 | |
| Developer(s) | Joe Birr-Pixton, Dirkjan Ochtman, Daniel McCarney, Josh Aas[1] |
|---|---|
| Initial release | 2016 |
| Stable release | v0.23.25 (March 17, 2025; 33 days ago (2025-03-17)[2]) [±] |
| Repository | |
| Written in | Rust |
| Operating system | Cross-platform |
| Type | Security library |
| License | Apache 2.0,MIT,ISC[1] |
| Website | github |
Rustls (pronounced "rustles"[3]) is anopen-source implementation of theTransport Layer Security (TLS)cryptographic protocol written in theRust programming language. TLS is essential tointernet security, and Rustls aims to enablesecure,fast TLS connections. Rustls uses Rust's enforcement ofmemory safety to reduce the risk ofsecurity vulnerabilities. It is part of efforts to improve internet security by replacing memory-unsafesoftware libraries, such asOpenSSL, with memory-safe alternatives.
Joe Birr-Pixton started Rustls in 2016 and remains the lead developer as of 2024.[1] TheInternet Security Research Group (ISRG), anonprofit organization based in the United States, has sponsored the project since 2021 as part of its Prossimo initiative.[4][5] ISRG aims to make Rustls a viable alternative toOpenSSL, which is widely used byinternetservers but difficult to use correctly and has hadsecurity bugs, such asHeartbleed, caused by memory-unsafe code.[4][6]
ISRG has paid severalprogrammers to work on Rustls, including Birr-Pixton, Daniel McCarney, and Dirkjan Ochtman, using money contributed byGoogle and other companies and organizations.[4][7] In 2023, theOpen Source Security Foundation's Alpha-Omega initiative gave ISRG $530,000 for development of the option to use different cryptographic backends and for the separate projectRust for Linux.[8][9] That money came from Google,Amazon Web Services, andMicrosoft.[10] Amazon Web Services also gave ISRG $1 million in 2023 for memory-safety projects including Rustls.[11] TheSovereign Tech Fund, supported by the German government, gave $1.5 million to ISRG in 2023 for work on Rustls and other projects that provide memory-safe versions of open source tools critical to internet security.[12][13]Craig Newmark Philanthropies granted $100,000 to ISRG for memory safety projects in 2024.[14] Additional funding has come from Fly.io,[15] acloud platform that uses Rustls.[16]
The United StatesOffice of the National Cyber Director has encouraged work on memory-safe security software[17] and complimented the Rustls team.[15] Google awarded Open Source Peer Bonuses to Birr-Pixton and Ochtman for their work on Rustls.[18]
Rustls is alow-level softwarelibrary focused onTLS implementation.[19] This means it does not support otherinternet protocols by itself, such asHTTPS, but software that implements other protocols may use Rustls as a component.[19]
By default Rustls usescryptographic primitives from Amazon Web Services Libcrypto for Rust (aws-lc-rs), which supportsFederal Information Processing Standards (FIPS).[20] Rustls allows using alternative cryptographic libraries instead ofaws-lc-rs, such asring.[20] The project has experimental support forpost-quantum cryptography: akey exchange method with a specialkey encapsulation mechanism (Kyber).[21]
Rustls uses its ownfork of thewebpki library to verifypublic key infrastructurecertificates, a step in theTLS handshake.[3][22] Rustls supportsServer Name Indication (SNI), which allows aweb server to serve multiple HTTPS websites at the sameIP address with different certificates.[23] It also supports TLS certificates that contain IP addresses instead ofdomain names.[24]
C programs can use Rustls through aforeign function interfaceAPI,rustls-ffi.[3][6] For example,cURL is a popular tool written in C, and it allows using Rustls throughrustls-ffi.[25][26] Rustls also has an OpenSSLcompatibility layer that allows configuring the widely-usedNginx web server to use Rustls instead of OpenSSL.[15][27]
Rustls is available under multiplefree software licenses:Apache 2.0,MIT, andISC.[1]
In 2020, theCloud Native Computing Foundation funded asecurity audit of Rustls and two Rust libraries it used,ring andwebpki, with positive results.[28]
In 2019,benchmarks carried out by the Rustls developer showed betterperformance thanOpenSSL.[29] In 2024 the project conducted new performance comparisons with the latest version of OpenSSL, which showed some scenarios where Rustls was faster or more efficient and some where OpenSSL performed better.[30]
Like other TLS implementations, acomputer user may use Rustls without being aware of it, as an underlying part of an application or website. A programmer can use Rustls directly or by configuring a higher-level library or tool to use it. In particular, Rustls is used by some projects that want to ensure they have a securesoftware supply chain.[31] The USCybersecurity and Infrastructure Security Agency has recommended using products in memory safe languages as part of its "Secure by Design" initiative.[32]
Some libraries support Rustls as one of several choices for TLS implementations. ThereqwestHTTP client library offers the option to use Rustls for TLS instead of the system's default TLS library (for example, onWindows the default is theSecurity Support Provider Interface).[33][34] In 2020 an ISRG software engineer enabled using Rustls as a TLS backend forcURL.[35][36]s2n-quic, an implementation of theQUICnetwork protocol in Rust, supports both Rustls ands2n-tls for TLS.[37]
In 2021Google funded the creation ofmod_tls, a new TLSmodule forApache HTTP Server using Rustls.[38][39] The new module is intended to be a successor to themod_ssl module that uses OpenSSL, as a more secure default.[38][40] As of August 2024,mod_tls is available in the latest version of Apache but still marked as experimental.[41] TheInternet Society, a nonprofit that advocates for an open and secureinternet, suggests that organizations use this module as a step toward increasing memory safety.[42]
Rustls is the default TLS implementation in some applications. The utility programcargo_audit, which checks Rust project dependencies for security vulnerabilities, uses Rustls.[43]Linkerd, which "adds security,observability, and reliability to anyKubernetes cluster", includes aproxy server built with Rustls.[44] Wolfi, a tool for making memory-safeLinuxcontainers, uses Rustls.[45][46] In 2024, ISRG announced plans to start replacing OpenSSL with Rustls inLet's Encrypt, their freecertificate authority used by hundreds of millions of websites.[15][47]
