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)

8 files changed, 44 insertions, 21 deletions

diff --git a/src/blockencodings.cpp b/src/blockencodings.cpp
index 93d3fa372b..737102f168 100644
--- a/src/blockencodings.cpp
+++ b/src/blockencodings.cpp
@@ -167,7 +167,7 @@ ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<
         // check its own merkle root and cache that check.
         if (state.CorruptionPossible())
             return READ_STATUS_FAILED; // Possible Short ID collision
-        return READ_STATUS_INVALID;
+        return READ_STATUS_CHECKBLOCK_FAILED;
     }
 
     LogPrint("cmpctblock", "Successfully reconstructed block %s with %lu txn prefilled, %lu txn from mempool and %lu txn requested\n", header.GetHash().ToString(), prefilled_count, mempool_count, vtx_missing.size());
diff --git a/src/blockencodings.h b/src/blockencodings.h
index 99b1cb140d..705eaf28aa 100644
--- a/src/blockencodings.h
+++ b/src/blockencodings.h
@@ -124,6 +124,8 @@ typedef enum ReadStatus_t
     READ_STATUS_OK,
     READ_STATUS_INVALID, // Invalid object, peer is sending bogus crap
     READ_STATUS_FAILED, // Failed to process object
+    READ_STATUS_CHECKBLOCK_FAILED, // Used only by FillBlock to indicate a
+                                   // failure in CheckBlock.
 } ReadStatus;
 
 class CBlockHeaderAndShortTxIDs {
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
diff --git a/src/main.h b/src/main.h
index e80314a64b..9343330587 100644
--- a/src/main.h
+++ b/src/main.h
@@ -223,7 +223,7 @@ static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
  * @param[out]  dbp     The already known disk position of pblock, or NULL if not yet stored.
  * @return True if state.IsValid()
  */
-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);
 /** Check whether enough disk space is available for an incoming block */
 bool CheckDiskSpace(uint64_t nAdditionalBytes = 0);
 /** Open a block file (blk?????.dat) */
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index f418262f02..3e91a79a64 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -132,7 +132,7 @@ UniValue generateBlocks(boost::shared_ptr<CReserveScript> coinbaseScript, int nG
             continue;
         }
         CValidationState state;
-        if (!ProcessNewBlock(state, Params(), NULL, pblock, true, NULL))
+        if (!ProcessNewBlock(state, Params(), NULL, pblock, true, NULL, false))
             throw JSONRPCError(RPC_INTERNAL_ERROR, "ProcessNewBlock, block not accepted");
         ++nHeight;
         blockHashes.push_back(pblock->GetHash().GetHex());
@@ -757,7 +757,7 @@ UniValue submitblock(const JSONRPCRequest& request)
     CValidationState state;
     submitblock_StateCatcher sc(block.GetHash());
     RegisterValidationInterface(&sc);
-    bool fAccepted = ProcessNewBlock(state, Params(), NULL, &block, true, NULL);
+    bool fAccepted = ProcessNewBlock(state, Params(), NULL, &block, true, NULL, false);
     UnregisterValidationInterface(&sc);
     if (fBlockPresent)
     {
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index a94979fd77..2762cafa38 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -223,7 +223,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
         pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
         pblock->nNonce = blockinfo[i].nonce;
         CValidationState state;
-        BOOST_CHECK(ProcessNewBlock(state, chainparams, NULL, pblock, true, NULL));
+        BOOST_CHECK(ProcessNewBlock(state, chainparams, NULL, pblock, true, NULL, false));
         BOOST_CHECK(state.IsValid());
         pblock->hashPrevBlock = pblock->GetHash();
     }
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index 98f4ed939f..3da0be8ca4 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -127,7 +127,7 @@ TestChain100Setup::CreateAndProcessBlock(const std::vector<CMutableTransaction>&
     while (!CheckProofOfWork(block.GetHash(), block.nBits, chainparams.GetConsensus())) ++block.nNonce;
 
     CValidationState state;
-    ProcessNewBlock(state, chainparams, NULL, &block, true, NULL);
+    ProcessNewBlock(state, chainparams, NULL, &block, true, NULL, false);
 
     CBlock result = block;
     return result;
diff --git a/src/version.h b/src/version.h
index 87bd655066..87fb1a3a75 100644
--- a/src/version.h
+++ b/src/version.h
@@ -9,7 +9,7 @@
  * network protocol versioning
  */
 
-static const int PROTOCOL_VERSION = 70014;
+static const int PROTOCOL_VERSION = 70015;
 
 //! initial proto version, to be increased after version/verack negotiation
 static const int INIT_PROTO_VERSION = 209;
@@ -42,4 +42,7 @@ static const int FEEFILTER_VERSION = 70013;
 //! short-id-based block download starts with this version
 static const int SHORT_IDS_BLOCKS_VERSION = 70014;
 
+//! not banning for invalid compact blocks starts with this version
+static const int INVALID_CB_NO_BAN_VERSION = 70015;
+
 #endif // BITCOIN_VERSION_H