gnupg/agent/minip12.c

/* minip12.c - A minilam pkcs-12 implementation.
 *	Copyright (C) 2002 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <gcrypt.h>

#undef TEST 

#ifdef TEST
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#endif

#include "../jnlib/logging.h"
#include "minip12.h"

#ifndef DIM
#define DIM(v)		     (sizeof(v)/sizeof((v)[0]))
#endif

enum
{
  UNIVERSAL = 0,
  APPLICATION = 1,
  CONTEXT = 2,
  PRIVATE = 3
};


enum
{
  TAG_NONE = 0,
  TAG_BOOLEAN = 1,
  TAG_INTEGER = 2,
  TAG_BIT_STRING = 3,
  TAG_OCTET_STRING = 4,
  TAG_NULL = 5,
  TAG_OBJECT_ID = 6,
  TAG_OBJECT_DESCRIPTOR = 7,
  TAG_EXTERNAL = 8,
  TAG_REAL = 9,
  TAG_ENUMERATED = 10,
  TAG_EMBEDDED_PDV = 11,
  TAG_UTF8_STRING = 12,
  TAG_REALTIVE_OID = 13,
  TAG_SEQUENCE = 16,
  TAG_SET = 17,
  TAG_NUMERIC_STRING = 18,
  TAG_PRINTABLE_STRING = 19,
  TAG_TELETEX_STRING = 20,
  TAG_VIDEOTEX_STRING = 21,
  TAG_IA5_STRING = 22,
  TAG_UTC_TIME = 23,
  TAG_GENERALIZED_TIME = 24,
  TAG_GRAPHIC_STRING = 25,
  TAG_VISIBLE_STRING = 26,
  TAG_GENERAL_STRING = 27,
  TAG_UNIVERSAL_STRING = 28,
  TAG_CHARACTER_STRING = 29,
  TAG_BMP_STRING = 30
};


static unsigned char const oid_data[9] = {
  0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x01 };
static unsigned char const oid_encryptedData[9] = {
  0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x06 };
static unsigned char const oid_pkcs_12_pkcs_8ShroudedKeyBag[11] = {
  0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x0C, 0x0A, 0x01, 0x02 };
static unsigned char const oid_pbeWithSHAAnd3_KeyTripleDES_CBC[10] = {
  0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x0C, 0x01, 0x03 };

static unsigned char const oid_rsaEncryption[9] = {
  0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01 };


static unsigned char const data_3desiter1024[30] = {
  0x30, 0x1C, 0x06, 0x0A, 0x2A, 0x86, 0x48, 0x86,
  0xF7, 0x0D, 0x01, 0x0C, 0x01, 0x03, 0x30, 0x0E, 
  0x04, 0x08, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0x02, 0x02, 0x04, 0x00 };
#define DATA_3DESITER1024_SALT_OFF  18


struct buffer_s 
{
  unsigned char *buffer;
  size_t length;
};  


struct tag_info 
{
  int class;
  int is_constructed;
  unsigned long tag;
  unsigned long length;  /* length part of the TLV */
  int nhdr;
  int ndef;              /* It is an indefinite length */
};


/* Parse the buffer at the address BUFFER which is of SIZE and return
   the tag and the length part from the TLV triplet.  Update BUFFER
   and SIZE on success. */
static int 
parse_tag (unsigned char const **buffer, size_t *size, struct tag_info *ti)
{
  int c;
  unsigned long tag;
  const unsigned char *buf = *buffer;
  size_t length = *size;

  ti->length = 0;
  ti->ndef = 0;
  ti->nhdr = 0;

  /* Get the tag */
  if (!length)
    return -1; /* premature eof */
  c = *buf++; length--;
  ti->nhdr++;

  ti->class = (c & 0xc0) >> 6;
  ti->is_constructed = !!(c & 0x20);
  tag = c & 0x1f;

  if (tag == 0x1f)
    {
      tag = 0;
      do
        {
          tag <<= 7;
          if (!length)
            return -1; /* premature eof */
          c = *buf++; length--;
          ti->nhdr++;
          tag |= c & 0x7f;
        }
      while (c & 0x80);
    }
  ti->tag = tag;

