wifidog源码分析 - 用户连接过程

引言

　　之前的文章已经描述wifidog大概的一个工作流程，这里我们具体说说wifidog是怎么把一个新用户重定向到认证服务器中的，它又是怎么对一个已认证的用户实行放行操作的。我们已经知道wifidog在启动时会删除iptables中mangle、nat、filter表中的所有规则，并在这三个表中添加wifidog自己的规则，其规则简单来说就是将网关80端口重定向到指定端口（默认为2060），禁止非认证用户连接外网（除认证服务器外）。当有新用户连接路由器上网时，wifidog会通过监听2060端口获取新用户的http报文，通过报文即可知道报文是否携带token进行认证，如果没有token，wifidog会返回一个重定向的http报文给新用户，用户则会跳转到认证服务器进行认证，当认证成功后，认真服务器又会对用户重定向到网关，并在重定向报文中添加关键路径"/wifidog/auth"和token，wifidog重新获取到用户的http报文，检测到包含关键路径"/wifidog/auth"后，会通过认证服务器验证token是否有效，有效则修改iptables放行此客户端。

 

main_loop

　　此函数几乎相当于我们写程序的main函数，主要功能都是在这里面实现的，函数主要实现了主循环，并启动了三个线程，这三个线程的功能具体见wifidog源码分析 - wifidog原理，在此函数最后主循环中会等待用户连接，新用户只要通过浏览器打开非认证服务器网页时主循环就会监听到，监听到后会启动一个处理线程。其流程为

• 设置程序启动时间
• 获取网关信息
• 绑定http端口（80重定向到了2060）
• 设置关键路径和404错误的回调函数
• 重新建立iptables规则
• 启动客户端检测线程 （稍后文章分析）
• 启动wdctrl交互线程 （稍后文章分析）
• 认证服务器心跳检测线程 （稍后文章分析）
• 循环等待用户http请求，为每个请求启动一个处理线程。（代码片段1.2 代码片段1.3 代码片段1.4）

