############################################################################
# Copyright (C) 2012-2016  Internet Systems Consortium, Inc. ("ISC")
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
############################################################################

import argparse
import os
import sys
from subprocess import Popen, PIPE

from isc.utils import prefix,version

prog = 'dnssec-checkds'


############################################################################
# SECRR class:
# Class for DS/DLV resource record
############################################################################
class SECRR:
    hashalgs = {1: 'SHA-1', 2: 'SHA-256', 3: 'GOST', 4: 'SHA-384'}
    rrname = ''
    rrclass = 'IN'
    keyid = None
    keyalg = None
    hashalg = None
    digest = ''
    ttl = 0

    def __init__(self, rrtext, dlvname = None):
        if not rrtext:
            raise Exception

        fields = rrtext.decode('ascii').split()
        if len(fields) < 7:
            raise Exception

        if dlvname:
            self.rrtype = "DLV"
            self.dlvname = dlvname.lower()
            parent = fields[0].lower().strip('.').split('.')
            parent.reverse()
            dlv = dlvname.split('.')
            dlv.reverse()
            while len(dlv) != 0 and len(parent) != 0 and parent[0] == dlv[0]:
                parent = parent[1:]
                dlv = dlv[1:]
            if dlv:
                raise Exception
            parent.reverse()
            self.parent = '.'.join(parent)
            self.rrname = self.parent + '.' + self.dlvname + '.'
        else:
            self.rrtype = "DS"
            self.rrname = fields[0].lower()

        fields = fields[1:]
        if fields[0].upper() in ['IN', 'CH', 'HS']:
            self.rrclass = fields[0].upper()
            fields = fields[1:]
        else:
            self.ttl = int(fields[0])
            self.rrclass = fields[1].upper()
            fields = fields[2:]

        if fields[0].upper() != self.rrtype:
            raise Exception('%s does not match %s' %
                            (fields[0].upper(), self.rrtype))

        self.keyid, self.keyalg, self.hashalg = map(int, fields[1:4])
        self.digest = ''.join(fields[4:]).upper()

    def __repr__(self):
        return '%s %s %s %d %d %d %s' % \
               (self.rrname, self.rrclass, self.rrtype,
                self.keyid, self.keyalg, self.hashalg, self.digest)

    def __eq__(self, other):
        return self.__repr__() == other.__repr__()


############################################################################
# check:
# Fetch DS/DLV RRset for the given zone from the DNS; fetch DNSKEY
# RRset from the masterfile if specified, or from DNS if not.
# Generate a set of expected DS/DLV records from the DNSKEY RRset,
# and report on congruency.
############################################################################
def check(zone, args, masterfile=None, lookaside=None):
    rrlist = []
    cmd = [args.dig, "+noall", "+answer", "-t", "dlv" if lookaside else "ds",
           "-q", zone + "." + lookaside if lookaside else zone]
    fp, _ = Popen(cmd, stdout=PIPE).communicate()

    for line in fp.splitlines():
        rrlist.append(SECRR(line, lookaside))
    rrlist = sorted(rrlist, key=lambda rr: (rr.keyid, rr.keyalg, rr.hashalg))

    klist = []

    if masterfile:
        cmd = [args.dsfromkey, "-f", masterfile]
        if lookaside:
            cmd += ["-l", lookaside]
        cmd.append(zone)
        fp, _ = Popen(cmd, stdout=PIPE).communicate()
    else:
        intods, _ = Popen([args.dig, "+noall", "+answer", "-t", "dnskey",
                           "-q", zone], stdout=PIPE).communicate()
        cmd = [args.dsfromkey, "-f", "-"]
        if lookaside:
            cmd += ["-l", lookaside]
        cmd.append(zone)
        fp, _ = Popen(cmd, stdin=PIPE, stdout=PIPE).communicate(intods)

    for line in fp.splitlines():
        klist.append(SECRR(line, lookaside))

    if len(klist) < 1:
        print("No DNSKEY records found in zone apex")
        return False

    found = False
    for rr in klist:
        if rr in rrlist:
            print("%s for KSK %s/%03d/%05d (%s) found in parent" %
                  (rr.rrtype, rr.rrname.strip('.'), rr.keyalg,
                   rr.keyid, SECRR.hashalgs[rr.hashalg]))
            found = True
        else:
            print("%s for KSK %s/%03d/%05d (%s) missing from parent" %
                  (rr.rrtype, rr.rrname.strip('.'), rr.keyalg,
                   rr.keyid, SECRR.hashalgs[rr.hashalg]))

    if not found:
        print("No %s records were found for any DNSKEY" % ("DLV" if lookaside else "DS"))

    return found

############################################################################
# parse_args:
# Read command line arguments, set global 'args' structure
############################################################################
def parse_args():
    parser = argparse.ArgumentParser(description=prog + ': checks DS coverage')

    bindir = 'bin'
    sbindir = 'bin' if os.name == 'nt' else 'sbin'

    parser.add_argument('zone', type=str, help='zone to check')
    parser.add_argument('-f', '--file', dest='masterfile', type=str,
                        help='zone master file')
    parser.add_argument('-l', '--lookaside', dest='lookaside', type=str,
                        help='DLV lookaside zone')
    parser.add_argument('-d', '--dig', dest='dig',
                        default=os.path.join(prefix(bindir), 'dig'),
                        type=str, help='path to \'dig\'')
    parser.add_argument('-D', '--dsfromkey', dest='dsfromkey',
                        default=os.path.join(prefix(sbindir),
                                             'dnssec-dsfromkey'),
                        type=str, help='path to \'dig\'')
    parser.add_argument('-v', '--version', action='version',
                        version=version)
    args = parser.parse_args()

    args.zone = args.zone.strip('.')
    if args.lookaside:
        args.lookaside = args.lookaside.strip('.')

    return args


############################################################################
# Main
############################################################################
def main():
    args = parse_args()
    found = check(args.zone, args, args.masterfile, args.lookaside)
    exit(0 if found else 1)
