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Fix bug in packet parsing and ip_to_socket

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This commit is contained in:
Jeremy Wall 2021-01-14 19:24:14 -05:00
parent 89f866f4c0
commit 07d8ee676a
2 changed files with 94 additions and 15 deletions
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107
src/packet.rs
View File

@ -25,20 +25,21 @@ fn sum_big_endian_words(bs: &[u8]) -> u32 {
let len = bs.len();
let mut data = &bs[..];
let mut sum = 032;
// We need to stop when we have less than 2 bytes left.
let mut sum = 0u32;
// Iterate by word which is two bytes.
while data.len() >= 2 {
sum += BigEndian::read_u16(&data[0..2]) as u32;
// remove the first two now that we've already summed them
// remove the first two bytes now that we've already summed them
data = &data[2..];
}
if len % 2 != 0 { // If odd then checksum the last byte
sum += (bs[len - 1] as u32) << 8;
if (len % 2) != 0 { // If odd then checksum the last byte
sum += (data[0] as u32) << 8;
}
return sum;
}
#[derive(Debug)]
pub enum Icmpv6Message {
// NOTE(JWALL): All of the below integers should be parsed as big endian on the
// wire.
@ -112,6 +113,7 @@ impl Icmpv6Message {
}
}
#[derive(Debug)]
pub struct Icmpv6Packet {
// NOTE(JWALL): All of the below integers should be parsed as big endian on the
// wire.
@ -135,8 +137,8 @@ impl Icmpv6Packet {
if bytes.len() < 8 {
return Err(PacketParseError::PacketTooSmall(bytes.len()));
}
let (typ, code, checksum) = (bytes[0], bytes[1], BigEndian::read_u16(&bytes[2..3]));
let next_field = BigEndian::read_u32(&bytes[4..7]);
let (typ, code, checksum) = (bytes[0], bytes[1], BigEndian::read_u16(&bytes[2..4]));
let next_field = BigEndian::read_u32(&bytes[4..8]);
let payload = bytes[8..].to_owned();
let message = match typ {
1 => Unreachable{
@ -160,13 +162,13 @@ impl Icmpv6Packet {
payload: payload,
},
128 => EchoRequest{
identifier: BigEndian::read_u16(&bytes[4..5]),
sequence: BigEndian::read_u16(&bytes[6..7]),
identifier: BigEndian::read_u16(&bytes[4..6]),
sequence: BigEndian::read_u16(&bytes[6..8]),
payload: payload,
},
129 => EchoReply{
identifier: BigEndian::read_u16(&bytes[4..5]),
sequence: BigEndian::read_u16(&bytes[6..7]),
identifier: BigEndian::read_u16(&bytes[4..6]),
sequence: BigEndian::read_u16(&bytes[6..8]),
payload: payload,
},
_ => return Err(PacketParseError::UnrecognizedICMPType),
@ -205,13 +207,13 @@ impl Icmpv6Packet {
sum += ipv6_sum_words(dest);
// according to rfc4443: https://tools.ietf.org/html/rfc4443#section-2.3
// the ip next header value is 58
sum += 58u32;
sum += 58;
// Then sum the len of the message bytes and then the message bytes starting
// with the message type field and with the checksum field set to 0.
let bytes = self.get_bytes(false);
let len = bytes.len();
sum += len as u32;
// Then append the message bytes as a byte buffer starting with the message
