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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.com
*/
#include "tomcrypt.h"
/**
@file rsa_verify_hash.c
RSA PKCS #1 v1.5 or v2 PSS signature verification, Tom St Denis and Andreas Lange
*/
#ifdef MRSA
/**
PKCS #1 de-sign then v1.5 or 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 padding Type of padding (LTC_PKCS_1_PSS or LTC_PKCS_1_V1_5)
@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_ex(const unsigned char *sig, unsigned long siglen,
const unsigned char *hash, unsigned long hashlen,
int padding,
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 padding? */
if ((padding != LTC_PKCS_1_V1_5) &&
(padding != LTC_PKCS_1_PSS)) {
return CRYPT_PK_INVALID_PADDING;
}
if (padding == LTC_PKCS_1_PSS) {
/* 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 = ltc_mp.rsa_me(sig, siglen, tmpbuf, &x, PK_PUBLIC, key)) != CRYPT_OK) {
XFREE(tmpbuf);
return err;
}
/* make sure the output is the right size */
if (x != siglen) {
XFREE(tmpbuf);
return CRYPT_INVALID_PACKET;
}
if (padding == LTC_PKCS_1_PSS) {
/* PSS decode and verify it */
err = pkcs_1_pss_decode(hash, hashlen, tmpbuf, x, saltlen, hash_idx, modulus_bitlen, stat);
} else {
/* PKCS #1 v1.5 decode it */
unsigned char *out;
unsigned long outlen, loid[16];
int decoded;
ltc_asn1_list digestinfo[2], siginfo[2];
/* not all hashes have OIDs... so sad */
if (hash_descriptor[hash_idx].OIDlen == 0) {
err = CRYPT_INVALID_ARG;
goto bail_2;
}
/* allocate temp buffer for decoded hash */
outlen = ((modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0)) - 3;
out = XMALLOC(outlen);
if (out == NULL) {
err = CRYPT_MEM;
goto bail_2;
}
if ((err = pkcs_1_v1_5_decode(tmpbuf, x, LTC_PKCS_1_EMSA, modulus_bitlen, out, &outlen, &decoded)) != CRYPT_OK) {
XFREE(out);
goto bail_2;
}
/* now we must decode out[0...outlen-1] using ASN.1, test the OID and then test the hash */
/* construct the SEQUENCE
SEQUENCE {
SEQUENCE {hashoid OID
blah NULL
}
hash OCTET STRING
}
*/
LTC_SET_ASN1(digestinfo, 0, LTC_ASN1_OBJECT_IDENTIFIER, loid, sizeof(loid)/sizeof(loid[0]));
LTC_SET_ASN1(digestinfo, 1, LTC_ASN1_NULL, NULL, 0);
LTC_SET_ASN1(siginfo, 0, LTC_ASN1_SEQUENCE, digestinfo, 2);
LTC_SET_ASN1(siginfo, 1, LTC_ASN1_OCTET_STRING, tmpbuf, siglen);
if ((err = der_decode_sequence(out, outlen, siginfo, 2)) != CRYPT_OK) {
XFREE(out);
goto bail_2;
}
/* test OID */
if ((digestinfo[0].size == hash_descriptor[hash_idx].OIDlen) &&
(XMEMCMP(digestinfo[0].data, hash_descriptor[hash_idx].OID, sizeof(unsigned long) * hash_descriptor[hash_idx].OIDlen) == 0) &&
(siginfo[1].size == hashlen) &&
(XMEMCMP(siginfo[1].data, hash, hashlen) == 0)) {
*stat = 1;
}
#ifdef LTC_CLEAN_STACK
zeromem(out, outlen);
#endif
XFREE(out);
}
bail_2:
#ifdef LTC_CLEAN_STACK
zeromem(tmpbuf, siglen);
#endif
XFREE(tmpbuf);
return err;
}
#endif /* MRSA */
/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_verify_hash.c,v $ */
/* $Revision: 1.11 $ */
/* $Date: 2006/12/04 03:09:28 $ */
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