sm: Support AES-GCM decryption.
* sm/gpgsm.c (main): Use gpgrt_fcancel on decryption error if gpgrt supports this. * sm/decrypt.c (decrypt_gcm_filter): New. (gpgsm_decrypt): Use this filter if requested. Check authtag. * common/compliance.c (gnupg_cipher_is_allowed): Allow GCM for gpgsm in consumer (decrypt) de-vs mode.
Backported-from-master: 4980fb3c6dde8c1dda975e8a36d6086c8456a631
We allow GCM in de-vs mode for decryption although this has not been
evaluation. It is decryption and thus no serious harm may happen.
- Signed-off-by: Werner Koch <wk@gnupg.org>