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/*
* Copyright (C) 2015 Benjamin Fry <benjaminfry@me.com>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//! option record for passing protocol options between the client and server
use std::collections::HashMap;
#[cfg(feature = "serde-config")]
use serde::{Deserialize, Serialize};
use log::warn;
use crate::error::*;
use crate::serialize::binary::*;
#[cfg(feature = "dnssec")]
use crate::rr::dnssec::SupportedAlgorithms;
/// The OPT record type is used for ExtendedDNS records.
///
/// These allow for additional information to be associated with the DNS request that otherwise
/// would require changes to the DNS protocol.
///
/// [RFC 6891, EDNS(0) Extensions, April 2013](https://tools.ietf.org/html/rfc6891#section-6)
///
/// ```text
/// 6.1. OPT Record Definition
///
/// 6.1.1. Basic Elements
///
/// An OPT pseudo-RR (sometimes called a meta-RR) MAY be added to the
/// additional data section of a request.
///
/// The OPT RR has RR type 41.
///
/// If an OPT record is present in a received request, compliant
/// responders MUST include an OPT record in their respective responses.
///
/// An OPT record does not carry any DNS data. It is used only to
/// contain control information pertaining to the question-and-answer
/// sequence of a specific transaction. OPT RRs MUST NOT be cached,
/// forwarded, or stored in or loaded from Zone Files.
///
/// The OPT RR MAY be placed anywhere within the additional data section.
/// When an OPT RR is included within any DNS message, it MUST be the
/// only OPT RR in that message. If a query message with more than one
/// OPT RR is received, a FORMERR (RCODE=1) MUST be returned. The
/// placement flexibility for the OPT RR does not override the need for
/// the TSIG or SIG(0) RRs to be the last in the additional section
/// whenever they are present.
///
/// 6.1.2. Wire Format
///
/// An OPT RR has a fixed part and a variable set of options expressed as
/// {attribute, value} pairs. The fixed part holds some DNS metadata,
/// and also a small collection of basic extension elements that we
/// expect to be so popular that it would be a waste of wire space to
/// encode them as {attribute, value} pairs.
///
/// The fixed part of an OPT RR is structured as follows:
///
/// +------------+--------------+------------------------------+
/// | Field Name | Field Type | Description |
/// +------------+--------------+------------------------------+
/// | NAME | domain name | MUST be 0 (root domain) |
/// | TYPE | u_int16_t | OPT (41) |
/// | CLASS | u_int16_t | requestor's UDP payload size |
/// | TTL | u_int32_t | extended RCODE and flags |
/// | RDLEN | u_int16_t | length of all RDATA |
/// | RDATA | octet stream | {attribute,value} pairs |
/// +------------+--------------+------------------------------+
///
/// OPT RR Format
///
/// The variable part of an OPT RR may contain zero or more options in
/// the RDATA. Each option MUST be treated as a bit field. Each option
/// is encoded as:
///
/// +0 (MSB) +1 (LSB)
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
/// 0: | OPTION-CODE |
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
/// 2: | OPTION-LENGTH |
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
/// 4: | |
/// / OPTION-DATA /
/// / /
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
///
/// OPTION-CODE
/// Assigned by the Expert Review process as defined by the DNSEXT
/// working group and the IESG.
///
/// OPTION-LENGTH
/// Size (in octets) of OPTION-DATA.
///
/// OPTION-DATA
/// Varies per OPTION-CODE. MUST be treated as a bit field.
///
/// The order of appearance of option tuples is not defined. If one
/// option modifies the behaviour of another or multiple options are
/// related to one another in some way, they have the same effect
/// regardless of ordering in the RDATA wire encoding.
///
/// Any OPTION-CODE values not understood by a responder or requestor
/// MUST be ignored. Specifications of such options might wish to
/// include some kind of signaled acknowledgement. For example, an
/// option specification might say that if a responder sees and supports
/// option XYZ, it MUST include option XYZ in its response.
