Merge #10146: Better error handling for submitblock

30f30c0 Add braces to submitblock per current style. (Gregory Maxwell)
4f15ea1 Check transaction count early in submitblock. (Gregory Maxwell)
ada0caa Make GetWitnessCommitmentIndex callable on blocks without a coinbase txn. (Gregory Maxwell)

Tree-SHA512: 02dcd337ad9cdd8e4fa6a42c009d016026d1229c193676ed6fcc9ce55e924fedec57f516ac1e95c3db0985243ba908307338ce783a70416cb292bed881002bfc

src/rpc/mining.cpp

@@ -720,7 +720,7 @@ protected:
 
 UniValue submitblock(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2)
+    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2) {
         throw std::runtime_error(
             "submitblock \"hexdata\" ( \"jsonparametersobject\" )\n"
             "\nAttempts to submit new block to network.\n"
@@ -738,11 +738,17 @@ UniValue submitblock(const JSONRPCRequest& request)
             + HelpExampleCli("submitblock", "\"mydata\"")
             + HelpExampleRpc("submitblock", "\"mydata\"")
         );
+    }
 
     std::shared_ptr<CBlock> blockptr = std::make_shared<CBlock>();
     CBlock& block = *blockptr;
-    if (!DecodeHexBlk(block, request.params[0].get_str()))
+    if (!DecodeHexBlk(block, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
+    }
+
+    if (block.vtx.empty() || !block.vtx[0]->IsCoinBase()) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block does not start with a coinbase");
+    }
 
     uint256 hash = block.GetHash();
     bool fBlockPresent = false;
@@ -751,10 +757,12 @@ UniValue submitblock(const JSONRPCRequest& request)
         BlockMap::iterator mi = mapBlockIndex.find(hash);
         if (mi != mapBlockIndex.end()) {
             CBlockIndex *pindex = mi->second;
-            if (pindex->IsValid(BLOCK_VALID_SCRIPTS))
+            if (pindex->IsValid(BLOCK_VALID_SCRIPTS)) {
                 return "duplicate";
-            if (pindex->nStatus & BLOCK_FAILED_MASK)
+            }
+            if (pindex->nStatus & BLOCK_FAILED_MASK) {
                 return "duplicate-invalid";
+            }
             // Otherwise, we might only have the header - process the block before returning
             fBlockPresent = true;
         }
@@ -772,14 +780,15 @@ UniValue submitblock(const JSONRPCRequest& request)
     RegisterValidationInterface(&sc);
     bool fAccepted = ProcessNewBlock(Params(), blockptr, true, NULL);
     UnregisterValidationInterface(&sc);
-    if (fBlockPresent)
-    {
-        if (fAccepted && !sc.found)
+    if (fBlockPresent) {
+        if (fAccepted && !sc.found) {
             return "duplicate-inconclusive";
+        }
         return "duplicate";
     }
-    if (!sc.found)
+    if (!sc.found) {
         return "inconclusive";
+    }
     return BIP22ValidationResult(sc.state);
 }
 

src/validation.cpp

@@ -2901,9 +2901,11 @@ bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& pa
 static int GetWitnessCommitmentIndex(const CBlock& block)
 {
     int commitpos = -1;
-    for (size_t o = 0; o < block.vtx[0]->vout.size(); o++) {
-        if (block.vtx[0]->vout[o].scriptPubKey.size() >= 38 && block.vtx[0]->vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0]->vout[o].scriptPubKey[1] == 0x24 && block.vtx[0]->vout[o].scriptPubKey[2] == 0xaa && block.vtx[0]->vout[o].scriptPubKey[3] == 0x21 && block.vtx[0]->vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0]->vout[o].scriptPubKey[5] == 0xed) {
-            commitpos = o;
+    if (!block.vtx.empty()) {
+        for (size_t o = 0; o < block.vtx[0]->vout.size(); o++) {
+            if (block.vtx[0]->vout[o].scriptPubKey.size() >= 38 && block.vtx[0]->vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0]->vout[o].scriptPubKey[1] == 0x24 && block.vtx[0]->vout[o].scriptPubKey[2] == 0xaa && block.vtx[0]->vout[o].scriptPubKey[3] == 0x21 && block.vtx[0]->vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0]->vout[o].scriptPubKey[5] == 0xed) {
+                commitpos = o;
+            }
         }
     }
     return commitpos;