From 8520bc3109c2de6175391497941f3fc0b74c08e5 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Fri, 25 Jan 2019 12:38:16 +0000
Subject: [PATCH] Fix Host header sent by MatrixFederationAgent (#4468)

Move the Host header logic down here so that (a) it is used if we reuse the
agent elsewhere, and (b) we can mess about with it with .well-known.
---
 changelog.d/4468.misc                            |  1 +
 .../http/federation/matrix_federation_agent.py   | 10 ++++++++++
 synapse/http/matrixfederationclient.py           |  1 -
 .../federation/test_matrix_federation_agent.py   | 16 ++++++++++++++++
 tests/http/test_fedclient.py                     |  2 +-
 5 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 changelog.d/4468.misc

diff --git a/changelog.d/4468.misc b/changelog.d/4468.misc
new file mode 100644
index 0000000000..9a51434755
--- /dev/null
+++ b/changelog.d/4468.misc
@@ -0,0 +1 @@
+Move SRV logic into the Agent layer
diff --git a/synapse/http/federation/matrix_federation_agent.py b/synapse/http/federation/matrix_federation_agent.py
index 0ec28c6696..1788e9a34a 100644
--- a/synapse/http/federation/matrix_federation_agent.py
+++ b/synapse/http/federation/matrix_federation_agent.py
@@ -19,6 +19,7 @@ from zope.interface import implementer
 from twisted.internet import defer
 from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
 from twisted.web.client import URI, Agent, HTTPConnectionPool
+from twisted.web.http_headers import Headers
 from twisted.web.iweb import IAgent
 
 from synapse.http.endpoint import parse_server_name
@@ -109,6 +110,15 @@ class MatrixFederationAgent(object):
             else:
                 target = pick_server_from_list(server_list)
 
+        # make sure that the Host header is set correctly
+        if headers is None:
+            headers = Headers()
+        else:
+            headers = headers.copy()
+
+        if not headers.hasHeader(b'host'):
+            headers.addRawHeader(b'host', server_name_bytes)
+
         class EndpointFactory(object):
             @staticmethod
             def endpointForURI(_uri):
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 980e912348..bb2e64ed80 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -255,7 +255,6 @@ class MatrixFederationHttpClient(object):
 
         headers_dict = {
             b"User-Agent": [self.version_string_bytes],
-            b"Host": [destination_bytes],
         }
 
         with limiter:
diff --git a/tests/http/federation/test_matrix_federation_agent.py b/tests/http/federation/test_matrix_federation_agent.py
index b32d7566a5..261afb5f41 100644
--- a/tests/http/federation/test_matrix_federation_agent.py
+++ b/tests/http/federation/test_matrix_federation_agent.py
@@ -131,6 +131,10 @@ class MatrixFederationAgentTests(TestCase):
         request = http_server.requests[0]
         self.assertEqual(request.method, b'GET')
         self.assertEqual(request.path, b'/foo/bar')
+        self.assertEqual(
+            request.requestHeaders.getRawHeaders(b'host'),
+            [b'testserv:8448']
+        )
         content = request.content.read()
         self.assertEqual(content, b'')
 
@@ -195,6 +199,10 @@ class MatrixFederationAgentTests(TestCase):
         request = http_server.requests[0]
         self.assertEqual(request.method, b'GET')
         self.assertEqual(request.path, b'/foo/bar')
+        self.assertEqual(
+            request.requestHeaders.getRawHeaders(b'host'),
+            [b'1.2.3.4'],
+        )
 
         # finish the request
         request.finish()
@@ -235,6 +243,10 @@ class MatrixFederationAgentTests(TestCase):
         request = http_server.requests[0]
         self.assertEqual(request.method, b'GET')
         self.assertEqual(request.path, b'/foo/bar')
+        self.assertEqual(
+            request.requestHeaders.getRawHeaders(b'host'),
+            [b'testserv'],
+        )
 
         # finish the request
         request.finish()
@@ -276,6 +288,10 @@ class MatrixFederationAgentTests(TestCase):
         request = http_server.requests[0]
         self.assertEqual(request.method, b'GET')
         self.assertEqual(request.path, b'/foo/bar')
+        self.assertEqual(
+            request.requestHeaders.getRawHeaders(b'host'),
+            [b'testserv'],
+        )
 
         # finish the request
         request.finish()
diff --git a/tests/http/test_fedclient.py b/tests/http/test_fedclient.py
index d37f8f9981..018c77ebcd 100644
--- a/tests/http/test_fedclient.py
+++ b/tests/http/test_fedclient.py
@@ -49,7 +49,6 @@ class FederationClientTests(HomeserverTestCase):
         return hs
 
     def prepare(self, reactor, clock, homeserver):
-
         self.cl = MatrixFederationHttpClient(self.hs)
         self.reactor.lookups["testserv"] = "1.2.3.4"
 
@@ -95,6 +94,7 @@ class FederationClientTests(HomeserverTestCase):
 
         # that should have made it send the request to the transport
         self.assertRegex(transport.value(), b"^GET /foo/bar")
+        self.assertRegex(transport.value(), b"Host: testserv:8008")
 
         # Deferred is still without a result
         self.assertNoResult(test_d)