///
/// 6.1.3. OPT Record TTL Field Use
///
/// The extended RCODE and flags, which OPT stores in the RR Time to Live
/// (TTL) field, are structured as follows:
///
/// +0 (MSB) +1 (LSB)
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
/// 0: | EXTENDED-RCODE | VERSION |
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
/// 2: | DO| Z |
/// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
///
/// EXTENDED-RCODE
/// Forms the upper 8 bits of extended 12-bit RCODE (together with the
/// 4 bits defined in [RFC1035]. Note that EXTENDED-RCODE value 0
/// indicates that an unextended RCODE is in use (values 0 through
/// 15).
///
/// VERSION
/// Indicates the implementation level of the setter. Full
/// conformance with this specification is indicated by version '0'.
/// Requestors are encouraged to set this to the lowest implemented
/// level capable of expressing a transaction, to minimise the
/// responder and network load of discovering the greatest common
/// implementation level between requestor and responder. A
/// requestor's version numbering strategy MAY ideally be a run-time
/// configuration option.
/// If a responder does not implement the VERSION level of the
/// request, then it MUST respond with RCODE=BADVERS. All responses
/// MUST be limited in format to the VERSION level of the request, but
/// the VERSION of each response SHOULD be the highest implementation
/// level of the responder. In this way, a requestor will learn the
/// implementation level of a responder as a side effect of every
/// response, including error responses and including RCODE=BADVERS.
///
/// 6.1.4. Flags
///
/// DO
/// DNSSEC OK bit as defined by [RFC3225].
///
/// Z
/// Set to zero by senders and ignored by receivers, unless modified
/// in a subsequent specification.
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Default, Debug, PartialEq, Eq, Clone)]
pub struct OPT {
options: HashMap<EdnsCode, EdnsOption>,
}
impl OPT {
/// Creates a new OPT record data.
///
/// # Arguments
///
/// * `options` - A map of the codes and record types
///
/// # Return value
///
/// The newly created OPT data
pub fn new(options: HashMap<EdnsCode, EdnsOption>) -> Self {
Self { options }
}
#[deprecated(note = "Please use as_ref() or as_mut() for shared/mutable references")]
/// The entire map of options
pub fn options(&self) -> &HashMap<EdnsCode, EdnsOption> {
&self.options
}
/// Get a single option based on the code
pub fn get(&self, code: EdnsCode) -> Option<&EdnsOption> {
self.options.get(&code)
}
/// Insert a new option, the key is derived from the `EdnsOption`
pub fn insert(&mut self, option: EdnsOption) {
self.options.insert((&option).into(), option);
}
/// Remove an option, the key is derived from the `EdnsOption`
pub fn remove(&mut self, option: EdnsCode) {
self.options.remove(&option);
}
}
impl AsMut<HashMap<EdnsCode, EdnsOption>> for OPT {
fn as_mut(&mut self) -> &mut HashMap<EdnsCode, EdnsOption> {
&mut self.options
}
}
impl AsRef<HashMap<EdnsCode, EdnsOption>> for OPT {
fn as_ref(&self) -> &HashMap<EdnsCode, EdnsOption> {
&self.options
}
}
/// Read the RData from the given Decoder
pub fn read(decoder: &mut BinDecoder<'_>, rdata_length: Restrict<u16>) -> ProtoResult<OPT> {
let mut state: OptReadState = OptReadState::ReadCode;
let mut options: HashMap<EdnsCode, EdnsOption> = HashMap::new();
let start_idx = decoder.index();
// There is no unsafe direct use of the rdata length after this point
let rdata_length =
rdata_length.map(|u| u as usize).unverified(/*rdata length usage is bounded*/);
while rdata_length > decoder.index() - start_idx {
match state {
OptReadState::ReadCode => {
state = OptReadState::Code {
code: EdnsCode::from(
decoder.read_u16()?.unverified(/*EdnsCode is verified as safe*/),
),
};
}
OptReadState::Code { code } => {
let length = decoder
.read_u16()?
