gpg: New export option "mode1003".

* agent/command.c (cmd_export_key): Add option --mode1003.
(command_has_option): Ditto.
* g10/build-packet.c (do_key): Implement mode 1003.
* g10/parse-packet.c (parse_key): Ditto.
* g10/options.h (EXPORT_MODE1003): New.o
* g10/call-agent.c (agent_export_key): Add arg mode1003.
* g10/export.c (parse_export_options): Add "mode1003"
(secret_key_to_mode1003): New.
(receive_seckey_from_agent): Add arg mode1003.
(do_export_one_keyblock): Pass option down.
--

This option allows to export a secret key in GnuPG's native format.
Thus no re-encryption is required and further the public key parameters
are also authenticated if a protection passphrase has been used.

Note that --import is not yet able to handle this new mode.  Although
old version of GnuPG will bail out with "invalid packet" if a mode1003
exported secret key is seen.

agent/command.c

@@ -2935,7 +2935,7 @@ cmd_import_key (assuan_context_t ctx, char *line)
 
 
 static const char hlp_export_key[] =
-  "EXPORT_KEY [--cache-nonce=<nonce>] [--openpgp] <hexstring_with_keygrip>\n"
+  "EXPORT_KEY [--cache-nonce=<nonce>] [--openpgp|--mode1003] <hexkeygrip>\n"
   "\n"
   "Export a secret key from the key store.  The key will be encrypted\n"
   "using the current session's key wrapping key (cf. command KEYWRAP_KEY)\n"
@@ -2943,9 +2943,10 @@ static const char hlp_export_key[] =
   "prior to using this command.  The function takes the keygrip as argument.\n"
   "\n"
   "If --openpgp is used, the secret key material will be exported in RFC 4880\n"
-  "compatible passphrase-protected form.  Without --openpgp, the secret key\n"
+  "compatible passphrase-protected form.  If --mode1003 is use the secret key\n"
-  "material will be exported in the clear (after prompting the user to unlock\n"
+  "is exported as s-expression as storred locally.  Without those options,\n"
-  "it, if needed).\n";
+  "the secret key material will be exported in the clear (after prompting\n"
+  "the user to unlock it, if needed).\n";
 static gpg_error_t
 cmd_export_key (assuan_context_t ctx, char *line)
 {
@@ -2958,7 +2959,7 @@ cmd_export_key (assuan_context_t ctx, char *line)
   gcry_cipher_hd_t cipherhd = NULL;
   unsigned char *wrappedkey = NULL;
   size_t wrappedkeylen;
-  int openpgp;
+  int openpgp, mode1003;
   char *cache_nonce;
   char *passphrase = NULL;
   unsigned char *shadow_info = NULL;
@@ -2969,6 +2970,10 @@ cmd_export_key (assuan_context_t ctx, char *line)
     return leave_cmd (ctx, gpg_error (GPG_ERR_FORBIDDEN));
 
   openpgp = has_option (line, "--openpgp");
+  mode1003 = has_option (line, "--mode1003");
+  if (mode1003)
+    openpgp = 0;
+
   cache_nonce = option_value (line, "--cache-nonce");
   if (cache_nonce)
     {
@@ -3003,7 +3008,13 @@ cmd_export_key (assuan_context_t ctx, char *line)
     }
 
   /* Get the key from the file.  With the openpgp flag we also ask for
-     the passphrase so that we can use it to re-encrypt it.  */
+   * the passphrase so that we can use it to re-encrypt it.  In
+   * mode1003 we return the key as-is.  FIXME: if the key is still in
+   * OpenPGP-native mode we should first convert it to our internal
+   * protection.  */
+  if (mode1003)
+    err = agent_raw_key_from_file (ctrl, grip, &s_skey, NULL);
+  else
     err = agent_key_from_file (ctrl, cache_nonce,
                                ctrl->server_local->keydesc, grip,
                                &shadow_info, CACHE_MODE_IGNORE, NULL, &s_skey,
@@ -4150,6 +4161,11 @@ command_has_option (const char *cmd, const char *cmdopt)
       if (!strcmp (cmdopt, "newsymkey"))
         return 1;
     }
+  else if (!strcmp (cmd, "EXPORT_KEY"))
+    {
+      if (!strcmp (cmdopt, "mode1003"))
+        return 1;
+    }
 
   return 0;
 }

doc/DETAILS

@@ -1504,6 +1504,14 @@ CREATE TABLE signatures (
          - One octet with the length of the following serial number.
          - The serial number. Regardless of what the length octet
            indicates no more than 16 octets are stored.
+  - 3 :: The internal representation of a private key: For v4 keys we
+         first write 4 octets big endian length of the following
+         s-expression with the protected or unprotected private key;
+         for v5 keys this is not necessarily because that length
+         header is always there.  The actual data are N octets of
+         s-expression.  Any protection (including the real S2K) is
+         part of that data.  Note that the public key aparemters are
+         repeated in th s-expression.
 
