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Android wpa_supplicant 四次握手 流程分析
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记录wpa_supplicant四次握手的过程。
相关log：https://www.cnblogs.com/helloworldtoyou/p/9633603.html
接收到第一次握手，会设置一个认证超时时间，根据情况，设置成10s或者70s。
四次握手，如果出错，将会等待这个超时时间后，才会判断认证失败。然后从新连接。
wpa_supplicant/wpa_supplicant.c
void wpa_supplicant_rx_eapol(void *ctx, const u8 *src_addr,
const u8 *buf, size_t len)
{
struct wpa_supplicant *wpa_s = ctx;
// 接受到EAPOL帧
wpa_dbg(wpa_s, MSG_DEBUG, "RX EAPOL from " MACSTR, MAC2STR(src_addr));
wpa_hexdump(MSG_MSGDUMP, "RX EAPOL", buf, len);
#ifdef CONFIG_TESTING_OPTIONS
if (wpa_s->ignore_auth_resp) {
wpa_printf(MSG_INFO, "RX EAPOL - ignore_auth_resp active!");
return;
}
#endif /* CONFIG_TESTING_OPTIONS */
#ifdef CONFIG_PEERKEY
if (wpa_s->wpa_state > WPA_ASSOCIATED && wpa_s->current_ssid &&
wpa_s->current_ssid->peerkey &&
!(wpa_s->drv_flags & WPA_DRIVER_FLAGS_4WAY_HANDSHAKE) &&
wpa_sm_rx_eapol_peerkey(wpa_s->wpa, src_addr, buf, len) == 1) {
wpa_dbg(wpa_s, MSG_DEBUG, "RSN: Processed PeerKey EAPOL-Key");
return;
}
#endif /* CONFIG_PEERKEY */
if (wpa_s->wpa_state < WPA_ASSOCIATED ||
(wpa_s->last_eapol_matches_bssid &&
#ifdef CONFIG_AP
!wpa_s->ap_iface &&
#endif /* CONFIG_AP */
os_memcmp(src_addr, wpa_s->bssid, ETH_ALEN) != 0)) {
/*
* There is possible race condition between receiving the
* association event and the EAPOL frame since they are coming
* through different paths from the driver. In order to avoid
* issues in trying to process the EAPOL frame before receiving
* association information, lets queue it for processing until
* the association event is received. This may also be needed in
* driver-based roaming case, so also use src_addr != BSSID as a
* trigger if we have previously confirmed that the
* Authenticator uses BSSID as the src_addr (which is not the
* case with wired IEEE 802.1X).
*/
wpa_dbg(wpa_s, MSG_DEBUG, "Not associated - Delay processing "
"of received EAPOL frame (state=%s bssid=" MACSTR ")",
wpa_supplicant_state_txt(wpa_s->wpa_state),
MAC2STR(wpa_s->bssid));
wpabuf_free(wpa_s->pending_eapol_rx);
wpa_s->pending_eapol_rx = wpabuf_alloc_copy(buf, len);
if (wpa_s->pending_eapol_rx) {
os_get_reltime(&wpa_s->pending_eapol_rx_time);
os_memcpy(wpa_s->pending_eapol_rx_src, src_addr,
ETH_ALEN);
}
return;
}
wpa_s->last_eapol_matches_bssid =
os_memcmp(src_addr, wpa_s->bssid, ETH_ALEN) == 0;
#ifdef CONFIG_AP
if (wpa_s->ap_iface) {
wpa_supplicant_ap_rx_eapol(wpa_s, src_addr, buf, len);
return;
}
#endif /* CONFIG_AP */
// 没有配置密钥，退出
if (wpa_s->key_mgmt == WPA_KEY_MGMT_NONE) {
wpa_dbg(wpa_s, MSG_DEBUG, "Ignored received EAPOL frame since "
"no key management is configured");
return;
}
// 第一次收到EAPOL帧，设置认证超时时间，
if (wpa_s->eapol_received == 0 &&
(!(wpa_s->drv_flags & WPA_DRIVER_FLAGS_4WAY_HANDSHAKE) ||
!wpa_key_mgmt_wpa_psk(wpa_s->key_mgmt) ||
wpa_s->wpa_state != WPA_COMPLETED) &&
(wpa_s->current_ssid == NULL ||
wpa_s->current_ssid->mode != IEEE80211_MODE_IBSS)) {
/* Timeout for completing IEEE 802.1X and WPA authentication */
int timeout = 10; // 认证超时时间10s
if (wpa_key_mgmt_wpa_ieee8021x(wpa_s->key_mgmt) ||
wpa_s->key_mgmt == WPA_KEY_MGMT_IEEE8021X_NO_WPA ||
wpa_s->key_mgmt == WPA_KEY_MGMT_WPS) {
/* Use longer timeout for IEEE 802.1X/EAP */
timeout = 70; // 802.1X/EAP认证超时时间设置成70s
}
// WPS相关设置
#ifdef CONFIG_WPS
if (wpa_s->current_ssid && wpa_s->current_bss &&
(wpa_s->current_ssid->key_mgmt & WPA_KEY_MGMT_WPS) &&
eap_is_wps_pin_enrollee(&wpa_s->current_ssid->eap)) {
/*
* Use shorter timeout if going through WPS AP iteration
* for PIN config method with an AP that does not
* advertise Selected Registrar.
