gpg: New option --auto-key-import

* g10/gpg.c (opts): New options --auto-key-import,
--no-auto-key-import, and --no-include-key-block.
(gpgconf_list): Add them.
* g10/options.h (opt): Add field flags.auto_key_import.
* g10/mainproc.c (check_sig_and_print): Use flag to enable that
feature.
* tools/gpgconf-comp.c: Give the new options a Basic config level.
--

Note that the --no variants of the options are intended for easy
disabling at the command line.

GnuPG-bug-id: 4856
Signed-off-by: Werner Koch <wk@gnupg.org>

Backported from master.

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

doc/gpg.texi

@@ -1818,6 +1818,20 @@ list.  The default is "local,wkd".
 @end table
 
 
+@item --auto-key-import
+@itemx --no-auto-key-import
+@opindex auto-key-import
+@opindex no-auto-key-import
+This is an offline mechanism to get a missing key for signature
+verification and for later encryption to this key.  If this option is
+enabled and a signature includes an embedded key, that key is
+used to verify the signature and on verification success that key is
+imported. The default is @option{--no-auto-key-import}.
+
+On the sender (signing) site the option @option{--include-key-block}
+needs to be used to put the public part of the signing key as “Key
+Block subpacket” into the signature.
+
 @item --auto-key-retrieve
 @itemx --no-auto-key-retrieve
 @opindex auto-key-retrieve
@@ -1828,22 +1842,26 @@ local keyring.  The default is @option{--no-auto-key-retrieve}.
 
 The order of methods tried to lookup the key is:
 
-1. If a preferred keyserver is specified in the signature and the
+1. If the option @option{--auto-key-import} is set and the signatures
+includes an embedded key, that key is used to verify the
+signature and on verification success that key is imported.
+
+2. If a preferred keyserver is specified in the signature and the
 option @option{honor-keyserver-url} is active (which is not the
 default), that keyserver is tried.  Note that the creator of the
 signature uses the option @option{--sig-keyserver-url} to specify the
 preferred keyserver for data signatures.
 
-2. If the signature has the Signer's UID set (e.g. using
+3. If the signature has the Signer's UID set (e.g. using
 @option{--sender} while creating the signature) a Web Key Directory
 (WKD) lookup is done.  This is the default configuration but can be
 disabled by removing WKD from the auto-key-locate list or by using the
 option @option{--disable-signer-uid}.
 
-3. If the option @option{honor-pka-record} is active, the legacy PKA
+4. If the option @option{honor-pka-record} is active, the legacy PKA
 method is used.
 
-4. If any keyserver is configured and the Issuer Fingerprint is part
+5. If any keyserver is configured and the Issuer Fingerprint is part
 of the signature (since GnuPG 2.1.16), the configured keyservers are
 tried.
 

g10/gpg.c

@@ -352,6 +352,8 @@ enum cmd_and_opt_values
     oNoRandomSeedFile,
     oAutoKeyRetrieve,
     oNoAutoKeyRetrieve,
+    oAutoKeyImport,
+    oNoAutoKeyImport,
     oUseAgent,
     oNoUseAgent,
     oGpgAgentInfo,
@@ -425,6 +427,7 @@ enum cmd_and_opt_values
     oNoSymkeyCache,
     oUseOnlyOpenPGPCard,
     oIncludeKeyBlock,
+    oNoIncludeKeyBlock,
 
     oNoop
   };
@@ -890,6 +893,8 @@ static ARGPARSE_OPTS opts[] = {
   ARGPARSE_s_n (oNoAutostart, "no-autostart", "@"),
   ARGPARSE_s_n (oNoSymkeyCache, "no-symkey-cache", "@"),
   ARGPARSE_s_n (oIncludeKeyBlock, "include-key-block", "@"),
+  ARGPARSE_s_n (oAutoKeyImport,   "auto-key-import", "@"),
+  ARGPARSE_s_n (oNoAutoKeyImport, "no-auto-key-import", "@"),
 
