lokinet/llarp/service/outbound_context.cpp

#include "outbound_context.hpp"
#include "async_key_exchange.hpp"
#include "hidden_service_address_lookup.hpp"
#include "endpoint.hpp"
#include "endpoint_util.hpp"
#include "protocol_type.hpp"

#include <llarp/router/router.hpp>
#include <llarp/nodedb.hpp>
#include <llarp/profiling.hpp>
#include <llarp/util/meta/memfn.hpp>

#include <random>
#include <algorithm>

namespace llarp::service
{
  bool
  OutboundContext::Stop()
  {
    markedBad = true;
    return path::Builder::Stop();
  }

  bool
  OutboundContext::IsDone(llarp_time_t now) const
  {
    (void)now;
    return AvailablePaths(path::ePathRoleAny) == 0 && ShouldRemove();
  }

  bool
  OutboundContext::ShouldBundleRC() const
  {
    return m_Endpoint->ShouldBundleRC();
  }

  bool
  OutboundContext::HandleDataDrop(path::Path_ptr p, const PathID_t& dst, uint64_t seq)
  {
    // pick another intro
    if (dst == remoteIntro.path_id && remoteIntro.router == p->Endpoint())
    {
      LogWarn(Name(), " message ", seq, " dropped by endpoint ", p->Endpoint(), " via ", dst);
      markedBad = remoteIntro.IsExpired(Now());
      MarkCurrentIntroBad(Now());
      ShiftIntroRouter(p->Endpoint());
      UpdateIntroSet();
    }
    return true;
  }

  constexpr auto OutboundContextNumPaths = 4;

  OutboundContext::OutboundContext(const IntroSet& introset, Endpoint* parent)
      : path::Builder{parent->router(), OutboundContextNumPaths, parent->numHops}
      , SendContext{introset.addressKeys, {}, this, parent}
      , location{introset.addressKeys.Addr().ToKey()}
      , addr{introset.addressKeys.Addr()}
      , currentIntroSet{introset}

  {
    assert(not introset.intros.empty());
    updatingIntroSet = false;

    // pick random first intro
    auto it = introset.intros.begin();
    if (introset.intros.size() > 1)
    {
      CSRNG rng{};
      it += std::uniform_int_distribution<size_t>{0, introset.intros.size() - 1}(rng);
    }
    m_NextIntro = *it;
    currentConvoTag.Randomize();
    lastShift = Now();
    // add send and connect timeouts to the parent endpoints path alignment timeout
    // this will make it so that there is less of a chance for timing races
    sendTimeout += parent->PathAlignmentTimeout();
    connectTimeout += parent->PathAlignmentTimeout();
  }

  OutboundContext::~OutboundContext() = default;

  /// actually swap intros
  void
  OutboundContext::SwapIntros()
  {
    if (remoteIntro != m_NextIntro)
    {
      remoteIntro = m_NextIntro;
      m_DataHandler->PutSenderFor(currentConvoTag, currentIntroSet.addressKeys, false);
      m_DataHandler->PutIntroFor(currentConvoTag, remoteIntro);
      ShiftIntroRouter(m_NextIntro.router);
      // if we have not made a handshake to the remote endpoint do so
      if (not IntroGenerated())
      {
        KeepAlive();
      }
    }
  }

  Address
  OutboundContext::Addr() const
  {
    return addr;
  }

  bool
  OutboundContext::OnIntroSetUpdate(
      const Address&,
      std::optional<IntroSet> foundIntro,
      const RouterID& endpoint,
      llarp_time_t,
      uint64_t relayOrder)
  {
    if (markedBad)
      return true;
    updatingIntroSet = false;
    if (foundIntro)
    {
      if (foundIntro->time_signed == 0s)
      {
        LogWarn(Name(), " got introset with zero timestamp: ", *foundIntro);
        return true;
      }
      if (currentIntroSet.time_signed > foundIntro->time_signed)
      {
        LogInfo("introset is old, dropping");
        return true;
      }

      const llarp_time_t now = Now();
      if (foundIntro->IsExpired(now))
      {
        LogError("got expired introset from lookup from ", endpoint);
        return true;
      }
      currentIntroSet = *foundIntro;
      ShiftIntroRouter(RouterID{});
    }
    else if (relayOrder > 0)
    {
      ++m_LookupFails;
      LogWarn(Name(), " failed to look up introset, fails=", m_LookupFails);
    }
    return true;
  }

  bool
  OutboundContext::ReadyToSend() const
  {
    if (markedBad)
      return false;
    if (remoteIntro.router.IsZero())
      return false;
    return IntroSent() and GetPathByRouter(remoteIntro.router);
  }

  void
  OutboundContext::ShiftIntroRouter(const RouterID r)
  {
    const auto now = Now();
    Introduction selectedIntro{};
    for (const auto& intro : currentIntroSet.intros)
    {
      if (intro.expiry > selectedIntro.expiry and intro.router != r)
      {
        selectedIntro = intro;
      }
    }
    if (selectedIntro.router.IsZero() || selectedIntro.ExpiresSoon(now))
      return;
    m_NextIntro = selectedIntro;
    lastShift = now;
  }

  void
  OutboundContext::HandlePathBuildTimeout(path::Path_ptr p)
  {
    ShiftIntroRouter(p->Endpoint());
    path::Builder::HandlePathBuildTimeout(p);
  }

  void
  OutboundContext::HandlePathBuildFailedAt(path::Path_ptr p, RouterID hop)
  {
    if (p->Endpoint() == hop)
    {
      // shift intro when we fail at the pivot
      ShiftIntroRouter(p->Endpoint());
    }
    path::Builder::HandlePathBuildFailedAt(p, hop);
  }

  void
  OutboundContext::HandlePathBuilt(path::Path_ptr p)
  {
    path::Builder::HandlePathBuilt(p);
    p->SetDataHandler([self = weak_from_this()](auto path, auto frame) {
      if (auto ptr = self.lock())
        return ptr->HandleHiddenServiceFrame(path, frame);
      return false;
    });
    p->SetDropHandler([self = weak_from_this()](auto path, auto id, auto seqno) {
      if (auto ptr = self.lock())
        return ptr->HandleDataDrop(path, id, seqno);
      return false;
    });
    if (markedBad)
    {
      // ignore new path if we are marked dead
      LogInfo(Name(), " marked bad, ignoring new path");
      p->EnterState(path::ePathIgnore, Now());
    }
    else if (p->Endpoint() == m_NextIntro.router)
    {
      // we now have a path to the next intro, swap intros
      SwapIntros();
    }
  }

  void
  OutboundContext::AsyncGenIntro(const llarp_buffer_t& payload, ProtocolType t)
  {
    if (generatedIntro)
    {
      LogWarn(Name(), " dropping packet as we are not fully handshaked right now");
      return;
    }
    if (remoteIntro.router.IsZero())
    {
      LogWarn(Name(), " dropping intro frame we have no intro ready yet");
      return;
    }

    auto path = GetPathByRouter(remoteIntro.router);
    if (path == nullptr)
    {
      LogError(Name(), " has no path to ", remoteIntro.router, " when we should have had one");
      return;
    }
    auto frame = std::make_shared<ProtocolFrameMessage>();
    frame->clear();
    auto ex = std::make_shared<AsyncKeyExchange>(
        m_Endpoint->Loop(),
        remoteIdent,
        m_Endpoint->GetIdentity(),
        currentIntroSet.sntru_pubkey,
        remoteIntro,
        m_DataHandler,
        currentConvoTag,
        t);

    ex->hook = [self = shared_from_this(), path](auto frame) {
      if (not self->Send(std::move(frame), path))
        return;
      self->m_Endpoint->Loop()->call_later(
          self->remoteIntro.latency, [self]() { self->sentIntro = true; });
    };

    ex->msg.PutBuffer(payload);
    ex->msg.introReply = path->intro;
    frame->path_id = ex->msg.introReply.path_id;
    frame->flag = 0;
    generatedIntro = true;
    // ensure we have a sender put for this convo tag
    m_DataHandler->PutSenderFor(currentConvoTag, currentIntroSet.addressKeys, false);
    // encrypt frame async
    m_Endpoint->router()->queue_work([ex, frame] { return AsyncKeyExchange::Encrypt(ex, frame); });

    LogInfo(Name(), " send intro frame T=", currentConvoTag);
  }

  std::string
  OutboundContext::Name() const
  {
    return "OBContext:" + currentIntroSet.addressKeys.Addr().ToString();
  }

