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handshake: Only bitwise compare when needed

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handshake_util_ap_ie_matches() is used to make sure that the RSN element
received from the Authenticator during handshake / association response
is the same as the one advertised in Beacon/Probe Response frames.  This
utility tries to bitwise compare the element first, and only if that
fails, compares RSN members individually.

For FT, bitwise comparison will always fail since the PMKID has to be
included by the Authenticator in any RSN IEs included in Authenticate
& Association Response frames.

Perform the bitwise comparison as an optimization only during processing
of eapol message 3/4.  Also keep the parsed rsn information for future
use and to possibly avoid re-parsing it during later checks.
This commit is contained in:
Denis Kenzior 2021-09-17 09:09:43 -05:00
parent 4d95e3a161
commit c235c9fa54
4 changed files with 50 additions and 66 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
src/eapol.c
View File

@ -1623,11 +1623,13 @@ static void eapol_handle_ptk_3_of_4(struct eapol_sm *sm,
const uint8_t *igtk = NULL;
size_t igtk_len;
const uint8_t *rsne;
struct ie_rsn_info rsn_info;
const uint8_t *optional_rsne = NULL;
const uint8_t *transition_disable;
size_t transition_disable_len;
uint8_t gtk_key_index;
uint16_t igtk_key_index;
int r;
l_debug("ifindex=%u", hs->ifindex);
@ -1667,20 +1669,26 @@ static void eapol_handle_ptk_3_of_4(struct eapol_sm *sm,
if (!rsne)
goto error_ie_different;
if (!handshake_util_ap_ie_matches(rsne, hs->authenticator_ie,
hs->wpa_ie))
if (!hs->wpa_ie)
r = ie_parse_rsne_from_data(rsne, rsne[1] + 2, &rsn_info);
else
r = ie_parse_wpa_from_data(rsne, rsne[1] + 2, &rsn_info);
if (r < 0)
goto error_ie_different;
if ((rsne[1] != hs->authenticator_ie[1] ||
memcmp(rsne + 2, hs->authenticator_ie + 2, rsne[1])) &&
!handshake_util_ap_ie_matches(&rsn_info,
hs->authenticator_ie,
hs->wpa_ie))
goto error_ie_different;
if (hs->akm_suite &
(IE_RSN_AKM_SUITE_FT_OVER_8021X |
IE_RSN_AKM_SUITE_FT_USING_PSK |
IE_RSN_AKM_SUITE_FT_OVER_SAE_SHA256)) {
struct ie_rsn_info ie_info;
if (ie_parse_rsne_from_data(rsne, rsne[1] + 2, &ie_info) < 0)
goto error_ie_different;
if (ie_info.num_pmkids != 1 || memcmp(ie_info.pmkids,
if (rsn_info.num_pmkids != 1 || memcmp(rsn_info.pmkids,
hs->pmk_r1_name, 16))
goto error_ie_different;
@ -1727,13 +1735,9 @@ static void eapol_handle_ptk_3_of_4(struct eapol_sm *sm,
* RSNE or deauthenticates."
*/
if (optional_rsne) {
struct ie_rsn_info info1;
struct ie_rsn_info info2;
uint16_t override;
if (ie_parse_rsne_from_data(rsne, rsne[1] + 2, &info1) < 0)
goto error_ie_different;
if (ie_parse_rsne_from_data(optional_rsne, optional_rsne[1] + 2,
&info2) < 0)
goto error_ie_different;
@ -1757,14 +1761,14 @@ static void eapol_handle_ptk_3_of_4(struct eapol_sm *sm,
* and rsne2
* - Check that rsne2 pairwise_ciphers is a subset of rsne
*/
if (info1.akm_suites != info2.akm_suites ||
info1.group_cipher != info2.group_cipher)
if (rsn_info.akm_suites != info2.akm_suites ||
rsn_info.group_cipher != info2.group_cipher)
goto error_ie_different;
override = info2.pairwise_ciphers;
if (override == info1.pairwise_ciphers ||
!(info1.pairwise_ciphers & override) ||
if (override == rsn_info.pairwise_ciphers ||
!(rsn_info.pairwise_ciphers & override) ||
__builtin_popcount(override) != 1) {
handshake_failed(sm,
MMPDU_REASON_CODE_INVALID_PAIRWISE_CIPHER);

5
src/ft.c
View File

@ -323,7 +323,7 @@ static bool ft_verify_rsne(const uint8_t *rsne, const uint8_t *pmk_r0_name,
memcmp(msg2_rsne.pmkids, pmk_r0_name, 16))
return false;
if (!handshake_util_ap_ie_matches(rsne, authenticator_ie, false))
if (!handshake_util_ap_ie_matches(&msg2_rsne, authenticator_ie, false))
return false;
return true;
@ -674,7 +674,8 @@ static int ft_rx_associate(struct auth_proto *ap, const uint8_t *frame,
memcmp(msg4_rsne.pmkids, hs->pmk_r1_name, 16))
return -EBADMSG;
if (!handshake_util_ap_ie_matches(rsne, hs->authenticator_ie,
if (!handshake_util_ap_ie_matches(&msg4_rsne,
hs->authenticator_ie,
false))
return -EBADMSG;
} else {

