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// Copyright 2015-2017 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.
//! TLSA records for storing TLS certificate validation information
use std::fmt;
#[cfg(feature = "serde-config")]
use serde::{Deserialize, Serialize};
use super::sshfp;
use crate::error::*;
use crate::serialize::binary::*;
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2.1)
///
/// ```text
/// 2.1. TLSA RDATA Wire Format
///
/// The RDATA for a TLSA RR consists of a one-octet certificate usage
/// field, a one-octet selector field, a one-octet matching type field,
/// and the certificate association data field.
///
/// 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | Cert. Usage | Selector | Matching Type | /
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
/// / /
/// / Certificate Association Data /
/// / /
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialEq, Eq, Hash, Clone)]
pub struct TLSA {
cert_usage: CertUsage,
selector: Selector,
matching: Matching,
cert_data: Vec<u8>,
}
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2.1.1)
///
/// ```text
/// 2.1.1. The Certificate Usage Field
///
/// A one-octet value, called "certificate usage", specifies the provided
/// association that will be used to match the certificate presented in
/// the TLS handshake. This value is defined in a new IANA registry (see
/// Section 7.2) in order to make it easier to add additional certificate
/// usages in the future. The certificate usages defined in this
/// document are:
///
/// 0 -- CA
///
/// 1 -- Service
///
/// 2 -- TrustAnchor
///
/// 3 -- DomainIssued
///
/// The certificate usages defined in this document explicitly only apply
/// to PKIX-formatted certificates in DER encoding [X.690]. If TLS
/// allows other formats later, or if extensions to this RRtype are made
/// that accept other formats for certificates, those certificates will
/// need their own certificate usage values.
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
pub enum CertUsage {
/// ```text
/// 0 -- Certificate usage 0 is used to specify a CA certificate, or
/// the public key of such a certificate, that MUST be found in any of
/// the PKIX certification paths for the end entity certificate given
/// by the server in TLS. This certificate usage is sometimes
/// referred to as "CA constraint" because it limits which CA can be
/// used to issue certificates for a given service on a host. The
/// presented certificate MUST pass PKIX certification path
/// validation, and a CA certificate that matches the TLSA record MUST
/// be included as part of a valid certification path. Because this
/// certificate usage allows both trust anchors and CA certificates,
/// the certificate might or might not have the basicConstraints
/// extension present.
/// ```
CA,
/// ```text
/// 1 -- Certificate usage 1 is used to specify an end entity
/// certificate, or the public key of such a certificate, that MUST be
/// matched with the end entity certificate given by the server in
/// TLS. This certificate usage is sometimes referred to as "service
/// certificate constraint" because it limits which end entity
/// certificate can be used by a given service on a host. The target
/// certificate MUST pass PKIX certification path validation and MUST
/// match the TLSA record.
/// ```
Service,
/// ```text
/// 2 -- Certificate usage 2 is used to specify a certificate, or the
/// public key of such a certificate, that MUST be used as the trust
/// anchor when validating the end entity certificate given by the
/// server in TLS. This certificate usage is sometimes referred to as
/// "trust anchor assertion" and allows a domain name administrator to
/// specify a new trust anchor -- for example, if the domain issues
/// its own certificates under its own CA that is not expected to be
/// in the end users' collection of trust anchors. The target
/// certificate MUST pass PKIX certification path validation, with any
/// certificate matching the TLSA record considered to be a trust
/// anchor for this certification path validation.
/// ```
TrustAnchor,
/// ```text
/// 3 -- Certificate usage 3 is used to specify a certificate, or the
/// public key of such a certificate, that MUST match the end entity
/// certificate given by the server in TLS. This certificate usage is
/// sometimes referred to as "domain-issued certificate" because it
/// allows for a domain name administrator to issue certificates for a
/// domain without involving a third-party CA. The target certificate
/// MUST match the TLSA record. The difference between certificate
/// usage 1 and certificate usage 3 is that certificate usage 1
/// requires that the certificate pass PKIX validation, but PKIX
/// validation is not tested for certificate usage 3.
