x/crypto/openpgp: Encrypt writes signature at the end

[emersion]

openpgp.Encrypt writes the signature packet after the encrypted key and the symmetrically encrypted packet. According to the RFC, an OpenPGP signed message is either a signature packet followed by a message or a one-pass signed message (https://tools.ietf.org/html/rfc4880#section-11.3).

Thus, this implementation is violating the RFC by writing the message followed by the signature (no one-pass). To fix it, a one-pass signature packet (https://tools.ietf.org/html/rfc4880#section-5.4) should be written before the encrypted message.

[emersion]

My bad, the one-pass signature packet is correctly written.