   Note that gpg stores the GNU S2K Extension Number internally as an
   S2K Specifier with an offset of 1000.

doc/gpg.texi

@@ -2721,6 +2721,16 @@ opposite meaning.  The options are:
   each record to allow diverting the records to the corresponding zone
   file.
 
+  @item mode1003
+  Enable the use of a new secret key export format.  This format
+  avoids the re-encryption as required with the current OpenPGP format
+  and also improves the security of the secret key if it has been
+  protected with a passphrase.  Note that an unprotected key is
+  exported as-is and thus not secure; the general rule to convey
+  secret keys in an OpenPGP encrypted file still applies with this
+  mode.  Versions of GnuPG before 2.4.0 are not able to import such a
+  secret file.
+
 @end table
 
 @item --with-colons

g10/build-packet.c

@@ -674,7 +674,8 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
                 count += 8;   /* Salt.  */
               if (ski->s2k.mode == 3)
                 count++;      /* S2K.COUNT */
-              if (ski->s2k.mode != 1001 && ski->s2k.mode != 1002)
+              if (ski->s2k.mode != 1001 && ski->s2k.mode != 1002
+                   && ski->s2k.mode != 1003)
                 count += ski->ivlen;
 
               iobuf_put (a, count);
@@ -704,8 +705,9 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
           if (ski->s2k.mode == 3)
             iobuf_put (a, ski->s2k.count);
 
-          /* For our special modes 1001, 1002 we do not need an IV. */
+          /* For our special modes 1001..1003 we do not need an IV. */
-          if (ski->s2k.mode != 1001 && ski->s2k.mode != 1002)
+          if (ski->s2k.mode != 1001 && ski->s2k.mode != 1002
+               && ski->s2k.mode != 1003)
             iobuf_write (a, ski->iv, ski->ivlen);
 
         }
@@ -733,6 +735,22 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
           /* The serial number gets stored in the IV field.  */
           iobuf_write (a, ski->iv, ski->ivlen);
         }
+      else if (ski->s2k.mode == 1003)
+        {
+          /* GnuPG extension - Store raw s-expression. */
+          byte *p;
+          unsigned int ndatabits;
+
+          log_assert (gcry_mpi_get_flag (pk->pkey[npkey], GCRYMPI_FLAG_OPAQUE));
+
+          p = gcry_mpi_get_opaque (pk->pkey[npkey], &ndatabits);
+          /* For v5 keys we first write the number of octets of the
+           * following key material.  */
+          if (is_v5)
+            write_32 (a, p? (ndatabits+7)/8 : 0);
+          if (p)
+            iobuf_write (a, p, (ndatabits+7)/8 );
+        }
       else if (ski->is_protected)
         {
           /* The secret key is protected - write it out as it is.  */

g10/call-agent.c

@@ -2997,13 +2997,15 @@ agent_import_key (ctrl_t ctrl, const char *desc, char **cache_nonce_addr,
    keygrip, DESC a prompt to be displayed with the agent's passphrase
    question (needs to be plus+percent escaped).  if OPENPGP_PROTECTED
    is not zero, ensure that the key material is returned in RFC
-   4880-compatible passphrased-protected form.  If CACHE_NONCE_ADDR is
+   4880-compatible passphrased-protected form; if instead MODE1003 is
-   not NULL the agent is advised to first try a passphrase associated
+   not zero the raw gpg-agent private key format is requested (either
-   with that nonce.  On success the key is stored as a canonical
+   protected or unprotected).  If CACHE_NONCE_ADDR is not NULL the
-   S-expression at R_RESULT and R_RESULTLEN.  */
+   agent is advised to first try a passphrase associated with that
+   nonce.  On success the key is stored as a canonical S-expression at
+   R_RESULT and R_RESULTLEN.  */
 gpg_error_t
 agent_export_key (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
-                  int openpgp_protected, char **cache_nonce_addr,
+                  int openpgp_protected, int mode1003, char **cache_nonce_addr,
                   unsigned char **r_result, size_t *r_resultlen,
 		  u32 *keyid, u32 *mainkeyid, int pubkey_algo)
 {
@@ -3028,6 +3030,12 @@ agent_export_key (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
     return err;
   dfltparm.ctx = agent_ctx;
 
