Re: Disturbing news..

[Ben Ford]

Simon Williams wrote:

> In message <[e-mail]>, Olivier Galibert
> <[e-mail]> writes
> 
>> On Wed, Mar 28, 2001 at 03:04:46PM +0100, Simon Williams wrote:
>> 
>>> I think their point was that a program could only change permissions
>>> of a file that was owned by the same owner.  If a file is owned by a
>>> different user & has no write permissions for any user, the program
>>> can't modify the file or it's permissions.
>> 
>> You mean, you usually have write permissions for other than the owner
>> on executable files?
>> 
>> Let me reformulate that.  You usually have write permissions for other
>> than the owner, and not only on some special, untrusted log files (I'm
>> talking files, here, not device nodes)?  What's your umask, 0?
>> 
> 
> Firstly, I'm relatively new to Linux (only about 3 yrs experience) &
> don't claim to be an expert.  Secondly, I don't think I stated my point
> very clearly.
> 
> No, I don't have write permissions set on an executable for any user
> other than the owner.
> 
> What I meant was that if a file is owned by root with permissions of,
> say, 555 (r-xr-xr-x), not setuid or setgid, then another executable
> run as a non-root user cannot modify it or change the permissions to
> 7 (rwx).

There are two problems I see here.  First, there are several known ways 
to elevate privileges.  If a virus can elevate privileges, then it owns 
you.  Second, this is a multi-OS virus.  If you dual-boot into Windows,  
any ELF files accessible can be infected.  With this one, that isn't a 
prob, but when somebody codes in an ext2 driver to their virus, then 
we've got issues.

-b