*/
struct wpabuf *wps_ie;
wps_ie = wpa_bss_get_vendor_ie_multi(
wpa_s->current_bss, WPS_IE_VENDOR_TYPE);
if (wps_ie &&
!wps_is_addr_authorized(wps_ie, wpa_s->own_addr, 1))
timeout = 10;
else {
/* We should apply a flexible timeout value,
* becasue some AP which send M2D MSG
* need more time to complete EAP auth,such as Marvell.
* */
timeout = 70;
}
wpabuf_free(wps_ie);
}
#endif /* CONFIG_WPS */
wpa_supplicant_req_auth_timeout(wpa_s, timeout, 0); // 设置认证超时，10s或者70s
}
wpa_s->eapol_received++; // 接受到的EAPOL计数加一
if (wpa_s->countermeasures) {
wpa_msg(wpa_s, MSG_INFO, "WPA: Countermeasures - dropped "
"EAPOL packet");
return;
}
#ifdef CONFIG_IBSS_RSN
if (wpa_s->current_ssid &&
wpa_s->current_ssid->mode == WPAS_MODE_IBSS) {
ibss_rsn_rx_eapol(wpa_s->ibss_rsn, src_addr, buf, len);
return;
}
#endif /* CONFIG_IBSS_RSN */
/* Source address of the incoming EAPOL frame could be compared to the
* current BSSID. However, it is possible that a centralized
* Authenticator could be using another MAC address than the BSSID of
* an AP, so just allow any address to be used for now. The replies are
* still sent to the current BSSID (if available), though. */
os_memcpy(wpa_s->last_eapol_src, src_addr, ETH_ALEN);
if (!wpa_key_mgmt_wpa_psk(wpa_s->key_mgmt) &&
wpa_s->key_mgmt != WPA_KEY_MGMT_OWE &&
wpa_s->key_mgmt != WPA_KEY_MGMT_DPP &&
eapol_sm_rx_eapol(wpa_s->eapol, src_addr, buf, len) > 0)
return;
wpa_drv_poll(wpa_s);
if (!(wpa_s->drv_flags & WPA_DRIVER_FLAGS_4WAY_HANDSHAKE))
wpa_sm_rx_eapol(wpa_s->wpa, src_addr, buf, len); // 处理接受的EAPOL帧
else if (wpa_key_mgmt_wpa_ieee8021x(wpa_s->key_mgmt)) {
/*
* Set portValid = TRUE here since we are going to skip 4-way
* handshake processing which would normally set portValid. We
* need this to allow the EAPOL state machines to be completed
* without going through EAPOL-Key handshake.
*/
eapol_sm_notify_portValid(wpa_s->eapol, TRUE);
}
}
src/rsn_supp/wpa.c
int wpa_sm_rx_eapol(struct wpa_sm *sm, const u8 *src_addr,
const u8 *buf, size_t len)
{
各种帧内容判断
...
