The maintainers of the PHP programming language have issued an update regarding the security incident that came to light late last month, stating that the actors may have gotten hold of a user database containing their passwords to make unauthorized changes to the repository.
"We no longer believe the git.php.net server has been compromised. However, it is possible that the master.php.net user database leaked," Nikita Popov said in a message posted on its mailing list on April 6.
On March 28, unidentified actors used the names of Rasmus Lerdorf and Popov to push malicious commits to the "php-src" repository hosted on the git.php.net server that involved adding a backdoor to the PHP source code in an instance of a software supply chain attack.
While this was initially treated as a compromise of the git.php.net server, further investigation into the incident has revealed that the commits were a result of pushing them using HTTPS and password-based authentication, leading them to suspect a possible leak of the master.php.net user database.
The "git.php.net (intentionally) support[s] pushing changes not only via SSH (using the Gitolite infrastructure and public key cryptography), but also via HTTPS," Popov said. "The latter did not use Gitolite, and instead used git-http-backend behind Apache 2 Digest authentication against the master.php.net user database."
"It is notable that the attacker only makes a few guesses at usernames, and successfully authenticates once the correct username has been found. While we don't have any specific evidence for this, a possible explanation is that the user database of master.php.net has been leaked, although it is unclear why the attacker would need to guess usernames in that case."
Additionally, the master.php.net authentication system is said to be on a very old operating system and a version of PHP, raising the possibility that the attackers may have also exploited a vulnerability in the software to stage the attack.
As a consequence, the maintainers have migrated master.php.net to a new main.php.net system with support for TLS 1.2, in addition to resetting all existing passwords and storing passwords using bcrypt instead of a plain MD5 hash.