#!/usr/bin/env python3
#
# SPDX-License-Identifier: BSD-2-Clause
#
# Copyright (c) 2017 Kristof Provost <kp@FreeBSD.org>
# Copyright (c) 2023 Kajetan Staszkiewicz <vegeta@tuxpowered.net>
#
# 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.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
#

import argparse
import logging
logging.getLogger("scapy").setLevel(logging.CRITICAL)
import math
import scapy.all as sp
import sys

from copy import copy
from sniffer import Sniffer

logging.basicConfig(format='%(message)s')
LOGGER = logging.getLogger(__name__)

PAYLOAD_MAGIC = bytes.fromhex('42c0ffee')

def build_payload(l):
    pl = len(PAYLOAD_MAGIC)
    ret = PAYLOAD_MAGIC * math.floor(l/pl)
    ret += PAYLOAD_MAGIC[0:(l % pl)]
    return ret


def prepare_ipv6(dst_address, send_params):
    src_address = send_params.get('src_address')
    hlim = send_params.get('hlim')
    tc = send_params.get('tc')
    ip6 = sp.IPv6(dst=dst_address)
    if src_address:
        ip6.src = src_address
    if hlim:
        ip6.hlim = hlim
    if tc:
        ip6.tc = tc
    return ip6


def prepare_ipv4(dst_address, send_params):
    src_address = send_params.get('src_address')
    flags = send_params.get('flags')
    tos = send_params.get('tc')
    ttl = send_params.get('hlim')
    ip = sp.IP(dst=dst_address)
    if src_address:
        ip.src = src_address
    if flags:
        ip.flags = flags
    if tos:
        ip.tos = tos
    if ttl:
        ip.ttl = ttl
    return ip


def send_icmp_ping(dst_address, sendif, send_params):
    send_length = send_params['length']
    ether = sp.Ether()
    if ':' in dst_address:
        ip6 = prepare_ipv6(dst_address, send_params)
        icmp = sp.ICMPv6EchoRequest(data=sp.raw(build_payload(send_length)))
        req = ether / ip6 / icmp
    else:
        ip = prepare_ipv4(dst_address, send_params)
        icmp = sp.ICMP(type='echo-request')
        raw = sp.raw(build_payload(send_length))
        req = ether / ip / icmp / raw
    sp.sendp(req, sendif, verbose=False)


def send_tcp_syn(dst_address, sendif, send_params):
    tcpopt_unaligned = send_params.get('tcpopt_unaligned')
    seq = send_params.get('seq')
    mss = send_params.get('mss')
    ether = sp.Ether()
    opts=[('Timestamp', (1, 1)), ('MSS', mss if mss else 1280)]
    if tcpopt_unaligned:
        opts = [('NOP', 0 )] + opts
    if ':' in dst_address:
        ip = prepare_ipv6(dst_address, send_params)
    else:
        ip = prepare_ipv4(dst_address, send_params)
    tcp = sp.TCP(dport=666, flags='S', options=opts, seq=seq)
    req = ether / ip / tcp
    sp.sendp(req, iface=sendif, verbose=False)


def send_ping(dst_address, sendif, ping_type, send_params):
    if ping_type == 'icmp':
        send_icmp_ping(dst_address, sendif, send_params)
    elif ping_type == 'tcpsyn':
        send_tcp_syn(dst_address, sendif, send_params)
    else:
        raise Exception('Unspported ping type')


def check_ipv4(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    flags = expect_params.get('flags')
    tos = expect_params.get('tc')
    ttl = expect_params.get('hlim')
    ip = packet.getlayer(sp.IP)
    if not ip:
        LOGGER.debug('Packet is not IPv4!')
        return False
    if src_address and ip.src != src_address:
        LOGGER.debug('Source IPv4 address does not match!')
        return False
    if dst_address and ip.dst != dst_address:
        LOGGER.debug('Destination IPv4 address does not match!')
        return False
    chksum = ip.chksum
    ip.chksum = None
    new_chksum = sp.IP(sp.raw(ip)).chksum
    if chksum != new_chksum:
        LOGGER.debug(f'Expected IP checksum {new_chksum} but found {chksum}')
        return False
    if flags and ip.flags != flags:
        LOGGER.debug(f'Wrong IP flags value {ip.flags}, expected {flags}')
        return False
    if tos and ip.tos != tos:
        LOGGER.debug(f'Wrong ToS value {ip.tos}, expected {tos}')
        return False
    if ttl and ip.ttl != ttl:
        LOGGER.debug(f'Wrong TTL value {ip.ttl}, expected {ttl}')
        return False
    return True


