Files
RustyDHCP/tests/test_security_wire.rs
T

573 lines
22 KiB
Rust

//! DHCP security wire + gate composition, part 4.
//!
//! Covers security-relevant behavior NOT locked by `test_security.rs`,
//! `test_security_extra.rs`, `test_security_edge.rs`, or the RFC suites:
//!
//! - malformed Server ID on a Release is stripped by the decoder, so the
//! `for_this_server` gate fails closed and the lease survives (live)
//! - wrong (but well-formed) Server ID on Release likewise keeps the lease
//! - malformed Requested IP falls back to `ciaddr` per the example match
//! - framing is purely length-delimited: fake cookies, fake option headers
//! and END bytes inside option data never resync parsing; END bytes in
//! `chaddr` don't confuse framing either
//! - oversized inputs stay bounded (4096-byte datagram decodes, re-encodes
//! capped); empty PRL still yields the required defaults live
//! - critical-address Requests (server IP, broadcast, 0.0.0.0) NAK cleanly
//! with no table insert; max `secs`/`hops` decode exactly
//!
//! `*_quirk` tests lock currently-unsafe behavior for review, not approval.
use dhcp4r::options::*;
use dhcp4r::packet::*;
use dhcp4r::server;
use std::collections::HashMap;
use std::net::{Ipv4Addr, UdpSocket};
use std::ops::Add;
use std::time::{Duration, Instant};
// ---------------------------------------------------------------------------
// helpers (same patterns as test_security.rs)
// ---------------------------------------------------------------------------
fn unwrap_packet(r: Result<Packet, CustomErr<&[u8]>>) -> Packet {
match r {
Ok(p) => p,
Err(_) => panic!("expected Ok Packet"),
}
}
#[allow(clippy::too_many_arguments)]
fn make_raw(
op: u8,
hlen: u8,
hops: u8,
xid: u32,
secs: u16,
flags: [u8; 2],
ci: [u8; 4],
yi: [u8; 4],
si: [u8; 4],
gi: [u8; 4],
chaddr: [u8; 6],
opts_after_cookie: Vec<u8>,
) -> Vec<u8> {
let mut v = vec![0u8; 236];
v[0] = op;
v[1] = 1;
v[2] = hlen;
v[3] = hops;
v[4..8].copy_from_slice(&xid.to_be_bytes());
v[8..10].copy_from_slice(&secs.to_be_bytes());
v[10] = flags[0];
v[11] = flags[1];
v[12..16].copy_from_slice(&ci);
v[16..20].copy_from_slice(&yi);
v[20..24].copy_from_slice(&si);
v[24..28].copy_from_slice(&gi);
v[28..34].copy_from_slice(&chaddr);
v.extend_from_slice(&[99, 130, 83, 99]);
v.extend_from_slice(&opts_after_cookie);
v
}
// Replica of examples/server.rs lease state (bodies identical; only the
// methods needed here are included).
const IP_START: [u8; 4] = [192, 168, 2, 2];
const IP_START_NUM: u32 = u32::from_be_bytes(IP_START);
const LEASE_NUM: u32 = 252;
const LEASE_DURATION_SECS: u32 = 86400;
struct Replica {
leases: HashMap<Ipv4Addr, ([u8; 6], Option<Instant>)>,
#[allow(dead_code)]
last_lease: u32,
lease_duration: Duration,
}
impl Replica {
fn new() -> Self {
Self {
leases: HashMap::new(),
last_lease: 0,
lease_duration: Duration::new(LEASE_DURATION_SECS as u64, 0),
}
}
fn available(&self, chaddr: &[u8; 6], addr: &Ipv4Addr) -> bool {
let pos: u32 = (*addr).into();
pos >= IP_START_NUM
&& pos < IP_START_NUM + LEASE_NUM
&& match self.leases.get(addr) {
Some((mac, expiry)) => {
*mac == *chaddr || expiry.map_or(true, |exp| Instant::now().gt(&exp))
}
None => true,
}
}
fn current_lease(&self, chaddr: &[u8; 6]) -> Option<Ipv4Addr> {
for (i, v) in &self.leases {
if v.0 == *chaddr {
return Some(*i);
}
}
None
}
fn request(
&mut self,
chaddr: &[u8; 6],
requested: Option<Ipv4Addr>,
ciaddr: Ipv4Addr,
_for_this: bool,
) -> Result<Ipv4Addr, &'static str> {
let req_ip = requested.unwrap_or(ciaddr);
if let Some(ip) = self.current_lease(chaddr) {
return Ok(ip);
}
if !self.available(chaddr, &req_ip) {
return Err("Requested IP not available");
}
self.leases.insert(
req_ip,
(chaddr.to_owned(), Some(Instant::now().add(self.lease_duration))),
);
Ok(req_ip)
}
}
// Example-like handler: Discover->Offer, Request->Ack, Release|Decline gated,
// everything else ignored. Mirrors examples/server.rs match arms.