  void
  OutboundContext::UpdateIntroSet()
  {
    constexpr auto IntrosetUpdateInterval = 10s;
    const auto now = Now();
    if (updatingIntroSet or markedBad or now < m_LastIntrosetUpdateAt + IntrosetUpdateInterval)
      return;
    LogInfo(Name(), " updating introset");
    m_LastIntrosetUpdateAt = now;
    // we want to use the parent endpoint's paths because outbound context
    // does not implement path::PathSet::HandleGotIntroMessage
    const auto paths = GetManyPathsWithUniqueEndpoints(m_Endpoint, 2, location);
    uint64_t relayOrder = 0;
    for (const auto& path : paths)
    {
      HiddenServiceAddressLookup* job = new HiddenServiceAddressLookup(
          m_Endpoint,
          util::memFn(&OutboundContext::OnIntroSetUpdate, shared_from_this()),
          location,
          PubKey{addr.as_array()},
          path->Endpoint(),
          relayOrder,
          m_Endpoint->GenTXID(),
          (IntrosetUpdateInterval / 2) + (2 * path->intro.latency) + IntrosetLookupGraceInterval);
      relayOrder++;
      if (job->SendRequestViaPath(path, m_Endpoint->router()))
        updatingIntroSet = true;
    }
  }

  util::StatusObject
  OutboundContext::ExtractStatus() const
  {
    auto obj = path::Builder::ExtractStatus();
    obj["estimatedRTT"] = to_json(estimatedRTT);
    obj["currentConvoTag"] = currentConvoTag.ToHex();
    obj["remoteIntro"] = remoteIntro.ExtractStatus();
    obj["sessionCreatedAt"] = to_json(createdAt);
    obj["lastGoodSend"] = to_json(lastGoodSend);
    obj["lastRecv"] = to_json(m_LastInboundTraffic);
    obj["lastIntrosetUpdate"] = to_json(m_LastIntrosetUpdateAt);
    obj["seqno"] = sequenceNo;
    obj["markedBad"] = markedBad;
    obj["lastShift"] = to_json(lastShift);
    obj["remoteIdentity"] = addr.ToString();
    obj["currentRemoteIntroset"] = currentIntroSet.ExtractStatus();
    obj["nextIntro"] = m_NextIntro.ExtractStatus();
    obj["readyToSend"] = ReadyToSend();
    return obj;
  }

  void
  OutboundContext::KeepAlive()
  {
    std::array<byte_t, 64> tmp;
    llarp_buffer_t buf{tmp};
    CryptoManager::instance()->randomize(buf);
    SendPacketToRemote(buf, ProtocolType::Control);
    m_LastKeepAliveAt = Now();
  }

  bool
  OutboundContext::Pump(llarp_time_t now)
  {
    if (ReadyToSend() and remoteIntro.router.IsZero())
    {
      SwapIntros();
    }
    if (ReadyToSend())
    {
      // if we dont have a cached session key after sending intro we are in a fugged state so
      // expunge
      SharedSecret discardme;
      if (not m_DataHandler->GetCachedSessionKeyFor(currentConvoTag, discardme))
      {
        LogError(Name(), " no cached key after sending intro, we are in a fugged state, oh no");
        return true;
      }
    }

    if (m_GotInboundTraffic and m_LastInboundTraffic + sendTimeout <= now)
    {
      // timeout on other side
      UpdateIntroSet();
      MarkCurrentIntroBad(now);
      ShiftIntroRouter(remoteIntro.router);
    }
    // check for stale intros
    // update the introset if we think we need to
    if (currentIntroSet.HasStaleIntros(now, path::intro_path_spread)
        or remoteIntro.ExpiresSoon(now, path::intro_path_spread))
    {
      UpdateIntroSet();
      ShiftIntroduction(false);
    }

    if (ReadyToSend())
    {
      if (not remoteIntro.router.IsZero() and not GetPathByRouter(remoteIntro.router))
      {
        // pick another good intro if we have no path on our current intro
        std::vector<Introduction> otherIntros;
        ForEachPath([now, router = remoteIntro.router, &otherIntros](auto path) {
          if (path and path->IsReady() and path->Endpoint() != router
              and not path->ExpiresSoon(now, path::intro_path_spread))
          {
            otherIntros.emplace_back(path->intro);
          }
        });
        if (not otherIntros.empty())
        {
          std::shuffle(otherIntros.begin(), otherIntros.end(), CSRNG{});
          remoteIntro = otherIntros[0];
        }
      }
    }
    // lookup router in intro if set and unknown
    if (not m_NextIntro.router.IsZero())
      m_Endpoint->EnsureRouterIsKnown(m_NextIntro.router);

    if (ReadyToSend() and not m_ReadyHooks.empty())
    {
      const auto path = GetPathByRouter(remoteIntro.router);
      if (not path)
      {
        LogWarn(Name(), " ready but no path to ", remoteIntro.router, " ???");
        return true;
      }
      for (const auto& hook : m_ReadyHooks)
        hook(this);
      m_ReadyHooks.clear();
    }

    const auto timeout = std::max(lastGoodSend, m_LastInboundTraffic);
    if (lastGoodSend > 0s and now >= timeout + (sendTimeout / 2))
    {
      // send a keep alive to keep this session alive
      KeepAlive();
      if (markedBad)
      {
        LogWarn(Name(), " keepalive timeout hit");
        return true;
      }
    }

