329 lines
12 KiB
Rust
329 lines
12 KiB
Rust
use crate::dhcp_snooper::Lease;
|
|
use crate::proxy::flows::{FlowDirection, FlowMatch};
|
|
use crate::proxy::udp_packet_helper::UdpPacketHelper;
|
|
use crate::proxy::{Direction, PolicyDecision, Proxy};
|
|
use anyhow::Context;
|
|
use anyhow::Result;
|
|
use smoltcp::phy::ChecksumCapabilities;
|
|
use smoltcp::wire::{
|
|
ArpOperation, ArpPacket, ArpRepr, EthernetFrame, EthernetProtocol, IpProtocol, Ipv4Address,
|
|
Ipv4Packet, Ipv4Repr, UdpPacket,
|
|
};
|
|
|
|
const IPV4_HEADER_LEN_WITHOUT_OPTIONS: u8 = 20;
|
|
|
|
impl Proxy<'_> {
|
|
pub(crate) fn process_frame_from_vm(&mut self, frame: EthernetFrame<&[u8]>) -> Result<()> {
|
|
if self.allowed_from_vm(&frame).is_none() {
|
|
// Block packet by not forwarding it to the host
|
|
return Ok(());
|
|
}
|
|
|
|
self.host
|
|
.write(frame.as_ref())
|
|
.map(|_| ())
|
|
.context("failed to write to the host")
|
|
}
|
|
|
|
fn allowed_from_vm(&mut self, frame: &EthernetFrame<&[u8]>) -> Option<()> {
|
|
if frame.src_addr() != self.vm_mac_address {
|
|
return None;
|
|
}
|
|
|
|
match frame.ethertype() {
|
|
EthernetProtocol::Arp => {
|
|
let arp_pkt = ArpPacket::new_checked(frame.payload()).ok()?;
|
|
self.allowed_from_vm_arp(arp_pkt)
|
|
}
|
|
EthernetProtocol::Ipv4 => {
|
|
let ipv4_pkt = Ipv4Packet::new_unchecked(frame.payload());
|
|
Ipv4Repr::parse(&ipv4_pkt, &ChecksumCapabilities::ignored()).ok()?;
|
|
|
|
// Reject IPv4 options because source routing could bypass destination-based policy
|
|
if ipv4_pkt.header_len() != IPV4_HEADER_LEN_WITHOUT_OPTIONS {
|
|
return None;
|
|
}
|
|
|
|
self.allowed_from_vm_ipv4(ipv4_pkt)
|
|
}
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
fn allowed_from_vm_arp(&self, arp_pkt: ArpPacket<&[u8]>) -> Option<()> {
|
|
vm_arp_allowed(arp_pkt, self.vm_mac_address, self.dhcp_snooper.lease())
|
|
}
|
|
|
|
pub(crate) fn allowed_from_vm_ipv4(&mut self, ipv4_pkt: Ipv4Packet<&[u8]>) -> Option<()> {
|
|
// Is this packet coming from VM's IP address that we've learned from DHCP snooping?
|
|
if let Some(lease) = &self.dhcp_snooper.lease()
|
|
&& lease.is_valid_for(ipv4_pkt.src_addr())
|
|
{
|
|
// Unicast DHCP renewal is required to maintain the VM's lease
|
|
// and must bypass user-specified rules
|
|
if is_allowed_dhcp_request(&ipv4_pkt, Some(self.host.gateway_ip)) {
|
|
return Some(());
|
|
}
|
|
|
|
// Consult the flow table before evaluating outbound policy
|
|
// so established flows are not treated as new traffic
|
|
let pending = match self
|
|
.flows
|
|
.as_mut()
|
|
.map(|flows| flows.inspect(&ipv4_pkt, FlowDirection::FromVm))
|
|
.unwrap_or(FlowMatch::Untracked)
|
|
{
|
|
FlowMatch::Allowed => return Some(()),
|
|
FlowMatch::Denied => return None,
|
|
FlowMatch::Candidate(pending) => Some(pending),
|
|
FlowMatch::Untracked => None,
|
|
};
|
|
|
|
// The flow is either pending or untracked, evaluate it against outbound policy
|
|
let dst_addr = ipv4_pkt.dst_addr();
|
|
|
|
match self.rules.policy_decision(dst_addr, Direction::Out) {
|
|
// Return traffic was handled above; enforce explicit outbound blocks here
|
|
Some(PolicyDecision::Block) => return None,
|
|
|
|
// Track statelessly allowed traffic only when needed so its reply is not
|
|
// treated as a new inbound flow
|
|
Some(PolicyDecision::AllowStateless) => {
|
|
return self.admit_with_tracking_if_stateful(pending, dst_addr, Direction::In);
|
|
}
|
|
|
|
// Untracked packets cannot satisfy stateful policy
|
|
