Merge #9026: Fix handling of invalid compact blocks

d4833ff Bump the protocol version to distinguish new banning behavior. (Suhas Daftuar)
88c3549 Fix compact block handling to not ban if block is invalid (Suhas Daftuar)
c93beac [qa] Test that invalid compactblocks don't result in ban (Suhas Daftuar)

1 files changed, 32 insertions, 14 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 2fb143e6a0..7e5b9528b9 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -180,8 +180,10 @@ namespace {
      * Sources of received blocks, saved to be able to send them reject
      * messages or ban them when processing happens afterwards. Protected by
      * cs_main.
+     * Set mapBlockSource[hash].second to false if the node should not be
+     * punished if the block is invalid.
      */
-    map<uint256, NodeId> mapBlockSource;
+    map<uint256, std::pair<NodeId, bool>> mapBlockSource;
 
     /**
      * Filter for transactions that were recently rejected by
@@ -3785,7 +3787,7 @@ static bool AcceptBlock(const CBlock& block, CValidationState& state, const CCha
     return true;
 }
 
-bool ProcessNewBlock(CValidationState& state, const CChainParams& chainparams, CNode* pfrom, const CBlock* pblock, bool fForceProcessing, const CDiskBlockPos* dbp)
+bool ProcessNewBlock(CValidationState& state, const CChainParams& chainparams, CNode* pfrom, const CBlock* pblock, bool fForceProcessing, const CDiskBlockPos* dbp, bool fMayBanPeerIfInvalid)
 {
     {
         LOCK(cs_main);
@@ -3795,7 +3797,7 @@ bool ProcessNewBlock(CValidationState& state, const CChainParams& chainparams, C
         bool fNewBlock = false;
         bool ret = AcceptBlock(*pblock, state, chainparams, &pindex, fForceProcessing, dbp, &fNewBlock);
         if (pindex && pfrom) {
-            mapBlockSource[pindex->GetBlockHash()] = pfrom->GetId();
+            mapBlockSource[pindex->GetBlockHash()] = std::make_pair(pfrom->GetId(), fMayBanPeerIfInvalid);
             if (fNewBlock) pfrom->nLastBlockTime = GetTime();
         }
         CheckBlockIndex(chainparams.GetConsensus());
@@ -4775,16 +4777,16 @@ void PeerLogicValidation::BlockChecked(const CBlock& block, const CValidationSta
     LOCK(cs_main);
 
     const uint256 hash(block.GetHash());
-    std::map<uint256, NodeId>::iterator it = mapBlockSource.find(hash);
+    std::map<uint256, std::pair<NodeId, bool>>::iterator it = mapBlockSource.find(hash);
 
     int nDoS = 0;
     if (state.IsInvalid(nDoS)) {
-        if (it != mapBlockSource.end() && State(it->second)) {
+        if (it != mapBlockSource.end() && State(it->second.first)) {
             assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
             CBlockReject reject = {(unsigned char)state.GetRejectCode(), state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), hash};
-            State(it->second)->rejects.push_back(reject);
-            if (nDoS > 0)
-                Misbehaving(it->second, nDoS);
+            State(it->second.first)->rejects.push_back(reject);
+            if (nDoS > 0 && it->second.second)
+                Misbehaving(it->second.first, nDoS);
         }
     }
     if (it != mapBlockSource.end())
@@ -5893,6 +5895,23 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 invs.push_back(CInv(MSG_BLOCK | GetFetchFlags(pfrom, chainActive.Tip(), chainparams.GetConsensus()), resp.blockhash));
                 connman.PushMessage(pfrom, NetMsgType::GETDATA, invs);
             } else {
+                // Block is either okay, or possibly we received
+                // READ_STATUS_CHECKBLOCK_FAILED.
+                // Note that CheckBlock can only fail for one of a few reasons:
+                // 1. bad-proof-of-work (impossible here, because we've already
+                //    accepted the header)
+                // 2. merkleroot doesn't match the transactions given (already
+                //    caught in FillBlock with READ_STATUS_FAILED, so
+                //    impossible here)
+                // 3. the block is otherwise invalid (eg invalid coinbase,
+                //    block is too big, too many legacy sigops, etc).
+                // So if CheckBlock failed, #3 is the only possibility.
+                // Under BIP 152, we don't DoS-ban unless proof of work is
+                // invalid (we don't require all the stateless checks to have
+                // been run).  This is handled below, so just treat this as
+                // though the block was successfully read, and rely on the
+                // handling in ProcessNewBlock to ensure the block index is
+                // updated, reject messages go out, etc.
                 MarkBlockAsReceived(resp.blockhash); // it is now an empty pointer
                 fBlockRead = true;
             }
@@ -5901,16 +5920,15 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             CValidationState state;
             // Since we requested this block (it was in mapBlocksInFlight), force it to be processed,
             // even if it would not be a candidate for new tip (missing previous block, chain not long enough, etc)
-            ProcessNewBlock(state, chainparams, pfrom, &block, true, NULL);
+            // BIP 152 permits peers to relay compact blocks after validating
+            // the header only; we should not punish peers if the block turns
+            // out to be invalid.
+            ProcessNewBlock(state, chainparams, pfrom, &block, true, NULL, false);
             int nDoS;
             if (state.IsInvalid(nDoS)) {
                 assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
                 connman.PushMessage(pfrom, NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                    state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), block.GetHash());
-                if (nDoS > 0) {
-                    LOCK(cs_main);
-                    Misbehaving(pfrom->GetId(), nDoS);
-                }
             }
         }
     }
@@ -6081,7 +6099,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             // need it even though it is not a candidate for a new best tip.
             forceProcessing |= MarkBlockAsReceived(block.GetHash());
         }
-        ProcessNewBlock(state, chainparams, pfrom, &block, forceProcessing, NULL);
+        ProcessNewBlock(state, chainparams, pfrom, &block, forceProcessing, NULL, true);
         int nDoS;
         if (state.IsInvalid(nDoS)) {
             assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes