s2n

s2n is an open-source TLS/SSL library developed by Amazon Web Services. It provides a production-ready implementation of the TLS protocol designed to be small, fast, and auditable. The project is written in portable C (C99) and aims to minimize dependencies while presenting a straightforward API for both client and server applications.

Key features and design goals include support for TLS 1.2 and TLS 1.3, modern cipher suites, and common TLS capabilities such as ALPN, certificate verification, and session resumption through tickets and PSK. The architecture emphasizes readability and security, offering a modular structure and a clean cryptographic interface intended to simplify auditing and verification. s2n is designed to be suitable for use in embedded environments as well as larger services, with an emphasis on a small surface area and predictable behavior.

License and ecosystem: s2n is released under the Apache 2.0 license and is distributed with documentation, tests, and tooling to facilitate integration and evaluation. The project is maintained by AWS with broad community involvement through its GitHub repository, including contributions, issue tracking, and ongoing development.

Security posture and testing: the project emphasizes security through comprehensive test suites, fuzzing campaigns, and code quality reviews. Its emphasis on simplicity and auditable code is intended to reduce the risk of undiscovered vulnerabilities relative to larger, more complex TLS stacks.

Usage and scope: s2n provides a runnable alternative to other TLS implementations for developers seeking a lean, auditable TLS library. While it covers core TLS functionality, users should assess feature parity and integration needs against their specific deployment requirements.