+  /* Check that the gpg-agent supports the --mode1003 option.  */
+  if (mode1003 && assuan_transact (agent_ctx,
+                                   "GETINFO cmd_has_option EXPORT_KEY mode1003",
+                                   NULL, NULL, NULL, NULL, NULL, NULL))
+    return gpg_error (GPG_ERR_NOT_SUPPORTED);
+
   if (desc)
     {
       snprintf (line, DIM(line), "SETKEYDESC %s", desc);
@@ -3038,7 +3046,7 @@ agent_export_key (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
     }
 
   snprintf (line, DIM(line), "EXPORT_KEY %s%s%s %s",
-            openpgp_protected ? "--openpgp ":"",
+            mode1003? "--mode1003" : openpgp_protected ? "--openpgp ":"",
             cache_nonce_addr && *cache_nonce_addr? "--cache-nonce=":"",
             cache_nonce_addr && *cache_nonce_addr? *cache_nonce_addr:"",
             hexkeygrip);

g10/call-agent.h

@@ -231,7 +231,7 @@ gpg_error_t agent_import_key (ctrl_t ctrl, const char *desc,
 /* Receive a key from the agent.  */
 gpg_error_t agent_export_key (ctrl_t ctrl, const char *keygrip,
                               const char *desc, int openpgp_protected,
-                              char **cache_nonce_addr,
+                              int mode1003, char **cache_nonce_addr,
                               unsigned char **r_result, size_t *r_resultlen,
                               u32 *keyid, u32 *mainkeyid, int pubkey_algo);
 

g10/export.c

@@ -2,6 +2,7 @@
  * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
  *               2005, 2010 Free Software Foundation, Inc.
  * Copyright (C) 1998-2016  Werner Koch
+ * Copyright (C) 2022 g10 Code GmbH
  *
  * This file is part of GnuPG.
  *
@@ -140,6 +141,9 @@ parse_export_options(char *str,unsigned int *options,int noisy)
        N_("use the GnuPG key backup format")},
       {"export-backup", EXPORT_BACKUP, NULL, NULL },
 
+      {"mode1003", EXPORT_MODE1003, NULL,
+       N_("export secret keys using the GnuPG format") },
+
       /* Aliases for backward compatibility */
       {"include-local-sigs",EXPORT_LOCAL_SIGS,NULL,NULL},
       {"include-attributes",EXPORT_ATTRIBUTES,NULL,NULL},
@@ -639,6 +643,183 @@ canon_pk_algo (enum gcry_pk_algos algo)
 }
 