.map(|u| u as usize)
.verify_unwrap(|u| *u <= rdata_length)
.map_err(|_| ProtoError::from("OPT value length exceeds rdata length"))?;
// If we know that the length is 0, we can avoid the `OptReadState::Data` state
// and directly add the option to the map.
// The data state does not process 0-length correctly, since it always reads at
// least 1 byte, thus making the length check fail.
state = if length == 0 {
options.insert(code, (code, &[] as &[u8]).into());
OptReadState::ReadCode
} else {
OptReadState::Data {
code,
length,
// TODO: this cean be replaced with decoder.read_vec(), right?
// the current version allows for malformed opt to be skipped...
collected: Vec::<u8>::with_capacity(length),
}
};
}
OptReadState::Data {
code,
length,
mut collected,
} => {
// TODO: can this be replaced by read_slice()?
collected.push(decoder.pop()?.unverified(/*byte array is safe*/));
if length == collected.len() {
options.insert(code, (code, &collected as &[u8]).into());
state = OptReadState::ReadCode;
} else {
state = OptReadState::Data {
code,
length,
collected,
};
}
}
}
}
if state != OptReadState::ReadCode {
// there was some problem parsing the data for the options, ignoring them
// TODO: should we ignore all of the EDNS data in this case?
warn!("incomplete or poorly formatted EDNS options: {:?}", state);
options.clear();
}
// the record data is stored as unstructured data, the expectation is that this will be processed after initial parsing.
Ok(OPT::new(options))
}
/// Write the RData from the given Decoder
pub fn emit(encoder: &mut BinEncoder<'_>, opt: &OPT) -> ProtoResult<()> {
for (edns_code, edns_option) in opt.as_ref().iter() {
encoder.emit_u16(u16::from(*edns_code))?;
encoder.emit_u16(edns_option.len())?;
edns_option.emit(encoder)?
}
Ok(())
}
#[derive(Debug, PartialEq, Eq)]
enum OptReadState {
ReadCode,
Code {
code: EdnsCode,
}, // expect LSB for the opt code, store the high byte
Data {
code: EdnsCode,
length: usize,
collected: Vec<u8>,
}, // expect the data for the option
}
/// The code of the EDNS data option
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Hash, Debug, Copy, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum EdnsCode {
/// [RFC 6891, Reserved](https://tools.ietf.org/html/rfc6891)
Zero,
/// [RFC 8764l, Apple's Long-Lived Queries, Optional](https://tools.ietf.org/html/rfc8764)
LLQ,
/// [UL On-hold](http://files.dns-sd.org/draft-sekar-dns-ul.txt)
UL,
/// [RFC 5001, NSID](https://tools.ietf.org/html/rfc5001)
NSID,
// 4 Reserved [draft-cheshire-edns0-owner-option] -EXPIRED-
/// [RFC 6975, DNSSEC Algorithm Understood](https://tools.ietf.org/html/rfc6975)
DAU,
/// [RFC 6975, DS Hash Understood](https://tools.ietf.org/html/rfc6975)
DHU,
/// [RFC 6975, NSEC3 Hash Understood](https://tools.ietf.org/html/rfc6975)
N3U,
/// [RFC 7871, Client Subnet, Optional](https://tools.ietf.org/html/rfc7871)
Subnet,
/// [RFC 7314, EDNS EXPIRE, Optional](https://tools.ietf.org/html/rfc7314)
Expire,
/// [RFC 7873, DNS Cookies](https://tools.ietf.org/html/rfc7873)
Cookie,
/// [RFC 7828, edns-tcp-keepalive](https://tools.ietf.org/html/rfc7828)
Keepalive,
/// [RFC 7830, The EDNS(0) Padding](https://tools.ietf.org/html/rfc7830)
