跟一下wpa_supplicant(3-2) connect AP

转：http://blog.chinaunix.net/uid-20514606-id-3260320.html

接前面(3-1)继续:

 

5. 接分支4.
authenticate response 来了
和前面一样:
wpa_driver_nl80211_event_receive到
=> process_event
   收到 NL80211_CMD_AUTHENTICATE=37
   ==> mlme_event (37)
       ===> mlme_event_auth
            authenticate response 管理帧中的AP mac 是我们感兴趣的,
     收了它,放wpa_driver_nl80211_data 的auth_bssid
            并放到wpa_event_data->auth_info->peer 
     ====> wpa_supplicant_event(drv->ctx, EVENT_AUTH, &event);
           Event 11 received on interface wlan0 被扔出来
          =====> sme_event_auth(wpa_s, data);
                       紧接着
         D/wpa_supplicant( 2129): SME: Authentication response:
                        peer=00:1f:33:b9:5d:e0 auth_type=0 status_code=0
                       被扔出来
                       ======> eloop_cancel_timeout(sme_auth_timer, 
                     wpa_s, NULL);
                               取消auth 失败的警戒,可以进城了
                       ======> sme_associate(wpa_s, ssid->mode, 
                  data->auth.peer, data->auth.auth_type);
    启动关联
                               =======>wpa_supplicant_set_state(wpa_s, 
                    WPA_ASSOCIATING);
                               ========> wpa_s->new_connection = 1;
                               ========> wpa_drv_set_operstate(wpa_s, 0);
                   /* 设置到IF_OPER_DORMANT */
                               ========> wpa_s->wpa_state = state;
                               ========> wpas_notify_state_changed(wpa_s, 
             wpa_s->wpa_state, old_state); 
        如果 oldstate  不同情况下执行
                               =======> 设置参数等,ie 
                               =======> wpa_drv_associate(wpa_s, &params) 
                                wpa_driver_nl80211_associate  driver interface
           通过netlink 给dirver 发assoc request
                                wpa_printf(MSG_DEBUG, "nl80211: 
       Association request send "  "successfully");
                                发完了应该,别忘警戒下:
                       =======> eloop_register_timeout(SME_ASSOC_TIMEOUT, 
                                 0, sme_assoc_timer, wpa_s,  NULL);
                                 /* 关联超时失败处理*/
        
                             接下来到分支6.

6. 接分支5.
38 event 来了!
wpa_driver_nl80211_event_receive到
=> process_event
   ==> mlme_event (38= NL80211_CMD_ASSOCIATE)
       asscoicate response 来了
      ===> mlme_event_assoc(drv, nla_data(frame),
             nla_len(frame));
      这里的 frame 应该就是关联响应帧
             去读下rp frame state 判断response为成功
          ====> drv->associated = 1;
          ====> 获得resp 中的IE们 到 event.assoc_info.resp_ies
          ====> event.assoc_info.freq = drv->assoc_freq;
        关联时的频率放到 struct assoc_info
         有了IE,就象口袋有钱,可以来事了,EVENT_ASSOC发出去
          ====> wpa_supplicant_event(drv->ctx, EVENT_ASSOC,&event);
               =====> wpa_supplicant_event_assoc(wpa_s, data);
                     ======> wpa_supplicant_event_associnfo
                            获取AP 的assoc info!
       就是挖掘前面说的已经存到event.assoc_info的resp ie
       其中如果挖到PMKID,是要注意
       去call wpa_find_assoc_pmkid
       干什么? 如果忘记了,到第1篇搜索:
       '成对主蜜钥安全关联'字样,我就不讲了

                     ======> wpa_supplicant_set_state(wpa_s, WPA_ASSOCIATED);
                             State: ASSOCIATING -> ASSOCIATED
                     ======> wpa_clear_keys (clear driver config key)
                     ======> wpa_supplicant_select_config
              我们设置为AP_SCAN =1(让wpa_supplciant选择AP)
       所以它什么也不做,return
                     ======> wpa_sm_notify_assoc(wpa_s->wpa, bssid);
                            WPA state machine 的rx_replay_counter_set 清0,
       的renew_snonce 置1
       比较下是否是在preauth的ap 的mac,是的话就deinit它
       最后清下wap state machine 的 old PTK
       这么做是因为人家IEEE 802.11协议8.4.10部分说了
                            Delete PTK SA on (re)association if this is not 
          part of a Fast BSS Transition.
                            