/// ```
DomainIssued,
/// Unassigned at the time of this implementation
Unassigned(u8),
/// Private usage
Private,
}
impl From<u8> for CertUsage {
fn from(usage: u8) -> Self {
match usage {
0 => Self::CA,
1 => Self::Service,
2 => Self::TrustAnchor,
3 => Self::DomainIssued,
4..=254 => Self::Unassigned(usage),
255 => Self::Private,
}
}
}
impl From<CertUsage> for u8 {
fn from(usage: CertUsage) -> Self {
match usage {
CertUsage::CA => 0,
CertUsage::Service => 1,
CertUsage::TrustAnchor => 2,
CertUsage::DomainIssued => 3,
CertUsage::Unassigned(usage) => usage,
CertUsage::Private => 255,
}
}
}
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2.1.1)
///
/// ```text
/// 2.1.2. The Selector Field
///
/// A one-octet value, called "selector", specifies which part of the TLS
/// certificate presented by the server will be matched against the
/// association data. This value is defined in a new IANA registry (see
/// Section 7.3). The selectors defined in this document are:
///
/// 0 -- Full
///
/// 1 -- Spki
///
/// (Note that the use of "selector" in this document is completely
/// unrelated to the use of "selector" in DomainKeys Identified Mail
/// (DKIM) [RFC6376].)
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
pub enum Selector {
/// Full certificate: the Certificate binary structure as defined in [RFC5280](https://tools.ietf.org/html/rfc5280)
Full,
/// SubjectPublicKeyInfo: DER-encoded binary structure as defined in [RFC5280](https://tools.ietf.org/html/rfc5280)
Spki,
/// Unassigned at the time of this writing
Unassigned(u8),
/// Private usage
Private,
}
impl From<u8> for Selector {
fn from(selector: u8) -> Self {
match selector {
0 => Self::Full,
1 => Self::Spki,
2..=254 => Self::Unassigned(selector),
255 => Self::Private,
}
}
}
impl From<Selector> for u8 {
fn from(selector: Selector) -> Self {
match selector {
Selector::Full => 0,
Selector::Spki => 1,
Selector::Unassigned(selector) => selector,
Selector::Private => 255,
}
}
}
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2.1.3)
///
/// ```text
/// 2.1.3. The Matching Type Field
///
/// A one-octet value, called "matching type", specifies how the
/// certificate association is presented. This value is defined in a new
/// IANA registry (see Section 7.4). The types defined in this document
/// are:
///
/// 0 -- Raw
///
/// 1 -- Sha256
///
/// 2 -- Sha512
///
/// If the TLSA record's matching type is a hash, having the record use
/// the same hash algorithm that was used in the signature in the
/// certificate (if possible) will assist clients that support a small
/// number of hash algorithms.
/// ```
#[cfg_attr(feature = "serde-config", derive(Deserialize, Serialize))]
#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
pub enum Matching {
/// Exact match on selected content
Raw,
/// SHA-256 hash of selected content [RFC6234](https://tools.ietf.org/html/rfc6234)
Sha256,
/// SHA-512 hash of selected content [RFC6234](https://tools.ietf.org/html/rfc6234)
Sha512,
/// Unassigned at the time of this writing
Unassigned(u8),
/// Private usage
Private,
}
impl From<u8> for Matching {
fn from(matching: u8) -> Self {
match matching {
0 => Self::Raw,
1 => Self::Sha256,
2 => Self::Sha512,
3..=254 => Self::Unassigned(matching),
255 => Self::Private,
}
}
}
impl From<Matching> for u8 {
fn from(matching: Matching) -> Self {
match matching {
Matching::Raw => 0,
Matching::Sha256 => 1,
Matching::Sha512 => 2,
Matching::Unassigned(matching) => matching,
Matching::Private => 255,
}
}
}
impl TLSA {
/// Constructs a new TLSA
///
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2)
///
/// ```text
/// 2. The TLSA Resource Record
///
/// The TLSA DNS resource record (RR) is used to associate a TLS server
/// certificate or public key with the domain name where the record is
/// found, thus forming a "TLSA certificate association". The semantics
/// of how the TLSA RR is interpreted are given later in this document.
///
/// The type value for the TLSA RR type is defined in Section 7.1.
///
/// The TLSA RR is class independent.
///
/// The TLSA RR has no special Time to Live (TTL) requirements.
