2 files changed, 13 insertions, 7 deletions
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 902ae7a203..a8e2d8e808 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -380,13 +380,15 @@ class CaptchaServerHttpClient(SimpleHttpClient):
 class SpiderEndpointFactory(object):
     def __init__(self, hs):
         self.blacklist = hs.config.url_preview_ip_range_blacklist
+        if hasattr(hs.config, "url_preview_ip_range_whitelist"):
+            self.whitelist = hs.config.url_preview_ip_range_whitelist
         self.policyForHTTPS = hs.get_http_client_context_factory()
 
     def endpointForURI(self, uri):
         logger.info("Getting endpoint for %s", uri.toBytes())
         if uri.scheme == "http":
             return SpiderEndpoint(
-                reactor, uri.host, uri.port, self.blacklist,
+                reactor, uri.host, uri.port, self.blacklist, self.whitelist,
                 endpoint=TCP4ClientEndpoint,
                 endpoint_kw_args={
                     'timeout': 15
@@ -395,7 +397,7 @@ class SpiderEndpointFactory(object):
         elif uri.scheme == "https":
             tlsPolicy = self.policyForHTTPS.creatorForNetloc(uri.host, uri.port)
             return SpiderEndpoint(
-                reactor, uri.host, uri.port, self.blacklist,
+                reactor, uri.host, uri.port, self.blacklist, self.whitelist,
                 endpoint=SSL4ClientEndpoint,
                 endpoint_kw_args={
                     'sslContextFactory': tlsPolicy,
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index a456dc19da..442696d393 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -79,12 +79,13 @@ 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,
+    def __init__(self, reactor, host, port, blacklist, whitelist,
                  endpoint=TCP4ClientEndpoint, endpoint_kw_args={}):
         self.reactor = reactor
         self.host = host
         self.port = port
         self.blacklist = blacklist
+        self.whitelist = whitelist
         self.endpoint = endpoint
         self.endpoint_kw_args = endpoint_kw_args
 
@@ -93,10 +94,13 @@ class SpiderEndpoint(object):
         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
-            )
+        ip_address = IPAddress(address)
+
+        if ip_address in self.blacklist:
+            if self.whitelist is None or ip_address not in self.whitelist:
+                raise ConnectError(
+                    "Refusing to spider blacklisted IP address %s" % address
+                )
 
         logger.info("Connecting to %s:%s", address, self.port)
         endpoint = self.endpoint(