Padding,
/// [RFC 7901, CHAIN Query Requests in DNS, Optional](https://tools.ietf.org/html/rfc7901)
Chain,
/// Unknown, used to deal with unknown or unsupported codes
Unknown(u16),
}
// TODO: implement a macro to perform these inversions
impl From<u16> for EdnsCode {
fn from(value: u16) -> Self {
match value {
0 => Self::Zero,
1 => Self::LLQ,
2 => Self::UL,
3 => Self::NSID,
// 4 Reserved [draft-cheshire-edns0-owner-option] -EXPIRED-
5 => Self::DAU,
6 => Self::DHU,
7 => Self::N3U,
8 => Self::Subnet,
9 => Self::Expire,
10 => Self::Cookie,
11 => Self::Keepalive,
12 => Self::Padding,
13 => Self::Chain,
_ => Self::Unknown(value),
}
}
}
impl From<EdnsCode> for u16 {
fn from(value: EdnsCode) -> Self {
match value {
EdnsCode::Zero => 0,
EdnsCode::LLQ => 1,
EdnsCode::UL => 2,
EdnsCode::NSID => 3,
// 4 Reserved [draft-cheshire-edns0-owner-option] -EXPIRED-
EdnsCode::DAU => 5,
EdnsCode::DHU => 6,
EdnsCode::N3U => 7,
EdnsCode::Subnet => 8,
EdnsCode::Expire => 9,
EdnsCode::Cookie => 10,
EdnsCode::Keepalive => 11,
EdnsCode::Padding => 12,
EdnsCode::Chain => 13,
EdnsCode::Unknown(value) => value,
}
}
}
/// options used to pass information about capabilities between client and server
///
/// `note: Not all EdnsOptions are supported at this time.`
///
/// <http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-13>
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialOrd, PartialEq, Eq, Clone, Hash)]
#[non_exhaustive]
pub enum EdnsOption {
/// [RFC 6975, DNSSEC Algorithm Understood](https://tools.ietf.org/html/rfc6975)
#[cfg(feature = "dnssec")]
#[cfg_attr(docsrs, doc(cfg(feature = "dnssec")))]
DAU(SupportedAlgorithms),
/// [RFC 6975, DS Hash Understood](https://tools.ietf.org/html/rfc6975)
#[cfg(feature = "dnssec")]
#[cfg_attr(docsrs, doc(cfg(feature = "dnssec")))]
DHU(SupportedAlgorithms),
/// [RFC 6975, NSEC3 Hash Understood](https://tools.ietf.org/html/rfc6975)
#[cfg(feature = "dnssec")]
#[cfg_attr(docsrs, doc(cfg(feature = "dnssec")))]
N3U(SupportedAlgorithms),
/// Unknown, used to deal with unknown or unsupported codes
Unknown(u16, Vec<u8>),
}
impl EdnsOption {
/// Returns the length in bytes of the EdnsOption
pub fn len(&self) -> u16 {
match *self {
#[cfg(feature = "dnssec")]
EdnsOption::DAU(ref algorithms)
| EdnsOption::DHU(ref algorithms)
| EdnsOption::N3U(ref algorithms) => algorithms.len(),
EdnsOption::Unknown(_, ref data) => data.len() as u16, // TODO: should we verify?
}
}
/// Returns `true` if the length in bytes of the EdnsOption is 0
pub fn is_empty(&self) -> bool {
match *self {
#[cfg(feature = "dnssec")]
EdnsOption::DAU(ref algorithms)
| EdnsOption::DHU(ref algorithms)
| EdnsOption::N3U(ref algorithms) => algorithms.is_empty(),
EdnsOption::Unknown(_, ref data) => data.is_empty(),
}
}
}
impl BinEncodable for EdnsOption {
fn emit(&self, encoder: &mut BinEncoder<'_>) -> ProtoResult<()> {
match *self {
#[cfg(feature = "dnssec")]
EdnsOption::DAU(ref algorithms)
| EdnsOption::DHU(ref algorithms)
| EdnsOption::N3U(ref algorithms) => algorithms.emit(encoder),
EdnsOption::Unknown(_, ref data) => encoder.emit_vec(data), // gah, clone needed or make a crazy api.
