console: Provide an RFB security proxy implementation

Instead of doing straight passthrough of the RFB protocol from the
tenant sock to the compute socket, insert an RFB security proxy. This
will MITM the initial RFB protocol handshake in order to negotiate an
authentication scheme with the compute node that is distinct from that
used by the tenant.

Based on earlier work by Solly Ross <sross@redhat.com>

Change-Id: I9cc9a380500715e60bd05aa5c29ee46bc6f8d6c2
Co-authored-by: Stephen Finucane <sfinucan@redhat.com>
Implements: bp websocket-proxy-to-host-security

6 files changed, 471 insertions, 2 deletions

diff --git a/nova/cmd/novncproxy.py b/nova/cmd/novncproxy.py
index 4b9f053bd7..954602542d 100644
--- a/nova/cmd/novncproxy.py
+++ b/nova/cmd/novncproxy.py
@@ -25,6 +25,7 @@ from nova.cmd import baseproxy
 import nova.conf
 from nova.conf import vnc
 from nova import config
+from nova.console.securityproxy import rfb
 
 
 CONF = nova.conf.CONF
@@ -36,6 +37,13 @@ def main():
     CONF.set_default('web', '/usr/share/novnc')
     config.parse_args(sys.argv)
 
+    # TODO(stephenfin): Always enable the security proxy once we support RFB
+    # version 3.3, as used in XenServer.
+    security_proxy = None
+    if CONF.compute_driver != 'xenapi.XenAPIDriver':
+        security_proxy = rfb.RFBSecurityProxy()
+
     baseproxy.proxy(
         host=CONF.vnc.novncproxy_host,
-        port=CONF.vnc.novncproxy_port)
+        port=CONF.vnc.novncproxy_port,
+        security_proxy=security_proxy)
diff --git a/nova/console/securityproxy/rfb.py b/nova/console/securityproxy/rfb.py
new file mode 100644
index 0000000000..6aea4712f9
--- /dev/null
+++ b/nova/console/securityproxy/rfb.py
@@ -0,0 +1,190 @@
+# Copyright (c) 2014-2016 Red Hat, Inc
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import struct
+
+from oslo_config import cfg
+from oslo_log import log as logging
+import six
+
+from nova.console.rfb import auth
+from nova.console.rfb import auths
+from nova.console.securityproxy import base
+from nova import exception
+from nova.i18n import _, _LI
+
+LOG = logging.getLogger(__name__)
+
+CONF = cfg.CONF
+
+
+class RFBSecurityProxy(base.SecurityProxy):
+    """RFB Security Proxy Negotiation Helper.
+
+    This class proxies the initial setup of the RFB connection between the
+    client and the server. Then, when the RFB security negotiation step
+    arrives, it intercepts the communication, posing as a server with the
+    "None" authentication type to the client, and acting as a client (via
+    the methods below) to the server. After security negotiation, normal
+    proxying can be used.
+
+    Note: this code mandates RFB version 3.8, since this is supported by any
+    client and server impl written in the past 10+ years.
+
+    See the general RFB specification at:
+
+      https://tools.ietf.org/html/rfc6143
+    """
+
+    def __init__(self):
+        self.auth_schemes = auths.RFBAuthSchemeList()
+
+    def _make_var_str(self, message):
+        message_str = six.text_type(message)
+        message_bytes = message_str.encode('utf-8')
+        message_len = struct.pack("!I", len(message_bytes))
+        return message_len + message_bytes
+
+    def _fail(self, tenant_sock, compute_sock, message):
+        # Tell the client there's been a problem
+        result_code = struct.pack("!I", 1)
+        tenant_sock.sendall(result_code + self._make_var_str(message))
+
+        if compute_sock is not None:
+            # Tell the server that there's been a problem
+            # by sending the "Invalid" security type
+            compute_sock.sendall(auth.AUTH_STATUS_FAIL)
+
+    def _parse_version(self, version_str):
+        maj_str = version_str[4:7]
+        min_str = version_str[8:11]
+
+        return float("%d.%d" % (int(maj_str), int(min_str)))
+
+    def connect(self, tenant_sock, compute_sock):
+        """Initiate the RFB connection process.
+
+        This method performs the initial ProtocolVersion
+        and Security messaging, and returns the socket-like
+        object to use to communicate with the server securely.
+        If an error occurs SecurityProxyNegotiationFailed
+        will be raised.
+        """
+
+        def recv(sock, num):
+            b = sock.recv(num)
+            if len(b) != num:
+                reason = _("Incorrect read from socket, wanted %(wanted)d "
+                           "bytes but got %(got)d. Socket returned "
+                           "%(result)r") % {'wanted': num, 'got': len(b),
+                                            'result': b}
+                raise exception.RFBAuthHandshakeFailed(reason=reason)
+            return b
+
