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Implement privsep boilerplate in cinder.

This includes implementing a first trivial example of how to use
privsep to run something as root, specifically the cgroup throttling
driver.

This code is modelled strongly on how nova has chosen to use privsep.
Consistency is probably good here, but it does imply that the cinder
team is ok with the decisons nova has made about implementation.

Change-Id: Ic401138a10a72cb4b976a1a6aba272cafcb40d8b
changes/79/566479/4
Michael Still 3 years ago
committed by TommyLike
parent
commit
861646d1ba
  1. 32
      cinder/privsep/__init__.py
  2. 35
      cinder/privsep/cgroup.py
  3. 3
      cinder/test.py
  4. 29
      cinder/tests/fixtures.py
  5. 53
      cinder/tests/unit/test_volume_throttling.py
  6. 7
      cinder/volume/throttling.py
  7. 6
      etc/cinder/rootwrap.d/volume.filters
  8. 14
      releasenotes/notes/privsep-rocky-35bdfe70ed62a826.yaml

32
cinder/privsep/__init__.py

@ -0,0 +1,32 @@
# Copyright 2016 Red Hat, Inc
# Copyright 2017 Rackspace Australia
# Copyright 2018 Michael Still and Aptira
#
# 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.
"""Setup privsep decorator."""
from oslo_privsep import capabilities
from oslo_privsep import priv_context
sys_admin_pctxt = priv_context.PrivContext(
'cinder',
cfg_section='cinder_sys_admin',
pypath=__name__ + '.sys_admin_pctxt',
capabilities=[capabilities.CAP_CHOWN,
capabilities.CAP_DAC_OVERRIDE,
capabilities.CAP_DAC_READ_SEARCH,
capabilities.CAP_FOWNER,
capabilities.CAP_NET_ADMIN,
capabilities.CAP_SYS_ADMIN],
)

35
cinder/privsep/cgroup.py

@ -0,0 +1,35 @@
# Copyright 2016 Red Hat, Inc
# Copyright 2017 Rackspace Australia
# Copyright 2018 Michael Still and Aptira
#
# 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.
"""
Helpers for cgroup related routines.
"""
from oslo_concurrency import processutils
import cinder.privsep
@cinder.privsep.sys_admin_pctxt.entrypoint
def cgroup_create(name):
processutils.execute('cgcreate', '-g', 'blkio:%s' % name)
@cinder.privsep.sys_admin_pctxt.entrypoint
def cgroup_limit(name, rw, dev, bps):
processutils.execute('cgset', '-r',
'blkio.throttle.%s_bps_device=%s %d' % (rw, dev, bps),
name)

3
cinder/test.py

@ -302,6 +302,9 @@ class TestCase(testtools.TestCase):
tpool.killall()
tpool._nthreads = 20
# NOTE(mikal): make sure we don't load a privsep helper accidentally
self.useFixture(cinder_fixtures.PrivsepNoHelperFixture())
def _restore_obj_registry(self):
objects_base.CinderObjectRegistry._registry._obj_classes = \
self._base_test_obj_backup

29
cinder/tests/fixtures.py

@ -1,4 +1,6 @@
# Copyright 2016 IBM Corp.
# Copyright 2017 Rackspace Australia
# Copyright 2018 Michael Still and Aptira
#
# 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
@ -21,6 +23,7 @@ import os
import warnings
import fixtures
from oslo_privsep import daemon as privsep_daemon
_TRUE_VALUES = ('True', 'true', '1', 'yes')
@ -131,3 +134,29 @@ class WarningsFixture(fixtures.Fixture):
' This key is deprecated. Please update your policy '
'file to use the standard policy values.')
self.addCleanup(warnings.resetwarnings)
class UnHelperfulClientChannel(privsep_daemon._ClientChannel):
def __init__(self, context):
raise Exception('You have attempted to start a privsep helper. '
'This is not allowed in the gate, and '
'indicates a failure to have mocked your tests.')
class PrivsepNoHelperFixture(fixtures.Fixture):
"""A fixture to catch failures to mock privsep's rootwrap helper.
If you fail to mock away a privsep'd method in a unit test, then
you may well end up accidentally running the privsep rootwrap
helper. This will fail in the gate, but it fails in a way which
doesn't identify which test is missing a mock. Instead, we
raise an exception so that you at least know where you've missed
something.
"""
def setUp(self):
super(PrivsepNoHelperFixture, self).setUp()
self.useFixture(fixtures.MonkeyPatch(
'oslo_privsep.daemon.RootwrapClientChannel',
UnHelperfulClientChannel))

