSubcommands[args[0]] {
+		return "", fmt.Errorf("runGit: disallowed subcommand %q", args[0])
+	}
+	seenDDash := false
+	for _, a := range args[1:] {
+		if a == "--" {
+			seenDDash = true
+			continue
+		}
+		if seenDDash && !filepath.IsLocal(a) {
+			return "", fmt.Errorf("runGit: non-local path arg %q", a)
+		}
+	}
+
 	full := append([]string{"-C", notesDir}, args...)
 	cmd := exec.Command("git", full...)
 	// Detach from any inherited GIT_* env — the caller's config must
@@ -117,6 +160,28 @@ func runGit(notesDir string, args ...string) (string, error) {
 	return buf.String(), err
 }
 
+// gitCommit runs `git commit` reading the message from stdin. The
+// message is never passed as a command-line argument, removing the
+// only path by which user-controlled bytes could have reached the git
+// argv. `--no-gpg-sign` keeps the commit unsigned (we rely on cosign
+// for release signing, not per-commit GPG).
+func gitCommit(notesDir, msg string) (string, error) {
+	if notesDir == "" || strings.HasPrefix(notesDir, "-") {
+		return "", fmt.Errorf("gitCommit: invalid notesDir")
+	}
+	cmd := exec.Command("git", "-C", notesDir, "commit", "--no-gpg-sign", "--allow-empty-message", "-F", "-")
+	cmd.Env = append(os.Environ(),
+		"GIT_CONFIG_GLOBAL=/dev/null",
+		"GIT_CONFIG_SYSTEM=/dev/null",
+	)
+	cmd.Stdin = strings.NewReader(msg)
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+	err := cmd.Run()
+	return buf.String(), err
+}
+
 // truncateForCommit caps a string to maxCommitMsgBytes (UTF-8-safe: cut
 // at byte boundary, then trim trailing invalid UTF-8 fragment by
 // walking back to a rune boundary).
@@ -216,10 +281,7 @@ func autoCommit(notesDir, key, author, subject string, deleted bool) {
 	// which is the desired behavior. `git commit` exits non-zero on
 	// "nothing to commit" — treat that as a silent no-op rather than
 	// a warning.
-	if out, err := runGit(notesDir, "commit",
-		"--no-gpg-sign",
-		"-m", msg,
-	); err != nil {
+	if out, err := gitCommit(notesDir, msg); err != nil {
 		if strings.Contains(out, "nothing to commit") ||
 			strings.Contains(out, "no changes added") {
 			return