Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Wed, 17 Apr 2013 14:32:36 -0400
From: Daniel Kahn Gillmor <>
CC: Kurt Seifried <>, Thomas Biege <>
Subject: Re: debian: gpg --verify suggests entire file was
 verified, even if file contains auxiliary data

On 04/17/2013 02:23 PM, Kurt Seifried wrote:
> I've run into this before, sadly enigmail (Thunderbird gpg plugin)
> displays the same green bar for message signed ok, but displays the
> text as "Part of the message signed" so unless you're really paying
> attention, you'll miss it.
> My thinking is this:
> 1) It's pretty easy to find signed content for people using GPG
> 2) It's pretty easy to append/embed signed content into a larger message
> So the attack would be: create malicious content/email, embed/append a
> valid message harvested from somewhere. Send to user. The user
> verifies then reads the message, unless they are really paying
> attention they probably won't notice that the content isn't signed
> properly (e.g. have an email, ton of whitespace, then the signed
> message). Personally I'm inclined to assign a CVE, enigmail for
> example does mostly the right thing (makes a distinction between fully
> signed and partially signed). I think GPG should too.
> Thoughts/comments before I assign this?

A similar attack (related to PGP/MIME) has been under discussion on the
enigmail list last month.  see the thread starting at:

I think the enigmail issues are distinct from the gpg issues, and i
don't think they should be conflated into the same CVE.

In particular, i see the enigmail issues as (security-related) UI/UX
problems, but i see the gpg problems as (security-related)
API/programmatic-use problems.

By comparison with enigmail, thunderbird's native S/MIME verification
routines display no cryptographic indicators at all if only part of a
message is signed.  This means that S/MIME-signed messages sent through
common mailing list software which attaches a text/plain MIME footer
(like mailman) will not indicate that they are verifiable at all.

it's not a pretty set of tradeoffs. :/


Download attachment "signature.asc" of type "application/pgp-signature" (1028 bytes)

Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.