Some(PolicyDecision::AllowStateful) => return self.admit_with_tracking(pending?),
|
|
|
|
// No outbound rule matched; apply the built-in fallbacks below
|
|
None => {}
|
|
}
|
|
|
|
// When no user-specified rules matched, simply allow all global traffic
|
|
if ip_network::IpNetwork::from(dst_addr).is_global() {
|
|
return self.admit_with_tracking_if_trackable(pending);
|
|
}
|
|
|
|
// Additionally, allow communication with the host,
|
|
// otherwise things like SSH to a VM won't work
|
|
if dst_addr == self.host.gateway_ip {
|
|
return self.admit_with_tracking_if_trackable(pending);
|
|
}
|
|
|
|
// Additionally, allow DNS requests to DNS-servers
|
|
// provided to a VM by the host's DHCP server
|
|
if ipv4_pkt.next_header() == IpProtocol::Udp {
|
|
let udp_pkt = UdpPacket::new_checked(ipv4_pkt.payload()).ok()?;
|
|
|
|
if udp_pkt.is_dns_request() && self.dhcp_snooper.valid_dns_target(&dst_addr) {
|
|
return self.admit_with_tracking_if_trackable(pending);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Allow outgoing DHCP requests to the bootpd(8) broadcast address,
|
|
// otherwise DHCP snooper will never be populated
|
|
if is_allowed_dhcp_request(&ipv4_pkt, None) {
|
|
return Some(());
|
|
}
|
|
|
|
None
|
|
}
|
|
}
|
|
|
|
fn is_allowed_dhcp_request(
|
|
ipv4_pkt: &Ipv4Packet<&[u8]>,
|
|
unicast_target: Option<Ipv4Address>,
|
|
) -> bool {
|
|
let dst_addr = ipv4_pkt.dst_addr();
|
|
|
|
// Keep the common path cheap and inspect UDP only for a permitted DHCP target
|
|
if !dst_addr.is_broadcast() && unicast_target != Some(dst_addr) {
|
|
return false;
|
|
}
|
|
|
|
if ipv4_pkt.next_header() != IpProtocol::Udp {
|
|
return false;
|
|
}
|
|
|
|
let Ok(udp_pkt) = UdpPacket::new_checked(ipv4_pkt.payload()) else {
|
|
return false;
|
|
};
|
|
|
|
udp_pkt.is_dhcp_request()
|
|
}
|
|
|
|
fn vm_arp_allowed(
|
|
arp_pkt: ArpPacket<&[u8]>,
|
|
vm_mac_address: smoltcp::wire::EthernetAddress,
|
|
lease: &Option<Lease>,
|
|
) -> Option<()> {
|
|
let (operation, source_hardware_addr, source_protocol_addr) =
|
|
match ArpRepr::parse(&arp_pkt).ok()? {
|
|
ArpRepr::EthernetIpv4 {
|
|
operation,
|
|
source_hardware_addr,
|
|
source_protocol_addr,
|
|
..
|
|
} => (operation, source_hardware_addr, source_protocol_addr),
|
|
_ => return None,
|
|
};
|
|
|
|
if !matches!(operation, ArpOperation::Request | ArpOperation::Reply) {
|
|
return None;
|
|
}
|
|
|
|
if source_hardware_addr != vm_mac_address {
|
|
return None;
|
|
}
|
|
|
|
if let Some(lease) = lease {
|
|
if lease.is_valid_for(source_protocol_addr) {
|
|
return Some(());
|
|
}
|
|
} else if source_protocol_addr.is_unspecified() {
|
|
return Some(());
|
|
}
|
|
|
|
None
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use crate::dhcp_snooper::Lease;
|
|
use smoltcp::wire::{
|
|
ArpHardware, ArpOperation, ArpPacket, EthernetAddress, EthernetProtocol, IpProtocol,
|
|
Ipv4Address, Ipv4Packet, UdpPacket,
|
|
};
|
|
use std::collections::HashSet;
|
|
use std::time::Duration;
|
|
|
|
#[test]
|
|
fn test_allowed_dhcp_request_targets() {
|
|
let gateway = Ipv4Address::new(192, 168, 64, 1);
|
|
let other = Ipv4Address::new(192, 168, 64, 2);
|
|
|
|
assert!(allowed_dhcp_request(Ipv4Address::BROADCAST, None));
|
|
assert!(allowed_dhcp_request(gateway, Some(gateway)));
|
|
assert!(!allowed_dhcp_request(gateway, None));
|
|
assert!(!allowed_dhcp_request(other, Some(gateway)));
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_allows_unspecified_request_without_lease() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_some());