  /* Get the length */
  if (!length)
    return -1; /* prematureeof */
  c = *buf++; length--;
  ti->nhdr++;

  if ( !(c & 0x80) )
    ti->length = c;
  else if (c == 0x80)
    ti->ndef = 1;
  else if (c == 0xff)
    return -1; /* forbidden length value */
  else
    {
      unsigned long len = 0;
      int count = c & 0x7f;

      for (; count; count--)
        {
          len <<= 8;
          if (!length)
            return -1; /* premature_eof */
          c = *buf++; length--;
          ti->nhdr++;
          len |= c & 0xff;
        }
      ti->length = len;
    }
  
  if (ti->class == UNIVERSAL && !ti->tag)
    ti->length = 0;

  if (ti->length > length)
    return -1; /* data larger than buffer. */
  
  *buffer = buf;
  *size = length;
  return 0;
}


static int 
string_to_key (int id, char *salt, int iter, const char *pw,
               int req_keylen, unsigned char *keybuf)
{
  int rc, i, j;
  GcryMDHd md;
  GcryMPI num_b1 = NULL;
  int pwlen;
  unsigned char hash[20], buf_b[64], buf_i[128], *p;
  size_t cur_keylen;
  size_t n;

  cur_keylen = 0;
  pwlen = strlen (pw);
  if (pwlen > 63/2)
    {
      log_error ("password too long\n");
      return -1;
    }

  /* Store salt and password in BUF_I */
  p = buf_i;
  for(i=0; i < 64; i++)
    *p++ = salt [i%8];
  for(i=j=0; i < 64; i += 2)
    {
      *p++ = 0;
      *p++ = pw[j];
      if (++j > pwlen) /* Note, that we include the trailing zero */
        j = 0;
    }

  for (;;)
    {
      md = gcry_md_open (GCRY_MD_SHA1, 0);
      if (!md)
        {
          log_error ( "gcry_md_open failed: %s\n", gcry_strerror (-1));
          return -1;
        }
      for(i=0; i < 64; i++)
        gcry_md_putc (md, id);
      gcry_md_write (md, buf_i, 128);
      memcpy (hash, gcry_md_read (md, 0), 20);
      gcry_md_close (md);
      for (i=1; i < iter; i++)
        gcry_md_hash_buffer (GCRY_MD_SHA1, hash, hash, 20);

      for (i=0; i < 20 && cur_keylen < req_keylen; i++)
        keybuf[cur_keylen++] = hash[i];
      if (cur_keylen == req_keylen)
        {
          gcry_mpi_release (num_b1);
          return 0; /* ready */
        }
      
      /* need more bytes. */
      for(i=0; i < 64; i++)
        buf_b[i] = hash[i % 20];
      n = 64;
      rc = gcry_mpi_scan (&num_b1, GCRYMPI_FMT_USG, buf_b, &n);
      if (rc)
        {
          log_error ( "gcry_mpi_scan failed: %s\n", gcry_strerror (rc));
          return -1;
        }
      gcry_mpi_add_ui (num_b1, num_b1, 1);
      for (i=0; i < 128; i += 64)
        {
          GcryMPI num_ij;

          n = 64;
          rc = gcry_mpi_scan (&num_ij, GCRYMPI_FMT_USG, buf_i + i, &n);
          if (rc)
            {
              log_error ( "gcry_mpi_scan failed: %s\n",
                       gcry_strerror (rc));
              return -1;
            }
          gcry_mpi_add (num_ij, num_ij, num_b1);
          gcry_mpi_clear_highbit (num_ij, 64*8);
          n = 64;
          rc = gcry_mpi_print (GCRYMPI_FMT_USG, buf_i + i, &n, num_ij);
          if (rc)
            {
              log_error ( "gcry_mpi_print failed: %s\n",
                       gcry_strerror (rc));
              return -1;
            }
          gcry_mpi_release (num_ij);
        }
    }
}


