Address #5

[tuck1s]

Accept multipart messages, fixing text/plain parts for compatibility with block crypto. encrypt() accepts string or message object type.

[balena]

Hey @tuck1s , nice work, but the code looks to solve a very particular case. Let me know if we can actually simplify the encrypt function a little bit, so all these filtering can be handled from outside the function. Do you agree?

[tuck1s]

Simpler is always better. A few comments -

• The existing code was doing a necessary thing by forming text/plain into Base64 (using the MIMEText call on the payload - which also removes non-needed headers), at least according to my reading of "RFC5751, section 3. Creating S/MIME Messages".
• I found that is definitely necessary if you have Content-Type: text/plain; charset=utf-8; format=flowed with long lines.
• Unfortunately, the existing code fails if you have anything except one text/plain MIME part
• I think it's necessary to walk the MIME parts and base64 encode any text/plain parts

I think my header removal code is rather ugly (please improve if you can), but in terms of inputs the intent is to make it more general rather than less general :-)

However I think you are right, we should move the "filtering" part outside of encrypt. Because I think the filtering should be done once only, before signing and/or encrypting. I'm trying to get some workable signing code together. So feel free to reject this PR (or even better .. suggest improvements to my code and also reject it)!

[tuck1s]

I'll withdraw this and submit a simpler version.