Ejemplo n.º 1
0
static int
get_it( PKT_pubkey_enc *enc, DEK *dek, PKT_secret_key *sk, u32 *keyid )
{
  int rc;
  gcry_mpi_t plain_dek  = NULL;
  byte *frame = NULL;
  unsigned int n;
  size_t nframe;
  u16 csum, csum2;
  
  int card = 0;

  if (sk->is_protected && sk->protect.s2k.mode == 1002)
    { /* Note, that we only support RSA for now. */
#ifdef ENABLE_CARD_SUPPORT
      unsigned char *rbuf;
      size_t rbuflen;
      char *snbuf;
      unsigned char *indata = NULL;
      size_t indatalen;

      snbuf = serialno_and_fpr_from_sk (sk->protect.iv, sk->protect.ivlen, sk);

      if (gcry_mpi_aprint (GCRYMPI_FMT_USG, &indata, &indatalen, enc->data[0]))
        BUG ();

      rc = agent_scd_pkdecrypt (snbuf, indata, indatalen, &rbuf, &rbuflen);
      xfree (snbuf);
      xfree (indata);
      if (rc)
        goto leave;

      frame = rbuf;
      nframe = rbuflen;
      card = 1;
#else
      rc = gpg_error (GPG_ERR_NOT_SUPPORTED);
      goto leave;
#endif /*!ENABLE_CARD_SUPPORT*/
    }
  else
    {
      rc = pk_decrypt (sk->pubkey_algo, &plain_dek, enc->data, sk->skey );
      if( rc )
	goto leave;
      if (gcry_mpi_aprint (GCRYMPI_FMT_USG, &frame, &nframe, plain_dek))
        BUG();
      gcry_mpi_release (plain_dek); plain_dek = NULL;
    }

    /* Now get the DEK (data encryption key) from the frame
     *
     * Old versions encode the DEK in in this format (msb is left):
     *
     *	   0  1  DEK(16 bytes)	CSUM(2 bytes)  0  RND(n bytes) 2
     *
     * Later versions encode the DEK like this:
     *
     *	   0  2  RND(n bytes)  0  A  DEK(k bytes)  CSUM(2 bytes)
     *
     * (mpi_get_buffer already removed the leading zero).
     *
     * RND are non-zero randow bytes.
     * A   is the cipher algorithm
     * DEK is the encryption key (session key) with length k
     * CSUM
     */
    if (DBG_CIPHER)
      log_printhex ("DEK frame:", frame, nframe );
    n=0;
    if (!card)
      {
        if( n + 7 > nframe )
          { rc = G10ERR_WRONG_SECKEY; goto leave; }
        if( frame[n] == 1 && frame[nframe-1] == 2 ) {
          log_info(_("old encoding of the DEK is not supported\n"));
          rc = G10ERR_CIPHER_ALGO;
          goto leave;
        }
        if( frame[n] != 2 )  /* somethink is wrong */
          { rc = G10ERR_WRONG_SECKEY; goto leave; }
        for(n++; n < nframe && frame[n]; n++ ) /* skip the random bytes */
          ;
        n++; /* and the zero byte */
      }

    if( n + 4 > nframe )
	{ rc = G10ERR_WRONG_SECKEY; goto leave; }

    dek->keylen = nframe - (n+1) - 2;
    dek->algo = frame[n++];
    if( dek->algo ==  CIPHER_ALGO_IDEA )
	write_status(STATUS_RSA_OR_IDEA);
    rc = openpgp_cipher_test_algo (dek->algo);
    if( rc ) {
	if( !opt.quiet && gpg_err_code (rc) == GPG_ERR_CIPHER_ALGO ) {
	    log_info(_("cipher algorithm %d%s is unknown or disabled\n"),
                     dek->algo, dek->algo == CIPHER_ALGO_IDEA? " (IDEA)":"");
	    if(dek->algo==CIPHER_ALGO_IDEA)
	      idea_cipher_warn (0);
	}
	dek->algo = 0;
	goto leave;
    }
    if ( dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo) ) {
	rc = GPG_ERR_WRONG_SECKEY;
	goto leave;
    }

