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// Copyright 2015-2019 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.
//! Dynamic Delegation Discovery System
use std::fmt;
#[cfg(feature = "serde-config")]
use serde::{Deserialize, Serialize};
use crate::error::*;
use crate::rr::domain::Name;
use crate::serialize::binary::*;
/// [RFC 3403 DDDS DNS Database, October 2002](https://tools.ietf.org/html/rfc3403#section-4)
///
/// ```text
/// 4.1 Packet Format
///
/// The packet format of the NAPTR RR is given below. The DNS type code
/// for NAPTR is 35.
///
/// The packet format for the NAPTR record is as follows
/// 1 1 1 1 1 1
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | ORDER |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// | PREFERENCE |
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// / FLAGS /
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// / SERVICES /
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// / REGEXP /
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/// / REPLACEMENT /
/// / /
/// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///
/// <character-string> and <domain-name> as used here are defined in RFC
/// 1035 [7].
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialEq, Eq, Hash, Clone)]
pub struct NAPTR {
order: u16,
preference: u16,
flags: Box<[u8]>,
services: Box<[u8]>,
regexp: Box<[u8]>,
replacement: Name,
}
impl NAPTR {
/// Constructs a new NAPTR record
///
/// # Arguments
///
/// * `order` - the order in which the NAPTR records MUST be processed in order to accurately represent the ordered list of Rules.
/// * `preference` - this field is equivalent to the Priority value in the DDDS Algorithm.
/// * `flags` - flags to control aspects of the rewriting and interpretation of the fields in the record. Flags are single characters from the set A-Z and 0-9.
/// * `services` - the Service Parameters applicable to this this delegation path.
/// * `regexp` - substitution expression that is applied to the original string held by the client in order to construct the next domain name to lookup.
/// * `replacement` - the next domain-name to query for depending on the potential values found in the flags field.
pub fn new(
order: u16,
preference: u16,
flags: Box<[u8]>,
services: Box<[u8]>,
regexp: Box<[u8]>,
replacement: Name,
) -> Self {
Self {
order,
preference,
flags,
services,
regexp,
replacement,
}
}
/// ```text
/// ORDER
/// A 16-bit unsigned integer specifying the order in which the NAPTR
/// records MUST be processed in order to accurately represent the
/// ordered list of Rules. The ordering is from lowest to highest.
/// If two records have the same order value then they are considered
/// to be the same rule and should be selected based on the
/// combination of the Preference values and Services offered.
/// ```
pub fn order(&self) -> u16 {
self.order
}
/// ```text
/// PREFERENCE
/// Although it is called "preference" in deference to DNS
/// terminology, this field is equivalent to the Priority value in the
/// DDDS Algorithm. It is a 16-bit unsigned integer that specifies
/// the order in which NAPTR records with equal Order values SHOULD be
/// processed, low numbers being processed before high numbers. This
/// is similar to the preference field in an MX record, and is used so
/// domain administrators can direct clients towards more capable
/// hosts or lighter weight protocols. A client MAY look at records
/// with higher preference values if it has a good reason to do so
/// such as not supporting some protocol or service very well.
///
/// The important difference between Order and Preference is that once
/// a match is found the client MUST NOT consider records with a
/// different Order but they MAY process records with the same Order
/// but different Preferences. The only exception to this is noted in
/// the second important Note in the DDDS algorithm specification
/// concerning allowing clients to use more complex Service
/// determination between steps 3 and 4 in the algorithm. Preference
/// is used to give communicate a higher quality of service to rules
/// that are considered the same from an authority standpoint but not
/// from a simple load balancing standpoint.
///
/// It is important to note that DNS contains several load balancing
/// mechanisms and if load balancing among otherwise equal services
/// should be needed then methods such as SRV records or multiple A
/// records should be utilized to accomplish load balancing.
/// ```
pub fn preference(&self) -> u16 {
self.preference
}
/// ```text
/// FLAGS
/// A <character-string> containing flags to control aspects of the
/// rewriting and interpretation of the fields in the record. Flags
/// are single characters from the set A-Z and 0-9. The case of the
/// alphabetic characters is not significant. The field can be empty.
///
/// It is up to the Application specifying how it is using this
/// Database to define the Flags in this field. It must define which
/// ones are terminal and which ones are not.
/// ```
pub fn flags(&self) -> &[u8] {
&self.flags
}
/// ```text
/// SERVICES
/// A <character-string> that specifies the Service Parameters
/// applicable to this this delegation path. It is up to the
/// Application Specification to specify the values found in this
/// field.
/// ```
pub fn services(&self) -> &[u8] {
&self.services
}
/// ```text
/// REGEXP
/// A <character-string> containing a substitution expression that is
/// applied to the original string held by the client in order to
/// construct the next domain name to lookup. See the DDDS Algorithm
/// specification for the syntax of this field.
