Vigil@nce: vixie-cron, changing timestamp
February 2010 by Vigil@nce
A local attacker can use vixie-cron to reset a file modification time.
Consequences: data creation/edition
Provenance: user shell
Means of attack: 1 attack
Ability of attacker: technician (2/4)
Confidence: confirmed by the editor (5/5)
Diffusion of the vulnerable configuration: high (3/3)
Creation date: 24/02/2010
Unix - plateform
DESCRIPTION OF THE VULNERABILITY
The utime() function changes the time of a file:
actime : time of the last access
modtime : time of the last modification
When a user edits its crontab via "crontab -e", vixie-cron creates a temporary file in /tmp, and uses utime() to reset its access and modification times (in order to easily detect that the file was changed). However, these changes are done with root privileges.
A local attacker can therefore edit his crontab, and create a symbolic link, in order to force vixie-cron to change times of a file.
Identifiers: CVE-2010-0424, FEDORA-2010-2751, VIGILANCE-VUL-9473