Merge #14890: rpc: Avoid creating non-standard raw transactions

fa4c8679ed94f215ce895938f7c3c169a2ce101e rpc: Avoid creating non-standard raw transactions (MarcoFalke)

Pull request description:

  Multiple OP_RETURN outputs in a transaction are not standard and unlikely to be relayed, so avoid creating them.

  Apart from that, the logic was broken in that it duplicated the same hex-data for each data output: Closes #14868.

Tree-SHA512: b08d08062b5622e8a7b497e490ccaf53b06e844c863fda3bf3f932a98684a809e8341aeb98232059a795afb32d8770a6c5591a66f8e6ee372b672af245607887

3 files changed, 15 insertions, 7 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index f5f6c344ea..472b65f975 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -397,7 +397,6 @@ CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniVal
         rawTx.vin.push_back(in);
     }
 
-    std::set<CTxDestination> destinations;
     if (!outputs_is_obj) {
         // Translate array of key-value pairs into dict
         UniValue outputs_dict = UniValue(UniValue::VOBJ);
@@ -413,8 +412,17 @@ CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniVal
         }
         outputs = std::move(outputs_dict);
     }
+
+    // Duplicate checking
+    std::set<CTxDestination> destinations;
+    bool has_data{false};
+
     for (const std::string& name_ : outputs.getKeys()) {
         if (name_ == "data") {
+            if (has_data) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, duplicate key: data");
+            }
+            has_data = true;
             std::vector<unsigned char> data = ParseHexV(outputs[name_].getValStr(), "Data");
 
             CTxOut out(0, CScript() << OP_RETURN << data);
@@ -466,7 +474,8 @@ static UniValue createrawtransaction(const JSONRPCRequest& request)
                                 },
                         },
                         },
-                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs).\n"
+                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs), where none of the keys are duplicated.\n"
+                            "That is, each address can only appear once and there can only be one 'data' object.\n"
                             "For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
                             "                             accepted as second parameter.",
                         {
@@ -1608,7 +1617,8 @@ UniValue createpsbt(const JSONRPCRequest& request)
                                 },
                         },
                         },
-                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs).\n"
+                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs), where none of the keys are duplicated.\n"
+                            "That is, each address can only appear once and there can only be one 'data' object.\n"
                             "For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
                             "                             accepted as second parameter.",
                         {
diff --git a/src/test/rpc_tests.cpp b/src/test/rpc_tests.cpp
index 121b72a5f7..ff48398925 100644
--- a/src/test/rpc_tests.cpp
+++ b/src/test/rpc_tests.cpp
@@ -129,9 +129,6 @@ BOOST_AUTO_TEST_CASE(rpc_createraw_op_return)
 {
     BOOST_CHECK_NO_THROW(CallRPC("createrawtransaction [{\"txid\":\"a3b807410df0b60fcb9736768df5823938b2f838694939ba45f3c0a1bff150ed\",\"vout\":0}] {\"data\":\"68656c6c6f776f726c64\"}"));
 
-    // Allow more than one data transaction output
-    BOOST_CHECK_NO_THROW(CallRPC("createrawtransaction [{\"txid\":\"a3b807410df0b60fcb9736768df5823938b2f838694939ba45f3c0a1bff150ed\",\"vout\":0}] {\"data\":\"68656c6c6f776f726c64\",\"data\":\"68656c6c6f776f726c64\"}"));
-
     // Key not "data" (bad address)
     BOOST_CHECK_THROW(CallRPC("createrawtransaction [{\"txid\":\"a3b807410df0b60fcb9736768df5823938b2f838694939ba45f3c0a1bff150ed\",\"vout\":0}] {\"somedata\":\"68656c6c6f776f726c64\"}"), std::runtime_error);
 
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 4479438238..7d48006606 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4023,7 +4023,8 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
                             },
                         },
                         },
-                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs).\n"
+                    {"outputs", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "a json array with outputs (key-value pairs), where none of the keys are duplicated.\n"
+                            "That is, each address can only appear once and there can only be one 'data' object.\n"
                             "For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
                             "                             accepted as second parameter.",
                         {