}
}
}
/// only the supported extensions are listed right now.
impl<'a> From<(EdnsCode, &'a [u8])> for EdnsOption {
#[allow(clippy::match_single_binding)]
fn from(value: (EdnsCode, &'a [u8])) -> Self {
match value.0 {
#[cfg(feature = "dnssec")]
EdnsCode::DAU => Self::DAU(value.1.into()),
#[cfg(feature = "dnssec")]
EdnsCode::DHU => Self::DHU(value.1.into()),
#[cfg(feature = "dnssec")]
EdnsCode::N3U => Self::N3U(value.1.into()),
_ => Self::Unknown(value.0.into(), value.1.to_vec()),
}
}
}
impl<'a> From<&'a EdnsOption> for Vec<u8> {
fn from(value: &'a EdnsOption) -> Self {
match *value {
#[cfg(feature = "dnssec")]
EdnsOption::DAU(ref algorithms)
| EdnsOption::DHU(ref algorithms)
| EdnsOption::N3U(ref algorithms) => algorithms.into(),
EdnsOption::Unknown(_, ref data) => data.clone(), // gah, clone needed or make a crazy api.
}
}
}
impl<'a> From<&'a EdnsOption> for EdnsCode {
fn from(value: &'a EdnsOption) -> Self {
match *value {
#[cfg(feature = "dnssec")]
EdnsOption::DAU(..) => Self::DAU,
#[cfg(feature = "dnssec")]
EdnsOption::DHU(..) => Self::DHU,
#[cfg(feature = "dnssec")]
EdnsOption::N3U(..) => Self::N3U,
EdnsOption::Unknown(code, _) => code.into(),
}
}
}
#[cfg(test)]
mod tests {
#![allow(clippy::dbg_macro, clippy::print_stdout)]
use super::*;
#[test]
#[cfg(feature = "dnssec")]
fn test() {
let mut rdata = OPT::default();
rdata.insert(EdnsOption::DAU(SupportedAlgorithms::all()));
let mut bytes = Vec::new();
let mut encoder: BinEncoder<'_> = BinEncoder::new(&mut bytes);
assert!(emit(&mut encoder, &rdata).is_ok());
let bytes = encoder.into_bytes();
println!("bytes: {:?}", bytes);
let mut decoder: BinDecoder<'_> = BinDecoder::new(bytes);
let restrict = Restrict::new(bytes.len() as u16);
let read_rdata = read(&mut decoder, restrict).expect("Decoding error");
assert_eq!(rdata, read_rdata);
}
#[test]
fn test_read_empty_option_at_end_of_opt() {
let bytes: Vec<u8> = vec![
0x00, 0x0a, 0x00, 0x08, 0x0b, 0x64, 0xb4, 0xdc, 0xd7, 0xb0, 0xcc, 0x8f, 0x00, 0x08,
0x00, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x0b, 0x00, 0x00,
];
let mut decoder: BinDecoder<'_> = BinDecoder::new(&*bytes);
let read_rdata = read(&mut decoder, Restrict::new(bytes.len() as u16));
assert!(
read_rdata.is_ok(),
"error decoding: {:?}",
read_rdata.unwrap_err()
);
let opt = read_rdata.unwrap();
let mut options = HashMap::default();
options.insert(EdnsCode::Subnet, EdnsOption::Unknown(8, vec![0, 1, 0, 0]));
options.insert(
EdnsCode::Cookie,
EdnsOption::Unknown(10, vec![0x0b, 0x64, 0xb4, 0xdc, 0xd7, 0xb0, 0xcc, 0x8f]),
);
options.insert(EdnsCode::Keepalive, EdnsOption::Unknown(11, vec![]));
let options = OPT::new(options);
assert_eq!(opt, options);
}
}