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sae: Handle error conditions more consistently

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In case an exceptional condition occurs, handle this more consistently
by returning the following errors:

  -ENOMSG -- If a message results in the retransmission timer t0 being
             restarted without actually sending anything.
  -EBADMSG -- If a received message is to be silently discarded without
              affecting the t0 timer.
  -ETIMEDOUT -- If SYNC_MAX has been exceeded
  -EPROTO -- If a fatal protocol error occurred
This commit is contained in:
Denis Kenzior 2021-07-10 19:19:06 -05:00
parent fefa93e3ba
commit 03b99ba0d5
1 changed files with 50 additions and 50 deletions
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100
src/sae.c
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@ -184,24 +184,29 @@ static bool sae_cn(const uint8_t *kck, uint16_t send_confirm,
return (ret == 32);
}
static void sae_reject_authentication(struct sae_sm *sm, uint16_t reason)
static int sae_reject(struct sae_sm *sm, uint16_t transaction, uint16_t status)
{
uint8_t reject[6];
uint8_t *ptr = reject;
if (!sm->handshake->authenticator)
return -EPROTO;
/* transaction */
l_put_u16(1, ptr);
ptr += 2;
/* status success */
l_put_u16(reason, ptr);
l_put_u16(transaction, ptr);
ptr += 2;
if (reason == MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP) {
l_put_u16(status, ptr);
ptr += 2;
if (status == MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP) {
l_put_u16(sm->group, ptr);
ptr += 2;
}
sm->tx_auth(reject, ptr - reject, sm->user_data);
return status;
}
static struct l_ecc_scalar *sae_new_residue(const struct l_ecc_curve *curve,
@ -483,7 +488,6 @@ static int sae_process_commit(struct sae_sm *sm, const uint8_t *from,
uint8_t kck_and_pmk[2][32];
uint8_t tmp[L_ECC_SCALAR_MAX_BYTES];
struct l_ecc_scalar *tmp_scalar;
uint16_t reason = MMPDU_REASON_CODE_UNSPECIFIED;
ssize_t klen;
struct l_ecc_scalar *order;
unsigned int nbytes = l_ecc_curve_get_scalar_bytes(sm->curve);
@ -493,8 +497,8 @@ static int sae_process_commit(struct sae_sm *sm, const uint8_t *from,
sm->p_scalar = l_ecc_scalar_new(sm->curve, ptr, nbytes);
if (!sm->p_scalar) {
l_error("Server sent invalid P_Scalar during commit");
reason = MMPDU_REASON_CODE_UNSPECIFIED;
goto reject;
return sae_reject(sm, SAE_STATE_COMMITTED,
MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP);
}
ptr += nbytes;
@ -503,16 +507,20 @@ static int sae_process_commit(struct sae_sm *sm, const uint8_t *from,
ptr, nbytes * 2);
if (!sm->p_element) {
l_error("Server sent invalid P_Element during commit");
reason = MMPDU_REASON_CODE_UNSPECIFIED;
goto reject;
return sae_reject(sm, SAE_STATE_COMMITTED,
MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP);
}
/*
* If they match those sent as part of the protocol instance's own
* SAE Commit message, the frame shall be silently discarded (because
* it is evidence of a reflection attack) and the t0 (retransmission)
* timer shall be set.
*/
if (l_ecc_scalars_are_equal(sm->p_scalar, sm->scalar) ||
l_ecc_points_are_equal(sm->p_element, sm->element)) {
/* possible reflection attack, silently discard message */
l_warn("peer scalar or element matched own, discarding frame");
return 0;
return -ENOMSG;
}
sm->sc++;
@ -543,7 +551,8 @@ static int sae_process_commit(struct sae_sm *sm, const uint8_t *from,
l_ecc_point_free(k_point);
if (klen < 0)
goto reject;
return sae_reject(sm, SAE_STATE_COMMITTED,
MMPDU_STATUS_CODE_UNSPECIFIED);
/* keyseed = H(<0>32, k) */
hmac_sha256(zero_key, 32, k, klen, keyseed, 32);
@ -580,10 +589,6 @@ static int sae_process_commit(struct sae_sm *sm, const uint8_t *from,
sm->state = SAE_STATE_CONFIRMED;
return 0;
reject:
sae_reject_authentication(sm, reason);
return -EBADMSG;
}
static bool sae_verify_confirm(struct sae_sm *sm, const uint8_t *frame)
@ -594,10 +599,8 @@ static bool sae_verify_confirm(struct sae_sm *sm, const uint8_t *frame)
sae_cn(sm->kck, rc, sm->p_scalar, sm->p_element, sm->scalar,
sm->element, check);
if (memcmp(frame + 2, check, 32)) {
l_error("confirm did not match");
if (memcmp(frame + 2, check, 32))
return false;
}
sm->rc = rc;
@ -611,11 +614,20 @@ static int sae_process_confirm(struct sae_sm *sm, const uint8_t *from,
if (len < 34) {
l_error("bad length");
goto reject;
return -EBADMSG;
}
if (!sae_verify_confirm(sm, ptr))
goto reject;
/*
* If processing is unsuccessful and the SAE Confirm message is not
* verified, protocol instance shall remain in Confirmed state.
