In May and June 2020, Cure53 completed an audit of ring , webpki , and rustls . Their report ( PDF ) fully describes the audit, and makes for interesting reading.
First off, though, Dirkjan Ochtman (of the Quinn project) deserves a great deal of thanks for ultimately making this happen. We first discussed the possibility of an audit like this at RustFest Paris 2018. He worked with great determination for almost two years to secure a sponsor. Thanks Dirkjan!
The Cloud Native Computing Foundation (a part of the Linux Foundation) funded this audit, at the request of Buoyant who use rustls in the data plane of linkerd . So further thanks are due to Chris Aniszczyk of the Linux Foundation, and Oliver Gould of Buoyant for their support of these projects.