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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.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
*/
#include "tomcrypt.h"
/**
@file rsa_verify_hash.c
RSA PKCS v2 PSS signature verification, Tom St Denis
*/
#ifdef MRSA
/**
(PKCS #1, v2.0) de-sign then PSS depad
@param sig The signature data
@param siglen The length of the signature data (octets)
@param hash The hash of the message that was signed
@param hashlen The length of the hash of the message that was signed (octets)
@param hash_idx The index of the desired hash
@param saltlen The length of the salt used during signature
@param stat [out] The result of the signature comparison, 1==valid, 0==invalid
@param key The public RSA key corresponding to the key that performed the signature
@return CRYPT_OK on success (even if the signature is invalid)
*/
int rsa_verify_hash(const unsigned char *sig, unsigned long siglen,
const unsigned char *hash, unsigned long hashlen,
int hash_idx, unsigned long saltlen,
int *stat, rsa_key *key)
{
unsigned long modulus_bitlen, modulus_bytelen, x;
int err;
unsigned char *tmpbuf;
LTC_ARGCHK(hash != NULL);
LTC_ARGCHK(sig != NULL);
LTC_ARGCHK(stat != NULL);
LTC_ARGCHK(key != NULL);
/* default to invalid */
*stat = 0;
/* valid hash ? */
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_INVALID_PACKET;
}
/* allocate temp buffer for decoded sig */
tmpbuf = XMALLOC(siglen);
if (tmpbuf == NULL) {
return CRYPT_MEM;
}
/* RSA decode it */
x = siglen;
if ((err = rsa_exptmod(sig, siglen, tmpbuf, &x, PK_PUBLIC, key)) != CRYPT_OK) {
XFREE(tmpbuf);
return err;
}
/* PSS decode it */
err = pkcs_1_pss_decode(hash, hashlen, tmpbuf, x, saltlen, hash_idx, modulus_bitlen, stat);
XFREE(tmpbuf);
return err;
}
#endif /* MRSA */
/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_verify_hash.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2005/05/05 14:35:59 $ */
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