def check_ipv6(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    flags = expect_params.get('flags')
    hlim = expect_params.get('hlim')
    tc = expect_params.get('tc')
    ip6 = packet.getlayer(sp.IPv6)
    if not ip6:
        LOGGER.debug('Packet is not IPv6!')
        return False
    if src_address and ip6.src != src_address:
        LOGGER.debug('Source IPv6 address does not match!')
        return False
    if dst_address and ip6.dst != dst_address:
        LOGGER.debug('Destination IPv6 address does not match!')
        return False
    # IPv6 has no IP-level checksum.
    if flags:
        raise Exception("There's no fragmentation flags in IPv6")
    if hlim and ip6.hlim != hlim:
        LOGGER.debug(f'Wrong Hop Limit value {ip6.hlim}, expected {hlim}')
        return False
    if tc and ip6.tc != tc:
        LOGGER.debug(f'Wrong TC value {ip6.tc}, expected {tc}')
        return False
    return True


def check_ping_4(expect_params, packet):
    expect_length = expect_params['length']
    if not check_ipv4(expect_params, packet):
        return False
    icmp = packet.getlayer(sp.ICMP)
    if not icmp:
        LOGGER.debug('Packet is not IPv4 ICMP!')
        return False
    raw = packet.getlayer(sp.Raw)
    if not raw:
        LOGGER.debug('Packet contains no payload!')
        return False
    if raw.load != build_payload(expect_length):
        LOGGER.debug('Payload magic does not match!')
        return False
    return True


def check_ping_request_4(expect_params, packet):
    if not check_ping_4(expect_params, packet):
        return False
    icmp = packet.getlayer(sp.ICMP)
    if sp.icmptypes[icmp.type] != 'echo-request':
        LOGGER.debug('Packet is not IPv4 ICMP Echo Request!')
        return False
    return True


def check_ping_reply_4(expect_params, packet):
    if not check_ping_4(expect_params, packet):
        return False
    icmp = packet.getlayer(sp.ICMP)
    if sp.icmptypes[icmp.type] != 'echo-reply':
        LOGGER.debug('Packet is not IPv4 ICMP Echo Reply!')
        return False
    return True


def check_ping_request_6(expect_params, packet):
    expect_length = expect_params['length']
    if not check_ipv6(expect_params, packet):
        return False
    icmp = packet.getlayer(sp.ICMPv6EchoRequest)
    if not icmp:
        LOGGER.debug('Packet is not IPv6 ICMP Echo Request!')
        return False
    if icmp.data != build_payload(expect_length):
        LOGGER.debug('Payload magic does not match!')
        return False
    return True


def check_ping_reply_6(expect_params, packet):
    expect_length = expect_params['length']
    if not check_ipv6(expect_params, packet):
        return False
    icmp = packet.getlayer(sp.ICMPv6EchoReply)
    if not icmp:
        LOGGER.debug('Packet is not IPv6 ICMP Echo Reply!')
        return False
    if icmp.data != build_payload(expect_length):
        LOGGER.debug('Payload magic does not match!')
        return False
    return True


def check_ping_request(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    if not (src_address or dst_address):
        raise Exception('Source or destination address must be given to match the ping request!')
    if (
        (src_address and ':' in src_address) or
        (dst_address and ':' in dst_address)
    ):
        return check_ping_request_6(expect_params, packet)
    else:
        return check_ping_request_4(expect_params, packet)


def check_ping_reply(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    if not (src_address or dst_address):
        raise Exception('Source or destination address must be given to match the ping reply!')
    if (
        (src_address and ':' in src_address) or
        (dst_address and ':' in dst_address)
    ):
        return check_ping_reply_6(expect_params, packet)
    else:
        return check_ping_reply_4(expect_params, packet)


