[WiFi Setup] Implement captive portal to automatically sign in

A captive portal allows a connected user to be redirected to the node when signing in to its AP.
If no WiFi credentials are present, it will redirect to the setup page immediately.

src/src/Helpers/StringConverter.cpp

@@ -78,11 +78,16 @@ bool string2float(const String& string, float& floatvalue) {
 /********************************************************************************************\
    Convert a char string to IP byte array
  \*********************************************************************************************/
-boolean str2ip(const String& string, byte *IP) {
+bool isIP(const String& string) {
+  IPAddress tmpip;
+  return (tmpip.fromString(string));
+}
+
+bool str2ip(const String& string, byte *IP) {
   return str2ip(string.c_str(), IP);
 }
 
-boolean str2ip(const char *string, byte *IP)
+bool str2ip(const char *string, byte *IP)
 {
   IPAddress tmpip; // Default constructor => set to 0.0.0.0
 
@@ -644,7 +649,7 @@ String URLEncode(const char *msg)
   return encodedMsg;
 }
 
-void repl(const String& key, const String& val, String& s, boolean useURLencode)
+void repl(const String& key, const String& val, String& s, bool useURLencode)
 {
   if (useURLencode) {
     // URLEncode does take resources, so check first if needed.
@@ -656,7 +661,7 @@ void repl(const String& key, const String& val, String& s, boolean useURLencode)
 }
 
 #ifndef BUILD_NO_SPECIAL_CHARACTERS_STRINGCONVERTER
-void parseSpecialCharacters(String& s, boolean useURLencode)
+void parseSpecialCharacters(String& s, bool useURLencode)
 {
   bool no_accolades   = s.indexOf('{') == -1 || s.indexOf('}') == -1;
   bool no_html_entity = s.indexOf('&') == -1 || s.indexOf(';') == -1;
@@ -740,7 +745,7 @@ void parseSpecialCharacters(String& s, boolean useURLencode)
 /********************************************************************************************\
    replace other system variables like %sysname%, %systime%, %ip%
  \*********************************************************************************************/
-void parseControllerVariables(String& s, struct EventStruct *event, boolean useURLencode) {
+void parseControllerVariables(String& s, struct EventStruct *event, bool useURLencode) {
   s = parseTemplate(s, useURLencode);
   parseEventVariables(s, event, useURLencode);
 }
@@ -748,7 +753,7 @@ void parseControllerVariables(String& s, struct EventStruct *event, boolean useU
 void parseSingleControllerVariable(String            & s,
                                    struct EventStruct *event,
                                    byte                taskValueIndex,
-                                   boolean             useURLencode) {
+                                   bool             useURLencode) {
   if (validTaskIndex(event->TaskIndex)) {
     LoadTaskSettings(event->TaskIndex);
     repl(F("%valname%"), ExtraTaskSettings.TaskDeviceValueNames[taskValueIndex], s, useURLencode);
@@ -761,7 +766,7 @@ void parseSingleControllerVariable(String            & s,
 // Simple macro to create the replacement string only when needed.
 #define SMART_REPL(T, S) \
   if (s.indexOf(T) != -1) { repl((T), (S), s, useURLencode); }
-void parseSystemVariables(String& s, boolean useURLencode)
+void parseSystemVariables(String& s, bool useURLencode)
 {
   #ifndef BUILD_NO_SPECIAL_CHARACTERS_STRINGCONVERTER
   parseSpecialCharacters(s, useURLencode);
@@ -770,7 +775,7 @@ void parseSystemVariables(String& s, boolean useURLencode)
   SystemVariables::parseSystemVariables(s, useURLencode);
 }
 
-void parseEventVariables(String& s, struct EventStruct *event, boolean useURLencode)
+void parseEventVariables(String& s, struct EventStruct *event, bool useURLencode)
 {
   repl(F("%id%"), String(event->idx), s, useURLencode);
 
@@ -867,7 +872,7 @@ bool getConvertArgumentString(const String& marker, const String& s, String& arg
 
 // Parse conversions marked with "%conv_marker%(float)"
 // Must be called last, since all sensor values must be converted, processed, etc.
-void parseStandardConversions(String& s, boolean useURLencode) {
+void parseStandardConversions(String& s, bool useURLencode) {
   if (s.indexOf(F("%c_")) == -1) {
     return; // Nothing to replace
   }

src/src/Helpers/StringConverter.h

@@ -32,10 +32,12 @@ bool string2float(const String& string,
 /********************************************************************************************\
    Convert a char string to IP byte array
  \*********************************************************************************************/
-boolean str2ip(const String& string,
+bool isIP(const String& string);
+
+bool str2ip(const String& string,
                byte         *IP);
 
-boolean str2ip(const char *string,
+bool str2ip(const char *string,
                byte       *IP);
 
 String  formatIP(const IPAddress& ip);
@@ -198,11 +200,11 @@ String URLEncode(const char *msg);
 void   repl(const String& key,
             const String& val,
             String      & s,
-            boolean       useURLencode);
+            bool       useURLencode);
 
