Rustls is a modern TLS library written in Rust.

Status

Rustls is used in production at many organizations and projects. We aim to maintain
reasonable API surface stability but the API may evolve as we make changes to accommodate
new features or performance improvements.

We have a roadmap for our future plans. We also have benchmarks to
prevent performance regressions and to let you evaluate rustls on your target hardware.

If you'd like to help out, please see CONTRIBUTING.md.


The maintainers pronounce "rustls" as rustles (rather than rust-TLS), but we don't feel strongly
about it.

Changelog

The detailed list of changes in each release can be found at
https://github.com/rustls/rustls/releases.

Documentation

https://docs.rs/rustls/

Approach

Rustls is a TLS library that aims to provide a good level of cryptographic security,
requires no configuration to achieve that security, and provides no unsafe features or
obsolete cryptography by default.

Rustls implements TLS1.2 and TLS1.3 for both clients and servers. See the full
list of protocol features.

Platform support

While Rustls itself is platform independent, it requires the use of cryptography primitives
for implementing the cryptography algorithms used in TLS. In Rustls, a
[crypto::CryptoProvider] represents a collection of crypto primitive implementations.

By providing a custom instance of the [crypto::CryptoProvider] struct, you
can replace all cryptography dependencies of rustls. This is a route to being portable
to a wider set of architectures and environments, or compliance requirements. See the
[crypto::CryptoProvider] documentation for more details.

[crypto::CryptoProvider]: https://docs.rs/rustls/latest/rustls/crypto/struct.CryptoProvider.html

Cryptography providers

Since Rustls 0.22 it has been possible to choose the provider of the cryptographic primitives
that Rustls uses. This may be appealing if you have specific platform, compliance or feature
requirements.

From 0.24, users must explicitly provide a crypto provider when constructing ClientConfig or
ServerConfig instances. See the [crypto::CryptoProvider] documentation for more details.

First-party providers

The Rustls project currently maintains two cryptography providers:

• [rustls-aws-lc-rs] - a provider that uses the [aws-lc-rs] crate for cryptography.

While this provider can be harder to build on [some platforms][aws-lc-rs-platforms-faq], it provides excellent performance and a complete feature set (including post-quantum algorithms).

• [rustls-ring] - a provider that uses the [ring] crate for cryptography. This

provider is easier to build on a variety of platforms, but has a more limited feature set (for example, it does not support post-quantum algorithms).

The Rustls team recommends using the [rustls-aws-lc-rs] crate for its complete feature set
and performance. See [the aws-lc-rs FAQ][aws-lc-rs-platforms-faq] for more details of the
platform/architecture support constraints in aws-lc-rs.

See the documentation for [crypto::CryptoProvider] for details on how providers are
selected.

(For rustls versions prior to 0.24, both of these providers were shipped as part of the rustls
crate, and Cargo features were used to select the preferred provider. The aws-lc-rs feature
was enabled by default.)

[rustls-aws-lc-rs]: https://crates.io/crates/rustls-aws-lc-rs
[aws-lc-rs]: https://crates.io/crates/aws-lc-rs
[aws-lc-rs-platforms-faq]: https://aws.github.io/aws-lc-rs/faq.html#can-i-run-aws-lc-rs-on-x-platform-or-architecture
[rustls-ring]: https://crates.io/crates/rustls-ring
[ring]: https://crates.io/crates/ring

Third-party providers

The community has also started developing third-party providers for Rustls:

• [boring-rustls-provider] - a work-in-progress provider that uses [boringssl] for

cryptography.

• [rustls-ccm] - adds AES-CCM cipher suites (TLS 1.2 and 1.3) using [RustCrypto], for IoT/constrained-device protocols (IEEE 2030.5, Matter, RFC 7925).
• [rustls-graviola] - a provider that uses [graviola] for cryptography.
• [rustls-mbedtls-provider] - a provider that uses [mbedtls] for cryptography.
• [rustls-openssl] - a provider that uses [OpenSSL] for cryptography.
• [rustls-rustcrypto] - an experimental provider that uses the crypto primitives

from [RustCrypto] for cryptography.

• [rustls-symcrypt] - a provider that uses Microsoft's [SymCrypt] library.
• [rustls-wolfcrypt-provider] - a work-in-progress provider that uses [wolfCrypt] for cryptography.

