path: root/lib/opencdk/read-packet.c

/* read-packet.c - Read OpenPGP packets
 * Copyright (C) 2001-2003, 2007-2008, 2010, 2012 Free Software
 * Foundation, Inc.
 *
 * Author: Timo Schulz
 *
 * This file is part of OpenCDK.
 *
 * The OpenCDK library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <string.h>
#include <stdio.h>
#include <time.h>
#include <assert.h>

#include "opencdk.h"
#include "main.h"
#include "packet.h"
#include "types.h"
#include <algorithms.h>
#include <gnutls_str.h>
#include <minmax.h>

/* The version of the MDC packet considering the lastest OpenPGP draft. */
#define MDC_PKT_VER 1

static int
stream_read (cdk_stream_t s, void *buf, size_t buflen, size_t * r_nread)
{
  *r_nread = cdk_stream_read (s, buf, buflen);
  return *r_nread > 0 ? 0 : _cdk_stream_get_errno (s);
}


/* Try to read 4 octets from the stream. */
static u32
read_32 (cdk_stream_t s)
{
  byte buf[4];
  size_t nread;

  assert (s != NULL);

  stream_read (s, buf, 4, &nread);
  if (nread != 4)
    return (u32) - 1;
  return buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3];
}


/* Try to read 2 octets from a stream. */
static u16
read_16 (cdk_stream_t s)
{
  byte buf[2];
  size_t nread;

  assert (s != NULL);

  stream_read (s, buf, 2, &nread);
  if (nread != 2)
    return (u16) - 1;
  return buf[0] << 8 | buf[1];
}


/* read about S2K at http://tools.ietf.org/html/rfc4880#section-3.7.1 */
static cdk_error_t
read_s2k (cdk_stream_t inp, cdk_s2k_t s2k)
{
  size_t nread;

  s2k->mode = cdk_stream_getc (inp);
  s2k->hash_algo = cdk_stream_getc (inp);
  if (s2k->mode == CDK_S2K_SIMPLE)
    return 0;
  else if (s2k->mode == CDK_S2K_SALTED || s2k->mode == CDK_S2K_ITERSALTED)
    {
      if (stream_read (inp, s2k->salt, DIM (s2k->salt), &nread))
        return CDK_Inv_Packet;
      if (nread != DIM (s2k->salt))
        return CDK_Inv_Packet;

      if (s2k->mode == CDK_S2K_ITERSALTED)
        s2k->count = cdk_stream_getc (inp);
    }
  else if (s2k->mode == CDK_S2K_GNU_EXT)
    {
      /* GNU extensions to the S2K : read DETAILS from gnupg */
      return 0;
    }
  else
    return CDK_Not_Implemented;

  return 0;
}


static cdk_error_t
read_mpi (cdk_stream_t inp, bigint_t * ret_m, int secure)
{
  bigint_t m;
  int err;
  byte buf[MAX_MPI_BYTES + 2];
  size_t nread, nbits;
  cdk_error_t rc;

  if (!inp || !ret_m)
    return CDK_Inv_Value;

  *ret_m = NULL;
  nbits = read_16 (inp);
  nread = (nbits + 7) / 8;

  if (nbits > MAX_MPI_BITS || nbits == 0)
    {
      _gnutls_write_log ("read_mpi: too large %d bits\n", (int) nbits);
      return CDK_MPI_Error;     /* Sanity check */
    }

  rc = stream_read (inp, buf + 2, nread, &nread);
  if (!rc && nread != ((nbits + 7) / 8))
    {
      _gnutls_write_log ("read_mpi: too short %d < %d\n", (int) nread,
                         (int) ((nbits + 7) / 8));
      return CDK_MPI_Error;
    }

  buf[0] = nbits >> 8;
  buf[1] = nbits >> 0;
  nread += 2;
  err = _gnutls_mpi_scan_pgp (&m, buf, nread);
  if (err < 0)
    return map_gnutls_error (err);

