Trust-DNS

A Rust based DNS client, server, and Resolver, built to be safe and secure from the ground up.

This repo consists of multiple crates:

Library	Description
Trust-DNS	Binaries for running a DNS authoritative server.
Proto	Raw DNS library, exposes an unstable API and only for use by the other Trust-DNS libraries, not intended for end-user use.
Client	Used for sending query, update, and notify messages directly to a DNS server.
Server	Use to host DNS records, this also has a named binary for running in a daemon form.
Resolver	Utilizes the client library to perform DNS resolution. Can be used in place of the standard OS resolution facilities.
Rustls	Implementation of DNS over TLS protocol using the rustls and ring libraries.
NativeTls	Implementation of DNS over TLS protocol using the Host OS' provided default TLS libraries
OpenSsl	Implementation of DNS over TLS protocol using OpenSSL

Goals

• Build a safe and secure DNS server and client with modern features.
• No panics, all code is guarded
• Use only safe Rust, and avoid all panics with proper Error handling
• Use only stable Rust
• Protect against DDOS attacks (to a degree)
• Support options for Global Load Balancing functions
• Make it dead simple to operate

Status:

Resolver

The Trust-DNS Resolver is a native Rust implementation for stub resolution in Rust applications. The Resolver supports many common query patterns, all of which can be configured when creating the Resolver. It is capable of using system configuration on Unix and Windows. On Windows there is a known issue that relates to a large set of interfaces being registered for use, so might require ignoring the system configuration.

The Resolver will properly follow CNAME chains as well as SRV record lookups. There is a long term plan to make the Resolver capable of fully recursive queries, but that's not currently possible.

Client

The Trust-DNS Client is intended to be used for operating against a DNS server directly. It can be used for verifying records or updating records for servers that support SIG0 and dynamic update. The Client is also capable of validating DNSSEC. As of now NSEC3 validation is not yet supported, though NSEC is. There are two interfaces that can be used, the async/await compatible AsyncClient and a blocking Client for ease of use. Today, Tokio is required for the executor Runtime.

Unique client side implementations

These are standards supported by the DNS protocol. The client implements them as high level interfaces, which is a bit more rare.

Feature	Description
SyncDnssecClient	DNSSec validation
create	atomic create of a record, with authenticated request
append	verify existence of a record and append to it
compare_and_swap	atomic (depends on server) compare and swap
delete_by_rdata	delete a specific record
delete_rrset	delete an entire record set
delete_all	delete all records sets with a given name
notify	notify server that it should reload a zone

Server

The server code is complete, the daemon supports IPv4 and IPv6, UDP and TCP. There currently is no way to limit TCP and AXFR operations, so it is still not recommended to put into production as TCP can be used to DOS the service. Master file parsing is complete and supported. There is currently no forking option, and the server is not yet threaded (although it is implemented with async IO, so threading may not be a huge benefit). There is still a lot of work to do before a server can be trusted with this externally. Running it behind a firewall on a private network would be safe.

Zone signing support is complete, to insert a key store a pem encoded rsa file in the same directory as the initial zone file with the .key suffix. Note: this must be only readable by the current user. If one is not present one will be created and written to the correct location. This also acts as the initial key for dynamic update SIG(0) validation. To get the public key, the DNSKEY record for the zone can be queried. This is needed to provide to other upstream servers to create the DS key. Dynamic DNS is also complete, if enabled, a journal file will be stored next to the zone file with the jrnl suffix. Note: if the key is changed or updated, it is currently the operators responsibility to remove the only public key from the zone, this allows for the DNSKEY to exist for some unspecified period of time during key rotation. Rotating the key currently is not available online and requires a restart of the server process.

DNS-over-TLS and DNS-over-HTTPS on the Server

Support of TLS on the Server is managed through a pkcs12 der file. The documentation is captured in the example test config file, example.toml. A registered certificate to the server can be pinned to the Client with the add_ca() method. Alternatively, as the client uses the rust-native-tls library, it should work with certificate signed by any standard CA.