static int 
set_key_iv (GcryCipherHd chd, char *salt, int iter, const char *pw)
{
  unsigned char keybuf[24];
  int rc;

  if (string_to_key (1, salt, iter, pw, 24, keybuf))
    return -1;
  rc = gcry_cipher_setkey (chd, keybuf, 24);
  if (rc)
    {
      log_error ( "gcry_cipher_setkey failed: %s\n", gcry_strerror (rc));
      return -1;
    }

  if (string_to_key (2, salt, iter, pw, 8, keybuf))
    return -1;
  rc = gcry_cipher_setiv (chd, keybuf, 8);
  if (rc)
    {
      log_error ("gcry_cipher_setiv failed: %s\n", gcry_strerror (rc));
      return -1;
    }
  return 0;
}


static void
crypt_block (unsigned char *buffer, size_t length, char *salt, int iter,
             const char *pw, int encrypt)
{
  GcryCipherHd chd;
  int rc;

  chd = gcry_cipher_open (GCRY_CIPHER_3DES, GCRY_CIPHER_MODE_CBC, 0);
  if (!chd)
    {
      log_error ( "gcry_cipher_open failed: %s\n", gcry_strerror(-1));
      return;
    }
  if (set_key_iv (chd, salt, iter, pw))
    goto leave;

  rc = encrypt? gcry_cipher_encrypt (chd, buffer, length, NULL, 0)
              : gcry_cipher_decrypt (chd, buffer, length, NULL, 0);

  if (rc)
    {
      log_error ( "en/de-crytion failed: %s\n", gcry_strerror (rc));
      goto leave;
    }

/*    { */
/*      FILE *fp = fopen("inner.der", "wb"); */
/*      fwrite (buffer, 1, length, fp); */
/*      fclose (fp); */
/*    } */

 leave:
  gcry_cipher_close (chd);
}
  



static int
parse_bag_encrypted_data (const unsigned char *buffer, size_t length,
                          int startoffset)
{
  struct tag_info ti;
  const unsigned char *p = buffer;
  size_t n = length;
  const char *where;

  where = "start";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != CONTEXT || ti.tag)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_SEQUENCE)
    goto bailout;

  where = "bag.encryptedData.version";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_INTEGER || ti.length != 1 || *p != 0)
    goto bailout;
  p++; n--;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_SEQUENCE)
    goto bailout;

  where = "bag.encryptedData.data";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_OBJECT_ID || ti.length != DIM(oid_data)
      || memcmp (p, oid_data, DIM(oid_data)))
    goto bailout;
  p += DIM(oid_data);
  n -= DIM(oid_data);

  /* fixme: continue parsing */

  return 0;
 bailout:
  log_error ("encrptedData error at \"%s\", offset %u\n",
             where, (p - buffer)+startoffset);
  return -1;
}

static GcryMPI *
parse_bag_data (const unsigned char *buffer, size_t length, int startoffset,
                const char *pw)
{
  int rc;
  struct tag_info ti;
  const unsigned char *p = buffer;
  size_t n = length;
  const char *where;
  char salt[8];
  unsigned int iter;
  int len;
  unsigned char *plain = NULL;
  GcryMPI *result = NULL;
  int result_count, i;

  where = "start";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != CONTEXT || ti.tag)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_OCTET_STRING)
    goto bailout;

  where = "data.outerseqs";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;

  where = "data.objectidentifier";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_OBJECT_ID
      || ti.length != DIM(oid_pkcs_12_pkcs_8ShroudedKeyBag)
      || memcmp (p, oid_pkcs_12_pkcs_8ShroudedKeyBag,
                 DIM(oid_pkcs_12_pkcs_8ShroudedKeyBag)))
    goto bailout;
  p += DIM(oid_pkcs_12_pkcs_8ShroudedKeyBag);
  n -= DIM(oid_pkcs_12_pkcs_8ShroudedKeyBag);