    /* copy the key to DEK and compare the checksum */
    csum  = frame[nframe-2] << 8;
    csum |= frame[nframe-1];
    memcpy( dek->key, frame+n, dek->keylen );
    for( csum2=0, n=0; n < dek->keylen; n++ )
	csum2 += dek->key[n];
    if( csum != csum2 ) {
	rc = G10ERR_WRONG_SECKEY;
	goto leave;
    }
    if( DBG_CIPHER )
        log_printhex ("DEK is:", dek->key, dek->keylen );
    /* check that the algo is in the preferences and whether it has expired */
    {
	PKT_public_key *pk = NULL;
        KBNODE pkb = get_pubkeyblock (keyid);

	if( !pkb ) {
            rc = -1;
	    log_error("oops: public key not found for preference check\n");
        }
	else if(pkb->pkt->pkt.public_key->selfsigversion > 3
		&& dek->algo != CIPHER_ALGO_3DES
		&& !opt.quiet
		&& !is_algo_in_prefs( pkb, PREFTYPE_SYM, dek->algo ))
	  log_info (_("WARNING: cipher algorithm %s not found in recipient"
                      " preferences\n"), openpgp_cipher_algo_name (dek->algo));
        if (!rc) {
            KBNODE k;
            
            for (k=pkb; k; k = k->next) {
                if (k->pkt->pkttype == PKT_PUBLIC_KEY 
                    || k->pkt->pkttype == PKT_PUBLIC_SUBKEY){
                    u32 aki[2];
        	    keyid_from_pk(k->pkt->pkt.public_key, aki);

                    if (aki[0]==keyid[0] && aki[1]==keyid[1]) {
                        pk = k->pkt->pkt.public_key;
                        break;
                    }
                }
            }
            if (!pk)
                BUG ();
            if ( pk->expiredate && pk->expiredate <= make_timestamp() ) {
                log_info(_("NOTE: secret key %s expired at %s\n"),
                         keystr(keyid), asctimestamp( pk->expiredate) );
            }
        }

        if ( pk &&  pk->is_revoked ) {
            log_info( _("NOTE: key has been revoked") );
            log_printf ("\n");
            show_revocation_reason( pk, 1 );
        }

	release_kbnode (pkb);
	rc = 0;
    }


  leave:
    gcry_mpi_release (plain_dek);
    xfree (frame);
    return rc;
}
Ejemplo n.º 2
0
static int
get_it( PKT_pubkey_enc *k, DEK *dek, PKT_secret_key *sk, u32 *keyid )
{
    int rc;
    MPI plain_dek  = NULL;
    byte *frame = NULL;
    unsigned n, nframe;
    u16 csum, csum2;

    rc = pubkey_decrypt(sk->pubkey_algo, &plain_dek, k->data, sk->skey );
    if( rc )
	goto leave;
    frame = mpi_get_buffer( plain_dek, &nframe, NULL );
    mpi_free( plain_dek ); plain_dek = NULL;

    /* Now get the DEK (data encryption key) from the frame
     *
     * Old versions encode the DEK in in this format (msb is left):
     *
     *	   0  1  DEK(16 bytes)	CSUM(2 bytes)  0  RND(n bytes) 2
     *
     * Later versions encode the DEK like this:
     *
     *	   0  2  RND(n bytes)  0  A  DEK(k bytes)  CSUM(2 bytes)
     *
     * (mpi_get_buffer already removed the leading zero).
     *
     * RND are non-zero randow bytes.
     * A   is the cipher algorithm
     * DEK is the encryption key (session key) with length k
     * CSUM
     */
    if( DBG_CIPHER )
	log_hexdump("DEK frame:", frame, nframe );
    n=0;
    if( n + 7 > nframe )
	{ rc = G10ERR_WRONG_SECKEY; goto leave; }
    if( frame[n] == 1 && frame[nframe-1] == 2 ) {
	log_info(_("old encoding of the DEK is not supported\n"));
	rc = G10ERR_CIPHER_ALGO;
	goto leave;
    }
    if( frame[n] != 2 )  /* somethink is wrong */
	{ rc = G10ERR_WRONG_SECKEY; goto leave; }
    for(n++; n < nframe && frame[n]; n++ ) /* skip the random bytes */
	;
    n++; /* and the zero byte */
    if( n + 4 > nframe )
	{ rc = G10ERR_WRONG_SECKEY; goto leave; }

    dek->keylen = nframe - (n+1) - 2;
    dek->algo = frame[n++];
    if( dek->algo ==  CIPHER_ALGO_IDEA )
	write_status(STATUS_RSA_OR_IDEA);
    rc = check_cipher_algo( dek->algo );
    if( rc ) {
	if( !opt.quiet && rc == G10ERR_CIPHER_ALGO ) {
	    log_info(_("cipher algorithm %d is unknown or disabled\n"),
							    dek->algo);
	}
	dek->algo = 0;
	goto leave;
    }
    if( (dek->keylen*8) != cipher_get_keylen( dek->algo ) ) {
	rc = G10ERR_WRONG_SECKEY;
	goto leave;
    }