+        # Negotiate version with compute server
+        compute_version = recv(compute_sock, auth.VERSION_LENGTH)
+        LOG.debug("Got version string '%s' from compute node",
+                  compute_version[:-1])
+
+        if self._parse_version(compute_version) != 3.8:
+            reason = _("Security proxying requires RFB protocol "
+                       "version 3.8, but server sent %s"), compute_version[:-1]
+            raise exception.SecurityProxyNegotiationFailed(reason=reason)
+        compute_sock.sendall(compute_version)
+
+        # Negotiate version with tenant
+        tenant_sock.sendall(compute_version)
+        tenant_version = recv(tenant_sock, auth.VERSION_LENGTH)
+        LOG.debug("Got version string '%s' from tenant",
+                  tenant_version[:-1])
+
+        if self._parse_version(tenant_version) != 3.8:
+            reason = _("Security proxying requires RFB protocol version "
+                       "3.8, but tenant asked for %s"), tenant_version[:-1]
+            raise exception.SecurityProxyNegotiationFailed(reason=reason)
+
+        # Negotiate security with server
+        permitted_auth_types_cnt = six.byte2int(recv(compute_sock, 1))
+
+        if permitted_auth_types_cnt == 0:
+            reason_len_raw = recv(compute_sock, 4)
+            reason_len = struct.unpack('!I', reason_len_raw)[0]
+            reason = recv(compute_sock, reason_len)
+
+            tenant_sock.sendall(auth.AUTH_STATUS_FAIL +
+                                reason_len_raw + reason)
+
+            raise exception.SecurityProxyNegotiationFailed(reason=reason)
+
+        f = recv(compute_sock, permitted_auth_types_cnt)
+        permitted_auth_types = []
+        for auth_type in f:
+            if isinstance(auth_type, six.string_types):
+                auth_type = ord(auth_type)
+            permitted_auth_types.append(auth_type)
+
+        LOG.debug("The server sent security types %s", permitted_auth_types)
+
+        # Negotiate security with client before we say "ok" to the server
+        # send 1:[None]
+        tenant_sock.sendall(auth.AUTH_STATUS_PASS +
+                            six.int2byte(auth.AuthType.NONE))
+        client_auth = six.byte2int(recv(tenant_sock, 1))
+
+        if client_auth != auth.AuthType.NONE:
+            self._fail(tenant_sock, compute_sock,
+                       _("Only the security type None (%d) is supported") %
+                       auth.AuthType.NONE)
+
+            reason = _("Client requested a security type other than "
+                       " None (%(none_code)d): "
+                       "%(auth_type)s") % {
+                           'auth_type': client_auth,
+                           'none_code': auth.AuthType.NONE}
+            raise exception.SecurityProxyNegotiationFailed(reason=reason)
+
+        try:
+            scheme = self.auth_schemes.find_scheme(permitted_auth_types)
+        except exception.RFBAuthNoAvailableScheme as e:
+            # Intentionally don't tell client what really failed
+            # as that's information leakage
+            self._fail(tenant_sock, compute_sock,
+                       _("Unable to negotiate security with server"))
+            raise exception.SecurityProxyNegotiationFailed(
+                reason=_("No compute auth available: %s") % six.text_type(e))
+
+        compute_sock.sendall(six.int2byte(scheme.security_type()))
+
+        LOG.debug("Using security type %d with server, None with client",
+                  scheme.security_type())
+
+        try:
+            compute_sock = scheme.security_handshake(compute_sock)
+        except exception.RFBAuthHandshakeFailed as e:
+            # Intentionally don't tell client what really failed
+            # as that's information leakage
+            self._fail(tenant_sock, None,
+                       _("Unable to negotiate security with server"))
+            LOG.debug("Auth failed %s", six.text_type(e))
+            raise exception.SecurityProxyNegotiationFailed(
+                reason="Auth handshake failed")
+
+        LOG.info(_LI("Finished security handshake, resuming normal proxy "
+                     "mode using secured socket"))
+
+        # we can just proxy the security result -- if the server security
+        # negotiation fails, we want the client to think it has failed
+
+        return compute_sock
diff --git a/nova/console/websocketproxy.py b/nova/console/websocketproxy.py
index b87abb17bb..d93d61ac6b 100644
--- a/nova/console/websocketproxy.py
+++ b/nova/console/websocketproxy.py
@@ -80,7 +80,7 @@ class TenantSock(object):
         self.reqhandler.send_frames([encodeutils.safe_encode(data)])
 