 
+/* Take an s-expression wit the public and private key and change the
+ * parameter array in PK to include the secret parameters.  */
+static gpg_error_t
+secret_key_to_mode1003 (gcry_sexp_t s_key, PKT_public_key *pk)
+{
+  gpg_error_t err;
+  gcry_sexp_t list = NULL;
+  gcry_sexp_t l2;
+  enum gcry_pk_algos pk_algo;
+  struct seckey_info *ski;
+  int idx;
+  char *string;
+  size_t npkey, nskey;
+  gcry_mpi_t pub_params[10] = { NULL };
+
+  /* We look for a private-key, then the first element in it tells us
+     the type */
+  list = gcry_sexp_find_token (s_key, "protected-private-key", 0);
+  if (!list)
+    list = gcry_sexp_find_token (s_key, "private-key", 0);
+  if (!list)
+    {
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      goto leave;
+    }
+
+  log_assert (!pk->seckey_info);
+
+  /* Parse the gcrypt PK algo and check that it is okay.  */
+  l2 = gcry_sexp_cadr (list);
+  if (!l2)
+    {
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      goto leave;
+    }
+  gcry_sexp_release (list);
+  list = l2;
+  string = gcry_sexp_nth_string (list, 0);
+  if (!string)
+    {
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      goto leave;
+    }
+  pk_algo = gcry_pk_map_name (string);
+  xfree (string); string = NULL;
+  if (gcry_pk_algo_info (pk_algo, GCRYCTL_GET_ALGO_NPKEY, NULL, &npkey)
+      || gcry_pk_algo_info (pk_algo, GCRYCTL_GET_ALGO_NSKEY, NULL, &nskey)
+      || !npkey || npkey >= nskey)
+    {
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      goto leave;
+    }
+
+  /* Check that the pubkey algo and the received parameters matches
+   * those from the public key.  */
+  switch (canon_pk_algo (pk_algo))
+    {
+    case GCRY_PK_RSA:
+      if (!is_RSA (pk->pubkey_algo) || npkey != 2)
+        err = gpg_error (GPG_ERR_PUBKEY_ALGO);  /* Does not match.  */
+      else
+        err = gcry_sexp_extract_param (list, NULL, "ne",
+                                       &pub_params[0],
+                                       &pub_params[1],
+                                       NULL);
+      break;
+
+    case GCRY_PK_DSA:
+      if (!is_DSA (pk->pubkey_algo) || npkey != 4)
+        err = gpg_error (GPG_ERR_PUBKEY_ALGO);  /* Does not match.  */
+      else
+        err = gcry_sexp_extract_param (list, NULL, "pqgy",
+                                       &pub_params[0],
+                                       &pub_params[1],
+                                       &pub_params[2],
+                                       &pub_params[3],
+                                       NULL);
+      break;
+
+    case GCRY_PK_ELG:
+      if (!is_ELGAMAL (pk->pubkey_algo) || npkey != 3)
+        err = gpg_error (GPG_ERR_PUBKEY_ALGO);  /* Does not match.  */
+      else
+        err = gcry_sexp_extract_param (list, NULL, "pgy",
+                                       &pub_params[0],
+                                       &pub_params[1],
+                                       &pub_params[2],
+                                       NULL);
+      break;
+
+    case GCRY_PK_ECC:
+      err = 0;
+      if (!(pk->pubkey_algo == PUBKEY_ALGO_ECDSA
+            || pk->pubkey_algo == PUBKEY_ALGO_ECDH
+            || pk->pubkey_algo == PUBKEY_ALGO_EDDSA))
+        {
+          err = gpg_error (GPG_ERR_PUBKEY_ALGO);  /* Does not match.  */
+          goto leave;
+        }
+      npkey = 2;
+      if (pk->pubkey_algo == PUBKEY_ALGO_ECDH)
+        npkey++;
+      /* Dedicated check of the curve.  */
+      pub_params[0] = NULL;
+      err = match_curve_skey_pk (list, pk);
+      if (err)
+        goto leave;
+      /* ... and of the Q parameter.  */
+      err = sexp_extract_param_sos (list, "q", &pub_params[1]);
+      if (!err && (gcry_mpi_cmp (pk->pkey[1], pub_params[1])))
+        err = gpg_error (GPG_ERR_BAD_PUBKEY);
+      break;
+
+    default:
+      err = gpg_error (GPG_ERR_PUBKEY_ALGO);  /* Unknown.  */
+      break;
+    }
+  if (err)
+    goto leave;
+
+  nskey = npkey + 1;  /* We only have one skey param.  */
+  if (nskey > PUBKEY_MAX_NSKEY)
+    {
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      goto leave;
+    }
+
+  /* Check that the public key parameters match.  For ECC we already
+   * did this in the switch above.  */
+  if (canon_pk_algo (pk_algo) != GCRY_PK_ECC)
