ACM.58 Making a parameter to retailer our batch job session

It is a continuation of my collection on automating cybersecurity metrics.

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I posted the structure I am engaged on some time again, although I am nonetheless including a number of the items on the time of writing.

We’re engaged on a Lambda operate that begins the method to start out a batch job. A part of that was producing a cryptographically safe random ID for our batch jobs:

We embed it in a Lambda operate:

Then we begin engaged on a approach to ship textual content messages to batch job operators, however now we have to attend till we get our numbers or SMS into AWS:

So now again to what else we’d like with our Lambda operate. We’re going to retailer our batch job ID in an AWS SSM parameter.

AWS Techniques Administrator

When you’re not conversant in AWS Techniques Supervisor, it is a assortment of options that appears to be geared toward IT directors who’re used to patching techniques and working scripts on them. I am not a fan of that method as a result of I favor immutable infrastructure as I’m and I will present you how you can construct on this weblog collection. As an alternative of patching, redeploy to get your updates.

Additionally, I see loads of safety challenges with AWS Techniques Supervisor safety. In my safety courses, I clarify how performance in AWS Techniques Supervisor could possibly be used as a C2 channel. In reality, after that, an organization I do know of created an open supply instrument that does precisely that. After I noticed the demo after inviting them to my AWS Meetup in Seattle (at the moment on maintain on account of logistical challenges, however hopefully I will be again quickly, however hopefully extra occasions on-line quickly), I instantly requested the developer if he was utilizing AWS Techniques Supervisor underhood. . Sure.

AWS Techniques Supervisor Parameter Retailer vs. Secrets and techniques Supervisor

Though I do not use a lot of what is in AWS Techniques Supervisor for safety causes, I can use part of AWS Techniques Supervisor: Parameter Retailer. It’s much like AWS Secrets and techniques Supervisor with not all of the performance and is cheaper.

A few of the variations: AWS SSM would not rotate credentials and you do not have cross-account entry right now (which might be good if you wish to make it possible for nobody exterior of your account can see what you are storing there by way of a misconfigured operate). ). It might probably retailer textual content blobs, nevertheless it would not have the performance that the AWS Secrets and techniques supervisor has to retailer well-defined key/worth pairs. All of this isn’t good or unhealthy, it is simply that you want to contemplate your use case and select the suitable resolution for the job.

Additionally, you can not encrypt SSM parameter values ​​created with CloudFormation. I’ve already proven you ways to do that with AWS Secrets and techniques Supervisor:

Since I will probably be creating loads of periods, I am hoping this extra worthwhile possibility will work for me, however we’ll have to check it to make certain.

You may safe AWS Techniques Supervisor

Additionally, earlier than anybody will get too mad at me, I can in all probability safe AWS Techniques Supervisor fairly decently for a lot of use circumstances. It is simply tougher to do as a result of a number of the performance is a bit freeform and it’s important to watch out about what folks can do with paperwork on techniques. I actually have averted complexity up to now and stick with immutable infrastructure. There are some circumstances the place you’ll need to use patches (databases, for instance), however you can too delegate that duty to AWS for those who use a managed database service. Who is aware of, possibly in some unspecified time in the future you may have a cause to make use of one other characteristic of AWS SSM.

Concerning the batch job ID as parameter identify…

I’ll use the batch job id for my parameter identify. Now why do not I retailer the worth of the batch job id and use the batch job identify because the parameter identify?

Contemplate our use case. What occurs if now we have a number of batch jobs working on the similar time? We could have totally different batch job IDs, however the batch job identify would be the similar. I already confirmed you a second in the past that we can’t add two parameters with the identical identify to the SSM parameter retailer. We’d like a singular worth for our parameter identify and one {that a} batch job can use later to retrieve the proper parameter. We’re utilizing a batch job ID for this function.

The batch job id is sort of a session for a specific occasion of that batch job working on our account. It will likely be related to a selected AWS session tied to that batch job ID and can expire after a time period. As a result of this worth acts as a session ID, we wish to restrict the possibility that somebody can get it and begin a batch job. For now, and for those who have been creating this, you can keep away from doing something dangerous with a batch job till that is resolved.

Utilizing Boto3 to create a parameter and retailer it in SSM

I defined what Boto3 is within the final publish and we took a have a look at the SSM documentation particularly.

We wish to name the put_parameter operate and it seems like we have to specify a reputation, worth and kind. There are further parameters, however we are going to omit them for now.

Examine the documentation for limitations on parameter names, however the naming conference we have outlined needs to be advantageous.

One of many issues now we have to specify is “kind”. What are our kind choices?

