Function assertDanglingSymlinkSafe

src/main/lib/git/security/secure-fs.ts:224–273

* Handle the ENOENT case: check if fullPath is a dangling symlink pointing outside * the worktree, or if it truly doesn't exist (in which case validate parent chain). * * Attack scenario this prevents: * - Repo contains `docs/config.yml` → symlink to `~/.ssh/some_new_file` (doesn't exist) * - r

(
	worktreePath: string,
	fullPath: string,
)

 * @throws PathValidationError if symlink escapes worktree
 */
async function assertDanglingSymlinkSafe(
	worktreePath: string,
	fullPath: string,
): Promise<void> {
	const worktreeReal = await realpath(worktreePath);

	try {
		// Check if the path itself exists (as a symlink or otherwise)
		const stats = await lstat(fullPath);

		if (stats.isSymbolicLink()) {
			// It's a dangling symlink - validate where it points
			const linkTarget = await readlink(fullPath);
			const resolvedTarget = isAbsolute(linkTarget)
				? linkTarget
				: resolve(dirname(fullPath), linkTarget);

			// Check if the resolved target would be within worktree
			// For dangling symlinks, we can't use realpath on the target,
			// so we check the literal resolved path
			const targetRelative = relative(worktreeReal, resolvedTarget);
			if (
				targetRelative === ".." ||
				targetRelative.startsWith(`..${sep}`) ||
				isAbsolute(targetRelative)
			) {
				throw new PathValidationError(
					"Dangling symlink points outside the worktree",
					"SYMLINK_ESCAPE",
				);
			}
			// Dangling symlink points within worktree - allow the operation
			return;
		}

		// Not a symlink but lstat succeeded - weird state, but validate parent chain
		await assertParentInWorktree(worktreePath, fullPath);
	} catch (error) {
		if (error instanceof PathValidationError) {
			throw error;
		}
		if (error instanceof Error && "code" in error && error.code === "ENOENT") {
			// Path truly doesn't exist (not even as a symlink) - validate parent chain
			await assertParentInWorktree(worktreePath, fullPath);
			return;
		}
		// Other errors - fail closed
		throw new PathValidationError("Cannot validate path", "SYMLINK_ESCAPE");
	}
}
export const secureFs = {
	/**
	 * Read a file within a worktree.