53
cinder/tests/unit/test_volume_throttling.py

@ -29,7 +29,9 @@ class ThrottleTestCase(test.TestCase):
self.assertEqual([], cmd['prefix'])
@mock.patch.object(utils, 'get_blkdev_major_minor')
def test_BlkioCgroup(self, mock_major_minor):
@mock.patch('cinder.privsep.cgroup.cgroup_create')
@mock.patch('cinder.privsep.cgroup.cgroup_limit')
def test_BlkioCgroup(self, mock_limit, mock_create, mock_major_minor):
def fake_get_blkdev_major_minor(path):
return {'src_volume1': "253:0", 'dst_volume1': "253:1",
@ -37,38 +39,25 @@ class ThrottleTestCase(test.TestCase):
mock_major_minor.side_effect = fake_get_blkdev_major_minor
self.exec_cnt = 0
throttle = throttling.BlkioCgroup(1024, 'fake_group')
with throttle.subcommand('src_volume1', 'dst_volume1') as cmd:
self.assertEqual(['cgexec', '-g', 'blkio:fake_group'],
cmd['prefix'])
def fake_execute(*cmd, **kwargs):
cmd_set = ['cgset', '-r',
'blkio.throttle.%s_bps_device=%s %d', 'fake_group']
set_order = [None,
('read', '253:0', 1024),
('write', '253:1', 1024),
# a nested job starts; bps limit are set to the half
('read', '253:0', 512),
('read', '253:2', 512),
('write', '253:1', 512),
('write', '253:3', 512),
# a nested job ends; bps limit is resumed
('read', '253:0', 1024),
('write', '253:1', 1024)]
if set_order[self.exec_cnt] is None:
self.assertEqual(('cgcreate', '-g', 'blkio:fake_group'), cmd)
else:
cmd_set[2] %= set_order[self.exec_cnt]
self.assertEqual(tuple(cmd_set), cmd)
self.exec_cnt += 1
with mock.patch.object(utils, 'execute', side_effect=fake_execute):
throttle = throttling.BlkioCgroup(1024, 'fake_group')
with throttle.subcommand('src_volume1', 'dst_volume1') as cmd:
# a nested job
with throttle.subcommand('src_volume2', 'dst_volume2') as cmd:
self.assertEqual(['cgexec', '-g', 'blkio:fake_group'],
cmd['prefix'])
# a nested job
with throttle.subcommand('src_volume2', 'dst_volume2') as cmd:
self.assertEqual(['cgexec', '-g', 'blkio:fake_group'],
cmd['prefix'])
mock_create.assert_has_calls([mock.call('fake_group')])
mock_limit.assert_has_calls([
mock.call('fake_group', 'read', '253:0', 1024),
mock.call('fake_group', 'write', '253:1', 1024),
# a nested job starts; bps limit are set to the half
mock.call('fake_group', 'read', '253:0', 512),
mock.call('fake_group', 'read', '253:2', 512),
mock.call('fake_group', 'write', '253:1', 512),
mock.call('fake_group', 'write', '253:3', 512),
# a nested job ends; bps limit is resumed
mock.call('fake_group', 'read', '253:0', 1024),
mock.call('fake_group', 'write', '253:1', 1024)])

7
cinder/volume/throttling.py

@ -22,6 +22,7 @@ from oslo_concurrency import processutils
from oslo_log import log as logging
from cinder import exception
import cinder.privsep.cgroup
from cinder import utils
@ -65,8 +66,7 @@ class BlkioCgroup(Throttle):
self.dstdevs = {}
try:
utils.execute('cgcreate', '-g', 'blkio:%s' % self.cgroup,
run_as_root=True)
cinder.privsep.cgroup.cgroup_create(self.cgroup)
except processutils.ProcessExecutionError:
LOG.error('Failed to create blkio cgroup \'%(name)s\'.',
{'name': cgroup_name})
@ -81,8 +81,7 @@ class BlkioCgroup(Throttle):
def _limit_bps(self, rw, dev, bps):
try:
utils.execute('cgset', '-r', 'blkio.throttle.%s_bps_device=%s %d'
% (rw, dev, bps), self.cgroup, run_as_root=True)
cinder.privsep.cgroup.cgroup_limit(self.cgroup, rw, dev, bps)
except processutils.ProcessExecutionError:
LOG.warning('Failed to setup blkio cgroup to throttle the '
'device \'%(device)s\'.', {'device': dev})

6
etc/cinder/rootwrap.d/volume.filters

@ -43,6 +43,10 @@ lvdisplay4: EnvFilter, env, root, LC_ALL=C, LVM_SYSTEM_DIR=, LVM_SUPPRESS_FD_WAR
# This line ties the superuser privs with the config files, context name,
# and (implicitly) the actual python code invoked.
privsep-rootwrap: RegExpFilter, privsep-helper, root, privsep-helper, --config-file, /etc/(?!\.\.).*, --privsep_context, os_brick.privileged.default, --privsep_sock_path, /tmp/.*
# Privsep calls within cinder iteself
privsep-rootwrap-sys_admin: RegExpFilter, privsep-helper, root, privsep-helper, --config-file, /etc/(?!\.\.).*, --privsep_context, cinder.privsep.sys_admin_pctxt, --privsep_sock_path, /tmp/.*
# The following and any cinder/brick/* entries should all be obsoleted
# by privsep, and may be removed once the os-brick version requirement
# is updated appropriately.
@ -93,8 +97,6 @@ ionice_1: ChainingRegExpFilter, ionice, root, ionice, -c[0-3], -n[0-7]
ionice_2: ChainingRegExpFilter, ionice, root, ionice, -c[0-3]
# cinder/volume/utils.py: setup_blkio_cgroup()
cgcreate: CommandFilter, cgcreate, root
cgset: CommandFilter, cgset, root
cgexec: ChainingRegExpFilter, cgexec, root, cgexec, -g, blkio:\S+
# cinder/volume/driver.py

14
releasenotes/notes/privsep-rocky-35bdfe70ed62a826.yaml

@ -0,0 +1,14 @@
---
security:
- |
Privsep transitions. Cinder is transitioning from using the older style
rootwrap privilege escalation path to the new style Oslo privsep path.
This should improve performance and security of Cinder in the long term.
- |
Privsep daemons are now started by Cinder when required. These daemons can
be started via rootwrap if required. rootwrap configs therefore need to
be updated to include new privsep daemon invocations.
upgrade:
- |
The following commands are no longer required to be listed in your rootwrap
configuration: cgcreate; and cgset.
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