/* 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 PSS Signature Padding -- Tom St Denis */#ifdef PKCS_1int pkcs_1_pss_encode(const unsigned char *msghash, unsigned long msghashlen,                            unsigned long saltlen,  prng_state   *prng,                                 int           prng_idx, int           hash_idx,                            unsigned long modulus_bitlen,                            unsigned char *out,     unsigned long *outlen){   unsigned char DB[1024], mask[sizeof(DB)], salt[sizeof(DB)], hash[sizeof(DB)];   unsigned long x, y, hLen, modulus_len;   int           err;   hash_state    md;   _ARGCHK(msghash != NULL);   _ARGCHK(out     != NULL);   _ARGCHK(outlen  != NULL);   /* ensure hash and PRNG are valid */   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {      return err;   }   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);   /* check sizes */   if ((saltlen > sizeof(salt)) || (modulus_len > sizeof(DB)) || (modulus_len < hLen + saltlen + 2)) {      return CRYPT_INVALID_ARG;   }   /* generate random salt */   if (saltlen > 0) {      if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) {         return CRYPT_ERROR_READPRNG;      }   }   /* M = (eight) 0x00 || msghash || salt, hash = H(M) */   hash_descriptor[hash_idx].init(&md);   zeromem(DB, 8);   if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) {      return err;   }   if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) {      return err;   }   if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) {      return err;   }   if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) {      return err;   }   /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */   for (x = 0; x < (modulus_len - saltlen - hLen - 2); x++) {       DB[x] = 0x00;   }   DB[x++] = 0x01;   for (y = 0; y < saltlen; y++) {      DB[x++] = salt[y];   }   /* generate mask of length modulus_len - hLen - 1 from hash */   if ((err = pkcs_1_mgf1(hash, 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];   }   /* output is DB || hash || 0xBC */   if (*outlen < modulus_len) {      return CRYPT_BUFFER_OVERFLOW;   }   /* DB */   for (y = x = 0; x < modulus_len - hLen - 1; x++) {       out[y++] = DB[x];   }   /* hash */   for (x = 0; x < hLen; x++) {       out[y++] = hash[x];   }   /* 0xBC */   out[y] = 0xBC;   /* now clear the 8*modulus_len - modulus_bitlen most significant bits */   out[0] &= 0xFF >> ((modulus_len<<3) - (modulus_bitlen-1));   /* store output size */   *outlen = modulus_len;#ifdef CLEAN_STACK   zeromem(DB,   sizeof(DB));      zeromem(mask, sizeof(mask));      zeromem(salt, sizeof(salt));      zeromem(hash, sizeof(hash));   #endif   return CRYPT_OK;}#endif /* PKCS_1 */