/// ```
pub fn new(
cert_usage: CertUsage,
selector: Selector,
matching: Matching,
cert_data: Vec<u8>,
) -> Self {
Self {
cert_usage,
selector,
matching,
cert_data,
}
}
/// Specifies the provided association that will be used to match the certificate presented in the TLS handshake
pub fn cert_usage(&self) -> CertUsage {
self.cert_usage
}
/// Specifies which part of the TLS certificate presented by the server will be matched against the association data
pub fn selector(&self) -> Selector {
self.selector
}
/// Specifies how the certificate association is presented
pub fn matching(&self) -> Matching {
self.matching
}
/// Binary data for validating the cert, see other members to understand format
pub fn cert_data(&self) -> &[u8] {
&self.cert_data
}
}
/// Read the RData from the given Decoder
///
/// ```text
/// 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
/// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// | Cert. Usage | Selector | Matching Type | /
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
/// / /
/// / Certificate Association Data /
/// / /
/// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/// ```
pub fn read(decoder: &mut BinDecoder<'_>, rdata_length: Restrict<u16>) -> ProtoResult<TLSA> {
let cert_usage = decoder.read_u8()?.unverified(/*CertUsage is verified*/).into();
let selector = decoder.read_u8()?.unverified(/*Selector is verified*/).into();
let matching = decoder.read_u8()?.unverified(/*Matching is verified*/).into();
// the remaining data is for the cert
let cert_len = rdata_length
.map(|u| u as usize)
.checked_sub(3)
.map_err(|_| ProtoError::from("invalid rdata length in TLSA"))?
.unverified(/*used purely as length safely*/);
let cert_data = decoder.read_vec(cert_len)?.unverified(/*will fail in usage if invalid*/);
Ok(TLSA {
cert_usage,
selector,
matching,
cert_data,
})
}
/// Write the RData from the given Decoder
pub fn emit(encoder: &mut BinEncoder<'_>, tlsa: &TLSA) -> ProtoResult<()> {
encoder.emit_u8(tlsa.cert_usage.into())?;
encoder.emit_u8(tlsa.selector.into())?;
encoder.emit_u8(tlsa.matching.into())?;
encoder.emit_vec(&tlsa.cert_data)?;
Ok(())
}
/// [RFC 6698, DNS-Based Authentication for TLS](https://tools.ietf.org/html/rfc6698#section-2.2)
///
/// ```text
/// 2.2. TLSA RR Presentation Format
///
/// The presentation format of the RDATA portion (as defined in
/// [RFC1035]) is as follows:
///
/// o The certificate usage field MUST be represented as an 8-bit
/// unsigned integer.
///
/// o The selector field MUST be represented as an 8-bit unsigned
/// integer.
///
/// o The matching type field MUST be represented as an 8-bit unsigned
/// integer.
///
/// o The certificate association data field MUST be represented as a
/// string of hexadecimal characters. Whitespace is allowed within
/// the string of hexadecimal characters, as described in [RFC1035].
///
/// 2.3. TLSA RR Examples
///
/// In the following examples, the domain name is formed using the rules
/// in Section 3.
