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# Copyright (C) 2016 Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <http://www.gnu.org/licenses/>.
'''Execute command in a sandbox, using 'bubblewrap'.
This implements an API defined in sandboxlib/__init__.py.
'''
import os
import logging
import sandboxlib
#FIXME copied over from `linux_user_chroot`, not sure on what is expected here.
CAPABILITIES = {
'network': ['isolated', 'undefined'],
'mounts': ['isolated', 'undefined'],
'filesystem_writable_paths': ['all', 'any'],
}
def degrade_config_for_capabilities(in_config, warn=True):
# This backend has the most features, right now!
return in_config
def run_sandbox(command, cwd=None, env=None,
filesystem_root='/', filesystem_writable_paths='all',
mounts='undefined', extra_mounts=None,
network='undefined',
stderr=sandboxlib.CAPTURE, stdout=sandboxlib.CAPTURE):
'''Run 'command' in a sandboxed environment.
Parameters:
- command: the command to run. Pass a list of parameters rather than
using spaces to separate them, e.g. ['echo', '"Hello world"'].
- cwd: the working directory of 'command', relative to 'rootfs_path'.
Defaults to '/' if "rootfs_path" is specified, and the current
directory of the calling process otherwise.
- env: environment variables to set
- filesystem_root: the path to the root of the sandbox. Defaults to '/',
which doesn't isolate the command from the host filesystem at all.
- filesystem_writable_paths: defaults to 'all', which allows the command
to write to anywhere under 'filesystem_root' that the user of the
calling process could write to. Backends may accept a list of paths
instead of 'all', and will prevent writes to any files not under a
path in that whitelist. If 'none' or an empty list is passed, the
whole file-system will be read-only. The paths should be relative
to filesystem_root. This will processed /after/ extra_mounts are
mounted.
- mounts: configures mount sharing. Defaults to 'undefined', where no
no attempt is made to isolate mounts. Backends may support
'isolated' as well.
- extra_mounts: a list of locations to mount inside 'rootfs_path',
specified as a list of tuples of (source_path, target_path, type,
options). The 'type' and 'options' should match what would be
specified in /etc/fstab, but a backends may support only a limited
subset of values. The 'target_path' is relative to filesystem_root
and will be created before mounting if it doesn't exist.
- network: configures network sharing. Defaults to 'undefined', where
no attempt is made to either prevent or provide networking
inside the sandbox. Backends may support 'isolated' and/or other
values as well.
- stdout: whether to capture stdout, or redirect stdout to a file handle.
If set to sandboxlib.CAPTURE, the function will return the stdout
data, if not, it will return None for that. If stdout=None, the
data will be discarded -- it will NOT inherit the parent process's
stdout, unlike with subprocess.Popen(). Set 'stdout=sys.stdout' if
you want that.
- stderr: same as stdout
Returns:
a tuple of (exit code, stdout output, stderr output).
'''
log = logging.getLogger("sandboxlib")
log.warn("In sandbox fn, args")
print("cmd: {}, cwd: {}, env: {}, filesystem_root: {}," \
"filesystem_writable_paths: {}, mounts: {}, extra_mounts: {}, "\
"network: {}, stderr: {}, stdout: {}".format(
command, cwd, env, filesystem_root, filesystem_writable_paths,
mounts, extra_mounts, network, stderr, stdout))
if type(command) == str:
command = [command]
#Bwrap full path
bwrap_command = [bubblewrap_program()]
print("bwrap cmd : {}".format(bwrap_command))
# Add in the root filesystem stuff first
bwrap_command += ["--ro-bind", filesystem_root, "/"]
bwrap_command += process_network_config(network)
if cwd is not None:
bwrap_command.extend(['--chdir', cwd])
# do pre checks on mounts
extra_mounts = sandboxlib.validate_extra_mounts(extra_mounts)
create_mount_points_if_missing(filesystem_root, extra_mounts)
#Handles the ro and rw mounts
bwrap_command += process_mounts(filesystem_root, extra_mounts,
filesystem_writable_paths)
argv = bwrap_command + command
print("run_command({}, {}, {}, {})"
.format(argv, stdout, stderr, env))
#run_command(['/usr/bin/bwrap', '--bind', 'a', '--bind', 'l', '--bind', 'l', '/', 'echo', 'xyzzy'], -1, -1, None)
exit, out, err = sandboxlib._run_command(argv, stdout, stderr, env=env)
return exit, out, err
def run_sandbox_with_redirection(command, **sandbox_config):
'''Start a subprocess in a sandbox, redirecting stderr and/or stdout.
The sandbox_config arguments are the same as the run_command() function.
This returns just the exit code, because if stdout or stderr are redirected
those values will be None in any case.
'''
exit, out, err = run_sandbox(command, **sandbox_config)
# out and err will be None
return exit
## Non API methods below
def bubblewrap_program():
# Raises sandboxlib.ProgramNotFound if not found.
return sandboxlib.utils.find_program('bwrap')
def create_mount_points_if_missing(filesystem_root, mount_info_list):
for source, mount_point, mount_type, mount_options in mount_info_list:
# Strip the preceeding '/' from mount_point, because it'll break
# os.path.join().
mount_point_no_slash = os.path.abspath(mount_point).lstrip('/')
path = os.path.join(filesystem_root, mount_point_no_slash)
if not os.path.exists(path):
os.makedirs(path)
def process_network_config(network):
sandboxlib.utils.check_parameter('network', network, CAPABILITIES['network'])
if network == 'isolated':
# This is all we need to do for network isolation
network_args = ['--unshare-net']
else:
network_args = []
return network_args
def process_mounts(fs_root, mounts, writable_paths):
'''
filesystem_writable_paths: defaults to 'all', which allows the command
to write to anywhere under 'filesystem_root' that the user of the
calling process could write to. Backends may accept a list of paths
instead of 'all', and will prevent writes to any files not under a
path in that whitelist. If 'none' or an empty list is passed, the
whole file-system will be read-only. The paths should be relative
to filesystem_root. This will processed /after/ extra_mounts are
mounted.
extra_mounts: a list of locations to mount inside 'rootfs_path',
specified as a list of tuples of (source_path, target_path, type,
options). The 'type' and 'options' should match what would be
specified in /etc/fstab, but a backends may support only a limited
subset of values. The 'target_path' is relative to filesystem_root
and will be created before mounting if it doesn't exist.
'''
extra_args = []
for ex_mnt in mounts:
mnt_src,mnt_target,mnt_type,mnt_options=ex_mnt
print("mnt '{}', '{}', '{}', '{}'".format(mnt_src,mnt_target,mnt_type,mnt_options))
#TODO
# How to handle options? Can bwrap do this?
if mnt_type == "proc":
extra_args.extend(['--proc', mnt_target])
elif mnt_type == "tmpfs":
extra_args.extend(['--tmpfs', mnt_target])
#TODO what type is passed here?
elif mnt_src == "/dev":
extra_args.extend(['--dev', '/dev'])
else:
if is_mount_writable(mnt_target, writable_paths):
extra_args.extend(['--bind', mnt_src, mnt_target])
else:
extra_args.extend(['--ro-bind', mnt_src, mnt_target])
return extra_args
def is_mount_writable(mnt, writable_paths):
#Deal with the catch all statements first
if writable_paths == 'all':
return True
elif writable_paths in ['none', []]:
return False
elif type(writable_paths) is list:
return mnt in writable_paths
#Default/unknown case
else:
logging.getLogger("sandboxlib").warn("Unknown [Bwrap]writable_path arg type "\
"given : {} type({})".format(writable_paths, type(writable_paths)))
return False
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