///
/// As stated in the DDDS algorithm, The regular expressions MUST NOT
/// be used in a cumulative fashion, that is, they should only be
/// applied to the original string held by the client, never to the
/// domain name p roduced by a previous NAPTR rewrite. The latter is
/// tempting in some applications but experience has shown such use to
/// be extremely fault sensitive, very error prone, and extremely
/// difficult to debug.
/// ```
pub fn regexp(&self) -> &[u8] {
&self.regexp
}
/// ```text
/// REPLACEMENT
/// A <domain-name> which is the next domain-name to query for
/// depending on the potential values found in the flags field. This
/// field is used when the regular expression is a simple replacement
/// operation. Any value in this field MUST be a fully qualified
/// domain-name. Name compression is not to be used for this field.
///
/// This field and the REGEXP field together make up the Substitution
/// Expression in the DDDS Algorithm. It is simply a historical
/// optimization specifically for DNS compression that this field
/// exists. The fields are also mutually exclusive. If a record is
/// returned that has values for both fields then it is considered to
/// be in error and SHOULD be either ignored or an error returned.
/// ```
pub fn replacement(&self) -> &Name {
&self.replacement
}
}
/// verifies that the flags are valid
pub fn verify_flags(flags: &[u8]) -> bool {
flags
.iter()
.all(|c| matches!(c, b'0'..=b'9' | b'a'..=b'z' | b'A'..=b'Z'))
}
/// Read the RData from the given Decoder
pub fn read(decoder: &mut BinDecoder<'_>) -> ProtoResult<NAPTR> {
Ok(NAPTR::new(
decoder.read_u16()?.unverified(/*any u16 is valid*/),
decoder.read_u16()?.unverified(/*any u16 is valid*/),
// must be 0-9a-z
decoder
.read_character_data()?
.verify_unwrap(|s| verify_flags(s))
.map_err(|_e| ProtoError::from("flags are not within range [a-zA-Z0-9]"))?
.to_vec()
.into_boxed_slice(),
decoder.read_character_data()?.unverified(/*any chardata*/).to_vec().into_boxed_slice(),
decoder.read_character_data()?.unverified(/*any chardata*/).to_vec().into_boxed_slice(),
Name::read(decoder)?,
))
}
/// Declares the method for emitting this type
pub fn emit(encoder: &mut BinEncoder<'_>, naptr: &NAPTR) -> ProtoResult<()> {
naptr.order.emit(encoder)?;
naptr.preference.emit(encoder)?;
encoder.emit_character_data(&naptr.flags)?;
encoder.emit_character_data(&naptr.services)?;
encoder.emit_character_data(&naptr.regexp)?;
encoder.with_canonical_names(|encoder| naptr.replacement.emit(encoder))?;
Ok(())
}
/// [RFC 2915](https://tools.ietf.org/html/rfc2915), NAPTR DNS RR, September 2000
///
/// ```text
/// Master File Format
///
/// The master file format follows the standard rules in RFC-1035 [1].
/// Order and preference, being 16-bit unsigned integers, shall be an
/// integer between 0 and 65535. The Flags and Services and Regexp
/// fields are all quoted <character-string>s. Since the Regexp field
/// can contain numerous backslashes and thus should be treated with
/// care. See Section 10 for how to correctly enter and escape the
/// regular expression.
///
/// ;; order pref flags service regexp replacement
/// IN NAPTR 100 50 "a" "z3950+N2L+N2C" "" cidserver.example.com.
/// IN NAPTR 100 50 "a" "rcds+N2C" "" cidserver.example.com.
/// IN NAPTR 100 50 "s" "http+N2L+N2C+N2R" "" www.example.com.
/// ```
impl fmt::Display for NAPTR {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
write!(
f,
"{order} {pref} \"{flags}\" \"{service}\" \"{regexp}\" {replace}",
order = self.order,
pref = self.preference,
flags = &String::from_utf8_lossy(&self.flags),
service = &String::from_utf8_lossy(&self.services),
regexp = &String::from_utf8_lossy(&self.regexp),
replace = self.replacement
)
}
}
#[cfg(test)]
mod tests {
#![allow(clippy::dbg_macro, clippy::print_stdout)]
use super::*;
#[test]
fn test() {
use std::str::FromStr;
let rdata = NAPTR::new(
8,
16,
b"aa11AA".to_vec().into_boxed_slice(),
b"services".to_vec().into_boxed_slice(),
b"regexpr".to_vec().into_boxed_slice(),
Name::from_str("naptr.example.com").unwrap(),
);
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 read_rdata = read(&mut decoder).expect("Decoding error");
assert_eq!(rdata, read_rdata);
}
#[test]
fn test_bad_data() {
use std::str::FromStr;
let rdata = NAPTR::new(
8,
16,
b"aa11AA-".to_vec().into_boxed_slice(),
b"services".to_vec().into_boxed_slice(),
b"regexpr".to_vec().into_boxed_slice(),
Name::from_str("naptr.example.com").unwrap(),
);
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 read_rdata = read(&mut decoder);
assert!(
read_rdata.is_err(),
"should have failed decoding with bad flag data"
);
}
}