tests: Add fuzzing harness for HTTPRequest, libevent's evhttp and related functions

Author: practicalswift

src/Makefile.test.include

@@ -38,6 +38,7 @@ FUZZ_TARGETS = \
   test/fuzz/flatfile \
   test/fuzz/float \
   test/fuzz/hex \
+  test/fuzz/http_request \
   test/fuzz/integer \
   test/fuzz/inv_deserialize \
   test/fuzz/key \
@@ -489,6 +490,12 @@ test_fuzz_hex_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_hex_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_hex_SOURCES = test/fuzz/hex.cpp
 
+test_fuzz_http_request_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_http_request_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_http_request_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_http_request_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_http_request_SOURCES = test/fuzz/http_request.cpp
+
 test_fuzz_integer_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_integer_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_integer_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/httpserver.cpp

@@ -189,7 +189,7 @@ static bool InitHTTPAllowList()
 }
 
 /** HTTP request method as string - use for logging only */
-static std::string RequestMethodString(HTTPRequest::RequestMethod m)
+std::string RequestMethodString(HTTPRequest::RequestMethod m)
 {
     switch (m) {
     case HTTPRequest::GET:
@@ -510,10 +510,10 @@ void HTTPEvent::trigger(struct timeval* tv)
     else
         evtimer_add(ev, tv); // trigger after timeval passed
 }
-HTTPRequest::HTTPRequest(struct evhttp_request* _req) : req(_req),
-                                                       replySent(false)
+HTTPRequest::HTTPRequest(struct evhttp_request* _req, bool _replySent) : req(_req), replySent(_replySent)
 {
 }
+
 HTTPRequest::~HTTPRequest()
 {
     if (!replySent) {

src/httpserver.h

@@ -60,7 +60,7 @@ class HTTPRequest
     bool replySent;
 
 public:
-    explicit HTTPRequest(struct evhttp_request* req);
+    explicit HTTPRequest(struct evhttp_request* req, bool replySent = false);
     ~HTTPRequest();
 
     enum RequestMethod {

src/test/fuzz/http_request.cpp

@@ -0,0 +1,56 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <httpserver.h>
+#include <netaddress.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <event2/buffer.h>
+#include <event2/http.h>
+#include <event2/http_struct.h>
+
+#include <cassert>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+extern "C" int evhttp_parse_firstline_(struct evhttp_request*, struct evbuffer*);
+extern "C" int evhttp_parse_headers_(struct evhttp_request*, struct evbuffer*);
+std::string RequestMethodString(HTTPRequest::RequestMethod m);
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    evhttp_request* evreq = evhttp_request_new(nullptr, nullptr);
+    assert(evreq != nullptr);
+    evreq->kind = EVHTTP_REQUEST;
+    evbuffer* evbuf = evbuffer_new();
+    assert(evbuf != nullptr);
+    const std::vector<uint8_t> http_buffer = ConsumeRandomLengthByteVector(fuzzed_data_provider, 4096);
+    evbuffer_add(evbuf, http_buffer.data(), http_buffer.size());
+    if (evhttp_parse_firstline_(evreq, evbuf) != 1 || evhttp_parse_headers_(evreq, evbuf) != 1) {
+        evbuffer_free(evbuf);
+        evhttp_request_free(evreq);
+        return;
+    }
+
+    HTTPRequest http_request{evreq, true};
+    const HTTPRequest::RequestMethod request_method = http_request.GetRequestMethod();
+    (void)RequestMethodString(request_method);
+    (void)http_request.GetURI();
+    (void)http_request.GetHeader("Host");
+    const std::string header = fuzzed_data_provider.ConsumeRandomLengthString(16);
+    (void)http_request.GetHeader(header);
+    (void)http_request.WriteHeader(header, fuzzed_data_provider.ConsumeRandomLengthString(16));
+    (void)http_request.GetHeader(header);
+    const std::string body = http_request.ReadBody();
+    assert(body.empty());
+    const CService service = http_request.GetPeer();
+    assert(service.ToString() == "[::]:0");
+
+    evbuffer_free(evbuf);
+    evhttp_request_free(evreq);
+}