NGINX App Protect v5 Signature Notifications

When working with NAP (NGINX App Protect) you don't have an easy way of knowing when any of the signatures are updated.

As an old BigIP guy I find that rather strange. Here you have build-in automatic updates and notifications.

Unfortunately there isn't any API's you can probe which would have been the best way of doing it. Hopefully it will come one day.

 

However, "friction" and "hard" will not keep me from finding a solution 😆

 

I have previously made a solution for NAPv4 and I have tried mentally to get me going on a NAPv5 version. The reason for the delay is in the different way NAPv4 and NAPv5 are designed. Where NAPv4 is one module loaded in NGINX, NAPv5 is completely detached from NGINX (well almost, you still need to load a small module to get the traffic from NGINX to NAP) and only works with containers.

NAPv5 has moved the signature "storage" from the actual host it is running on (e.g. an installed package) to the policy. This has the consequence that finding a valid "source of truth", for the latest signature versions, is not as simple as building a new image and see which versions got installed.

There are very good reasons for this design that I will come back to later.

When you fire up NAPv5 you got three containers for the data plane (NGINX, waf-enforcer and waf-config-mgr) and one for the "control plane" (waf-compiler). For this solution the "control plane" is the useful one. It isn't really a control plane but it gives a nice picture of how it is detached from the actual processing of traffic.

When you update your signatures you are actually doing it through the waf-compiler. The waf-compiler is a container hosting the actual signature databases and every time a new verison is released you need to rebuild this container and compile your policies into a new version and reload NGINX.

And this is what I take advantage of when I look for signature updates. It has the upside that you only need the waf-compiler to get the information you need. My solution will take care of the entire process and make sure that you are always running with the latest signatures.

Back to the reason why the split of functions is a very good thing. When you build a new version of the NGINX image and deploy it into production, NAP needs to compile the policies as they load. During the compilation NGINX is not moving any traffic! This becomes a annoying problem even when you have a low number of policies. I have installations where it takes 5 to 10 minutes from deployment of the new image until it starts moving traffic. That is a crazy long time when you are used to working with micro-services and expect everything to flip within seconds. If you have your NAPv4 hooked up to a NGINX Instance Manager (NIM) the problem is somewhat mitigated as NIM will compile the policies before sending them to the gateways. NIM is not a nimble piece of software so it doesn't always fit into the environment.

 

And now here is my hack to the notification problem:

The solution consist of two bash scripts and one html template. The template is used when sending a notification mail. I wanted it to be pretty and that was easiest with html. Strictly speaking you could do with just a simple text based mail.

Save all three in the same directory.

The main script is called "waf_policy_auto_compile.sh"and is the one you put into crontab.

The main script will build a new waf-compiler image and compile a test policy. The outcome of that is information about what versions are the newest. It will then extract versions from an old policy and simply see if any of the versions differ. For this to work you need to have an uncompiled policy (you can just use the default one) and a compiled version of it ready beforehand.

 

When a diff has been identified the notification logic is executed and a second script is called: "compile_waf_policies.sh".

It basically just trawls through the directory of you policies and logging profiles and compiles a new version of them all. It is not necessary to recompile the logging profiles, so this will probably change in the next version.

 

As the compilation completes the main script will nudge NGINX to reload thus implement all the new versions.

You can run "waf_policy_auto_compile.sh" with a verbose flag (-v) and a debug flag (-d). The verbose flag is intended to be used when you run it on a terminal and want the information displayed there. Debug is, well, for debug 😝 

The construction of the scripts are based on my own needs but they should be easy to adjust for any need.

I will be happy for any feedback, so please don't hold back 😄