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tests: Avoid fuzzer-specific nullptr dereference in libevent when handling PROXY requests

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This commit is contained in:
practicalswift 2020-06-02 09:34:12 +00:00
parent 9e8bd217cd
commit 20d31bdd92
1 changed files with 9 additions and 1 deletions
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10
src/test/fuzz/http_request.cpp
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@ -7,6 +7,7 @@
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/fuzz.h>
#include <test/fuzz/util.h>
#include <util/strencodings.h>
#include <event2/buffer.h>
#include <event2/event.h>
@ -48,7 +49,14 @@ void test_one_input(const std::vector<uint8_t>& buffer)
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) {
// Avoid constructing requests that will be interpreted by libevent as PROXY requests to avoid triggering
// a nullptr dereference. The dereference (req->evcon->http_server) takes place in evhttp_parse_request_line
// and is a consequence of our hacky but necessary use of the internal function evhttp_parse_firstline_ in
// this fuzzing harness. The workaround is not aesthetically pleasing, but it successfully avoids the troublesome
// code path. " http:// HTTP/1.1\n" was a crashing input prior to this workaround.
const std::string http_buffer_str = ToLower({http_buffer.begin(), http_buffer.end()});
if (http_buffer_str.find(" http://") != std::string::npos || http_buffer_str.find(" https://") != std::string::npos ||
evhttp_parse_firstline_(evreq, evbuf) != 1 || evhttp_parse_headers_(evreq, evbuf) != 1) {
evbuffer_free(evbuf);
evhttp_request_free(evreq);
return;