fuzz: fix oss crash on http utility function (envoyproxy#11687)

Commit Message: Fix crash on initializeAndValidateOptions fuzz test
the crash occurred because validateCustomSettingsParameters does not allow duplicate custom settings identifiers and the fuzzer fed it an input that had duplicates. fixed by catching expected exceptions from duplicate custom settings identifiers.
Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=23616

Signed-off-by: Sam Flattery <[email protected]>

Author: samflattery

test/common/http/utility_corpus/clusterfuzz-testcase-minimized-utility_fuzz_test-5091558495092736

@@ -79,7 +79,28 @@ DEFINE_PROTO_FUZZER(const test::common::http::UtilityTestCase& input) {
   }
   case test::common::http::UtilityTestCase::kInitializeAndValidate: {
     const auto& options = input.initialize_and_validate();
-    Http2::Utility::initializeAndValidateOptions(options);
+    try {
+      Http2::Utility::initializeAndValidateOptions(options);
+    } catch (EnvoyException& e) {
+      absl::string_view msg = e.what();
+      // initializeAndValidateOptions throws exceptions for 4 different reasons due to malformed
+      // settings, so check for them and allow any other exceptions through
+      if (absl::StartsWith(
+              msg, "server push is not supported by Envoy and can not be enabled via a SETTINGS "
+                   "parameter.") ||
+          absl::StartsWith(
+              msg, "the \"allow_connect\" SETTINGS parameter must only be configured through the "
+                   "named field") ||
+          absl::StartsWith(
+              msg, "inconsistent HTTP/2 custom SETTINGS parameter(s) detected; identifiers =") ||
+          absl::EndsWith(
+              msg, "HTTP/2 SETTINGS parameter(s) can not be configured through both named and "
+                   "custom parameters")) {
+        ENVOY_LOG_MISC(trace, "Caught exception {} in initializeAndValidateOptions test", e.what());
+      } else {
+        throw EnvoyException(e.what());
+      }
+    }
     break;
   }