Harden against mistakes handling invalid blocks

Fixes a bug in AcceptBlock() in invoking CheckBlock() with incorrect
arguments, and restores a call to CheckBlock() from ProcessNewBlock()
as belt-and-suspenders.

Updates the (overspecified) tests to match behavior.

qa/rpc-tests/p2p-fullblocktest.py

@@ -398,7 +398,7 @@ class FullBlockTest(ComparisonTestFramework):
 
         # Extend the b26 chain to make sure bitcoind isn't accepting b26
         b27 = block(27, spend=out[7])
-        yield rejected(RejectResult(16, b'bad-prevblk'))
+        yield rejected(RejectResult(0, b'bad-prevblk'))
 
         # Now try a too-large-coinbase script
         tip(15)
@@ -410,7 +410,7 @@ class FullBlockTest(ComparisonTestFramework):
 
         # Extend the b28 chain to make sure bitcoind isn't accepting b28
         b29 = block(29, spend=out[7])
-        yield rejected(RejectResult(16, b'bad-prevblk'))
+        yield rejected(RejectResult(0, b'bad-prevblk'))
 
         # b30 has a max-sized coinbase scriptSig.
         tip(23)

src/validation.cpp

@@ -3187,7 +3187,7 @@ static bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidation
     }
     if (fNewBlock) *fNewBlock = true;
 
-    if (!CheckBlock(block, state, chainparams.GetConsensus(), GetAdjustedTime()) ||
+    if (!CheckBlock(block, state, chainparams.GetConsensus()) ||
         !ContextualCheckBlock(block, state, chainparams.GetConsensus(), pindex->pprev)) {
         if (state.IsInvalid() && !state.CorruptionPossible()) {
             pindex->nStatus |= BLOCK_FAILED_VALID;
@@ -3229,13 +3229,19 @@ static bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidation
 bool ProcessNewBlock(const CChainParams& chainparams, const std::shared_ptr<const CBlock> pblock, bool fForceProcessing, bool *fNewBlock)
 {
     {
-        LOCK(cs_main);
-
-        // Store to disk
         CBlockIndex *pindex = NULL;
         if (fNewBlock) *fNewBlock = false;
         CValidationState state;
-        bool ret = AcceptBlock(pblock, state, chainparams, &pindex, fForceProcessing, NULL, fNewBlock);
+        // Ensure that CheckBlock() passes before calling AcceptBlock, as
+        // belt-and-suspenders.
+        bool ret = CheckBlock(*pblock, state, chainparams.GetConsensus());
+
+        LOCK(cs_main);
+
+        if (ret) {
+            // Store to disk
+            ret = AcceptBlock(pblock, state, chainparams, &pindex, fForceProcessing, NULL, fNewBlock);
+        }
         CheckBlockIndex(chainparams.GetConsensus());
         if (!ret) {
             GetMainSignals().BlockChecked(*pblock, state);