sanity check on transaction construction

lib/bitcoin.py

@@ -540,6 +540,16 @@ def chunks(l, n):
     # Serialise inputs and outputs.
     unsigned_tx = serialise(block_index, encoding, inputs, destination_outputs, data_output, change_output, self_public_key=self_public_key)
     unsigned_tx_hex = binascii.hexlify(unsigned_tx).decode('utf-8')
+
+    # Check that the constructed transaction isn’t doing anything funny.
+    from lib import blocks
+    (desired_source, desired_destination_outputs, desired_data) = tx_info
+    desired_destination = desired_destination_outputs[0][0] if desired_destination_outputs else ''
+    if desired_data == None: desired_data = b''
+    parsed_source, parsed_destination, x, y, parsed_data = blocks.get_tx_info2(unsigned_tx_hex)
+    if (desired_source, desired_destination, desired_data) != (parsed_source, parsed_destination, parsed_data):
+        raise TransactionError('constructed transaction does not parse correctly')
+
     return unsigned_tx_hex
 
 def sign_tx (unsigned_tx_hex, private_key_wif=None):

lib/blocks.py

@@ -1001,9 +1001,9 @@ def initialise(db):
 def get_tx_info (tx_hex, block_index, block_parser = None):
     try:
         if util.multisig_enabled(block_index):  # Protocol change.
-            tx_info = get_tx_info2(tx_hex, block_index, block_parser)
+            tx_info = get_tx_info2(tx_hex, block_parser=block_parser)
         else:
-            tx_info = get_tx_info1(tx_hex, block_index, block_parser)
+            tx_info = get_tx_info1(tx_hex, block_index, block_parser=block_parser)
     except DecodeError as e:
         logging.debug('Could not decode: ' + str(e))
         tx_info = b'', None, None, None, None
@@ -1120,7 +1120,7 @@ def get_address (scriptpubkey):
 
     return source, destination, btc_amount, fee, data
 
-def get_tx_info2 (tx_hex, block_index, block_parser = None):
+def get_tx_info2 (tx_hex, block_parser = None):
     """
     The destinations, if they exists, always comes before the data output; the
     change, if it exists, always comes after.

test/util_test.py

@@ -108,7 +108,7 @@ def insert_raw_transaction(raw_transaction, db, rawtransactions_db):
     if pytest.config.option.savescenarios:
         save_rawtransaction(rawtransactions_db, tx_hash, raw_transaction, json.dumps(tx))
 
-    source, destination, btc_amount, fee, data = blocks.get_tx_info2(raw_transaction, block_index)
+    source, destination, btc_amount, fee, data = blocks.get_tx_info2(raw_transaction)
     transaction = (tx_index, tx_hash, block_index, block_hash, block_time, source, destination, btc_amount, fee, data, True)
     cursor.execute('''INSERT INTO transactions VALUES (?,?,?,?,?,?,?,?,?,?,?)''', transaction)
     tx = list(cursor.execute('''SELECT * FROM transactions WHERE tx_index = ?''', (tx_index,)))[0]