  where = "shrouded,outerseqs";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != CONTEXT || ti.tag)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_OBJECT_ID
      || ti.length != DIM(oid_pbeWithSHAAnd3_KeyTripleDES_CBC)
      || memcmp (p, oid_pbeWithSHAAnd3_KeyTripleDES_CBC,
                 DIM(oid_pbeWithSHAAnd3_KeyTripleDES_CBC)))
    goto bailout;
  p += DIM(oid_pbeWithSHAAnd3_KeyTripleDES_CBC);
  n -= DIM(oid_pbeWithSHAAnd3_KeyTripleDES_CBC);

  where = "3des-params";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_OCTET_STRING || ti.length != 8 )
    goto bailout;
  memcpy (salt, p, 8);
  p += 8;
  n -= 8;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_INTEGER || !ti.length )
    goto bailout;
  for (iter=0; ti.length; ti.length--)
    {
      iter <<= 8;
      iter |= (*p++) & 0xff; 
      n--;
    }
  
  where = "3des-ciphertext";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class || ti.tag != TAG_OCTET_STRING || !ti.length )
    goto bailout;
  
  log_info ("%lu bytes of 3DES encrypted text\n", ti.length);
  
  plain = gcry_malloc_secure (ti.length);
  if (!plain)
    {
      log_error ("error allocating decryption buffer\n");
      goto bailout;
    }
  memcpy (plain, p, ti.length);
  crypt_block (plain, ti.length, salt, iter, pw, 0);
  n = ti.length;
  startoffset = 0;
  buffer = p = plain;

  where = "decrypted-text";
  if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_INTEGER
      || ti.length != 1 || *p)
    goto bailout;
  p++; n--;
  if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  len = ti.length;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (len < ti.nhdr)
    goto bailout;
  len -= ti.nhdr;
  if (ti.class || ti.tag != TAG_OBJECT_ID
      || ti.length != DIM(oid_rsaEncryption)
      || memcmp (p, oid_rsaEncryption,
                 DIM(oid_rsaEncryption)))
    goto bailout;
  p += DIM (oid_rsaEncryption);
  n -= DIM (oid_rsaEncryption);
  if (len < ti.length)
    goto bailout;
  len -= ti.length;
  if (n < len)
    goto bailout;
  p += len;
  n -= len;
  if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_OCTET_STRING)
    goto bailout;
  if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_SEQUENCE)
    goto bailout;
  len = ti.length;

  result = gcry_calloc (10, sizeof *result);
  if (!result)
    {
      log_error ( "error allocating result array\n");
      goto bailout;
    }
  result_count = 0;

  where = "reading.key-parameters";
  for (result_count=0; len && result_count < 9;)
    {
      int dummy_n;

      if (parse_tag (&p, &n, &ti) || ti.class || ti.tag != TAG_INTEGER)
        goto bailout;
      if (len < ti.nhdr)
        goto bailout;
      len -= ti.nhdr;
      if (len < ti.length)
        goto bailout;
      len -= ti.length;
      dummy_n = ti.length;
      if (!result_count && ti.length == 1 && !*p)
        ; /* ignore the very first one if it is a 0 */
      else 
        {
          rc = gcry_mpi_scan (result+result_count, GCRYMPI_FMT_USG, p,
                              &dummy_n);
          if (rc)
            {
              log_error ("error parsing key parameter: %s\n",
                         gcry_strerror (rc));
              goto bailout;
            }
          result_count++;
        }
      p += ti.length;
      n -= ti.length;
    }
  if (len)
    goto bailout;

  return result;

 bailout:
  gcry_free (plain);
  if (result)
    {
      for (i=0; result[i]; i++)
        gcry_mpi_release (result[i]);
      gcry_free (result);
    }
  log_error ( "data error at \"%s\", offset %u\n",
              where, (p - buffer) + startoffset);
  return NULL;
}