struct ExampleLike {
leases: HashMap<Ipv4Addr, ([u8; 6], Option<Instant>)>,
last_lease: u32,
lease_duration: Duration,
#[allow(dead_code)]
server_ip: Ipv4Addr,
}
impl ExampleLike {
fn new(server_ip: Ipv4Addr) -> Self {
Self {
leases: HashMap::new(),
last_lease: 0,
lease_duration: Duration::new(LEASE_DURATION_SECS as u64, 0),
server_ip,
}
}
fn available(&self, chaddr: &[u8; 6], addr: &Ipv4Addr) -> bool {
let pos: u32 = (*addr).into();
pos >= IP_START_NUM
&& pos < IP_START_NUM + LEASE_NUM
&& match self.leases.get(addr) {
Some((mac, expiry)) => {
*mac == *chaddr || expiry.map_or(true, |exp| Instant::now().gt(&exp))
}
None => true,
}
}
fn current_lease(&self, chaddr: &[u8; 6]) -> Option<Ipv4Addr> {
for (i, v) in &self.leases {
if v.0 == *chaddr {
return Some(*i);
}
}
None
}
}
impl server::Handler for ExampleLike {
fn handle_request(&mut self, server: &server::Server, in_packet: Packet) {
match in_packet.message_type() {
Ok(MessageType::Discover) => {
if let Some(ip) = self.current_lease(&in_packet.chaddr) {
let _ = server.reply(
MessageType::Offer,
vec![DhcpOption::IpAddressLeaseTime(LEASE_DURATION_SECS)],
ip,
in_packet,
);
return;
}
for _ in 0..LEASE_NUM {
self.last_lease = (self.last_lease + 1) % LEASE_NUM;
let cand: Ipv4Addr = (IP_START_NUM + self.last_lease).into();
if self.available(&in_packet.chaddr, &cand) {
let _ = server.reply(
MessageType::Offer,
vec![DhcpOption::IpAddressLeaseTime(LEASE_DURATION_SECS)],
cand,
in_packet,
);
break;
}
}
}
Ok(MessageType::Request) => {
// NOTE: mirrors the example — the for_this_server gate is
// commented out upstream, so Requests are honored regardless.
let req_ip = match in_packet.option(REQUESTED_IP_ADDRESS) {
Some(DhcpOption::RequestedIpAddress(x)) => *x,
_ => in_packet.ciaddr,
};
if let Some(ip) = self.current_lease(&in_packet.chaddr) {
let _ = server.reply(
MessageType::Ack,
vec![DhcpOption::IpAddressLeaseTime(LEASE_DURATION_SECS)],
ip,
in_packet,
);
return;
}
if !self.available(&in_packet.chaddr, &req_ip) {
let _ = server.reply(
MessageType::Nak,
vec![DhcpOption::Message("Requested IP not available".to_string())],
Ipv4Addr::UNSPECIFIED,
in_packet,
);
return;
}
self.leases.insert(
req_ip,
(
in_packet.chaddr,
Some(Instant::now().add(self.lease_duration)),
),
);
let _ = server.reply(
MessageType::Ack,
vec![DhcpOption::IpAddressLeaseTime(LEASE_DURATION_SECS)],
req_ip,
in_packet,
);
}
Ok(MessageType::Release) | Ok(MessageType::Decline) => {
if !server.for_this_server(&in_packet) {
return;
}
if let Some(ip) = self.current_lease(&in_packet.chaddr) {
self.leases.remove(&ip);
}
}
_ => {}
}
}
}
fn serve_example_like() -> (std::net::SocketAddr, Ipv4Addr) {
let srv_sock = UdpSocket::bind("127.0.0.1:0").unwrap();
let srv_addr = srv_sock.local_addr().unwrap();
let server_ip = Ipv4Addr::new(192, 168, 2, 1);
std::thread::spawn(move || {
let _ = server::Server::serve(
srv_sock,
server_ip,
Ipv4Addr::new(192, 168, 2, 255),
ExampleLike::new(server_ip),
);
});
std::thread::sleep(Duration::from_millis(100));
(srv_addr, server_ip)
}
fn send_recv(
client: &UdpSocket,
srv_addr: &std::net::SocketAddr,
p: &Packet,
buf: &mut [u8; 1500],
rbuf: &mut [u8; 1500],
) -> Packet {
client.send_to(&p.encode(buf).to_vec(), srv_addr).unwrap();
let (n, _) = client.recv_from(rbuf).expect("expected reply");
unwrap_packet(Packet::from(&rbuf[..n]))
}
// ===========================================================================
// A. Malformed vs wrong Server ID on Release: both fail closed (live)
// ===========================================================================
/// A Release whose Server Identifier is truncated on the wire (`len` 3)
/// decodes to *no* Server ID at all, so `for_this_server` is false and the
/// lease survives. Wire-levelzott malformation fails closed for Release.
