pf tests: Verify (tcp) checksum modification on unaligned options
It turns out pf incorrectly updates the TCP checksum if the TCP option we're modifying is not 2-byte algined with respect to the start of the packet. Create a TCP packet with such an option and throw it through a scrub rule, which will update timestamps and modify the packet. PR: 240416 MFC after: 1 week Differential revision: https://reviews.freebsd.org/D27688
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@ -28,6 +28,7 @@
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import argparse
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import scapy.all as sp
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import socket
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import sys
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from sniffer import Sniffer
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@ -113,6 +114,53 @@ def ping6(send_if, dst_ip, args):
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req = ether / ip6 / icmp
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sp.sendp(req, iface=send_if, verbose=False)
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def check_tcpsyn(args, packet):
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dst_ip = args.to[0]
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ip = packet.getlayer(sp.IP)
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if not ip:
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return False
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if ip.dst != dst_ip:
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return False
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tcp = packet.getlayer(sp.TCP)
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if not tcp:
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return False
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# Verify IP checksum
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chksum = ip.chksum
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ip.chksum = None
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new_chksum = sp.IP(sp.raw(ip)).chksum
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if chksum != new_chksum:
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print("Expected IP checksum %x but found %x\n" % (new_cshkum, chksum))
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return False
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# Verify TCP checksum
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chksum = tcp.chksum
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packet_raw = sp.raw(packet)
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tcp.chksum = None
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newpacket = sp.Ether(sp.raw(packet[sp.Ether]))
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new_chksum = newpacket[sp.TCP].chksum
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if chksum != new_chksum:
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print("Expected TCP checksum %x but found %x\n" % (new_chksum, chksum))
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return False
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return True
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def tcpsyn(send_if, dst_ip, args):
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opts=[('Timestamp', (1, 1)), ('MSS', 1280)]
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if args.tcpopt_unaligned:
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opts = [('NOP', 0 )] + opts
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ether = sp.Ether()
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ip = sp.IP(dst=dst_ip)
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tcp = sp.TCP(dport=666, flags='S', options=opts)
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req = ether / ip / tcp
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sp.sendp(req, iface=send_if, verbose=False)
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def main():
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parser = argparse.ArgumentParser("pft_ping.py",
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description="Ping test tool")
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@ -127,6 +175,12 @@ def main():
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required=True,
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help='The destination IP address for the ICMP echo request')
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# TCP options
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parser.add_argument('--tcpsyn', action='store_true',
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help='Send a TCP SYN packet')
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parser.add_argument('--tcpopt_unaligned', action='store_true',
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help='Include unaligned TCP options')
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# Packet settings
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parser.add_argument('--send-tos', nargs=1,
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help='Set the ToS value for the transmitted packet')
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@ -142,12 +196,19 @@ def main():
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sniffer = None
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if not args.recvif is None:
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sniffer = Sniffer(args, check_ping_request)
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checkfn=check_ping_request
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if args.tcpsyn:
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checkfn=check_tcpsyn
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if args.ip6:
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ping6(args.sendif[0], args.to[0], args)
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sniffer = Sniffer(args, checkfn)
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if args.tcpsyn:
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tcpsyn(args.sendif[0], args.to[0], args)
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else:
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ping(args.sendif[0], args.to[0], args)
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if args.ip6:
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ping6(args.sendif[0], args.to[0], args)
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else:
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ping(args.sendif[0], args.to[0], args)
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if sniffer:
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sniffer.join()
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@ -6,6 +6,7 @@ TESTSDIR= ${TESTSBASE}/sys/netpfil/pf
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TESTS_SUBDIRS+= ioctl
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ATF_TESTS_SH+= anchor \
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checksum \
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forward \
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fragmentation \
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icmp \
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85
tests/sys/netpfil/pf/checksum.sh
Normal file
85
tests/sys/netpfil/pf/checksum.sh
Normal file
@ -0,0 +1,85 @@
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# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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#
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# Copyright (c) 2020 Kristof Provost <kp@FreeBSD.org>
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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. $(atf_get_srcdir)/utils.subr
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common_dir=$(atf_get_srcdir)/../common
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atf_test_case "unaligned" "cleanup"
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unaligned_head()
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{
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atf_set descr 'Test unaligned checksum updates'
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atf_set require.user root
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}
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unaligned_body()
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{
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pft_init
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epair_in=$(vnet_mkepair)
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epair_out=$(vnet_mkepair)
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vnet_mkjail alcatraz ${epair_in}b ${epair_out}a
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ifconfig ${epair_in}a 192.0.2.2/24 up
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route add -net 198.51.100.0/24 192.0.2.1
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jexec alcatraz ifconfig ${epair_in}b 192.0.2.1/24 up
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jexec alcatraz sysctl net.inet.ip.forwarding=1
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jexec alcatraz ifconfig ${epair_out}a 198.51.100.1/24 up
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jexec alcatraz arp -s 198.51.100.2 00:01:02:03:04:05
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ifconfig ${epair_out}b up
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jexec alcatraz pfctl -e
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pft_set_rules alcatraz \
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"scrub on ${epair_in}b reassemble tcp max-mss 1200"
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# Check aligned
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atf_check -s exit:0 ${common_dir}/pft_ping.py \
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--sendif ${epair_in}a \
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--to 198.51.100.2 \
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--recvif ${epair_out}b \
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--tcpsyn
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# And unaligned
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atf_check -s exit:0 ${common_dir}/pft_ping.py \
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--sendif ${epair_in}a \
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--to 198.51.100.2 \
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--recvif ${epair_out}b \
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--tcpsyn \
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--tcpopt_unaligned
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}
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unaligned_cleanup()
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{
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pft_cleanup
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}
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atf_init_test_cases()
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{
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atf_add_test_case "unaligned"
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}
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