  *ret_m = m;
  return rc;
}


/* Read the encoded packet length directly from the file 
   object INP and return it. Reset RET_PARTIAL if this is
   the last packet in block mode. */
size_t
_cdk_pkt_read_len (FILE * inp, size_t * ret_partial)
{
  int c1, c2;
  size_t pktlen;

  c1 = fgetc (inp);
  if (c1 == EOF)
    return (size_t) EOF;
  if (c1 < 224 || c1 == 255)
    *ret_partial = 0;           /* End of partial data */
  if (c1 < 192)
    pktlen = c1;
  else if (c1 >= 192 && c1 <= 223)
    {
      c2 = fgetc (inp);
      if (c2 == EOF)
        return (size_t) EOF;
      pktlen = ((c1 - 192) << 8) + c2 + 192;
    }
  else if (c1 == 255)
    {
      pktlen = fgetc (inp) << 24;
      pktlen |= fgetc (inp) << 16;
      pktlen |= fgetc (inp) << 8;
      pktlen |= fgetc (inp) << 0;
    }
  else
    pktlen = 1 << (c1 & 0x1f);
  return pktlen;
}


static cdk_error_t
read_pubkey_enc (cdk_stream_t inp, size_t pktlen, cdk_pkt_pubkey_enc_t pke)
{
  size_t i, nenc;

  if (!inp || !pke)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_pubkey_enc: %d octets\n", (int) pktlen);

  if (pktlen < 12)
    return CDK_Inv_Packet;
  pke->version = cdk_stream_getc (inp);
  if (pke->version < 2 || pke->version > 3)
    return CDK_Inv_Packet;
  pke->keyid[0] = read_32 (inp);
  pke->keyid[1] = read_32 (inp);
  if (!pke->keyid[0] && !pke->keyid[1])
    pke->throw_keyid = 1;       /* RFC2440 "speculative" keyID */
  pke->pubkey_algo = _pgp_pub_algo_to_cdk (cdk_stream_getc (inp));
  nenc = cdk_pk_get_nenc (pke->pubkey_algo);
  if (!nenc)
    return CDK_Inv_Algo;
  for (i = 0; i < nenc; i++)
    {
      cdk_error_t rc = read_mpi (inp, &pke->mpi[i], 0);
      if (rc)
        return rc;
    }

  return 0;
}



static cdk_error_t
read_mdc (cdk_stream_t inp, cdk_pkt_mdc_t mdc)
{
  size_t n;
  cdk_error_t rc;

  if (!inp || !mdc)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_mdc:\n");

  rc = stream_read (inp, mdc->hash, DIM (mdc->hash), &n);
  if (rc)
    return rc;

  return n != DIM (mdc->hash) ? CDK_Inv_Packet : 0;
}


static cdk_error_t
read_compressed (cdk_stream_t inp, size_t pktlen, cdk_pkt_compressed_t c)
{
  if (!inp || !c)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_compressed: %d octets\n", (int) pktlen);

  c->algorithm = cdk_stream_getc (inp);
  if (c->algorithm > 3)
    return CDK_Inv_Packet;

  /* don't know the size, so we read until EOF */
  if (!pktlen)
    {
      c->len = 0;
      c->buf = inp;
    }

  /* FIXME: Support partial bodies. */
  return 0;
}


static cdk_error_t
read_public_key (cdk_stream_t inp, size_t pktlen, cdk_pkt_pubkey_t pk)
{
  size_t i, ndays, npkey;

  if (!inp || !pk)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_public_key: %d octets\n", (int) pktlen);

  pk->is_invalid = 1;           /* default to detect missing self signatures */
  pk->is_revoked = 0;
  pk->has_expired = 0;

  pk->version = cdk_stream_getc (inp);
  if (pk->version < 2 || pk->version > 4)
    return CDK_Inv_Packet_Ver;
  pk->timestamp = read_32 (inp);
  if (pk->version < 4)
    {
      ndays = read_16 (inp);
      if (ndays)
        pk->expiredate = pk->timestamp + ndays * 86400L;
    }

  pk->pubkey_algo = _pgp_pub_algo_to_cdk (cdk_stream_getc (inp));
  npkey = cdk_pk_get_npkey (pk->pubkey_algo);
  if (!npkey)
    {
      gnutls_assert ();
      _gnutls_write_log ("invalid public key algorithm %d\n",
                         pk->pubkey_algo);
      return CDK_Inv_Algo;
    }
  for (i = 0; i < npkey; i++)
    {
      cdk_error_t rc = read_mpi (inp, &pk->mpi[i], 0);
      if (rc)
        return rc;
    }

