Posted by Tobias Thierer, Software Engineer
To improve security, insecure TLS version fallback has been removed from HttpsURLConnection in Android O.
What is changing and why?
We are removing this workaround because it weakens TLS by disabling TLS protocol version downgrade protections. The workaround is no longer needed, because fewer than 0.01% of web servers relied on it as of late 2015.
Will my app be affected?
- Target web servers that work with recent versions of Chrome or Firefox, because those servers have correctly implemented TLS protocol version negotiation. Support for TLS version fallback was removed in Firefox 37 (Mar 2015) and Chrome 50 (Apr 2016).
- Use a third-party HTTP library not built on top of HttpsURLConnection. We suggest you disable protocol fallback if you're using a third-party library. For example, in OkHttp versions up to 3.6, you may want to configure your OkHttpClient to only use ConnectionSpec.MODERN_TLS.