From 5af046fd4e6387cdbf8bf65ea4c2039a4019b64b Mon Sep 17 00:00:00 2001
From: Brian Haley <bhaley@redhat.com>
Date: Thu, 27 Feb 2020 17:33:28 -0500
Subject: [PATCH] Remove extra header fields in proxied metadata requests

If a user specifies a header in their request for metadata,
it could override what the proxy would have inserted on their
behalf. Make sure to remove any headers we don't want, and
override something that might be present in the request.
If the agent somehow gets a request with both headers it will
silently drop it.

Change-Id: Id6c103b7bcebe441c27c6049d349d84ba7fd15a6
Closes-bug: #1865036
---
 neutron/agent/metadata/agent.py               |  7 ++++++
 neutron/agent/metadata/driver.py              |  7 +++++-
 .../tests/unit/agent/metadata/test_agent.py   | 25 +++++++++++++++++++
 .../tests/unit/agent/metadata/test_driver.py  |  1 +
 ...header-vulnerability-60c44eb7c76d560c.yaml |  8 ++++++
 5 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 releasenotes/notes/metadata-proxy-header-vulnerability-60c44eb7c76d560c.yaml

diff --git a/neutron/agent/metadata/agent.py b/neutron/agent/metadata/agent.py
index 0ef370bed72..456689bf521 100644
--- a/neutron/agent/metadata/agent.py
+++ b/neutron/agent/metadata/agent.py
@@ -158,6 +158,13 @@ class MetadataProxyHandler(object):
         network_id = req.headers.get('X-Neutron-Network-ID')
         router_id = req.headers.get('X-Neutron-Router-ID')
 
+        # Only one should be given, drop since it could be spoofed
+        if network_id and router_id:
+            LOG.debug("Both network and router IDs were specified in proxy "
+                      "request, but only a single one of the two is allowed, "
+                      "dropping")
+            return None, None
+
         ports = self._get_ports(remote_address, network_id, router_id)
         LOG.debug("Gotten ports for remote_address %(remote_address)s, "
                   "network_id %(network_id)s, router_id %(router_id)s are: "
diff --git a/neutron/agent/metadata/driver.py b/neutron/agent/metadata/driver.py
index 93f78b199b1..1ae61a334d1 100644
--- a/neutron/agent/metadata/driver.py
+++ b/neutron/agent/metadata/driver.py
@@ -65,7 +65,8 @@ defaults
 listen listener
     bind %(host)s:%(port)s
     server metadata %(unix_socket_path)s
-    http-request add-header X-Neutron-%(res_type)s-ID %(res_id)s
+    http-request del-header X-Neutron-%(res_type_del)s-ID
+    http-request set-header X-Neutron-%(res_type)s-ID %(res_id)s
 """
 
 
@@ -128,12 +129,16 @@ class HaproxyConfigurator(object):
             'log_level': self.log_level,
             'log_tag': self.log_tag
         }
+        # If using the network ID, delete any spurious router ID that might
+        # have been in the request, same for network ID when using router ID.
         if self.network_id:
             cfg_info['res_type'] = 'Network'
             cfg_info['res_id'] = self.network_id
+            cfg_info['res_type_del'] = 'Router'
         else:
             cfg_info['res_type'] = 'Router'
             cfg_info['res_id'] = self.router_id
+            cfg_info['res_type_del'] = 'Network'
 
         haproxy_cfg = _HAPROXY_CONFIG_TEMPLATE % cfg_info
         LOG.debug("haproxy_cfg = %s", haproxy_cfg)
diff --git a/neutron/tests/unit/agent/metadata/test_agent.py b/neutron/tests/unit/agent/metadata/test_agent.py
index 63436d80ad4..f3e3484371e 100644
--- a/neutron/tests/unit/agent/metadata/test_agent.py
+++ b/neutron/tests/unit/agent/metadata/test_agent.py
@@ -241,6 +241,9 @@ class _TestMetadataProxyHandlerCacheMixin(object):
 
         expected = []
 
+        if networks and router_id:
+            return (instance_id, tenant_id)
+
         if router_id:
             expected.append(
                 mock.call(
@@ -332,6 +335,28 @@ class _TestMetadataProxyHandlerCacheMixin(object):
             (None, None)
         )
 
+    def test_get_instance_id_network_id_and_router_id_invalid(self):
+        network_id = 'the_nid'
+        router_id = 'the_rid'
+        headers = {
+            'X-Neutron-Network-ID': network_id,
+            'X-Neutron-Router-ID': router_id
+        }
+
+        # The call should never do a port lookup, but mock it to verify
+        ports = [
+            [{'device_id': 'device_id',
+              'tenant_id': 'tenant_id',
+              'network_id': network_id}]
+        ]
+
+        self.assertEqual(
+            self._get_instance_and_tenant_id_helper(headers, ports,
+                                                    networks=(network_id,),
+                                                    router_id=router_id),
+            (None, None)
+        )
+
     def _proxy_request_test_helper(self, response_code=200, method='GET'):
         hdrs = {'X-Forwarded-For': '8.8.8.8'}
         body = 'body'
diff --git a/neutron/tests/unit/agent/metadata/test_driver.py b/neutron/tests/unit/agent/metadata/test_driver.py
index df044cc9e7d..ade8d10ca5c 100644
--- a/neutron/tests/unit/agent/metadata/test_driver.py
+++ b/neutron/tests/unit/agent/metadata/test_driver.py
@@ -157,6 +157,7 @@ class TestMetadataDriverProcess(base.BaseTestCase):
                 'unix_socket_path': self.METADATA_SOCKET,
                 'res_type': 'Router',
                 'res_id': router_id,
+                'res_type_del': 'Network',
                 'pidfile': self.PIDFILE,
                 'log_level': 'debug',
                 'log_tag': log_tag}
diff --git a/releasenotes/notes/metadata-proxy-header-vulnerability-60c44eb7c76d560c.yaml b/releasenotes/notes/metadata-proxy-header-vulnerability-60c44eb7c76d560c.yaml
new file mode 100644
index 00000000000..1af9d8a468c
--- /dev/null
+++ b/releasenotes/notes/metadata-proxy-header-vulnerability-60c44eb7c76d560c.yaml
@@ -0,0 +1,8 @@
+---
+security:
+  - |
+    A change was made to the metadata proxy to not allow a user to override
+    header values, it will now always insert the correct information and
+    remove unnecessary fields before sending requests to the metadata agent.
+    For more information, see bug
+    `1865036 <https://bugs.launchpad.net/neutron/+bug/1865036>`_.