On Fri, Apr 9, 2010 at 8:00 PM, Junhao <[email protected]> wrote:

> On 04/09/2010 10:11 AM, Michael Clark wrote:
>


> If the systems had prelinking (popular in fedora a few years ago), all
>>
>> of the the shared objects get rewritten with non-conflicting link
>> addresses (to avoid runtime relocation overhead). It is usually set up
>> in /etc/cron (check cron.daily, cron.weekly, etc)
>>
>> I'm not sure if more recent linux systems use prelinking or not - it may
>> conflict with link address randomisation (a security mechanism, so that
>> exploits can't run code that targets known address offsets). e.g. look
>> at the link addresses of /bin/ls over two runs (on Debian Sid/2.6.32):
>>
>> mcl...@monty:~$ ldd /bin/ls
>> libselinux.so.1 => /lib/libselinux.so.1 (0xb777f000)
>> librt.so.1 => /lib/i686/cmov/librt.so.1 (0xb7776000)
>
>
> Ahh.... That might explain it. Will check when I get back to office next
> week. FYI, we are testing on Redhat Enterprise Linux 5.x.


That's interesting.  With such a mechanism in place, how would one verify
the integrity of the files?  Eg, rpm -V and tripwire would both fail now.
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