Mercurial > dropbear
view libtomcrypt/src/pk/dsa/dsa_verify_hash.c @ 1696:d18fa38c1fd4
initialise variable to stop warning
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Thu, 28 May 2020 22:02:03 +0800 |
parents | 6dba84798cd5 |
children |
line wrap: on
line source
/* 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. */ #include "tomcrypt.h" /** @file dsa_verify_hash.c DSA implementation, verify a signature, Tom St Denis */ #ifdef LTC_MDSA /** Verify a DSA signature @param r DSA "r" parameter @param s DSA "s" parameter @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DSA key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash_raw( void *r, void *s, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { void *w, *v, *u1, *u2; int err; LTC_ARGCHK(r != NULL); LTC_ARGCHK(s != NULL); LTC_ARGCHK(stat != NULL); LTC_ARGCHK(key != NULL); /* default to invalid signature */ *stat = 0; /* init our variables */ if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != CRYPT_OK) { return err; } /* neither r or s can be null or >q*/ if (mp_cmp_d(r, 0) != LTC_MP_GT || mp_cmp_d(s, 0) != LTC_MP_GT || mp_cmp(r, key->q) != LTC_MP_LT || mp_cmp(s, key->q) != LTC_MP_LT) { err = CRYPT_INVALID_PACKET; goto error; } /* FIPS 186-4 4.7: use leftmost min(bitlen(q), bitlen(hash)) bits of 'hash' */ hashlen = MIN(hashlen, (unsigned long)(key->qord)); /* w = 1/s mod q */ if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; } /* u1 = m * w mod q */ if ((err = mp_read_unsigned_bin(u1, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, w, key->q, u1)) != CRYPT_OK) { goto error; } /* u2 = r*w mod q */ if ((err = mp_mulmod(r, w, key->q, u2)) != CRYPT_OK) { goto error; } /* v = g^u1 * y^u2 mod p mod q */ if ((err = mp_exptmod(key->g, u1, key->p, u1)) != CRYPT_OK) { goto error; } if ((err = mp_exptmod(key->y, u2, key->p, u2)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, u2, key->p, v)) != CRYPT_OK) { goto error; } if ((err = mp_mod(v, key->q, v)) != CRYPT_OK) { goto error; } /* if r = v then we're set */ if (mp_cmp(r, v) == LTC_MP_EQ) { *stat = 1; } err = CRYPT_OK; error: mp_clear_multi(w, v, u1, u2, NULL); return err; } /** Verify a DSA signature @param sig The signature @param siglen The length of the signature (octets) @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DSA key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash(const unsigned char *sig, unsigned long siglen, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { int err; void *r, *s; ltc_asn1_list sig_seq[2]; unsigned long reallen = 0; LTC_ARGCHK(stat != NULL); *stat = 0; /* must be set before the first return */ if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) { return err; } LTC_SET_ASN1(sig_seq, 0, LTC_ASN1_INTEGER, r, 1UL); LTC_SET_ASN1(sig_seq, 1, LTC_ASN1_INTEGER, s, 1UL); err = der_decode_sequence(sig, siglen, sig_seq, 2); if (err != CRYPT_OK) { goto LBL_ERR; } err = der_length_sequence(sig_seq, 2, &reallen); if (err != CRYPT_OK || reallen != siglen) { goto LBL_ERR; } /* do the op */ err = dsa_verify_hash_raw(r, s, hash, hashlen, stat, key); LBL_ERR: mp_clear_multi(r, s, NULL); return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */