/* parsetlv.c -  ASN.1 TLV functions

 * Copyright (C) 2005, 2007, 2008, 2012 g10 Code GmbH

 *

 * This file 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 2.1 of

 * the License, or (at your option) any later version.

 *

 * This file 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 <https://www.gnu.org/licenses/>.

 */

#ifdef HAVE_CONFIG_H

# include <config.h>

#endif

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include "parsetlv.h"

/* Simple but pretty complete ASN.1 BER parser.  Parse the data at the

   address of BUFFER with a length given at the address of SIZE.  On

   success return 0 and update BUFFER and SIZE to point to the value.

   Do not update them on error.  The information about the object are

   stored in the caller allocated TI structure.  */

int

_gpgme_parse_tlv (char const **buffer, size_t *size, tlvinfo_t *ti)

{

  int c;

  unsigned long tag;

  const unsigned char *buf = (const unsigned char *)(*buffer);

  size_t length = *size;

  ti->cls = 0;

  ti->tag = 0;

  ti->is_cons = 0;

  ti->is_ndef = 0;

  ti->length = 0;

  ti->nhdr = 0;

  if (!length)

    return -1;

  c = *buf++; length--; ++ti->nhdr;

  ti->cls = (c & 0xc0) >> 6;

  ti->is_cons = !!(c & 0x20);

  tag = c & 0x1f;

  if (tag == 0x1f)

    {

      tag = 0;

      do

        {

          tag <<= 7;

          if (!length)

            return -1;

          c = *buf++; length--; ++ti->nhdr;

          tag |= c & 0x7f;

        }

      while (c & 0x80);

    }

  ti->tag = tag;

  if (!length)

    return -1;

  c = *buf++; length--; ++ti->nhdr;

  if ( !(c & 0x80) )

    ti->length = c;

  else if (c == 0x80)

    ti->is_ndef = 1;

  else if (c == 0xff)

    return -1;

  else

    {

      unsigned long len = 0;

      int count = (c & 0x7f);

      if (count > sizeof (len) || count > sizeof (size_t))

        return -1;

      for (; count; count--)

        {

          len <<= 8;

          if (!length)

            return -1;

          c = *buf++; length--; ++ti->nhdr;

          len |= c & 0xff;

        }

      ti->length = len;

    }

  *buffer = (void*)buf;

  *size = length;

  return 0;

}