58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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#include "mycrypt.h"
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#ifdef MRSA
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/* PKCS #1 v1.5 pad then sign */
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int rsa_v15_sign_hash(const unsigned char *msghash, unsigned long msghashlen,
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unsigned char *sig, unsigned long *siglen,
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prng_state *prng, int prng_idx,
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int hash_idx, rsa_key *key)
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{
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unsigned long modulus_bitlen, modulus_bytelen, x;
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int err;
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_ARGCHK(msghash != NULL);
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_ARGCHK(sig != NULL);
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_ARGCHK(siglen != NULL);
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_ARGCHK(key != NULL);
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/* valid prng and hash ? */
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if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
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return err;
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}
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if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
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return err;
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}
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/* get modulus len in bits */
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modulus_bitlen = mp_count_bits(&(key->N));
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/* outlen must be at least the size of the modulus */
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modulus_bytelen = mp_unsigned_bin_size(&(key->N));
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if (modulus_bytelen > *siglen) {
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return CRYPT_BUFFER_OVERFLOW;
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}
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/* PKCS #1 v1.5 pad the key */
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x = *siglen;
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if ((err = pkcs_1_v15_sa_encode(msghash, msghashlen, hash_idx, modulus_bitlen, sig, &x)) != CRYPT_OK) {
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return err;
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}
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/* RSA encode it */
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return rsa_exptmod(sig, x, sig, siglen, PK_PRIVATE, prng, prng_idx, key);
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}
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#endif
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