  /* This value is just for the first run and will be
     replaced with the actual key flags from the self signature. */
  pk->pubkey_usage = 0;
  return 0;
}


static cdk_error_t
read_public_subkey (cdk_stream_t inp, size_t pktlen, cdk_pkt_pubkey_t pk)
{
  if (!inp || !pk)
    return CDK_Inv_Value;
  return read_public_key (inp, pktlen, pk);
}

static cdk_error_t
read_secret_key (cdk_stream_t inp, size_t pktlen, cdk_pkt_seckey_t sk)
{
  size_t p1, p2, nread;
  int i, nskey;
  int rc;

  if (!inp || !sk || !sk->pk)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_secret_key: %d octets\n", (int) pktlen);

  p1 = cdk_stream_tell (inp);
  rc = read_public_key (inp, pktlen, sk->pk);
  if (rc)
    return rc;

  sk->s2k_usage = cdk_stream_getc (inp);
  sk->protect.sha1chk = 0;
  if (sk->s2k_usage == 254 || sk->s2k_usage == 255)
    {
      sk->protect.sha1chk = (sk->s2k_usage == 254);
      sk->protect.algo = _pgp_cipher_to_gnutls (cdk_stream_getc (inp));
      sk->protect.s2k = cdk_calloc (1, sizeof *sk->protect.s2k);
      if (!sk->protect.s2k)
        return CDK_Out_Of_Core;
      rc = read_s2k (inp, sk->protect.s2k);
      if (rc)
        return rc;
      /* refer to --export-secret-subkeys in gpg(1) */
      if (sk->protect.s2k->mode == CDK_S2K_GNU_EXT)
        sk->protect.ivlen = 0;
      else
        {
          sk->protect.ivlen = gnutls_cipher_get_block_size (sk->protect.algo);
          if (!sk->protect.ivlen)
            return CDK_Inv_Packet;
          rc = stream_read (inp, sk->protect.iv, sk->protect.ivlen, &nread);
          if (rc)
            return rc;
          if (nread != sk->protect.ivlen)
            return CDK_Inv_Packet;
        }
    }
  else
    sk->protect.algo = _pgp_cipher_to_gnutls (sk->s2k_usage);
  if (sk->protect.algo == GNUTLS_CIPHER_NULL)
    {
      sk->csum = 0;
      nskey = cdk_pk_get_nskey (sk->pk->pubkey_algo);
      if (!nskey)
        {
          gnutls_assert ();
          return CDK_Inv_Algo;
        }
      for (i = 0; i < nskey; i++)
        {
          rc = read_mpi (inp, &sk->mpi[i], 1);
          if (rc)
            return rc;
        }
      sk->csum = read_16 (inp);
      sk->is_protected = 0;
    }
  else if (sk->pk->version < 4)
    {
      /* The length of each multiprecision integer is stored in plaintext. */
      nskey = cdk_pk_get_nskey (sk->pk->pubkey_algo);
      if (!nskey)
        {
          gnutls_assert ();
          return CDK_Inv_Algo;
        }
      for (i = 0; i < nskey; i++)
        {
          rc = read_mpi (inp, &sk->mpi[i], 1);
          if (rc)
            return rc;
        }
      sk->csum = read_16 (inp);
      sk->is_protected = 1;
    }
  else
    {
      /* We need to read the rest of the packet because we do not
         have any information how long the encrypted mpi's are */
      p2 = cdk_stream_tell (inp);
      p2 -= p1;
      sk->enclen = pktlen - p2;
      if (sk->enclen < 2)
        return CDK_Inv_Packet;  /* at least 16 bits for the checksum! */
      sk->encdata = cdk_calloc (1, sk->enclen + 1);
      if (!sk->encdata)
        return CDK_Out_Of_Core;
      if (stream_read (inp, sk->encdata, sk->enclen, &nread))
        return CDK_Inv_Packet;
      /* Handle the GNU S2K extensions we know (just gnu-dummy right now): */
      if (sk->protect.s2k->mode == CDK_S2K_GNU_EXT)
        {
          unsigned char gnumode;
          if ((sk->enclen < strlen ("GNU") + 1) ||
              (0 != memcmp ("GNU", sk->encdata, strlen ("GNU"))))
            return CDK_Inv_Packet;
          gnumode = sk->encdata[strlen ("GNU")];
          /* we only handle gnu-dummy (mode 1).
             mode 2 should refer to external smart cards.
           */
          if (gnumode != 1)
            return CDK_Inv_Packet;
          /* gnu-dummy should have no more data */
          if (sk->enclen != strlen ("GNU") + 1)
            return CDK_Inv_Packet;
        }
      nskey = cdk_pk_get_nskey (sk->pk->pubkey_algo);
      if (!nskey)
        {
          gnutls_assert ();
          return CDK_Inv_Algo;
        }
      /* We mark each MPI entry with NULL to indicate a protected key. */
      for (i = 0; i < nskey; i++)
        sk->mpi[i] = NULL;
      sk->is_protected = 1;
    }

