Extract constants (fixes #37), allows you to specify a size limit and database path as an argument

magneticod/magneticod/__main__.py

@@ -27,18 +27,15 @@ import time
 import typing
 
 import appdirs
+import humanfriendly
 
+from .constants import TICK_INTERVAL, MAX_ACTIVE_PEERS_PER_INFO_HASH, DEFAULT_MAX_METADATA_SIZE
 from . import __version__
 from . import bittorrent
 from . import dht
 from . import persistence
 
 
-TICK_INTERVAL = 1  # in seconds (soft constraint)
-# maximum (inclusive) number of active (disposable) peers to fetch the metadata per info hash at the same time:
-MAX_ACTIVE_PEERS_PER_INFO_HASH = 5
-
-
 # Global variables are bad bla bla bla, BUT these variables are used so many times that I think it is justified; else
 # the signatures of many functions are literally cluttered.
 #
@@ -64,7 +61,7 @@ def main():
 
     # noinspection PyBroadException
     try:
-        path = os.path.join(appdirs.user_data_dir("magneticod"), "database.sqlite3")
+        path =arguments.database_file
         database = persistence.Database(path)
     except:
         logging.exception("could NOT connect to the database!")
@@ -72,7 +69,7 @@ def main():
 
     complete_info_hashes = database.get_complete_info_hashes()
 
-    node = dht.SybilNode(arguments.node_addr)
+    node = dht.SybilNode(arguments.node_addr, max_metadata_size=arguments.metadata_size_limit)
     node.when_peer_found = on_peer_found
 
     selector.register(node, selectors.EVENT_READ)
@@ -92,14 +89,14 @@ def main():
     return 0
 
 
-def on_peer_found(info_hash: dht.InfoHash, peer_address) -> None:
+def on_peer_found(info_hash: dht.InfoHash, peer_address, max_metadata_size: int=DEFAULT_MAX_METADATA_SIZE) -> None:
     global selector, peers, complete_info_hashes
 
     if len(peers[info_hash]) > MAX_ACTIVE_PEERS_PER_INFO_HASH or info_hash in complete_info_hashes:
         return
 
     try:
-        peer = bittorrent.DisposablePeer(info_hash, peer_address)
+        peer = bittorrent.DisposablePeer(info_hash, peer_address, max_metadata_size)
     except ConnectionError:
         return
 
@@ -171,6 +168,13 @@ def loop() -> None:
                 selector.modify(fileobj, selectors.EVENT_READ)
 
 
+def parse_size(value: str) -> int:
+    try:
+        return humanfriendly.parse_size(value)
+    except humanfriendly.InvalidSize as e:
+        raise argparse.ArgumentTypeError("Invalid argument. {}".format(e))
+
+
 def parse_cmdline_arguments() -> typing.Optional[argparse.Namespace]:
     parser = argparse.ArgumentParser(
         description="Autonomous BitTorrent DHT crawler and metadata fetcher.",
@@ -194,13 +198,25 @@ def parse_cmdline_arguments() -> typing.Optional[argparse.Namespace]:
         allow_abbrev=False,
         formatter_class=argparse.RawDescriptionHelpFormatter
     )
+
     parser.add_argument(
         "--node-addr", action="store", type=str, required=False,
         help="the address of the (DHT) node magneticod will use"
     )
 
-    args = parser.parse_args(sys.argv[1:])
+    parser.add_argument(
+        "--metadata-size-limit", type=parse_size, default=DEFAULT_MAX_METADATA_SIZE,
+        help="Limit metadata size to protect memory overflow"
+    )
 
+    default_database_dir = os.path.join(appdirs.user_data_dir("magneticod"), "database.sqlite3")
+    parser.add_argument(
+        "--database-file", type=str, default=default_database_dir,
+        help="Path to database file (default: {})".format(default_database_dir)
+    )
+
+    args = parser.parse_args(sys.argv[1:])
+    print(args.metadata_size_limit)
     args.node_addr = parse_ip_port(args.node_addr) if args.node_addr else ("0.0.0.0", 0)
     if args.node_addr is None:
         logging.critical("Invalid node address supplied!")