 #ifndef BUILD_NO_SPECIAL_CHARACTERS_STRINGCONVERTER
 void parseSpecialCharacters(String& s,
-                            boolean useURLencode);
+                            bool useURLencode);
 #endif // ifndef BUILD_NO_SPECIAL_CHARACTERS_STRINGCONVERTER
 
 /********************************************************************************************\
@@ -210,19 +212,19 @@ void parseSpecialCharacters(String& s,
  \*********************************************************************************************/
 void parseControllerVariables(String            & s,
                               struct EventStruct *event,
-                              boolean             useURLencode);
+                              bool             useURLencode);
 
 void parseSingleControllerVariable(String            & s,
                                    struct EventStruct *event,
                                    byte                taskValueIndex,
-                                   boolean             useURLencode);
+                                   bool             useURLencode);
 
 void parseSystemVariables(String& s,
-                          boolean useURLencode);
+                          bool useURLencode);
 
 void parseEventVariables(String            & s,
                          struct EventStruct *event,
-                         boolean             useURLencode);
+                         bool             useURLencode);
 
 bool getConvertArgument(const String& marker,
                         const String& s,
@@ -246,7 +248,7 @@ bool getConvertArgumentString(const String& marker,
 // Parse conversions marked with "%conv_marker%(float)"
 // Must be called last, since all sensor values must be converted, processed, etc.
 void parseStandardConversions(String& s,
-                              boolean useURLencode);
+                              bool useURLencode);
 
 
 bool HasArgv(const char  *string,

src/src/WebServer/404.cpp

@@ -17,6 +17,10 @@ void handleNotFound() {
   checkRAM(F("handleNotFound"));
   #endif
 
+  if (captivePortal()) { // If captive portal redirect instead of displaying the error page.
+    return;
+  }
+
   // if Wifi setup, launch setup wizard if AP_DONT_FORCE_SETUP is not set.
  if (WiFiEventData.wifiSetup && !Settings.ApDontForceSetup())
   {

src/src/WebServer/RootPage.cpp

@@ -31,6 +31,8 @@
 #endif
 
 
+
+
 // ********************************************************************************
 // Web Interface root page
 // ********************************************************************************
@@ -39,6 +41,10 @@ void handle_root() {
   checkRAM(F("handle_root"));
   #endif
 
+ if (captivePortal()) { // If captive portal redirect instead of displaying the page.
+   return;
+ }
+
   // if Wifi setup, launch setup wizard if AP_DONT_FORCE_SETUP is not set.
  if (WiFiEventData.wifiSetup && !Settings.ApDontForceSetup())
   {

src/src/WebServer/RootPage.h

@@ -6,11 +6,15 @@
 
 #ifdef WEBSERVER_ROOT
 
+
+
 // ********************************************************************************
 // Web Interface root page
 // ********************************************************************************
 void handle_root();
 
+
+
 #endif // ifdef WEBSERVER_ROOT
 
 

src/src/WebServer/WebServer.cpp

@@ -267,6 +267,24 @@ size_t streamFile_htmlEscape(const String& fileName)
   return size;
 }
 
+
+bool captivePortal() {
+  if (!isIP(web_server.hostHeader()) && web_server.hostHeader() != (NetworkGetHostname() + F(".local"))) {
+    const bool fromAP = web_server.client().localIP() == apIP;
+    String redirectURL = F("http://");
+    redirectURL += web_server.client().localIP().toString();
+    if (fromAP && !SecuritySettings.hasWiFiCredentials()) {
+      redirectURL += F("/setup");
+    }
+    web_server.sendHeader(F("Location"), redirectURL, true);
+    web_server.send(302, F("text/plain"), "");   // Empty content inhibits Content-length header so we have to close the socket ourselves.
+    web_server.client().stop(); // Stop is needed because we sent no content length
+    return true;
+  }
+  return false;
+}
+
+
 // ********************************************************************************
 // Web Interface init
 // ********************************************************************************
@@ -280,7 +298,11 @@ void WebServerInit()
 
   // Prepare webserver pages
   #ifdef WEBSERVER_ROOT
-  web_server.on(F("/"),               handle_root);
+  web_server.on(F("/"),             handle_root);
+  // Entries for several captive portal URLs.
+  // Maybe not needed. Might be handled by notFound handler.
+  web_server.on(F("/generate_204"), handle_root);  //Android captive portal.
+  web_server.on(F("/fwlink"),       handle_root);  //Microsoft captive portal.
   #endif // ifdef WEBSERVER_ROOT
   #ifdef WEBSERVER_ADVANCED
   web_server.on(F("/advanced"),    handle_advanced);

src/src/WebServer/WebServer.h

@@ -44,6 +44,12 @@ size_t streamFile_htmlEscape(const String& fileName);
 
 void   WebServerInit();
 
+// ********************************************************************************
+// Redirect to captive portal if we got a request for another domain. 
+// Return true in that case so the page handler does not try to handle the request again.
+// ********************************************************************************
+bool   captivePortal();
+
 void   setWebserverRunning(bool state);
 
 void   getWebPageTemplateDefault(const String& tmplName,