/// Locked live.
#[test]
fn sec3_truncated_server_id_release_keeps_lease_live() {
let (srv_addr, server_ip) = serve_example_like();
let client = UdpSocket::bind("127.0.0.1:0").unwrap();
client
.set_read_timeout(Some(Duration::from_secs(2)))
.unwrap();
let mut buf = [0u8; 1500];
let mut rbuf = [0u8; 1500];
let victim = [0x31; 6];
// occupy .61 with a well-formed Request
let req = Packet {
reply: false, hops: 0, xid: 0xF001, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: victim,
options: vec![
DhcpOption::DhcpMessageType(MessageType::Request),
DhcpOption::ServerIdentifier(server_ip),
DhcpOption::RequestedIpAddress(Ipv4Addr::new(192, 168, 2, 61)),
],
};
assert_eq!(
send_recv(&client, &srv_addr, &req, &mut buf, &mut rbuf).message_type(),
Ok(MessageType::Ack)
);
// Release with truncated Server ID [54,3,10,20,30]: stripped on decode
let raw = make_raw(
1, 6, 0, 0xF002, 0, [0, 0],
[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
victim, vec![53, 1, 7, 54, 3, 10, 20, 30, 255],
);
// sanity: decoder really drops the identifier (fail-closed precondition)
let decoded = unwrap_packet(Packet::from(&raw));
assert!(decoded.option(SERVER_IDENTIFIER).is_none());
client.send_to(&raw, srv_addr).unwrap();
// lease kept: Discover still offers .61
let disc = Packet {
reply: false, hops: 0, xid: 0xF003, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: victim,
options: vec![DhcpOption::DhcpMessageType(MessageType::Discover)],
};
let offer = send_recv(&client, &srv_addr, &disc, &mut buf, &mut rbuf);
assert_eq!(offer.message_type(), Ok(MessageType::Offer));
assert_eq!(offer.yiaddr, Ipv4Addr::new(192, 168, 2, 61), "lease kept");
}
/// A well-formed Release naming the WRONG server is likewise ignored live —
/// the lease survives and Discover still offers it. Complements the
/// missing-ID case with a wrong-value case.
#[test]
fn sec3_wrong_server_id_release_keeps_lease_live() {
let (srv_addr, _) = serve_example_like();
let client = UdpSocket::bind("127.0.0.1:0").unwrap();
client
.set_read_timeout(Some(Duration::from_secs(2)))
.unwrap();
let mut buf = [0u8; 1500];
let mut rbuf = [0u8; 1500];
let victim = [0x32; 6];
let req = Packet {
reply: false, hops: 0, xid: 0xF010, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: victim,
options: vec![
DhcpOption::DhcpMessageType(MessageType::Request),
DhcpOption::ServerIdentifier(Ipv4Addr::new(192, 168, 2, 1)),
DhcpOption::RequestedIpAddress(Ipv4Addr::new(192, 168, 2, 62)),
],
};
assert_eq!(
send_recv(&client, &srv_addr, &req, &mut buf, &mut rbuf).message_type(),
Ok(MessageType::Ack)
);
// Release naming a different server: ignored
let rel = Packet {
reply: false, hops: 0, xid: 0xF011, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: victim,
options: vec![
DhcpOption::DhcpMessageType(MessageType::Release),
DhcpOption::ServerIdentifier(Ipv4Addr::new(10, 99, 99, 99)),
],
};
client.send_to(&rel.encode(&mut buf).to_vec(), srv_addr).unwrap();
let disc = Packet {
reply: false, hops: 0, xid: 0xF012, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: victim,
options: vec![DhcpOption::DhcpMessageType(MessageType::Discover)],
};
let offer = send_recv(&client, &srv_addr, &disc, &mut buf, &mut rbuf);
assert_eq!(offer.yiaddr, Ipv4Addr::new(192, 168, 2, 62), "lease kept");
}
// ===========================================================================
// B. Malformed Requested IP falls back to ciaddr (no crash, no bypass)
// ===========================================================================
/// A Requested-IP option truncated to 3 bytes is stripped by the decoder, so
/// the example `match option(50) / _ => ciaddr` falls back to `ciaddr`.
