Updates released by Retrospect, Inc. for its cross-platform backup and recovery software address numerous bugs, including a password hashing weakness that puts users’ files at risk.
Retrospect backup clients are designed to store hashed versions of user passwords. However, researchers discovered a bug in the hash generating algorithm that makes it easy for an attacker to brute-force the password and gain access to the victim’s backup files.
“The password is not fully utilized when generating a hash, allowing the possibility of a weak hash with a higher probability of collision with other passwords,” the CERT Coordination Center at Carnegie Mellon University wrote in an advisory. “Attackers with network access to a machine running the Retrospect client may be able to generate brute-force passwords that are guaranteed to collide with the hashed password with a maximum of 128 tries.”
Retrospect has pointed out that the security hole can be exploited by “a sophisticated individual with a significant amount of technical expertise and network access.”
The vulnerability (CVE-2015-2864) only affects customers who use clients with password protection. Customers using clients with public/private key authentication are not impacted. All versions of the product are affected, including Retrospect 8 for Mac and Retrospect 7 for Windows.
The flaw was publicly disclosed by Josep Pi Rodriguez and Pedro Guillen Nunez at the Hack in Paris conference in June 2014. Retrospect was notified of the existence of the bug in late April 2015.
The vulnerability was addressed by Retrospect on June 9 with the release of version 10.0.2.119 for Windows, version 10.0.2.104 for Linux, and version 12.0.2.116 for Mac. Users can resolve the issue either by updating the Retrospect engine and clients, or by switching to public key authentication.
Retrospect has published an advisory containing instructions on how to update the backup software and how to switch to keypairs.