73
src/handshake.c
View File

@ -759,90 +759,69 @@ void handshake_state_set_gtk(struct handshake_state *s, const uint8_t *key,
* results vs the RSN/WPA IE obtained as part of the 4-way handshake. If they
* don't match, the EAPoL packet must be silently discarded.
*/
bool handshake_util_ap_ie_matches(const uint8_t *msg_ie,
bool handshake_util_ap_ie_matches(const struct ie_rsn_info *msg_info,
const uint8_t *scan_ie, bool is_wpa)
{
struct ie_rsn_info msg_info;
struct ie_rsn_info scan_info;
int r;
/*
* First check that the sizes match, if they do, run a bitwise
* comparison.
*/
if (msg_ie[1] == scan_ie[1] &&
!memcmp(msg_ie + 2, scan_ie + 2, msg_ie[1]))
return true;
if (!is_wpa)
r = ie_parse_rsne_from_data(scan_ie,
scan_ie[1] + 2, &scan_info);
else
r = ie_parse_wpa_from_data(scan_ie, scan_ie[1] + 2, &scan_info);
/*
* Otherwise we have to parse the IEs and compare the individual
* fields
*/
if (!is_wpa) {
if (ie_parse_rsne_from_data(msg_ie, msg_ie[1] + 2,
&msg_info) < 0)
return false;
if (ie_parse_rsne_from_data(scan_ie, scan_ie[1] + 2,
&scan_info) < 0)
return false;
} else {
if (ie_parse_wpa_from_data(msg_ie, msg_ie[1] + 2,
&msg_info) < 0)
return false;
if (ie_parse_wpa_from_data(scan_ie, scan_ie[1] + 2,
&scan_info) < 0)
return false;
}
if (msg_info.group_cipher != scan_info.group_cipher)
if (r < 0)
return false;
if (msg_info.pairwise_ciphers != scan_info.pairwise_ciphers)
if (msg_info->group_cipher != scan_info.group_cipher)
return false;
if (msg_info.akm_suites != scan_info.akm_suites)
if (msg_info->pairwise_ciphers != scan_info.pairwise_ciphers)
return false;
if (msg_info.preauthentication != scan_info.preauthentication)
if (msg_info->akm_suites != scan_info.akm_suites)
return false;
if (msg_info.no_pairwise != scan_info.no_pairwise)
if (msg_info->preauthentication != scan_info.preauthentication)
return false;
if (msg_info.ptksa_replay_counter != scan_info.ptksa_replay_counter)
if (msg_info->no_pairwise != scan_info.no_pairwise)
return false;
if (msg_info.gtksa_replay_counter != scan_info.gtksa_replay_counter)
if (msg_info->ptksa_replay_counter != scan_info.ptksa_replay_counter)
return false;
if (msg_info.mfpr != scan_info.mfpr)
if (msg_info->gtksa_replay_counter != scan_info.gtksa_replay_counter)
return false;
if (msg_info.mfpc != scan_info.mfpc)
if (msg_info->mfpr != scan_info.mfpr)
return false;
if (msg_info.peerkey_enabled != scan_info.peerkey_enabled)
if (msg_info->mfpc != scan_info.mfpc)
return false;
if (msg_info.spp_a_msdu_capable != scan_info.spp_a_msdu_capable)
if (msg_info->peerkey_enabled != scan_info.peerkey_enabled)
return false;
if (msg_info.spp_a_msdu_required != scan_info.spp_a_msdu_required)
if (msg_info->spp_a_msdu_capable != scan_info.spp_a_msdu_capable)
return false;
if (msg_info.pbac != scan_info.pbac)
if (msg_info->spp_a_msdu_required != scan_info.spp_a_msdu_required)
return false;
if (msg_info.extended_key_id != scan_info.extended_key_id)
if (msg_info->pbac != scan_info.pbac)
return false;
if (msg_info.ocvc != scan_info.ocvc)
if (msg_info->extended_key_id != scan_info.extended_key_id)
return false;
if (msg_info->ocvc != scan_info.ocvc)
return false;
/* We don't check the PMKIDs since these might actually be different */
if (msg_info.group_management_cipher !=
if (msg_info->group_management_cipher !=
scan_info.group_management_cipher)
return false;

2
src/handshake.h
View File

@ -242,7 +242,7 @@ bool handshake_decode_fte_key(struct handshake_state *s, const uint8_t *wrapped,
void handshake_state_set_gtk(struct handshake_state *s, const uint8_t *key,
unsigned int key_index, const uint8_t *rsc);
bool handshake_util_ap_ie_matches(const uint8_t *msg_ie,
bool handshake_util_ap_ie_matches(const struct ie_rsn_info *msg_info,
const uint8_t *scan_ie, bool is_wpa);
const uint8_t *handshake_util_find_kde(enum handshake_kde selector,