Implements the blueprint for enabling the setting of the root/admin password on an instance.

It uses a new xenapi plugin 'agent' that handles communication to/from the agent running on the guest.

nova/api/openstack/servers.py

@@ -165,15 +165,18 @@ class Controller(wsgi.Controller):
         if not inst_dict:
             return faults.Fault(exc.HTTPUnprocessableEntity())
 
+        ctxt = req.environ['nova.context']
         update_dict = {}
         if 'adminPass' in inst_dict['server']:
             update_dict['admin_pass'] = inst_dict['server']['adminPass']
+            try:
+                self.compute_api.set_admin_password(ctxt, id)
+            except exception.TimeoutException, e:
+                return exc.HTTPRequestTimeout()
         if 'name' in inst_dict['server']:
             update_dict['display_name'] = inst_dict['server']['name']
-
         try:
-            self.compute_api.update(req.environ['nova.context'], id,
+            self.compute_api.update(ctxt, id, **update_dict)
-                                    **update_dict)
         except exception.NotFound:
             return faults.Fault(exc.HTTPNotFound())
         return exc.HTTPNoContent()

nova/compute/api.py

@@ -280,7 +280,7 @@ class API(base.Base):
         return self.db.instance_update(context, instance_id, kwargs)
 
     def delete(self, context, instance_id):
-        LOG.debug(_("Going to try and terminate %s"), instance_id)
+        LOG.debug(_("Going to try to terminate %s"), instance_id)
         try:
             instance = self.get(context, instance_id)
         except exception.NotFound as e:
@@ -301,10 +301,8 @@ class API(base.Base):
 
         host = instance['host']
         if host:
-            rpc.cast(context,
+            self._cast_compute_message('terminate_instance', context,
-                     self.db.queue_get_for(context, FLAGS.compute_topic, host),
+                    instance_id, host)
-                     {"method": "terminate_instance",
-                      "args": {"instance_id": instance_id}})
         else:
             self.db.instance_destroy(context, instance_id)
 
@@ -332,50 +330,34 @@ class API(base.Base):
             project_id)
         return self.db.instance_get_all(context)
 
+    def _cast_compute_message(self, method, context, instance_id, host=None):
+        """Generic handler for RPC calls to compute."""
+        if not host:
+            instance = self.get(context, instance_id)
+            host = instance['host']
+        queue = self.db.queue_get_for(context, FLAGS.compute_topic, host)
+        kwargs = {'method': method, 'args': {'instance_id': instance_id}}
+        rpc.cast(context, queue, kwargs)
+
     def snapshot(self, context, instance_id, name):
         """Snapshot the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('snapshot_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "snapshot_instance",
-                  "args": {"instance_id": instance_id, "name": name}})
 
     def reboot(self, context, instance_id):
         """Reboot the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('reboot_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "reboot_instance",
-                  "args": {"instance_id": instance_id}})
 
     def pause(self, context, instance_id):
         """Pause the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('pause_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "pause_instance",
-                  "args": {"instance_id": instance_id}})
 
     def unpause(self, context, instance_id):
         """Unpause the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('unpause_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "unpause_instance",
-                  "args": {"instance_id": instance_id}})
 
     def get_diagnostics(self, context, instance_id):
         """Retrieve diagnostics for the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('get_diagnostics', context, instance_id)
-        host = instance["host"]
-        return rpc.call(context,
-            self.db.queue_get_for(context, FLAGS.compute_topic, host),
-            {"method": "get_diagnostics",
-             "args": {"instance_id": instance_id}})
 
     def get_actions(self, context, instance_id):
         """Retrieve actions for the given instance."""
@@ -383,39 +365,23 @@ class API(base.Base):
 
     def suspend(self, context, instance_id):
         """suspend the instance with instance_id"""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('suspend_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "suspend_instance",
-                  "args": {"instance_id": instance_id}})
 
