Messages in this thread | | | Date | Mon, 22 Apr 2002 12:18:19 -0700 | From | Chris Wright <> | Subject | Re: [SECURITY] FDs 0, 1, 2 for SUID/SGID programs |
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* Florian Weimer (Weimer@CERT.Uni-Stuttgart.DE) wrote: > http://www.pine.nl/advisories/pine-cert-20020401.html probably affects > Linux, too (if a SUID/SGID program is invoked with FD 2 closed, error > messages might be written to a file opened by the program ).
AFAIK, the standards clearly specify behaviour wrt. open file descriptors and clone-on-exec file descriptors across execve(). However, there is nothing specified when it comes to closed file descpriptors across execve(), notably FD's 0, 1 and 2 are certainly not required to be open across an execve() of a SUID/SGID applictaion. One could argue that SUID/SGID apps that trust the file descriptors they inherit across exec() are buggy.
Having said that, there are a number of implementations of this type of protection for the linux kernel stemming from the Openwall project. If you are interested, see:
http://www.openwall.com (CONFIG_SECURE_FD_0_1_2) http://lsm.immunix.org (CONFIG_OWLSM_FD) http://grsecurity.net (CONFIG_GRKERNSEC_FD)
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