                            PTK 有两种格式,TKIP,和CCMP

                     ======> eapol_sm_notify_portEnabled(wpa_s->eapol, FALSE);
                     ======>eapol_sm_notify_portValid(wpa_s->eapol, FALSE);
       ======> if (wpa_key_mgmt_wpa_psk(wpa_s->key_mgmt) || 
                                   ft_completed)
                          eapol_sm_notify_eap_success(wpa_s->eapol,
                                FALSE);   
                      到这里PAE还没变化,下面就要变了
                     ======> eapol_sm_notify_portEnabled(wpa_s->eapol, TRUE);
                            portEnabled=1
       PAE状态要发生变化了,从disconnect 变到connecting
                            这个disconnect是在 eapol_sm_init,开始设置的
       之后一直保持该状态
       EAP状态一直为disable,因为我们是WPA-psk,所以
       没有EAP,他就一直处于disable

                     ======> /* Timeout for receiving the first
                  EAPOL packet */
                       wpa_supplicant_req_auth_timeout(wpa_s, 10, 0);
         /* 10  秒后没收到第1个 eapol packet 后 ,
         就处理auth 失败 */
                     ======> wpa_supplicant_cancel_sched_scan(wpa_s);
       /* 要做正事了, 就先停sched scan ,scan  */
                  wpa_supplicant_cancel_scan(wpa_s);

                     ======> wpa_supplicant_event_assoc中
                接下来的部分不会执行到

到这里已经关联已经完成,在AP 发来EAPOL frame 前,我们会收到
NL80211_CMD_CONNECT 通知,根据cmd注释,可以了解该命令是在不分开进行认证
和关联的情况下,来请求连接到一个指点网络的,连接完成会收到NL80211_CMD_CONNECT
的response,目前的driver capa里设置了WPA_DRIVER_FLAGS_SME,表示driver 支持
auth 和associate 分开的命令,所以能收到NL80211_CMD_CONNECT,但不处理
为什么呢? 注释里已经写了,为了避免2次报告关联事件,引起核心代码混乱
/** Avoid reporting two association events that would confuse
 * the core code.
 */

                   进入7. 继续

7. 前面6.中完成asscicate 后,讲过就会等待EAPOL FRAME到来
  在wpa init 中 wpa_supplicant_driver_init 会注册 l2 rx callback
wpa_s->l2 = l2_packet_init(wpa_s->ifname,
     wpa_drv_get_mac_addr(wpa_s),
     ETH_P_EAPOL,
     wpa_supplicant_rx_eapol, wpa_s, 0);

可以看出收到l2 packet 后call back wpa_supplicant_rx_eapol,就从它开始
=> wpa_supplicant_rx_eapol:
   ==> wpa_supplicant_req_auth_timeout(wpa_s,
              (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) ? 70 : 10, 0);
        和前面associate最后设置的10s timeout 一样,这里只是收到
 第1个,reset 下一次认证超时为10s

   ==> wpa_s->eapol_received++;  是第1次,eapol_received++ 后等于1
   ==> 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);
              该函数处理收到的 EAPOL frame
              分析可得:
                * type =2 时 EAPOL-Key
  * key_info =0x8a
     (ver=2 keyidx=0 rsvd=0 Pairwise Ack)
  * key length =16, key data lenght 22
key_info 各bit 所代表的内容在:
wpa_comm.h中定义如下:

点击(此处)折叠或打开

1. /* IEEE 802.11, 8.5.2 EAPOL-Key frames */
   
2. #define WPA_KEY_INFO_TYPE_MASK ((u16) (BIT(0) | BIT(1) | BIT(2)))
   
3. #define WPA_KEY_INFO_TYPE_HMAC_MD5_RC4 BIT(0)
   
4. #define WPA_KEY_INFO_TYPE_HMAC_SHA1_AES BIT(1)
   
5. #define WPA_KEY_INFO_TYPE_AES_128_CMAC 3
   
6. #define WPA_KEY_INFO_KEY_TYPE BIT(3) /* 1 = Pairwise, 0 = Group key */
   
7. /* bit4..5 is used in WPA, but is reserved in IEEE 802.11i/RSN */
   
8. #define WPA_KEY_INFO_KEY_INDEX_MASK (BIT(4) | BIT(5))
   
9. #define WPA_KEY_INFO_KEY_INDEX_SHIFT 4
   
10. #define WPA_KEY_INFO_INSTALL BIT(6) /* pairwise */
    
11. #define WPA_KEY_INFO_TXRX BIT(6) /* group */
    
12. #define WPA_KEY_INFO_ACK BIT(7)
    
13. #define WPA_KEY_INFO_MIC BIT(8)
    
14. #define WPA_KEY_INFO_SECURE BIT(9)
    
15. #define WPA_KEY_INFO_ERROR BIT(10)
    
16. #define WPA_KEY_INFO_REQUEST BIT(11)
    
17. #define WPA_KEY_INFO_ENCR_KEY_DATA BIT(12) /* IEEE 802.11i/RSN only */
    
18. #define WPA_KEY_INFO_SMK_MESSAGE BIT(13)

第1个发过来的eapol frame 表示4次握手的第1次握手已经开始了!!!

   ==> 接下来就是部分4 way handle 的代码,直接贴上:

点击(此处)折叠或打开

1. if (key_info & WPA_KEY_INFO_KEY_TYPE) { 
   
2.      /* 走到这里, WPA_KEY_INFO_KEY_TYPE ,pairwise ,or group key !!!*/
   
3.    if (key_info & WPA_KEY_INFO_KEY_INDEX_MASK) {
   
4.  wpa_msg(sm->ctx->msg_ctx, MSG_WARNING,
   
5.  "WPA: Ignored EAPOL-Key (Pairwise) with "
   
6.  "non-zero key index");
   
7.  goto out;
   
8.    }
   
9.    if (peerkey) { /* 如果4way 的第1次没有peerkey */
   
10.       /* PeerKey 4-Way Handshake */
    
11.   peerkey_rx_eapol_4way(sm, peerkey, key, key_info, ver);
    
12.    } else if (key_info & WPA_KEY_INFO_MIC) {
    
13.      /* 3/4 4-Way Handshake */
    
14.      wpa_supplicant_process_3_of_4(sm, key, ver);
    
15.    } else {
    
16.        /* 1/4 4-Way Handshake */
    
17.  wpa_supplicant_process_1_of_4(sm, src_addr, key, ver);
    
18.    }
    
19. } else if (key_info & WPA_KEY_INFO_SMK_MESSAGE) {
    
20.      /* PeerKey SMK Handshake */
    
21.      peerkey_rx_eapol_smk(sm, src_addr, key, extra_len, key_info,ver);
    
22. } else {
    
23.  if (key_info & WPA_KEY_INFO_MIC) {
    
24.  /* 1/2 Group Key Handshake */
    
25.  wpa_supplicant_process_1_of_2(sm, src_addr, key, extra_len, ver);
    
26.   } else {
    
27.          wpa_msg(sm->ctx->msg_ctx, MSG_WARNING,
    
28.         "WPA: EAPOL-Key (Group) without Mic bit - "
    
29.   "dropped");
    