     def resume(self, context, instance_id):
         """resume the instance with instance_id"""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('resume_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "resume_instance",
-                  "args": {"instance_id": instance_id}})
 
     def rescue(self, context, instance_id):
         """Rescue the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('rescue_instance', context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "rescue_instance",
-                  "args": {"instance_id": instance_id}})
 
     def unrescue(self, context, instance_id):
         """Unrescue the given instance."""
-        instance = self.get(context, instance_id)
+        self._cast_compute_message('unrescue_instance', context, instance_id)
-        host = instance['host']
+
-        rpc.cast(context,
+    def set_admin_password(self, context, instance_id):
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
+        """Set the root/admin password for the given instance."""
-                 {"method": "unrescue_instance",
+        self._cast_compute_message('set_admin_password', context, instance_id)
-                  "args": {"instance_id": instance['id']}})
 
     def get_ajax_console(self, context, instance_id):
         """Get a url to an AJAX Console"""
@@ -437,35 +403,16 @@ class API(base.Base):
                 output['token'])}
 
     def lock(self, context, instance_id):
-        """
+        """lock the instance with instance_id"""
-        lock the instance with instance_id
+        self._cast_compute_message('lock_instance', context, instance_id)
-
-        """
-        instance = self.get_instance(context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "lock_instance",
-                  "args": {"instance_id": instance['id']}})
 
     def unlock(self, context, instance_id):
-        """
+        """unlock the instance with instance_id"""
-        unlock the instance with instance_id
+        self._cast_compute_message('unlock_instance', context, instance_id)
-
-        """
-        instance = self.get_instance(context, instance_id)
-        host = instance['host']
-        rpc.cast(context,
-                 self.db.queue_get_for(context, FLAGS.compute_topic, host),
-                 {"method": "unlock_instance",
-                  "args": {"instance_id": instance['id']}})
 
     def get_lock(self, context, instance_id):
-        """
+        """return the boolean state of (instance with instance_id)'s lock"""
-        return the boolean state of (instance with instance_id)'s lock
+        instance = self.get(context, instance_id)
-
-        """
-        instance = self.get_instance(context, instance_id)
         return instance['locked']
 
     def attach_volume(self, context, instance_id, volume_id, device):

nova/compute/manager.py

@@ -35,6 +35,8 @@ terminating it.
 """
 
 import datetime
+import random
+import string
 import logging
 import socket
 import functools
@@ -54,6 +56,8 @@ flags.DEFINE_string('compute_driver', 'nova.virt.connection.get_connection',
                     'Driver to use for controlling virtualization')
 flags.DEFINE_string('stub_network', False,
                     'Stub network related code')
+flags.DEFINE_integer('password_length', 12,
+                    'Length of generated admin passwords')
 flags.DEFINE_string('console_host', socket.gethostname(),
                     'Console proxy host to use to connect to instances on'
                     'this host.')
@@ -309,6 +313,35 @@ class ComputeManager(manager.Manager):
 
         self.driver.snapshot(instance_ref, name)
 
+    @exception.wrap_exception
+    @checks_instance_lock
+    def set_admin_password(self, context, instance_id, new_pass=None):
+        """Set the root/admin password for an instance on this server."""
+        context = context.elevated()
+        instance_ref = self.db.instance_get(context, instance_id)
+        if instance_ref['state'] != power_state.RUNNING:
+            logging.warn('trying to reset the password on a non-running '
+                    'instance: %s (state: %s expected: %s)',
+                    instance_ref['id'],
+                    instance_ref['state'],
+                    power_state.RUNNING)
+
+        logging.debug('instance %s: setting admin password',
+                instance_ref['name'])
+        if new_pass is None:
+            # Generate a random password
+            new_pass = self._generate_password(FLAGS.password_length)
+
+        self.driver.set_admin_password(instance_ref, new_pass)
+        self._update_state(context, instance_id)
+
+    def _generate_password(self, length=20):
+        """Generate a random sequence of letters and digits
+        to be used as a password.
+        """
+        chrs = string.letters + string.digits
+        return "".join([random.choice(chrs) for i in xrange(length)])
+
     @exception.wrap_exception
     @checks_instance_lock
     def rescue_instance(self, context, instance_id):

