security/smaSHeM 0.4 NetBSD

System V shared memory segments created with shmget() are assigned an owner, a group and a set of permissions intended to limit access to the segment to designated processes only. The owner of a shared memory segment can change the ownership and permissions on a segment after its creation using shmctl(). Any subsequent processes that wish to attach to the segment can only do so if they have the appropriate permissions. Once attached, the process can read or write to the segment, as per the permissions that were set when the segment was created.

smaSHeM takes advantage of applications that set weak permissions on such segments, allowing an attacker to dump or patch their contents. As discussed in the presentation at 44CON 2013 entitled 'I Miss LSD', in the case of many X11 applications it is possible to extract pixmaps of previously rendered GUI artifacts. When compiled with QtCore linking enabled, smaSHeM aids in that process by brute forcing potentially valid dimensions for the raw pixmap dump.