Petter Reinholdtsen

Secure Socket API - a simple and powerful approach for TLS support in software
6th June 2020

As a member of the Norwegian Unix User Group, I have the pleasure of receiving the USENIX magazine ;login: several times a year. I rarely have time to read all the articles, but try to at least skim through them all as there is a lot of nice knowledge passed on there. I even carry the latest issue with me most of the time to try to get through all the articles when I have a few spare minutes.

The other day I came across a nice article titled "The Secure Socket API: TLS as an Operating System Service" with a marvellous idea I hope can make it all the way into the POSIX standard. The idea is as simple as it is powerful. By introducing a new socket() option IPPROTO_TLS to use TLS, and a system wide service to handle setting up TLS connections, one both make it trivial to add TLS support to any program currently using the POSIX socket API, and gain system wide control over certificates, TLS versions and encryption systems used. Instead of doing this:

int socket = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);

the program code would be doing this:

int socket = socket(PF_INET, SOCK_STREAM, IPPROTO_TLS);

According to the ;login: article, converting a C program to use TLS would normally modify only 5-10 lines in the code, which is amazing when compared to using for example the OpenSSL API.

The project has set up the web site to spread the idea, and the code for a kernel module and the associated system daemon is available from two github repositories: ssa and ssa-daemon. Unfortunately there is no explicit license information with the code, so its copyright status is unclear. A request to solve this about it has been unsolved since 2018-08-17.

I love the idea of extending socket() to gain TLS support, and understand why it is an advantage to implement this as a kernel module and system wide service daemon, but can not help to think that it would be a lot easier to get projects to move to this way of setting up TLS if it was done with a user space approach where programs wanting to use this API approach could just link with a wrapper library.

I recommend you check out this simple and powerful approach to more secure network connections. :)

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Tags: debian, english, sikkerhet, sysadmin.

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