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fuzz: FuzzedSock::Recv() don't lose bytes from MSG_PEEK read

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Problem:

If `FuzzedSock::Recv(N, MSG_PEEK)` is called then `N` bytes would be
retrieved from the fuzz provider, saved in `m_peek_data` and returned
to the caller (ok).

If after this `FuzzedSock::Recv(M, 0)` is called where `M < N`
then the first `M` bytes from `m_peek_data` would be returned
to the caller (ok), but the remaining `N - M` bytes in `m_peek_data`
would be discarded/lost (not ok). They must be returned by a subsequent
`Recv()`.

To resolve this, only remove the head `N` bytes from `m_peek_data`.
This commit is contained in:
Vasil Dimov 2024-06-12 14:41:50 +02:00
parent b51d75ea97
commit 4d81b4de33
No known key found for this signature in database
GPG key ID: 54DF06F64B55CBBF
1 changed files with 34 additions and 34 deletions
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68
src/test/fuzz/util/net.cpp
View file

@ -182,6 +182,12 @@ ssize_t FuzzedSock::Recv(void* buf, size_t len, int flags) const
EWOULDBLOCK,
};
assert(buf != nullptr || len == 0);
// Do the latency before any of the "return" statements.
if (m_fuzzed_data_provider.ConsumeBool() && std::getenv("FUZZED_SOCKET_FAKE_LATENCY") != nullptr) {
std::this_thread::sleep_for(std::chrono::milliseconds{2});
}
if (len == 0 || m_fuzzed_data_provider.ConsumeBool()) {
const ssize_t r = m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
if (r == -1) {
@ -189,47 +195,41 @@ ssize_t FuzzedSock::Recv(void* buf, size_t len, int flags) const
}
return r;
}
std::vector<uint8_t> random_bytes;
bool pad_to_len_bytes{m_fuzzed_data_provider.ConsumeBool()};
size_t copied_so_far{0};
if (!m_peek_data.empty()) {
// `MSG_PEEK` was used in the preceding `Recv()` call, return `m_peek_data`.
random_bytes = m_peek_data;
// `MSG_PEEK` was used in the preceding `Recv()` call, copy the first bytes from `m_peek_data`.
const size_t copy_len{std::min(len, m_peek_data.size())};
std::memcpy(buf, m_peek_data.data(), copy_len);
copied_so_far += copy_len;
if ((flags & MSG_PEEK) == 0) {
m_peek_data.clear();
m_peek_data.erase(m_peek_data.begin(), m_peek_data.begin() + copy_len);
}
pad_to_len_bytes = false;
} else if ((flags & MSG_PEEK) != 0) {
// New call with `MSG_PEEK`.
random_bytes = ConsumeRandomLengthByteVector(m_fuzzed_data_provider, len);
if (!random_bytes.empty()) {
m_peek_data = random_bytes;
pad_to_len_bytes = false;
}
} else {
random_bytes = ConsumeRandomLengthByteVector(m_fuzzed_data_provider, len);
}
if (random_bytes.empty()) {
const ssize_t r = m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
if (r == -1) {
SetFuzzedErrNo(m_fuzzed_data_provider, recv_errnos);
}
return r;
if (copied_so_far == len) {
return copied_so_far;
}
// `random_bytes` might exceed the size of `buf` if e.g. Recv is called with
// len=N and MSG_PEEK first and afterwards called with len=M (M < N) and
// without MSG_PEEK.
size_t recv_len{std::min(random_bytes.size(), len)};
std::memcpy(buf, random_bytes.data(), recv_len);
if (pad_to_len_bytes) {
if (len > random_bytes.size()) {
std::memset((char*)buf + random_bytes.size(), 0, len - random_bytes.size());
}
return len;
auto new_data = ConsumeRandomLengthByteVector(m_fuzzed_data_provider, len - copied_so_far);
if (new_data.empty()) return copied_so_far;
std::memcpy(reinterpret_cast<uint8_t*>(buf) + copied_so_far, new_data.data(), new_data.size());
copied_so_far += new_data.size();
if ((flags & MSG_PEEK) != 0) {
m_peek_data.insert(m_peek_data.end(), new_data.begin(), new_data.end());
}
if (m_fuzzed_data_provider.ConsumeBool() && std::getenv("FUZZED_SOCKET_FAKE_LATENCY") != nullptr) {
std::this_thread::sleep_for(std::chrono::milliseconds{2});
if (copied_so_far == len || m_fuzzed_data_provider.ConsumeBool()) {
return copied_so_far;
}
return recv_len;
// Pad to len bytes.
std::memset(reinterpret_cast<uint8_t*>(buf) + copied_so_far, 0x0, len - copied_so_far);
return len;
}
int FuzzedSock::Connect(const sockaddr*, socklen_t) const