oath-toolkit: privilege escalation in pam_oath.so (SUSE Security Team Blog)

The SUSE Security Team Blog has a detailed report on its discovery of a privilege escalation in the oath-toolkit, which provides libraries and utilities for managing one-time password (OTP) authentication.

Fellow SUSE engineer Fabian Vogt approached our Security Team about the project's PAM module. A couple of years ago, the module gained a feature which allows to place the OTP state file (called usersfile) in the home directory of the to-be-authenticated user. Fabian noticed that the PAM module performs unsafe file operations in users' home directories. Since PAM stacks typically run as root, this can easily cause security issues.