Add cpp-httplib to oss-fuzz (#684)

* *Add server fuzzer target  and seed corpus
* Add fuzz_test option to Makefile

* Fix #685

* Try to fix Github actions on Ubuntu

* Added ReadTimeoutSSL test

* Comment out `-fsanitize=address`

* Rebase upstream changes

* remove address sanitizer temporarily

* Add separate Makefile for fuzzing

* 1. Remove special char from dictionary
2. Clean fuzzing/Makefile

* Use specific path to avoid accidently linking openssl version brought in by oss-fuzz

* remove addition of flags

* Refactor Makefile

* Add missing newline

* Add fuzztest to github workflow

* Fix

Co-authored-by: yhirose <yuji.hirose.bug@gmail.com>

test/fuzzing/server_fuzzer.cc

@@ -0,0 +1,88 @@
+#include <memory>
+#include <httplib.h>
+
+class FuzzedStream : public httplib::Stream {
+ public:
+  FuzzedStream(const uint8_t* data, size_t size)
+      : data_(data), size_(size), read_pos_(0) {}
+
+  ssize_t read(char* ptr, size_t size) override {
+    if (size + read_pos_ > size_) {
+      size = size_ - read_pos_;
+    }
+    memcpy(ptr, data_ + read_pos_, size);
+    read_pos_ += size;
+    return size;
+  }
+
+  ssize_t write(const char* ptr, size_t size) override {
+    response_.append(ptr, size);
+    return static_cast<int>(size);
+  }
+
+  int write(const char* ptr) { return write(ptr, strlen(ptr)); }
+
+  int write(const std::string& s) { return write(s.data(), s.size()); }
+
+  std::string get_remote_addr() const { return ""; }
+
+  bool is_readable() const override { return true; }
+
+  bool is_writable() const override { return true; }
+
+  void get_remote_ip_and_port(std::string &ip, int &port) const override {
+    ip = "127.0.0.1";
+    port = 8080;
+  }
+
+ private:
+  const uint8_t* data_;
+  size_t size_;
+  size_t read_pos_;
+  std::string response_;
+};
+
+class FuzzableServer : public httplib::Server {
+ public:
+  void ProcessFuzzedRequest(FuzzedStream& stream) {
+    bool connection_close = false;
+    process_request(stream, /*last_connection=*/false, connection_close,
+                    nullptr);
+  }
+};
+
+static FuzzableServer g_server;
+
+extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv) {
+  g_server.Get(R"(.*)",
+                [&](const httplib::Request& req, httplib::Response& res) {
+                  res.set_content("response content", "text/plain");
+                });
+  g_server.Post(R"(.*)",
+                 [&](const httplib::Request& req, httplib::Response& res) {
+                   res.set_content("response content", "text/plain");
+                 });
+  g_server.Put(R"(.*)",
+                [&](const httplib::Request& req, httplib::Response& res) {
+                  res.set_content("response content", "text/plain");
+                });
+  g_server.Patch(R"(.*)",
+                  [&](const httplib::Request& req, httplib::Response& res) {
+                    res.set_content("response content", "text/plain");
+                  });
+  g_server.Delete(R"(.*)",
+                   [&](const httplib::Request& req, httplib::Response& res) {
+                     res.set_content("response content", "text/plain");
+                   });
+  g_server.Options(R"(.*)",
+                    [&](const httplib::Request& req, httplib::Response& res) {
+                      res.set_content("response content", "text/plain");
+                    });
+  return 0;
+}
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  FuzzedStream stream{data, size};
+  g_server.ProcessFuzzedRequest(stream);
+  return 0;
+}