/* Parse a PKCS12 object and return an array of MPI representing the
   secret key parameters.  This is a very limited inplementation in
   that it is only able to look for 3DES encoded enctyptedData and
   tries to extract the first private key object it finds.  In case of
   an error NULL is returned. */
GcryMPI *
p12_parse (const unsigned char *buffer, size_t length, const char *pw)
{
  struct tag_info ti;
  const unsigned char *p = buffer;
  size_t n = length;
  const char *where;
  int bagseqlength, len;

  where = "pfx";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_SEQUENCE)
    goto bailout;

  where = "pfxVersion";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_INTEGER || ti.length != 1 || *p != 3)
    goto bailout;
  p++; n--;
  
  where = "authSave";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_SEQUENCE)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.tag != TAG_OBJECT_ID || ti.length != DIM(oid_data)
      || memcmp (p, oid_data, DIM(oid_data)))
    goto bailout;
  p += DIM(oid_data);
  n -= DIM(oid_data);

  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != CONTEXT || ti.tag)
    goto bailout;
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != UNIVERSAL || ti.tag != TAG_OCTET_STRING)
    goto bailout;

  where = "bags";
  if (parse_tag (&p, &n, &ti))
    goto bailout;
  if (ti.class != UNIVERSAL || ti.tag != TAG_SEQUENCE)
    goto bailout;
  bagseqlength = ti.length;
  while (bagseqlength)
    {
      /*log_debug ( "at offset %u\n", (p - buffer));*/
      where = "bag-sequence";
      if (parse_tag (&p, &n, &ti))
        goto bailout;
      if (ti.class != UNIVERSAL || ti.tag != TAG_SEQUENCE)
        goto bailout;

      if (bagseqlength < ti.nhdr)
        goto bailout;
      bagseqlength -= ti.nhdr;
      if (bagseqlength < ti.length)
        goto bailout;
      bagseqlength -= ti.length;
      len = ti.length;

      if (parse_tag (&p, &n, &ti))
        goto bailout;
      len -= ti.nhdr;
      if (ti.tag == TAG_OBJECT_ID && ti.length == DIM(oid_encryptedData)
          && !memcmp (p, oid_encryptedData, DIM(oid_encryptedData)))
        {
          p += DIM(oid_encryptedData);
          n -= DIM(oid_encryptedData);
          len -= DIM(oid_encryptedData);
          where = "bag.encryptedData";
          if (parse_bag_encrypted_data (p, n, (p - buffer)))
            goto bailout;
        }
      else if (ti.tag == TAG_OBJECT_ID && ti.length == DIM(oid_data)
          && !memcmp (p, oid_data, DIM(oid_data)))
        {
          p += DIM(oid_data);
          n -= DIM(oid_data);
          len -= DIM(oid_data);
          return parse_bag_data (p, n, (p-buffer), pw);
        }
      else
        log_info ( "unknown bag type - skipped\n");

      if (len < 0 || len > n)
        goto bailout;
      p += len;
      n -= len;
    }
  
  return NULL;
 bailout:
  log_error ("error at \"%s\", offset %u\n", where, (p - buffer));
  return NULL;
}



static size_t
compute_tag_length (size_t n)
{     
  int needed = 0;

  if (n < 128)
    needed += 2; /* tag and one length byte */
  else if (n < 256)
    needed += 3; /* tag, number of length bytes, 1 length byte */
  else if (n < 65536)
    needed += 4; /* tag, number of length bytes, 2 length bytes */
  else
    {
      log_error ("object too larger to encode\n");
      return 0;
    }
  return needed;
}

static unsigned char *
store_tag_length (unsigned char *p, int tag, size_t n)
{     
  if (tag == TAG_SEQUENCE)
    tag |= 0x20; /* constructed */