nova/exception.py

@@ -76,6 +76,10 @@ class InvalidInputException(Error):
     pass
 
 
+class TimeoutException(Error):
+    pass
+
+
 def wrap_exception(f):
     def _wrap(*args, **kw):
         try:

nova/tests/test_compute.py

@@ -151,6 +151,13 @@ class ComputeTestCase(test.TestCase):
         self.compute.reboot_instance(self.context, instance_id)
         self.compute.terminate_instance(self.context, instance_id)
 
+    def test_set_admin_password(self):
+        """Ensure instance can have its admin password set"""
+        instance_id = self._create_instance()
+        self.compute.run_instance(self.context, instance_id)
+        self.compute.set_admin_password(self.context, instance_id)
+        self.compute.terminate_instance(self.context, instance_id)
+
     def test_snapshot(self):
         """Ensure instance can be snapshotted"""
         instance_id = self._create_instance()

nova/tests/test_xenapi.py

@@ -31,6 +31,7 @@ from nova.compute import power_state
 from nova.virt import xenapi_conn
 from nova.virt.xenapi import fake as xenapi_fake
 from nova.virt.xenapi import volume_utils
+from nova.virt.xenapi.vmops import SimpleDH
 from nova.tests.db import fakes as db_fakes
 from nova.tests.xenapi import stubs
 
@@ -262,3 +263,29 @@ class XenAPIVMTestCase(test.TestCase):
         instance = db.instance_create(values)
         self.conn.spawn(instance)
         return instance
+
+
+class XenAPIDiffieHellmanTestCase(test.TestCase):
+    """
+    Unit tests for Diffie-Hellman code
+    """
+    def setUp(self):
+        super(XenAPIDiffieHellmanTestCase, self).setUp()
+        self.alice = SimpleDH()
+        self.bob = SimpleDH()
+
+    def test_shared(self):
+        alice_pub = self.alice.get_public()
+        bob_pub = self.bob.get_public()
+        alice_shared = self.alice.compute_shared(bob_pub)
+        bob_shared = self.bob.compute_shared(alice_pub)
+        self.assertEquals(alice_shared, bob_shared)
+
+    def test_encryption(self):
+        msg = "This is a top-secret message"
+        enc = self.alice.encrypt(msg)
+        dec = self.bob.decrypt(enc)
+        self.assertEquals(dec, msg)
+
+    def tearDown(self):
+        super(XenAPIDiffieHellmanTestCase, self).tearDown()

nova/virt/fake.py

@@ -98,7 +98,7 @@ class FakeConnection(object):
         the new instance.
 
         The work will be done asynchronously.  This function returns a
-        Deferred that allows the caller to detect when it is complete.
+        task that allows the caller to detect when it is complete.
 
         Once this successfully completes, the instance should be
         running (power_state.RUNNING).
@@ -122,7 +122,7 @@ class FakeConnection(object):
         The second parameter is the name of the snapshot.
 
         The work will be done asynchronously.  This function returns a
-        Deferred that allows the caller to detect when it is complete.
+        task that allows the caller to detect when it is complete.
         """
         pass
 
@@ -134,7 +134,20 @@ class FakeConnection(object):
         and so the instance is being specified as instance.name.
 
         The work will be done asynchronously.  This function returns a
-        Deferred that allows the caller to detect when it is complete.
+        task that allows the caller to detect when it is complete.
+        """
+        pass
+
+    def set_admin_password(self, instance, new_pass):
+        """
+        Set the root password on the specified instance.
+
+        The first parameter is an instance of nova.compute.service.Instance,
+        and so the instance is being specified as instance.name. The second
+        parameter is the value of the new password.
+
+        The work will be done asynchronously.  This function returns a
+        task that allows the caller to detect when it is complete.
         """
         pass
 
@@ -182,7 +195,7 @@ class FakeConnection(object):
         and so the instance is being specified as instance.name.
 