  sk->is_primary = 1;
  _cdk_copy_pk_to_sk (sk->pk, sk);
  return 0;
}


static cdk_error_t
read_secret_subkey (cdk_stream_t inp, size_t pktlen, cdk_pkt_seckey_t sk)
{
  cdk_error_t rc;

  if (!inp || !sk || !sk->pk)
    return CDK_Inv_Value;

  rc = read_secret_key (inp, pktlen, sk);
  sk->is_primary = 0;
  return rc;
}

#define ATTRIBUTE "[attribute]"

static cdk_error_t
read_attribute (cdk_stream_t inp, size_t pktlen, cdk_pkt_userid_t attr, int name_size)
{
  const byte *p;
  byte *buf;
  size_t len, nread;
  cdk_error_t rc;

  if (!inp || !attr || !pktlen)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_attribute: %d octets\n", (int) pktlen);

  _gnutls_str_cpy (attr->name, name_size, ATTRIBUTE);
  attr->len = MIN(name_size, sizeof(ATTRIBUTE)-1);

  buf = cdk_calloc (1, pktlen);
  if (!buf)
    return CDK_Out_Of_Core;
  rc = stream_read (inp, buf, pktlen, &nread);
  if (rc)
    {
      cdk_free (buf);
      return CDK_Inv_Packet;
    }
  p = buf;
  len = *p++;
  pktlen--;
  if (len == 255)
    {
      len = _cdk_buftou32 (p);
      p += 4;
      pktlen -= 4;
    }
  else if (len >= 192)
    {
      if (pktlen < 2)
        {
          cdk_free (buf);
          return CDK_Inv_Packet;
        }
      len = ((len - 192) << 8) + *p + 192;
      p++;
      pktlen--;
    }

  if (*p != 1)                  /* Currently only 1, meaning an image, is defined. */
    {
      cdk_free (buf);
      return CDK_Inv_Packet;
    }
  p++;
  len--;

  if (len >= pktlen)
    return CDK_Inv_Packet;
  attr->attrib_img = cdk_calloc (1, len);
  if (!attr->attrib_img)
    {
      cdk_free (buf);
      return CDK_Out_Of_Core;
    }
  attr->attrib_len = len;
  memcpy (attr->attrib_img, p, len);
  cdk_free (buf);
  return rc;
}


static cdk_error_t
read_user_id (cdk_stream_t inp, size_t pktlen, cdk_pkt_userid_t user_id)
{
  size_t nread;
  cdk_error_t rc;

  if (!inp || !user_id)
    return CDK_Inv_Value;
  if (!pktlen)
    return CDK_Inv_Packet;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_user_id: %lu octets\n", (unsigned long)pktlen);

  user_id->len = pktlen;
  rc = stream_read (inp, user_id->name, pktlen, &nread);
  if (rc)
    return rc;
  if (nread != pktlen)
    return CDK_Inv_Packet;
  user_id->name[nread] = '\0';
  return rc;
}


static cdk_error_t
read_subpkt (cdk_stream_t inp, cdk_subpkt_t * r_ctx, size_t * r_nbytes)
{
  byte c, c1;
  size_t size, nread, n;
  cdk_subpkt_t node;
  cdk_error_t rc;

  if (!inp || !r_nbytes)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_subpkt:\n");

  n = 0;
  *r_nbytes = 0;
  c = cdk_stream_getc (inp);
  n++;
  if (c == 255)
    {
      size = read_32 (inp);
      n += 4;
    }
  else if (c >= 192 && c < 255)
    {
      c1 = cdk_stream_getc (inp);
      n++;
      if (c1 == 0)
        return 0;
      size = ((c - 192) << 8) + c1 + 192;
    }
  else if (c < 192)
    size = c;
  else
    return CDK_Inv_Packet;