    /* copy the key to DEK and compare the checksum */
    csum  = frame[nframe-2] << 8;
    csum |= frame[nframe-1];
    memcpy( dek->key, frame+n, dek->keylen );
    for( csum2=0, n=0; n < dek->keylen; n++ )
	csum2 += dek->key[n];
    if( csum != csum2 ) {
	rc = G10ERR_WRONG_SECKEY;
	goto leave;
    }
    if( DBG_CIPHER )
	log_hexdump("DEK is:", dek->key, dek->keylen );
    /* check that the algo is in the preferences and whether it has expired */
    {
	PKT_public_key *pk = m_alloc_clear( sizeof *pk );
	if( (rc = get_pubkey( pk, keyid )) )
	    log_error("public key problem: %s\n", g10_errstr(rc) );
	else if( !pk->local_id && query_trust_record(pk) )
	    log_error("can't check algorithm against preferences\n");
	else if( dek->algo != CIPHER_ALGO_3DES
	    && !is_algo_in_prefs( pk->local_id, PREFTYPE_SYM, dek->algo ) ) {
	    /* Don't print a note while we are not on verbose mode,
	     * the cipher is blowfish and the preferences have twofish
	     * listed */
	    if( opt.verbose || dek->algo != CIPHER_ALGO_BLOWFISH
		|| !is_algo_in_prefs( pk->local_id, PREFTYPE_SYM,
						    CIPHER_ALGO_TWOFISH ) )
		log_info(_(
		    "NOTE: cipher algorithm %d not found in preferences\n"),
								 dek->algo );
	}


	if( !rc && pk->expiredate && pk->expiredate <= make_timestamp() ) {
	    log_info(_("NOTE: secret key %08lX expired at %s\n"),
			   (ulong)keyid[1], asctimestamp( pk->expiredate) );
	}

	/* FIXME: check wheter the key has been revoked and display
	 * the revocation reason.  Actually the user should know this himself,
	 * but the sender might not know already and therefor the user
	 * should get a notice that an revoked key has been used to decode
	 * the message.  The user can than watch out for snakes send by
	 * one of those Eves outside his paradise :-)
	 */
	free_public_key( pk );
	rc = 0;
    }


  leave:
    mpi_free(plain_dek);
    m_free(frame);
    return rc;
}
Ejemplo n.º 3
0
static gpg_error_t
get_it (PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
{
  gpg_error_t err;
  byte *frame = NULL;
  unsigned int n;
  size_t nframe;
  u16 csum, csum2;
  int card = 0;
  gcry_sexp_t s_data;
  char *desc;
  char *keygrip;
  byte fp[MAX_FINGERPRINT_LEN];
  size_t fpn;
  const int pkalgo = map_pk_openpgp_to_gcry (sk->pubkey_algo);

  /* Get the keygrip.  */
  err = hexkeygrip_from_pk (sk, &keygrip);
  if (err)
    goto leave;

  /* Convert the data to an S-expression.  */
  if (pkalgo == GCRY_PK_ELG || pkalgo == GCRY_PK_ELG_E)
    {
      if (!enc->data[0] || !enc->data[1])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))",
                               enc->data[0], enc->data[1]);
    }
  else if (pkalgo == GCRY_PK_RSA || pkalgo == GCRY_PK_RSA_E)
    {
      if (!enc->data[0])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))",
                               enc->data[0]);
    }
  else if (pkalgo == GCRY_PK_ECDH)
    {
      if (!enc->data[0] || !enc->data[1])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
                               enc->data[0], enc->data[1]);
    }
  else
    err = gpg_error (GPG_ERR_BUG);

  if (err)
    goto leave;

  if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      fingerprint_from_pk (sk, fp, &fpn);
      assert (fpn == 20);
    }

  /* Decrypt. */
  desc = gpg_format_keydesc (sk, 0, 1);
  err = agent_pkdecrypt (NULL, keygrip, desc, s_data, &frame, &nframe);
  xfree (desc);
  gcry_sexp_release (s_data);
  if (err)
    goto leave;