DNS-over-TLS and DNS-over-HTTPS

DoT and DoH are supported. This is accomplished through the use of one of native-tls, openssl, or rustls (only rustls is currently supported for DoH). The Resolver requires only requires valid DoT or DoH resolvers being registered in order to be used.

To use with the Client, the TlsClientConnection or HttpsClientConnection should be used. Similarly, to use with the tokio AsyncClient the TlsClientStream or HttpsClientStream should be used. ClientAuth, mTLS, is currently not supported, there are some issues still being worked on. TLS is useful for Server authentication and connection privacy.

To enable DoT one of the features dns-over-native-tls, dns-over-openssl, or dns-over-rustls must be enabled, dns-over-https-rustls is used for DoH.

DNSSec status

Currently the root key is hardcoded into the system. This gives validation of DNSKEY and DS records back to the root. NSEC is implemented, but not NSEC3. Because caching is not yet enabled, it has been noticed that some DNS servers appear to rate limit the connections, validating RRSIG records back to the root can require a significant number of additional queries for those records.

Zones will be automatically resigned on any record updates via dynamic DNS. To enable DNSSEC, one of the features dnssec-openssl or dnssec-rustls must be enabled.

RFCs implemented

Basic operations

• RFC 1035: Base DNS spec (see the Resolver for caching)
• RFC 2308: Negative Caching of DNS Queries (see the Resolver)
• RFC 2782: Service location
• RFC 3596: IPv6
• RFC 6891: Extension Mechanisms for DNS
• RFC 6761: Special-Use Domain Names (resolver)
• RFC 6762: mDNS Multicast DNS (experimental feature: mdns)
• RFC 6763: DNS-SD Service Discovery (experimental feature: mdns)
• RFC ANAME: Address-specific DNS aliases (ANAME)

Update operations

• RFC 2136: Dynamic Update

Secure DNS operations

• RFC 3007: Secure Dynamic Update
• RFC 4034: DNSSEC Resource Records
• RFC 4035: Protocol Modifications for DNSSEC
• RFC 4509: SHA-256 in DNSSEC Delegation Signer
• RFC 5702: SHA-2 Algorithms with RSA in DNSKEY and RRSIG for DNSSEC
• RFC 6844: DNS Certification Authority Authorization (CAA) Resource Record
• RFC 6698: The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA
• RFC 6840: Clarifications and Implementation Notes for DNSSEC
• RFC 6844: DNS Certification Authority Authorization Resource Record
• RFC 6944: DNSKEY Algorithm Implementation Status
• RFC 6975: Signaling Cryptographic Algorithm Understanding
• RFC 7858: DNS over TLS (feature: dns-over-rustls, dns-over-native-tls, or dns-over-openssl)
• RFC DoH: DNS over HTTPS, DoH (feature: dns-over-https-rustls)

RFCs in progress or not yet implemented

Basic operations

• RFC 2317: Classless IN-ADDR.ARPA delegation

Update operations

• RFC 1995: Incremental Zone Transfer
• RFC 1996: Notify secondaries of update
• Update Leases: Dynamic DNS Update Leases
• Long-Lived Queries: Notify with bells

Secure DNS operations

• RFC 5155: DNSSEC Hashed Authenticated Denial of Existence
• DNSCrypt: Trusted DNS queries
• S/MIME: Domain Names For S/MIME

Usage

This assumes that you have Rust stable installed. These presume that the trust-dns repos have already been synced to the local system:

$ git clone https://github.com/bluejekyll/trust-dns.git
$ cd trust-dns

Prerequisites

Minimum Rust Version

• The current minimum rustc version for this project is 1.39
• OpenSSL development libraries (optional in client and resolver, min version 1.0.2)

Mac OS X: using homebrew

  $ brew install openssl
  $ export OPENSSL_INCLUDE_DIR=`brew --prefix openssl`/include
  $ export OPENSSL_LIB_DIR=`brew --prefix openssl`/lib

Debian-based (includes Ubuntu & Raspbian): using apt-get

  # note for openssl that a minimum version of 1.0.2 is required for TLS, 
  #  if this is an issue, TLS can be disabled (on the client), see below.
  $ apt-get install openssl
  $ apt-get install libssl-dev pkg-config

Testing

Trust-DNS uses cargo-make for build workflow management. While running cargo test at the project root will work, this is not exhaustive. Install cargo-make with cargo install cargo-make.