   /* Options to override new security defaults.  */
   ARGPARSE_s_n (oAllowWeakKeySignatures, "allow-weak-key-signatures", "@"),
@@ -1873,6 +1878,8 @@ gpgconf_list (const char *configfile)
   es_printf ("encrypt-to:%lu:\n", GC_OPT_FLAG_NONE);
   es_printf ("try-secret-key:%lu:\n", GC_OPT_FLAG_NONE);
   es_printf ("auto-key-locate:%lu:\n", GC_OPT_FLAG_NONE);
+  es_printf ("auto-key-import:%lu:\n", GC_OPT_FLAG_NONE);
+  es_printf ("include-key-block:%lu:\n", GC_OPT_FLAG_NONE);
   es_printf ("auto-key-retrieve:%lu:\n", GC_OPT_FLAG_NONE);
   es_printf ("log-file:%lu:\n", GC_OPT_FLAG_NONE);
   es_printf ("debug-level:%lu:\"none:\n", GC_OPT_FLAG_DEFAULT);
@@ -2993,6 +3000,7 @@ main (int argc, char **argv)
 
           case oDisableSignerUID: opt.flags.disable_signer_uid = 1; break;
           case oIncludeKeyBlock:  opt.flags.include_key_block = 1; break;
+          case oNoIncludeKeyBlock: opt.flags.include_key_block = 0; break;
 
 	  case oS2KMode:   opt.s2k_mode = pargs.r.ret_int; break;
 	  case oS2KDigest: s2k_digest_string = xstrdup(pargs.r.ret_str); break;
@@ -3375,6 +3383,9 @@ main (int argc, char **argv)
 	  case oIgnoreMDCError: opt.ignore_mdc_error = 1; break;
 	  case oNoRandomSeedFile: use_random_seed = 0; break;
 
+          case oAutoKeyImport: opt.flags.auto_key_import = 1; break;
+          case oNoAutoKeyImport: opt.flags.auto_key_import = 0; break;
+
 	  case oAutoKeyRetrieve:
             opt.keyserver_options.options |= KEYSERVER_AUTO_KEY_RETRIEVE;
             break;

g10/mainproc.c

@@ -1905,14 +1905,11 @@ check_sig_and_print (CTX c, kbnode_t node)
 
   rc = do_check_sig (c, node, NULL, NULL, &is_expkey, &is_revkey, &pk);
 
-  /* If the key is not found but the signaure includes a key bnlock we
-   * import that key block and trry again.  We keep this key block
-   * only if the signature verifies.  */
-  /* FIXME: Shall we add an option to disable it or use it only if
-   * --auto-key-retriueve is set?  */
+  /* If the key is not found but the signature includes a key block we
+   * use that key block for verification and on success import it.  */
   if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
-      && sig->flags.key_block)
-      /* && (opt.keyserver_options.options & KEYSERVER_AUTO_KEY_RETRIEVE)) */
+      && sig->flags.key_block
+      && opt.flags.auto_key_import)
     {
       PKT_public_key *included_pk;
       const byte *kblock;

g10/options.h

@@ -233,6 +233,7 @@ struct
     unsigned int large_rsa:1;
     unsigned int disable_signer_uid:1;
     unsigned int include_key_block:1;
+    unsigned int auto_key_import:1;
     /* Flag to enable experimental features from RFC4880bis.  */
     unsigned int rfc4880bis:1;
     /* Hack: --output is not given but OUTFILE was temporary set to "-".  */

tools/gpgconf-comp.c

@@ -756,6 +756,12 @@ static gc_option_t gc_options_gpg[] =
    { "auto-key-locate", GC_OPT_FLAG_NONE, GC_LEVEL_ADVANCED,
      "gnupg", N_("|MECHANISMS|use MECHANISMS to locate keys by mail address"),
      GC_ARG_TYPE_STRING, GC_BACKEND_GPG },
+   { "auto-key-import", GC_OPT_FLAG_NONE, GC_LEVEL_BASIC,
+     N_("import missing key from a signature"), "gnupg",
+     GC_ARG_TYPE_NONE, GC_BACKEND_GPG },
+   { "include-key-block", GC_OPT_FLAG_NONE, GC_LEVEL_BASIC,
+     N_("include the public key in signatures"), "gnupg",
+     GC_ARG_TYPE_NONE, GC_BACKEND_GPG },
    { "auto-key-retrieve", GC_OPT_FLAG_NONE, GC_LEVEL_EXPERT,
      NULL, NULL, GC_ARG_TYPE_NONE, GC_BACKEND_GPG },
    { "no-auto-key-retrieve", GC_OPT_FLAG_NONE, GC_LEVEL_INVISIBLE,