Re: [ANNOUNCE] Release Digsig 1.5: kernel module for run-timeauthentication of binaries

[Nix <nix@esperi.org.uk>]

On 24 Apr 2006, Arjan van de Ven announced authoritatively:
> On Mon, 2006-04-24 at 12:27 -0400, Makan Pourzandi (QB/EMC) wrote:
>> Hi Arjan, 
>> 
>> I hope I correctly understood your question, DigSig uses LSM hooks to
>> check the digital signature before loading it, then as long as your elf
>> loader uses kernel system calls, it's covered by DigSig. 
> 
> ok I have to admit that this answer worries me.
> 
> how can it be covered? How do you distinguish an elf loader application
> (which just uses open + mmap after all) with... say a grep-calling perl
> script?

It checks mmap and mprotect with PROT_EXEC, and execve().

> As long as you allow apps to mmap (or even just read() a file into
> memory).... they can start acting like an elf loader if they chose to do
> so. And.. remember it's not the files WITH signature you're protecting
> against (which you could check) but the ones WITHOUT. And there are many
> of those; and you can't sign ALL files I think, not without going
> through really great hoops anyway.

Why not? It's one command with bsign:

bsign -s -I -i / -e /proc

will sign every ELF shared object and executable on the system.

-- 
`On a scale of 1-10, X's "brokenness rating" is 1.1, but that's only
 because bringing Windows into the picture rescaled "brokenness" by
 a factor of 10.' --- Peter da Silva