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Merge bitcoin/bitcoin#23695: p2p: Always serialize local timestamp for version msg

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fa1dc9b36a p2p: Always serialize local timestamp for version msg (MarcoFalke)

Pull request description:

  Currently we serialize the local time when connecting to outbound connections and the "adjusted network" time when someone connects to us.

  I presume the reason is to avoid a fingerprint in case the local time is misconfigured. However, the fingerprint still exits when:
  * The local time goes out-of-sync after timedata is filled up, in which case the adjusted time is *not* adjusted. See comment in `src/timedata.cpp`. (In practise I expect no adjustment to happen after timedata is filled up by one entry more than half its size).
  * The local time is off by more than 70 minutes. See `DEFAULT_MAX_TIME_ADJUSTMENT`. While there is a warning in this case, the warning might be missed by the node operator.
  * The adjusted time is poisoned by an attacker. This is only a theoretical concern after commit e457513eb1.

  Using the adjusted time does help in a the case where the local time is off by a constant less than 70 minutes and the node quickly connects to 5 outbound peers to retrieve the adjusted time.

  Still, I think using `GetAdjustedTime` here gives a false sense of security. It will be better for node operators to instead set the correct time.

ACKs for top commit:
  naumenkogs:
    ACK fa1dc9b36a
  laanwj:
    Code review ACK fa1dc9b36a
  w0xlt:
    crACK fa1dc9b

Tree-SHA512: 70a0f4ab3500e6ddcde291620e35273018cefd1d9e94b91ad333e360139ed18862718bb1a9854af2bf79990bf74b05d95492f77d0747c7b9bdd276c020116dcb
This commit is contained in:
W. J. van der Laan 2021-12-17 21:42:30 +01:00
commit 14ba286556
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1 changed files with 7 additions and 4 deletions
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11
src/net_processing.cpp
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@ -386,7 +386,7 @@ private:
EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
/** Send a version message to a peer */
void PushNodeVersion(CNode& pnode, int64_t nTime);
void PushNodeVersion(CNode& pnode);
/** Send a ping message every PING_INTERVAL or if requested via RPC. May
* mark the peer to be disconnected if a ping has timed out.
@ -1090,12 +1090,13 @@ void PeerManagerImpl::FindNextBlocksToDownload(NodeId nodeid, unsigned int count
} // namespace
void PeerManagerImpl::PushNodeVersion(CNode& pnode, int64_t nTime)
void PeerManagerImpl::PushNodeVersion(CNode& pnode)
{
// Note that pnode->GetLocalServices() is a reflection of the local
// services we were offering when the CNode object was created for this
// peer.
uint64_t my_services{pnode.GetLocalServices()};
const int64_t nTime{count_seconds(GetTime<std::chrono::seconds>())};
uint64_t nonce = pnode.GetLocalNonce();
const int nNodeStartingHeight{m_best_height};
NodeId nodeid = pnode.GetId();
@ -1167,7 +1168,7 @@ void PeerManagerImpl::InitializeNode(CNode *pnode)
m_peer_map.emplace_hint(m_peer_map.end(), nodeid, std::move(peer));
}
if (!pnode->IsInboundConn()) {
PushNodeVersion(*pnode, GetTime());
PushNodeVersion(*pnode);
}
}
@ -2599,7 +2600,9 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type,
// Inbound peers send us their version message when they connect.
// We send our version message in response.
if (pfrom.IsInboundConn()) PushNodeVersion(pfrom, GetAdjustedTime());
if (pfrom.IsInboundConn()) {
PushNodeVersion(pfrom);
}
// Change version
const int greatest_common_version = std::min(nVersion, PROTOCOL_VERSION);