Re: [gmime-devel] [PATCH 6/6] Support extraction of session keys during decryption.

[Jeffrey Stedfast <fejj gnome org>]

On 12/2/2016 7:48 PM, Daniel Kahn Gillmor wrote:
> On Fri 2016-12-02 18:52:04 -0500, Jeffrey Stedfast wrote:
> > On 12/2/2016 3:31 PM, Daniel Kahn Gillmor wrote:
> > > (and hm, actually, maybe that means we should be zeroing the RAM before
> > > releasing the stored session key; i can make that change if that sounds
> > > good to you)
> > Yes, please :)
> thanks for scrubbing the ram already :)
>
> > > the other advantage for keeping this command is that it makes it clearer
> > > in the API which cryptocontexts are capable of this kind of operation.
> > > Would it be better to make this function part of the GMimeCryptoContext
> > > API instead of the GMimeGpgContext, though?
> > If the plan is to also add it to the S/MIME context, then yes.
> I have no idea whether it makes sense to add it to the S/MIME context --
> it might, but i haven't tried.  i don't think S/MIME can do decryption
> anyway yet, can it?
>
> > > What API would you prefer for a "try-this-session-key" approach?  I see
> > > two mechanisms:
> > >
> > > (a) give the session key to the context for any number of subsequent
> > >       decryptions until it is cleared or re-set:
> > >
> > >           g_mime_gpg_context_set_session_key_for_decryption()
> > >           g_mime_gpg_context_clear_session_key_for_decryption()
> > >
> > >       This is a bit awkward, though: what should happen if the wrong
> > >       session key is given; should it fall back to trying to use the
> > >       available public keys?  if so, then we'd need to do some fancy
> > >       footwork, because gpg simply fails to decrypt if you give it the
> > >       wrong session key.
> > >
> > >
> > > (b) have some variation on g_mime_multipart_encrypted_decrypt() or
> > >       g_mime_crypto_context_decrypt(), which has an additional parameter
> > >       of "session_key".
> > (b) makes the most sense.
> >
> > Perhaps g_mime_crypto_context_decrypt_session?
> and a g_mime_multipart_encrypted_decrypt_session() as well?
>
> I can work on this patch if it's something that you'd like.
>
>        --dkg


I am not in a rush to have it since at this moment, you are the only one 
using the session_key at all and you don't seem to need it in any sort 
of immediate timeframe.


I was more just curious.


Feel free to implement as time and/or desire permits.


Jeff