Secrecy and user trust

[Patrick O'Callaghan]

On Thu, 2008-09-04 at 23:12 +0800, Ed Greshko wrote:
> Patrick O'Callaghan wrote:
> >
> >> NAK - if a fake public key were distributed then packages signed with 
> >> the fake key would be matched, allowing full access to install crap in 
> >> your machine.
> >>     
> >
> > True.
> >   
> Actually I don't understand the paragraph above.  It seems to be saying
> that packages would be signed with a public key which can't be done. 
> So, the person making that statement needs to clarify.

Which is the point I made earlier.
  
> >> And packages signed with any valid redhat key would be 
> >> rejected.
> >>     
> >
> > Which is what I said. Thus it would be noticed immediately.
> >   
> No, they would not be rejected as long as you still have Red Hat's
> public key installed on your system.  You can determine what public keys
> are on your system by "rpm -qa gpg-pubkey*". 
> 
> When an rpm is signed it is signed with a private key and information
> about the corresponding public key is placed in the rpm file.  That
> information is used to retrieve the correct public key for
> verification.  So, as long as you've not deleted it, they will verify.

The hypothetical scenario being discussed is that you have already
replaced the former (good but now possibly suspect) public key with a
spurious new one. If that were to happen, you would be in danger of
accepting trojanned packages signed with this new fake key. My point is
that you would also *reject* packages signed with the new good key, and
this would be noticed very quickly (basically the next time you did an
update).

poc