  *p++ = tag;
  if (n < 128)
    *p++ = n;
  else if (n < 256)
    {
      *p++ = 0x81;
      *p++ = n;
    }
  else if (n < 65536)
    {
      *p++ = 0x82;
      *p++ = n >> 8;
      *p++ = n;
    }

  return p;
}


/* Create the final PKCS-12 object from the sequences contained in
   SEQLIST.  That array is terminated with an NULL object */
static unsigned char *
create_final (struct buffer_s *sequences, size_t *r_length)
{
  int i;
  size_t needed = 0;
  size_t n, outseqlen, notsooutseqlen, out0taglen, octstrlen, inseqlen;
  unsigned char *result, *p;
  size_t resultlen;

  for (i=0; sequences[i].buffer; i++)
    needed += sequences[i].length;
  /* This goes into a sequences. */
  inseqlen = needed;
  n = compute_tag_length (needed);
  needed += n;
  /* And encapsulate all in an octet string. */
  octstrlen = needed;
  n = compute_tag_length (needed);
  needed += n;
  /* And tag it with [0]. */
  out0taglen = needed;
  n = compute_tag_length (needed);
  needed += n;
  /* Prepend an data OID. */
  needed += 2 + DIM (oid_data);
  /* This all into a sequences. */
  notsooutseqlen = needed;
  n = compute_tag_length (needed);
  needed += n;
  /* Prepend the version integer 3. */
  needed += 3;
  /* And the final sequence. */
  outseqlen = needed;
  n = compute_tag_length (needed);
  needed += n;

  result = gcry_malloc (needed);
  if (!result)
    {
      log_error ("error allocating buffer\n");
      return NULL;
    }
  p = result;

  /* Store the very outer sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, outseqlen);
  /* Store the version integer 3. */
  *p++ = TAG_INTEGER;
  *p++ = 1; 
  *p++ = 3; 
  /* Store another sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, notsooutseqlen);
  /* Store the data OID. */
  p = store_tag_length (p, TAG_OBJECT_ID, DIM (oid_data));
  memcpy (p, oid_data, DIM (oid_data)); 
  p += DIM (oid_data); 
  /* Next comes a context tag. */
  p = store_tag_length (p, 0xa0, out0taglen);
  /* And an octet string. */
  p = store_tag_length (p, TAG_OCTET_STRING, octstrlen);
  /* And the inner sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, inseqlen);
  /* And append all the buffers. */
  for (i=0; sequences[i].buffer; i++)
    {
      memcpy (p, sequences[i].buffer, sequences[i].length);
      p += sequences[i].length;
    }

  /* Ready. */
  resultlen = p - result;
  if (needed != resultlen)
    log_debug ("length mismatch: %u, %u\n", needed, resultlen);

  *r_length = resultlen;
  return result;
}


/* Expect the RSA key parameters in KPARMS and a password in
   PW. Create a PKCS structure from it and return it as well as the
   length in R_LENGTH; return NULL in case of an error. */
unsigned char * 
p12_build (GcryMPI *kparms, const char *pw, size_t *r_length)
{
  int rc, i;
  size_t needed, n;
  unsigned char *plain, *p, *cipher;
  size_t plainlen, cipherlen;
  size_t outseqlen, oidseqlen, octstrlen, inseqlen;
  size_t out0taglen, in0taglen, outoctstrlen;
  size_t aseq1len, aseq2len, aseq3len;
  char salt[8];

  needed = 3; /* The version(?) integer of value 0. */
  for (i=0; kparms[i]; i++)
    {
      n = 0;
      rc = gcry_mpi_print (GCRYMPI_FMT_STD, NULL, &n, kparms[i]);
      if (rc)
        {
          log_error ("error formatting parameter: %s\n", gcry_strerror (rc));
          return NULL;
        }
      needed += n;
      n = compute_tag_length (n);
      if (!n)
        return NULL;
      needed += n;
    }
  if (i != 8)
    {
      log_error ("invalid paramters for p12_build\n");
      return NULL;
    }
  /* Now this all goes into a sequence. */
  inseqlen = needed;
  n = compute_tag_length (needed);
  if (!n)
    return NULL;
  needed += n;
  /* Encapsulate all into an octet string. */
  octstrlen = needed;
  n = compute_tag_length (needed);
  if (!n)
    return NULL;
  needed += n;
  /* Prepend the object identifier sequence. */
  oidseqlen = 2 + DIM (oid_rsaEncryption) + 2;
  needed += 2 + oidseqlen;
  /* The version number. */
  needed += 3;
  /* And finally put the whole thing into a sequence. */
  outseqlen = needed;
  n = compute_tag_length (needed);
  if (!n)
    return NULL;
  needed += n;
  