// type field with the checksum field set to 0.
sum += sum_big_endian_words(&bytes);
// handle the carry
@ -342,3 +344,80 @@ impl From<Icmpv6PacketBuildError> for std::io::Error {
std::io::Error::new(std::io::ErrorKind::Other, format!("{}", err))
}
}
#[cfg(test)]
mod checksum_tests {
use super::*;
#[test]
fn echo_packet_parse_test() {
// NOTE(jwall): I am shamelessly ripping ff the cases for this from libpnet
// The equivalent of your typical ping -6 ::1%lo
let lo = &Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1);
let mut data = vec![
0x80, // Icmpv6 Type
0x00, // Code
0xff, 0xff, // Checksum
0x00, 0x00, // Id
0x00, 0x01, // Sequence
// 56 bytes of "random" data
0x20, 0x20, 0x75, 0x73, 0x74, 0x20, 0x61, 0x20,
0x66, 0x6c, 0x65, 0x73, 0x68, 0x20, 0x77, 0x6f,
0x75, 0x6e, 0x64, 0x20, 0x20, 0x74, 0x69, 0x73,
0x20, 0x62, 0x75, 0x74, 0x20, 0x61, 0x20, 0x73,
0x63, 0x72, 0x61, 0x74, 0x63, 0x68, 0x20, 0x20,
0x6b, 0x6e, 0x69, 0x67, 0x68, 0x74, 0x73, 0x20,
0x6f, 0x66, 0x20, 0x6e, 0x69, 0x20, 0x20, 0x20
];
let pkt = Icmpv6Packet::parse(&data).unwrap();
assert_eq!(pkt.typ, 128);
assert_eq!(pkt.code, 0x00);
if let EchoRequest{
identifier,
sequence,
payload,
}= &pkt.message {
assert_eq!(*identifier, 0);
assert_eq!(*sequence, 1);
assert_eq!(payload, &[
0x20, 0x20, 0x75, 0x73, 0x74, 0x20, 0x61, 0x20,
0x66, 0x6c, 0x65, 0x73, 0x68, 0x20, 0x77, 0x6f,
0x75, 0x6e, 0x64, 0x20, 0x20, 0x74, 0x69, 0x73,
0x20, 0x62, 0x75, 0x74, 0x20, 0x61, 0x20, 0x73,
0x63, 0x72, 0x61, 0x74, 0x63, 0x68, 0x20, 0x20,
0x6b, 0x6e, 0x69, 0x67, 0x68, 0x74, 0x73, 0x20,
0x6f, 0x66, 0x20, 0x6e, 0x69, 0x20, 0x20, 0x20
]);
} else {
assert!(false, "Packet did not parse as an EchoRequest {:?}", pkt.message);
}
assert_eq!(pkt.get_bytes(true), data);
assert_eq!(pkt.calculate_checksum(lo, lo), 0x1d2e);
// Check echo response as well
data[0] = 0x81;
let pkt = Icmpv6Packet::parse(&data).unwrap();
assert_eq!(pkt.typ, 129);
assert_eq!(pkt.code, 0);
if let EchoReply{
identifier,
sequence,
payload,
}= &pkt.message {
assert_eq!(*identifier, 0);
assert_eq!(*sequence, 1);
assert_eq!(payload, &[
0x20, 0x20, 0x75, 0x73, 0x74, 0x20, 0x61, 0x20,
0x66, 0x6c, 0x65, 0x73, 0x68, 0x20, 0x77, 0x6f,
0x75, 0x6e, 0x64, 0x20, 0x20, 0x74, 0x69, 0x73,
0x20, 0x62, 0x75, 0x74, 0x20, 0x61, 0x20, 0x73,
0x63, 0x72, 0x61, 0x74, 0x63, 0x68, 0x20, 0x20,
0x6b, 0x6e, 0x69, 0x67, 0x68, 0x74, 0x73, 0x20,
0x6f, 0x66, 0x20, 0x6e, 0x69, 0x20, 0x20, 0x20
]);
} else {
assert!(false, "Packet did not parse as an EchoReply {:?}", pkt.message);
}
assert_eq!(pkt.calculate_checksum(lo, lo), 0x1c2e);
}
}

2
src/socket.rs
View File

@ -20,7 +20,7 @@ use socket2::{Socket, Domain, Type, Protocol};
use crate::packet::Icmpv6Packet;
fn ip_to_socket(ip: &IpAddr) -> SocketAddr {
format!("{}:0", ip).parse::<SocketAddr>().unwrap()
SocketAddr::new(*ip, 0)
}
pub struct Opts {