Date: Tue, 7 Sep 2010 10:35:46 +0200 From: Sebastian Krahmer <krahmer@...e.de> To: oss-security@...ts.openwall.com Cc: security@...nel.org, spender@...ecurity.net Subject: /proc infoleaks I have been elected to receive the bashing from all sides, so here we go. It is not about a new vulnerability or even a new discussion but needs to be discussed, at least that we have a clear statement about the status quo. Recent i-CAN-haz-MODHARDEN.c has shown once *again* that certain file permissions make no sense except to exploitation development. There is no reason to have files like /proc/kallsyms /proc/slabinfo /proc/zoneinfo and probably a lot of others world readable. The symbol addresses might be hard-coded for a certain targetlist inside the exploit so you can argue that there wont be any protection benefit from making it unreadable. However this argument aint a reason to also leak it for self-compiled kernels and doesnt even hold for dynamic/runtime content like slabinfos etc. It would be nice to have something like echo 1 > /proc/quiet or something like a umask for kernel-owned proc entries so that you have a polite default and are still able to enable it for certain profiling tools or whereever you need it. I know that hardening patches already have these secure defaults; with reason. Making kernel exploits has been really too easy in past if you get all the mem layout and symbols for free. Of course that doesnt free one from writing good code but its about time (since years actually) to raise the level. regards, Sebastian -- ~ ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@...e.de - SuSE Security Team ~ SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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