Composer arbitrary command execution via a malicious package's Perforce source URL

Summary

If the p4 Perforce CLI client is installed, a malicious dependency package from a package repository allowing arbitrary perforce source URLs (packagist.org is safe) could execute arbitrary commands when running composer install or composer update. Composer passed a package's Perforce source address to the p4 CLI client without validating it. The p4 CLI client accepts addresses that mean "run this local command" instead of "connect to this server". This is remote code execution with the privileges of the user or CI account running Composer.

Am I affected?

You are only affected if all of the following are true:

• The Perforce p4 command line client is installed and on the PATH of the machine running Composer.
• An attacker can control a package metadata's source section with a perforce type. Packagist.org does not allow perforce source metadata, so you are only exploitable if you rely on another Composer repository (any custom composer-type repository, or an inline package repository entry), or a composer.lock file you obtained from somewhere you do not trust.
• The package gets installed from source, either because it has no dist artifact or because source installs are selected (for example --prefer-source).

Plainly not affected: anyone without the p4 client installed, which is the large majority of Composer users. Perforce is an optional VCS integration. Also not affected: projects that only consume packages from Packagist.org, which does not allow Perforce source repositories and therefore cannot serve a package with a Perforce source address.

Most realistic way to get hit: a developer workstation or CI image that has Perforce tooling installed, pulling packages from a private or third party Composer repository that an attacker has compromised.

Patched versions

Composer now validates Perforce source addresses before handing them to the p4 client, and accepts only real network endpoints (an optional tcp/ssl transport with a host and port). Addresses that make the client spawn a local process are rejected, and the package fails validation on both update and install, before any p4 command runs. Fixed in Composer 2.10.3 and 2.2.30.

Note: If you legitimately use Perforce with an unusual P4PORT value that is not a plain host and port, Composer will now reject it.

Workarounds

Upgrading is the only complete fix.

Risk reduction short of upgrading:

• Remove the p4 client from the PATH of machines that run Composer but do not use Perforce. This fully blocks this specific attack, since the vulnerability depends on that client being present.
• Restrict configured repositories to sources you control or trust, and treat lock files from untrusted sources as untrusted input.