Cambridge Researcher Breaks OpenBSD Systrace

An anonymous reader writes "University of Cambridge researcher Robert Watson has published a paper at the First USENIX Workshop On Offensive Technology in which he describes serious vulnerabilities in OpenBSD's Systrace, Sudo, Sysjail, the TIS GSWTK framework, and CerbNG. The technique is also effective against many commercially available anti-virus systems. His slides include sample exploit code that bypasses access control, virtualization, and intrusion detection in under 20 lines of C code consisting solely of memcpy() and fork(). Sysjail has now withdrawn their software, recommending against any use, and NetBSD has disabled Systrace by default in their upcoming release."

Comments

SELinux and the same ...

[Gopal.V]

James Morris has put up an analysis of the same vulnerabilities.

And pushing the system code down into lower echelons of execution (i.e kernel), the way SELinux does it, is a valid fix.

No released version of sudo affected

[millert]

The sudo systrace support is part of an experimental feature ("monitor mode") not present in any of the real sudo releases (though the code is available via anonymous cvs). Given the deficiencies of systrace (and ptrace) it is unlikely that this feature will be present in any future sudo release.

  - todd

OpenBSD's man page for systrace mentions this?

[cgdae]

OpenBSD's systrace manpage appears to mention this problem in the BUGS section:

Applications that use clone()-like system calls to share the complete address space between processes may be able to replace system call arguments after they have been evaluated by systrace and escape policy enforcement.

Or see http://www.openbsd.org/cgi-bin/man.cgi?query=systr ace&apropos=0&sektion=0&manpath=OpenBSD+Current&ar ch=i386&format=html