*
* NOTE: We diverge from the protocol here and bail out early
*/
if (!sae_verify_confirm(sm, ptr)) {
l_error("SAE: Confirm could not be verified");
return sae_reject(sm, SAE_STATE_CONFIRMED,
MMPDU_STATUS_CODE_UNSPECIFIED);
}
/* Sc shall be set to the value 2^16 - 1 */
sm->sc = 0xffff;
@ -628,10 +640,6 @@ static int sae_process_confirm(struct sae_sm *sm, const uint8_t *from,
sm->tx_assoc(sm->user_data);
return 0;
reject:
sae_reject_authentication(sm, MMPDU_REASON_CODE_UNSPECIFIED);
return -EBADMSG;
}
static bool sae_send_commit(struct sae_sm *sm, bool retry)
@ -719,11 +727,9 @@ static int sae_verify_nothing(struct sae_sm *sm, uint16_t transaction,
return -EBADMSG;
/* reject with unsupported group */
if (l_get_le16(frame) != sm->group) {
sae_reject_authentication(sm,
if (l_get_le16(frame) != sm->group)
return sae_reject(sm, SAE_STATE_COMMITTED,
MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP);
return -EBADMSG;
}
return 0;
}
@ -765,10 +771,9 @@ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction,
*/
if (transaction == SAE_STATE_CONFIRMED) {
if (sm->sync > SAE_SYNC_MAX)
return -EBADMSG;
return -ETIMEDOUT;
sm->sync++;
sae_send_commit(sm, true);
return -EAGAIN;
@ -799,7 +804,7 @@ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction,
if (len == 0)
l_warn("AP did not include group number in response!");
else if (len >= 2 && (l_get_le16(frame) != sm->group))
return -EBADMSG;
return -ENOMSG;
sm->group_retry++;
@ -828,7 +833,6 @@ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction,
sm->curve = l_ecc_curve_from_ike_group(sm->group);
sm->sync = 0;
sae_send_commit(sm, false);
return -EAGAIN;
@ -838,7 +842,7 @@ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction,
if (l_get_le16(frame) != sm->group) {
l_error("SAE: Peer tried to change group -- Reject");
return -EPROTO;
goto reject_unsupp_group;
}
len -= 2;
@ -857,9 +861,8 @@ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction,
}
reject_unsupp_group:
sae_reject_authentication(sm,
return sae_reject(sm, SAE_STATE_COMMITTED,
MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP);
return MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP;
}
/*
@ -887,7 +890,7 @@ static int sae_verify_confirmed(struct sae_sm *sm, uint16_t trans,
* Nothing state.
*/
if (sm->sync > SAE_SYNC_MAX)
return -EBADMSG;
return -ETIMEDOUT;
if (len < 2)
return -EBADMSG;
@ -925,7 +928,7 @@ static int sae_verify_accepted(struct sae_sm *sm, uint16_t trans,
}
if (sm->sync > SAE_SYNC_MAX)
return -EBADMSG;
return -ETIMEDOUT;
if (len < 2)
return -EBADMSG;
@ -980,7 +983,7 @@ static int sae_verify_packet(struct sae_sm *sm, uint16_t trans,
}
/* should never get here */
return -1;
return -EPROTO;
}
static int sae_rx_authenticate(struct auth_proto *ap,
@ -993,11 +996,10 @@ static int sae_rx_authenticate(struct auth_proto *ap,
if (!hdr) {
l_debug("Auth frame header did not validate");
goto reject;
return -EBADMSG;
}
auth = mmpdu_body(hdr);
len -= mmpdu_header_len(hdr);
ret = sae_verify_packet(sm, L_LE16_TO_CPU(auth->transaction_sequence),
@ -1018,10 +1020,8 @@ static int sae_rx_authenticate(struct auth_proto *ap,
L_LE16_TO_CPU(auth->transaction_sequence));
}
reject:
sae_reject_authentication(sm, MMPDU_REASON_CODE_UNSPECIFIED);
return -EBADMSG;
/* should never get here */
return -EPROTO;
}
static int sae_rx_associate(struct auth_proto *ap, const uint8_t *frame,
@ -1039,7 +1039,7 @@ static int sae_rx_associate(struct auth_proto *ap, const uint8_t *frame,
body = mmpdu_body(mpdu);
if (body->status_code != 0)
return L_LE16_TO_CPU(body->status_code);
return -EPROTO;
return 0;
}