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https://github.com/clearml/dropbear
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a938f4cfe1
to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a) --HG-- extra : convert_revision : 52ccb0ad0587a62bc64aecb939adbb76546aac16
127 lines
4.0 KiB
C
127 lines
4.0 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@gmail.com, http://libtomcrypt.com
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*/
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#include "tomcrypt.h"
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/**
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@file dsa_verify_hash.c
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DSA implementation, verify a signature, Tom St Denis
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*/
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#ifdef MDSA
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/**
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Verify a DSA signature
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@param r DSA "r" parameter
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@param s DSA "s" parameter
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@param hash The hash that was signed
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@param hashlen The length of the hash that was signed
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@param stat [out] The result of the signature verification, 1==valid, 0==invalid
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@param key The corresponding public DH key
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@return CRYPT_OK if successful (even if the signature is invalid)
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*/
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int dsa_verify_hash_raw( void *r, void *s,
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const unsigned char *hash, unsigned long hashlen,
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int *stat, dsa_key *key)
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{
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void *w, *v, *u1, *u2;
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int err;
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LTC_ARGCHK(r != NULL);
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LTC_ARGCHK(s != NULL);
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LTC_ARGCHK(stat != NULL);
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LTC_ARGCHK(key != NULL);
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/* default to invalid signature */
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*stat = 0;
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/* init our variables */
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if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != CRYPT_OK) {
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return err;
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}
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/* neither r or s can be null or >q*/
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if (mp_iszero(r) == LTC_MP_YES || mp_iszero(s) == LTC_MP_YES || mp_cmp(r, key->q) != LTC_MP_LT || mp_cmp(s, key->q) != LTC_MP_LT) {
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err = CRYPT_INVALID_PACKET;
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goto error;
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}
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/* w = 1/s mod q */
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if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; }
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/* u1 = m * w mod q */
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if ((err = mp_read_unsigned_bin(u1, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; }
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if ((err = mp_mulmod(u1, w, key->q, u1)) != CRYPT_OK) { goto error; }
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/* u2 = r*w mod q */
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if ((err = mp_mulmod(r, w, key->q, u2)) != CRYPT_OK) { goto error; }
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/* v = g^u1 * y^u2 mod p mod q */
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if ((err = mp_exptmod(key->g, u1, key->p, u1)) != CRYPT_OK) { goto error; }
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if ((err = mp_exptmod(key->y, u2, key->p, u2)) != CRYPT_OK) { goto error; }
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if ((err = mp_mulmod(u1, u2, key->p, v)) != CRYPT_OK) { goto error; }
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if ((err = mp_mod(v, key->q, v)) != CRYPT_OK) { goto error; }
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/* if r = v then we're set */
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if (mp_cmp(r, v) == LTC_MP_EQ) {
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*stat = 1;
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}
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err = CRYPT_OK;
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error:
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mp_clear_multi(w, v, u1, u2, NULL);
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return err;
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}
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/**
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Verify a DSA signature
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@param sig The signature
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@param siglen The length of the signature (octets)
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@param hash The hash that was signed
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@param hashlen The length of the hash that was signed
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@param stat [out] The result of the signature verification, 1==valid, 0==invalid
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@param key The corresponding public DH key
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@return CRYPT_OK if successful (even if the signature is invalid)
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*/
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int dsa_verify_hash(const unsigned char *sig, unsigned long siglen,
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const unsigned char *hash, unsigned long hashlen,
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int *stat, dsa_key *key)
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{
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int err;
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void *r, *s;
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if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) {
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return CRYPT_MEM;
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}
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/* decode the sequence */
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if ((err = der_decode_sequence_multi(sig, siglen,
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LTC_ASN1_INTEGER, 1UL, r,
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LTC_ASN1_INTEGER, 1UL, s,
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LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* do the op */
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err = dsa_verify_hash_raw(r, s, hash, hashlen, stat, key);
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LBL_ERR:
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mp_clear_multi(r, s, NULL);
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return err;
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}
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#endif
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/* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_hash.c,v $ */
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/* $Revision: 1.13 $ */
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/* $Date: 2006/12/04 03:18:43 $ */
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