Securing a sensitive variable in Azure DevOps


I’m a newbie at Azure DevOps. They sort of have to drag me kicking and screaming to give up the comfort of my personal linux to endure the torture of learning something brand new. But I iguess that’s the new way so I gotta go along with it. I work within a project that has a repo. And we intend to run a pipeline. Question is, how to deal with sensitive parameters like passwords?

One approach

If you just do raw Internet searches you can fall into any number of rabbit holes. Key vault, anyone? How about relying on secure files within the library? I guess – very tentatively – that using a key vault might be the right way to deal with this issue, but it all depends on the ACLs available and I do not know that.. I also do not see a simple-minded way to set up a key vault. So what the guy who seems to know a lot more than I do is to set up a hidden variable for the pipeline itself.

The thing is that even that has its own gotchas. I find that depending on where you start from, you may ior may not see the option to declare a pipline variable as hidden.

If I am in the Pipeline section and looking at Recently Run Pipelines, and click on my pipeline, before I run it I can add variables. Doing it that way, you only get the option to include a name and Value. No option for declaring it to be hidden.

So how do you do it?

Instead of Run Pipline > variables go to Edit Pipeline > Variables. Then variables you create will have the option to be kept secret.

It is a bad idea to pass a sensitive information on the command line. Anyone with access to that agent could do a process listing to read the secret. So instead you use an environment variable. It’s a little tricky as you have to understand yaml variable interpolation versus script interpolation.

My secret variable is auth_token for the Zabbix api token. So in my yaml file I have a reference to it which sets up an environment variable:

- script: python Delete_Unused_VEdges/ 'SA'
  displayName: 'Run script'
    AUTH_TOKEN: $(auth_token)

And in I read that environment variable like this:

token_zabbix = os.environ['AUTH_TOKEN']

And, voila, it’s all good.

But how secure is it really?

Question is, is this just performative security? Because I’m working with a project. Anyone else with access to the project could alter my python program temporarily to print out the value of the secret variable. I’m assuming they can both alter the repo I use as well as run a pipeline. Yes, they make it a tiny bit challenging because you need to break up a secret variable into two pieces in order to print it out, but come on. So maybe we’ve mostly achieved security by obscurity.

But again, I don’t really know the richness of this environment and perhaps more can be done to restrict who can alter the repo and run it in a pipeline.


People who know more than I, a newbie, have sugested a certain approach to dealing with sensitive variables with our Azure DevOps pipelines. I have described here what I as a newbie see as potential pitfalls as well as how to implement their chosen method.