  node = cdk_subpkt_new (size);
  if (!node)
    return CDK_Out_Of_Core;
  node->size = size;
  node->type = cdk_stream_getc (inp);
  if (DEBUG_PKT)
    _gnutls_write_log (" %d octets %d type\n", node->size, node->type);
  n++;
  node->size--;
  rc = stream_read (inp, node->d, node->size, &nread);
  n += nread;
  if (rc)
    return rc;
  *r_nbytes = n;
  if (!*r_ctx)
    *r_ctx = node;
  else
    cdk_subpkt_add (*r_ctx, node);
  return rc;
}


static cdk_error_t
read_onepass_sig (cdk_stream_t inp, size_t pktlen, cdk_pkt_onepass_sig_t sig)
{
  if (!inp || !sig)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_onepass_sig: %d octets\n", (int) pktlen);

  if (pktlen != 13)
    return CDK_Inv_Packet;
  sig->version = cdk_stream_getc (inp);
  if (sig->version != 3)
    return CDK_Inv_Packet_Ver;
  sig->sig_class = cdk_stream_getc (inp);
  sig->digest_algo = _pgp_hash_algo_to_gnutls (cdk_stream_getc (inp));
  sig->pubkey_algo = _pgp_pub_algo_to_cdk (cdk_stream_getc (inp));
  sig->keyid[0] = read_32 (inp);
  sig->keyid[1] = read_32 (inp);
  sig->last = cdk_stream_getc (inp);
  return 0;
}


static cdk_error_t
parse_sig_subpackets (cdk_pkt_signature_t sig)
{
  cdk_subpkt_t node;

  /* Setup the standard packet entries, so we can use V4
     signatures similar to V3. */
  for (node = sig->unhashed; node; node = node->next)
    {
      if (node->type == CDK_SIGSUBPKT_ISSUER && node->size >= 8)
        {
          sig->keyid[0] = _cdk_buftou32 (node->d);
          sig->keyid[1] = _cdk_buftou32 (node->d + 4);
        }
      else if (node->type == CDK_SIGSUBPKT_EXPORTABLE && node->d[0] == 0)
        {
          /* Sometimes this packet might be placed in the unhashed area */
          sig->flags.exportable = 0;
        }
    }
  for (node = sig->hashed; node; node = node->next)
    {
      if (node->type == CDK_SIGSUBPKT_SIG_CREATED && node->size >= 4)
        sig->timestamp = _cdk_buftou32 (node->d);
      else if (node->type == CDK_SIGSUBPKT_SIG_EXPIRE && node->size >= 4)
        {
          sig->expiredate = _cdk_buftou32 (node->d);
          if (sig->expiredate > 0 && sig->expiredate < (u32) gnutls_time (NULL))
            sig->flags.expired = 1;
        }
      else if (node->type == CDK_SIGSUBPKT_POLICY)
        sig->flags.policy_url = 1;
      else if (node->type == CDK_SIGSUBPKT_NOTATION)
        sig->flags.notation = 1;
      else if (node->type == CDK_SIGSUBPKT_REVOCABLE && node->d[0] == 0)
        sig->flags.revocable = 0;
      else if (node->type == CDK_SIGSUBPKT_EXPORTABLE && node->d[0] == 0)
        sig->flags.exportable = 0;
    }
  if (sig->sig_class == 0x1F)
    {
      cdk_desig_revoker_t r, rnode;

      for (node = sig->hashed; node; node = node->next)
        {
          if (node->type == CDK_SIGSUBPKT_REV_KEY)
            {
              if (node->size < 22)
                continue;
              rnode = cdk_calloc (1, sizeof *rnode);
              if (!rnode)
                return CDK_Out_Of_Core;
              rnode->r_class = node->d[0];
              rnode->algid = node->d[1];
              memcpy (rnode->fpr, node->d + 2, KEY_FPR_LEN);
              if (!sig->revkeys)
                sig->revkeys = rnode;
              else
                {
                  for (r = sig->revkeys; r->next; r = r->next)
                    ;
                  r->next = rnode;
                }
            }
        }
    }

  return 0;
}


static cdk_error_t
read_signature (cdk_stream_t inp, size_t pktlen, cdk_pkt_signature_t sig)
{
  size_t nbytes;
  size_t i, size, nsig;
  cdk_error_t rc;

  if (!inp || !sig)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_signature: %d octets\n", (int) pktlen);

