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send datetime and address blocks with path challenge

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orignal
2025-03-29 21:34:16 -04:00
parent 7404ce7fd2
commit c2f68d7021
2 changed files with 29 additions and 15 deletions
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libi2pd/SSU2Session.cpp
+28 -14
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@@ -2562,17 +2562,19 @@ namespace transport
return nullptr;
}
void SSU2Session::AdjustMaxPayloadSize ()
void SSU2Session::AdjustMaxPayloadSize (size_t maxMtu)
{
auto addr = FindLocalAddress ();
if (addr && addr->ssu)
{
int mtu = addr->ssu->mtu;
if (!mtu && addr->IsV4 ()) mtu = SSU2_MAX_PACKET_SIZE;
if (mtu > (int)maxMtu) mtu = maxMtu;
if (m_Address && m_Address->ssu && (!mtu || m_Address->ssu->mtu < mtu))
mtu = m_Address->ssu->mtu;
if (mtu)
{
if (mtu > (int)SSU2_MAX_PACKET_SIZE) mtu = SSU2_MAX_PACKET_SIZE;
if (mtu < (int)SSU2_MIN_PACKET_SIZE) mtu = SSU2_MIN_PACKET_SIZE;
m_MaxPayloadSize = mtu - (addr->IsV6 () ? IPV6_HEADER_SIZE: IPV4_HEADER_SIZE) - UDP_HEADER_SIZE - 32;
LogPrint (eLogDebug, "SSU2: Session MTU=", mtu, ", max payload size=", m_MaxPayloadSize);
@@ -3075,23 +3077,35 @@ namespace transport
void SSU2Session::SendPathChallenge (const boost::asio::ip::udp::endpoint& to)
{
AdjustMaxPayloadSize (SSU2_MIN_PACKET_SIZE); // reduce to minimum
m_WindowSize = SSU2_MIN_WINDOW_SIZE; // reduce window to minimum
uint8_t payload[SSU2_MAX_PACKET_SIZE];
payload[0] = eSSU2BlkPathChallenge;
size_t len = m_Server.GetRng ()() % (m_MaxPayloadSize - 3);
htobe16buf (payload + 1, len);
if (len > 0)
{
m_PathChallenge = std::make_unique<std::pair<i2p::data::Tag<32>, boost::asio::ip::udp::endpoint> >();
RAND_bytes (payload + 3, len);
SHA256 (payload + 3, len, m_PathChallenge->first);
size_t payloadSize = 0;
// datetime block
payload[0] = eSSU2BlkDateTime;
htobe16buf (payload + 1, 4);
htobe32buf (payload + 3, (i2p::util::GetMillisecondsSinceEpoch () + 500)/1000);
payloadSize += 7;
// address block with new address
payloadSize += CreateAddressBlock (payload + payloadSize, m_MaxPayloadSize - payloadSize, to);
// path challenge block
payload[payloadSize] = eSSU2BlkPathChallenge;
size_t len = m_Server.GetRng ()() % (m_MaxPayloadSize - payloadSize - 3 - 8) + 8; // 8 bytes min
htobe16buf (payload + payloadSize + 1, len);
payloadSize += 3;
m_PathChallenge = std::make_unique<std::pair<i2p::data::Tag<32>, boost::asio::ip::udp::endpoint> >();
RAND_bytes (payload + payloadSize, len);
SHA256 (payload + payloadSize, len, m_PathChallenge->first);
m_PathChallenge->second = to;
}
len += 3;
if (len < m_MaxPayloadSize)
len += CreatePaddingBlock (payload + len, m_MaxPayloadSize - len, len < 8 ? 8 : 0);
payloadSize += len;
// padding block
if (payloadSize < m_MaxPayloadSize)
payloadSize += CreatePaddingBlock (payload + payloadSize, m_MaxPayloadSize - payloadSize);
// send to new endpoint
auto existing = m_RemoteEndpoint;
m_RemoteEndpoint = to; // send path challenge to new endpoint
SendData (payload, len);
SendData (payload, payloadSize);
m_RemoteEndpoint = existing; // restore endpoint back until path response received
}