dbf77fba10
This change replaces all uses of rootwrap with a trivial privsep-based equivalent. This replacement simply executes commands as the privsep user *without any additional checks*. There are 2 reasons why this is a reasonable thing to do: 1. We don't have a good workflow for merging rootwrap filter changes into parent projects (nova/cinder) for a loosely-coupled library like os-brick. 2. The previous situation was also insecure. The os-brick.filters rootwrap config permitted commands like "dd" and "cp" with any arguments, as root. This would have posed only a mild inconvenience to an attacker. With privsep we can at least (in principle) limit the commands to the privsep uid/gid and Linux capabilities (CAP_SYS_ADMIN by default with this change). This change addresses the urgency of (1). Later refactors will take greater advantage of privsep to address (2). Change-Id: I0af542eba97d2f89b1c283bf1e1e985d9690f5de Depends-On: I90dc41bc77993bd83b80c92286e015e14f290b45 # nova: nova.conf: Set privsep_rootwrap.helper_command Depends-On: I4e333e73ddfd45c045b9d32dac1506fc25858c4d # nova: Add os-brick rootwrap filter for privsep Depends-On: I8a0b1728cc66c4861f69623b1b16b1f759b57b25 # cinder: cinder.conf: Set privsep_rootwrap.helper_command Depends-On: I3b2e337321875cf4abc0ab9b44fe17cf9327d88b # cinder: Add os-brick rootwrap filter for privsep Depends-On: I4299c2fc059807610f83e12a2d470e020930c64c # privsep: Switch to msgpack for serialization Depends-On: Ied1ef4fc945e18516b39d1f20d58425cb633dc74 # requirements: require oslo.privsep>=1.5.0 for msgpack fix
83 lines
3.1 KiB
Python
83 lines
3.1 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Just in case it wasn't clear, this is a massive security back-door.
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`execute_root()` (or the same via `execute(run_as_root=True)`) allows
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any command to be run as the privileged user (default "root"). This
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is intended only as an expedient transition and should be removed
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ASAP.
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This is not completely unreasonable because:
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1. We have no tool/workflow for merging changes to rootwrap filter
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configs from os-brick into nova/cinder, which makes it difficult
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to evolve these loosely coupled projects.
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2. Let's not pretend the earlier situation was any better. The
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rootwrap filters config contained several entries like "allow cp as
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root with any arguments", etc, and would have posed only a mild
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inconvenience to an attacker. At least with privsep we can (in
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principle) run the "root" commands as a non-root uid, with
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restricted Linux capabilities.
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The plan is to switch os-brick to privsep using this module (removing
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the urgency of (1)), then work on the larger refactor that addresses
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(2) in followup changes.
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"""
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import six
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from oslo_concurrency import processutils as putils
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from oslo_utils import strutils
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from os_brick import privileged
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# Entrypoint used for rootwrap.py transition code. Don't use this for
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# other purposes, since it will be removed when we think the
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# transition is finished.
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def execute(*cmd, **kwargs):
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"""NB: Raises processutils.ProcessExecutionError on failure."""
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run_as_root = kwargs.pop('run_as_root', False)
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kwargs.pop('root_helper', None)
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try:
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if run_as_root:
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return execute_root(*cmd, **kwargs)
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else:
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return putils.execute(*cmd, **kwargs)
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except OSError as e:
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# Note:
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# putils.execute('bogus', run_as_root=True)
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# raises ProcessExecutionError(exit_code=1) (because there's a
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# "sh -c bogus" involved in there somewhere, but:
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# putils.execute('bogus', run_as_root=False)
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# raises OSError(not found).
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#
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# Lots of code in os-brick catches only ProcessExecutionError
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# and never encountered the latter when using rootwrap.
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# Rather than fix all the callers, we just always raise
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# ProcessExecutionError here :(
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sanitized_cmd = strutils.mask_password(' '.join(cmd))
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raise putils.ProcessExecutionError(
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cmd=sanitized_cmd, description=six.text_type(e))
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# See comment on `execute`
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@privileged.default.entrypoint
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def execute_root(*cmd, **kwargs):
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"""NB: Raises processutils.ProcessExecutionError/OSError on failure."""
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return putils.execute(*cmd, shell=False, run_as_root=False, **kwargs)
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