99 lines
4.1 KiB
OCaml
99 lines
4.1 KiB
OCaml
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let unwrap_ipv4 buf = Ipv4_packet.Unmarshal.of_cstruct buf |> Result.get_ok
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let verify_ipv4_udp = Ipv4_packet.Unmarshal.verify_transport_checksum ~proto:`UDP
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let verify_ipv4_tcp = Ipv4_packet.Unmarshal.verify_transport_checksum ~proto:`TCP
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let example_ipv4_udp = "\
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\x45\xb8\x00\x4c\xbf\x7c\x40\x00\x34\x11\xdf\x65\x90\x5c\x09\x16\
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\x0a\x89\x03\x0c\x00\x7b\x00\x7b\x00\x38\xf4\xfb\x24\x01\x03\xee\
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\x00\x00\x00\x00\x00\x00\x00\x43\x47\x50\x53\x00\xdc\x03\xd0\x04\
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\x53\x76\x73\x95\xdc\x03\xd0\x06\xcb\xd2\x4f\xfb\xdc\x03\xd0\x06\
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\xcd\x57\x43\xa0\xdc\x03\xd0\x06\xcd\xb6\x2e\x51"
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let example_ipv4_tcp = "\
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\x45\x00\x00\x34\x00\x00\x40\x00\x2d\x06\x47\x91\x93\x4b\x65\x53\
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\x0a\x89\x03\x0c\x01\xbb\xe5\xd0\x6f\x75\x20\x55\xf6\x5e\xdb\xef\
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\x80\x12\x72\x10\xad\x83\x00\x00\x02\x04\x05\x48\x01\x01\x04\x02\
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\x01\x03\x03\x08"
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let udp_ipv4_correct_positive () =
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let buf = Cstruct.of_string example_ipv4_udp in
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let (ipv4_header, transport_packet) = unwrap_ipv4 buf in
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Alcotest.(check bool) "for a correct UDP checksum, return true"
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true @@ verify_ipv4_udp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let udp_ipv4_correct_negative () =
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let buf = Cstruct.of_string example_ipv4_udp in
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Cstruct.BE.set_uint32 buf ((Cstruct.length buf) - 4) 0x1234l;
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let (ipv4_header, transport_packet) = unwrap_ipv4 buf in
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Alcotest.(check bool) "mutating the packet w/o fixing checksum causes verification to fail"
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false @@ verify_ipv4_udp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let udp_ipv4_allows_zero () =
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let buf = Cstruct.of_string example_ipv4_udp in
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let (ipv4_header, transport_packet) = unwrap_ipv4 buf in
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Udp_wire.set_checksum transport_packet 0x0000;
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Alcotest.(check bool) "0x0000 checksum is OK for UDP"
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true @@ verify_ipv4_udp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let udp_ipv4_zero_checksum () =
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let src = Ipaddr.V4.make 127 0 0 1 in
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let dst = src in
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let proto = `UDP in
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let ttl = 38 in
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let options = Cstruct.empty in
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let payload = Cstruct.of_hex "01 84" in
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let payload_len = Cstruct.length payload in
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let ipv4_header = Ipv4_packet.{
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src; dst;
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proto = Ipv4_packet.Marshal.protocol_to_int proto;
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ttl; id = 0 ; off = 0 ; options } in
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let pseudoheader = Ipv4_packet.Marshal.pseudoheader
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~src
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~dst
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~proto
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(payload_len + 8) in
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let packet = Cstruct.concat [
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Ipv4_packet.Marshal.make_cstruct ~payload_len:(payload_len + 8) ipv4_header;
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Udp_packet.Marshal.make_cstruct ~pseudoheader ~payload
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{ src_port = 42; dst_port = 42 };
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payload] in
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let (_ipv4_header', transport_packet) = unwrap_ipv4 packet in
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Alcotest.(check bool) "UDP packets with zero checksums pass verification"
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true @@ verify_ipv4_udp ~ipv4_header ~transport_packet;
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Cstruct.set_char transport_packet (Cstruct.length transport_packet - 1) '\000';
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Alcotest.(check bool) "Corrupted UDP packets with zero checksum fail verification"
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false @@ verify_ipv4_udp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let tcp_ipv4_correct_positive () =
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let buf = Cstruct.of_string example_ipv4_tcp in
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let (ipv4_header, transport_packet) = unwrap_ipv4 buf in
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Alcotest.(check bool) "for a correct TCP checksum, return true"
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true @@ verify_ipv4_tcp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let tcp_ipv4_correct_negative () =
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let buf = Cstruct.of_string example_ipv4_tcp in
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Cstruct.BE.set_uint32 buf ((Cstruct.length buf) - 4) 0x1234l;
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let (ipv4_header, transport_packet) = unwrap_ipv4 buf in
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Alcotest.(check bool) "mutating a TCP packet w/o fixing checksum causes verification to fail"
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false @@ verify_ipv4_tcp ~ipv4_header ~transport_packet;
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Lwt.return_unit
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let suite =
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[
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"correct UDP IPV4 checksums are recognized", `Quick, udp_ipv4_correct_positive;
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"incorrect UDP IPV4 checksums are recognized", `Quick, udp_ipv4_correct_negative;
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"0x00 UDP checksum is valid", `Quick, udp_ipv4_allows_zero;
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"correct but zero UDP IPV4 checksums are recognized", `Quick, udp_ipv4_zero_checksum;
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"correct TCP IPV4 checksums are recognized", `Quick, tcp_ipv4_correct_positive;
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"incorrect TCP IPV4 checksums are recognized", `Quick, tcp_ipv4_correct_negative;
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]
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