# Copyright (c) 2011 OpenStack Foundation.
# 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 logging
import os
import sys

from oslo_rootwrap import subprocess
from oslo_rootwrap import wrapper

from six import moves

try:
    # This isn't available on all platforms (e.g. Windows).
    import resource
except ImportError:
    resource = None

RC_UNAUTHORIZED = 99
RC_NOCOMMAND = 98
RC_BADCONFIG = 97
RC_NOEXECFOUND = 96
SIGNAL_BASE = 128


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


def daemon():
    return main(run_daemon=True)


def main(run_daemon=False):
    # Split arguments, require at least a command
    execname = sys.argv.pop(0)
    if run_daemon:
        if len(sys.argv) != 1:
            _exit_error(execname, "Extra arguments to daemon", RC_NOCOMMAND,
                        log=False)
    else:
        if len(sys.argv) < 2:
            _exit_error(execname, "No command specified", RC_NOCOMMAND,
                        log=False)

    configfile = sys.argv.pop(0)

    # Load configuration
    try:
        rawconfig = moves.configparser.RawConfigParser()
        rawconfig.read(configfile)
        config = wrapper.RootwrapConfig(rawconfig)
    except ValueError as exc:
        msg = "Incorrect value in %s: %s" % (configfile, exc.args[0])
        _exit_error(execname, msg, RC_BADCONFIG, log=False)
    except moves.configparser.Error:
        _exit_error(execname, "Incorrect configuration file: %s" % configfile,
                    RC_BADCONFIG, log=False)

    if resource:
        # When use close_fds=True on Python 2.x, calling subprocess with
        # close_fds=True (which we do by default) can be inefficient when
        # the current fd ulimits are large, because it blindly closes
        # all fds in the range(1, $verylargenumber)

        # Lower our ulimit to a reasonable value to regain performance.
        fd_limits = resource.getrlimit(resource.RLIMIT_NOFILE)
        sensible_fd_limit = min(config.rlimit_nofile, fd_limits[0])
        if (fd_limits[0] > sensible_fd_limit):
            # Close any fd beyond sensible_fd_limit prior adjusting our
            # rlimit to ensure all fds are closed
            for fd_entry in os.listdir('/proc/self/fd'):
                # NOTE(dmllr): In a previous patch revision non-numeric
                # dir entries were silently ignored which reviewers
                # didn't like. Readd exception handling when it occurs.
                fd = int(fd_entry)
                if fd >= sensible_fd_limit:
                    os.close(fd)
            # Unfortunately this inherits to our children, so allow them to
            # re-raise by passing through the hard limit unmodified
            resource.setrlimit(
                resource.RLIMIT_NOFILE, (sensible_fd_limit, fd_limits[1]))
            # This is set on import to the hard ulimit. if its defined we
            # already have imported it, so we need to update it to the new
            # limit.
            if (hasattr(subprocess, 'MAXFD') and
                    subprocess.MAXFD > sensible_fd_limit):
                subprocess.MAXFD = sensible_fd_limit

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

    filters = wrapper.load_filters(config.filters_path)

    if run_daemon:
        # NOTE(dims): When not running as daemon, this import
        # slows us down just a bit. So moving it here so we have
        # it only when we need it.
        from oslo_rootwrap import daemon as daemon_mod
        daemon_mod.daemon_start(config, filters)
    else:
        run_one_command(execname, config, filters, sys.argv)


def run_one_command(execname, config, filters, userargs):
    # Execute command if it matches any of the loaded filters
    try:
        obj = wrapper.start_subprocess(
            filters, userargs,
            exec_dirs=config.exec_dirs,
            log=config.use_syslog,
            stdin=sys.stdin,
            stdout=sys.stdout,
            stderr=sys.stderr)
        returncode = obj.wait()
        # Fix returncode of Popen
        if returncode < 0:
            returncode = SIGNAL_BASE - returncode
        sys.exit(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)
