Merge #19836: rpc: Properly deserialize txs with witness before signing

3333077823 rpc: Adjust witness-tx deserialize error message (MarcoFalke)
cccc752569 rpc: Properly deserialize txs with witness before signing (MarcoFalke)

Pull request description:

  Signing a transaction can only happen when the transaction has inputs. A transaction with inputs can always be deserialized as witness-transaction. If `try_no_witness` decoding is attempted, this will lead to rare intermittent failures.

  Fixes #18803

ACKs for top commit:
  achow101:
    ACK 3333077823
  ajtowns:
    ACK 3333077823

Tree-SHA512: 73f8a5cdfe03fb0e68908d2fa09752c346406f455694a020ec0dd1267ef8f0a583b8e84063ea74aac127106dd193b72623ca6d81469a94b3f5b3c766ebf2c42b

src/rpc/mining.cpp

@@ -352,7 +352,7 @@ static RPCHelpMan generateblock()
             txs.push_back(MakeTransactionRef(std::move(mtx)));
 
         } else {
-            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("Transaction decode failed for %s", str));
+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("Transaction decode failed for %s. Make sure the tx has at least one input.", str));
         }
     }
 

src/rpc/rawtransaction.cpp

@@ -656,8 +656,8 @@ static RPCHelpMan combinerawtransaction()
     std::vector<CMutableTransaction> txVariants(txs.size());
 
     for (unsigned int idx = 0; idx < txs.size(); idx++) {
-        if (!DecodeHexTx(txVariants[idx], txs[idx].get_str(), true)) {
-            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed for tx %d", idx));
+        if (!DecodeHexTx(txVariants[idx], txs[idx].get_str())) {
+            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed for tx %d. Make sure the tx has at least one input.", idx));
         }
     }
 
@@ -780,8 +780,8 @@ static RPCHelpMan signrawtransactionwithkey()
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR, UniValue::VARR, UniValue::VSTR}, true);
 
     CMutableTransaction mtx;
-    if (!DecodeHexTx(mtx, request.params[0].get_str(), true)) {
-        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    if (!DecodeHexTx(mtx, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
     }
 
     FillableSigningProvider keystore;
@@ -847,10 +847,10 @@ static RPCHelpMan sendrawtransaction()
         UniValueType(), // VNUM or VSTR, checked inside AmountFromValue()
     });
 
-    // parse hex string from parameter
     CMutableTransaction mtx;
-    if (!DecodeHexTx(mtx, request.params[0].get_str()))
-        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    if (!DecodeHexTx(mtx, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
+    }
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
 
     const CFeeRate max_raw_tx_fee_rate = request.params[1].isNull() ?
@@ -928,7 +928,7 @@ static RPCHelpMan testmempoolaccept()
 
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_array()[0].get_str())) {
-        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
     }
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
     const uint256& tx_hash = tx->GetHash();

src/wallet/rpcdump.cpp

@@ -340,8 +340,9 @@ RPCHelpMan importprunedfunds()
     CWallet* const pwallet = wallet.get();
 
     CMutableTransaction tx;
-    if (!DecodeHexTx(tx, request.params[0].get_str()))
-        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    if (!DecodeHexTx(tx, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
+    }
     uint256 hashTx = tx.GetHash();
 
     CDataStream ssMB(ParseHexV(request.params[1], "proof"), SER_NETWORK, PROTOCOL_VERSION);

src/wallet/rpcwallet.cpp

@@ -3331,8 +3331,8 @@ RPCHelpMan signrawtransactionwithwallet()
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR, UniValue::VSTR}, true);
 
     CMutableTransaction mtx;
-    if (!DecodeHexTx(mtx, request.params[0].get_str(), true)) {
-        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    if (!DecodeHexTx(mtx, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
     }
 
     // Sign the transaction