Also fuzz the extensions negotiator

fuzzing/Extensions.cpp

@@ -0,0 +1,39 @@
+/* This is a fuzz test of the websocket extensions parser */
+
+#define WIN32_EXPORT
+
+#include <cstdio>
+#include <string>
+
+/* We test the websocket extensions parser */
+#include "../src/WebSocketExtensions.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+
+    {
+        uWS::ExtensionsNegotiator<true> extensionsNegotiator(uWS::Options::PERMESSAGE_DEFLATE);
+        extensionsNegotiator.readOffer({(char *) data, size});
+
+        extensionsNegotiator.generateOffer();
+        extensionsNegotiator.getNegotiatedOptions();
+    }
+
+    {
+        uWS::ExtensionsNegotiator<true> extensionsNegotiator(uWS::Options::NO_OPTIONS);
+        extensionsNegotiator.readOffer({(char *) data, size});
+
+        extensionsNegotiator.generateOffer();
+        extensionsNegotiator.getNegotiatedOptions();
+    }
+
+    {
+        uWS::ExtensionsNegotiator<true> extensionsNegotiator(uWS::Options::CLIENT_NO_CONTEXT_TAKEOVER);
+        extensionsNegotiator.readOffer({(char *) data, size});
+
+        extensionsNegotiator.generateOffer();
+        extensionsNegotiator.getNegotiatedOptions();
+    }
+
+    return 0;
+}
+

fuzzing/Makefile

@@ -1,3 +1,4 @@
 default:
 	clang++ -std=c++17 -fsanitize=address,fuzzer -O3 WebSocket.cpp -o WebSocket
 	clang++ -std=c++17 -fsanitize=address,fuzzer -O3 Http.cpp -o Http
+	clang++ -std=c++17 -fsanitize=address,fuzzer -O3 Extensions.cpp -o Extensions

src/WebSocketExtensions.h

@@ -51,12 +51,12 @@ public:
     int clientMaxWindowBits = 0;
 
     int getToken(const char *&in, const char *stop) {
-        while (!isalnum(*in) && in != stop) {
+        while (in != stop && !isalnum(*in)) {
             in++;
         }
 
         int hashedToken = 0;
-        while (isalnum(*in) || *in == '-' || *in == '_') {
+        while (in != stop && (isalnum(*in) || *in == '-' || *in == '_')) {
             if (isdigit(*in)) {
                 hashedToken = hashedToken * 10 - (*in - '0');
             } else {