sm: Support signing using ECDSA.

* sm/gpgsm.h (struct certlist_s): Add helper field pk_algo.
* sm/sign.c (gpgsm_sign): Store the public key algo.  Take the hash
algo from the curve.  Improve diagnostic output in verbose mode.
--

GnuPG-bug-id: 4098
Signed-off-by: Werner Koch <wk@gnupg.org>

sm/gpgsm.h

@@ -245,6 +245,7 @@ struct certlist_s
   ksba_cert_t cert;
   int is_encrypt_to; /* True if the certificate has been set through
                         the --encrypto-to option. */
+  int pk_algo;       /* The PK_ALGO from CERT or 0 if not yet known.  */
   int hash_algo;     /* Used to track the hash algorithm to use.  */
   const char *hash_algo_oid;  /* And the corresponding OID.  */
 };

sm/sign.c

@@ -529,6 +529,7 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
       release_signerlist = 1;
     }
 
+
   /* Figure out the hash algorithm to use. We do not want to use the
      one for the certificate but if possible an OID for the plain
      algorithm.  */
@@ -537,6 +538,11 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
   for (i=0, cl=signerlist; cl; cl = cl->next, i++)
     {
       const char *oid;
+      unsigned int nbits;
+      int pk_algo;
+
+      pk_algo = gpgsm_get_key_algo_info (cl->cert, &nbits);
+      cl->pk_algo = pk_algo;
 
       if (opt.forced_digest_algo)
         {
@@ -545,7 +551,21 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
         }
       else
         {
+          if (pk_algo == GCRY_PK_ECC)
+            {
+              /* Map the Curve to a corresponding hash algo.  */
+              if (nbits <= 256)
+                oid = "2.16.840.1.101.3.4.2.1"; /* sha256 */
+              else if (nbits <= 384)
+                oid = "2.16.840.1.101.3.4.2.2"; /* sha384 */
+              else
+                oid = "2.16.840.1.101.3.4.2.3"; /* sha512 */
+            }
+          else
+            {
+              /* For RSA we reuse the hash algo used by the certificate.  */
               oid = ksba_cert_get_digest_algo (cl->cert);
+            }
           cl->hash_algo = oid ? gcry_md_map_name (oid) : 0;
         }
       switch (cl->hash_algo)
@@ -581,10 +601,6 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
           goto leave;
         }
 
-      {
-        unsigned int nbits;
-        int pk_algo = gpgsm_get_key_algo_info (cl->cert, &nbits);
-
       if (! gnupg_pk_is_allowed (opt.compliance, PK_USE_SIGNING, pk_algo,
                                  NULL, nbits, NULL))
         {
@@ -598,10 +614,10 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
           err = gpg_error (GPG_ERR_PUBKEY_ALGO);
           goto leave;
         }
-      }
+
     }
 
-  if (opt.verbose)
+  if (opt.verbose > 1 || opt.debug)
     {
       for (i=0, cl=signerlist; cl; cl = cl->next, i++)
         log_info (_("hash algorithm used for signer %d: %s (%s)\n"),
@@ -891,17 +907,23 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
                   goto leave;
                 }
               rc = 0;
+              if (opt.verbose)
                 {
-                int pkalgo = gpgsm_get_key_algo_info (cl->cert, NULL);
+                  char *pkalgostr = gpgsm_pubkey_algo_string (cl->cert, NULL);
+                  log_info (_("%s/%s signature using %s key %s\n"),
+                            pubkey_algo_to_string (cl->pk_algo),
+                            gcry_md_algo_name (cl->hash_algo),
+                            pkalgostr, fpr);
+                  xfree (pkalgostr);
+                }
               buf = xtryasprintf ("%c %d %d 00 %s %s",
                                   detached? 'D':'S',
-                                    pkalgo,
+                                  cl->pk_algo,
                                   cl->hash_algo,
                                   signed_at,
                                   fpr);
               if (!buf)
                 rc = gpg_error_from_syserror ();
-              }
               xfree (fpr);
               if (rc)
                 {
@@ -927,7 +949,6 @@ gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
   audit_log (ctrl->audit, AUDIT_SIGNING_DONE);
   log_info ("signature created\n");
 
-
  leave:
   if (rc)
     log_error ("error creating signature: %s <%s>\n",