created_at2024-03-28 08:04:17.82337
updated_at2024-03-28 08:04:17.82337
descriptionRustls is a modern TLS library written in Rust. This is clia-mod using ring.
clia (clia)



Rustls is a modern TLS library written in Rust.


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 accomodate 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

Build Status Coverage Status ( Documentation Chat


The detailed list of changes in each release can be found at



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, by default it uses aws-lc-rs for implementing the cryptography in TLS. See the aws-lc-rs FAQ for more details of the platform/architecture support constraints in aws-lc-rs.

ring is also available via the ring crate feature: see the supported ring target platforms.

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.

Specifying default-features = false when depending on rustls will remove the dependency on aws-lc-rs.

Rustls requires Rust 1.61 or later.

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 that aren't met by the default provider, aws-lc-rs.

Users that wish to customize the provider in use can do so when constructing ClientConfig and ServerConfig instances using the with_crypto_provider method on the respective config builder types. See the crypto::CryptoProvider documentation for more details.

Built-in providers

Rustls ships with two built-in providers controlled with associated feature flags:

  • aws-lc-rs - enabled by default, available with the aws_lc_rs feature flag enabled.
  • ring - available with the ring feature flag enabled.

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

Third-party providers

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

Custom provider

We also provide a simple example of writing your own provider in the custom-provider example. This example implements a minimal provider using parts of the RustCrypto ecosystem.

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

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.

Client example program

The MIO client example program is named tlsclient-mio. The interface looks like:

Connects to the TLS server at hostname:PORT.  The default PORT
is 443.  By default, this reads a request from stdin (to EOF)
before making the connection.  --http replaces this with a
basic HTTP GET request for /.

If --cafile is not supplied, a built-in set of CA certificates
are used from the webpki-roots crate.

  tlsclient-mio [options] [--suite SUITE ...] [--proto PROTO ...] [--protover PROTOVER ...] <hostname>
  tlsclient-mio (--version | -v)
  tlsclient-mio (--help | -h)

    -p, --port PORT     Connect to PORT [default: 443].
    --http              Send a basic HTTP GET request for /.
    --cafile CAFILE     Read root certificates from CAFILE.
    --auth-key KEY      Read client authentication key from KEY.
    --auth-certs CERTS  Read client authentication certificates from CERTS.
                        CERTS must match up with KEY.
    --protover VERSION  Disable default TLS version list, and use
                        VERSION instead.  May be used multiple times.
    --suite SUITE       Disable default cipher suite list, and use
                        SUITE instead.  May be used multiple times.
    --proto PROTOCOL    Send ALPN extension containing PROTOCOL.
                        May be used multiple times to offer several protocols.
    --no-tickets        Disable session ticket support.
    --no-sni            Disable server name indication support.
    --insecure          Disable certificate verification.
    --verbose           Emit log output.
    --max-frag-size M   Limit outgoing messages to M bytes.
    --version, -v       Show tool version.
    --help, -h          Show this screen.

Some sample runs:

$ cargo run --bin tlsclient-mio -- --http
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


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

Server example program

The MIO server example program is named tlsserver-mio. The interface looks like:

Runs a TLS server on :PORT.  The default PORT is 443.

`echo' mode means the server echoes received data on each connection.

`http' mode means the server blindly sends a HTTP response on each

`forward' means the server forwards plaintext to a connection made to

`--certs' names the full certificate chain, `--key' provides the
RSA private key.

  tlsserver-mio --certs CERTFILE --key KEYFILE [--suite SUITE ...] [--proto PROTO ...] [--protover PROTOVER ...] [options] echo
  tlsserver-mio --certs CERTFILE --key KEYFILE [--suite SUITE ...] [--proto PROTO ...] [--protover PROTOVER ...] [options] http
  tlsserver-mio --certs CERTFILE --key KEYFILE [--suite SUITE ...] [--proto PROTO ...] [--protover PROTOVER ...] [options] forward <fport>
  tlsserver-mio (--version | -v)
  tlsserver-mio (--help | -h)

    -p, --port PORT     Listen on PORT [default: 443].
    --certs CERTFILE    Read server certificates from CERTFILE.
                        This should contain PEM-format certificates
                        in the right order (the first certificate should
                        certify KEYFILE, the last should be a root CA).
    --key KEYFILE       Read private key from KEYFILE.  This should be a RSA
                        private key or PKCS8-encoded private key, in PEM format.
    --ocsp OCSPFILE     Read DER-encoded OCSP response from OCSPFILE and staple
                        to certificate.  Optional.
    --auth CERTFILE     Enable client authentication, and accept certificates
                        signed by those roots provided in CERTFILE.
    --crl CRLFILE ...   Perform client certificate revocation checking using the DER-encoded
                        CRLFILE. May be used multiple times.
    --require-auth      Send a fatal alert if the client does not complete client
    --resumption        Support session resumption.
    --tickets           Support tickets.
    --protover VERSION  Disable default TLS version list, and use
                        VERSION instead.  May be used multiple times.
    --suite SUITE       Disable default cipher suite list, and use
                        SUITE instead.  May be used multiple times.
    --proto PROTOCOL    Negotiate PROTOCOL using ALPN.
                        May be used multiple times.
    --verbose           Emit log output.
    --version, -v       Show tool version.
    --help, -h          Show this screen.

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/end.fullchain --key test-ca/rsa/end.rsa -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
$ echo hello world | cargo run --bin tlsclient-mio -- --cafile test-ca/rsa/ca.cert -p 8443 localhost
hello world


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 - full-time funded by Prossimo)
  • Josh Aas (@bdaehlie, Project Management)

Code of conduct

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

Commit count: 3043

cargo fmt