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// Copyright 2015-2021 Benjamin Fry <benjaminfry@me.com>
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
//! Message metadata
use std::{convert::From, fmt};
use crate::{
error::*,
op::{op_code::OpCode, response_code::ResponseCode},
serialize::binary::*,
};
/// Metadata for the `Message` struct.
///
/// [RFC 1035, DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION, November 1987](https://tools.ietf.org/html/rfc1035)
///
/// ```text
/// 4.1.1. Header section format
///
/// The header contains the following fields
///
/// 1 1 1 1 1 1
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | ID |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// |QR| Opcode |AA|TC|RD|RA|ZZ|AD|CD| RCODE | /// AD and CD from RFC4035
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | QDCOUNT / ZCOUNT |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | ANCOUNT / PRCOUNT |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | NSCOUNT / UPCOUNT |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | ARCOUNT / ADCOUNT |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///
/// where
///
/// Z Reserved for future use. Must be zero in all queries
/// and responses.
///
/// ```
///
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Eq, Hash)]
pub struct Header {
id: u16,
message_type: MessageType,
op_code: OpCode,
authoritative: bool,
truncation: bool,
recursion_desired: bool,
recursion_available: bool,
authentic_data: bool,
checking_disabled: bool,
response_code: ResponseCode,
query_count: u16,
answer_count: u16,
name_server_count: u16,
additional_count: u16,
}
impl fmt::Display for Header {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
write!(
f,
"{id}:{flags}:{code:?}:{answers}/{authorities}/{additionals}",
id = self.id,
flags = self.flags(),
code = self.response_code,
answers = self.answer_count,
authorities = self.name_server_count,
additionals = self.additional_count,
)
}
}
/// Message types are either Query (also Update) or Response
#[derive(Debug, PartialEq, Eq, PartialOrd, Copy, Clone, Hash)]
pub enum MessageType {
/// Queries are Client requests, these are either Queries or Updates
Query,
/// Response message from the Server or upstream Resolver
Response,
}
impl fmt::Display for MessageType {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
let s = match self {
MessageType::Query => "QUERY",
MessageType::Response => "RESPONSE",
};
f.write_str(s)
}
}
/// All the flags of the request/response header
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub struct Flags {
authoritative: bool,
truncation: bool,
recursion_desired: bool,
recursion_available: bool,
authentic_data: bool,
checking_disabled: bool,
}
/// We are following the `dig` commands display format for the header flags
///
/// Example: "RD,AA,RA;" is Recursion-Desired, Authoritative-Answer, Recursion-Available.
impl fmt::Display for Flags {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
const SEPARATOR: &str = ",";
let flags = [
(self.recursion_desired, "RD"),
(self.checking_disabled, "CD"),
(self.truncation, "TC"),
(self.authoritative, "AA"),
(self.recursion_available, "RA"),
(self.authentic_data, "AD"),
];
let mut iter = flags
.iter()
.cloned()
.filter_map(|(flag, s)| if flag { Some(s) } else { None });
// print first without a separator, then print the rest.
if let Some(s) = iter.next() {
f.write_str(s)?
}
for s in iter {
f.write_str(SEPARATOR)?;
f.write_str(s)?;
}
Ok(())
}
}
impl Default for Header {
fn default() -> Self {
Self::new()
}
}
impl Header {
// TODO: we should make id, message_type and op_code all required and non-editable
/// A default Header, not very useful.
pub const fn new() -> Self {
Self {
id: 0,
message_type: MessageType::Query,
op_code: OpCode::Query,
authoritative: false,
truncation: false,
recursion_desired: false,
recursion_available: false,
authentic_data: false,
checking_disabled: false,
response_code: ResponseCode::NoError,
query_count: 0,
answer_count: 0,
name_server_count: 0,
additional_count: 0,
}
}
/// Construct a new header based off the request header. This copies over the RD (recursion-desired)
/// and CD (checking-disabled), as well as the op_code and id of the request.
///
/// See https://datatracker.ietf.org/doc/html/rfc6895#section-2
///
/// ```text
/// The AA, TC, RD, RA, and CD bits are each theoretically meaningful
/// only in queries or only in responses, depending on the bit. The AD
/// bit was only meaningful in responses but is expected to have a
/// separate but related meaning in queries (see Section 5.7 of
/// [RFC6840]). Only the RD and CD bits are expected to be copied from
/// the query to the response; however, some DNS implementations copy all
/// the query header as the initial value of the response header. Thus,
/// any attempt to use a "query" bit with a different meaning in a
/// response or to define a query meaning for a "response" bit may be
/// dangerous, given the existing implementation. Meanings for these
/// bits may only be assigned by a Standards Action.