　　代码片段1.1

  1 static void
  2 main_loop(void)
  3 {
  4     int result;
  5     pthread_t    tid;
  6     s_config *config = config_get_config();
  7     request *r;
  8     void **params;
  9 
 10     /* 设置启动时间 */
 11     if (!started_time) {
 12         debug(LOG_INFO, "Setting started_time");
 13         started_time = time(NULL);
 14     }
 15     else if (started_time < MINIMUM_STARTED_TIME) {
 16         debug(LOG_WARNING, "Detected possible clock skew - re-setting started_time");
 17         started_time = time(NULL);
 18     }
 19 
 20     /* 获取网关IP，失败退出程序 */
 21     if (!config->gw_address) {
 22         debug(LOG_DEBUG, "Finding IP address of %s", config->gw_interface);
 23         if ((config->gw_address = get_iface_ip(config->gw_interface)) == NULL) {
 24             debug(LOG_ERR, "Could not get IP address information of %s, exiting...", config->gw_interface);
 25             exit(1);
 26         }
 27         debug(LOG_DEBUG, "%s = %s", config->gw_interface, config->gw_address);
 28     }
 29 
 30     /* 获取网关ID，失败退出程序 */
 31     if (!config->gw_id) {
 32         debug(LOG_DEBUG, "Finding MAC address of %s", config->gw_interface);
 33         if ((config->gw_id = get_iface_mac(config->gw_interface)) == NULL) {
 34             debug(LOG_ERR, "Could not get MAC address information of %s, exiting...", config->gw_interface);
 35             exit(1);
 36         }
 37         debug(LOG_DEBUG, "%s = %s", config->gw_interface, config->gw_id);
 38     }
 39 
 40     /* 初始化监听网关2060端口的socket */
 41     debug(LOG_NOTICE, "Creating web server on %s:%d", config->gw_address, config->gw_port);
 42     
 43     if ((webserver = httpdCreate(config->gw_address, config->gw_port)) == NULL) {
 44         debug(LOG_ERR, "Could not create web server: %s", strerror(errno));
 45         exit(1);
 46     }
 47 
 48     debug(LOG_DEBUG, "Assigning callbacks to web server");
 49     /* 设置关键路径及其回调函数，在代码片段1.2中会使用到 */
 50     httpdAddCContent(webserver, "/", "wifidog", 0, NULL, http_callback_wifidog);
 51     httpdAddCContent(webserver, "/wifidog", "", 0, NULL, http_callback_wifidog);
 52     httpdAddCContent(webserver, "/wifidog", "about", 0, NULL, http_callback_about);
 53     httpdAddCContent(webserver, "/wifidog", "status", 0, NULL, http_callback_status);
 54     httpdAddCContent(webserver, "/wifidog", "auth", 0, NULL, http_callback_auth);
 55     /* 设置404错误回调函数，在里面实现了重定向至认证服务器 */
 56     httpdAddC404Content(webserver, http_callback_404);
 57 
 58     /* 清除iptables规则 */
 59     fw_destroy();
 60     /* 重新设置iptables规则 */
 61     if (!fw_init()) {
 62         debug(LOG_ERR, "FATAL: Failed to initialize firewall");
 63         exit(1);
 64     }
 65 
 66     /* 客户端检测线程 */
 67     result = pthread_create(&tid_fw_counter, NULL, (void *)thread_client_timeout_check, NULL);
 68     if (result != 0) {
 69         debug(LOG_ERR, "FATAL: Failed to create a new thread (fw_counter) - exiting");
 70         termination_handler(0);
 71     }
 72     pthread_detach(tid_fw_counter);
 73 
 74     /* wdctrl交互线程 */
 75     result = pthread_create(&tid, NULL, (void *)thread_wdctl, (void *)safe_strdup(config->wdctl_sock));
 76     if (result != 0) {
 77         debug(LOG_ERR, "FATAL: Failed to create a new thread (wdctl) - exiting");
 78         termination_handler(0);
 79     }
 80     pthread_detach(tid);
 81     
 82     /* 认证服务器心跳检测线程 */
 83     result = pthread_create(&tid_ping, NULL, (void *)thread_ping, NULL);
 84     if (result != 0) {
 85         debug(LOG_ERR, "FATAL: Failed to create a new thread (ping) - exiting");
 86         termination_handler(0);
 87     }
 88     pthread_detach(tid_ping);
 89     
 90     debug(LOG_NOTICE, "Waiting for connections");
 91     while(1) {
 92         /* 监听2060端口等待用户http请求 */
 93         r = httpdGetConnection(webserver, NULL);
 94 
 95         /* 错误处理 */
 96         if (webserver->lastError == -1) {
 97             /* Interrupted system call */
 98             continue; /* restart loop */
 99         }
100         else if (webserver->lastError < -1) {
101             debug(LOG_ERR, "FATAL: httpdGetConnection returned unexpected value %d, exiting.", webserver->lastError);
102             termination_handler(0);
103         }
104         else if (r != NULL) {
105             /* 用户http请求接收成功 */
106             debug(LOG_INFO, "Received connection from %s, spawning worker thread", r->clientAddr);
107             params = safe_malloc(2 * sizeof(void *));
108             *params = webserver;
109             *(params + 1) = r;
110 
111             /* 开启http请求处理线程 */
112             result = pthread_create(&tid, NULL, (void *)thread_httpd, (void *)params);
113             if (result != 0) {
114                 debug(LOG_ERR, "FATAL: Failed to create a new thread (httpd) - exiting");
115                 termination_handler(0);
116             }
117             pthread_detach(tid);
118         }
119         else {
120             ;
121         }
122     }
123 
124     /* never reached */
125 }        

 

用户连接启动线程（void thread_httpd(void * args)）

代码片段1.2

此段代码是当有新用户（未认证的用户 代码片段1.3，已在认证服务器上认证但没有在wifidog认证的用户 代码片段1.4）连接时创建的线程，其主要功能为

• 获取用户浏览器发送过来的http报头
• 分析http报头，分析是否包含关键路径
• 不包含关键路径则调用404回调函数
• 包含关键路径则执行关键路径回调函数（这里主要讲解"/wifidog/auth"路径）

