[fuzz] fix h1 end to end fuzz test issue

source/common/filesystem/posix/filesystem_impl.cc

@@ -160,6 +160,14 @@ bool InstanceImplPosix::illegalPath(const std::string& path) {
       absl::StartsWith(canonical_path.rc_, "/proc")) {
     return true;
   }
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+  // Allow temporary files in OSS-Fuzz to prevent failures running (h1/h2)_capture_fuzz_test.
+  // Ideally this would be TestEnvironment::temporaryPath() but this avoids depending on test
+  // libraries.
+  if (absl::StartsWith(canonical_path.rc_, "/mnt")) {
+    return true;
+  }
+#endif
   return false;
 }
 

test/integration/h1_capture_direct_response_fuzz_test.cc

@@ -6,11 +6,10 @@ namespace Envoy {
 
 void H1FuzzIntegrationTest::initialize() {
   const std::string body = "Response body";
-  const std::string file_path = TestEnvironment::writeStringToFileForTest("test_envoy", body);
   const std::string prefix("/");
   const Http::Code status(Http::Code::OK);
   config_helper_.addConfigModifier(
-      [&file_path, &prefix](
+      [&body, &prefix](
           envoy::extensions::filters::network::http_connection_manager::v3::HttpConnectionManager&
               hcm) -> void {
         auto* route_config = hcm.mutable_route_config();
@@ -19,7 +18,9 @@ void H1FuzzIntegrationTest::initialize() {
             hcm.mutable_route_config()->mutable_virtual_hosts(0)->mutable_routes(0);
         default_route->mutable_match()->set_prefix(prefix);
         default_route->mutable_direct_response()->set_status(static_cast<uint32_t>(status));
-        default_route->mutable_direct_response()->mutable_body()->set_filename(file_path);
+        // Use inline bytes rather than a filename to avoid using a path that may look illegal to
+        // Envoy.
+        default_route->mutable_direct_response()->mutable_body()->set_inline_bytes(body);
         // adding headers to the default route
         auto* header_value_option = route_config->mutable_response_headers_to_add()->Add();
         header_value_option->mutable_header()->set_value("direct-response-enabled");