+    {
+      for (idx=0; idx < npkey; idx++)
+        if (gcry_mpi_cmp (pk->pkey[idx], pub_params[idx]))
+          {
+            err = gpg_error (GPG_ERR_BAD_PUBKEY);
+            goto leave;
+          }
+    }
+
+  /* Store the maybe protected secret key as an s-expression.  */
+  pk->seckey_info = ski = xtrycalloc (1, sizeof *ski);
+  if (!ski)
+    {
+      err = gpg_error_from_syserror ();
+      goto leave;
+    }
+
+  pk->seckey_info = ski = xtrycalloc (1, sizeof *ski);
+  if (!ski)
+    {
+      err = gpg_error_from_syserror ();
+      goto leave;
+    }
+
+  ski->is_protected = 1;
+  ski->s2k.mode = 1003;
+
+  {
+    unsigned char *buf;
+    size_t buflen;
+
+    err = make_canon_sexp (s_key, &buf, &buflen);
+    if (err)
+      goto leave;
+    pk->pkey[npkey] = gcry_mpi_set_opaque (NULL, buf, buflen*8);
+    for (idx=npkey+1; idx < PUBKEY_MAX_NSKEY; idx++)
+      pk->pkey[idx] = NULL;
+  }
+
+ leave:
+  gcry_sexp_release (list);
+  for (idx=0; idx < DIM(pub_params); idx++)
+    gcry_mpi_release (pub_params[idx]);
+  return err;
+}
+
+
 /* Take a cleartext dump of a secret key in PK and change the
  * parameter array in PK to include the secret parameters.  */
 static gpg_error_t
@@ -1248,6 +1429,11 @@ print_status_exported (PKT_public_key *pk)
  * passphrase-protected.  Otherwise, store secret key material in the
  * clear.
  *
+ * If MODE1003 is set, the key is requested in raw GnuPG format from
+ * the agent.  This usually does not require a passphrase unless the
+ * gpg-agent has not yet used the key and needs to convert it to its
+ * internal format first.
+ *
  * CACHE_NONCE_ADDR is used to share nonce for multiple key retrievals.
  *
  * If PK is NULL, the raw key is returned (e.g. for ssh export) at
@@ -1255,7 +1441,7 @@ print_status_exported (PKT_public_key *pk)
  */
 gpg_error_t
 receive_seckey_from_agent (ctrl_t ctrl, gcry_cipher_hd_t cipherhd,
-                           int cleartext,
+                           int cleartext, int mode1003,
                            char **cache_nonce_addr, const char *hexgrip,
                            PKT_public_key *pk, gcry_sexp_t *r_key)
 {
@@ -1275,7 +1461,7 @@ receive_seckey_from_agent (ctrl_t ctrl, gcry_cipher_hd_t cipherhd,
   if (pk)
     {
       prompt = gpg_format_keydesc (ctrl, pk, FORMAT_KEYDESC_EXPORT, 1);
-      err = agent_export_key (ctrl, hexgrip, prompt, !cleartext,
+      err = agent_export_key (ctrl, hexgrip, prompt, !cleartext, mode1003,
                               cache_nonce_addr,
                               &wrappedkey, &wrappedkeylen,
                               pk->keyid, pk->main_keyid, pk->pubkey_algo);
@@ -1283,7 +1469,7 @@ receive_seckey_from_agent (ctrl_t ctrl, gcry_cipher_hd_t cipherhd,
   else
     {
       prompt = gpg_format_keydesc (ctrl, NULL, FORMAT_KEYDESC_KEYGRIP, 1);
-      err = agent_export_key (ctrl, hexgrip, prompt, 0,
+      err = agent_export_key (ctrl, hexgrip, prompt, 0, 0,
                               NULL,
                               &wrappedkey, &wrappedkeylen,
                               NULL, NULL, 0);
@@ -1314,7 +1500,9 @@ receive_seckey_from_agent (ctrl_t ctrl, gcry_cipher_hd_t cipherhd,
   err = gcry_sexp_sscan (&s_skey, NULL, key, realkeylen);
   if (!err)
     {
-      if (pk && cleartext)
+      if (pk && mode1003)
+        err = secret_key_to_mode1003 (s_skey, pk);
+      else if (pk && cleartext)
         err = cleartext_secret_key_to_openpgp (s_skey, pk);
       else if (pk)
         err = transfer_format_to_openpgp (s_skey, pk);
@@ -1832,7 +2020,9 @@ do_export_one_keyblock (ctrl_t ctrl, kbnode_t keyblock, u32 *keyid,
           else if (!err)
             {
               err = receive_seckey_from_agent (ctrl, cipherhd,
-                                               cleartext, &cache_nonce,
+                                               cleartext,
+                                               !!(options & EXPORT_MODE1003),
+                                               &cache_nonce,
                                                hexgrip, pk, NULL);
               if (err)
                 {
@@ -2781,7 +2971,7 @@ export_secret_ssh_key (ctrl_t ctrl, const char *userid)
   if ((err = get_keywrap_key (ctrl, &cipherhd)))
     goto leave;
 
