Introduce requested changes, log when malicious / empty metadata received

magneticod/magneticod/__main__.py

@@ -67,8 +67,11 @@ def main():
 
     complete_info_hashes = database.get_complete_info_hashes()
 
-    node = dht.SybilNode(arguments.node_addr, max_metadata_size=arguments.metadata_size_limit)
+    node = dht.SybilNode(arguments.node_addr)
-    node.when_peer_found = on_peer_found
+
+    node.when_peer_found = lambda info_hash, peer_address: on_peer_found(info_hash=info_hash,
+                                                                         peer_address=peer_address,
+                                                                         max_metadata_size=arguments.max_metadata_size)
 
     selector.register(node, selectors.EVENT_READ)
 
@@ -223,8 +226,8 @@ def parse_cmdline_arguments() -> typing.Optional[argparse.Namespace]:
     )
 
     parser.add_argument(
-        "--metadata-size-limit", type=parse_size, default=DEFAULT_MAX_METADATA_SIZE,
+        "--max-metadata-size", type=parse_size, default=DEFAULT_MAX_METADATA_SIZE,
-        help="Limit metadata size to protect memory overflow"
+        help="Limit metadata size to protect memory overflow. Provide in human friendly format eg. 1 M, 1 GB"
     )
 
     default_database_dir = os.path.join(appdirs.user_data_dir("magneticod"), "database.sqlite3")

magneticod/magneticod/bittorrent.py

@@ -40,6 +40,7 @@ class DisposablePeer:
         if res != errno.EINPROGRESS:
             raise ConnectionError()
 
+        self.__peer_addr = peer_addr
         self.__info_hash = info_hash
 
         self.__max_metadata_size = max_metadata_size
@@ -211,10 +212,16 @@ class DisposablePeer:
             # Just to make sure that the remote peer supports ut_metadata extension:
             ut_metadata = msg_dict[b"m"][b"ut_metadata"]
             metadata_size = msg_dict[b"metadata_size"]
-            assert metadata_size > 0, "Invalid (empty) metada size"
+            assert metadata_size > 0, "Invalid (empty) metadata size"
-            assert metadata_size < self.__max_metadata_size, "Malicious or malfunctioning peer tried send above " \
+            assert metadata_size < self.__max_metadata_size, "Malicious or malfunctioning peer {}:{} tried send above" \
-                                                             "{} limit metadata size".format(self.__max_metadata_size)
+                                                             " {} max metadata size".format(self.__peer_addr[0],
-        except (AssertionError, KeyError):
+                                                                                            self.__peer_addr[1],
+                                                                                            self.__max_metadata_size)
+        except KeyError:
+            self.when_error()
+            return
+        except AssertionError as e:
+            logging.debug(str(e))
             self.when_error()
             return
 

magneticod/magneticod/dht.py

@@ -30,7 +30,7 @@ InfoHash = bytes
 
 
 class SybilNode:
-    def __init__(self, address: typing.Tuple[str, int], max_metadata_size: int=DEFAULT_MAX_METADATA_SIZE):
+    def __init__(self, address: typing.Tuple[str, int]):
         self.__true_id = self.__random_bytes(20)
 
         self.__socket = socket.socket(type=socket.SOCK_DGRAM)
@@ -43,7 +43,6 @@ class SybilNode:
         self.__routing_table = {}  # type: typing.Dict[NodeID, NodeAddress]
 
         self.__token_secret = self.__random_bytes(4)
-        self.__max_metadata_size = max_metadata_size
         # Maximum number of neighbours (this is a THRESHOLD where, once reached, the search for new neighbours will
         # stop; but until then, the total number of neighbours might exceed the threshold).
         self.__n_max_neighbours = 2000
@@ -51,8 +50,7 @@ class SybilNode:
         logging.info("SybilNode %s on %s initialized!", self.__true_id.hex().upper(), address)
 
     @staticmethod
-    def when_peer_found(info_hash: InfoHash, peer_addr: PeerAddress,
+    def when_peer_found(info_hash: InfoHash, peer_addr: PeerAddress) -> None:
-                        max_metadata_size: int=DEFAULT_MAX_METADATA_SIZE) -> None:
         raise NotImplementedError()
 
     def on_tick(self) -> None:
@@ -204,7 +202,7 @@ class SybilNode:
         else:
             peer_addr = (addr[0], port)
 
-        self.when_peer_found(info_hash, peer_addr, self.__max_metadata_size)
+        self.when_peer_found(info_hash, peer_addr)
 
     def fileno(self) -> int:
         return self.__socket.fileno()