[36072] in bugtraq
Re: Windows doesn't verify digital signature of CRL files
daemon@ATHENA.MIT.EDU (Thomas Walpuski)
Tue Aug 10 20:03:18 2004
Date: Tue, 10 Aug 2004 18:40:15 +0000
From: Thomas Walpuski <thomas-bugtraq@unproved.org>
To: Neil Gierman <ngierman@roadrunn.com>
Cc: Faro Poplar <faropoplar@yahoo.com>, bugtraq@securityfocus.com
Message-ID: <20040810184015.GA8029@unproved.org>
Mail-Followup-To: Neil Gierman <ngierman@roadrunn.com>,
Faro Poplar <faropoplar@yahoo.com>, bugtraq@securityfocus.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1479.192.138.31.191.1092154067.squirrel@192.138.31.191>
* Neil Gierman wrote:
> If a person was able to inject a modified CRL into
> that CDP URL, or redirect the client machine to an alternate server for
> LDAP/HTTP CRL download, and CAPI is not validating signatures on CRL's
> then a person could use a revoked certificate for access to systems among
> other things.
You have to distinguish between CRL retrieval (which is not really
critical) and using a CRL in the process of verifying an certificate
chain.
All parts of Microsoft's CryptoAPI use CertGetCRLFromStore with
CERT_STORE_SIGNATURE_FLAG, i.e. improperly signed CRLs won't be used in
the verification process.
So unless you're using Microsoft's CryptoAPI at a low level and you
don't know what you're doing there is no issue.
Thomas Walpuski
