Date: Wed, 26 Nov 2014 16:25:25 +0100 From: Sebastian Krahmer <krahmer@...e.de> To: oss-security@...ts.openwall.com Subject: blkid command injection Hi There is a command injection inside blkid. It uses caching files (/dev/.blkid.tab or /run/blkid/blkid.tab) to store info about the UUID, LABEL etc it finds on certain devices. However, it does not strip " character, so it can be confused to build variable names containing embedded shell metas, which it would usually encode inside the value. Given an USB stick with /dev/sdb1 you can: # mkfs.ext4 -L 'X"`/tmp/foo` "' /dev/sdb1 # blkid -o udev /dev/sdb1 ID_FS_LABEL=X__/tmp/foo___ [...] Seems to be OK, but invoking blkid a second time, taking the cache in effect: # blkid -o udev /dev/sdb1 ID_FS_LABEL=X ID_FS_LABEL_ENC=X ID_FS_`/tmp/foo` "" UUID=... [...] "blkid -o udev" is often used in root context via udev or in automounters (uam-pmount) to construct key=value environment variables inside shell scripts which are then evaluated. Might be possible to construct an embedded LD_PRELOAD= as well for the binary case. By injecting > character one can probably construct whole fake cache entries. Sebastian -- ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@...e.de - SuSE Security Team
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.