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net: make V2Transport preallocate receive buffer space

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This commit is contained in:
Pieter Wuille 2023-07-30 10:51:12 -04:00
parent 3ffa5fb49e
commit 297c888997
1 changed files with 37 additions and 0 deletions
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37
src/net.cpp
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@ -1317,6 +1317,9 @@ size_t V2Transport::GetMaxBytesToProcess() noexcept
bool V2Transport::ReceivedBytes(Span<const uint8_t>& msg_bytes) noexcept
{
AssertLockNotHeld(m_recv_mutex);
/** How many bytes to allocate in the receive buffer at most above what is received so far. */
static constexpr size_t MAX_RESERVE_AHEAD = 256 * 1024;
LOCK(m_recv_mutex);
if (m_recv_state == RecvState::V1) return m_v1_fallback.ReceivedBytes(msg_bytes);
@ -1327,6 +1330,40 @@ bool V2Transport::ReceivedBytes(Span<const uint8_t>& msg_bytes) noexcept
while (!msg_bytes.empty()) {
// Decide how many bytes to copy from msg_bytes to m_recv_buffer.
size_t max_read = GetMaxBytesToProcess();
// Reserve space in the buffer if there is not enough.
if (m_recv_buffer.size() + std::min(msg_bytes.size(), max_read) > m_recv_buffer.capacity()) {
switch (m_recv_state) {
case RecvState::KEY_MAYBE_V1:
case RecvState::KEY:
case RecvState::GARB_GARBTERM:
// During the initial states (key/garbage), allocate once to fit the maximum (4111
// bytes).
m_recv_buffer.reserve(MAX_GARBAGE_LEN + BIP324Cipher::GARBAGE_TERMINATOR_LEN);
break;
case RecvState::GARBAUTH:
case RecvState::VERSION:
case RecvState::APP: {
// During states where a packet is being received, as much as is expected but never
// more than MAX_RESERVE_AHEAD bytes in addition to what is received so far.
// This means attackers that want to cause us to waste allocated memory are limited
// to MAX_RESERVE_AHEAD above the largest allowed message contents size, and to
// MAX_RESERVE_AHEAD more than they've actually sent us.
size_t alloc_add = std::min(max_read, msg_bytes.size() + MAX_RESERVE_AHEAD);
m_recv_buffer.reserve(m_recv_buffer.size() + alloc_add);
break;
}
case RecvState::APP_READY:
// The buffer is empty in this state.
Assume(m_recv_buffer.empty());
break;
case RecvState::V1:
// Should have bailed out above.
Assume(false);
break;
}
}
// Can't read more than provided input.
max_read = std::min(msg_bytes.size(), max_read);
// Copy data to buffer.