gpg: Prepare for signatures with ISSUER_FPR but without ISSUER.

* g10/getkey.c (get_pubkey_for_sig): New.
(get_pubkeyblock_for_sig): New.
* g10/mainproc.c (issuer_fpr_raw): Give global scope.
(check_sig_and_print): Use get_pubkeyblock_for_sig.
* g10/pkclist.c (check_signatures_trust): Use get_pubkey_for_sig.
* g10/sig-check.c (check_signature2): Ditto.
(check_signature_over_key_or_uid): Ditto.
--

GnuPG-bug-id: 4046

The whole getkey stuff is still a mess with way to much duplication
and missing caching of already fetched data.

Signed-off-by: Werner Koch <wk@gnupg.org>

g10/getkey.c

@@ -677,6 +677,24 @@ pk_from_block (PKT_public_key *pk, kbnode_t keyblock, kbnode_t found_key)
 }
 
 
+/* Specialized version of get_pubkey which retrieves the key based on
+ * information in SIG.  In contrast to get_pubkey PK is required.  */
+gpg_error_t
+get_pubkey_for_sig (ctrl_t ctrl, PKT_public_key *pk, PKT_signature *sig)
+{
+  const byte *fpr;
+  size_t fprlen;
+
+  /* First try the new ISSUER_FPR info.  */
+  fpr = issuer_fpr_raw (sig, &fprlen);
+  if (fpr && !get_pubkey_byfprint (ctrl, pk, NULL, fpr, fprlen))
+    return 0;
+
+  /* Fallback to use the ISSUER_KEYID.  */
+  return get_pubkey (ctrl, pk, sig->keyid);
+}
+
+
 /* Return the public key with the key id KEYID and store it at PK.
  * The resources in *PK should be released using
  * release_public_key_parts().  This function also stores a copy of
@@ -739,8 +757,9 @@ get_pubkey (ctrl_t ctrl, PKT_public_key * pk, u32 * keyid)
   /* Do a lookup.  */
   {
     struct getkey_ctx_s ctx;
-    KBNODE kb = NULL;
-    KBNODE found_key = NULL;
+    kbnode_t kb = NULL;
+    kbnode_t found_key = NULL;
+
     memset (&ctx, 0, sizeof ctx);
     ctx.exact = 1; /* Use the key ID exactly as given.  */
     ctx.not_allocated = 1;
@@ -863,6 +882,28 @@ get_pubkey_fast (PKT_public_key * pk, u32 * keyid)
 }
 
 
+/* Return the entire keyblock used to create SIG.  This is a
+ * specialized version of get_pubkeyblock.
+ *
+ * FIXME: This is a hack because get_pubkey_for_sig was already called
+ * and it could have used a cache to hold the key.  */
+kbnode_t
+get_pubkeyblock_for_sig (ctrl_t ctrl, PKT_signature *sig)
+{
+  const byte *fpr;
+  size_t fprlen;
+  kbnode_t keyblock;
+
+  /* First try the new ISSUER_FPR info.  */
+  fpr = issuer_fpr_raw (sig, &fprlen);
+  if (fpr && !get_pubkey_byfprint (ctrl, NULL, &keyblock, fpr, fprlen))
+    return keyblock;
+
+  /* Fallback to use the ISSUER_KEYID.  */
+  return get_pubkeyblock (ctrl, sig->keyid);
+}
+
+
 /* Return the key block for the key with key id KEYID or NULL, if an
  * error occurs.  Use release_kbnode() to release the key block.
  *
@@ -1802,6 +1843,8 @@ get_pubkey_byfprint (ctrl_t ctrl, PKT_public_key *pk, kbnode_t *r_keyblock,
       memset (&ctx, 0, sizeof ctx);
       ctx.exact = 1;
       ctx.not_allocated = 1;
+      /* FIXME: We should get the handle from the cache like we do in
+       * get_pubkey.  */
       ctx.kr_handle = keydb_new ();
       if (!ctx.kr_handle)
         return gpg_error_from_syserror ();

g10/keydb.h

@@ -283,6 +283,10 @@ void cache_public_key( PKT_public_key *pk );
 /* Disable and drop the public key cache.  */
 void getkey_disable_caches(void);
 
+/* Return the public key used for signature SIG and store it at PK.  */
+gpg_error_t get_pubkey_for_sig (ctrl_t ctrl,
+                                PKT_public_key *pk, PKT_signature *sig);
+
 /* Return the public key with the key id KEYID and store it at PK.  */
 int get_pubkey (ctrl_t ctrl, PKT_public_key *pk, u32 *keyid);
 
@@ -291,6 +295,10 @@ int get_pubkey (ctrl_t ctrl, PKT_public_key *pk, u32 *keyid);
    also only considers primary keys.  */
 int get_pubkey_fast (PKT_public_key *pk, u32 *keyid);
 
+/* Return the entire keyblock used to create SIG.  This is a
+ * specialized version of get_pubkeyblock.  */
+kbnode_t get_pubkeyblock_for_sig (ctrl_t ctrl, PKT_signature *sig);
+
 /* Return the key block for the key with KEYID.  */
 kbnode_t get_pubkeyblock (ctrl_t ctrl, u32 *keyid);
 

g10/mainproc.c

@@ -1751,7 +1751,7 @@ akl_has_wkd_method (void)
 /* Return the ISSUER fingerprint buffer and its lenbgth at R_LEN.
  * Returns NULL if not available.  The returned buffer is valid as
  * long as SIG is not modified.  */
-static const byte *
+const byte *
 issuer_fpr_raw (PKT_signature *sig, size_t *r_len)
 {
   const byte *p;
@@ -1768,7 +1768,7 @@ issuer_fpr_raw (PKT_signature *sig, size_t *r_len)
 }
 
 
-/* Return the ISSUER fingerprint string in human readbale format if
+/* Return the ISSUER fingerprint string in human readable format if
  * available.  Caller must release the string.  */
 /* FIXME: Move to another file.  */
 char *
@@ -2134,7 +2134,7 @@ check_sig_and_print (CTX c, kbnode_t node)
        * keyblock has already been fetched.  Thus we could use the
        * fingerprint or PK itself to lookup the entire keyblock.  That
        * would best be done with a cache.  */
-      keyblock = get_pubkeyblock (c->ctrl, sig->keyid);
+      keyblock = get_pubkeyblock_for_sig (c->ctrl, sig);
 
       snprintf (keyid_str, sizeof keyid_str, "%08lX%08lX [uncertain] ",
                 (ulong)sig->keyid[0], (ulong)sig->keyid[1]);

g10/packet.h

@@ -621,6 +621,7 @@ int proc_signature_packets_by_fd (ctrl_t ctrl,
 int proc_encryption_packets (ctrl_t ctrl, void *ctx, iobuf_t a);
 int list_packets( iobuf_t a );
 
+const byte *issuer_fpr_raw (PKT_signature *sig, size_t *r_len);
 char *issuer_fpr_string (PKT_signature *sig);
 
 /*-- parse-packet.c --*/

g10/pkclist.c

@@ -548,7 +548,7 @@ check_signatures_trust (ctrl_t ctrl, PKT_signature *sig)
   unsigned int trustlevel = TRUST_UNKNOWN;
   int rc=0;
 
-  rc = get_pubkey (ctrl, pk, sig->keyid );
+  rc = get_pubkey_for_sig (ctrl, pk, sig);
   if (rc)
     { /* this should not happen */
       log_error("Ooops; the key vanished  - can't check the trust\n");

g10/sig-check.c

@@ -156,7 +156,7 @@ check_signature2 (ctrl_t ctrl,
       log_info(_("WARNING: signature digest conflict in message\n"));
       rc = gpg_error (GPG_ERR_GENERAL);
     }
-  else if (get_pubkey (ctrl, pk, sig->keyid))
+  else if (get_pubkey_for_sig (ctrl, pk, sig))
     rc = gpg_error (GPG_ERR_NO_PUBKEY);
   else if (!gnupg_pk_is_allowed (opt.compliance, PK_USE_VERIFICATION,
                                  pk->pubkey_algo, pk->pkey,
@@ -926,7 +926,7 @@ check_signature_over_key_or_uid (ctrl_t ctrl, PKT_public_key *signer,
               if (IS_CERT (sig))
                 signer->req_usage = PUBKEY_USAGE_CERT;
 
-              rc = get_pubkey (ctrl, signer, sig->keyid);
+              rc = get_pubkey_for_sig (ctrl, signer, sig);
               if (rc)
                 {
                   xfree (signer);