Strictly speaking, Botan is a general-purpose crypto library, but has a TLS implementation. Source is kept in Monotone, but there is a Github mirror. Botan has had continuous development since 2001. Is it safe to use in a commercial product? Good question.
It builds on Unix/POSIX and Microsoft Windows. There are instructions for both iOS and Android builds referenced in the documentation.
- Wikipedia - Botan
- SSL implementations compared - although this is really about coding style.
- Stack Overflow - Looking for a High Level C++ SSL Library
- Speedtest and Comparsion of Open-Source Cryptography Libraries and Compiler Flags - by the author of CryptoTE.
- SSL and TLS - sample from old Botan manual
- Botan’s Implementation of the McEliece PKC - cryptography resilient against quantum computers?
- Building the Botan library for ios7 arm64
LibreSSL is a fork of OpenSSL done by the OpenBSD folks as a security-focused rewrite. There is a new library coming called ressl, for reimagined SSL.
Secure Channel or Schannel is the name of Microsoft’s SSL implementation, implemented as an SSP in their Security Support Provider Interface.
- Secure Channel
- Certificate Stores
- SSL/TLS Alert Protocol & the Alert Codes
- Cryptography API: Next Generation
- CSslSocket - SSL/TLS enabled CSocket
- SSL in WinHTTP
- How to add SNI client hello extension using Schannel API?
- SSL with WinHTTP
- Manually Validating Schannel Credentials
- CryptoAPI Cryptographic Service Providers
Secure Transport is Darwin/Mac OS X’s name for SSL. Modern features are only supported in Mac OS X 10.8 or later. Also annoyingly, you must put certificates in the Keychain instead of bundling them with your program. But it’s open source under the APSL 2.0 license.
Wikipedia - Comparison of TLS implementations
Note to self - don’t allow SSL renegotiation. Re: SSL renegotiation