gpg: Print info about the used AEAD algorithm.

* g10/misc.c (openpgp_cipher_algo_mode_name): New.
* g10/decrypt-data.c (decrypt_data): Use function here.
--

With out this change we would see

  gpg: cipher algorithm 'AES256' may not be used in
  --compliance=de-vs mode

This is confusing because AES256 is compliant.  Now we see

  gpg: cipher algorithm 'AES256.OCB' may not be used in
  --compliance=de-vs mode

which gives a hint on the problem.

3 files changed, 22 insertions, 2 deletions

diff --git a/g10/decrypt-data.c b/g10/decrypt-data.c
index 89d7c9a70..f9fc1d2c7 100644
--- a/g10/decrypt-data.c
+++ b/g10/decrypt-data.c
@@ -244,7 +244,7 @@ decrypt_data (ctrl_t ctrl, void *procctx, PKT_encrypted *ed, DEK *dek,
     {
       if (!openpgp_cipher_test_algo (dek->algo))
         log_info (_("%s encrypted data\n"),
-                  openpgp_cipher_algo_name (dek->algo));
+                  openpgp_cipher_algo_mode_name (dek->algo, ed->aead_algo));
       else
         log_info (_("encrypted with unknown algorithm %d\n"), dek->algo );
       dek->algo_info_printed = 1;
@@ -264,7 +264,7 @@ decrypt_data (ctrl_t ctrl, void *procctx, PKT_encrypted *ed, DEK *dek,
   if (!gnupg_cipher_is_allowed (opt.compliance, 0, dek->algo, ciphermode))
     {
       log_error (_("cipher algorithm '%s' may not be used in %s mode\n"),
-		 openpgp_cipher_algo_name (dek->algo),
+		 openpgp_cipher_algo_mode_name (dek->algo,ed->aead_algo),
 		 gnupg_compliance_option_string (opt.compliance));
       *compliance_error = 1;
       if (opt.flags.require_compliance)
diff --git a/g10/main.h b/g10/main.h
index 68360e218..273ddaaaf 100644
--- a/g10/main.h
+++ b/g10/main.h
@@ -122,6 +122,8 @@ enum gcry_cipher_algos map_cipher_openpgp_to_gcry (cipher_algo_t algo);
 int openpgp_cipher_blocklen (cipher_algo_t algo);
 int openpgp_cipher_test_algo(cipher_algo_t algo);
 const char *openpgp_cipher_algo_name (cipher_algo_t algo);
+const char *openpgp_cipher_algo_mode_name (cipher_algo_t algo,
+                                           aead_algo_t aead);
 
 gpg_error_t openpgp_aead_test_algo (aead_algo_t algo);
 const char *openpgp_aead_algo_name (aead_algo_t algo);
diff --git a/g10/misc.c b/g10/misc.c
index 634d30387..1d30bbc6d 100644
--- a/g10/misc.c
+++ b/g10/misc.c
@@ -608,6 +608,24 @@ openpgp_cipher_algo_name (cipher_algo_t algo)
 }
 
 
+/* Same as openpgp_cipher_algo_name but returns a string in the form
+ * "ALGO.MODE" if AEAD is not 0.  Note that in this version we do not
+ * print "ALGO.CFB" as we do in 2.3 to avoid confusing users.  */
+const char *
+openpgp_cipher_algo_mode_name (cipher_algo_t algo, aead_algo_t aead)
+{
+
+  if (aead == AEAD_ALGO_NONE)
+    return openpgp_cipher_algo_name (algo);
+
+  return map_static_strings ("openpgp_cipher_algo_mode_name", algo, aead,
+                             openpgp_cipher_algo_name (algo),
+                             ".",
+                             openpgp_aead_algo_name (aead),
+                             NULL);
+}
+
+
 /* Return 0 if ALGO is supported.  Return an error if not. */
 gpg_error_t
 openpgp_aead_test_algo (aead_algo_t algo)