Messages in this thread | | | Date | Mon, 21 Aug 2000 20:00:25 +0200 | From | Julien Oster <> | Subject | Re: When to submit something? and: signed executables. |
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On Mon, Aug 21, 2000 at 11:39:59AM -0600, Charles Cazabon wrote:
Hello Charles,
I submit this to the list since I think it's something that might be of interest for others.
> Just out of curiosity, what happens if...
> 1. Hacker gets in through sendmail whole or such and gets a root shell. > 2. Hacker pokes through /proc/kcore and changes the md5sums stored. > 3. Now no one (including root?) can run any setuid programs, or possibly > any binaries at all, until the system is restarted or they undo the damage > in /proc/kcore.
The hacker, obviously being root, could also write a module that tries to disable the whole MD5 checking thing. He could also mess up everything by dumping crap to /proc/kcore, without the MD5 thingie.
He could also remove the insmod for the module from the startup scripts, provocate a reboot...
If one's already root, the system is overtaken. There's always a way if you are root.
I even would say that if a hacker got root privileges, there's no more need to replace any binaries. (except for building "entry insurances")
But if he has no complete root shell, and there is a way to somehow change a binary, put in a trojan horse (how many times a day is an administrator typing "ls" as root?)... well, that's bad. And the signed exec module (it's called "signed exec" since I later plan to implement some public/private key mechanism) prevents this.
It does not prevent an idiot system administrator from doing idiot things which break security, but maybe it has some advantages.
I believe that security is mostly a conceptual thing, built up by a good admin with a good network structure. But if we can make a operating system a little bit more secure, make hacking just a little bit more harder - why shouldn't we do so?
Just my 2 cents, Julien
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