/* 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. * * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org */#include "mycrypt.h"/* PKCS #1 v1.5 Encryption Padding -- Tom St Denis */#ifdef PKCS_1int pkcs_1_v15_es_decode(const unsigned char *msg,  unsigned long msglen,                               unsigned long modulus_bitlen,                               unsigned char *out,  unsigned long outlen,                               int           *res){   unsigned long x, modulus_bytelen;   _ARGCHK(msg != NULL);   _ARGCHK(out != NULL);   _ARGCHK(res != NULL);      /* default to failed */   *res = 0;   /* must be at least 12 bytes long */   if (msglen < 12) {      return CRYPT_INVALID_ARG;   }   modulus_bytelen = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);   /* should start with 0x00 0x02 */   if (msg[0] != 0x00 || msg[1] != 0x02) {      return CRYPT_OK;   }      /* skip over PS */   x = 2 + (modulus_bytelen - outlen - 3);   /* should be 0x00 */   if (msg[x++] != 0x00) {      return CRYPT_OK;   }   /* the message is left */   if (x + outlen > modulus_bytelen) {      return CRYPT_PK_INVALID_SIZE;   }   memcpy(out, msg + x, outlen);   *res = 1;   return CRYPT_OK;}#endif