[rustls-ccm]: https://github.com/jsulmont/rustls-ccm [rustls-graviola]: https://crates.io/crates/rustls-graviola [graviola]: https://github.com/ctz/graviola [rustls-mbedtls-provider]: https://github.com/fortanix/rustls-mbedtls-provider [mbedtls]: https://github.com/Mbed-TLS/mbedtls [rustls-openssl]: https://github.com/tofay/rustls-openssl [OpenSSL]: https://openssl-library.org/ [rustls-symcrypt]: https://github.com/microsoft/rustls-symcrypt [SymCrypt]: https://github.com/microsoft/SymCrypt [boring-rustls-provider]: https://github.com/janrueth/boring-rustls-provider [boringssl]: https://github.com/google/boringssl [rustls-rustcrypto]: https://github.com/RustCrypto/rustls-rustcrypto [RustCrypto]: https://github.com/RustCrypto [rustls-wolfcrypt-provider]: https://github.com/wolfSSL/rustls-wolfcrypt-provider [wolfCrypt]: https://www.wolfssl.com/products/wolfcrypt

See the [Making a custom CryptoProvider] section of the documentation for more information
on this topic.

[Making a custom CryptoProvider]: https://docs.rs/rustls/latest/rustls/crypto/struct.CryptoProvider.html#making-a-custom-cryptoprovider

Example code

Our [examples] directory contains demos that show how to handle I/O using the
[stream::Stream] helper, as well as more complex asynchronous I/O using [mio].
If you're already using Tokio for an async runtime you may prefer to use
[tokio-rustls] instead of interacting with rustls directly.

The [mio] based examples are the most complete, and discussed below. Users
new to Rustls may prefer to look at the simple client/server examples before
diving in to the more complex MIO examples.

[examples]: examples/
[stream::Stream]: https://docs.rs/rustls/latest/rustls/struct.Stream.html
[mio]: https://docs.rs/mio/latest/mio/
[tokio-rustls]: https://docs.rs/tokio-rustls/latest/tokio_rustls/

Client example program

The MIO client example program is named tlsclient-mio.

Some sample runs:

$ cargo run --bin tlsclient-mio -- --http mozilla-modern.badssl.com
HTTP/1.1 200 OK
Server: nginx/1.6.2 (Ubuntu)
Date: Wed, 01 Jun 2016 18:44:00 GMT
Content-Type: text/html
Content-Length: 644
(...)

or

$ cargo run --bin tlsclient-mio -- --http expired.badssl.com
TLS error: InvalidCertificate(Expired)
Connection closed

Run cargo run --bin tlsclient-mio -- --help for more options.

Server example program

The MIO server example program is named tlsserver-mio.

Here's a sample run; we start a TLS echo server, then connect to it with
openssl and tlsclient-mio:

$ cargo run --bin tlsserver-mio -- --certs test-ca/rsa-2048/end.fullchain --key test-ca/rsa-2048/end.key -p 8443 echo &
$ echo hello world | openssl s_client -ign_eof -quiet -connect localhost:8443
depth=2 CN = ponytown RSA CA
verify error:num=19:self signed certificate in certificate chain
hello world
^C
$ echo hello world | cargo run --bin tlsclient-mio -- --cafile test-ca/rsa-2048/ca.cert --port 8443 localhost
hello world
^C

Run cargo run --bin tlsserver-mio -- --help for more options.

License

Rustls is distributed under the following three licenses:

• Apache License version 2.0.
• MIT license.
• ISC license.

These are included as LICENSE-APACHE, LICENSE-MIT and LICENSE-ISC respectively. You may use this software under the terms of any of these licenses, at your option.

Project Membership

• Joe Birr-Pixton ([@ctz], Project Founder - full-time funded by [Prossimo])
• Dirkjan Ochtman ([@djc], Co-maintainer)
• Daniel McCarney ([@cpu], Co-maintainer)
• Josh Aas ([@bdaehlie], Project Management)

[@ctz]: https://github.com/ctz [@djc]: https://github.com/djc [@cpu]: https://github.com/cpu [@bdaehlie]: https://github.com/bdaehlie [Prossimo]: https://www.memorysafety.org/initiative/rustls/

Code of conduct

This project adopts the Rust Code of Conduct.
Please email [email protected] to report any instance of misconduct, or if you
have any comments or questions on the Code of Conduct.

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