def check_tcp(expect_params, packet):
    tcp_flags = expect_params.get('tcp_flags')
    mss = expect_params.get('mss')
    seq = expect_params.get('seq')
    tcp = packet.getlayer(sp.TCP)
    if not tcp:
        LOGGER.debug('Packet is not TCP!')
        return False
    chksum = tcp.chksum
    tcp.chksum = None
    newpacket = sp.Ether(sp.raw(packet[sp.Ether]))
    new_chksum = newpacket[sp.TCP].chksum
    if chksum != new_chksum:
        LOGGER.debug(f'Wrong TCP checksum {chksum}, expected {new_chksum}!')
        return False
    if tcp_flags and tcp.flags != tcp_flags:
        LOGGER.debug(f'Wrong TCP flags {tcp.flags}, expected {tcp_flags}!')
        return False
    if seq:
        if tcp_flags == 'S':
            tcp_seq = tcp.seq
        elif tcp_flags == 'SA':
            tcp_seq = tcp.ack - 1
        if seq != tcp_seq:
            LOGGER.debug(f'Wrong TCP Sequence Number {tcp_seq}, expected {seq}')
            return False
    if mss:
        for option in tcp.options:
            if option[0] == 'MSS':
                if option[1] != mss:
                    LOGGER.debug(f'Wrong TCP MSS {option[1]}, expected {mss}')
                    return False
    return True


def check_tcp_syn_request_4(expect_params, packet):
    if not check_ipv4(expect_params, packet):
        return False
    if not check_tcp(expect_params | {'tcp_flags': 'S'}, packet):
        return False
    return True


def check_tcp_syn_reply_4(expect_params, packet):
    if not check_ipv4(expect_params, packet):
        return False
    if not check_tcp(expect_params | {'tcp_flags': 'SA'}, packet):
        return False
    return True


def check_tcp_syn_request_6(expect_params, packet):
    if not check_ipv6(expect_params, packet):
        return False
    if not check_tcp(expect_params | {'tcp_flags': 'S'}, packet):
        return False
    return True


def check_tcp_syn_reply_6(expect_params, packet):
    if not check_ipv6(expect_params, packet):
        return False
    if not check_tcp(expect_params | {'tcp_flags': 'SA'}, packet):
        return False
    return True


def check_tcp_syn_request(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    if not (src_address or dst_address):
        raise Exception('Source or destination address must be given to match the tcp syn request!')
    if (
        (src_address and ':' in src_address) or
        (dst_address and ':' in dst_address)
    ):
        return check_tcp_syn_request_6(expect_params, packet)
    else:
        return check_tcp_syn_request_4(expect_params, packet)


def check_tcp_syn_reply(expect_params, packet):
    src_address = expect_params.get('src_address')
    dst_address = expect_params.get('dst_address')
    if not (src_address or dst_address):
        raise Exception('Source or destination address must be given to match the tcp syn reply!')
    if (
        (src_address and ':' in src_address) or
        (dst_address and ':' in dst_address)
    ):
        return check_tcp_syn_reply_6(expect_params, packet)
    else:
        return check_tcp_syn_reply_4(expect_params, packet)


def setup_sniffer(recvif, ping_type, sniff_type, expect_params):
    if ping_type == 'icmp' and sniff_type == 'request':
        checkfn = check_ping_request
    elif ping_type == 'icmp' and sniff_type == 'reply':
        checkfn = check_ping_reply
    elif ping_type == 'tcpsyn' and sniff_type == 'request':
        checkfn = check_tcp_syn_request
    elif ping_type == 'tcpsyn' and sniff_type == 'reply':
        checkfn = check_tcp_syn_reply
    else:
        raise Exception('Unspported ping or sniff type')

    return Sniffer(expect_params, checkfn, recvif)


def parse_args():
    parser = argparse.ArgumentParser("pft_ping.py",
        description="Ping test tool")

    # Parameters of sent ping request
    parser.add_argument('--sendif', nargs=1,
        required=True,
        help='The interface through which the packet(s) will be sent')
    parser.add_argument('--to', nargs=1,
        required=True,
        help='The destination IP address for the ping request')
    parser.add_argument('--ping-type',
        choices=('icmp', 'tcpsyn'),
        help='Type of ping: ICMP (default) or TCP SYN',
        default='icmp')
    parser.add_argument('--fromaddr', nargs=1,
        help='The source IP address for the ping request')

    # Where to look for packets to analyze.
    # The '+' format is ugly as it mixes positional with optional syntax.
    # But we have no positional parameters so I guess it's fine to use it.
    parser.add_argument('--recvif', nargs='+',
        help='The interfaces on which to expect the ping request')
    parser.add_argument('--replyif', nargs='+',
        help='The interfaces which to expect the ping response')