if (key_info & WPA_KEY_INFO_KEY_TYPE) {
if (key_info & WPA_KEY_INFO_KEY_INDEX_MASK) {
wpa_msg(sm->ctx->msg_ctx, MSG_WARNING,
"WPA: Ignored EAPOL-Key (Pairwise) with "
"non-zero key index");
goto out;
}
if (peerkey) {
/* PeerKey 4-Way Handshake */
peerkey_rx_eapol_4way(sm, peerkey, key, key_info, ver,
key_data, key_data_len);
} else if (key_info & (WPA_KEY_INFO_MIC |
WPA_KEY_INFO_ENCR_KEY_DATA)) {
/* 3/4 4-Way Handshake */ // 第三次握手
wpa_supplicant_process_3_of_4(sm, key, ver, key_data,
key_data_len);
} else {
/* 1/4 4-Way Handshake */ // 第一次握手
wpa_supplicant_process_1_of_4(sm, src_addr, key,
ver, key_data,
key_data_len);
}
} else if (key_info & WPA_KEY_INFO_SMK_MESSAGE) {
/* PeerKey SMK Handshake */
peerkey_rx_eapol_smk(sm, src_addr, key, key_data, key_data_len,
key_info, ver);
} else {
if ((mic_len && (key_info & WPA_KEY_INFO_MIC)) ||
(!mic_len && (key_info & WPA_KEY_INFO_ENCR_KEY_DATA))) {
/* 1/2 Group Key Handshake */
wpa_supplicant_process_1_of_2(sm, src_addr, key,
key_data, key_data_len,
ver);
} else {
wpa_msg(sm->ctx->msg_ctx, MSG_WARNING,
"WPA: EAPOL-Key (Group) without Mic/Encr bit - "
"dropped");
}
}
...
}
static void wpa_supplicant_process_1_of_4(struct wpa_sm *sm,
const unsigned char *src_addr,
const struct wpa_eapol_key *key,
u16 ver, const u8 *key_data,
size_t key_data_len)
{
struct wpa_eapol_ie_parse ie;
struct wpa_ptk *ptk;
int res;
u8 *kde, *kde_buf = NULL;
size_t kde_len;
if (wpa_sm_get_network_ctx(sm) == NULL) {
wpa_msg(sm->ctx->msg_ctx, MSG_WARNING, "WPA: No SSID info "
"found (msg 1 of 4)");
return;
}
wpa_sm_set_state(sm, WPA_4WAY_HANDSHAKE);
wpa_dbg(sm->ctx->msg_ctx, MSG_DEBUG, "WPA: RX message 1 of 4-Way "
"Handshake from " MACSTR " (ver=%d)", MAC2STR(src_addr), ver);
os_memset(&ie, 0, sizeof(ie));
if (sm->proto == WPA_PROTO_RSN || sm->proto == WPA_PROTO_OSEN) {
/* RSN: msg 1/4 should contain PMKID for the selected PMK */
wpa_hexdump(MSG_DEBUG, "RSN: msg 1/4 key data",
key_data, key_data_len);
if (wpa_supplicant_parse_ies(key_data, key_data_len, &ie) < 0)
goto failed;
if (ie.pmkid) {
wpa_hexdump(MSG_DEBUG, "RSN: PMKID from "
"Authenticator", ie.pmkid, PMKID_LEN);
}
}
res = wpa_supplicant_get_pmk(sm, src_addr, ie.pmkid);
if (res == -2) {
wpa_dbg(sm->ctx->msg_ctx, MSG_DEBUG, "RSN: Do not reply to "
"msg 1/4 - requesting full EAP authentication");
return;
}
if (res)
goto failed;
if (sm->renew_snonce) {
if (random_get_bytes(sm->snonce, WPA_NONCE_LEN)) {
wpa_msg(sm->ctx->msg_ctx, MSG_WARNING,
"WPA: Failed to get random data for SNonce");
goto failed;
}
sm->renew_snonce = 0;
wpa_hexdump(MSG_DEBUG, "WPA: Renewed SNonce",
sm->snonce, WPA_NONCE_LEN);
}
/* Calculate PTK which will be stored as a temporary PTK until it has
* been verified when processing message 3/4. */
ptk = &sm->tptk;
wpa_derive_ptk(sm, src_addr, key, ptk);
if (sm->pairwise_cipher == WPA_CIPHER_TKIP) {
u8 buf[8];
/* Supplicant: swap tx/rx Mic keys */
os_memcpy(buf, &ptk->tk[16], 8);
os_memcpy(&ptk->tk[16], &ptk->tk[24], 8);
os_memcpy(&ptk->tk[24], buf, 8);
os_memset(buf, 0, sizeof(buf));
}
sm->tptk_set = 1;
kde = sm->assoc_wpa_ie;
kde_len = sm->assoc_wpa_ie_len;
...
// 发送第二次握手的包
if (wpa_supplicant_send_2_of_4(sm, sm->bssid, key, ver, sm->snonce,
kde, kde_len, ptk) < 0)
goto failed;
os_free(kde_buf);
os_memcpy(sm->anonce, key->key_nonce, WPA_NONCE_LEN);
return;
failed:
os_free(kde_buf);
wpa_sm_deauthenticate(sm, WLAN_REASON_UNSPECIFIED);
}
Liutao
2018-11-22