30.  }
    
31. }

 

wpa_supplicant_process_1_of_4(sm, src_addr, key, ver);
wpa_supplicant_process_3_of_4(sm, key, ver);
是我们关心的

为什么没有0_of_4, 2_of_4? 不是没有,4次握手的第1,3次都在AP端处理
我们不管了,所以目前阶段,直接跑到1_fo_4,处理如下
 
       ===> wpa_supplicant_process_1_of_4(sm, src_addr, key,  ver);
            ====> wpa_sm_set_state(sm, WPA_4WAY_HANDSHAKE); 
                  wap state 变化了 , ASSOCIATED -> 4WAY_HANDSHAKE
            ====> wpa_supplicant_parse_ies(_buf, len, &ie);
                  将buf 内容解析到 struct wpa_eapol_ie_parse
                  包括我们下面要用的pmkid 
            ====> wpa_supplicant_get_pmk(sm, src_addr, ie.pmkid);
       如果pmksa cashe 不空,
       先从PMKSA cache中根据传来的ie.pmkid 去匹配
       然后获得PMK,它是计算 PTK必须的,但现在cur_pmksa
       为空,那如何获得pmk ,其实上面已经设置了,
       在wpa_supplicant_associate 的
       最后 wpa_sm_set_pmk 将预共享密钥PSK,copy到
        struct wpa_sm->pmk
                    
            ====> ptk = &sm->tptk;
            ====> wpa_derive_ptk(sm, src_addr, key, ptk);
                  计算方法:
               wpa_pmk_to_ptk(sm->pmk, sm->pmk_len, "Pairwise key expansion",
                  sm->own_addr, sm->bssid, sm->snonce, key->key_nonce,
                  (u8 *) ptk, ptk_len,
                  wpa_key_mgmt_sha256(sm->key_mgmt));
                  公式:
                  * PTK = PRF-X(PMK, "Pairwise key expansion",
                  *             Min(AA, SA) || Max(AA, SA) ||
                  *             Min(ANonce, SNonce) || Max(ANonce, SNonce))

            ====> wpa_supplicant_send_2_of_4(sm, sm->bssid, key, ver, 
         sm->snonce, sm->assoc_wpa_ie, sm->assoc_wpa_ie_len, ptk)
                  =====> wpa_sm_alloc_eapol(sm, IEEE802_1X_TYPE_EAPOL_KEY, 
            NULL, sizeof(*reply) + wpa_ie_len, &rlen, 
     (void *) &reply);
                       os_memcpy(reply->key_nonce, nonce, WPA_NONCE_LEN);
                       wpa_eapol_key_send(sm, ptk->kck, ver, dst, ETH_P_EAPOL,  
             rbuf, rlen, reply->key_mic);
                      /* 发出去,然后等下次 wpa_supplicant_rx_eapol*/

                   接下来到8.

 

8.
l2 packet 又来了
=> wpa_supplicant_rx_eapol:
   ==> 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);
        该函数处理收到的 EAPOL frame
        分析可得:
        * type =2 时 EAPOL-Key
 * key_info =0x13ca
    (ver=2 keyidx=0 rsvd=0 Pairwise Install Ack MIC Secure Encr)
 * key length =16, key data lenght 80
   ==>  else if (key_info & WPA_KEY_INFO_MIC) { 
         /*wpa_commom.h #define WPA_KEY_INFO_MIC BIT(8)*/
  /* 3/4 4-Way Handshake */
   ==>  wpa_supplicant_process_3_of_4(sm, key, ver); 
       其中key 就是 EAPOL-KEY 内容
struct wpa_eapol_key {   /* EAPOL-KEY 结构!!! */
 u8 type;
 /* Note: key_info, key_length, and key_data_length are unaligned */
 u8 key_info[2]; /* big endian */
 u8 key_length[2]; /* big endian */
 u8 replay_counter[WPA_REPLAY_COUNTER_LEN];
 u8 key_nonce[WPA_NONCE_LEN];
 u8 key_iv[16];
 u8 key_rsc[WPA_KEY_RSC_LEN];
 u8 key_id[8]; /* Reserved in IEEE 802.11i/RSN */
 u8 key_mic[16];
 u8 key_data_length[2]; /* big endian */
 /* followed by key_data_length bytes of key_data */
} STRUCT_PACKED;
        下面对eapol key data 部分进行处理,将获得的ie,放到
 struct wpa_eapol_ie_parse 
        ===> pos = (const u8 *) (key + 1);  eapol key 后就是ie
             len = WPA_GET_BE16(key->key_data_length);    
             wpa_supplicant_parse_ies(pos, len, &ie);
                     
