Re: [openpgp] Encryption and signature context parameter (Was: OpenPGP encryption block modes)

[Ángel <[e-mail]>]

On 2022-08-18 at 01:12 +0200, Marcus Brinkmann wrote:
> Yes, and we limited our investigation to email encryption only
> because that was a nicely scoped academic research task. Even just
> adding some mime type, file ending, or any other meaningful label as
> context parameter would be useful to disable potential attacks that
> exploit context confusion across different application domains (for
> example stuffing email ciphertexts into OpenOffice documents should
> they support public key document encryption in the future).

For the record, it is already possible to encrypt OpenOffice documents
(i.e. OpenDocument) using OpenPGP keys, in what might be a LibreOffice
extension: 
https://conference.libreoffice.org/assets/Conference/Rome/Slides/libocon2017gpg4libre.pdf


It seems like a "normal" password-encrypted document where the key is
available through OpenPGP.

META-INF/manifest.xml looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<manifest:manifest xmlns:manifest="urn:oasis:names:tc:opendocument:xmlns:manifest:1.0" manifest:version="1.2" xmlns:loext="ur
n:org:documentfoundation:names:experimental:office:xmlns:loext:1.0">
 <loext:keyinfo>
  <loext:encrypted-key>
   <loext:encryption-method loext:PGPAlgorithm="
http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p"/>
   <loext:KeyInfo>
    <loext:PGPData>
     <loext:PGPKeyID>{base64 of ASCII fingerprint of the main key}</loext:PGPKeyID>
     <loext:PGPKeyPacket>{base64 of ASCII fingerprint of the main key}</loext:PGPKeyPacket>
    </loext:PGPData>
   </loext:KeyInfo>
   <loext:CipherData>
    <loext:CipherValue>{OpenPGP encryypted data}</loext:CipherValue>
   </loext:CipherData>
  </loext:encrypted-key>
 </loext:keyinfo>
 <manifest:file-entry manifest:full-path="/" manifest:version="1.2" manifest:media-type="application/vnd.oasis.opendocument.t
ext"/>
 <manifest:file-entry manifest:full-path="styles.xml" manifest:media-type="text/xml" manifest:size="12337">
  <manifest:encryption-data manifest:checksum-
type="urn:oasis:names:tc:opendocument:xmlns:manifest:1.0#sha256-1k"
manifest:ch
ecksum="4AfV2B3IFXUKhnXhd8dH3xD1kyrxL1nHKmHLVyTwKYQ=">
   <manifest:algorithm manifest:algorithm-name="
http://www.w3.org/2001/04/xmlenc#aes256-cbc" manifest:initialisation-
vector="{base64 of IV}"/>
   <manifest:key-derivation manifest:key-derivation-name="PGP"/>
  </manifest:encryption-data>
 </manifest:file-entry>
 <manifest:file-entry manifest:full-path="settings.xml" manifest:media-
type="text/xml" manifest:size="12055">
 ...
 </manifest:file-entry>
</manifest:manifest>

Regards