  1 void
  2 thread_httpd(void *args)
  3 {
  4     void    **params;
  5     httpd    *webserver;
  6     request    *r;
  7     
  8     params = (void **)args;
  9     webserver = *params;
 10     r = *(params + 1);
 11     free(params);
 12     
 13     /* 获取http报文 */
 14     if (httpdReadRequest(webserver, r) == 0) {
 15         debug(LOG_DEBUG, "Processing request from %s", r->clientAddr);
 16         debug(LOG_DEBUG, "Calling httpdProcessRequest() for %s", r->clientAddr);
 17         /* 分析http报文 */
 18         httpdProcessRequest(webserver, r);
 19         debug(LOG_DEBUG, "Returned from httpdProcessRequest() for %s", r->clientAddr);
 20     }
 21     else {
 22         debug(LOG_DEBUG, "No valid request received from %s", r->clientAddr);
 23     }
 24     debug(LOG_DEBUG, "Closing connection with %s", r->clientAddr);
 25     httpdEndRequest(r);
 26 }
 27 
 28 
 29 
 30 /* 被thread_httpd调用 */
 31 void httpdProcessRequest(httpd *server, request *r)
 32 {
 33     char    dirName[HTTP_MAX_URL],
 34         entryName[HTTP_MAX_URL],
 35         *cp;
 36     httpDir    *dir;
 37     httpContent *entry;
 38 
 39     r->response.responseLength = 0;
 40     strncpy(dirName, httpdRequestPath(r), HTTP_MAX_URL);
 41     dirName[HTTP_MAX_URL-1]=0;
 42     cp = rindex(dirName, '/');
 43     if (cp == NULL)
 44     {
 45         printf("Invalid request path '%s'\n",dirName);
 46         return;
 47     }
 48     strncpy(entryName, cp + 1, HTTP_MAX_URL);
 49     entryName[HTTP_MAX_URL-1]=0;
 50     if (cp != dirName)
 51         *cp = 0;
 52     else
 53         *(cp+1) = 0;
 54 
 55      /* 获取http报文中的关键路径，在main_loop中已经设置 */
 56     dir = _httpd_findContentDir(server, dirName, HTTP_FALSE);
 57     if (dir == NULL)
 58     {
 59         /* http报文中未包含关键路径，执行404回调函数（在404回调函数中新用户被重定向到认证服务器），见代码片段1.3 */
 60         _httpd_send404(server, r);
 61         _httpd_writeAccessLog(server, r);
 62         return;
 63     }
 64     /* 获取关键路径内容描述符 */
 65     entry = _httpd_findContentEntry(r, dir, entryName);
 66     if (entry == NULL)
 67     {
 68         _httpd_send404(server, r);
 69         _httpd_writeAccessLog(server, r);
 70         return;
 71     }
 72     if (entry->preload)
 73     {
 74         if ((entry->preload)(server) < 0)
 75         {
 76             _httpd_writeAccessLog(server, r);
 77             return;
 78         }
 79     }
 80     switch(entry->type)
 81     {
 82         case HTTP_C_FUNCT:
 83         case HTTP_C_WILDCARD:
 84             /* 如果是被认证服务器重定向到网关的用户，此处的关键路径为"/wifidog/auth"，并执行回调函数 */
 85             (entry->function)(server, r);
 86             break;
 87 
 88         case HTTP_STATIC:
 89             _httpd_sendStatic(server, r, entry->data);
 90             break;
 91 
 92         case HTTP_FILE:
 93             _httpd_sendFile(server, r, entry->path);
 94             break;
 95 
 96         case HTTP_WILDCARD:
 97             if (_httpd_sendDirectoryEntry(server, r, entry,
 98                         entryName)<0)
 99             {
100                 _httpd_send404(server, r);
101             }
102             break;
103     }
104     _httpd_writeAccessLog(server, r);
105 }

 