  if (pktlen < 16)
    return CDK_Inv_Packet;
  sig->version = cdk_stream_getc (inp);
  if (sig->version < 2 || sig->version > 4)
    return CDK_Inv_Packet_Ver;

  sig->flags.exportable = 1;
  sig->flags.revocable = 1;

  if (sig->version < 4)
    {
      if (cdk_stream_getc (inp) != 5)
        return CDK_Inv_Packet;
      sig->sig_class = cdk_stream_getc (inp);
      sig->timestamp = read_32 (inp);
      sig->keyid[0] = read_32 (inp);
      sig->keyid[1] = read_32 (inp);
      sig->pubkey_algo = _pgp_pub_algo_to_cdk (cdk_stream_getc (inp));
      sig->digest_algo = _pgp_hash_algo_to_gnutls (cdk_stream_getc (inp));
      sig->digest_start[0] = cdk_stream_getc (inp);
      sig->digest_start[1] = cdk_stream_getc (inp);
      nsig = cdk_pk_get_nsig (sig->pubkey_algo);
      if (!nsig)
        return CDK_Inv_Algo;
      for (i = 0; i < nsig; i++)
        {
          rc = read_mpi (inp, &sig->mpi[i], 0);
          if (rc)
            return rc;
        }
    }
  else
    {
      sig->sig_class = cdk_stream_getc (inp);
      sig->pubkey_algo = _pgp_pub_algo_to_cdk (cdk_stream_getc (inp));
      sig->digest_algo = _pgp_hash_algo_to_gnutls (cdk_stream_getc (inp));
      sig->hashed_size = read_16 (inp);
      size = sig->hashed_size;
      sig->hashed = NULL;
      while (size > 0)
        {
          rc = read_subpkt (inp, &sig->hashed, &nbytes);
          if (rc)
            return rc;
          size -= nbytes;
        }
      sig->unhashed_size = read_16 (inp);
      size = sig->unhashed_size;
      sig->unhashed = NULL;
      while (size > 0)
        {
          rc = read_subpkt (inp, &sig->unhashed, &nbytes);
          if (rc)
            return rc;
          size -= nbytes;
        }

      rc = parse_sig_subpackets (sig);
      if (rc)
        return rc;

      sig->digest_start[0] = cdk_stream_getc (inp);
      sig->digest_start[1] = cdk_stream_getc (inp);
      nsig = cdk_pk_get_nsig (sig->pubkey_algo);
      if (!nsig)
        return CDK_Inv_Algo;
      for (i = 0; i < nsig; i++)
        {
          rc = read_mpi (inp, &sig->mpi[i], 0);
          if (rc)
            return rc;
        }
    }

  return 0;
}


static cdk_error_t
read_literal (cdk_stream_t inp, size_t pktlen,
              cdk_pkt_literal_t * ret_pt, int is_partial)
{
  cdk_pkt_literal_t pt = *ret_pt;
  size_t nread;
  cdk_error_t rc;

  if (!inp || !pt)
    return CDK_Inv_Value;

  if (DEBUG_PKT)
    _gnutls_write_log ("read_literal: %d octets\n", (int) pktlen);

  pt->mode = cdk_stream_getc (inp);
  if (pt->mode != 0x62 && pt->mode != 0x74 && pt->mode != 0x75)
    return CDK_Inv_Packet;
  if (cdk_stream_eof (inp))
    return CDK_Inv_Packet;

  pt->namelen = cdk_stream_getc (inp);
  if (pt->namelen > 0)
    {
      *ret_pt = pt = cdk_realloc (pt, sizeof *pt + pt->namelen + 2);
      if (!pt)
        return CDK_Out_Of_Core;
      pt->name = (char *) pt + sizeof (*pt);
      rc = stream_read (inp, pt->name, pt->namelen, &nread);
      if (rc)
        return rc;
      if ((int) nread != pt->namelen)
        return CDK_Inv_Packet;
      pt->name[pt->namelen] = '\0';
    }
  pt->timestamp = read_32 (inp);
  pktlen = pktlen - 6 - pt->namelen;
  if (is_partial)
    _cdk_stream_set_blockmode (inp, pktlen);
  pt->buf = inp;
  pt->len = pktlen;
  return 0;
}