  /* Now get the DEK (data encryption key) from the frame
   *
   * Old versions encode the DEK in in this format (msb is left):
   *
   *     0  1  DEK(16 bytes)  CSUM(2 bytes)  0  RND(n bytes) 2
   *
   * Later versions encode the DEK like this:
   *
   *     0  2  RND(n bytes)  0  A  DEK(k bytes)  CSUM(2 bytes)
   *
   * (mpi_get_buffer already removed the leading zero).
   *
   * RND are non-zero randow bytes.
   * A   is the cipher algorithm
   * DEK is the encryption key (session key) with length k
   * CSUM
   */
  if (DBG_CIPHER)
    log_printhex ("DEK frame:", frame, nframe);
  n = 0;

  if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      gcry_mpi_t shared_mpi;
      gcry_mpi_t decoded;

      /* At the beginning the frame are the bytes of shared point MPI.  */
      err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL);
      if (err)
        {
          err = gpg_error (GPG_ERR_WRONG_SECKEY);
          goto leave;
        }

      err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/,
                             shared_mpi, sk->pkey);
      mpi_release (shared_mpi);
      if(err)
        goto leave;

      /* Reuse NFRAME, which size is sufficient to include the session key.  */
      err = gcry_mpi_print (GCRYMPI_FMT_USG, frame, nframe, &nframe, decoded);
      mpi_release (decoded);
      if (err)
        goto leave;

      /* Now the frame are the bytes decrypted but padded session key.  */

      /* Allow double padding for the benefit of DEK size concealment.
         Higher than this is wasteful. */
      if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8
          || frame[nframe-1] > nframe)
        {
          err = gpg_error (GPG_ERR_WRONG_SECKEY);
          goto leave;
        }
      nframe -= frame[nframe-1]; /* Remove padding.  */
      assert (!n); /* (used just below) */
    }
  else
    {
      if (!card)
        {
          if (n + 7 > nframe)
            {
              err = gpg_error (GPG_ERR_WRONG_SECKEY);
              goto leave;
            }
          if (frame[n] == 1 && frame[nframe - 1] == 2)
            {
              log_info (_("old encoding of the DEK is not supported\n"));
              err = gpg_error (GPG_ERR_CIPHER_ALGO);
              goto leave;
            }
          if (frame[n] != 2) /* Something went wrong.  */
            {
              err = gpg_error (GPG_ERR_WRONG_SECKEY);
              goto leave;
            }
          for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes.  */
            ;
          n++; /* Skip the zero byte.  */
        }
    }

  if (n + 4 > nframe)
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }

  dek->keylen = nframe - (n + 1) - 2;
  dek->algo = frame[n++];
  if (dek->algo == CIPHER_ALGO_IDEA)
    write_status (STATUS_RSA_OR_IDEA);
  err = openpgp_cipher_test_algo (dek->algo);
  if (err)
    {
      if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO)
        {
          log_info (_("cipher algorithm %d%s is unknown or disabled\n"),
                    dek->algo,
                    dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : "");
          if (dek->algo == CIPHER_ALGO_IDEA)
            idea_cipher_warn (0);
        }
      dek->algo = 0;
      goto leave;
    }
  if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo))
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }

  /* Copy the key to DEK and compare the checksum.  */
  csum = frame[nframe - 2] << 8;
  csum |= frame[nframe - 1];
  memcpy (dek->key, frame + n, dek->keylen);
  for (csum2 = 0, n = 0; n < dek->keylen; n++)
    csum2 += dek->key[n];
  if (csum != csum2)
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }
  if (DBG_CIPHER)
    log_printhex ("DEK is:", dek->key, dek->keylen);

  /* Check that the algo is in the preferences and whether it has expired.  */
  {
    PKT_public_key *pk = NULL;
    KBNODE pkb = get_pubkeyblock (keyid);

    if (!pkb)
      {
        err = -1;
        log_error ("oops: public key not found for preference check\n");
      }
    else if (pkb->pkt->pkt.public_key->selfsigversion > 3
             && dek->algo != CIPHER_ALGO_3DES
             && !opt.quiet
             && !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo))
      log_info (_("WARNING: cipher algorithm %s not found in recipient"
                  " preferences\n"), openpgp_cipher_algo_name (dek->algo));
    if (!err)
      {
        KBNODE k;

        for (k = pkb; k; k = k->next)
          {
            if (k->pkt->pkttype == PKT_PUBLIC_KEY
                || k->pkt->pkttype == PKT_PUBLIC_SUBKEY)
              {
                u32 aki[2];
                keyid_from_pk (k->pkt->pkt.public_key, aki);

