Missing input validation can lead to command execution in composer

Vulnerability Description

Composer is a dependency manager for the PHP programming language. Integrators using Composer code to call `VcsDriver::getFileContent` can have a code injection vulnerability if the user can control the `$file` or `$identifier` argument. This leads to a vulnerability on packagist.org for example where the composer.json's `readme` field can be used as a vector for injecting parameters into hg/Mercurial via the `$file` argument, or git via the `$identifier` argument if you allow arbitrary data there (Packagist does not, but maybe other integrators do). Composer itself should not be affected by the vulnerability as it does not call `getFileContent` with arbitrary data into `$file`/`$identifier`. To the best of our knowledge this was not abused, and the vulnerability has been patched on packagist.org and Private Packagist within a day of the vulnerability report.

References

• https://github.com/composer/composer/security/advisories/GHSA-x7cr-6qr6-2hh6
• https://github.com/composer/composer/commit/2c40c53637c5c7e43fff7c09d3d324d632734709
• https://www.tenable.com/security/tns-2022-09
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QD7JQWL6C4GVROO25DTXWYWM6BPOPPCG/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GWT6LDSRY7SFMTDZWJ4MS2ZBXHL7VQEF/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/625MT3IKWKFVIWLSYZFSXHVUA2LES7YQ/