/* Read an old packet CTB and return the length of the body. */
static void
read_old_length (cdk_stream_t inp, int ctb, size_t * r_len, size_t * r_size)
{
  int llen = ctb & 0x03;

  if (llen == 0)
    {
      *r_len = cdk_stream_getc (inp);
      (*r_size)++;
    }
  else if (llen == 1)
    {
      *r_len = read_16 (inp);
      (*r_size) += 2;
    }
  else if (llen == 2)
    {
      *r_len = read_32 (inp);
      (*r_size) += 4;
    }
  else
    {
      *r_len = 0;
      *r_size = 0;
    }
}


/* Read a new CTB and decode the body length. */
static void
read_new_length (cdk_stream_t inp,
                 size_t * r_len, size_t * r_size, size_t * r_partial)
{
  int c, c1;

  c = cdk_stream_getc (inp);
  (*r_size)++;
  if (c < 192)
    *r_len = c;
  else if (c >= 192 && c <= 223)
    {
      c1 = cdk_stream_getc (inp);
      (*r_size)++;
      *r_len = ((c - 192) << 8) + c1 + 192;
    }
  else if (c == 255)
    {
      *r_len = read_32 (inp);
      (*r_size) += 4;
    }
  else
    {
      *r_len = 1 << (c & 0x1f);
      *r_partial = 1;
    }
}


/* Skip the current packet body. */
static void
skip_packet (cdk_stream_t inp, size_t pktlen)
{
  byte buf[BUFSIZE];
  size_t nread, buflen = DIM (buf);

  while (pktlen > 0)
    {
      stream_read (inp, buf, pktlen > buflen ? buflen : pktlen, &nread);
      pktlen -= nread;
    }

  assert (pktlen == 0);
}


/**
 * cdk_pkt_read:
 * @inp: the input stream
 * @pkt: allocated packet handle to store the packet
 *
 * Parse the next packet on the @inp stream and return its contents in @pkt.
 **/
cdk_error_t
cdk_pkt_read (cdk_stream_t inp, cdk_packet_t pkt)
{
  int ctb, is_newctb;
  int pkttype;
  size_t pktlen = 0, pktsize = 0, is_partial = 0;
  cdk_error_t rc;

  if (!inp || !pkt)
    return CDK_Inv_Value;

  ctb = cdk_stream_getc (inp);
  if (cdk_stream_eof (inp) || ctb == EOF)
    return CDK_EOF;
  else if (!ctb)
    return CDK_Inv_Packet;

  pktsize++;
  if (!(ctb & 0x80))
    {
      _cdk_log_info ("cdk_pkt_read: no openpgp data found. "
                     "(ctb=%02X; fpos=%02X)\n", (int) ctb,
                     (int) cdk_stream_tell (inp));
      return CDK_Inv_Packet;
    }

  if (ctb & 0x40)               /* RFC2440 packet format. */
    {
      pkttype = ctb & 0x3f;
      is_newctb = 1;
    }
  else                          /* the old RFC1991 packet format. */
    {
      pkttype = ctb & 0x3f;
      pkttype >>= 2;
      is_newctb = 0;
    }

  if (pkttype > 63)
    {
      _cdk_log_info ("cdk_pkt_read: unknown type %d\n", pkttype);
      return CDK_Inv_Packet;
    }

  if (is_newctb)
    read_new_length (inp, &pktlen, &pktsize, &is_partial);
  else
    read_old_length (inp, ctb, &pktlen, &pktsize);

  pkt->pkttype = pkttype;
  pkt->pktlen = pktlen;
  pkt->pktsize = pktsize + pktlen;
  pkt->old_ctb = is_newctb ? 0 : 1;

  rc = 0;
  switch (pkt->pkttype)
    {
    case CDK_PKT_ATTRIBUTE:
#define NAME_SIZE (pkt->pktlen + 16 + 1)
      pkt->pkt.user_id = cdk_calloc (1, sizeof *pkt->pkt.user_id
                                     + NAME_SIZE);
      if (!pkt->pkt.user_id)
        return CDK_Out_Of_Core;
      pkt->pkt.user_id->name =
        (char *) pkt->pkt.user_id + sizeof (*pkt->pkt.user_id);

      rc = read_attribute (inp, pktlen, pkt->pkt.user_id, NAME_SIZE);
      pkt->pkttype = CDK_PKT_ATTRIBUTE;
      break;