/// The fallback address (.71) is Acked and inserted — never the truncated
/// bytes, never a panic. Locked.
#[test]
fn sec3_malformed_requested_ip_falls_back_to_ciaddr() {
let raw = make_raw(
1, 6, 0, 0xF020, 0, [0, 0],
[192, 168, 2, 71], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
[0x33; 6],
vec![53, 1, 3, 50, 3, 10, 0, 0, 255],
);
let p = unwrap_packet(Packet::from(&raw));
assert_eq!(p.message_type(), Ok(MessageType::Request));
assert!(p.option(REQUESTED_IP_ADDRESS).is_none(), "truncated option stripped");
// byte-for-byte example selection: RequestedIp else ciaddr
let req_ip = match p.option(REQUESTED_IP_ADDRESS) {
Some(DhcpOption::RequestedIpAddress(x)) => *x,
_ => p.ciaddr,
};
assert_eq!(req_ip, Ipv4Addr::new(192, 168, 2, 71), "falls back to ciaddr");
let mut s = Replica::new();
assert_eq!(
s.request(&[0x33; 6], p.option(REQUESTED_IP_ADDRESS).and_then(|o| match o {
DhcpOption::RequestedIpAddress(x) => Some(*x),
_ => None,
}), p.ciaddr, true),
Ok(Ipv4Addr::new(192, 168, 2, 71))
);
assert!(s.leases.contains_key(&Ipv4Addr::new(192, 168, 2, 71)));
}
// ===========================================================================
// C. Framing is purely length-delimited (no sentinel scanning)
// ===========================================================================
/// Fake magic cookie, fake option header and END *byte values* inside option
/// data never resync parsing: decode consumes exactly `len` bytes, so the
/// real Offer option after them still decodes and `message_type()` finds it.
#[test]
fn sec3_embedded_cookie_and_end_bytes_ignored_in_data() {
let mut opts = vec![200, 6, 99, 130, 83, 99, 255, 53]; // data: cookie+END+53
opts.extend_from_slice(&[53, 1, 2, 255]); // real Offer
let raw = make_raw(
1, 6, 0, 0xF030, 0, [0, 0],
[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
[0x34; 6], opts,
);
let p = unwrap_packet(Packet::from(&raw));
assert_eq!(p.options.len(), 2);
match &p.options[0] {
DhcpOption::Unrecognized(r) => {
assert_eq!(r.code, 200);
assert_eq!(r.data, vec![99, 130, 83, 99, 255, 53]);
}
_ => panic!("first option must be the Unrecognized carrier"),
}
assert_eq!(p.message_type(), Ok(MessageType::Offer));
}
/// END bytes (255) in `chaddr` don't confuse framing: the 6-byte field is
/// positional, so `chaddr == [255; 6]` round-trips exactly with options intact.
#[test]
fn sec3_end_bytes_in_chaddr_no_confusion() {
let raw = make_raw(
1, 6, 0, 0xF031, 0, [0, 0],
[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
[255; 6],
vec![53, 1, 1, 255],
);
let p = unwrap_packet(Packet::from(&raw));
assert_eq!(p.chaddr, [255; 6]);
assert_eq!(p.message_type(), Ok(MessageType::Discover));
}
// ===========================================================================
// D. Oversized inputs stay bounded; empty PRL still yields defaults
// ===========================================================================
/// A 4096-byte datagram (past the 1500 MTU buffers) decodes with the option
/// Vec bounded by the input (~1285 entries, no amplification) and re-encodes
/// capped at 300 with Discover first. No panic at either size.
