core/lib/libtomcrypt/src/pk/asn1/der/octet/der_decode_octet_string.c

// SPDX-License-Identifier: BSD-2-Clause
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt_private.h"

/**
  @file der_decode_octet_string.c
  ASN.1 DER, encode a OCTET STRING, Tom St Denis
*/


#ifdef LTC_DER

/**
  Store a OCTET STRING
  @param in      The DER encoded OCTET STRING
  @param inlen   The size of the DER OCTET STRING
  @param out     [out] The array of octets stored (one per char)
  @param outlen  [in/out] The number of octets stored
  @return CRYPT_OK if successful
*/
int der_decode_octet_string(const unsigned char *in, unsigned long inlen,
                                  unsigned char *out, unsigned long *outlen)
{
   unsigned long x, y, len;
   int err;

   LTC_ARGCHK(in     != NULL);
   LTC_ARGCHK(out    != NULL);
   LTC_ARGCHK(outlen != NULL);

   /* must have header at least */
   if (inlen < 2) {
      return CRYPT_INVALID_PACKET;
   }

   /* check for 0x04 */
   if ((in[0] & 0x1F) != 0x04) {
      return CRYPT_INVALID_PACKET;
   }
   x = 1;

   /* get the length of the data */
   y = inlen - x;
   if ((err = der_decode_asn1_length(in + x, &y, &len)) != CRYPT_OK) {
      return err;
   }
   x += y;

   /* is it too long? */
   if (len > *outlen) {
      *outlen = len;
      return CRYPT_BUFFER_OVERFLOW;
   }

   if (len > (inlen - x)) {
      return CRYPT_INVALID_PACKET;
   }

   /* read the data */
   for (y = 0; y < len; y++) {
       out[y] = in[x++];
   }

   *outlen = y;

   return CRYPT_OK;
}

#endif

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