1 files changed, 57 insertions, 19 deletions

diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index 4775f6707d..a456dc19da 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -22,6 +22,7 @@ from twisted.names.error import DNSNameError, DomainError
 import collections
 import logging
 import random
+import time
 
 
 logger = logging.getLogger(__name__)
@@ -31,7 +32,7 @@ SERVER_CACHE = {}
 
 
 _Server = collections.namedtuple(
-    "_Server", "priority weight host port"
+    "_Server", "priority weight host port expires"
 )
 
 
@@ -74,6 +75,37 @@ def matrix_federation_endpoint(reactor, destination, ssl_context_factory=None,
         return transport_endpoint(reactor, domain, port, **endpoint_kw_args)
 
 
+class SpiderEndpoint(object):
+    """An endpoint which refuses to connect to blacklisted IP addresses
+    Implements twisted.internet.interfaces.IStreamClientEndpoint.
+    """
+    def __init__(self, reactor, host, port, blacklist,
+                 endpoint=TCP4ClientEndpoint, endpoint_kw_args={}):
+        self.reactor = reactor
+        self.host = host
+        self.port = port
+        self.blacklist = blacklist
+        self.endpoint = endpoint
+        self.endpoint_kw_args = endpoint_kw_args
+
+    @defer.inlineCallbacks
+    def connect(self, protocolFactory):
+        address = yield self.reactor.resolve(self.host)
+
+        from netaddr import IPAddress
+        if IPAddress(address) in self.blacklist:
+            raise ConnectError(
+                "Refusing to spider blacklisted IP address %s" % address
+            )
+
+        logger.info("Connecting to %s:%s", address, self.port)
+        endpoint = self.endpoint(
+            self.reactor, address, self.port, **self.endpoint_kw_args
+        )
+        connection = yield endpoint.connect(protocolFactory)
+        defer.returnValue(connection)
+
+
 class SRVClientEndpoint(object):
     """An endpoint which looks up SRV records for a service.
     Cycles through the list of servers starting with each call to connect
@@ -92,7 +124,8 @@ class SRVClientEndpoint(object):
                 host=domain,
                 port=default_port,
                 priority=0,
-                weight=0
+                weight=0,
+                expires=0,
             )
         else:
             self.default_server = None
@@ -118,7 +151,7 @@ class SRVClientEndpoint(object):
                 return self.default_server
             else:
                 raise ConnectError(
-                    "Not server available for %s", self.service_name
+                    "Not server available for %s" % self.service_name
                 )
 
         min_priority = self.servers[0].priority
@@ -153,7 +186,13 @@ class SRVClientEndpoint(object):
 
 
 @defer.inlineCallbacks
-def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE):
+def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=time):
+    cache_entry = cache.get(service_name, None)
+    if cache_entry:
+        if all(s.expires > int(clock.time()) for s in cache_entry):
+            servers = list(cache_entry)
+            defer.returnValue(servers)
+
     servers = []
 
     try:
@@ -166,34 +205,33 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE):
                 and answers[0].type == dns.SRV
                 and answers[0].payload
                 and answers[0].payload.target == dns.Name('.')):
-            raise ConnectError("Service %s unavailable", service_name)
+            raise ConnectError("Service %s unavailable" % service_name)
 
         for answer in answers:
             if answer.type != dns.SRV or not answer.payload:
                 continue
 
             payload = answer.payload
-
             host = str(payload.target)
+            srv_ttl = answer.ttl
 
             try:
                 answers, _, _ = yield dns_client.lookupAddress(host)
             except DNSNameError:
                 continue
 
-            ips = [
-                answer.payload.dottedQuad()
-                for answer in answers
-                if answer.type == dns.A and answer.payload
-            ]
-
-            for ip in ips:
-                servers.append(_Server(
-                    host=ip,
-                    port=int(payload.port),
-                    priority=int(payload.priority),
-                    weight=int(payload.weight)
-                ))
+            for answer in answers:
+                if answer.type == dns.A and answer.payload:
+                    ip = answer.payload.dottedQuad()
+                    host_ttl = min(srv_ttl, answer.ttl)
+
+                    servers.append(_Server(
+                        host=ip,
+                        port=int(payload.port),
+                        priority=int(payload.priority),
+                        weight=int(payload.weight),
+                        expires=int(clock.time()) + host_ttl,
+                    ))
 
         servers.sort()
         cache[service_name] = list(servers)