| /* 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" |
| |
| #ifdef MRSA |
| |
| /* PKCS #1 v1.5 pad then sign */ |
| int rsa_v15_sign_hash(const unsigned char *msghash, unsigned long msghashlen, |
| unsigned char *sig, unsigned long *siglen, |
| prng_state *prng, int prng_idx, |
| int hash_idx, rsa_key *key) |
| { |
| unsigned long modulus_bitlen, modulus_bytelen, x; |
| int err; |
| |
| _ARGCHK(msghash != NULL); |
| _ARGCHK(sig != NULL); |
| _ARGCHK(siglen != NULL); |
| _ARGCHK(key != NULL); |
| |
| /* valid prng and hash ? */ |
| if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) { |
| return err; |
| } |
| if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* get modulus len in bits */ |
| modulus_bitlen = mp_count_bits(&(key->N)); |
| |
| /* outlen must be at least the size of the modulus */ |
| modulus_bytelen = mp_unsigned_bin_size(&(key->N)); |
| if (modulus_bytelen > *siglen) { |
| return CRYPT_BUFFER_OVERFLOW; |
| } |
| |
| /* PKCS #1 v1.5 pad the key */ |
| x = *siglen; |
| if ((err = pkcs_1_v15_sa_encode(msghash, msghashlen, hash_idx, modulus_bitlen, sig, &x)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* RSA encode it */ |
| return rsa_exptmod(sig, x, sig, siglen, PK_PRIVATE, prng, prng_idx, key); |
| } |
| |
| #endif |