In Ruby password checking library discovered a backdoor

Developer Tute Costa found a backdoor in the Ruby library “strong_password”, with which attackers could execute any code in applications containing this library.

As Costa found out, malicious code checked in which environment the library is located – in test or production. If in production, the code downloaded from Pastebin an additional malicious module that serves as a backdoor in applications or on web sites that use the strong_password library.

“In a loop within a new thread, after waiting for a random number of seconds up to about an hour, it fetches and runs the code stored in a pastebin.com, only if running in production, with an empty exception handling that ignores any error it may raise”, — reported Tute Costa.

Having discovered the problem, Costa made an attempt to contact the real owner of the library, but it turned out that the developer’s RubyGems account was intercepted by an intruder. In this account, the hacker posted a malicious version of “strong_password” 0.0.7, containing a backdoor. According to RubyGems statistics, the malicious version was downloaded 537 times.

Costa told the owner of the library and the RubyGems security service about the find. The malicious version was removed from the repository within a week after the download.

A similar incident happened in April of this year, when a hacker crashed into the Bootstrap-Sass Ruby library with an almost identical backdoor deployment mechanism.