Solaris ufsrestore Buffer Overflow Vulnerability

Solaris is a version of the UNIX Operating System distributed by Sun Microsystems.

Solaris ships with a filesystem utility called ufsrestore that is used for archive/backup retrieval. A problem with the utility could allow a local user to gain elevated privileges.

The ufsrestore utility is setuid root by default, and vulnerable to a buffer overflow attack. The problem is an oversight in code that was put in place to try and correct/prevent this very type of vulnerability. In a function in ufsrestore, two strncat calls (libc functions that are used to concatenate two NULL terminated arrays) are used to construct a string. The programmer made an effort to prevent a buffer overflow by using the strncat functions, which allow you to specify a maximum byte length. The error is that an incorrect number of bytes are passed to the strncat calls as length. The number of bytes (the maximum that the function should copy) that are passed to the strncats are the size of the entire buffer (the one being constructed), meaning it is possible to overflow it via strncat.

This problem makes it possible for a local user execute arbitrary code, and gain root priviliges.


 

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