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net: Simplify v2 recv logic by decoupling AAD from state machine

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This commit is contained in:
Tim Ruffing 2023-09-26 13:26:27 +02:00
parent b0f5175c04
commit e3720bca39
2 changed files with 18 additions and 24 deletions
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38
src/net.cpp
View File

@ -1190,8 +1190,8 @@ bool V2Transport::ProcessReceivedGarbageBytes() noexcept
if (m_recv_buffer.size() >= BIP324Cipher::GARBAGE_TERMINATOR_LEN) {
if (MakeByteSpan(m_recv_buffer).last(BIP324Cipher::GARBAGE_TERMINATOR_LEN) == m_cipher.GetReceiveGarbageTerminator()) {
// Garbage terminator received. Store garbage to authenticate it as AAD later.
m_recv_garbage = std::move(m_recv_buffer);
m_recv_garbage.resize(m_recv_garbage.size() - BIP324Cipher::GARBAGE_TERMINATOR_LEN);
m_recv_aad = std::move(m_recv_buffer);
m_recv_aad.resize(m_recv_aad.size() - BIP324Cipher::GARBAGE_TERMINATOR_LEN);
m_recv_buffer.clear();
SetReceiveState(RecvState::VERSION);
} else if (m_recv_buffer.size() == MAX_GARBAGE_LEN + BIP324Cipher::GARBAGE_TERMINATOR_LEN) {
@ -1235,43 +1235,37 @@ bool V2Transport::ProcessReceivedPacketBytes() noexcept
// as GetMaxBytesToProcess only allows up to LENGTH_LEN into the buffer before that point.
m_recv_decode_buffer.resize(m_recv_len);
bool ignore{false};
Span<const std::byte> aad;
if (m_recv_state == RecvState::VERSION) aad = MakeByteSpan(m_recv_garbage);
bool ret = m_cipher.Decrypt(
/*input=*/MakeByteSpan(m_recv_buffer).subspan(BIP324Cipher::LENGTH_LEN),
/*aad=*/aad,
/*aad=*/MakeByteSpan(m_recv_aad),
/*ignore=*/ignore,
/*contents=*/MakeWritableByteSpan(m_recv_decode_buffer));
if (!ret) {
LogPrint(BCLog::NET, "V2 transport error: packet decryption failure (%u bytes), peer=%d\n", m_recv_len, m_nodeid);
return false;
}
// We have decrypted a valid packet with the AAD we expected, so clear the expected AAD.
ClearShrink(m_recv_aad);
// Feed the last 4 bytes of the Poly1305 authentication tag (and its timing) into our RNG.
RandAddEvent(ReadLE32(m_recv_buffer.data() + m_recv_buffer.size() - 4));
// At this point we have a valid packet decrypted into m_recv_decode_buffer. Depending on
// the current state, decide what to do with it.
switch (m_recv_state) {
case RecvState::VERSION:
if (!ignore) {
// At this point we have a valid packet decrypted into m_recv_decode_buffer. If it's not a
// decoy, which we simply ignore, use the current state to decide what to do with it.
if (!ignore) {
switch (m_recv_state) {
case RecvState::VERSION:
// Version message received; transition to application phase. The contents is
// ignored, but can be used for future extensions.
SetReceiveState(RecvState::APP);
}
// We have decrypted one valid packet (which may or may not have been a decoy) with the
// received garbage as AAD. We no longer need the received garbage and further packets
// are expected to use the empty string as AAD.
ClearShrink(m_recv_garbage);
break;
case RecvState::APP:
if (!ignore) {
break;
case RecvState::APP:
// Application message decrypted correctly. It can be extracted using GetMessage().
SetReceiveState(RecvState::APP_READY);
break;
default:
// Any other state is invalid (this function should not have been called).
Assume(false);
}
break;
default:
// Any other state is invalid (this function should not have been called).
Assume(false);
}
// Wipe the receive buffer where the next packet will be received into.
ClearShrink(m_recv_buffer);

4
src/net.h
View File

@ -578,8 +578,8 @@ private:
uint32_t m_recv_len GUARDED_BY(m_recv_mutex) {0};
/** Receive buffer; meaning is determined by m_recv_state. */
std::vector<uint8_t> m_recv_buffer GUARDED_BY(m_recv_mutex);
/** During VERSION, the garbage received during GARB_GARBTERM. */
std::vector<uint8_t> m_recv_garbage GUARDED_BY(m_recv_mutex);
/** AAD expected in next received packet (currently used only for garbage). */
std::vector<uint8_t> m_recv_aad GUARDED_BY(m_recv_mutex);
/** Buffer to put decrypted contents in, for converting to CNetMessage. */
std::vector<uint8_t> m_recv_decode_buffer GUARDED_BY(m_recv_mutex);
/** Deserialization type. */