    // check for half open state where we can send but we get nothing back
    if (m_LastInboundTraffic == 0s and now - createdAt > connectTimeout)
    {
      LogWarn(Name(), " half open state, we can send but we got nothing back");
      return true;
    }
    // if we are dead return true so we are removed
    const bool removeIt = timeout > 0s ? (now >= timeout && now - timeout > sendTimeout)
                                       : (now >= createdAt && now - createdAt > connectTimeout);
    if (removeIt)
    {
      LogInfo(Name(), " session is stale");
      return true;
    }
    return false;
  }

  void
  OutboundContext::AddReadyHook(std::function<void(OutboundContext*)> hook, llarp_time_t timeout)
  {
    if (ReadyToSend())
    {
      hook(this);
      return;
    }
    if (m_ReadyHooks.empty())
    {
      m_router->loop()->call_later(timeout, [this]() {
        LogWarn(Name(), " did not obtain session in time");
        for (const auto& hook : m_ReadyHooks)
          hook(nullptr);
        m_ReadyHooks.clear();
      });
    }
    m_ReadyHooks.push_back(hook);
  }

  std::optional<std::vector<RouterContact>>
  OutboundContext::GetHopsForBuild()
  {
    if (m_NextIntro.router.IsZero())
    {
      ShiftIntroduction(false);
    }
    if (m_NextIntro.router.IsZero())
      return std::nullopt;
    return GetHopsAlignedToForBuild(m_NextIntro.router, m_Endpoint->SnodeBlacklist());
  }

  bool
  OutboundContext::ShouldBuildMore(llarp_time_t now) const
  {
    if (markedBad or path::Builder::BuildCooldownHit(now))
      return false;

    if (NumInStatus(path::ePathBuilding) >= std::max(numDesiredPaths / size_t{2}, size_t{1}))
      return false;

    size_t numValidPaths = 0;
    bool havePathToNextIntro = false;
    ForEachPath([now, this, &havePathToNextIntro, &numValidPaths](path::Path_ptr path) {
      if (not path->IsReady())
        return;
      if (not path->intro.ExpiresSoon(now, path::default_lifetime - path::intro_path_spread))
      {
        numValidPaths++;
        if (path->intro.router == m_NextIntro.router)
          havePathToNextIntro = true;
      }
    });
    return numValidPaths < numDesiredPaths or not havePathToNextIntro;
  }

  void
  OutboundContext::MarkCurrentIntroBad(llarp_time_t now)
  {
    MarkIntroBad(remoteIntro, now);
  }

  void
  OutboundContext::MarkIntroBad(const Introduction&, llarp_time_t)
  {}

  bool
  OutboundContext::IntroSent() const
  {
    return sentIntro;
  }

  bool
  OutboundContext::IntroGenerated() const
  {
    return generatedIntro;
  }

  bool
  OutboundContext::ShiftIntroduction(bool rebuild)
  {
    bool success = false;
    const auto now = Now();
    if (abs(now - lastShift) < shiftTimeout)
      return false;
    bool shifted = false;
    std::vector<Introduction> intros = currentIntroSet.intros;
    if (intros.size() > 1)
    {
      std::shuffle(intros.begin(), intros.end(), CSRNG{});
    }

    // to find a intro on the same router as before that is newer
    for (const auto& intro : intros)
    {
      if (intro.ExpiresSoon(now))
        continue;
      if (m_Endpoint->SnodeBlacklist().count(intro.router))
        continue;
      if (remoteIntro.router == intro.router)
      {
        if (intro.expiry > m_NextIntro.expiry)
        {
          success = true;
          m_NextIntro = intro;
        }
      }
    }
    if (!success)
    {
      /// pick newer intro not on same router
      for (const auto& intro : intros)
      {
        if (m_Endpoint->SnodeBlacklist().count(intro.router))
          continue;
        m_Endpoint->EnsureRouterIsKnown(intro.router);
        if (intro.ExpiresSoon(now))
          continue;
        if (m_NextIntro != intro)
        {
          if (intro.expiry > m_NextIntro.expiry)
          {
            shifted = intro.router != m_NextIntro.router;
            m_NextIntro = intro;
            success = true;
          }
        }
      }
    }
    if (m_NextIntro.router.IsZero())
      return false;
    if (shifted)
      lastShift = now;
    if (rebuild && !BuildCooldownHit(Now()))
      BuildOneAlignedTo(m_NextIntro.router);
    return success;
  }

