1"""Mail handling
3@copyright: 2022 Ansgar <ansgar@debian.org>
4@license: GNU General Public License version 2 or later
5"""
7import daklib.gpg
9import email
10import email.message
11import email.policy
13from typing import cast
16def sign_mail(msg: email.message.EmailMessage, *, digest_algorithm: str = "SHA256", **kwargs) -> email.message.EmailMessage:
17 """sign an email message using GnuPG.
19 This only handles non-multipart messages.
20 """
21 mime_data = email.message.MIMEPart()
22 mime_data.set_content(msg.get_payload())
23 # Copy Content-Transfer-Encoding from unsigned message
24 del mime_data["Content-Transfer-Encoding"]
25 mime_data["Content-Transfer-Encoding"] = msg["Content-Transfer-Encoding"]
26 data = mime_data.as_bytes(policy=email.policy.SMTP)
28 sig = daklib.gpg.sign(data, **kwargs, digest_algorithm=digest_algorithm)
29 mime_sig = email.message.MIMEPart()
30 mime_sig['Content-Type'] = 'application/pgp-signature'
31 mime_sig.set_payload(sig)
33 msg.clear_content()
34 del msg['Content-Type']
35 msg['Content-Type'] = f'multipart/signed; micalg="pgp-{digest_algorithm.lower()}"; protocol="application/pgp-signature"'
36 msg.set_payload([mime_data, mime_sig])
37 return msg
40# TODO [python3.10, pep604]:
41# def parse_mail(msg: bytes | str) -> email.message.EmailMessage:
42def parse_mail(msg) -> email.message.EmailMessage:
43 if isinstance(msg, str): 43 ↛ 48line 43 didn't jump to line 48, because the condition on line 43 was never false
44 # We need a cast as the return type depends on the `policy` argument.
45 return cast(email.message.EmailMessage, email.message_from_string(msg, policy=email.policy.SMTPUTF8))
46 else:
47 # We need a cast as the return type depends on the `policy` argument.
48 return cast(email.message.EmailMessage, email.message_from_bytes(msg, policy=email.policy.SMTPUTF8))