代码片段1.3

此段代码表示wifidog是如何通过http 404回调函数实现客户端重定向了，实际上就是在404回调函数中封装了一个307状态的http报头，http的307状态在http协议中就是用于重定向的，封装完成后通过已经与客户端连接的socket返回给客户端。步骤流程为

• 判断本机是否处于离线状态
• 判断认证服务器是否在线
• 封装http 307报文
• 发送于目标客户端

 1 void
 2 http_callback_404(httpd *webserver, request *r)
 3 {
 4     char        tmp_url[MAX_BUF],
 5             *url;
 6     s_config    *config = config_get_config();
 7     t_auth_serv    *auth_server = get_auth_server();
 8 
 9     memset(tmp_url, 0, sizeof(tmp_url));
10 
11         snprintf(tmp_url, (sizeof(tmp_url) - 1), "http://%s%s%s%s",
12                         r->request.host,
13                         r->request.path,
14                         r->request.query[0] ? "?" : "",
15                         r->request.query);
16     url = httpdUrlEncode(tmp_url);
17 
18     if (!is_online()) {
19         /* 本机处于离线状态，此函数调用结果由认证服务器检测线程设置 */
20         char * buf;
21         safe_asprintf(&buf, 
22             "<p>We apologize, but it seems that the internet connection that powers this hotspot is temporarily unavailable.</p>"
23             "<p>If at all possible, please notify the owners of this hotspot that the internet connection is out of service.</p>"
24             "<p>The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.</p>"
25             "<p>In a while please <a href='%s'>click here</a> to try your request again.</p>", tmp_url);
26 
27                 send_http_page(r, "Uh oh! Internet access unavailable!", buf);
28         free(buf);
29         debug(LOG_INFO, "Sent %s an apology since I am not online - no point sending them to auth server", r->clientAddr);
30     }
31     else if (!is_auth_online()) {
32         /* 认证服务器处于离线状态 */
33         char * buf;
34         safe_asprintf(&buf, 
35             "<p>We apologize, but it seems that we are currently unable to re-direct you to the login screen.</p>"
36             "<p>The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.</p>"
37             "<p>In a couple of minutes please <a href='%s'>click here</a> to try your request again.</p>", tmp_url);
38 
39                 send_http_page(r, "Uh oh! Login screen unavailable!", buf);
40         free(buf);
41         debug(LOG_INFO, "Sent %s an apology since auth server not online - no point sending them to auth server", r->clientAddr);
42     }
43     else {
44         /* 本机与认证服务器都在线，返回重定向包于客户端 */
45         char *urlFragment;
46         safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&url=%s",
47             auth_server->authserv_login_script_path_fragment,
48             config->gw_address,
49             config->gw_port, 
50             config->gw_id,
51             url);
52         debug(LOG_INFO, "Captured %s requesting [%s] and re-directing them to login page", r->clientAddr, url);
53         http_send_redirect_to_auth(r, urlFragment, "Redirect to login page");  /* 实际上此函数中通过socket返回一个307状态的http报头给客户端，里面包含有认证服务器地址 */
54         free(urlFragment);
55     }
56     free(url);
57 }

 

代码片段1.4

此段表明当客户端已经在认证服务器确认登陆，认证服务器将客户端重新重定向回网关，并在重定向包中包含关键路径"/wifidog/auth"和token，认证服务器所执行的操作。