    # Packet settings
    parser_send = parser.add_argument_group('Values set in transmitted packets')
    parser_send.add_argument('--send-flags', nargs=1, type=str,
        help='IPv4 fragmentation flags')
    parser_send.add_argument('--send-hlim', nargs=1, type=int,
        help='IPv6 Hop Limit or IPv4 Time To Live')
    parser_send.add_argument('--send-mss', nargs=1, type=int,
        help='TCP Maximum Segment Size')
    parser_send.add_argument('--send-seq', nargs=1, type=int,
        help='TCP sequence number')
    parser_send.add_argument('--send-length', nargs=1, type=int,
        default=[len(PAYLOAD_MAGIC)], help='ICMP Echo Request payload size')
    parser_send.add_argument('--send-tc', nargs=1, type=int,
        help='IPv6 Traffic Class or IPv4 DiffServ / ToS')
    parser_send.add_argument('--send-tcpopt-unaligned', action='store_true',
            help='Include unaligned TCP options')

    # Expectations
    parser_expect = parser.add_argument_group('Values expected in sniffed packets')
    parser_expect.add_argument('--expect-flags', nargs=1, type=str,
        help='IPv4 fragmentation flags')
    parser_expect.add_argument('--expect-hlim', nargs=1, type=int,
        help='IPv6 Hop Limit or IPv4 Time To Live')
    parser_expect.add_argument('--expect-mss', nargs=1, type=int,
        help='TCP Maximum Segment Size')
    parser_send.add_argument('--expect-seq', nargs=1, type=int,
        help='TCP sequence number')
    parser_expect.add_argument('--expect-tc', nargs=1, type=int,
        help='IPv6 Traffic Class or IPv4 DiffServ / ToS')

    parser.add_argument('-v', '--verbose', action='store_true',
        help=('Enable verbose logging. Apart of potentially useful information '
            'you might see warnings from parsing packets like NDP or other '
            'packets not related to the test being run. Use only when '
            'developing because real tests expect empty stderr and stdout.'))

    return parser.parse_args()


def main():
    args = parse_args()

    if args.verbose:
        LOGGER.setLevel(logging.DEBUG)

    # Dig out real values of program arguments
    send_if = args.sendif[0]
    reply_ifs = args.replyif
    recv_ifs = args.recvif
    dst_address = args.to[0]

    # Standardize parameters which have nargs=1.
    send_params = {}
    expect_params = {}
    for param_name in ('flags', 'hlim', 'length', 'mss', 'seq', 'tc'):
        param_arg = vars(args).get(f'send_{param_name}')
        send_params[param_name] = param_arg[0] if param_arg else None
        param_arg = vars(args).get(f'expect_{param_name}')
        expect_params[param_name] = param_arg[0] if param_arg else None

    expect_params['length'] = send_params['length']
    send_params['tcpopt_unaligned'] = args.send_tcpopt_unaligned
    send_params['src_address'] = args.fromaddr[0] if args.fromaddr else None

    # We may not have a default route. Tell scapy where to start looking for routes
    sp.conf.iface6 = send_if

    # Configuration sanity checking.
    if not (reply_ifs or recv_ifs):
        raise Exception('With no reply or recv interface specified no traffic '
            'can be sniffed and verified!'
        )

    sniffers = []

    if recv_ifs:
        sniffer_params = copy(expect_params)
        sniffer_params['src_address'] = None
        sniffer_params['dst_address'] = dst_address
        for iface in recv_ifs:
            LOGGER.debug(f'Installing receive sniffer on {iface}')
            sniffers.append(
                setup_sniffer(iface, args.ping_type, 'request', sniffer_params,
            ))

    if reply_ifs:
        sniffer_params = copy(expect_params)
        sniffer_params['src_address'] = dst_address
        sniffer_params['dst_address'] = None
        for iface in reply_ifs:
            LOGGER.debug(f'Installing reply sniffer on {iface}')
            sniffers.append(
                setup_sniffer(iface, args.ping_type, 'reply', sniffer_params,
            ))

    LOGGER.debug(f'Installed {len(sniffers)} sniffers')

    send_ping(dst_address, send_if, args.ping_type, send_params)

    err = 0
    sniffer_num = 0
    for sniffer in sniffers:
        sniffer.join()
        if sniffer.correctPackets == 1:
            LOGGER.debug(f'Expected ping has been sniffed on {sniffer._recvif}.')
        else:
            # Set a bit in err for each failed sniffer.
            err |= 1<<sniffer_num
            if sniffer.correctPackets > 1:
                LOGGER.debug(f'Duplicated ping has been sniffed on {sniffer._recvif}!')
            else:
                LOGGER.debug(f'Expected ping has not been sniffed on {sniffer._recvif}!')
        sniffer_num += 1

    return err


if __name__ == '__main__':
    sys.exit(main())