#[test]
fn sec3_4096_byte_datagram_decodes_bounded() {
let mut opts = vec![53, 1, 1];
for _ in 0..1284 {
opts.extend_from_slice(&[200, 1, 7]);
}
opts.push(255);
let raw = make_raw(
1, 6, 0, 0xF040, 0, [0, 0],
[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
[0x35; 6], opts,
);
assert_eq!(raw.len(), 4096);
let p = unwrap_packet(Packet::from(&raw));
assert_eq!(p.options.len(), 1285, "1 Discover + 1284 fillers");
let mut buf = [0u8; 1500];
let enc = p.encode(&mut buf).to_vec();
assert!(enc.len() <= 300, "re-encode capped");
let q = unwrap_packet(Packet::from(&enc));
assert_eq!(q.message_type(), Ok(MessageType::Discover));
assert_eq!(q.options.len(), 19, "Discover + 18 fillers");
}
/// Empty PRL (`len` 0) is valid and live-filters to the required defaults:
/// a Request asking for nothing extra still gets `[53,54,51]`. An attacker
/// cannot use an empty list to strip Server ID / lease time. Locked live.
#[test]
fn sec3_empty_prl_returns_defaults_live() {
let (srv_addr, server_ip) = serve_example_like();
let client = UdpSocket::bind("127.0.0.1:0").unwrap();
client
.set_read_timeout(Some(Duration::from_secs(2)))
.unwrap();
let mut buf = [0u8; 1500];
let mut rbuf = [0u8; 1500];
let req = Packet {
reply: false, hops: 0, xid: 0xF041, secs: 0, broadcast: false,
ciaddr: Ipv4Addr::UNSPECIFIED, yiaddr: Ipv4Addr::UNSPECIFIED,
siaddr: Ipv4Addr::UNSPECIFIED, giaddr: Ipv4Addr::UNSPECIFIED,
chaddr: [0x36; 6],
options: vec![
DhcpOption::DhcpMessageType(MessageType::Request),
DhcpOption::ServerIdentifier(server_ip),
DhcpOption::RequestedIpAddress(Ipv4Addr::new(192, 168, 2, 72)),
DhcpOption::ParameterRequestList(vec![]),
],
};
client.send_to(&req.encode(&mut buf).to_vec(), srv_addr).unwrap();
let (n, _) = client.recv_from(&mut rbuf).expect("Ack");
let rep = unwrap_packet(Packet::from(&rbuf[..n]));
assert_eq!(rep.message_type(), Ok(MessageType::Ack));
assert_eq!(
rep.options.iter().map(|o| o.code()).collect::<Vec<u8>>(),
vec![53, 54, 51],
"empty PRL keeps required + defaults"
);
}
// ===========================================================================
// E. Critical-address Requests NAK cleanly; secs/hops extremes preserved
// ===========================================================================
/// Requests for the server's own IP, the subnet broadcast, and explicit
/// 0.0.0.0 all NAK with no table insert — critical identities can never be
/// handed out, and 0.0.0.0 never enters the map. Locked.
#[test]
fn sec3_critical_and_unspecified_requests_nak_without_insert() {
let mut s = Replica::new();
for ip in [
Ipv4Addr::new(192, 168, 2, 1), // server identity
Ipv4Addr::new(192, 168, 2, 255), // subnet broadcast
Ipv4Addr::new(0, 0, 0, 0), // unspecified
] {
assert!(
s.request(&[0x37; 6], Some(ip), Ipv4Addr::UNSPECIFIED, true).is_err(),
"must NAK {}",
ip
);
}
assert!(s.leases.is_empty(), "nothing critical/unspecified may be leased");
}
/// Max `secs` (0xFFFF) and `hops` 255 decode exactly — no clamping that could
/// desync retransmission/loop accounting between peers. Locked.
#[test]
fn sec3_secs_hops_max_preserved_on_decode() {
let raw = make_raw(
1, 6, 255, 0xF050, 0xFFFF, [0, 0],
[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
[0x38; 6],
vec![53, 1, 1, 255],
);
let p = unwrap_packet(Packet::from(&raw));
assert_eq!(p.secs, 0xFFFF);
assert_eq!(p.hops, 255);
}