• Default tests

  These are good for running on local systems. They will create sockets for local tests, but will not attempt to access remote systems. Tests can also be run from the crate directory, i.e. client or server and cargo test

$ cargo make

• Default feature tests

  Trust-DNS has many features, to quickly test with them or without, there are three targets supported, default, no-default-features, all-features:

$ cargo make all-features

• Individual feature tests

  Trust-DNS has many features, each individual feature can be tested in dependently, see individual crates for all their features, here is a not necessarily up to date list: dns-over-rustls, dns-over-https-rustls, dns-over-native-tls, dns-over-openssl, dns-dnssec-openssl, dns-dnssec-openssl, dns-dnssec-ring, mdns. Each feature can be tested with itself as the task target for cargo-make:

$ cargo make dns-over-https-rustls

• Benchmarks

  Waiting on benchmarks to stabilize in mainline Rust.

Building

• Production build, from the trust-dns base dir, to get all features, just pass the --all-features flag.

$ cargo build --release -p trust-dns

Running

Warning: Trust-DNS is still under development, running in production is not recommended. The server is currently only single-threaded, it is non-blocking so this should allow it to work with most internal loads.

• Verify the version

$ ./target/release/named --version

• Get help

$ ./target/release/named --help

• Launch named server with test config

You may want not passing the -p parameter will run on default DNS ports. For the tls features, there are also port options for those, see trust-dns --help

$ ./target/release/named -c ./tests/test-data/named_test_configs/example.toml -z ./tests/test-data/named_test_configs/ -p 24141

• Query the just launched server with dig

$ dig @127.0.0.1 -p 24141 www.example.com

Using as a dependency and custom features

The Client has a few features which can be disabled for different reasons when embedding in other software.

• dnssec-openssl It is a default feature, so default-features will need to be set to false (this will disable all other default features in trust-dns). Until there are other crypto libraries supported, this will also disable DNSSec validation. The functions will still exist, but will always return errors on validation. The below example line will disable all default features and enable OpenSSL, remove "openssl" to remove the dependency on OpenSSL.

• dnssec-ring Ring support can be used for RSA and ED25519 DNSSec validation.

• dns-over-native-tls Uses native-tls for DNS-over-TLS implementation, only supported in client and resolver, not server.

• dns-over-openssl Uses openssl for DNS-over-TLS implementation supported in server and client, resolver does not have default CA chains.

• dns-over-rustls Uses rustls for DNS-over-TLS implementation, only supported in client and resolver, not server. This is the best option where a pure Rust toolchain is desired. Supported in client, resolver, and server.

• dns-over-https-rustls Uses rustls for DNS-over-HTTPS (and DNS-over-TLS will be enabled) implementation, only supported in client, resolver, and server. This is the best option where a pure Rust toolchain is desired.

• mdns EXPERIMENTAL Enables the experimental mDNS features as well as DNS-SD. This currently has known issues.

Using custom features in dependencies:

[dependencies]
  ...
trust-dns = { version = "*", default-features = false, features = ["dnssec-openssl"] }

Using custom features during build:

$> cargo build --release --features dns-over-rustls
...

FAQ

• Why are you building another DNS server?

  Because of all the security advisories out there for BIND. Using Rust semantics it should be possible to develop a high performance and safe DNS Server that is more resilient to attacks.

Community

For live discussions beyond this repository, please see this Discord.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.