/// ```
pub fn response_from_request(header: &Self) -> Self {
Self {
id: header.id,
message_type: MessageType::Response,
op_code: header.op_code,
authoritative: false,
truncation: false,
recursion_desired: header.recursion_desired,
recursion_available: false,
authentic_data: false,
checking_disabled: header.checking_disabled,
response_code: ResponseCode::default(),
query_count: 0,
answer_count: 0,
name_server_count: 0,
additional_count: 0,
}
}
/// Length of the header, always 12 bytes
#[inline(always)]
pub fn len() -> usize {
12 /* this is always 12 bytes */
}
/// Sets the id of the message, for queries this should be random.
pub fn set_id(&mut self, id: u16) -> &mut Self {
self.id = id;
self
}
/// Sets the message type, Queries and Updates both use Query.
pub fn set_message_type(&mut self, message_type: MessageType) -> &mut Self {
self.message_type = message_type;
self
}
/// Set the operation code for the message
pub fn set_op_code(&mut self, op_code: OpCode) -> &mut Self {
self.op_code = op_code;
self
}
/// From the server is specifies that it is an authoritative response.
pub fn set_authoritative(&mut self, authoritative: bool) -> &mut Self {
self.authoritative = authoritative;
self
}
/// Specifies that the records were too large for the payload.
///
/// See EDNS or TCP for resolutions to truncation.
pub fn set_truncated(&mut self, truncated: bool) -> &mut Self {
self.truncation = truncated;
self
}
/// Specify that the resolver should recursively request data from upstream DNS nodes
pub fn set_recursion_desired(&mut self, recursion_desired: bool) -> &mut Self {
self.recursion_desired = recursion_desired;
self
}
/// Specifies that recursion is available from this or the remote resolver
pub fn set_recursion_available(&mut self, recursion_available: bool) -> &mut Self {
self.recursion_available = recursion_available;
self
}
/// Specifies that the data is authentic, i.e. the resolver believes all data to be valid through DNSSec
pub fn set_authentic_data(&mut self, authentic_data: bool) -> &mut Self {
self.authentic_data = authentic_data;
self
}
/// Used during recursive resolution to specified if a resolver should or should not validate DNSSec signatures
pub fn set_checking_disabled(&mut self, checking_disabled: bool) -> &mut Self {
self.checking_disabled = checking_disabled;
self
}
/// A method to get all header flags (useful for Display purposes)
pub fn flags(&self) -> Flags {
Flags {
authoritative: self.authoritative,
authentic_data: self.authentic_data,
checking_disabled: self.checking_disabled,
recursion_available: self.recursion_available,
recursion_desired: self.recursion_desired,
truncation: self.truncation,
}
}
/// The low response code (original response codes before EDNS extensions)
pub fn set_response_code(&mut self, response_code: ResponseCode) -> &mut Self {
self.response_code = response_code;
self
}
/// This combines the high and low response code values to form the complete ResponseCode from the EDNS record.
/// The existing high order bits will be overwritten (if set), and `high_response_code` will be merge with
/// the existing low order bits.
///
/// This is intended for use during decoding.
#[doc(hidden)]
pub fn merge_response_code(&mut self, high_response_code: u8) {
self.response_code = ResponseCode::from(high_response_code, self.response_code.low());
}
/// Number or query records in the message
pub fn set_query_count(&mut self, query_count: u16) -> &mut Self {
self.query_count = query_count;
self
}
/// Number of answer records in the message
pub fn set_answer_count(&mut self, answer_count: u16) -> &mut Self {
self.answer_count = answer_count;
self
}
/// Number of name server records in the message
pub fn set_name_server_count(&mut self, name_server_count: u16) -> &mut Self {
self.name_server_count = name_server_count;
self
}
/// Number of additional records in the message
pub fn set_additional_count(&mut self, additional_count: u16) -> &mut Self {
self.additional_count = additional_count;
self
}
/// ```text
/// ID A 16 bit identifier assigned by the program that
/// generates any kind of query. This identifier is copied
/// the corresponding reply and can be used by the requester
/// to match up replies to outstanding queries.
/// ```
pub fn id(&self) -> u16 {
self.id
}
/// ```text
/// QR A one bit field that specifies whether this message is a
/// query (0), or a response (1).
/// ```
pub fn message_type(&self) -> MessageType {
self.message_type
}
/// ```text
/// OPCODE A four bit field that specifies kind of query in this
/// message. This value is set by the originator of a query
/// and copied into the response. The values are: <see super::op_code>
/// ```
pub fn op_code(&self) -> OpCode {
self.op_code
}
/// ```text
/// AA Authoritative Answer - this bit is valid in responses,
/// and specifies that the responding name server is an
/// authority for the domain name in question section.
///
/// Note that the contents of the answer section may have
/// multiple owner names because of aliases. The AA bit
/// corresponds to the name which matches the query name, or
/// the first owner name in the answer section.