-  err = receive_seckey_from_agent (ctrl, cipherhd, 0, NULL, hexgrip, NULL,
+  err = receive_seckey_from_agent (ctrl, cipherhd, 0, 0, NULL, hexgrip, NULL,
                                    &skey);
   if (err)
     goto leave;

g10/keygen.c

@@ -5286,7 +5286,7 @@ card_store_key_with_backup (ctrl_t ctrl, PKT_public_key *sub_psk,
       goto leave;
     }
 
-  err = receive_seckey_from_agent (ctrl, cipherhd, 0,
+  err = receive_seckey_from_agent (ctrl, cipherhd, 0, 0,
                                    &cache_nonce, hexgrip, sk, NULL);
   if (err)
     {

g10/main.h

@@ -431,7 +431,7 @@ gpg_error_t export_pubkey_buffer (ctrl_t ctrl, const char *keyspec,
                                   void **r_data, size_t *r_datalen);
 
 gpg_error_t receive_seckey_from_agent (ctrl_t ctrl, gcry_cipher_hd_t cipherhd,
-                                       int cleartext,
+                                       int cleartext, int mode1003,
                                        char **cache_nonce_addr,
                                        const char *hexgrip,
                                        PKT_public_key *pk, gcry_sexp_t *r_key);

g10/options.h

@@ -407,6 +407,7 @@ EXTERN_UNLESS_MAIN_MODULE int memory_stat_debug_mode;
 #define EXPORT_DANE_FORMAT               (1<<7)
 #define EXPORT_BACKUP                    (1<<10)
 #define EXPORT_REVOCS                    (1<<11)
+#define EXPORT_MODE1003                  (1<<12)
 
 #define LIST_SHOW_PHOTOS                 (1<<0)
 #define LIST_SHOW_POLICY_URLS            (1<<1)

g10/parse-packet.c

@@ -2752,11 +2752,15 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 		  break;
 		case 1001:
 		  if (list_mode)
-		    es_fprintf (listfp, "\tgnu-dummy S2K");
+		    es_fprintf (listfp, "\tgnu-dummy");
 		  break;
 		case 1002:
 		  if (list_mode)
-		    es_fprintf (listfp, "\tgnu-divert-to-card S2K");
+		    es_fprintf (listfp, "\tgnu-divert-to-card");
+		  break;
+		case 1003:
+		  if (list_mode)
+		    es_fprintf (listfp, "\tgnu-mode1003");
 		  break;
 		default:
 		  if (list_mode)
@@ -2768,7 +2772,7 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 		}
 
               /* Print some info.  */
-	      if (list_mode)
+	      if (list_mode && ski->s2k.mode != 1003)
 		{
 		  es_fprintf (listfp, ", algo: %d,%s hash: %d",
                               ski->algo,
@@ -2779,8 +2783,9 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 		      es_fprintf (listfp, ", salt: ");
                       es_write_hexstring (listfp, ski->s2k.salt, 8, 0, NULL);
 		    }
-		  es_putc ('\n', listfp);
                 }
+              if (list_mode)
+                es_putc ('\n', listfp);
 
               /* Read remaining protection parameters.  */
 	      if (ski->s2k.mode == 3)
@@ -2838,7 +2843,7 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 	  ski->ivlen = openpgp_cipher_blocklen (ski->algo);
 	  log_assert (ski->ivlen <= sizeof (temp));
 
-	  if (ski->s2k.mode == 1001)
+	  if (ski->s2k.mode == 1001 || ski->s2k.mode == 1003)
 	    ski->ivlen = 0;
 	  else if (ski->s2k.mode == 1002)
 	    ski->ivlen = snlen < 16 ? snlen : 16;
@@ -2850,7 +2855,7 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 	    }
 	  for (i = 0; i < ski->ivlen; i++, pktlen--)
 	    temp[i] = iobuf_get_noeof (inp);
-	  if (list_mode)
+	  if (list_mode && ski->s2k.mode != 1003)
 	    {
 	      es_fprintf (listfp,
                           ski->s2k.mode == 1002 ? "\tserial-number: "
@@ -2888,6 +2893,35 @@ parse_key (IOBUF inp, int pkttype, unsigned long pktlen,
 						 10 * 8);
 	  pktlen = 0;
 	}
+      else if (ski->s2k.mode == 1003)
+	{
+          void *tmpp;
+
+	  if (pktlen < 2) /* At least two bytes for parenthesis.  */
+	    {
+              err = gpg_error (GPG_ERR_INV_PACKET);
+	      goto leave;
+	    }
+
+          tmpp = read_rest (inp, pktlen);
+          if (list_mode)
+            {
+              if (mpi_print_mode)
+                {
+                  char *tmpsxp = canon_sexp_to_string (tmpp, pktlen);
+                  es_fprintf (listfp, "\tskey[%d]: %s\n", npkey,
+                              tmpsxp? trim_trailing_spaces (tmpsxp)
+                              /*  */: "[invalid S-expression]");
+                  xfree (tmpsxp);
+                }
+              else
+                es_fprintf (listfp, "\tskey[%d]: [s-expression %lu octets]\n",
+                            npkey, pktlen);
+            }
+	  pk->pkey[npkey] = gcry_mpi_set_opaque (NULL,
+						 tmpp, tmpp? pktlen * 8 : 0);
+          pktlen = 0;
+	}
       else if (ski->is_protected)
 	{
           void *tmpp;