#!/usr/bin/env python3
# Copyright 2014-2015, Tresys Technology, LLC
#
# This file is part of SETools.
#
# SETools 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, either version 2 of the License, or
# (at your option) any later version.
#
# SETools 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 SETools.  If not, see <http://www.gnu.org/licenses/>.
#

import setools
import argparse
import sys
import logging
import signal

signal.signal(signal.SIGPIPE, signal.SIG_DFL)

parser = argparse.ArgumentParser(
    description="SELinux policy information flow analysis tool.",
    epilog="If no analysis is selected, all information flow out of the source will be printed.")
parser.add_argument("--version", action="version", version=setools.__version__)
parser.add_argument("--stats", action="store_true",
                    help="Display statistics at the end of the analysis.")
parser.add_argument("-v", "--verbose", action="store_true",
                    help="Print extra informational messages")
parser.add_argument("--debug", action="store_true", dest="debug", help="Enable debugging.")

settings = parser.add_argument_group("Analysis settings")
settings.add_argument("-p", "--policy",
                      help="Path to SELinux policy to analyze.")
settings.add_argument("-m", "--map", required=True,
                      help="Path to permission map file.")
settings.add_argument("-s", "--source", required=True,
                      help="Source type of the analysis.")
settings.add_argument("-t", "--target", default="",
                      help="Target type of the analysis.")

alg = parser.add_argument_group("Analysis algorithm")
alg.add_argument("-S", "--shortest_path", action="store_true",
                 help="Calculate all shortest paths.")
alg.add_argument("-A", "--all_paths", type=int, metavar="MAX_STEPS",
                 help="Calculate all paths, with the specified maximum path length. (Expensive)")

opts = parser.add_argument_group("Analysis options")
opts.add_argument("-w", "--min_weight", default=3, type=int,
                  help="Minimum permission weight.  Default is 3.")
opts.add_argument("-l", "--limit_flows", default=0, type=int,
                  help="Limit to the specified number of flows.  Default is unlimited.")
opts.add_argument("exclude", nargs="*",
                  help="List of excluded types in the analysis.")

args = parser.parse_args()

if not args.target and (args.shortest_path or args.all_paths):
    parser.error("The target type must be specified to determine a path.")

if args.target and not (args.shortest_path or args.all_paths):
    parser.error("A target type is not used for flows in/out of a type.")

if args.limit_flows < 0:
    parser.error("Limit on information flows cannot be negative.")

if args.debug:
    logging.basicConfig(level=logging.DEBUG,
                        format='%(asctime)s|%(levelname)s|%(name)s|%(message)s')
elif args.verbose:
    logging.basicConfig(level=logging.INFO, format='%(message)s')
else:
    logging.basicConfig(level=logging.WARNING, format='%(message)s')

try:
    p = setools.SELinuxPolicy(args.policy)
    m = setools.PermissionMap(args.map)
    g = setools.InfoFlowAnalysis(p, m, min_weight=args.min_weight, exclude=args.exclude)

    if args.shortest_path or args.all_paths:
        if args.shortest_path:
            paths = g.all_shortest_paths(args.source, args.target)
        else:
            paths = g.all_paths(args.source, args.target, args.all_paths)

        flownum = 0
        for flownum, path in enumerate(paths, start=1):
            print("Flow {0}:".format(flownum))
            for stepnum, step in enumerate(path, start=1):
                print("  Step {0}: {1} -> {2}".format(stepnum, step.source, step.target))

                for rule in sorted(step.rules):
                    print("   ", rule)

                print()

            if args.limit_flows and flownum >= args.limit_flows:
                break

            print()

    else:  # single direct info flow
        flownum = 0
        for flownum, flow in enumerate(g.infoflows(args.source), start=1):
            print("Flow {0}: {1} -> {2}".format(flownum, flow.source, flow.target))
            for rule in sorted(flow.rules):
                print("   ", rule)

            print()

            if args.limit_flows and flownum >= args.limit_flows:
                break

    print(flownum, "information flow(s) found.")

    if args.stats:
        print("\nGraph statistics:")
        print(g.get_stats())

except Exception as err:
    if args.debug:
        raise
    else:
        print(err)

    sys.exit(1)
