Fix integer overflow in basic password authentication

The string lengths were added and then stored in "char" which is
limited in values at most up to 255. Using size_t is a much more
appropriate type.

In addition the code was using base64 with newlines injected
(easy to fall into that trap as the default is imho wrong), which
means that anything longer than ~ 60 characters never matched and
you had no way to authenticate against the server.

Author: dirkmueller

libraries/ESP8266WebServer/src/ESP8266WebServer-impl.h

@@ -121,41 +121,29 @@ String ESP8266WebServerTemplate<ServerType>::_extractParam(String& authReq,const
 }
 
 template <typename ServerType>
-bool ESP8266WebServerTemplate<ServerType>::authenticate(const char * username, const char * password){
-  if(hasHeader(FPSTR(AUTHORIZATION_HEADER))) {
-    String authReq = header(FPSTR(AUTHORIZATION_HEADER));
-    if(authReq.startsWith(F("Basic"))){
-      authReq = authReq.substring(6);
-      authReq.trim();
-      char toencodeLen = strlen(username)+strlen(password)+1;
-      char *toencode = new (std::nothrow) char[toencodeLen + 1];
-      if(toencode == NULL){
-        authReq = "";
-        return false;
-      }
-      char *encoded = new (std::nothrow) char[base64_encode_expected_len(toencodeLen)+1];
-      if(encoded == NULL){
-        authReq = "";
-        delete[] toencode;
-        return false;
-      }
-      sprintf(toencode, "%s:%s", username, password);
-      if(base64_encode_chars(toencode, toencodeLen, encoded) > 0 && authReq.equalsConstantTime(encoded)) {
-        authReq = "";
-        delete[] toencode;
-        delete[] encoded;
-        return true;
-      }
-      delete[] toencode;
-      delete[] encoded;
-    } else if(authReq.startsWith(F("Digest"))) {
-      String _realm    = _extractParam(authReq, F("realm=\""));
-      String _H1 = credentialHash((String)username,_realm,(String)password);
-      return authenticateDigest((String)username,_H1);
+bool ESP8266WebServerTemplate<ServerType>::authenticate(const char* name, const char* pass) {
+    if (hasHeader(FPSTR(AUTHORIZATION_HEADER))) {
+        String authReq = header(FPSTR(AUTHORIZATION_HEADER));
+        String username(name);
+        String password(pass);
+
+        if (authReq.startsWith(F("Basic"))) {
+            authReq = authReq.substring(6);
+            authReq.trim();
+            String toencode;
+            toencode.reserve(username.length() + 1 + password.length());
+
+            toencode += username;
+            toencode += ':';
+            toencode += password;
+            return authReq.equalsConstantTime(::base64::encode(toencode, false /* doNewLines */));
+        } else if (authReq.startsWith(F("Digest"))) {
+            return authenticateDigest(
+                username, credentialHash(
+                    username, _extractParam(authReq, F("realm=\"")), password));
+        }
     }
-    authReq = "";
-  }
-  return false;
+    return false;
 }
 
 template <typename ServerType>