/// ```
pub fn authoritative(&self) -> bool {
self.authoritative
}
/// ```text
/// TC TrunCation - specifies that this message was truncated
/// due to length greater than that permitted on the
/// transmission channel.
/// ```
pub fn truncated(&self) -> bool {
self.truncation
}
/// ```text
/// RD Recursion Desired - this bit may be set in a query and
/// is copied into the response. If RD is set, it directs
/// the name server to pursue the query recursively.
/// Recursive query support is optional.
/// ```
pub fn recursion_desired(&self) -> bool {
self.recursion_desired
}
/// ```text
/// RA Recursion Available - this be is set or cleared in a
/// response, and denotes whether recursive query support is
/// available in the name server.
/// ```
pub fn recursion_available(&self) -> bool {
self.recursion_available
}
/// [RFC 4035, DNSSEC Resource Records, March 2005](https://tools.ietf.org/html/rfc4035#section-3.1.6)
///
/// ```text
///
/// 3.1.6. The AD and CD Bits in an Authoritative Response
///
/// The CD and AD bits are designed for use in communication between
/// security-aware resolvers and security-aware recursive name servers.
/// These bits are for the most part not relevant to query processing by
/// security-aware authoritative name servers.
///
/// A security-aware name server does not perform signature validation
/// for authoritative data during query processing, even when the CD bit
/// is clear. A security-aware name server SHOULD clear the CD bit when
/// composing an authoritative response.
///
/// A security-aware name server MUST NOT set the AD bit in a response
/// unless the name server considers all RRsets in the Answer and
/// Authority sections of the response to be authentic. A security-aware
/// name server's local policy MAY consider data from an authoritative
/// zone to be authentic without further validation. However, the name
/// server MUST NOT do so unless the name server obtained the
/// authoritative zone via secure means (such as a secure zone transfer
/// mechanism) and MUST NOT do so unless this behavior has been
/// configured explicitly.
///
/// A security-aware name server that supports recursion MUST follow the
/// rules for the CD and AD bits given in Section 3.2 when generating a
/// response that involves data obtained via recursion.
/// ```
pub fn authentic_data(&self) -> bool {
self.authentic_data
}
/// see `is_authentic_data()`
pub fn checking_disabled(&self) -> bool {
self.checking_disabled
}
/// ```text
/// RCODE Response code - this 4 bit field is set as part of
/// responses. The values have the following
/// interpretation: <see super::response_code>
/// ```
pub fn response_code(&self) -> ResponseCode {
self.response_code
}
/// ```text
/// QDCOUNT an unsigned 16 bit integer specifying the number of
/// entries in the question section.
/// ```
///
/// # Return value
///
/// If this is a query, this will return the number of queries in the query section of the
// message, fo updates this represents the zone count (must be no more than 1).
pub fn query_count(&self) -> u16 {
self.query_count
}
/// ```text
/// ANCOUNT an unsigned 16 bit integer specifying the number of
/// resource records in the answer section.
/// ```
///
/// # Return value
///
/// For query responses this is the number of records in the answer section, should be 0 for
/// requests, for updates this is the count of prerequisite records.
pub fn answer_count(&self) -> u16 {
self.answer_count
}
/// for queries this is the nameservers which are authorities for the SOA of the Record
/// for updates this is the update record count
/// ```text
/// NSCOUNT an unsigned 16 bit integer specifying the number of name
/// server resource records in the authority records
/// section.
/// ```
///
/// # Return value
///
/// For query responses this is the number of authorities, or nameservers, in the name server
/// section, for updates this is the number of update records being sent.
pub fn name_server_count(&self) -> u16 {
self.name_server_count
}
/// ```text
/// ARCOUNT an unsigned 16 bit integer specifying the number of
/// resource records in the additional records section.
/// ```
///
/// # Return value
///
/// This is the additional record section count, this section may include EDNS options.