         The work will be done asynchronously.  This function returns a
-        Deferred that allows the caller to detect when it is complete.
+        task that allows the caller to detect when it is complete.
         """
         del self.instances[instance.name]
 

nova/virt/xenapi/vmops.py

@@ -20,6 +20,11 @@ Management class for VM-related functions (spawn, reboot, etc).
 """
 
 import json
+import M2Crypto
+import os
+import subprocess
+import tempfile
+import uuid
 
 from nova import db
 from nova import context
@@ -127,12 +132,31 @@ class VMOps(object):
         """Refactored out the common code of many methods that receive either
         a vm name or a vm instance, and want a vm instance in return.
         """
+        vm = None
         try:
-            instance_name = instance_or_vm.name
+            if instance_or_vm.startswith("OpaqueRef:"):
-            vm = VMHelper.lookup(self._session, instance_name)
+                # Got passed an opaque ref; return it
-        except AttributeError:
+                return instance_or_vm
-            # A vm opaque ref was passed
+            else:
-            vm = instance_or_vm
+                # Must be the instance name
+                instance_name = instance_or_vm
+        except (AttributeError, KeyError):
+            # Note the the KeyError will only happen with fakes.py
+            # Not a string; must be an ID or a vm instance
+            if isinstance(instance_or_vm, (int, long)):
+                ctx = context.get_admin_context()
+                try:
+                    instance_obj = db.instance_get_by_id(ctx, instance_or_vm)
+                    instance_name = instance_obj.name
+                except exception.NotFound:
+                    # The unit tests screw this up, as they use an integer for
+                    # the vm name. I'd fix that up, but that's a matter for
+                    # another bug report. So for now, just try with the passed
+                    # value
+                    instance_name = instance_or_vm
+            else:
+                instance_name = instance_or_vm.name
+        vm = VMHelper.lookup(self._session, instance_name)
         if vm is None:
             raise Exception(_('Instance not present %s') % instance_name)
         return vm
@@ -189,6 +213,44 @@ class VMOps(object):
         task = self._session.call_xenapi('Async.VM.clean_reboot', vm)
         self._session.wait_for_task(instance.id, task)
 
+    def set_admin_password(self, instance, new_pass):
+        """Set the root/admin password on the VM instance. This is done via
+        an agent running on the VM. Communication between nova and the agent
+        is done via writing xenstore records. Since communication is done over
+        the XenAPI RPC calls, we need to encrypt the password. We're using a
+        simple Diffie-Hellman class instead of the more advanced one in
+        M2Crypto for compatibility with the agent code.
+        """
+        # Need to uniquely identify this request.
+        transaction_id = str(uuid.uuid4())
+        # The simple Diffie-Hellman class is used to manage key exchange.
+        dh = SimpleDH()
+        args = {'id': transaction_id, 'pub': str(dh.get_public())}
+        resp = self._make_agent_call('key_init', instance, '', args)
+        if resp is None:
+            # No response from the agent
+            return
+        resp_dict = json.loads(resp)
+        # Successful return code from key_init is 'D0'
+        if resp_dict['returncode'] != 'D0':
+            # There was some sort of error; the message will contain
+            # a description of the error.
+            raise RuntimeError(resp_dict['message'])
+        agent_pub = int(resp_dict['message'])
+        dh.compute_shared(agent_pub)
+        enc_pass = dh.encrypt(new_pass)
+        # Send the encrypted password
+        args['enc_pass'] = enc_pass
+        resp = self._make_agent_call('password', instance, '', args)
+        if resp is None:
+            # No response from the agent
+            return
+        resp_dict = json.loads(resp)
+        # Successful return code from password is '0'
+        if resp_dict['returncode'] != '0':
+            raise RuntimeError(resp_dict['message'])
+        return resp_dict['message']
+
     def destroy(self, instance):
         """Destroy VM instance"""
         vm = VMHelper.lookup(self._session, instance.name)
@@ -246,30 +308,19 @@ class VMOps(object):
 
