Re: #100409 GnuPG printf format string vulnerability

[Florian Weimer <Florian.Weimer@RUS.Uni-Stuttgart.DE>]

Wichert Akkerman <wichert@wiggy.net> writes:

> Previously Florian Weimer wrote:
> > With GnuPG 1.0.4, the web of trust can be compromised by an attacker,
> 
> How?

GnuPG 1.0.4 automatically assigns ultimate trust to public keys if a
corresponding private key is present in the private key ring.  When a
key ring is imported, public keys are added to the public key ring,
and private keys to the private key ring, without any confirmation by
the user.  Usually, key rings are distributed over an insecure
channel, and we have to assume an attacker can inject suitably chosen
private keys, public keys, and key signatures.  When the victim
imports a tampered key ring, he also imports ultimately trusted keys
without any warning.  The ultimately trusted key can sign any other
key and raise the computed trust to the maximum, thus the victim's web
of trust is compromised.

Starting with 1.0.5, GnuPG no longer automatically imports private
keys.

I first thought that this problem is pretty academic, but when you
think of it, it's quite scary, because it affects the core of GnuPG,
the web of trust.

> > and there's a pretty severe problem with detached signature
> > verification. 
> 
> That was fixed months ago, check the changelog.

Sorry.

-- 
Florian Weimer 	                  Florian.Weimer@RUS.Uni-Stuttgart.DE
University of Stuttgart           http://cert.uni-stuttgart.de/
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