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trying to fix dh_shared_secret - #119

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This commit is contained in:
Karel Miko 2017-06-11 23:20:46 +02:00
parent bc4236d90f
commit 114b694735
1 changed files with 14 additions and 9 deletions
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23
src/pk/dh/dh.c
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@ -355,7 +355,7 @@ error:
int dh_shared_secret(dh_key *private_key, dh_key *public_key, int dh_shared_secret(dh_key *private_key, dh_key *public_key,
unsigned char *out, unsigned long *outlen) unsigned char *out, unsigned long *outlen)
{ {
void *tmp, *p; void *tmp, *p, *p_minus1;
unsigned long x; unsigned long x;
int err; int err;
@ -375,26 +375,31 @@ int dh_shared_secret(dh_key *private_key, dh_key *public_key,
} }
/* compute y^x mod p */ /* compute y^x mod p */
if ((err = mp_init_multi(&tmp, &p, NULL)) != CRYPT_OK) { if ((err = mp_init_multi(&tmp, &p, &p_minus1, NULL)) != CRYPT_OK) {
return err; return err;
} }
if ((err = mp_read_radix(p, (char *)sets[private_key->idx].prime, 16)) != CRYPT_OK) { goto error; } if ((err = mp_read_radix(p, sets[private_key->idx].prime, 16)) != CRYPT_OK) { goto error; }
if ((err = mp_exptmod(public_key->y, private_key->x, p, tmp)) != CRYPT_OK) { goto error; } if ((err = mp_sub_d(p, 1, p_minus1)) != CRYPT_OK) { goto error; }
if (mp_cmp(public_key->y, p_minus1) != LTC_MP_LT || mp_cmp_d(public_key->y, 1) != LTC_MP_GT) {
/* reject public key with: y <= 1 OR y >= p-1 */
err = CRYPT_INVALID_ARG;
goto error;
};
if ((err = mp_exptmod(public_key->y, private_key->x, p, tmp)) != CRYPT_OK) { goto error; }
/* enough space for output? */ /* enough space for output? */
x = (unsigned long)mp_unsigned_bin_size(tmp); x = (unsigned long)mp_unsigned_bin_size(tmp);
if (*outlen < x) { if (*outlen < x) {
err = CRYPT_BUFFER_OVERFLOW; err = CRYPT_BUFFER_OVERFLOW;
goto done; goto error;
} }
if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) { goto error; } if ((err = mp_to_unsigned_bin(tmp, out)) != CRYPT_OK) { goto error; }
*outlen = x; *outlen = x;
err = CRYPT_OK; err = CRYPT_OK;
goto done;
error: error:
done: mp_clear_multi(p_minus1, p, tmp, NULL);
mp_clear_multi(p, tmp, NULL);
return err; return err;
} }