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Merge bitcoin/bitcoin#28577: net: raise V1_PREFIX_LEN from 12 to 16

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ba2e5bfc67 net: raise V1_PREFIX_LEN from 12 to 16 (Pieter Wuille)

Pull request description:

  A "version" message in the V1 protocol starts with a fixed 16 bytes:
  * The 4-byte network magic
  * The 12-byte command string: "version" plus 5 0x00 bytes

  The current code detects incoming V1 connections by just looking at the first 12 bytes (matching an [earlier version](https://github.com/bitcoin/bips/pull/1496) of BIP324), but 16 bytes is more precise. This isn't an observable difference right now, as a 12 byte prefix ought to be negligible already, but it may become observable with future extensions to the protocol, so make the code match the specification.

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This commit is contained in:
Andrew Chow 2023-10-04 16:50:39 -04:00
commit 5b4478418b
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2 changed files with 6 additions and 6 deletions
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10
src/net.cpp
View file

@ -1098,10 +1098,10 @@ void V2Transport::ProcessReceivedMaybeV1Bytes() noexcept
AssertLockNotHeld(m_send_mutex);
Assume(m_recv_state == RecvState::KEY_MAYBE_V1);
// We still have to determine if this is a v1 or v2 connection. The bytes being received could
// be the beginning of either a v1 packet (network magic + "version\x00"), or of a v2 public
// key. BIP324 specifies that a mismatch with this 12-byte string should trigger sending of the
// key.
std::array<uint8_t, V1_PREFIX_LEN> v1_prefix = {0, 0, 0, 0, 'v', 'e', 'r', 's', 'i', 'o', 'n', 0};
// be the beginning of either a v1 packet (network magic + "version\x00\x00\x00\x00\x00"), or
// of a v2 public key. BIP324 specifies that a mismatch with this 16-byte string should trigger
// sending of the key.
std::array<uint8_t, V1_PREFIX_LEN> v1_prefix = {0, 0, 0, 0, 'v', 'e', 'r', 's', 'i', 'o', 'n', 0, 0, 0, 0, 0};
std::copy(std::begin(Params().MessageStart()), std::end(Params().MessageStart()), v1_prefix.begin());
Assume(m_recv_buffer.size() <= v1_prefix.size());
if (!std::equal(m_recv_buffer.begin(), m_recv_buffer.end(), v1_prefix.begin())) {
@ -1295,7 +1295,7 @@ size_t V2Transport::GetMaxBytesToProcess() noexcept
// receive buffer.
Assume(m_recv_buffer.size() <= V1_PREFIX_LEN);
// As long as we're not sure if this is a v1 or v2 connection, don't receive more than what
// is strictly necessary to distinguish the two (12 bytes). If we permitted more than
// is strictly necessary to distinguish the two (16 bytes). If we permitted more than
// the v1 header size (24 bytes), we may not be able to feed the already-received bytes
// back into the m_v1_fallback V1 transport.
return V1_PREFIX_LEN - m_recv_buffer.size();

2
src/net.h
View file

@ -473,7 +473,7 @@ private:
/** The length of the V1 prefix to match bytes initially received by responders with to
* determine if their peer is speaking V1 or V2. */
static constexpr size_t V1_PREFIX_LEN = 12;
static constexpr size_t V1_PREFIX_LEN = 16;
// The sender side and receiver side of V2Transport are state machines that are transitioned
// through, based on what has been received. The receive state corresponds to the contents of,