Re: [openpgp] Spoofing OpenPGP and S/MIME Signatures in Emails

[Marcus Brinkmann <[e-mail]>]

On 5/4/19 4:10 PM, Albrecht Dreß wrote:
> On 30.04.19 14:29, ilf wrote:
>> https://github.com/RUB-NDS/Johnny-You-Are-Fired
> 
> While testing the MUA Balsa <https://pawsa.fedorapeople.org/balsa/>
> using the proof-of-concept messages provided on Github, I noticed that
> many (most? all?) of the RFC 3156 message parts are not recognised by
> it.  Looking at the message source (e.g. “Attack Class 'MIME', Test 'M1'
> (PGP/MIME)”), it appears that the header
> 
>   Content-Type: multipart/signed; boundary="BOUNDARY";
> protocol="application/pgp-signature"
> 
> is missing the “micalg” parameter.  However, RFC 3156, sect.. 5 states that
> 
>> OpenPGP signed messages are denoted by the "multipart/signed" content
>> type, described in [RFC1847]
> 
> which defines in sect. 2.1
> 
>> Required parameters: boundary, protocol, and micalg
> 
> Consequently, Balsa (and maybe other MUA's, too) simply ignores such
> multipart/signed parts as they don't comply with the standard.
> 
> Did you omit the parameter intentionally, i.e. did I miss something
> interpreting the standards (typically, the value is never used), or are
> these proof-of-concept messages broken?

This is just because these are minimal test cases developed by hand.
Adding the parameter should be fine.

Thanks for your additional testing!  For everybody else: Albrecht posted
the test results on the balsa mailing list:
https://mail.gnome.org/archives/balsa-list/2019-May/msg00000.html

Thanks,
Marcus

-- 
Dipl.-Math. Marcus Brinkmann

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