  1 void 
  2 http_callback_auth(httpd *webserver, request *r)
  3 {
  4     t_client    *client;
  5     httpVar * token;
  6     char    *mac;
  7     /* 判断http报文是否包含登出logout */
  8     httpVar *logout = httpdGetVariableByName(r, "logout");
  9     if ((token = httpdGetVariableByName(r, "token"))) {
 10         /* 获取http报文中的token */
 11         if (!(mac = arp_get(r->clientAddr))) {
 12             /* 获取客户端mac地址失败 */
 13             debug(LOG_ERR, "Failed to retrieve MAC address for ip %s", r->clientAddr);
 14             send_http_page(r, "WiFiDog Error", "Failed to retrieve your MAC address");
 15         } else {
 16             LOCK_CLIENT_LIST();
 17             /* 判断客户端是否存在于列表中 */
 18             if ((client = client_list_find(r->clientAddr, mac)) == NULL) {
 19                 debug(LOG_DEBUG, "New client for %s", r->clientAddr);
 20                 /* 将此客户端添加到客户端列表 */
 21                 client_list_append(r->clientAddr, mac, token->value);
 22             } else if (logout) {
 23                 /* http报文为登出 */
 24                 t_authresponse  authresponse;
 25                 s_config *config = config_get_config();
 26                 unsigned long long incoming = client->counters.incoming;
 27                 unsigned long long outgoing = client->counters.outgoing;
 28                 char *ip = safe_strdup(client->ip);
 29                 char *urlFragment = NULL;
 30                 t_auth_serv    *auth_server = get_auth_server();
 31                 /* 修改iptables禁止客户端访问外网 */                
 32                 fw_deny(client->ip, client->mac, client->fw_connection_state);
 33                 /* 从客户端列表中删除此客户端 */
 34                 client_list_delete(client);
 35                 debug(LOG_DEBUG, "Got logout from %s", client->ip);
 36                 
 37                 if (config->auth_servers != NULL) {
 38                     UNLOCK_CLIENT_LIST();
 39                     /* 发送登出认证包给认证服务器 */
 40                     auth_server_request(&authresponse, REQUEST_TYPE_LOGOUT, ip, mac, token->value, 
 41                                         incoming, outgoing);
 42                     LOCK_CLIENT_LIST();
 43                     
 44                     /* 将客户端重定向到认证服务器 */
 45                     debug(LOG_INFO, "Got manual logout from client ip %s, mac %s, token %s"
 46                     "- redirecting them to logout message", client->ip, client->mac, client->token);
 47                     safe_asprintf(&urlFragment, "%smessage=%s",
 48                         auth_server->authserv_msg_script_path_fragment,
 49                         GATEWAY_MESSAGE_ACCOUNT_LOGGED_OUT
 50                     );
 51                     http_send_redirect_to_auth(r, urlFragment, "Redirect to logout message");
 52                     free(urlFragment);
 53                 }
 54                 free(ip);
 55              } 
 56              else {
 57                 debug(LOG_DEBUG, "Client for %s is already in the client list", client->ip);
 58             }
 59             UNLOCK_CLIENT_LIST();
 60             if (!logout) {
 61                 /* 通过认证服务器认证此客户端token */
 62                 authenticate_client(r);
 63             }
 64             free(mac);
 65         }
 66     } else {
 67         send_http_page(r, "WiFiDog error", "Invalid token");
 68     }
 69 }
 70 
 71 /* 此函数用于提交token到认证服务器进行认证 */
 72 void
 73 authenticate_client(request *r)
 74 {
 75     t_client    *client;
 76     t_authresponse    auth_response;
 77     char    *mac,
 78         *token;
 79     char *urlFragment = NULL;
 80     s_config    *config = NULL;
 81     t_auth_serv    *auth_server = NULL;
 82 
 83     LOCK_CLIENT_LIST();
 84 
 85     client = client_list_find_by_ip(r->clientAddr);
 86     /* 判断此客户端是否在列表中 */
 87     if (client == NULL) {
 88         debug(LOG_ERR, "Could not find client for %s", r->clientAddr);
 89         UNLOCK_CLIENT_LIST();
 90         return;
 91     }
 92     
 93     mac = safe_strdup(client->mac);
 94     token = safe_strdup(client->token);
 95     
 96     UNLOCK_CLIENT_LIST();
 97     
 98     /* 提交token、客户端ip、客户端mac至认证服务器 */
