[OpenSIPS-Devel] Re-organizing and de-duplicating digest code (related to the RFC8760 work)

[Liviu Chircu]

On 08.10.2020 05:42, Maxim Sobolev wrote:
> Hey folks,
Hi!
> The problem that I am hitting now is that we have digest computation 
> code duplicated in both modules (auth vs. uac_auth), which of course 
> is less than ideal from many perspectives (2x code to test, code 
> bloat, pain to add more algorithms etc).
I agree that the uac / uac_auth code is a bit "all over the place" and 
could use some re-org into a single "authentication-related" module / 
directory / library.
>
> Now the question is what is the best way to deal with it. Couple of 
> options I have:
>
> 1. Make uas_auth use code from the auth module and add it as a 
> dependency. In general this seems to be the path the project takes to 
> solve this problem. The downside is perhaps some small performance 
> degradation as well some overhead to define and maintain API. Also 
> this method does not work for smallish bits and pieces, too 
> heavy-weight for an API.
Classical module API approach - let's see if we can do better.
>
> 2. Move code into the core. I think this is probably the wrong 
> direction, some application might not need auth at all. Just listing 
> it for completeness sake.
I agree - no need to compile this code into the "opensips" binary if the 
app only does IP authentication, for example.
> 3. Move code into some kind of internal static library (say 
> "libospcore.a") and link both modules against that library. I really 
> like this approach since apart from some make-foo to get the library 
> compiled and linked with each of modules, the rest is pretty much 
> trivial. This avoids API/dependency overhead. With things like 
> link-time-optimization becoming de-facto standard in the next 2-3 
> years would give the best possible performance with very small size 
> overhead. Also works great for useful functions that are too small for 
> an API (for example function to convert binary into hex and the likes).

I like this approach best, but let me suggest an improvement!  If you 
place the code under and extra directory level, e.g. in *lib/auth/* 
instead of just *lib/*, /it will not compile by default!/ This way, any 
modules requiring digest auth-related DS and functions will simply 
include the *lib/auth/auth.h* header and have everything they need.  See 
the /modules/registrar/Makefile/ for an example of how to include some 
"extra core source code" into your module.

-- 
Liviu Chircu
www.twitter.com/liviuchircu | www.opensips-solutions.com

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