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use crate::options::*;
use nom::bytes::complete::{tag, take};
use nom::multi::{many0, many_till};
use nom::number::complete::{be_u16, be_u32, be_u8};
use std::net::Ipv4Addr;
pub enum Err<I> {
NomError(nom::Err<(I, nom::error::ErrorKind)>),
NonUtf8String,
UnrecognizedMessageType,
InvalidHlen,
}
impl<I> nom::error::ParseError<I> for Err<I> {
fn from_error_kind(input: I, kind: nom::error::ErrorKind) -> Self {
Err::NomError(nom::Err::Error((input, kind)))
}
fn append(_input: I, _kind: nom::error::ErrorKind, other: Self) -> Self {
other
}
}
type IResult<I, O> = nom::IResult<I, O, Err<I>>;
pub struct Packet {
pub reply: bool,
pub hops: u8,
pub xid: u32,
pub secs: u16,
pub broadcast: bool,
pub ciaddr: Ipv4Addr,
pub yiaddr: Ipv4Addr,
pub siaddr: Ipv4Addr,
pub giaddr: Ipv4Addr,
pub chaddr: [u8; 6],
pub options: Vec<DhcpOption>,
}
fn decode_reply(input: &[u8]) -> IResult<&[u8], bool> {
let (input, reply) = take(1u8)(input)?;
Ok((
input,
match reply[0] {
BOOT_REPLY => true,
BOOT_REQUEST => false,
_ => {
false
}
},
))
}
fn decode_ipv4(p: &[u8]) -> IResult<&[u8], Ipv4Addr> {
let (input, addr) = take(4u8)(p)?;
Ok((input, Ipv4Addr::new(addr[0], addr[1], addr[2], addr[3])))
}
pub fn decode_option(input: &[u8]) -> IResult<&[u8], DhcpOption> {
let (input, code) = be_u8(input)?;
assert!(code != END);
let (input, len) = be_u8(input)?;
let (input, data) = take(len)(input)?;
let option = match code {
DHCP_MESSAGE_TYPE => DhcpOption::DhcpMessageType(match MessageType::from(be_u8(data)?.1) {
Ok(x) => x,
Err(_) => return Err(nom::Err::Error(Err::UnrecognizedMessageType)),
}),
SERVER_IDENTIFIER => DhcpOption::ServerIdentifier(decode_ipv4(data)?.1),
PARAMETER_REQUEST_LIST => DhcpOption::ParameterRequestList(data.to_vec()),
REQUESTED_IP_ADDRESS => DhcpOption::RequestedIpAddress(decode_ipv4(data)?.1),
HOST_NAME => DhcpOption::HostName(match std::str::from_utf8(data) {
Ok(s) => s.to_string(),
Err(_) => return Err(nom::Err::Error(Err::NonUtf8String)),
}),
ROUTER => DhcpOption::Router(many0(decode_ipv4)(data)?.1),
DOMAIN_NAME_SERVER => DhcpOption::DomainNameServer(many0(decode_ipv4)(data)?.1),
IP_ADDRESS_LEASE_TIME => DhcpOption::IpAddressLeaseTime(be_u32(data)?.1),
MESSAGE => DhcpOption::Message(match std::str::from_utf8(data) {
Ok(s) => s.to_string(),
Err(_) => return Err(nom::Err::Error(Err::NonUtf8String)),
}),
_ => DhcpOption::Unrecognized(RawDhcpOption {
code,
data: data.to_vec(),
}),
};
Ok((input, option))
}
fn decode(input: &[u8]) -> IResult<&[u8], Packet> {
let (options_input, input) = take(236u32)(input)?;
let (input, reply) = decode_reply(input)?;
let (input, _htype) = take(1u8)(input)?;
let (input, hlen) = be_u8(input)?;
let (input, hops) = be_u8(input)?;
let (input, xid) = be_u32(input)?;
let (input, secs) = be_u16(input)?;
let (input, flags) = be_u16(input)?;
let (input, ciaddr) = decode_ipv4(input)?;
let (input, yiaddr) = decode_ipv4(input)?;
let (input, siaddr) = decode_ipv4(input)?;
let (input, giaddr) = decode_ipv4(input)?;
if hlen != 6 {
return Err(nom::Err::Error(Err::InvalidHlen));
}
let (_, chaddr) = take(6u8)(input)?;
let input = options_input;
let (input, _) = tag(COOKIE)(input)?;
let (input, (options, _)) = many_till(decode_option, tag(&[END]))(input)?;
Ok((
input,
Packet {
reply,
hops,
secs,
broadcast: flags & 128 == 128,
ciaddr,
yiaddr,
siaddr,
giaddr,
options,
chaddr: [
chaddr[0], chaddr[1], chaddr[2], chaddr[3], chaddr[4], chaddr[5],
],
xid,
},
))
}
impl Packet {
pub fn from(input: &[u8]) -> Result<Packet, nom::Err<Err<&[u8]>>> {
Ok(decode(input)?.1)
}
pub fn option(&self, code: u8) -> Option<&DhcpOption> {
for option in &self.options {
if option.code() == code {
return Some(&option);
}
}
None
}
pub fn message_type(&self) -> Result<MessageType, String> {
match self.option(DHCP_MESSAGE_TYPE) {
Some(DhcpOption::DhcpMessageType(msgtype)) => Ok(*msgtype),
Some(option) => Err(format![
"Got wrong enum code {} for DHCP_MESSAGE_TYPE",
option.code()
]),
None => Err("Packet does not have MessageType option".to_string()),
}
}
pub fn encode<'c>(&'c self, p: &'c mut [u8]) -> &[u8] {
p[..12].clone_from_slice(&[
(if self.reply { BOOT_REPLY } else { BOOT_REQUEST }),
1,
6,
self.hops,
((self.xid >> 24) & 0xFF) as u8,
((self.xid >> 16) & 0xFF) as u8,
((self.xid >> 8) & 0xFF) as u8,
(self.xid & 0xFF) as u8,
(self.secs >> 8) as u8,
(self.secs & 255) as u8,
(if self.broadcast { 128 } else { 0 }),
0,
]);
p[12..16].clone_from_slice(&self.ciaddr.octets());
p[16..20].clone_from_slice(&self.yiaddr.octets());
p[20..24].clone_from_slice(&self.siaddr.octets());
p[24..28].clone_from_slice(&self.giaddr.octets());
p[28..34].clone_from_slice(&self.chaddr);
p[34..236].clone_from_slice(&[0; 202]);
p[236..240].clone_from_slice(&COOKIE);
let mut length: usize = 240;
for option in &self.options {
let option = option.to_raw();
p[length] = option.code;
p[length + 1] = option.data.len() as u8;
p[length + 2..length + 2 + option.data.len()].clone_from_slice(&option.data);
length += 2 + option.data.len();
}
p[length] = END;
length += 1;
if length < 272 {
p[length..272].clone_from_slice(&[PAD; 32][..272 - length]);
length = 272
}
&p[..length]
}
}
const COOKIE: [u8; 4] = [99, 130, 83, 99];
const BOOT_REQUEST: u8 = 1;
const BOOT_REPLY: u8 = 2;
const END: u8 = 255;
const PAD: u8 = 0;