mitogen/ansible_mitogen/target.py

300 lines
9.0 KiB
Python

# Copyright 2017, David Wilson
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its contributors
# may be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
"""
Helper functions intended to be executed on the target. These are entrypoints
for file transfer, module execution and sundry bits like changing file modes.
"""
from __future__ import absolute_import
import json
import logging
import operator
import os
import pwd
import random
import re
import stat
import subprocess
import tempfile
import threading
import zlib
import ansible_mitogen.runner
import ansible_mitogen.services
import mitogen.core
import mitogen.fork
import mitogen.parent
import mitogen.service
LOG = logging.getLogger(__name__)
#: Caching of fetched file data.
_file_cache = {}
#: Initialized to an econtext.parent.Context pointing at a pristine fork of
#: the target Python interpreter before it executes any code or imports.
_fork_parent = None
def get_file(context, path):
"""
Basic in-memory caching module fetcher. This generates an one roundtrip for
every previously unseen file, so it is only a temporary solution.
:param context:
Context we should direct FileService requests to. For now (and probably
forever) this is just the top-level Mitogen connection manager process.
:param path:
Path to fetch from FileService, must previously have been registered by
a privileged context using the `register` command.
:returns:
Bytestring file data.
"""
if path not in _file_cache:
_file_cache[path] = zlib.decompress(
mitogen.service.call(
context=context,
handle=ansible_mitogen.services.FileService.handle,
method='fetch',
kwargs={
'path': path
}
)
)
return _file_cache[path]
@mitogen.core.takes_econtext
def start_fork_parent(econtext):
"""
Called by ContextService immediately after connection; arranges for the
(presently) spotless Python interpreter to be forked, where the newly
forked interpreter becomes the parent of any newly forked future
interpreters.
This is necessary to prevent modules that are executed in-process from
polluting the global interpreter state in a way that effects explicitly
isolated modules.
"""
global _fork_parent
mitogen.parent.upgrade_router(econtext)
_fork_parent = econtext.router.fork()
@mitogen.core.takes_econtext
def start_fork_child(kwargs, econtext):
mitogen.parent.upgrade_router(econtext)
context = econtext.router.fork()
kwargs['shutdown_on_exit'] = True
context.call_async(run_module, kwargs)
@mitogen.core.takes_econtext
def run_module(kwargs, econtext):
"""
Set up the process environment in preparation for running an Ansible
module. This monkey-patches the Ansible libraries in various places to
prevent it from trying to kill the process on completion, and to prevent it
from reading sys.stdin.
"""
should_fork = kwargs.pop('should_fork', False)
shutdown_on_exit = kwargs.pop('shutdown_on_exit', False)
if should_fork:
_fork_parent.call(start_fork_child, kwargs)
return
runner_name = kwargs.pop('runner_name')
klass = getattr(ansible_mitogen.runner, runner_name)
impl = klass(**kwargs)
impl.run()
if shutdown_on_exit:
econtext.broker.shutdown()
def make_temp_directory(base_dir):
"""
Handle creation of `base_dir` if it is absent, in addition to a unique
temporary directory within `base_dir`.
:returns:
Newly created temporary directory.
"""
if not os.path.exists(base_dir):
os.makedirs(base_dir, mode=int('0700', 8))
return tempfile.mkdtemp(
dir=base_dir,
prefix='ansible-mitogen-tmp-',
)
def get_user_shell():
"""
For commands executed directly via an SSH command-line, SSH looks up the
user's shell via getpwuid() and only defaults to /bin/sh if that field is
missing or empty.
"""
try:
pw_shell = pwd.getpwuid(os.geteuid()).pw_shell
except KeyError:
pw_shell = None
return pw_shell or '/bin/sh'
def exec_args(args, in_data='', chdir=None, shell=None, emulate_tty=False):
"""
Run a command in a subprocess, emulating the argument handling behaviour of
SSH.
:param list[str]:
Argument vector.
:param bytes in_data:
Optional standard input for the command.
:param bool emulate_tty:
If :data:`True`, arrange for stdout and stderr to be merged into the
stdout pipe and for LF to be translated into CRLF, emulating the
behaviour of a TTY.
:return:
(return code, stdout bytes, stderr bytes)
"""
LOG.debug('exec_args(%r, ..., chdir=%r)', args, chdir)
assert isinstance(args, list)
if emulate_tty:
stderr = subprocess.STDOUT
else:
stderr = subprocess.PIPE
proc = subprocess.Popen(
args=args,
stdout=subprocess.PIPE,
stderr=stderr,
stdin=subprocess.PIPE,
cwd=chdir,
)
stdout, stderr = proc.communicate(in_data)
if emulate_tty:
stdout = stdout.replace('\n', '\r\n')
return proc.returncode, stdout, stderr or ''
def exec_command(cmd, in_data='', chdir=None, shell=None, emulate_tty=False):
"""
Run a command in a subprocess, emulating the argument handling behaviour of
SSH.
:param bytes cmd:
String command line, passed to user's shell.
:param bytes in_data:
Optional standard input for the command.
:return:
(return code, stdout bytes, stderr bytes)
"""
assert isinstance(cmd, basestring)
return exec_args(
args=[get_user_shell(), '-c', cmd],
in_data=in_data,
chdir=chdir,
shell=shell,
emulate_tty=emulate_tty,
)
def read_path(path):
"""
Fetch the contents of a filesystem `path` as bytes.
"""
return open(path, 'rb').read()
def write_path(path, s):
"""
Writes bytes `s` to a filesystem `path`.
"""
open(path, 'wb').write(s)
CHMOD_CLAUSE_PAT = re.compile(r'([uoga]*)([+\-=])([ugo]|[rwx]*)')
CHMOD_MASKS = {
'u': stat.S_IRWXU,
'g': stat.S_IRWXG,
'o': stat.S_IRWXO,
'a': (stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO),
}
CHMOD_BITS = {
'u': {'r': stat.S_IRUSR, 'w': stat.S_IWUSR, 'x': stat.S_IXUSR},
'g': {'r': stat.S_IRGRP, 'w': stat.S_IWGRP, 'x': stat.S_IXGRP},
'o': {'r': stat.S_IROTH, 'w': stat.S_IWOTH, 'x': stat.S_IXOTH},
'a': {
'r': (stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH),
'w': (stat.S_IWUSR | stat.S_IWGRP | stat.S_IWOTH),
'x': (stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)
}
}
def apply_mode_spec(spec, mode):
"""
Given a symbolic file mode change specification in the style of chmod(1)
`spec`, apply changes in the specification to the numeric file mode `mode`.
"""
for clause in spec.split(','):
match = CHMOD_CLAUSE_PAT.match(clause)
who, op, perms = match.groups()
for ch in who or 'a':
mask = CHMOD_MASKS[ch]
bits = CHMOD_BITS[ch]
cur_perm_bits = mode & mask
new_perm_bits = reduce(operator.or_, (bits[p] for p in perms), 0)
mode &= ~mask
if op == '=':
mode |= new_perm_bits
elif op == '+':
mode |= new_perm_bits | cur_perm_bits
else:
mode |= cur_perm_bits & ~new_perm_bits
return mode
def set_file_mode(path, spec):
"""
Update the permissions of a file using the same syntax as chmod(1).
"""
mode = os.stat(path).st_mode
if spec.isdigit():
new_mode = int(spec, 8)
else:
new_mode = apply_mode_spec(spec, mode)
os.chmod(path, new_mode)