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Merge pull request #408 from libtom/pr/fix-cve-2018-12437

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ecc_sign_hash blinding CVE-2018-12437
(cherry picked from commit 6aef5e3765cb84dd610883932c170975cf254167)
This commit is contained in:
karel-m 2018-06-19 09:30:51 +02:00 committed by Steffen Jaeckel
parent 94132324a9
commit 250eced904
1 changed files with 10 additions and 7 deletions
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17
src/pk/ecc/ecc_sign_hash.c
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@ -21,7 +21,7 @@ static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen,
prng_state *prng, int wprng, ecc_key *key, int sigformat)
{
ecc_key pubkey;
void *r, *s, *e, *p;
void *r, *s, *e, *p, *b;
int err, max_iterations = LTC_PK_MAX_RETRIES;
unsigned long pbits, pbytes, i, shift_right;
unsigned char ch, buf[MAXBLOCKSIZE];
@ -46,7 +46,7 @@ static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen,
}
/* init the bignums */
if ((err = mp_init_multi(&r, &s, &p, &e, NULL)) != CRYPT_OK) {
if ((err = mp_init_multi(&r, &s, &p, &e, &b, NULL)) != CRYPT_OK) {
return err;
}
if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto errnokey; }
@ -82,12 +82,15 @@ static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen,
if (mp_iszero(r) == LTC_MP_YES) {
ecc_free(&pubkey);
} else {
if ((err = rand_bn_upto(b, p, prng, wprng)) != CRYPT_OK) { goto error; } /* b = blinding value */
/* find s = (e + xr)/k */
if ((err = mp_invmod(pubkey.k, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = 1/k */
if ((err = mp_mulmod(pubkey.k, b, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = kb */
if ((err = mp_invmod(pubkey.k, p, pubkey.k)) != CRYPT_OK) { goto error; } /* k = 1/kb */
if ((err = mp_mulmod(key->k, r, p, s)) != CRYPT_OK) { goto error; } /* s = xr */
if ((err = mp_add(e, s, s)) != CRYPT_OK) { goto error; } /* s = e + xr */
if ((err = mp_mod(s, p, s)) != CRYPT_OK) { goto error; } /* s = e + xr */
if ((err = mp_mulmod(s, pubkey.k, p, s)) != CRYPT_OK) { goto error; } /* s = (e + xr)/k */
if ((err = mp_mulmod(pubkey.k, s, p, s)) != CRYPT_OK) { goto error; } /* s = xr/kb */
if ((err = mp_mulmod(pubkey.k, e, p, e)) != CRYPT_OK) { goto error; } /* e = e/kb */
if ((err = mp_add(e, s, s)) != CRYPT_OK) { goto error; } /* s = e/kb + xr/kb */
if ((err = mp_mulmod(s, b, p, s)) != CRYPT_OK) { goto error; } /* s = b(e/kb + xr/kb) = (e + xr)/k */
ecc_free(&pubkey);
if (mp_iszero(s) == LTC_MP_NO) {
break;
@ -121,7 +124,7 @@ static int _ecc_sign_hash(const unsigned char *in, unsigned long inlen,
error:
ecc_free(&pubkey);
errnokey:
mp_clear_multi(r, s, p, e, NULL);
mp_clear_multi(r, s, p, e, b, NULL);
return err;
}