                if (aki[0] == keyid[0] && aki[1] == keyid[1])
                  {
                    pk = k->pkt->pkt.public_key;
                    break;
                  }
              }
          }
        if (!pk)
          BUG ();
        if (pk->expiredate && pk->expiredate <= make_timestamp ())
          {
            log_info (_("NOTE: secret key %s expired at %s\n"),
                      keystr (keyid), asctimestamp (pk->expiredate));
          }
      }

    if (pk && pk->flags.revoked)
      {
        log_info (_("NOTE: key has been revoked"));
        log_printf ("\n");
        show_revocation_reason (pk, 1);
      }

    release_kbnode (pkb);
    err = 0;
  }

 leave:
  xfree (frame);
  xfree (keygrip);
  return err;
}
Ejemplo n.º 4
0
static gpg_error_t
get_it (ctrl_t ctrl,
        PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid)
{
  gpg_error_t err;
  byte *frame = NULL;
  unsigned int n;
  size_t nframe;
  u16 csum, csum2;
  int padding;
  gcry_sexp_t s_data;
  char *desc;
  char *keygrip;
  byte fp[MAX_FINGERPRINT_LEN];
  size_t fpn;

  if (DBG_CLOCK)
    log_clock ("decryption start");

  /* Get the keygrip.  */
  err = hexkeygrip_from_pk (sk, &keygrip);
  if (err)
    goto leave;

  /* Convert the data to an S-expression.  */
  if (sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL
      || sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E)
    {
      if (!enc->data[0] || !enc->data[1])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))",
                               enc->data[0], enc->data[1]);
    }
  else if (sk->pubkey_algo == PUBKEY_ALGO_RSA
           || sk->pubkey_algo == PUBKEY_ALGO_RSA_E)
    {
      if (!enc->data[0])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))",
                               enc->data[0]);
    }
  else if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      if (!enc->data[0] || !enc->data[1])
        err = gpg_error (GPG_ERR_BAD_MPI);
      else
        err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
                               enc->data[1], enc->data[0]);
    }
  else
    err = gpg_error (GPG_ERR_BUG);

  if (err)
    goto leave;

  if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      fingerprint_from_pk (sk, fp, &fpn);
      log_assert (fpn == 20);
    }

  /* Decrypt. */
  desc = gpg_format_keydesc (ctrl, sk, FORMAT_KEYDESC_NORMAL, 1);
  err = agent_pkdecrypt (NULL, keygrip,
                         desc, sk->keyid, sk->main_keyid, sk->pubkey_algo,
                         s_data, &frame, &nframe, &padding);
  xfree (desc);
  gcry_sexp_release (s_data);
  if (err)
    goto leave;

  /* Now get the DEK (data encryption key) from the frame
   *
   * Old versions encode the DEK in this format (msb is left):
   *
   *     0  1  DEK(16 bytes)  CSUM(2 bytes)  0  RND(n bytes) 2
   *
   * Later versions encode the DEK like this:
   *
   *     0  2  RND(n bytes)  0  A  DEK(k bytes)  CSUM(2 bytes)
   *
   * (mpi_get_buffer already removed the leading zero).
   *
   * RND are non-zero randow bytes.
   * A   is the cipher algorithm
   * DEK is the encryption key (session key) with length k
   * CSUM
   */
  if (DBG_CRYPTO)
    log_printhex (frame, nframe, "DEK frame:");
  n = 0;

  if (sk->pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      gcry_mpi_t shared_mpi;
      gcry_mpi_t decoded;

      /* At the beginning the frame are the bytes of shared point MPI.  */
      err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL);
      if (err)
        {
          err = gpg_error (GPG_ERR_WRONG_SECKEY);
          goto leave;
        }

      err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/,
                             shared_mpi, sk->pkey);
      mpi_release (shared_mpi);
      if(err)
        goto leave;

      xfree (frame);
      err = gcry_mpi_aprint (GCRYMPI_FMT_USG, &frame, &nframe, decoded);
      mpi_release (decoded);
      if (err)
        goto leave;