     def finish_up(self):
-        self.reqhandler.send_frames([b''.join([self.queue])])
+        self.reqhandler.send_frames([b''.join(self.queue)])
 
     def close(self):
         self.finish_up()
diff --git a/nova/tests/unit/console/securityproxy/__init__.py b/nova/tests/unit/console/securityproxy/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/nova/tests/unit/console/securityproxy/__init__.py
diff --git a/nova/tests/unit/console/securityproxy/test_rfb.py b/nova/tests/unit/console/securityproxy/test_rfb.py
new file mode 100644
index 0000000000..e6c284e4d7
--- /dev/null
+++ b/nova/tests/unit/console/securityproxy/test_rfb.py
@@ -0,0 +1,248 @@
+# Copyright (c) 2014-2016 Red Hat, Inc
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Tests the Console Security Proxy Framework."""
+
+import six
+
+import mock
+
+from nova.console.rfb import auth
+from nova.console.rfb import authnone
+from nova.console.securityproxy import rfb
+from nova import exception
+from nova import test
+
+
+class RFBSecurityProxyTestCase(test.NoDBTestCase):
+    """Test case for the base RFBSecurityProxy."""
+
+    def setUp(self):
+        super(RFBSecurityProxyTestCase, self).setUp()
+        self.manager = mock.Mock()
+        self.tenant_sock = mock.Mock()
+        self.compute_sock = mock.Mock()
+
+        self.tenant_sock.recv.side_effect = []
+        self.compute_sock.recv.side_effect = []
+
+        self.expected_manager_calls = []
+        self.expected_tenant_calls = []
+        self.expected_compute_calls = []
+
+        self.proxy = rfb.RFBSecurityProxy()
+
+    def _assert_expected_calls(self):
+        self.assertEqual(self.expected_manager_calls,
+                         self.manager.mock_calls)
+        self.assertEqual(self.expected_tenant_calls,
+                         self.tenant_sock.mock_calls)
+        self.assertEqual(self.expected_compute_calls,
+                         self.compute_sock.mock_calls)
+
+    def _version_handshake(self):
+        full_version_str = "RFB 003.008\n"
+
+        self._expect_compute_recv(auth.VERSION_LENGTH, full_version_str)
+        self._expect_compute_send(full_version_str)
+
+        self._expect_tenant_send(full_version_str)
+        self._expect_tenant_recv(auth.VERSION_LENGTH, full_version_str)
+
+    def _to_binary(self, val):
+        if type(val) != six.binary_type:
+            val = six.binary_type(val, 'utf-8')
+        return val
+
+    def _expect_tenant_send(self, val):
+        val = self._to_binary(val)
+        self.expected_tenant_calls.append(mock.call.sendall(val))
+
+    def _expect_compute_send(self, val):
+        val = self._to_binary(val)
+        self.expected_compute_calls.append(mock.call.sendall(val))
+
+    def _expect_tenant_recv(self, amt, ret_val):
+        ret_val = self._to_binary(ret_val)
+        self.expected_tenant_calls.append(mock.call.recv(amt))
+        self.tenant_sock.recv.side_effect = (
+            list(self.tenant_sock.recv.side_effect) + [ret_val])
+
+    def _expect_compute_recv(self, amt, ret_val):
+        ret_val = self._to_binary(ret_val)
+        self.expected_compute_calls.append(mock.call.recv(amt))
+        self.compute_sock.recv.side_effect = (
+            list(self.compute_sock.recv.side_effect) + [ret_val])
+
+    def test_fail(self):
+        self._expect_tenant_send("\x00\x00\x00\x01\x00\x00\x00\x04blah")
+
+        self.proxy._fail(self.tenant_sock, None, 'blah')
+
+        self._assert_expected_calls()
+
+    def test_fail_server_message(self):
+        self._expect_tenant_send("\x00\x00\x00\x01\x00\x00\x00\x04blah")
+        self._expect_compute_send("\x00")
+
+        self.proxy._fail(self.tenant_sock, self.compute_sock, 'blah')
