Merge pull request #8 from whizz/ft_disable_unknown

Add option to deny serving unknown clients

docs/environment.rst

@@ -281,6 +281,14 @@ These environment variables are optional:
   version string. For example to drop versions from 1.0 to 1.2 use
   the regex ``1\.[0-2]\.\d+``.
 
+.. envvar:: DROP_CLIENT_UNKNOWN
+
+  Set to anything non-empty to deny serving clients which do not
+  identify themselves first by issuing the server.version method
+  call with a non-empty client identifier. The connection is dropped 
+  on first actual method call. This might help to filter out simple 
+  robots. This behavior is off by default.
+
 
 Resource Usage Limits
 =====================

electrumx/server/env.py

@@ -69,6 +69,7 @@ def __init__(self, coin=None):
         self.log_level = self.default('LOG_LEVEL', 'info').upper()
         self.donation_address = self.default('DONATION_ADDRESS', '')
         self.drop_client = self.custom("DROP_CLIENT", None, re.compile)
+        self.drop_client_unknown = self.boolean('DROP_CLIENT_UNKNOWN', False)
         self.blacklist_url = self.default('BLACKLIST_URL', self.coin.BLACKLIST_URL)
         self.cache_MB = self.integer('CACHE_MB', 1200)
         self.reorg_limit = self.integer('REORG_LIMIT', self.coin.REORG_LIMIT)

electrumx/server/session.py

@@ -884,6 +884,14 @@ async def handle_request(self, request):
         else:
             handler = None
         method = 'invalid method' if handler is None else request.method
+
+        # If DROP_CLIENT_UNKNOWN is enabled, check if the client identified
+        # by calling server.version previously. If not, disconnect the session
+        if self.env.drop_client_unknown and method != 'server.version' and self.client == 'unknown':
+            self.logger.info(f'disconnecting because client is unknown')
+            raise ReplyAndDisconnect(
+                BAD_REQUEST, f'use server.version to identify client')
+
         self.session_mgr._method_counts[method] += 1
         coro = handler_invocation(handler, request)()
         return await coro

tests/server/test_env.py

@@ -61,10 +61,10 @@ def assert_boolean(env_var, attr, default):
     assert getattr(e, attr) == default
     os.environ[env_var] = 'foo'
     e = Env()
-    assert getattr(e, attr) == True
+    assert getattr(e, attr) is True
     os.environ[env_var] = ''
     e = Env()
-    assert getattr(e, attr) == False
+    assert getattr(e, attr) is False
 
 
 def test_minimal():
@@ -141,6 +141,7 @@ def test_COIN_NET():
     e = Env()
     assert e.coin == lib_coins.TokenPay
 
+
 def test_CACHE_MB():
     assert_integer('CACHE_MB', 'cache_MB', 1200)
 
@@ -158,6 +159,7 @@ def test_SERVICES():
         Service('rpc', NetAddress('::1', 700)),
     ]
 
+
 def test_SERVICES_default_rpc():
     # This has a blank entry between commas
     os.environ['SERVICES'] = 'rpc://foo.bar'
@@ -178,7 +180,7 @@ def test_bad_SERVICES():
     setup_base_env()
     os.environ['SERVICES'] = 'tcp:foo.bar:1234'
     with pytest.raises(ServiceError) as err:
-         Env()
+        Env()
     assert 'invalid service string' in str(err.value)
     os.environ['SERVICES'] = 'xxx://foo.com:50001'
     with pytest.raises(ServiceError) as err:
@@ -197,7 +199,7 @@ def test_onion_SERVICES():
 def test_duplicate_SERVICES():
     setup_base_env()
     os.environ['SERVICES'] = 'tcp://foo.bar:1234,ws://foo.bar:1235'
-    e = Env()
+    Env()
     os.environ['SERVICES'] = 'tcp://foo.bar:1234,ws://foo.bar:1234'
     with pytest.raises(ServiceError) as err:
         Env()
@@ -406,3 +408,17 @@ def test_ban_versions():
 def test_coin_class_provided():
     e = Env(lib_coins.BitcoinSV)
     assert e.coin == lib_coins.BitcoinSV
+
+
+def test_drop_unknown_clients():
+    e = Env()
+    assert e.drop_client_unknown is False
+    os.environ['DROP_CLIENT_UNKNOWN'] = ""
+    e = Env()
+    assert e.drop_client_unknown is False
+    os.environ['DROP_CLIENT_UNKNOWN'] = "1"
+    e = Env()
+    assert e.drop_client_unknown is True
+    os.environ['DROP_CLIENT_UNKNOWN'] = "whatever"
+    e = Env()
+    assert e.drop_client_unknown is True