diff --git a/synapse/http/client.py b/synapse/http/client.py
index ad454f4964..ddbfb72228 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -90,45 +90,50 @@ class IPBlacklistingResolver(object):
def resolveHostName(self, recv, hostname, portNumber=0):
r = recv()
- d = defer.Deferred()
addresses = []
- @provider(IResolutionReceiver)
- class EndpointReceiver(object):
- @staticmethod
- def resolutionBegan(resolutionInProgress):
- pass
+ def _callback():
+ r.resolutionBegan(None)
- @staticmethod
- def addressResolved(address):
- ip_address = IPAddress(address.host)
+ has_bad_ip = False
+ for i in addresses:
+ ip_address = IPAddress(i.host)
if check_against_blacklist(
ip_address, self._ip_whitelist, self._ip_blacklist
):
logger.info(
- "Dropped %s from DNS resolution to %s" % (ip_address, hostname)
+ "Dropped %s from DNS resolution to %s due to blacklist" %
+ (ip_address, hostname)
)
- raise SynapseError(403, "IP address blocked by IP blacklist entry")
+ has_bad_ip = True
+
+ # if we have a blacklisted IP, we'd like to raise an error to block the
+ # request, but all we can really do from here is claim that there were no
+ # valid results.
+ if not has_bad_ip:
+ for i in addresses:
+ r.addressResolved(i)
+ r.resolutionComplete()
+ @provider(IResolutionReceiver)
+ class EndpointReceiver(object):
+ @staticmethod
+ def resolutionBegan(resolutionInProgress):
+ pass
+
+ @staticmethod
+ def addressResolved(address):
addresses.append(address)
@staticmethod
def resolutionComplete():
- d.callback(addresses)
+ _callback()
self._reactor.nameResolver.resolveHostName(
EndpointReceiver, hostname, portNumber=portNumber
)
- def _callback(addrs):
- r.resolutionBegan(None)
- for i in addrs:
- r.addressResolved(i)
- r.resolutionComplete()
-
- d.addCallback(_callback)
-
return r
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index ba3ab1d37d..acf87709f2 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -31,6 +31,7 @@ from six.moves import urllib_parse as urlparse
from canonicaljson import json
from twisted.internet import defer
+from twisted.internet.error import DNSLookupError
from twisted.web.resource import Resource
from twisted.web.server import NOT_DONE_YET
@@ -328,9 +329,18 @@ class PreviewUrlResource(Resource):
# handler will return a SynapseError to the client instead of
# blank data or a 500.
raise
+ except DNSLookupError:
+ # DNS lookup returned no results
+ # Note: This will also be the case if one of the resolved IP
+ # addresses is blacklisted
+ raise SynapseError(
+ 502, "DNS resolution failure during URL preview generation",
+ Codes.UNKNOWN
+ )
except Exception as e:
# FIXME: pass through 404s and other error messages nicely
logger.warn("Error downloading %s: %r", url, e)
+
raise SynapseError(
500, "Failed to download content: %s" % (
traceback.format_exception_only(sys.exc_info()[0], e),
|
