| /* 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@gmail.com, http://libtomcrypt.org |
| */ |
| #include "tomcrypt.h" |
| |
| /** |
| @file pkcs_1_pss_encode.c |
| PKCS #1 PSS Signature Padding, Tom St Denis |
| */ |
| |
| #ifdef 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_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 */ |
| 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) { |
| 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) { |
| err = CRYPT_BUFFER_OVERFLOW; |
| goto LBL_ERR; |
| } |
| |
| /* 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; |
| 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 /* PKCS_1 */ |