/*

 * simpletlv.c: Simple TLV encoding and decoding functions

 *

 * Copyright (C) 2016  Red Hat, Inc.

 *

 * Authors: Robert Relyea <rrelyea@redhat.com>

 *          Jakub Jelen <jjelen@redhat.com>

 *

 * This 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 2.1 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 library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <stdio.h>

#include <string.h>

#include <ctype.h>

#include <assert.h>

#include <stdlib.h>

#include "internal.h"

#include "simpletlv.h"

/*

 * Put a tag/length record to a file in Simple TLV based on the  datalen

 * content length.

 */

int

sc_simpletlv_put_tag(u8 tag, size_t datalen, u8 *out, size_t outlen, u8 **ptr)

{

  u8 *p = out;

  if (outlen < 2 || (outlen < 4 && datalen >= 0xff))

    return SC_ERROR_INVALID_ARGUMENTS;

  /* tag is just number between 0x01 and 0xFE */

  if (tag == 0x00 || tag == 0xff)

    return SC_ERROR_INVALID_ARGUMENTS;

  if (datalen > 0xffff) {

    /* we can't store more than two bytes in Simple TLV */

    return SC_ERROR_WRONG_LENGTH;

  }

  *p++ = tag; /* tag is single byte */

  if (datalen < 0xff) {

    /* short value up to 255 */

    *p++ = (u8)datalen; /* is in the second byte */

  } else {

    /* longer values up to 65535 */

    *p++ = (u8)0xff; /* first byte is 0xff */

    *p++ = (u8)datalen & 0xff;

    *p++ = (u8)(datalen >> 8) & 0xff; /* LE */

  }

  if (ptr != NULL)

    *ptr = p;

  return SC_SUCCESS;

}

/* Read the TL file and return appropriate tag and the length of associated

 * content.

 */

int

sc_simpletlv_read_tag(const u8 **buf, size_t buflen, u8 *tag_out, size_t *taglen)

{

  u8 tag;

  size_t left = buflen, len;

  const u8 *p = *buf;

  *buf = NULL;

  if (left < 2) {

    return SC_ERROR_INVALID_TLV_OBJECT;

  }

  tag = *p;

  p++;

  len = *p;

  p++;

  left -= 2;

  if (len == 0xff) {

    /* don't crash on bad data */

    if (left < 2) {

      return SC_ERROR_INVALID_TLV_OBJECT;

    }

    /* skip two bytes (the size) */

    len = lebytes2ushort(p);

    p += 2;

    left -= 2;

  }

  *tag_out = tag;

  *taglen = len;

  *buf = p;

  if (len > left)

    return SC_ERROR_TLV_END_OF_CONTENTS;

  return SC_SUCCESS;

}