  /* allocate 8 extra bytes for padding */
  plain = gcry_malloc_secure (needed+8);
  if (!plain)
    {
      log_error ("error allocating encryption buffer\n");
      return NULL;
    }
  
  /* And now fill the plaintext buffer. */
  p = plain;
  p = store_tag_length (p, TAG_SEQUENCE, outseqlen);
  /* Store version. */
  *p++ = TAG_INTEGER;
  *p++ = 1;
  *p++ = 0;
  /* Store object identifier sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, oidseqlen);
  p = store_tag_length (p, TAG_OBJECT_ID, DIM (oid_rsaEncryption));
  memcpy (p, oid_rsaEncryption, DIM (oid_rsaEncryption)); 
  p += DIM (oid_rsaEncryption); 
  *p++ = TAG_NULL;
  *p++ = 0;
  /* Start with the octet string. */
  p = store_tag_length (p, TAG_OCTET_STRING, octstrlen);
  p = store_tag_length (p, TAG_SEQUENCE, inseqlen);
  /* Store the key parameters. */
  *p++ = TAG_INTEGER;
  *p++ = 1;
  *p++ = 0;
  for (i=0; kparms[i]; i++)
    {
      n = 0;
      rc = gcry_mpi_print (GCRYMPI_FMT_STD, NULL, &n, kparms[i]);
      if (rc)
        {
          log_error ("oops: error formatting parameter: %s\n",
                     gcry_strerror (rc));
          gcry_free (plain);
          return NULL;
        }
      p = store_tag_length (p, TAG_INTEGER, n);
      
      n = plain + needed - p;
      rc = gcry_mpi_print (GCRYMPI_FMT_STD, p, &n, kparms[i]);
      if (rc)
        {
          log_error ("oops: error storing parameter: %s\n",
                     gcry_strerror (rc));
          gcry_free (plain);
          return NULL;
        }
      p += n;
    }

  plainlen = p - plain;
  assert (needed == plainlen);
  /* Append some pad characters; we already allocated extra space. */
  n = 8 - plainlen % 8;
  for (;(plainlen % 8); plainlen++)
    *p++ = n;

  {
    FILE *fp = fopen("inner-out.der", "wb");
    fwrite (plain, 1, plainlen, fp);
    fclose (fp);
  }


  /* Encrypt it and prepend a lot of stupid things. */
  gcry_randomize (salt, 8, GCRY_STRONG_RANDOM);
  crypt_block (plain, plainlen, salt, 1024, pw, 1);
  /* the data goes into an octet string. */
  needed = compute_tag_length (plainlen);
  needed += plainlen;
  /* we prepend the the algorithm identifier (we use a pre-encoded one)*/
  needed += DIM (data_3desiter1024);
  /* we put a sequence around. */
  aseq3len = needed;
  needed += compute_tag_length (needed);
  /* Prepend it with a [0] tag. */
  in0taglen = needed;
  needed += compute_tag_length (needed);
  /* Prepend that shroudedKeyBag OID. */
  needed += 2 + DIM (oid_pkcs_12_pkcs_8ShroudedKeyBag);
  /* Put it all into two sequence. */
  aseq2len = needed;
  needed += compute_tag_length ( needed);
  aseq1len = needed;
  needed += compute_tag_length (needed);
  /* This all goes into an octet string. */
  outoctstrlen = needed;
  needed += compute_tag_length (needed);
  /* Prepend it with a [0] tag. */
  out0taglen = needed;
  needed += compute_tag_length (needed);
  /* Prepend the data OID. */
  needed += 2 + DIM (oid_data);
  /* And a sequence. */
  outseqlen = needed;
  needed += compute_tag_length (needed);