    case CDK_PKT_USER_ID:
      pkt->pkt.user_id = cdk_calloc (1, sizeof *pkt->pkt.user_id
                                     + pkt->pktlen + 1);
      if (!pkt->pkt.user_id)
        return CDK_Out_Of_Core;
      pkt->pkt.user_id->name =
        (char *) pkt->pkt.user_id + sizeof (*pkt->pkt.user_id);
      rc = read_user_id (inp, pktlen, pkt->pkt.user_id);
      break;

    case CDK_PKT_PUBLIC_KEY:
      pkt->pkt.public_key = cdk_calloc (1, sizeof *pkt->pkt.public_key);
      if (!pkt->pkt.public_key)
        return CDK_Out_Of_Core;
      rc = read_public_key (inp, pktlen, pkt->pkt.public_key);
      break;

    case CDK_PKT_PUBLIC_SUBKEY:
      pkt->pkt.public_key = cdk_calloc (1, sizeof *pkt->pkt.public_key);
      if (!pkt->pkt.public_key)
        return CDK_Out_Of_Core;
      rc = read_public_subkey (inp, pktlen, pkt->pkt.public_key);
      break;

    case CDK_PKT_SECRET_KEY:
      pkt->pkt.secret_key = cdk_calloc (1, sizeof *pkt->pkt.secret_key);
      if (!pkt->pkt.secret_key)
        return CDK_Out_Of_Core;
      pkt->pkt.secret_key->pk = cdk_calloc (1,
                                            sizeof *pkt->pkt.secret_key->pk);
      if (!pkt->pkt.secret_key->pk)
        return CDK_Out_Of_Core;
      rc = read_secret_key (inp, pktlen, pkt->pkt.secret_key);
      break;

    case CDK_PKT_SECRET_SUBKEY:
      pkt->pkt.secret_key = cdk_calloc (1, sizeof *pkt->pkt.secret_key);
      if (!pkt->pkt.secret_key)
        return CDK_Out_Of_Core;
      pkt->pkt.secret_key->pk = cdk_calloc (1,
                                            sizeof *pkt->pkt.secret_key->pk);
      if (!pkt->pkt.secret_key->pk)
        return CDK_Out_Of_Core;
      rc = read_secret_subkey (inp, pktlen, pkt->pkt.secret_key);
      break;

    case CDK_PKT_LITERAL:
      pkt->pkt.literal = cdk_calloc (1, sizeof *pkt->pkt.literal);
      if (!pkt->pkt.literal)
        return CDK_Out_Of_Core;
      rc = read_literal (inp, pktlen, &pkt->pkt.literal, is_partial);
      break;

    case CDK_PKT_ONEPASS_SIG:
      pkt->pkt.onepass_sig = cdk_calloc (1, sizeof *pkt->pkt.onepass_sig);
      if (!pkt->pkt.onepass_sig)
        return CDK_Out_Of_Core;
      rc = read_onepass_sig (inp, pktlen, pkt->pkt.onepass_sig);
      break;

    case CDK_PKT_SIGNATURE:
      pkt->pkt.signature = cdk_calloc (1, sizeof *pkt->pkt.signature);
      if (!pkt->pkt.signature)
        return CDK_Out_Of_Core;
      rc = read_signature (inp, pktlen, pkt->pkt.signature);
      break;

    case CDK_PKT_PUBKEY_ENC:
      pkt->pkt.pubkey_enc = cdk_calloc (1, sizeof *pkt->pkt.pubkey_enc);
      if (!pkt->pkt.pubkey_enc)
        return CDK_Out_Of_Core;
      rc = read_pubkey_enc (inp, pktlen, pkt->pkt.pubkey_enc);
      break;

    case CDK_PKT_COMPRESSED:
      pkt->pkt.compressed = cdk_calloc (1, sizeof *pkt->pkt.compressed);
      if (!pkt->pkt.compressed)
        return CDK_Out_Of_Core;
      rc = read_compressed (inp, pktlen, pkt->pkt.compressed);
      break;

    case CDK_PKT_MDC:
      pkt->pkt.mdc = cdk_calloc (1, sizeof *pkt->pkt.mdc);
      if (!pkt->pkt.mdc)
        return CDK_Out_Of_Core;
      rc = read_mdc (inp, pkt->pkt.mdc);
      break;

    default:
      /* Skip all packets we don't understand */
      skip_packet (inp, pktlen);
      break;
    }

  return rc;
}