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authorAndrew Morgan <1342360+anoadragon453@users.noreply.github.com>2019-05-10 10:32:44 -0700
committerGitHub <noreply@github.com>2019-05-10 10:32:44 -0700
commit2f48c4e1ae40869a1bc5dcb36557ad0a0d8a5728 (patch)
tree7b83d18d61d1eaaa38e705ace989ea3cdcb2c82c /synapse/rest/media/v1
parentRevert 085ae346ace418e0fc043ac5f568f85ebf80038e (diff)
downloadsynapse-2f48c4e1ae40869a1bc5dcb36557ad0a0d8a5728.tar.xz
URL preview blacklisting fixes (#5155)
Prevents a SynapseError being raised inside of a IResolutionReceiver and instead opts to just return 0 results. This thus means that we have to lump a failed lookup and a blacklisted lookup together with the same error message, but the substitute should be generic enough to cover both cases.
Diffstat (limited to 'synapse/rest/media/v1')
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py10
1 files changed, 10 insertions, 0 deletions
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),