     def suspend(self, instance, callback):
         """suspend the specified instance"""
-        instance_name = instance.name
+        vm = self._get_vm_opaque_ref(instance)
-        vm = VMHelper.lookup(self._session, instance_name)
-        if vm is None:
-            raise Exception(_("suspend: instance not present %s") %
-                                                     instance_name)
         task = self._session.call_xenapi('Async.VM.suspend', vm)
         self._wait_with_callback(instance.id, task, callback)
 
     def resume(self, instance, callback):
         """resume the specified instance"""
-        instance_name = instance.name
+        vm = self._get_vm_opaque_ref(instance)
-        vm = VMHelper.lookup(self._session, instance_name)
-        if vm is None:
-            raise Exception(_("resume: instance not present %s") %
-                                                    instance_name)
         task = self._session.call_xenapi('Async.VM.resume', vm, False, True)
         self._wait_with_callback(instance.id, task, callback)
 
-    def get_info(self, instance_id):
+    def get_info(self, instance):
         """Return data about VM instance"""
-        vm = VMHelper.lookup(self._session, instance_id)
+        vm = self._get_vm_opaque_ref(instance)
-        if vm is None:
-            raise exception.NotFound(_('Instance not'
-                                       ' found %s') % instance_id)
         rec = self._session.get_xenapi().VM.get_record(vm)
         return VMHelper.compile_info(rec)
 
@@ -333,22 +384,34 @@ class VMOps(object):
         return self._make_plugin_call('xenstore.py', method=method, vm=vm,
                 path=path, addl_args=addl_args)
 
+    def _make_agent_call(self, method, vm, path, addl_args={}):
+        """Abstracts out the interaction with the agent xenapi plugin."""
+        return self._make_plugin_call('agent', method=method, vm=vm,
+                path=path, addl_args=addl_args)
+
     def _make_plugin_call(self, plugin, method, vm, path, addl_args={}):
         """Abstracts out the process of calling a method of a xenapi plugin.
         Any errors raised by the plugin will in turn raise a RuntimeError here.
         """
+        instance_id = vm.id
         vm = self._get_vm_opaque_ref(vm)
         rec = self._session.get_xenapi().VM.get_record(vm)
         args = {'dom_id': rec['domid'], 'path': path}
         args.update(addl_args)
-        # If the 'testing_mode' attribute is set, add that to the args.
-        if getattr(self, 'testing_mode', False):
-            args['testing_mode'] = 'true'
         try:
             task = self._session.async_call_plugin(plugin, method, args)
-            ret = self._session.wait_for_task(0, task)
+            ret = self._session.wait_for_task(instance_id, task)
         except self.XenAPI.Failure, e:
-            raise RuntimeError("%s" % e.details[-1])
+            ret = None
+            err_trace = e.details[-1]
+            err_msg = err_trace.splitlines()[-1]
+            strargs = str(args)
+            if 'TIMEOUT:' in err_msg:
+                LOG.error(_('TIMEOUT: The call to %(method)s timed out. '
+                        'VM id=%(instance_id)s; args=%(strargs)s') % locals())
+            else:
+                LOG.error(_('The call to %(method)s returned an error: %(e)s. '
+                        'VM id=%(instance_id)s; args=%(strargs)s') % locals())
         return ret
 