+
+        self._assert_expected_calls()
+
+    def test_parse_version(self):
+        res = self.proxy._parse_version("RFB 012.034\n")
+        self.assertEqual(12.34, res)
+
+    def test_fails_on_compute_version(self):
+        for full_version_str in ["RFB 003.007\n", "RFB 003.009\n"]:
+            self._expect_compute_recv(auth.VERSION_LENGTH, full_version_str)
+
+            self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                              self.proxy.connect,
+                              self.tenant_sock,
+                              self.compute_sock)
+            self._assert_expected_calls()
+
+    def test_fails_on_tenant_version(self):
+        full_version_str = "RFB 003.008\n"
+
+        for full_version_str_invalid in ["RFB 003.007\n", "RFB 003.009\n"]:
+            self._expect_compute_recv(auth.VERSION_LENGTH, full_version_str)
+            self._expect_compute_send(full_version_str)
+
+            self._expect_tenant_send(full_version_str)
+            self._expect_tenant_recv(auth.VERSION_LENGTH,
+                                     full_version_str_invalid)
+
+            self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                              self.proxy.connect,
+                              self.tenant_sock,
+                              self.compute_sock)
+            self._assert_expected_calls()
+
+    def test_fails_on_sec_type_cnt_zero(self):
+        self.proxy._fail = mock.Mock()
+
+        self._version_handshake()
+
+        self._expect_compute_recv(1, "\x00")
+        self._expect_compute_recv(4, "\x00\x00\x00\x06")
+        self._expect_compute_recv(6, "cheese")
+        self._expect_tenant_send("\x00\x00\x00\x00\x06cheese")
+
+        self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                          self.proxy.connect,
+                          self.tenant_sock,
+                          self.compute_sock)
+
+        self._assert_expected_calls()
+
+    @mock.patch.object(authnone.RFBAuthSchemeNone, "security_handshake")
+    def test_full_run(self, mock_handshake):
+        new_sock = mock.MagicMock()
+        mock_handshake.return_value = new_sock
+
+        self._version_handshake()
+
+        self._expect_compute_recv(1, "\x02")
+        self._expect_compute_recv(2, "\x01\x02")
+
+        self._expect_tenant_send("\x01\x01")
+        self._expect_tenant_recv(1, "\x01")
+
+        self._expect_compute_send("\x01")
+
+        self.assertEqual(new_sock, self.proxy.connect(
+            self.tenant_sock, self.compute_sock))
+
+        mock_handshake.assert_called_once_with(self.compute_sock)
+        self._assert_expected_calls()
+
+    def test_client_auth_invalid_fails(self):
+        self.proxy._fail = self.manager.proxy._fail
+        self.proxy.security_handshake = self.manager.proxy.security_handshake
+
+        self._version_handshake()
+
+        self._expect_compute_recv(1, "\x02")
+        self._expect_compute_recv(2, "\x01\x02")
+
+        self._expect_tenant_send("\x01\x01")
+        self._expect_tenant_recv(1, "\x02")
+
+        self.expected_manager_calls.append(
+            mock.call.proxy._fail(self.tenant_sock,
+                                  self.compute_sock,
+                                  "Only the security type "
+                                  "None (1) is supported"))
+
+        self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                          self.proxy.connect,
+                          self.tenant_sock,
+                          self.compute_sock)
+        self._assert_expected_calls()
+
+    def test_exception_in_choose_security_type_fails(self):