  void
  OutboundContext::HandlePathDied(path::Path_ptr path)
  {
    // unconditionally update introset
    UpdateIntroSet();
    const RouterID endpoint{path->Endpoint()};
    // if a path to our current intro died...
    if (endpoint == remoteIntro.router)
    {
      // figure out how many paths to this router we have
      size_t num = 0;
      ForEachPath([&](const path::Path_ptr& p) {
        if (p->Endpoint() == endpoint && p->IsReady())
          ++num;
      });
      if (num == 0)
      {
        // we have no more paths to this endpoint so we want to pivot off of it
        MarkCurrentIntroBad(Now());
        ShiftIntroRouter(endpoint);
        if (m_NextIntro.router != endpoint)
          BuildOneAlignedTo(m_NextIntro.router);
      }
    }
  }

  bool
  OutboundContext::ShouldKeepAlive(llarp_time_t now) const
  {
    const auto SendKeepAliveInterval = sendTimeout / 2;
    if (not m_GotInboundTraffic)
      return false;
    if (m_LastInboundTraffic == 0s)
      return false;
    return (now - m_LastKeepAliveAt) >= SendKeepAliveInterval;
  }

  void
  OutboundContext::Tick(llarp_time_t now)
  {
    path::Builder::Tick(now);
    if (ShouldKeepAlive(now))
      KeepAlive();
  }

  bool
  OutboundContext::HandleHiddenServiceFrame(path::Path_ptr p, const ProtocolFrameMessage& frame)
  {
    m_LastInboundTraffic = m_Endpoint->Now();
    m_GotInboundTraffic = true;
    if (frame.flag)
    {
      // handle discard
      ServiceInfo si;
      if (!m_Endpoint->GetSenderFor(frame.convo_tag, si))
      {
        LogWarn("no sender for T=", frame.convo_tag);
        return false;
      }
      // verify source
      if (!frame.Verify(si))
      {
        LogWarn("signature verification failed, T=", frame.convo_tag);
        return false;
      }
      // remove convotag it doesn't exist
      LogWarn("remove convotag T=", frame.convo_tag, " R=", frame.flag);

      AuthResult result{AuthResultCode::eAuthFailed, "unknown reason"};
      if (const auto maybe = AuthResultCodeFromInt(frame.flag))
        result.code = *maybe;
      SharedSecret sessionKey{};
      if (m_DataHandler->GetCachedSessionKeyFor(frame.convo_tag, sessionKey))
      {
        ProtocolMessage msg{};
        if (frame.DecryptPayloadInto(sessionKey, msg))
        {
          if (msg.proto == ProtocolType::Auth and not msg.payload.empty())
          {
            result.reason =
                std::string{reinterpret_cast<const char*>(msg.payload.data()), msg.payload.size()};
          }
        }
      }

      m_Endpoint->RemoveConvoTag(frame.convo_tag);
      if (authResultListener)
      {
        authResultListener(result);
        authResultListener = nullptr;
      }
      return true;
    }
    std::function<void(std::shared_ptr<ProtocolMessage>)> hook = nullptr;
    if (authResultListener)
    {
      std::function<void(AuthResult)> handler = authResultListener;
      authResultListener = nullptr;
      hook = [handler](std::shared_ptr<ProtocolMessage> msg) {
        AuthResult result{AuthResultCode::eAuthAccepted, "OK"};
        if (msg->proto == ProtocolType::Auth and not msg->payload.empty())
        {
          result.reason =
              std::string{reinterpret_cast<const char*>(msg->payload.data()), msg->payload.size()};
        }
        handler(result);
      };
    }
    const auto& ident = m_Endpoint->GetIdentity();
    if (not frame.AsyncDecryptAndVerify(m_Endpoint->Loop(), p, ident, m_Endpoint, hook))
    {
      // send reset convo tag message
      LogError("failed to decrypt and verify frame");
      ProtocolFrameMessage f;
      f.flag = 1;
      f.convo_tag = frame.convo_tag;
      f.path_id = p->intro.path_id;

      f.Sign(ident);
      {
        LogWarn("invalidating convotag T=", frame.convo_tag);
        m_Endpoint->RemoveConvoTag(frame.convo_tag);
        m_Endpoint->m_SendQueue.tryPushBack(
            SendEvent_t{std::make_shared<routing::PathTransferMessage>(f, frame.path_id), p});
      }
    }
    return true;
  }

  void
  OutboundContext::SendPacketToRemote(const llarp_buffer_t& buf, service::ProtocolType t)
  {
    AsyncEncryptAndSendTo(buf, t);
  }

}  // namespace llarp::service