gpg: New option --add-desig-revoker

* g10/gpg.c (oAddDesigRevoker): New.
(opts): Add new option.
* g10/options.h (opt): Add field desig_revokers.
* g10/keygen.c (get_parameter_idx): New.
(get_parameter): Make use of get_parameter_idx.
(prepare_desig_revoker): New.
(get_parameter_revkey): Add arg idx.
(proc_parameter_file): Add designated revokers.
(do_generate_keypair): Write all designated revokers.
--

(cherry picked from commit 3d094e2bcf6c9ed2cd405623f2dbc6131d04366f)

Support for v5 desig revokers has been removed.  However, we should
check whether we can add a longer v4 desig revoker fingerprint in
addition to the regular v4 desig revoker.

NEWS

@@ -22,6 +22,8 @@ Noteworthy changes in version 2.2.42 (unreleased)
   * gpg: Detect already compressed data also when using a pipe.  Also
     detect JPEG and PNG file formats.  [T6332]
 
+  * gpg: New option --add-desig-revoker.
+
   * gpgsm: Support ECC certificates.  [T6253]
 
   * gpgsm: Print PROGRESS status lines.  Add new --input-size-hint.

doc/gpg.texi

@@ -1713,6 +1713,19 @@ recipient's or signator's key.  If the given key is not locally
 available but an LDAP keyserver is configured the missing key is
 imported from that server.
 
+@item --add-desig-revoker [sensitive:]@var{fingerprint}
+@opindex add-desig-revoker
+Add the key specified by @var{fingerprint} as a designated revoker to
+newly created keys.  If the fingerprint is prefixed with the keyword
+``sensitive:'' that info is normally not exported wit the key.  This
+option may be given several time to add more than one designated
+revoker.  If the keyword ``clear'' is used instead of a fingerprint,
+all designated options previously encountered are discarded.
+Designated revokers are marked on the key as non-revocable.  Note that
+a designated revoker specified using a parameter file will also be
+added to the key.
+
+
 @item --trust-model @{pgp|classic|tofu|tofu+pgp|direct|always|auto@}
 @opindex trust-model
 Set what trust model GnuPG should follow. The models are:

g10/gpg.c

@@ -437,7 +437,7 @@ enum cmd_and_opt_values
     oForbidGenKey,
     oRequireCompliance,
     oCompatibilityFlags,
-    oKbxBufferSize,
+    oAddDesigRevoker,
 
     oNoop
   };
@@ -693,6 +693,7 @@ static ARGPARSE_OPTS opts[] = {
   ARGPARSE_s_n (oNoAutoCheckTrustDB, "no-auto-check-trustdb", "@"),
   ARGPARSE_s_s (oForceOwnertrust, "force-ownertrust", "@"),
 #endif
+  ARGPARSE_s_s (oAddDesigRevoker, "add-desig-revoker", "@"),
 
 
   ARGPARSE_header ("Input", N_("Options controlling the input")),
@@ -910,7 +911,6 @@ static ARGPARSE_OPTS opts[] = {
   /* Esoteric compatibility options.  */
   ARGPARSE_s_n (oRFC2440Text,      "rfc2440-text", "@"),
   ARGPARSE_s_n (oNoRFC2440Text, "no-rfc2440-text", "@"),
-  ARGPARSE_p_u (oKbxBufferSize,  "kbx-buffer-size", "@"),
 
   ARGPARSE_header (NULL, ""),  /* Stop the header group.  */
 
@@ -3655,9 +3655,12 @@ main (int argc, char **argv)
             opt.flags.require_compliance = 1;
             break;
 
-          case oKbxBufferSize:
+	  case oAddDesigRevoker:
-            keybox_set_buffersize (pargs.r.ret_ulong, 0);
+            if (!strcmp (pargs.r.ret_str, "clear"))
-            break;
+              FREE_STRLIST (opt.desig_revokers);
+            else
+              append_to_strlist (&opt.desig_revokers, pargs.r.ret_str);
+	    break;
 
 	  case oNoop: break;
 

g10/keygen.c

@@ -3671,14 +3671,29 @@ release_parameter_list (struct para_data_s *r)
     }
 }
 
+/* Return the N-th parameter of name KEY from PARA.  An IDX of 0
+ * returns the first and so on.  */
 static struct para_data_s *
-get_parameter( struct para_data_s *para, enum para_name key )
+get_parameter_idx (struct para_data_s *para, enum para_name key,
+                   unsigned int idx)
 {
-    struct para_data_s *r;
+  struct para_data_s *r;
 
-    for( r = para; r && r->key != key; r = r->next )
+  for(r = para; r; r = r->next)
-	;
+    if (r->key == key)
-    return r;
+      {
+        if (!idx)
+          return r;
+        idx--;
+      }
+  return NULL;
+}
+
+/* Return the first parameter of name KEY from PARA.  */
+static struct para_data_s *
+get_parameter (struct para_data_s *para, enum para_name key)
+{
+  return get_parameter_idx (para, key, 0);
 }
 
 static const char *
@@ -3826,6 +3841,68 @@ parse_parameter_usage (const char *fname,
 }
 