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_allows_reply_for_leased_ip() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let lease_ip = Ipv4Address::new(192, 168, 0, 2);
|
|
let lease = Some(Lease::new(
|
|
lease_ip,
|
|
Duration::from_secs(600),
|
|
HashSet::new(),
|
|
));
|
|
let buf = arp_packet(
|
|
vm_mac_address.0,
|
|
lease_ip.octets(),
|
|
ArpOperation::Reply,
|
|
6,
|
|
4,
|
|
);
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &lease).is_some());
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_rejects_unknown_operation() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let buf = arp_packet(
|
|
vm_mac_address.0,
|
|
[0, 0, 0, 0],
|
|
ArpOperation::Unknown(3),
|
|
6,
|
|
4,
|
|
);
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_rejects_non_ethernet_hardware_type() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let mut buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
|
|
let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
|
|
arp_pkt.set_hardware_type(ArpHardware::Unknown(2));
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_rejects_non_ipv4_protocol_type() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let mut buf = arp_packet(vm_mac_address.0, [0, 0, 0, 0], ArpOperation::Request, 6, 4);
|
|
let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
|
|
arp_pkt.set_protocol_type(EthernetProtocol::Ipv6);
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
|
|
}
|
|
|
|
#[test]
|
|
fn test_allowed_from_vm_arp_rejects_non_ipv4_protocol_length() {
|
|
let vm_mac_address = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
|
|
let buf = arp_packet(vm_mac_address.0, [0, 0, 0], ArpOperation::Request, 6, 3);
|
|
let arp_pkt = ArpPacket::new_checked(buf.as_slice()).unwrap();
|
|
|
|
assert!(super::vm_arp_allowed(arp_pkt, vm_mac_address, &None).is_none());
|
|
}
|
|
|
|
fn arp_packet(
|
|
source_hardware_addr: [u8; 6],
|
|
source_protocol_addr: impl AsRef<[u8]>,
|
|
operation: ArpOperation,
|
|
hardware_len: u8,
|
|
protocol_len: u8,
|
|
) -> Vec<u8> {
|
|
let source_protocol_addr = source_protocol_addr.as_ref();
|
|
let payload_len = 8 + 2 * (hardware_len as usize + protocol_len as usize);
|
|
let mut buf = vec![0; payload_len];
|
|
let mut arp_pkt = ArpPacket::new_unchecked(buf.as_mut_slice());
|
|
arp_pkt.set_hardware_type(ArpHardware::Ethernet);
|
|
arp_pkt.set_protocol_type(EthernetProtocol::Ipv4);
|
|
arp_pkt.set_hardware_len(hardware_len);
|
|
arp_pkt.set_protocol_len(protocol_len);
|
|
arp_pkt.set_operation(operation);
|
|
arp_pkt.set_source_hardware_addr(&source_hardware_addr[..hardware_len as usize]);
|
|
arp_pkt.set_source_protocol_addr(source_protocol_addr);
|
|
arp_pkt.set_target_hardware_addr(&[0; 6][..hardware_len as usize]);
|
|
arp_pkt.set_target_protocol_addr(&vec![0; protocol_len as usize]);
|
|
buf
|
|
}
|
|
|
|
fn allowed_dhcp_request(dst_addr: Ipv4Address, unicast_target: Option<Ipv4Address>) -> bool {
|
|
let mut buf = vec![0; 28];
|
|
let mut ipv4_pkt = Ipv4Packet::new_unchecked(buf.as_mut_slice());
|
|
ipv4_pkt.set_version(4);
|
|
ipv4_pkt.set_header_len(20);
|
|
ipv4_pkt.set_total_len(28);
|
|
ipv4_pkt.set_next_header(IpProtocol::Udp);
|
|
ipv4_pkt.set_dst_addr(dst_addr);
|
|
|
|
let mut udp_pkt = UdpPacket::new_unchecked(ipv4_pkt.payload_mut());
|
|
udp_pkt.set_src_port(68);
|
|
udp_pkt.set_dst_port(67);
|
|
udp_pkt.set_len(8);
|
|
|
|
let ipv4_pkt = Ipv4Packet::new_checked(buf.as_slice()).unwrap();
|
|
super::is_allowed_dhcp_request(&ipv4_pkt, unicast_target)
|
|
}
|
|
}
|