view libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c @ 1659:d32bcb5c557d

Add Ed25519 support (#91) * Add support for Ed25519 as a public key type Ed25519 is a elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance. It may be used for both user and host keys. OpenSSH key import and fuzzer are not supported yet. Initially inspired by Peter Szabo. * Add curve25519 and ed25519 fuzzers * Add import and export of Ed25519 keys
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Wed, 11 Mar 2020 21:09:45 +0500
parents 6dba84798cd5
children
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/* 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.h"

/**
  @file pkcs_1_pss_encode.c
  PKCS #1 PSS Signature Padding, Tom St Denis
*/

#ifdef LTC_PKCS_1

/**
   PKCS #1 v2.00 Signature Encoding
   @param msghash          The hash to encode
   @param msghashlen       The length of the hash (octets)
   @param saltlen          The length of the salt desired (octets)
   @param prng             An active PRNG context
   @param prng_idx         The index of the PRNG desired
   @param hash_idx         The index of the hash desired
   @param modulus_bitlen   The bit length of the RSA modulus
   @param out              [out] The destination of the encoding
   @param outlen           [in/out] The max size and resulting size of the encoded data
   @return CRYPT_OK if successful
*/
int 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, *mask, *salt, *hash;
   unsigned long x, y, hLen, modulus_len;
   int           err;
   hash_state    md;

   LTC_ARGCHK(msghash != NULL);
   LTC_ARGCHK(out     != NULL);
   LTC_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_bitlen--;
   modulus_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);

   /* check sizes */
   if ((saltlen > modulus_len) || (modulus_len < hLen + saltlen + 2)) {
      return CRYPT_PK_INVALID_SIZE;
   }

   /* allocate ram for DB/mask/salt/hash of size modulus_len */
   DB   = XMALLOC(modulus_len);
   mask = XMALLOC(modulus_len);
   salt = XMALLOC(modulus_len);
   hash = XMALLOC(modulus_len);
   if (DB == NULL || mask == NULL || salt == NULL || hash == NULL) {
      if (DB != NULL) {
         XFREE(DB);
      }
      if (mask != NULL) {
         XFREE(mask);
      }
      if (salt != NULL) {
         XFREE(salt);
      }
      if (hash != NULL) {
         XFREE(hash);
      }
      return CRYPT_MEM;
   }


   /* generate random salt */
   if (saltlen > 0) {
      if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) {
         err = CRYPT_ERROR_READPRNG;
         goto LBL_ERR;
      }
   }

   /* M = (eight) 0x00 || msghash || salt, hash = H(M) */
   if ((err = hash_descriptor[hash_idx].init(&md)) != CRYPT_OK) {
      goto LBL_ERR;
   }
   zeromem(DB, 8);
   if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) {
      goto LBL_ERR;
   }
   if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) {
      goto LBL_ERR;
   }
   if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) {
      goto LBL_ERR;
   }
   if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) {
      goto LBL_ERR;
   }

   /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */
   x = 0;
   XMEMSET(DB + x, 0, modulus_len - saltlen - hLen - 2);
   x += modulus_len - saltlen - hLen - 2;
   DB[x++] = 0x01;
   XMEMCPY(DB + x, salt, saltlen);
   /* x += saltlen; */

   /* generate mask of length modulus_len - hLen - 1 from hash */
   if ((err = pkcs_1_mgf1(hash_idx, hash, hLen, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
      goto LBL_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) {
      *outlen = modulus_len;
      err = CRYPT_BUFFER_OVERFLOW;
      goto LBL_ERR;
   }

   /* DB len = modulus_len - hLen - 1 */
   y = 0;
   XMEMCPY(out + y, DB, modulus_len - hLen - 1);
   y += modulus_len - hLen - 1;

   /* hash */
   XMEMCPY(out + y, hash, hLen);
   y += hLen;

   /* 0xBC */
   out[y] = 0xBC;

   /* now clear the 8*modulus_len - modulus_bitlen most significant bits */
   out[0] &= 0xFF >> ((modulus_len<<3) - modulus_bitlen);

   /* store output size */
   *outlen = modulus_len;
   err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(DB,   modulus_len);
   zeromem(mask, modulus_len);
   zeromem(salt, modulus_len);
   zeromem(hash, modulus_len);
#endif

   XFREE(hash);
   XFREE(salt);
   XFREE(mask);
   XFREE(DB);

   return err;
}

#endif /* LTC_PKCS_1 */

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