pub fn additional_count(&self) -> u16 {
self.additional_count
}
}
impl BinEncodable for Header {
fn emit(&self, encoder: &mut BinEncoder<'_>) -> ProtoResult<()> {
encoder.reserve(12)?; // the 12 bytes for the following fields;
// Id
encoder.emit_u16(self.id)?;
// IsQuery, OpCode, Authoritative, Truncation, RecursionDesired
let mut q_opcd_a_t_r: u8 = if let MessageType::Response = self.message_type {
0x80
} else {
0x00
};
q_opcd_a_t_r |= u8::from(self.op_code) << 3;
q_opcd_a_t_r |= if self.authoritative { 0x4 } else { 0x0 };
q_opcd_a_t_r |= if self.truncation { 0x2 } else { 0x0 };
q_opcd_a_t_r |= if self.recursion_desired { 0x1 } else { 0x0 };
encoder.emit(q_opcd_a_t_r)?;
// IsRecursionAvailable, Triple 0's, ResponseCode
let mut r_z_ad_cd_rcod: u8 = if self.recursion_available {
0b1000_0000
} else {
0b0000_0000
};
r_z_ad_cd_rcod |= if self.authentic_data {
0b0010_0000
} else {
0b0000_0000
};
r_z_ad_cd_rcod |= if self.checking_disabled {
0b0001_0000
} else {
0b0000_0000
};
r_z_ad_cd_rcod |= self.response_code.low();
encoder.emit(r_z_ad_cd_rcod)?;
encoder.emit_u16(self.query_count)?;
encoder.emit_u16(self.answer_count)?;
encoder.emit_u16(self.name_server_count)?;
encoder.emit_u16(self.additional_count)?;
Ok(())
}
}
impl<'r> BinDecodable<'r> for Header {
fn read(decoder: &mut BinDecoder<'r>) -> ProtoResult<Self> {
let id = decoder.read_u16()?.unverified(/*it is valid for this to be any u16*/);
let q_opcd_a_t_r = decoder.pop()?.unverified(/*used as a bitfield, this is safe*/);
// if the first bit is set
let message_type = if (0b1000_0000 & q_opcd_a_t_r) == 0b1000_0000 {
MessageType::Response
} else {
MessageType::Query
};
// the 4bit opcode, masked and then shifted right 3bits for the u8...
let op_code: OpCode = OpCode::from_u8((0b0111_1000 & q_opcd_a_t_r) >> 3)?;
let authoritative = (0b0000_0100 & q_opcd_a_t_r) == 0b0000_0100;
let truncation = (0b0000_0010 & q_opcd_a_t_r) == 0b0000_0010;
let recursion_desired = (0b0000_0001 & q_opcd_a_t_r) == 0b0000_0001;
let r_z_ad_cd_rcod = decoder.pop()?.unverified(/*used as a bitfield, this is safe*/); // fail fast...
let recursion_available = (0b1000_0000 & r_z_ad_cd_rcod) == 0b1000_0000;
let authentic_data = (0b0010_0000 & r_z_ad_cd_rcod) == 0b0010_0000;
let checking_disabled = (0b0001_0000 & r_z_ad_cd_rcod) == 0b0001_0000;
let response_code: u8 = 0b0000_1111 & r_z_ad_cd_rcod;
let response_code = ResponseCode::from_low(response_code);
// TODO: We should pass these restrictions on, they can't be trusted, but that would seriously complicate the Header type..
// TODO: perhaps the read methods for BinDecodable should return Restrict?
let query_count =
decoder.read_u16()?.unverified(/*this must be verified when reading queries*/);
let answer_count =
decoder.read_u16()?.unverified(/*this must be evaluated when reading records*/);
let name_server_count =
decoder.read_u16()?.unverified(/*this must be evaluated when reading records*/);
let additional_count =
decoder.read_u16()?.unverified(/*this must be evaluated when reading records*/);
// TODO: question, should this use the builder pattern instead? might be cleaner code, but
// this guarantees that the Header is fully instantiated with all values...
Ok(Self {
id,
message_type,
op_code,
authoritative,
truncation,
recursion_desired,
recursion_available,
authentic_data,
checking_disabled,
response_code,
query_count,
answer_count,
name_server_count,
additional_count,
})
}
}
#[test]
fn test_parse() {
let byte_vec = vec![
0x01, 0x10, 0xAA, 0x83, // 0b1010 1010 1000 0011
0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11,
];
let mut decoder = BinDecoder::new(&byte_vec);
let expect = Header {
id: 0x0110,
message_type: MessageType::Response,
op_code: OpCode::Update,
authoritative: false,
truncation: true,
recursion_desired: false,
recursion_available: true,
authentic_data: false,
checking_disabled: false,
response_code: ResponseCode::NXDomain,
query_count: 0x8877,
answer_count: 0x6655,
name_server_count: 0x4433,
additional_count: 0x2211,
};
let got = Header::read(&mut decoder).unwrap();
assert_eq!(got, expect);
}
#[test]
fn test_write() {
let header = Header {
id: 0x0110,
message_type: MessageType::Response,
op_code: OpCode::Update,
authoritative: false,
truncation: true,
recursion_desired: false,
recursion_available: true,
authentic_data: false,
checking_disabled: false,
response_code: ResponseCode::NXDomain,
query_count: 0x8877,
answer_count: 0x6655,
name_server_count: 0x4433,
additional_count: 0x2211,
};
let expect: Vec<u8> = vec![
0x01, 0x10, 0xAA, 0x83, // 0b1010 1010 1000 0011
0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11,
];
let mut bytes = Vec::with_capacity(512);
{
let mut encoder = BinEncoder::new(&mut bytes);
header.emit(&mut encoder).unwrap();
}
assert_eq!(bytes, expect);
}