 99     auth_server_request(&auth_response, REQUEST_TYPE_LOGIN, r->clientAddr, mac, token, 0, 0);
100     
101     LOCK_CLIENT_LIST();
102     
103     /*再次判断客户端是否存在于列表中，保险起见，因为有可能在于认证服务器认证过程中，客户端检测线程把此客户端下线 */
104     client = client_list_find(r->clientAddr, mac);
105     
106     if (client == NULL) {
107         debug(LOG_ERR, "Could not find client node for %s (%s)", r->clientAddr, mac);
108         UNLOCK_CLIENT_LIST();
109         free(token);
110         free(mac);
111         return;
112     }
113     
114     free(token);
115     free(mac);
116 
117     config = config_get_config();
118     auth_server = get_auth_server();
119 
120         /* 判断认证服务器认证结果 */
121     switch(auth_response.authcode) {
122 
123     case AUTH_ERROR:
124         /* 认证错误 */
125         debug(LOG_ERR, "Got %d from central server authenticating token %s from %s at %s", auth_response, client->token, client->ip, client->mac);
126         send_http_page(r, "Error!", "Error: We did not get a valid answer from the central server");
127         break;
128 
129     case AUTH_DENIED:
130         /* 认证服务器拒绝此客户端 */
131         debug(LOG_INFO, "Got DENIED from central server authenticating token %s from %s at %s - redirecting them to denied message", client->token, client->ip, client->mac);
132         safe_asprintf(&urlFragment, "%smessage=%s",
133             auth_server->authserv_msg_script_path_fragment,
134             GATEWAY_MESSAGE_DENIED
135         );
136         http_send_redirect_to_auth(r, urlFragment, "Redirect to denied message");
137         free(urlFragment);
138         break;
139 
140     case AUTH_VALIDATION:
141         /* 认证服务器处于等待此客户端电子邮件确认回执状态 */
142         debug(LOG_INFO, "Got VALIDATION from central server authenticating token %s from %s at %s"
143                 "- adding to firewall and redirecting them to activate message", client->token,
144                 client->ip, client->mac);
145         client->fw_connection_state = FW_MARK_PROBATION;
146         fw_allow(client->ip, client->mac, FW_MARK_PROBATION);
147         safe_asprintf(&urlFragment, "%smessage=%s",
148             auth_server->authserv_msg_script_path_fragment,
149             GATEWAY_MESSAGE_ACTIVATE_ACCOUNT
150         );
151         http_send_redirect_to_auth(r, urlFragment, "Redirect to activate message");
152         free(urlFragment);
153         break;
154 
155     case AUTH_ALLOWED:
156         /* 认证通过 */
157         debug(LOG_INFO, "Got ALLOWED from central server authenticating token %s from %s at %s - "
158                 "adding to firewall and redirecting them to portal", client->token, client->ip, client->mac);
159         client->fw_connection_state = FW_MARK_KNOWN;
160         fw_allow(client->ip, client->mac, FW_MARK_KNOWN);
161         served_this_session++;
162         safe_asprintf(&urlFragment, "%sgw_id=%s",
163             auth_server->authserv_portal_script_path_fragment,
164             config->gw_id
165         );
166         http_send_redirect_to_auth(r, urlFragment, "Redirect to portal");
167         free(urlFragment);
168         break;
169 
170     case AUTH_VALIDATION_FAILED:
171          /* 电子邮件确认回执超时 */
172         debug(LOG_INFO, "Got VALIDATION_FAILED from central server authenticating token %s from %s at %s "
173                 "- redirecting them to failed_validation message", client->token, client->ip, client->mac);
174         safe_asprintf(&urlFragment, "%smessage=%s",
175             auth_server->authserv_msg_script_path_fragment,
176             GATEWAY_MESSAGE_ACCOUNT_VALIDATION_FAILED
177         );
178         http_send_redirect_to_auth(r, urlFragment, "Redirect to failed validation message");
179         free(urlFragment);
180         break;
181 
182     default:
183         debug(LOG_WARNING, "I don't know what the validation code %d means for token %s from %s at %s - sending error message", auth_response.authcode, client->token, client->ip, client->mac);
184         send_http_page(r, "Internal Error", "We can not validate your request at this time");
185         break;
186 
187     }
188 
189     UNLOCK_CLIENT_LIST();
190     return;
191 }