String It might be clear textual content.

safe chain could be encrypted. We will use the default AWS encryption or present our personal KMS key ID. I will clarify why the latter is a greater possibility in a second.

string checklist is a comma separated checklist. We will be taught extra in regards to the StringList kind within the AWS API reference documentation for SSM PutParameter:

Again to Boto3 documentation. There’s a notice right here that I would really like you to notice within the Warning under:

You may’t use SecureString with CloudFormation. That’s why at any time when I wish to use CloudFormation to retailer any kind of worth I wish to be encrypted and never seen within the AWS console, logs, and so on., I by no means use Parameter Retailer. I exploit AWS Secrets and techniques Supervisor.

Storing a Worth in AWS Techniques Supervisor

Let’s first check our code in a neighborhood Python file and run it to check the code we’ll add to our Lambda operate.

We will create a test-ssm-put-param.py file and add the next code. Let’s begin with a SecureString that makes use of the default AWS encryption.

#!/bin/python3import boto3
ssm = boto3.consumer('ssm')param_name="TestParameter"
param_value="TestValue"
param_type="SecureString"#utilizing AWS default encrypt (kind=SecureString)
ssm.put_parameter(Identify=param_name,Worth=param_value,Kind=param_type
val = ssm.get_parameter(Identify=param_name, WithDecryption=True)print(val)

Double click on the file and it ought to add a parameter to the SSM Parameter Retailer. It should then retrieve and print the parameter.

You can too examine the AWS Techniques Supervisor parameter retailer console to substantiate that your parameter exists.

Observe that for those who run the check once more you’re going to get an error as a result of the parameter already exists.

You may take away the parameter or add further code to the script to take away the parameter after retrieving it.

Add the batch job identify as a parameter handed to our Lambda operate

Now let’s add this to our lambda operate. First, we wish to move a batch job identify. Configure the Lambda operate check occasion the way in which I wrote within the final publish. The identify of the operate we’re engaged on is known as: GenerateBatchJobIDLambda. You may merely change the present check occasion.

Reserve it:

Modify our Lambda code to learn the worth of the BatchJobName parameter

Replace the Lambda code in our CloudFormation template to learn the parameter as defined within the final publish.

batch_job_name=occasion['BatchJobName']

Observe that this at the moment has an enormous safety difficulty. Appears like my final publish on Lambda operate parameters, XSS and injection assaults. We are going to repair it in a future publish.

Retailer SSM parameter

Add the code to retailer the SSM parameter after producing the ID. Use the ID for the parameter identify and the batch job identify for the worth.

Deploy CloudFormation to replace the operate utilizing the deployment.sh file within the capabilities folder we created within the earlier publish:

./deploy.sh

Now you can check your operate from the console utilizing the brand new check occasion.

Add SSM permission to our Lambda function

AHA. I forgot to replace the function related to this Lambda operate to permit it to name ssm::PutParameter.

Now take into consideration the permissions we have to grant to the Lambda operate for a minute. Can this Lambda operate add any parameters to the SSM parameter retailer? We simply need you so as to add this batch job ID parameter. We additionally don’t desire anybody else to have the ability to edit our batch job ID parameters.

Let’s begin by modifying the worth that we retailer in our code to the next for the parameter identify to the next format:

param_name="batch-job-" + batch_job_id

That may even make it simple for us to look and discover the parameters associated to our batch jobs within the SSM Parameter Retailer.

Do not forget that we had a tough deny assertion in our Lambda operate coverage:

Add permission for the Lambda operate to name AWS SSM PutParameter, however just for sources that begin with “batch-job-“.

Rerun the deployment script to implement the coverage change.

Observe that I acquired this error because of the coverage above. Oops. When you’ve ever seen this error, don’t overlook !Sub when including pseudo parameters. The error message could possibly be a tad much less obscure. I simply acquired this just a few days in the past and I already had forgotten what induced it. That’s why I’m writing issues down on posts in my bug weblog:

Wait a couple of minutes for IAM permissions to activate, after which attempt your function once more. Yippe!

Now examine if the parameter exists within the parameter retailer. Wow!

Observe that we need not give our Lambda operate permissions to learn or retrieve parameters, solely to write down parameters.

SSM Parameter Retailer Insurance policies

Now, how would we stop another person from studying or modifying these insurance policies? Does an SSM parameter have a coverage like an AWS KMS key that we will use to limit entry to solely the individuals who ought to entry that parameter? Nope.

AWS Parameter Retailer has one thing they sadly referred to as a “Coverage”, however it isn’t a useful resource coverage that can be utilized to forestall entry to a specific parameter. Maintain that thought.

Though I acquired this to “work”, we’re not executed with this implementation. Have you learnt what safety gaps exist once you have a look at this implementation? What enhancements might we add to make it tougher for an attacker to retrieve our parameters or the values ​​they comprise?

Keep tuned… observe us for updates.

Teri Radichel

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