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_DENIED135         );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_ACCOUNT150         );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_id165         );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_FAILED177         );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 }