Description

pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, when updating a one-time pad file, a temporary file is created using open() without the O_EXCL flag. Without O_EXCL, the create operation is not atomic: two concurrent processes racing to update the same pad may both succeed in opening the file, with the second write silently overwriting the first. The one-time pad is the core replay-prevention mechanism of pam_usb. A successful race could result in the stored pad value diverging from what either process expected, potentially causing authentication failures or, in a precisely timed attack, creating a window for pad reuse. This issue has been fixed in version 0.9.2.

Weaknesses 1

References 2

• github.com https://github.com/mcdope/pam_usb/releases/tag/0.9.2
• github.com https://github.com/mcdope/pam_usb/security/advisories/GHSA-hxh6-9574-5vp6

Remediation