     def add_to_xenstore(self, vm, path, key, value):
@@ -460,3 +523,89 @@ class VMOps(object):
         """Removes all data from the xenstore parameter record for this VM."""
         self.write_to_param_xenstore(instance_or_vm, {})
     ########################################################################
+
+
+def _runproc(cmd):
+    pipe = subprocess.PIPE
+    return subprocess.Popen([cmd], shell=True, stdin=pipe, stdout=pipe,
+            stderr=pipe, close_fds=True)
+
+
+class SimpleDH(object):
+    """This class wraps all the functionality needed to implement
+    basic Diffie-Hellman-Merkle key exchange in Python. It features
+    intelligent defaults for the prime and base numbers needed for the
+    calculation, while allowing you to supply your own. It requires that
+    the openssl binary be installed on the system on which this is run,
+    as it uses that to handle the encryption and decryption. If openssl
+    is not available, a RuntimeError will be raised.
+    """
+    def __init__(self, prime=None, base=None, secret=None):
+        """You can specify the values for prime and base if you wish;
+        otherwise, reasonable default values will be used.
+        """
+        if prime is None:
+            self._prime = 162259276829213363391578010288127
+        else:
+            self._prime = prime
+        if base is None:
+            self._base = 5
+        else:
+            self._base = base
+        self._shared = self._public = None
+
+        self._dh = M2Crypto.DH.set_params(
+                self.dec_to_mpi(self._prime),
+                self.dec_to_mpi(self._base))
+        self._dh.gen_key()
+        self._public = self.mpi_to_dec(self._dh.pub)
+
+    def get_public(self):
+        return self._public
+
+    def compute_shared(self, other):
+        self._shared = self.bin_to_dec(
+                self._dh.compute_key(self.dec_to_mpi(other)))
+        return self._shared
+
+    def mpi_to_dec(self, mpi):
+        bn = M2Crypto.m2.mpi_to_bn(mpi)
+        hexval = M2Crypto.m2.bn_to_hex(bn)
+        dec = int(hexval, 16)
+        return dec
+
+    def bin_to_dec(self, binval):
+        bn = M2Crypto.m2.bin_to_bn(binval)
+        hexval = M2Crypto.m2.bn_to_hex(bn)
+        dec = int(hexval, 16)
+        return dec
+
+    def dec_to_mpi(self, dec):
+        bn = M2Crypto.m2.dec_to_bn('%s' % dec)
+        mpi = M2Crypto.m2.bn_to_mpi(bn)
+        return mpi
+
+    def _run_ssl(self, text, which):
+        base_cmd = ('cat %(tmpfile)s | openssl enc -aes-128-cbc '
+                '-a -pass pass:%(shared)s -nosalt %(dec_flag)s')
+        if which.lower()[0] == 'd':
+            dec_flag = ' -d'
+        else:
+            dec_flag = ''
+        fd, tmpfile = tempfile.mkstemp()
+        os.close(fd)
+        file(tmpfile, 'w').write(text)
+        shared = self._shared
+        cmd = base_cmd % locals()
+        proc = _runproc(cmd)
+        proc.wait()
+        err = proc.stderr.read()
+        if err:
+            raise RuntimeError(_('OpenSSL error: %s') % err)
+        return proc.stdout.read()
+
+    def encrypt(self, text):
+        return self._run_ssl(text, 'enc')
+
+    def decrypt(self, text):
+        return self._run_ssl(text, 'dec')

nova/virt/xenapi_conn.py

@@ -149,6 +149,10 @@ class XenAPIConnection(object):
         """Reboot VM instance"""
         self._vmops.reboot(instance)
 
