Merge pull request #688 from matrix-org/matthew/preview_urls

URL previewing support

2 files changed, 197 insertions, 5 deletions

diff --git a/synapse/http/client.py b/synapse/http/client.py
index cbd45b2bbe..6c89b20984 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -15,17 +15,24 @@
 from OpenSSL import SSL
 from OpenSSL.SSL import VERIFY_NONE
 
-from synapse.api.errors import CodeMessageException
+from synapse.api.errors import (
+    CodeMessageException, SynapseError, Codes,
+)
 from synapse.util.logcontext import preserve_context_over_fn
 import synapse.metrics
+from synapse.http.endpoint import SpiderEndpoint
 
 from canonicaljson import encode_canonical_json
 
-from twisted.internet import defer, reactor, ssl
+from twisted.internet import defer, reactor, ssl, protocol
+from twisted.internet.endpoints import SSL4ClientEndpoint, TCP4ClientEndpoint
 from twisted.web.client import (
-    Agent, readBody, FileBodyProducer, PartialDownloadError,
+    BrowserLikeRedirectAgent, ContentDecoderAgent, GzipDecoder, Agent,
+    readBody, FileBodyProducer, PartialDownloadError,
 )
+from twisted.web.http import PotentialDataLoss
 from twisted.web.http_headers import Headers
+from twisted.web._newclient import ResponseDone
 
 from StringIO import StringIO
 
@@ -238,6 +245,107 @@ class SimpleHttpClient(object):
         else:
             raise CodeMessageException(response.code, body)
 
+    # XXX: FIXME: This is horribly copy-pasted from matrixfederationclient.
+    # The two should be factored out.
+
+    @defer.inlineCallbacks
+    def get_file(self, url, output_stream, max_size=None):
+        """GETs a file from a given URL
+        Args:
+            url (str): The URL to GET
+            output_stream (file): File to write the response body to.
+        Returns:
+            A (int,dict,string,int) tuple of the file length, dict of the response
+            headers, absolute URI of the response and HTTP response code.
+        """
+
+        response = yield self.request(
+            "GET",
+            url.encode("ascii"),
+            headers=Headers({
+                b"User-Agent": [self.user_agent],
+            })
+        )
+
+        headers = dict(response.headers.getAllRawHeaders())
+
+        if 'Content-Length' in headers and headers['Content-Length'] > max_size:
+            logger.warn("Requested URL is too large > %r bytes" % (self.max_size,))
+            raise SynapseError(
+                502,
+                "Requested file is too large > %r bytes" % (self.max_size,),
+                Codes.TOO_LARGE,
+            )
+
+        if response.code > 299:
+            logger.warn("Got %d when downloading %s" % (response.code, url))
+            raise SynapseError(
+                502,
+                "Got error %d" % (response.code,),
+                Codes.UNKNOWN,
+            )
+
+        # TODO: if our Content-Type is HTML or something, just read the first
+        # N bytes into RAM rather than saving it all to disk only to read it
+        # straight back in again
+
+        try:
+            length = yield preserve_context_over_fn(
+                _readBodyToFile,
+                response, output_stream, max_size
+            )
+        except Exception as e:
+            logger.exception("Failed to download body")
+            raise SynapseError(
+                502,
+                ("Failed to download remote body: %s" % e),
+                Codes.UNKNOWN,
+            )
+
+        defer.returnValue((length, headers, response.request.absoluteURI, response.code))
+
+
+# XXX: FIXME: This is horribly copy-pasted from matrixfederationclient.
+# The two should be factored out.
+
+class _ReadBodyToFileProtocol(protocol.Protocol):
+    def __init__(self, stream, deferred, max_size):
+        self.stream = stream
+        self.deferred = deferred
+        self.length = 0
+        self.max_size = max_size
+
+    def dataReceived(self, data):
+        self.stream.write(data)
+        self.length += len(data)
+        if self.max_size is not None and self.length >= self.max_size:
+            self.deferred.errback(SynapseError(
+                502,
+                "Requested file is too large > %r bytes" % (self.max_size,),
+                Codes.TOO_LARGE,
+            ))
+            self.deferred = defer.Deferred()
+            self.transport.loseConnection()
+
+    def connectionLost(self, reason):
+        if reason.check(ResponseDone):
+            self.deferred.callback(self.length)
+        elif reason.check(PotentialDataLoss):
+            # stolen from https://github.com/twisted/treq/pull/49/files
+            # http://twistedmatrix.com/trac/ticket/4840
+            self.deferred.callback(self.length)
+        else:
+            self.deferred.errback(reason)
+
+
+# XXX: FIXME: This is horribly copy-pasted from matrixfederationclient.
+# The two should be factored out.
+
+def _readBodyToFile(response, stream, max_size):
+    d = defer.Deferred()
+    response.deliverBody(_ReadBodyToFileProtocol(stream, d, max_size))
+    return d
+
 
 class CaptchaServerHttpClient(SimpleHttpClient):
     """
@@ -269,6 +377,59 @@ class CaptchaServerHttpClient(SimpleHttpClient):
             defer.returnValue(e.response)
 
 
+class SpiderEndpointFactory(object):
+    def __init__(self, hs):
+        self.blacklist = hs.config.url_preview_ip_range_blacklist
+        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,
+                endpoint=TCP4ClientEndpoint,
+                endpoint_kw_args={
+                    'timeout': 15
+                },
+            )
+        elif uri.scheme == "https":
+            tlsPolicy = self.policyForHTTPS.creatorForNetloc(uri.host, uri.port)
+            return SpiderEndpoint(
+                reactor, uri.host, uri.port, self.blacklist,
+                endpoint=SSL4ClientEndpoint,
+                endpoint_kw_args={
+                    'sslContextFactory': tlsPolicy,
+                    'timeout': 15
+                },
+            )
+        else:
+            logger.warn("Can't get endpoint for unrecognised scheme %s", uri.scheme)
+
+
+class SpiderHttpClient(SimpleHttpClient):
+    """
+    Separate HTTP client for spidering arbitrary URLs.
+    Special in that it follows retries and has a UA that looks
+    like a browser.
+
+    used by the preview_url endpoint in the content repo.
+    """
+    def __init__(self, hs):
+        SimpleHttpClient.__init__(self, hs)
+        # clobber the base class's agent and UA:
+        self.agent = ContentDecoderAgent(
+            BrowserLikeRedirectAgent(
+                Agent.usingEndpointFactory(
+                    reactor,
+                    SpiderEndpointFactory(hs)
+                )
+            ), [('gzip', GzipDecoder)]
+        )
+        # We could look like Chrome:
+        # self.user_agent = ("Mozilla/5.0 (%s) (KHTML, like Gecko)
+        #                   Chrome Safari" % hs.version_string)
+
+
 def encode_urlencode_args(args):
     return {k: encode_urlencode_arg(v) for k, v in args.items()}
 
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index bc28a2959a..a456dc19da 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -75,6 +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
@@ -120,7 +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
@@ -174,7 +205,7 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t
                 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: