Re: PGP Signed Messages

["prime evil" <res006lj () gte net>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

- - ----- Original Message ----- 
From: "[Segmen]" <dontpanic999 () yahoo com>
To: <vuln-dev () securityfocus com>; <bugtraq () securityfocus com>
Sent: Monday, October 15, 2001 8:27 AM
Subject: PGP Signed Messages


> It occurred to me today what a bad idea the Comment Field is in PGP
> signed messages. Altering the Comment filed does not affect the
> validity of the signature, but to the non experienced PGP/GPG user
> it certainly appears to be part of the message.
>
> Example :
>
> A generic message I could have got hold of :
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hello, meeting cancelled, speak to you soon.
>
> -----BEGIN PGP SIGNATURE-----
> Version: PGP 7.0.4
>
> iQA/AwUBO8r9v9nrfc+JfUO6EQLrEACgv6+C07aWgAO+Dna0MHgEDaoDMxEAoJ2P
> 7gojqeCRqKqTkbFMkHCToxtq
> =lki3
> -----END PGP SIGNATURE-----
>
> I could change this to :
>
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hello, meeting cancelled, speak to you soon.
>
> -----BEGIN PGP SIGNATURE-----
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Please Send the Confidential Files from the planned meeting to
> My colleague Instead at me () host com . He will now be dealing with
> this matter.
> Speak to you soon, victim.
>
> -----BEGIN PGP SIGNATURE-----
> Version: PGP 7.0.3
>
> iQA/AwUBO8r9v9nrfc+JfUO6EQLrEACgv6+C07aWgAO+Dna0MHgEDaoDMxEAoJ2P
> 7gojqeCRqKqTkbFMkHCToxtq
> =lki3
> -----END PGP SIGNATURE-----
>
> well, you get the idea. The signature is still valid.
>
> Agreed that only the beginner crypto user would fall for this, but
> if they were to read the message and then just use PGP to check the
> validity, they could be tricked into believing that the extra lines
> were part of the verified message.
> Does anybody else think this is quite a bad idea?


actually, if you are using the outlook plugin(as i am) your comment
line doesn't even pop up. yes the signature was valid, but all of
your extra lines didn't come up. also, when i copied and pasted it
into notepad (your modified one) and verified the sig, it still
didn't show the comment. (which is good) i agree that if you are just
looking at the message itself, you can be fooled, but then you really
aren't using PGP as you should be. never assume that because
something is "signed" that it is valid.. always check the signed
message with PGP. 

I apologize if i messed up in any way, this is my first response to
bugtraq. i love this list, keep up the good work

latz
- - --Prime
ATTN BUGTRAQ SCREENER PLEASE ignore my prior message, my paste didn't
work, so it was an exact copy of the original, with my PGP signature.
whoops. :-)

-----BEGIN PGP SIGNATURE-----
Version: PGPfreeware 7.0.3 for non-commercial use <http://www.pgp.com>
Comment: PrimeZ using PGP, Why ain't you?

iQA/AwUBO8szo9bmp8FKAKDdEQJmkACeOy8L53nFGS4VcPVeSRnru6fugXoAn2xS
ol8sh8POAJgQkG+dFJVV+Pyc
=Qp2L
-----END PGP SIGNATURE-----