        ===> wpa_supplicant_send_4_of_4(sm, sm->bssid, key, ver, key_info,
                      NULL, 0, &sm->ptk)
             ====> wpa_sm_alloc_eapol ,init epaol packet
                   =====> wpa_eapol_key_send(sm, ptk->kck, ver, dst, 
               ETH_P_EAPOL,  rbuf, rlen, reply->key_mic);
        一个ACK ,没有什么实质内容,也不加密
        ===> wpa_supplicant_install_ptk (struct wpa_sm *sm, 
                   const struct wpa_eapol_key *key)
              ====> 设置driver key !!! wpa_sm_set_key
                    wpa_driver_nl80211_set_key  (nl80211 driver)
                    wap_supplicant 的 终极目标,终于看到了!
      PTK 安装好了,稍侯片刻,马上结束

        ===> eapol_sm_notify_portValid(sm->eapol, TRUE);
               前面associate 成功后 PAE 处于 CONNECTING
               到这里 portValid = TRUE, 但PAE 状态没发生变化

        ===> wpa_sm_set_state(sm, WPA_GROUP_HANDSHAKE);
             WPA State 从 4WAY_HANDSHAKE -> GROUP_HANDSHAKE

        ===> wpa_supplicant_pairwise_gtk(sm, key, ie.gtk,ie.gtk_len, 
                                    key_info)
             从代码中看加密的GTK 3/4 way  中的IE部分就发来了!!!
             wpa_supplicant_check_group_cipher
      用双方都已知道的PTK 的 EPAOL KEK 加的密 )现在解开来
             ====> wpa_supplicant_install_gtk(sm, &gd, key->key_rsc) 
            安装组密码
             ====> wpa_supplicant_key_neg_complete   key 协商完成
                   =====> wpa_sm_cancel_auth_timeout(sm);
            将前面设置的认证超时处理取消
                   =====> wpa_sm_set_state(sm, WPA_COMPLETED);
             wpa state 从 GROUP_HANDSHAKE -> COMPLETED
                   =====> if (secure) {
                            ......
                     eapol_sm_notify_portValid(sm->eapol, TRUE);
                     eapol_sm_notify_eap_success(sm->eapol, TRUE);
       PAE 进入AUTHENTICATING
       BE  进入success
       EAP 返回diable
       PAE 最终进入AUTHENTICATED
         然后eapol_sm_set_port_authorized
                              然后wpa_supplicant_port_cb
         然后wpa_drv_set_supp_port
         设置driver NL80211_STA_FLAG_AUTHORIZED
到此为止,认证完成

整个过程的WPA State变化如下:
(wpa_supplicant)
DISCONNECTED    -> SCANNING
SCANNING        -> AUTHENTICATING      (802.11身份认证 )
AUTHENTICATING  -> ASSOCIATING
SCANNING        -> ASSOCIATING 
ASSOCIATING     -> ASSOCIATED     
      
ASSOCIATED      -> 4WAY_HANDSHAKE
4WAY_HANDSHAKE  -> 4WAY_HANDSHAKE
4WAY_HANDSHAKE  -> GROUP_HANDSHAKE
GROUP_HANDSHAKE -> COMPLETED

PAE supplicant 端状态图

 

 

结束