/* 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"/* OAEP Padding for PKCS #1 -- Tom St Denis */#ifdef PKCS_1int pkcs_1_oaep_encode(const unsigned char *msg,    unsigned long msglen,                       const unsigned char *lparam, unsigned long lparamlen,                             unsigned long modulus_bitlen, prng_state *prng,                             int           prng_idx,         int  hash_idx,                             unsigned char *out,    unsigned long *outlen){   unsigned char DB[1024], seed[MAXBLOCKSIZE], mask[sizeof(DB)];   unsigned long hLen, x, y, modulus_len;   int           err;   _ARGCHK(msg    != NULL);   _ARGCHK(out    != NULL);   _ARGCHK(outlen != NULL);   /* test valid hash */   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {       return err;   }   /* valid prng */   if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {      return err;   }   hLen        = hash_descriptor[hash_idx].hashsize;   modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);   /* test message size */   if (modulus_len >= sizeof(DB) || msglen > (modulus_len - 2*hLen - 2)) {      return CRYPT_PK_INVALID_SIZE;   }   /* get lhash */// DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes   x = sizeof(DB);   if (lparam != NULL) {      if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) {         return err;      }   } else {      /* can't pass hash_memory a NULL so use DB with zero length */      if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) {         return err;      }   }   /* append PS then 0x01 (to lhash)  */   x = hLen;   y = modulus_len - msglen - 2*hLen - 2;   while (y--) {      DB[x++] = 0x00;   }   DB[x++] = 0x01;   /* message */   y = msglen;   while (y--) {     DB[x++] = *msg++;   }   /* now choose a random seed */   if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) {      return CRYPT_ERROR_READPRNG;   }   /* compute MGF1 of seed (k - hlen - 1) */   if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {      return err;   }   /* xor against DB */   for (y = 0; y < (modulus_len - hLen - 1); y++) {       DB[y] ^= mask[y];    }   /* compute MGF1 of maskedDB (hLen) */    if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) {      return err;   }   /* XOR against seed */   for (y = 0; y < hLen; y++) {      seed[y] ^= mask[y];   }   /* create string of length modulus_len */   if (*outlen < modulus_len) {      return CRYPT_BUFFER_OVERFLOW;   }   /* start output which is 0x00 || maskedSeed || maskedDB */   x = 0;   out[x++] = 0x00;   for (y = 0; y < hLen; y++) {      out[x++] = seed[y];   }   for (y = 0; y < modulus_len - hLen - 1; y++) {      out[x++] = DB[y];   }   *outlen = x;#ifdef CLEAN_STACK   zeromem(DB,   sizeof(DB));   zeromem(seed, sizeof(seed));   zeromem(mask, sizeof(mask));#endif   return CRYPT_OK;}#endif /* PKCS_1 */