Namecoin: enforce length restrictions in name script serialization

Fixes #46

electrum_nmc/commands.py

@@ -39,7 +39,7 @@
 from . import bitcoin
 from .bitcoin import is_address,  hash_160, COIN, TYPE_ADDRESS
 from .i18n import _
-from .names import build_name_new, name_expires_in, name_identifier_to_scripthash, OP_NAME_FIRSTUPDATE, OP_NAME_UPDATE
+from .names import build_name_new, name_expires_in, name_identifier_to_scripthash, OP_NAME_FIRSTUPDATE, OP_NAME_UPDATE, validate_value_length
 from .transaction import Transaction, multisig_script, TxOutput
 from .paymentrequest import PR_PAID, PR_UNPAID, PR_UNKNOWN, PR_EXPIRED
 from .synchronizer import Notifier
@@ -675,6 +675,11 @@ def name_update(self, identifier, value=None, destination=None, amount=0.0, fee=
     def name_autoregister(self, identifier, value, destination=None, amount=0.0, fee=None, from_addr=None, change_addr=None, nocheck=False, rbf=None, password=None, locktime=None, allow_existing=False):
         """Creates a name_new transaction, broadcasts it, creates a corresponding name_firstupdate transaction, and queues it. """
 
+        # Validate the value before we try to pre-register the name.  That way,
+        # if the value is invalid, we'll be able to cancel the registration
+        # without losing money in fees.
+        validate_value_length(value)
+
         # TODO: Don't hardcode the 0.005 name_firstupdate fee
         new_result = self.name_new(identifier, amount=amount+0.005, fee=fee, from_addr=from_addr, change_addr=change_addr, nocheck=nocheck, rbf=rbf, password=password, locktime=locktime, allow_existing=allow_existing)
         new_txid = new_result["txid"]

electrum_nmc/gui/qt/configure_name_dialog.py

@@ -146,8 +146,13 @@ def update_and_broadcast(self, identifier, value, transfer_to):
         name_update = self.main_window.console.namespace.get('name_update')
         broadcast = self.main_window.console.namespace.get('broadcast')
 
-        # TODO: support non-ASCII encodings
-        tx = name_update(identifier.decode('ascii'), value.decode('ascii'), recipient_address)['hex']
+        try:
+            # TODO: support non-ASCII encodings
+            tx = name_update(identifier.decode('ascii'), value.decode('ascii'), recipient_address)['hex']
+        except Exception as e:
+            formatted_name = format_name_identifier(identifier)
+            self.main_window.show_error(_("Error creating update for ") + formatted_name + ": " + str(e))
+            return
 
         try:
             broadcast(tx)

electrum_nmc/gui/qt/main_window.py

@@ -3358,12 +3358,20 @@ def check_name_availability(self):
         name_show = self.console.namespace.get('name_show')
 
         name_exists = True
+        name_valid = True
         try:
             name_show(identifier_ascii)
         except commands.NameNotFoundError:
             name_exists = False
+        except util.BitcoinException:
+            # This happens if the name identifier exceeded the 255-byte limit.
+            name_valid = False
 
-        if name_exists:
+        if not name_valid:
+            self.buy_names_available_widget.hide()
+            self.buy_names_already_exists_label.setText(_("That name is invalid (probably exceeded the 255-byte limit) and therefore cannot be registered."))
+            self.buy_names_already_exists_widget.show()
+        elif name_exists:
             self.buy_names_available_widget.hide()
             self.buy_names_already_exists_label.setText(identifier_formatted + _(" is already registered, sorry!"))
             self.buy_names_already_exists_widget.show()

electrum_nmc/names.py

@@ -62,17 +62,20 @@ def name_op_to_script(name_op):
     if name_op is None:
         script = ''
     elif name_op["op"] == OP_NAME_NEW:
+        validate_new_length(name_op)
         script = '51'                                 # OP_NAME_NEW
         script += push_script(bh2u(name_op["hash"]))
         script += '6d'                                # OP_2DROP
     elif name_op["op"] == OP_NAME_FIRSTUPDATE:
+        validate_firstupdate_length(name_op)
         script = '52'                                 # OP_NAME_FIRSTUPDATE
         script += push_script(bh2u(name_op["name"]))
         script += push_script(bh2u(name_op["rand"]))
         script += push_script(bh2u(name_op["value"]))
         script += '6d'                                # OP_2DROP
         script += '6d'                                # OP_2DROP
     elif name_op["op"] == OP_NAME_UPDATE:
+        validate_update_length(name_op)
         script = '53'                                 # OP_NAME_UPDATE
         script += push_script(bh2u(name_op["name"]))
         script += push_script(bh2u(name_op["value"]))
@@ -82,7 +85,51 @@ def name_op_to_script(name_op):
         raise BitcoinException('unknown name op: {}'.format(name_op))
     return script
 
+def validate_new_length(name_op):
+    validate_hash_length(name_op["hash"])
+
+def validate_firstupdate_length(name_op):
+    validate_rand_length(name_op["rand"])
+    validate_anyupdate_length(name_op)
+
+def validate_update_length(name_op):
+    validate_anyupdate_length(name_op)
+
+def validate_anyupdate_length(name_op):
+    validate_identifier_length(name_op["name"])
+    validate_value_length(name_op["value"])
+
+def validate_hash_length(commitment):
+    hash_length_requirement = 20
+
+    hash_length = len(commitment)
+    if hash_length != hash_length_requirement:
+        raise BitcoinException('hash length {} is not equal to requirement of {}'.format(hash_length, hash_length_requirement))
+
+def validate_rand_length(rand):
+    rand_length_requirement = 20
+
+    rand_length = len(rand)
+    if rand_length != rand_length_requirement:
+        raise BitcoinException('rand length {} is not equal to requirement of {}'.format(rand_length, rand_length_requirement))
+
+def validate_identifier_length(identifier):
+    identifier_length_limit = 255
+
+    identifier_length = len(identifier)
+    if identifier_length > identifier_length_limit:
+        raise BitcoinException('identifier length {} exceeds limit of {}'.format(identifier_length, identifier_length_limit))
+
+def validate_value_length(value):
+    value_length_limit = 520
+
+    value_length = len(value)
+    if value_length > value_length_limit:
+        raise BitcoinException('value length {} exceeds limit of {}'.format(value_length, value_length_limit))
+
 def build_name_new(identifier, rand = None):
+    validate_identifier_length(identifier)
+
     if rand is None:
         rand = os.urandom(20)
 
@@ -264,7 +311,7 @@ def name_expires_in(name_height, chain_height):
 from .bitcoin import push_script, script_to_scripthash
 from .crypto import hash_160
 from .transaction import MalformedBitcoinScript, match_decoded, opcodes, OPPushDataGeneric, script_GetOp
-from .util import bh2u
+from .util import bh2u, BitcoinException
 
 OP_NAME_NEW = opcodes.OP_1
 OP_NAME_FIRSTUPDATE = opcodes.OP_2