///
/// An example of a hashed (SHA-256) association of a PKIX CA
/// certificate:
///
/// _443._tcp.www.example.com. IN TLSA (
/// 0 0 1 d2abde240d7cd3ee6b4b28c54df034b9
/// 7983a1d16e8a410e4561cb106618e971 )
///
/// An example of a hashed (SHA-512) subject public key association of a
/// PKIX end entity certificate:
///
/// _443._tcp.www.example.com. IN TLSA (
/// 1 1 2 92003ba34942dc74152e2f2c408d29ec
/// a5a520e7f2e06bb944f4dca346baf63c
/// 1b177615d466f6c4b71c216a50292bd5
/// 8c9ebdd2f74e38fe51ffd48c43326cbc )
///
/// An example of a full certificate association of a PKIX end entity
/// certificate:
///
/// _443._tcp.www.example.com. IN TLSA (
/// 3 0 0 30820307308201efa003020102020... )
/// ```
impl fmt::Display for TLSA {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
write!(
f,
"{usage} {selector} {matching} {cert}",
usage = u8::from(self.cert_usage),
selector = u8::from(self.selector),
matching = u8::from(self.matching),
cert = sshfp::HEX.encode(&self.cert_data),
)
}
}
#[cfg(test)]
mod tests {
#![allow(clippy::dbg_macro, clippy::print_stdout)]
use super::*;
#[test]
fn read_cert_usage() {
assert_eq!(CertUsage::CA, CertUsage::from(0));
assert_eq!(CertUsage::Service, CertUsage::from(1));
assert_eq!(CertUsage::TrustAnchor, CertUsage::from(2));
assert_eq!(CertUsage::DomainIssued, CertUsage::from(3));
assert_eq!(CertUsage::Unassigned(4), CertUsage::from(4));
assert_eq!(CertUsage::Unassigned(254), CertUsage::from(254));
assert_eq!(CertUsage::Private, CertUsage::from(255));
assert_eq!(u8::from(CertUsage::CA), 0);
assert_eq!(u8::from(CertUsage::Service), 1);
assert_eq!(u8::from(CertUsage::TrustAnchor), 2);
assert_eq!(u8::from(CertUsage::DomainIssued), 3);
assert_eq!(u8::from(CertUsage::Unassigned(4)), 4);
assert_eq!(u8::from(CertUsage::Unassigned(254)), 254);
assert_eq!(u8::from(CertUsage::Private), 255);
}
#[test]
fn read_selector() {
assert_eq!(Selector::Full, Selector::from(0));
assert_eq!(Selector::Spki, Selector::from(1));
assert_eq!(Selector::Unassigned(2), Selector::from(2));
assert_eq!(Selector::Unassigned(254), Selector::from(254));
assert_eq!(Selector::Private, Selector::from(255));
assert_eq!(u8::from(Selector::Full), 0);
assert_eq!(u8::from(Selector::Spki), 1);
assert_eq!(u8::from(Selector::Unassigned(2)), 2);
assert_eq!(u8::from(Selector::Unassigned(254)), 254);
assert_eq!(u8::from(Selector::Private), 255);
}
#[test]
fn read_matching() {
assert_eq!(Matching::Raw, Matching::from(0));
assert_eq!(Matching::Sha256, Matching::from(1));
assert_eq!(Matching::Sha512, Matching::from(2));
assert_eq!(Matching::Unassigned(3), Matching::from(3));
assert_eq!(Matching::Unassigned(254), Matching::from(254));
assert_eq!(Matching::Private, Matching::from(255));
assert_eq!(u8::from(Matching::Raw), 0);
assert_eq!(u8::from(Matching::Sha256), 1);
assert_eq!(u8::from(Matching::Sha512), 2);
assert_eq!(u8::from(Matching::Unassigned(3)), 3);
assert_eq!(u8::from(Matching::Unassigned(254)), 254);
assert_eq!(u8::from(Matching::Private), 255);
}
fn test_encode_decode(rdata: TLSA) {
let mut bytes = Vec::new();
let mut encoder: BinEncoder<'_> = BinEncoder::new(&mut bytes);
emit(&mut encoder, &rdata).expect("failed to emit tlsa");
let bytes = encoder.into_bytes();
println!("bytes: {:?}", bytes);
let mut decoder: BinDecoder<'_> = BinDecoder::new(bytes);
let read_rdata =
read(&mut decoder, Restrict::new(bytes.len() as u16)).expect("failed to read back");
assert_eq!(rdata, read_rdata);
}
#[test]
fn test_encode_decode_tlsa() {
test_encode_decode(TLSA::new(
CertUsage::Service,
Selector::Spki,
Matching::Sha256,
vec![1, 2, 3, 4, 5, 6, 7, 8],
));
test_encode_decode(TLSA::new(
CertUsage::CA,
Selector::Full,
Matching::Raw,
vec![1, 2, 3, 4, 5, 6, 7, 8],
));
test_encode_decode(TLSA::new(
CertUsage::DomainIssued,
Selector::Full,
Matching::Sha512,
vec![1, 2, 3, 4, 5, 6, 7, 8],
));
test_encode_decode(TLSA::new(
CertUsage::Unassigned(40),
Selector::Unassigned(39),
Matching::Unassigned(6),
vec![1, 2, 3, 4, 5, 6, 7, 8],
));
}
}