  cipher = gcry_malloc (needed);
  if (!cipher)
    {
      log_error ("error allocating buffer\n");
      gcry_free (plain);
      return NULL;
    }
  p = cipher;
  /* Store the first sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, outseqlen);
  /* Store the data OID. */
  p = store_tag_length (p, TAG_OBJECT_ID, DIM (oid_data));
  memcpy (p, oid_data, DIM (oid_data)); 
  p += DIM (oid_data); 
  /* Next comes a context tag. */
  p = store_tag_length (p, 0xa0, out0taglen);
  /* And an octet string. */
  p = store_tag_length (p, TAG_OCTET_STRING, outoctstrlen);
  /* Two sequences. */
  p = store_tag_length (p, TAG_SEQUENCE, aseq1len);
  p = store_tag_length (p, TAG_SEQUENCE, aseq2len);
  /* Store the shroudedKeyBag OID. */
  p = store_tag_length (p, TAG_OBJECT_ID,
                        DIM (oid_pkcs_12_pkcs_8ShroudedKeyBag));
  memcpy (p, oid_pkcs_12_pkcs_8ShroudedKeyBag,
          DIM (oid_pkcs_12_pkcs_8ShroudedKeyBag)); 
  p += DIM (oid_pkcs_12_pkcs_8ShroudedKeyBag); 
  /* Next comes a context tag. */
  p = store_tag_length (p, 0xa0, in0taglen);
  /* And a sequence. */
  p = store_tag_length (p, TAG_SEQUENCE, aseq3len);
  /* Now for the pre-encoded algorithm indentifier and the salt. */
  memcpy (p, data_3desiter1024, DIM (data_3desiter1024));
  memcpy (p + DATA_3DESITER1024_SALT_OFF, salt, 8);
  p += DIM (data_3desiter1024);
  /* And finally the octet string with the encrypted data. */
  p = store_tag_length (p, TAG_OCTET_STRING, plainlen);
  memcpy (p, plain, plainlen);
  p += plainlen;
  cipherlen = p - cipher;
  
  if (needed != cipherlen)
    log_debug ("length mismatch: %u, %u\n", needed, cipherlen);
  gcry_free (plain);

  {
    struct buffer_s seqlist[2];

    seqlist[0].buffer = cipher;
    seqlist[0].length = cipherlen;
    seqlist[1].buffer = NULL;
    seqlist[1].length = 0;

    cipher = create_final (seqlist, &cipherlen);
    gcry_free (seqlist[0].buffer);
  }

  *r_length = cipherlen;
  return cipher;
}


#ifdef TEST
int
main (int argc, char **argv)
{
  FILE *fp;
  struct stat st;
  char *buf;
  size_t buflen;
  GcryMPI *result;

  if (argc != 3)
    {
      fprintf (stderr, "usage: testp12 file passphrase\n");
      return 1;
    }

  gcry_control (GCRYCTL_DISABLE_SECMEM, NULL);
  gcry_control (GCRYCTL_INITIALIZATION_FINISHED, NULL);

  fp = fopen (argv[1], "rb");
  if (!fp)
    {
      fprintf (stderr, "can't open `%s': %s\n", argv[1], strerror (errno));
      return 1;
    }
  
  if (fstat (fileno(fp), &st))
    {
      fprintf (stderr, "can't stat `%s': %s\n", argv[1], strerror (errno));
      return 1;
    }

  buflen = st.st_size;
  buf = gcry_malloc (buflen+1);
  if (!buf || fread (buf, buflen, 1, fp) != 1)
    {
      fprintf (stderr, "error reading `%s': %s\n", argv[1], strerror (errno));
      return 1;
    }
  fclose (fp);

  result = p12_parse (buf, buflen, argv[2]);
  if (result)
    {
      int i, rc;
      char *buf;

      for (i=0; result[i]; i++)
        {
          rc = gcry_mpi_aprint (GCRYMPI_FMT_HEX, (void**)&buf,
                                NULL, result[i]);
          if (rc)
            printf ("%d: [error printing number: %s]\n",
                    i, gcry_strerror (rc));
          else
            {
              printf ("%d: %s\n", i, buf);
              gcry_free (buf);
            }
        }
    }

  return 0;

}
#endif /* TEST */