+    def set_admin_password(self, instance, new_pass):
+        """Set the root/admin password on the VM instance"""
+        self._vmops.set_admin_password(instance, new_pass)
+
     def destroy(self, instance):
         """Destroy VM instance"""
         self._vmops.destroy(instance)
@@ -266,7 +270,8 @@ class XenAPISession(object):
 
     def _poll_task(self, id, task, done):
         """Poll the given XenAPI task, and fire the given action if we
-        get a result."""
+        get a result.
+        """
         try:
             name = self._session.xenapi.task.get_name_label(task)
             status = self._session.xenapi.task.get_status(task)

plugins/xenserver/xenapi/etc/xapi.d/plugins/agent

@@ -0,0 +1,126 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2011 Citrix Systems, Inc.
+# Copyright 2011 OpenStack LLC.
+# Copyright 2011 United States Government as represented by the
+# Administrator of the National Aeronautics and Space Administration.
+# 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.
+
+#
+# XenAPI plugin for reading/writing information to xenstore
+#
+
+try:
+    import json
+except ImportError:
+    import simplejson as json
+import os
+import random
+import subprocess
+import tempfile
+import time
+
+import XenAPIPlugin
+
+from pluginlib_nova import *
+configure_logging("xenstore")
+import xenstore
+
+AGENT_TIMEOUT = 30
+
+
+def jsonify(fnc):
+    def wrapper(*args, **kwargs):
+        return json.dumps(fnc(*args, **kwargs))
+    return wrapper
+
+
+class TimeoutError(StandardError):
+    pass
+
+
+@jsonify
+def key_init(self, arg_dict):
+    """Handles the Diffie-Hellman key exchange with the agent to
+    establish the shared secret key used to encrypt/decrypt sensitive
+    info to be passed, such as passwords. Returns the shared
+    secret key value.
+    """
+    pub = int(arg_dict["pub"])
+    arg_dict["value"] = json.dumps({"name": "keyinit", "value": pub})
+    request_id = arg_dict["id"]
+    arg_dict["path"] = "data/host/%s" % request_id
+    xenstore.write_record(self, arg_dict)
+    try:
+        resp = _wait_for_agent(self, request_id, arg_dict)
+    except TimeoutError, e:
+        raise PluginError("%s" % e)
+    return resp
+
+
+@jsonify
+def password(self, arg_dict):
+    """Writes a request to xenstore that tells the agent to set
+    the root password for the given VM. The password should be 
+    encrypted using the shared secret key that was returned by a 
+    previous call to key_init. The encrypted password value should
+    be passed as the value for the 'enc_pass' key in arg_dict.
+    """
+    pub = int(arg_dict["pub"])
+    enc_pass = arg_dict["enc_pass"]
+    arg_dict["value"] = json.dumps({"name": "password", "value": enc_pass})
+    request_id = arg_dict["id"]
+    arg_dict["path"] = "data/host/%s" % request_id
+    xenstore.write_record(self, arg_dict)
+    try:
+        resp = _wait_for_agent(self, request_id, arg_dict)
+    except TimeoutError, e:
+        raise PluginError("%s" % e)
+    return resp
+
+
+def _wait_for_agent(self, request_id, arg_dict):
+    """Periodically checks xenstore for a response from the agent.
+    The request is always written to 'data/host/{id}', and
+    the agent's response for that request will be in 'data/guest/{id}'.
+    If no value appears from the agent within the time specified by
+    AGENT_TIMEOUT, the original request is deleted and a TimeoutError
+    is returned.
+    """
+    arg_dict["path"] = "data/guest/%s" % request_id
+    arg_dict["ignore_missing_path"] = True
+    start = time.time()
+    while True:
+        if time.time() - start > AGENT_TIMEOUT:
+            # No response within the timeout period; bail out
+            # First, delete the request record
+            arg_dict["path"] = "data/host/%s" % request_id
+            xenstore.delete_record(self, arg_dict)
+            raise TimeoutError("TIMEOUT: No response from agent within %s seconds." %
+                    AGENT_TIMEOUT)
+        ret = xenstore.read_record(self, arg_dict)
+        # Note: the response for None with be a string that includes
+        # double quotes.
+        if ret != '"None"':
+            # The agent responded
+            return ret
+        else:
+            time.sleep(3)
+
+
+if __name__ == "__main__":
+    XenAPIPlugin.dispatch(
+        {"key_init": key_init,
+        "password": password})