The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Monday, August 06, 2018

It seems that checking the TLS API version number is useless

I've pretty much finished the Lua TLS module and before releasing it, I thought it might be nice to ensure it compiles with previous versions of libtls. The main header file contains the defined value TLS_API, which I assume is updated whenever the API is updated. So I began the arduous procedure of downloading previous versions of libtls to ensure I can compile against any version.

I started with LibreSSL version 2.7.4 (current when I started—they are now up to 2.8.0 as I write this). The defined value TLS_API had a value of “20180210”. I checked version 2.7.0 and no change in libtls. It wasn't until I got into the pre-2.7 versions that things started going south.

The previous version of TLS_API, “20170126”, was first defined in 2.5.1, and last used in 2.6.5. But the API changed quite a bit between versions 2.5.1 and 2.6.5. Five functions were added:

  1. tls_config_set_crl_file()
  2. tls_config_set_crl_mem()
  3. tls_config_set_ecdhecurves()
  4. tls_peer_cert_chain_pem()
  5. tls_unload_file()

What's the point of having a defined value like TLS_API if it doesn't change when you add new functions?

Fortunately, the defined value LIBRESSL_VERSION_NUMBER is updated per version, so at least I can use that.


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