Re: [GIT PULL] Load keys from signed PE binaries

Jiri Kosina
2013-02-28T23:02:49Z

On Thu, 28 Feb 2013, Matthew Garrett wrote:

> > Let me formulate my point more clearly -- Microsoft very likely going to
> > sign hello world EFI PE binary, no matter the contents of .keylist
> > section, as they don't give a damn about this section, as it has zero
> > semantic value to them, right?
> >
> > They sign the binary. By signing the binary, they are *NOT* establishing
> > cryptographic chain of trust to the key stored in .keylist, but your
> > patchset seems to imply so.
>
> Mr Evil Blackhat's binary is then a mechanism for circumventing the
> Windows trust mechanism,

Yes, the "hello world" one.

But the real harm is being done by the i_own_your_ring0.ko module, which
can be modprobed on all the systems where the signed "hello world" binary
has been keyctl-ed before it was blacklisted.

In other words -- you blacklist the population of the key on systems by
blakclisting the key-carrying binary, but the key remains trusted on
whatever system the binary has been processed by keyctl before. Right?

If so, that's a clear difference from normal X.509 chain of trust (i.e.
the difference between having the key signed, and having the binary
signed).

--
Jiri Kosina
SUSE Labs