magneticod/magneticod/bittorrent.py

@@ -21,15 +21,14 @@ import typing
 import os
 
 from . import bencode
-
+from .constants import DEFAULT_MAX_METADATA_SIZE
-MAX_METADATA_SIZE = 5*1024*1024
 
 InfoHash = bytes
 PeerAddress = typing.Tuple[str, int]
 
 
 class DisposablePeer:
-    def __init__(self, info_hash: InfoHash, peer_addr: PeerAddress):
+    def __init__(self, info_hash: InfoHash, peer_addr: PeerAddress, max_metadata_size: int= DEFAULT_MAX_METADATA_SIZE):
         self.__socket = socket.socket()
         self.__socket.setblocking(False)
         # To reduce the latency:
@@ -43,6 +42,8 @@ class DisposablePeer:
 
         self.__info_hash = info_hash
 
+        self.__max_metadata_size = max_metadata_size
+
         self.__incoming_buffer = bytearray()
         self.__outgoing_buffer = bytearray()
 
@@ -211,7 +212,8 @@ class DisposablePeer:
             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 < MAX_METADATA_SIZE, "Malicious or malfunctioning peer tried send a huge metadata size"
+            assert metadata_size < self.__max_metadata_size, "Malicious or malfunctioning peer tried send above " \
+                                                             "{} limit metadata size".format(self.__max_metadata_size)
         except (AssertionError, KeyError):
             self.when_error()
             return

magneticod/magneticod/constants.py

@@ -0,0 +1,11 @@
+# coding=utf-8
+DEFAULT_MAX_METADATA_SIZE = 10 * 1024 * 1024
+BOOTSTRAPPING_NODES = [
+    ("router.bittorrent.com", 6881),
+    ("dht.transmissionbt.com", 6881)
+]
+PENDING_INFO_HASHES = 10
+
+TICK_INTERVAL = 1  # in seconds (soft constraint)
+ # maximum (inclusive) number of active (disposable) peers to fetch the metadata per info hash at the same time:
+MAX_ACTIVE_PEERS_PER_INFO_HASH = 5

magneticod/magneticod/dht.py

@@ -20,6 +20,7 @@ import socket
 import typing
 import os
 
+from .constants import BOOTSTRAPPING_NODES, DEFAULT_MAX_METADATA_SIZE
 from . import bencode
 
 NodeID = bytes
@@ -28,14 +29,8 @@ PeerAddress = typing.Tuple[str, int]
 InfoHash = bytes
 
 
-BOOTSTRAPPING_NODES = [
-    ("router.bittorrent.com", 6881),
-    ("dht.transmissionbt.com", 6881)
-]
-
-
 class SybilNode:
-    def __init__(self, address: typing.Tuple[str, int]):
+    def __init__(self, address: typing.Tuple[str, int], max_metadata_size: int=DEFAULT_MAX_METADATA_SIZE):
         self.__true_id = self.__random_bytes(20)
 
         self.__socket = socket.socket(type=socket.SOCK_DGRAM)
@@ -48,7 +43,7 @@ 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
@@ -56,7 +51,8 @@ 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) -> None:
+    def when_peer_found(info_hash: InfoHash, peer_addr: PeerAddress,
+                        max_metadata_size: int=DEFAULT_MAX_METADATA_SIZE) -> None:
         raise NotImplementedError()
 
     def on_tick(self) -> None:
@@ -208,7 +204,7 @@ class SybilNode:
         else:
             peer_addr = (addr[0], port)
 
-        self.when_peer_found(info_hash, peer_addr)
+        self.when_peer_found(info_hash, peer_addr, self.max_metadata_size)
 
     def fileno(self) -> int:
         return self.__socket.fileno()

magneticod/magneticod/persistence.py

@@ -18,11 +18,9 @@ import time
 import typing
 import os
 
-from . import bencode
-
-
 # threshold for pending info hashes before being committed to database:
-PENDING_INFO_HASHES = 10
+
+from .constants import PENDING_INFO_HASHES
 
 
 class Database:

magneticod/setup.py

@@ -23,7 +23,8 @@ setup(
 
     install_requires=[
         "appdirs >= 1.4.3",
-        "bencoder.pyx >= 1.1.3"
+        "bencoder.pyx >= 1.1.3",
+        "humanfriendly"
     ],
 
     classifiers=[