#!/usr/bin/env python
# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright (c) 2011 OpenStack, LLC.
# 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.

"""Root wrapper for OpenStack services

   Filters which commands a service is allowed to run as another user.

   To use this with oslo, you should set the following in
   oslo.conf:
   rootwrap_config=/etc/oslo/rootwrap.conf

   You also need to let the oslo user run oslo-rootwrap
   as root in sudoers:
   oslo ALL = (root) NOPASSWD: /usr/bin/oslo-rootwrap
                                   /etc/oslo/rootwrap.conf *

   Service packaging should deploy .filters files only on nodes where
   they are needed, to avoid allowing more than is necessary.
"""

import ConfigParser
import logging
import os
import pwd
import signal
import subprocess
import sys


RC_UNAUTHORIZED = 99
RC_NOCOMMAND = 98
RC_BADCONFIG = 97
RC_NOEXECFOUND = 96


def _subprocess_setup():
    # Python installs a SIGPIPE handler by default. This is usually not what
    # non-Python subprocesses expect.
    signal.signal(signal.SIGPIPE, signal.SIG_DFL)


def _exit_error(execname, message, errorcode, log=True):
    print "%s: %s" % (execname, message)
    if log:
        logging.error(message)
    sys.exit(errorcode)


if __name__ == '__main__':
    # Split arguments, require at least a command
    execname = sys.argv.pop(0)
    if len(sys.argv) < 2:
        _exit_error(execname, "No command specified", RC_NOCOMMAND, log=False)

    configfile = sys.argv.pop(0)
    userargs = sys.argv[:]

    # Add ../ to sys.path to allow running from branch
    possible_topdir = os.path.normpath(os.path.join(os.path.abspath(execname),
                                                    os.pardir, os.pardir))
    if os.path.exists(os.path.join(possible_topdir, "oslo", "__init__.py")):
        sys.path.insert(0, possible_topdir)

    from openstack.common.rootwrap import wrapper

    # Load configuration
    try:
        rawconfig = ConfigParser.RawConfigParser()
        rawconfig.read(configfile)
        config = wrapper.RootwrapConfig(rawconfig)
    except ValueError as exc:
        msg = "Incorrect value in %s: %s" % (configfile, exc.message)
        _exit_error(execname, msg, RC_BADCONFIG, log=False)
    except ConfigParser.Error:
        _exit_error(execname, "Incorrect configuration file: %s" % configfile,
                    RC_BADCONFIG, log=False)

    if config.use_syslog:
        wrapper.setup_syslog(execname,
                             config.syslog_log_facility,
                             config.syslog_log_level)

    # Execute command if it matches any of the loaded filters
    filters = wrapper.load_filters(config.filters_path)
    try:
        filtermatch = wrapper.match_filter(filters, userargs,
                                           exec_dirs=config.exec_dirs)
        if filtermatch:
            command = filtermatch.get_command(userargs,
                                              exec_dirs=config.exec_dirs)
            if config.use_syslog:
                logging.info("(%s > %s) Executing %s (filter match = %s)" % (
                    os.getlogin(), pwd.getpwuid(os.getuid())[0],
                    command, filtermatch.name))

            obj = subprocess.Popen(command,
                                   stdin=sys.stdin,
                                   stdout=sys.stdout,
                                   stderr=sys.stderr,
                                   preexec_fn=_subprocess_setup,
                                   env=filtermatch.get_environment(userargs))
            obj.wait()
            sys.exit(obj.returncode)

    except wrapper.FilterMatchNotExecutable as exc:
        msg = ("Executable not found: %s (filter match = %s)"
               % (exc.match.exec_path, exc.match.name))
        _exit_error(execname, msg, RC_NOEXECFOUND, log=config.use_syslog)

    except wrapper.NoFilterMatched:
        msg = ("Unauthorized command: %s (no filter matched)"
               % ' '.join(userargs))
        _exit_error(execname, msg, RC_UNAUTHORIZED, log=config.use_syslog)