      /* Now the frame are the bytes decrypted but padded session key.  */

      /* Allow double padding for the benefit of DEK size concealment.
         Higher than this is wasteful. */
      if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8
          || frame[nframe-1] > nframe)
        {
          err = gpg_error (GPG_ERR_WRONG_SECKEY);
          goto leave;
        }
      nframe -= frame[nframe-1]; /* Remove padding.  */
      log_assert (!n); /* (used just below) */
    }
  else
    {
      if (padding)
        {
          if (n + 7 > nframe)
            {
              err = gpg_error (GPG_ERR_WRONG_SECKEY);
              goto leave;
            }
          if (frame[n] == 1 && frame[nframe - 1] == 2)
            {
              log_info (_("old encoding of the DEK is not supported\n"));
              err = gpg_error (GPG_ERR_CIPHER_ALGO);
              goto leave;
            }
          if (frame[n] != 2) /* Something went wrong.  */
            {
              err = gpg_error (GPG_ERR_WRONG_SECKEY);
              goto leave;
            }
          for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes.  */
            ;
          n++; /* Skip the zero byte.  */
        }
    }

  if (n + 4 > nframe)
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }

  dek->keylen = nframe - (n + 1) - 2;
  dek->algo = frame[n++];
  err = openpgp_cipher_test_algo (dek->algo);
  if (err)
    {
      if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO)
        {
          log_info (_("cipher algorithm %d%s is unknown or disabled\n"),
                    dek->algo,
                    dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : "");
        }
      dek->algo = 0;
      goto leave;
    }
  if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo))
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }

  /* Copy the key to DEK and compare the checksum.  */
  csum = buf16_to_u16 (frame+nframe-2);
  memcpy (dek->key, frame + n, dek->keylen);
  for (csum2 = 0, n = 0; n < dek->keylen; n++)
    csum2 += dek->key[n];
  if (csum != csum2)
    {
      err = gpg_error (GPG_ERR_WRONG_SECKEY);
      goto leave;
    }
  if (DBG_CLOCK)
    log_clock ("decryption ready");
  if (DBG_CRYPTO)
    log_printhex (dek->key, dek->keylen, "DEK is:");

  /* Check that the algo is in the preferences and whether it has
   * expired.  Also print a status line with the key's fingerprint.  */
  {
    PKT_public_key *pk = NULL;
    PKT_public_key *mainpk = NULL;
    KBNODE pkb = get_pubkeyblock (ctrl, keyid);

    if (!pkb)
      {
        err = -1;
        log_error ("oops: public key not found for preference check\n");
      }
    else if (pkb->pkt->pkt.public_key->selfsigversion > 3
             && dek->algo != CIPHER_ALGO_3DES
             && !opt.quiet
             && !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo))
      log_info (_("WARNING: cipher algorithm %s not found in recipient"
                  " preferences\n"), openpgp_cipher_algo_name (dek->algo));

    if (!err)
      {
        kbnode_t k;
        int first = 1;

        for (k = pkb; k; k = k->next)
          {
            if (k->pkt->pkttype == PKT_PUBLIC_KEY
                || k->pkt->pkttype == PKT_PUBLIC_SUBKEY)
              {
                u32 aki[2];

                if (first)
                  {
                    first = 0;
                    mainpk = k->pkt->pkt.public_key;
                  }

                keyid_from_pk (k->pkt->pkt.public_key, aki);
                if (aki[0] == keyid[0] && aki[1] == keyid[1])
                  {
                    pk = k->pkt->pkt.public_key;
                    break;
                  }
              }
          }
        if (!pk)
          BUG ();
        if (pk->expiredate && pk->expiredate <= make_timestamp ())
          {
            log_info (_("Note: secret key %s expired at %s\n"),
                      keystr (keyid), asctimestamp (pk->expiredate));
          }
      }

    if (pk && pk->flags.revoked)
      {
        log_info (_("Note: key has been revoked"));
        log_printf ("\n");
        show_revocation_reason (ctrl, pk, 1);
      }

    if (is_status_enabled () && pk && mainpk)
      {
        char pkhex[MAX_FINGERPRINT_LEN*2+1];
        char mainpkhex[MAX_FINGERPRINT_LEN*2+1];

        hexfingerprint (pk, pkhex, sizeof pkhex);
        hexfingerprint (mainpk, mainpkhex, sizeof mainpkhex);

        /* Note that we do not want to create a trustdb just for
         * getting the ownertrust: If there is no trustdb there can't
         * be ulitmately trusted key anyway and thus the ownertrust
         * value is irrelevant.  */
        write_status_printf (STATUS_DECRYPTION_KEY, "%s %s %c",
                             pkhex, mainpkhex,
                             get_ownertrust_info (ctrl, mainpk, 1));

      }

    release_kbnode (pkb);
    err = 0;
  }

 leave:
  xfree (frame);
  xfree (keygrip);
  return err;
}