+        self.proxy._fail = self.manager.proxy._fail
+        self.proxy.security_handshake = self.manager.proxy.security_handshake
+
+        self._version_handshake()
+
+        self._expect_compute_recv(1, "\x02")
+        self._expect_compute_recv(2, "\x02\x05")
+
+        self._expect_tenant_send("\x01\x01")
+        self._expect_tenant_recv(1, "\x01")
+
+        self.expected_manager_calls.extend([
+            mock.call.proxy._fail(
+                self.tenant_sock, self.compute_sock,
+                'Unable to negotiate security with server')])
+
+        self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                          self.proxy.connect,
+                          self.tenant_sock,
+                          self.compute_sock)
+
+        self._assert_expected_calls()
+
+    @mock.patch.object(authnone.RFBAuthSchemeNone, "security_handshake")
+    def test_exception_security_handshake_fails(self, mock_auth):
+        self.proxy._fail = self.manager.proxy._fail
+
+        self._version_handshake()
+
+        self._expect_compute_recv(1, "\x02")
+        self._expect_compute_recv(2, "\x01\x02")
+
+        self._expect_tenant_send("\x01\x01")
+        self._expect_tenant_recv(1, "\x01")
+
+        self._expect_compute_send("\x01")
+
+        ex = exception.RFBAuthHandshakeFailed(reason="crackers")
+        mock_auth.side_effect = ex
+
+        self.expected_manager_calls.extend([
+            mock.call.proxy._fail(self.tenant_sock, None,
+                                  'Unable to negotiate security with server')])
+
+        self.assertRaises(exception.SecurityProxyNegotiationFailed,
+                          self.proxy.connect,
+                          self.tenant_sock,
+                          self.compute_sock)
+
+        mock_auth.assert_called_once_with(self.compute_sock)
+        self._assert_expected_calls()
diff --git a/releasenotes/notes/websocket-proxy-to-host-security-c3eca0647b0cbc02.yaml b/releasenotes/notes/websocket-proxy-to-host-security-c3eca0647b0cbc02.yaml
index 017bf386fd..f9588c3b4b 100644
--- a/releasenotes/notes/websocket-proxy-to-host-security-c3eca0647b0cbc02.yaml
+++ b/releasenotes/notes/websocket-proxy-to-host-security-c3eca0647b0cbc02.yaml
@@ -9,3 +9,26 @@ features:
     - ``vencrypt_client_key``
     - ``vencrypt_client_cert``
     - ``vencrypt_ca_certs``
+  - |
+    The *nova-novncproxy* server can now be configured to do a security
+    negotiation with the compute node VNC server. If the VeNCrypt auth scheme
+    is enabled, this establishes a TLS session to provide encryption of all
+    data. The proxy will validate the x509 certs issued by the remote server to
+    ensure it is connecting to a valid compute node. The proxy can also send
+    its own x509 cert to allow the compute node to validate that the connection
+    comes from the official proxy server.
+upgrade:
+  - |
+    To make use of VeNCrypt, configuration steps are required for both the
+    `nova-novncproxy` service and libvirt on all the compute nodes. The
+    ``/etc/libvirt/qemu.conf`` file should be modified to set the ``vnc_tls``
+    option to ``1``, and optionally the ``vnc_tls_x509_verify`` option to
+    ``1``. Certificates must also be deployed on the compute node.
+
+    The ``nova.conf`` file should have the ``auth_schemes`` parameter in the
+    ``vnc`` group set. If there are a mix of compute nodes, some with VeNCrypt
+    enabled and others with it disabled, then the ``auth_schemes``
+    configuration option should be set to ``['vencrypt', 'none']``.
+
+    Once all compute nodes have VeNCrypt enabled, the ``auth_schemes``
+    parameter can be set to just ``['vencrypt']``.