 
+/* Parse the revocation key specified by NAME, check that the public
+ * key exists (so that we can get the required public key algorithm),
+ * and return a parameter wit the revocation key information.  On
+ * error print a diagnostic and return NULL.  */
+static struct para_data_s *
+prepare_desig_revoker (ctrl_t ctrl, const char *name)
+{
+  gpg_error_t err;
+  struct para_data_s *para = NULL;
+  KEYDB_SEARCH_DESC desc;
+  int sensitive = 0;
+  struct revocation_key revkey;
+  PKT_public_key *revoker_pk = NULL;
+  size_t fprlen;
+
+  if (!ascii_strncasecmp (name, "sensitive:", 10) && !spacep (name+10))
+    {
+      name += 10;
+      sensitive = 1;
+    }
+
+  if (classify_user_id (name, &desc, 1)
+      || desc.mode != KEYDB_SEARCH_MODE_FPR)
+    {
+      log_info (_("\"%s\" is not a fingerprint\n"), name);
+      err = gpg_error (GPG_ERR_INV_NAME);
+      goto leave;
+    }
+
+  revoker_pk = xcalloc (1, sizeof *revoker_pk);
+  revoker_pk->req_usage = PUBKEY_USAGE_CERT;
+  err = get_pubkey_byname (ctrl, GET_PUBKEY_NO_AKL,
+                           NULL, revoker_pk, name, NULL, NULL, 1);
+  if (err)
+    goto leave;
+
+  fingerprint_from_pk (revoker_pk, revkey.fpr, &fprlen);
+  if (fprlen != 20)
+    {
+      log_info (_("cannot appoint a PGP 2.x style key as a "
+                  "designated revoker\n"));
+      err = gpg_error (GPG_ERR_UNUSABLE_PUBKEY);
+      goto leave;
+    }
+  revkey.class = 0x80;
+  if (sensitive)
+    revkey.class |= 0x40;
+  revkey.algid = revoker_pk->pubkey_algo;
+
+  para = xcalloc (1, sizeof *para);
+  para->key = pREVOKER;
+  memcpy (&para->u.revkey, &revkey, sizeof revkey);
+
+ leave:
+  if (err)
+    log_error ("invalid revocation key '%s': %s\n", name, gpg_strerror (err));
+  free_public_key (revoker_pk);
+  return para;
+}
+
+
+/* Parse a pREVOKER parameter into its dedicated parts.  */
 static int
 parse_revocation_key (const char *fname,
 		      struct para_data_s *para, enum para_name key)
@@ -3904,10 +3981,11 @@ get_parameter_uint( struct para_data_s *para, enum para_name key )
 }
 
 static struct revocation_key *
-get_parameter_revkey( struct para_data_s *para, enum para_name key )
+get_parameter_revkey (struct para_data_s *para, enum para_name key,
+                      unsigned int idx)
 {
-    struct para_data_s *r = get_parameter( para, key );
+  struct para_data_s *r = get_parameter_idx (para, key, idx);
-    return r? &r->u.revkey : NULL;
+  return r? &r->u.revkey : NULL;
 }
 
 static int
@@ -3918,6 +3996,7 @@ proc_parameter_file (ctrl_t ctrl, struct para_data_s *para, const char *fname,
   const char *s1, *s2, *s3;
   size_t n;
   char *p;
+  strlist_t sl;
   int is_default = 0;
   int have_user_id = 0;
   int err, algo;
@@ -4063,10 +4142,20 @@ proc_parameter_file (ctrl_t ctrl, struct para_data_s *para, const char *fname,
 	}
     }
 
-  /* Set revoker, if any. */
+  /* Set revoker from parameter file, if any.  Must be done first so
+   * that we don't find a parameter set via prepare_desig_revoker.  */
   if (parse_revocation_key (fname, para, pREVOKER))
     return -1;
 
+  /* Check and append revokers from the config file.  */
+  for (sl = opt.desig_revokers; sl; sl = sl->next)
+    {
+      r = prepare_desig_revoker (ctrl, sl->d);
+      if (!r)
+        return -1;
+      append_to_parameter (para, r);
+     }
+
 
   /* Make KEYCREATIONDATE from Creation-Date.  */
   r = get_parameter (para, pCREATIONDATE);
@@ -5104,6 +5193,7 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
   int algo;
   u32 expire;
   const char *key_from_hexgrip = NULL;
+  unsigned int idx;
 
   if (outctrl->dryrun)
     {
@@ -5205,7 +5295,10 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
       keyid_copy (pri_psk->main_keyid, pri_psk->keyid);
     }
 
-  if (!err && (revkey = get_parameter_revkey (para, pREVOKER)))
+  /* Write all signatures specifying designated revokers.  */
+  for (idx=0;
+       !err && (revkey = get_parameter_revkey (para, pREVOKER, idx));
+       idx++)
     err = write_direct_sig (ctrl, pub_root, pri_psk,
                             revkey, timestamp, cache_nonce);
 

g10/options.h

@@ -105,6 +105,9 @@ struct
    * the option --sender.  */
   strlist_t sender_list;
 
+  /* A list of fingerprints added as designated revokers to new keys.  */
+  strlist_t desig_revokers;
+
   int def_cert_level;
   int min_cert_level;
   int ask_cert_level;

g10/trust.c

@@ -59,7 +59,7 @@ register_trusted_key (const char *string)
   /* Some users have conf files with entries like
    *   trusted-key 0x1234567812345678    # foo
    * That is obviously wrong.  Before fixing bug#1206 trailing garbage
-   * on a key specification if was ignored.  We detect the above use case
+   * on a key specification was ignored.  We detect the above use case
    * here and  cut off the junk-looking-like-a comment.  */
   if (strchr (string, '#'))
     {