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FIPS 186-4 DSA validity tests

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This commit is contained in:
Karel Miko 2017-09-14 11:43:59 +02:00
parent 5fb4c9f89b
commit 1ea4fecc81
1 changed files with 36 additions and 25 deletions
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55
src/pk/dsa/dsa_verify_key.c
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@ -49,33 +49,33 @@ int dsa_verify_key(dsa_key *key, int *stat)
*/ */
int dsa_int_validate_pqg(dsa_key *key, int *stat) int dsa_int_validate_pqg(dsa_key *key, int *stat)
{ {
void *tmp, *tmp2; void *tmp1, *tmp2;
int err; int err;
*stat = 0; *stat = 0;
LTC_ARGCHK(key != NULL); LTC_ARGCHK(key != NULL);
LTC_ARGCHK(stat != NULL); LTC_ARGCHK(stat != NULL);
/* now make sure that g is not -1, 0 or 1 and <p */ /* FIPS 186-4 chapter 4.1: 1 < g < p */
if (mp_cmp_d(key->g, 0) == LTC_MP_EQ || mp_cmp_d(key->g, 1) == LTC_MP_EQ) { if (mp_cmp_d(key->g, 1) != LTC_MP_GT || mp_cmp(key->g, key->p) != LTC_MP_LT) {
return CRYPT_OK; return CRYPT_OK;
} }
if ((err = mp_init_multi(&tmp, &tmp2, NULL)) != CRYPT_OK) { return err; }
if ((err = mp_sub_d(key->p, 1, tmp)) != CRYPT_OK) { goto error; }
if (mp_cmp(tmp, key->g) == LTC_MP_EQ || mp_cmp(key->g, key->p) != LTC_MP_LT) {
err = CRYPT_OK;
goto error;
}
/* now we have to make sure that g^q = 1, and that p-1/q gives 0 remainder */ if ((err = mp_init_multi(&tmp1, &tmp2, NULL)) != CRYPT_OK) { return err; }
if ((err = mp_div(tmp, key->q, tmp, tmp2)) != CRYPT_OK) { goto error; }
/* FIPS 186-4 chapter 4.1: q is a divisor of (p - 1) */
if ((err = mp_sub_d(key->p, 1, tmp1)) != CRYPT_OK) { goto error; }
if ((err = mp_div(tmp1, key->q, tmp1, tmp2)) != CRYPT_OK) { goto error; }
if (mp_iszero(tmp2) != LTC_MP_YES) { if (mp_iszero(tmp2) != LTC_MP_YES) {
err = CRYPT_OK; err = CRYPT_OK;
goto error; goto error;
} }
if ((err = mp_exptmod(key->g, key->q, key->p, tmp)) != CRYPT_OK) { goto error; } /* FIPS 186-4 chapter 4.1: g is a generator of a subgroup of order q in
if (mp_cmp_d(tmp, 1) != LTC_MP_EQ) { * the multiplicative group of GF(p) - so we make sure that g^q mod p = 1
*/
if ((err = mp_exptmod(key->g, key->q, key->p, tmp1)) != CRYPT_OK) { goto error; }
if (mp_cmp_d(tmp1, 1) != LTC_MP_EQ) {
err = CRYPT_OK; err = CRYPT_OK;
goto error; goto error;
} }
@ -83,7 +83,7 @@ int dsa_int_validate_pqg(dsa_key *key, int *stat)
err = CRYPT_OK; err = CRYPT_OK;
*stat = 1; *stat = 1;
error: error:
mp_clear_multi(tmp, tmp2, NULL); mp_clear_multi(tmp1, tmp2, NULL);
return err; return err;
} }
@ -150,7 +150,25 @@ int dsa_int_validate_xy(dsa_key *key, int *stat)
goto error; goto error;
} }
/* now we have to make sure that y^q = 1, this makes sure y \in g^x mod p */ if (key->type == PK_PRIVATE) {
/* FIPS 186-4 chapter 4.1: 0 < x < q */
if (mp_cmp_d(key->x, 0) != LTC_MP_GT || mp_cmp(key->x, key->q) != LTC_MP_LT) {
err = CRYPT_OK;
goto error;
}
/* FIPS 186-4 chapter 4.1: y = g^x mod p */
if ((err = mp_exptmod(key->g, key->x, key->p, tmp)) != CRYPT_OK) {
goto error;
}
if (mp_cmp(tmp, key->y) != LTC_MP_EQ) {
err = CRYPT_OK;
goto error;
}
}
else {
/* with just a public key we cannot test y = g^x mod p therefore we
* only test that y^q mod p = 1, which makes sure y is in g^x mod p
*/
if ((err = mp_exptmod(key->y, key->q, key->p, tmp)) != CRYPT_OK) { if ((err = mp_exptmod(key->y, key->q, key->p, tmp)) != CRYPT_OK) {
goto error; goto error;
} }
@ -158,13 +176,6 @@ int dsa_int_validate_xy(dsa_key *key, int *stat)
err = CRYPT_OK; err = CRYPT_OK;
goto error; goto error;
} }
if (key->type == PK_PRIVATE) {
/* x > 1 */
if (!(mp_cmp_d(key->x, 1) == LTC_MP_GT)) {
err = CRYPT_OK;
goto error;
}
} }
err = CRYPT_OK; err = CRYPT_OK;