gpg: Implement AEAD for SKESK packets.
* g10/packet.h (PKT_symkey_enc): Add field aead_algo. * g10/build-packet.c (do_symkey_enc): Support version 5 packets. * g10/parse-packet.c (parse_symkeyenc): Ditto. * g10/encrypt.c (encrypt_symmetric): Force using a random session key in AEAD mode. (encrypt_seskey): Add and support arg aead_algo. (write_symkey_enc): Ditto. (encrypt_simple): Adjust accordingly. (encrypt_filter): Ditto. * g10/gpgcompose.c (sk_esk): For now call encrypt_seskey without AEAD support. * g10/mainproc.c (symkey_decrypt_seskey): Support AEAD. Nver call BUG but return an error. (proc_symkey_enc): Call symkey_decrypt_seskey in a bug compatible way. * g10/import.c (check_prefs): Check AEAD preferences. * g10/keyedit.c (show_prefs): Print AEAD preferences.
For easier debugging this patch also changes some diagnostics to also
print the encryption mode with the cipher algorithm.
- Signed-off-by: Werner Koch <wk@gnupg.org>