Automated Creation of an SSH Key for an AWS Person | by Teri Radichel | Cloud Safety | Oct, 2022 | Elevate Tech

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ACM.78 Automated creation of an AWS EC2 SSH key saved in AWS

This can be a continuation of my sequence on automating cybersecurity metrics.

I wrote about totally different authentication mechanisms within the final submit.

Now let’s have a look at how we are able to automate the implementation of an SSH key that permits a consumer to log in to an EC2 occasion.

This implementation has some safety issues that we are going to repair within the subsequent few posts. I believed it was going to be easy...however it wasn't.

An SSH key identifies a consumer (as does any credential you assign to a consumer)

An SSH key should belong to a single consumer. Identifies that consumer as the one who related on a given day and time to a number. We will add our SSH key creation code to our frequent IAM roles and have the IAM crew handle the deployment of SSH keys, however the IAM crew ought to by no means have entry to keys owned by different customers. See the final submit for an outline of non-repudiation and why it will be significant for safety.

We’re going to create a key related to a consumer in the mean time of making the consumer. The password may have the identical identify because the consumer. We’ll create it within the IAM listing of our code utilizing the IAM CLI profile, because it’s tied to the consumer’s id.

Create an SSH key and retailer it within the AWS Parameter Retailer

Right here is a few code that creates a key and shops it within the AWS parameter retailer. I put my user_functions.sh file in my IAM customers listing. The profile on the subject of the IAM profile included within the file.

I will add a parameter to my create consumer operate that signifies whether or not or not a key must be created for that consumer.

I will verify if that worth is “y” and in that case, name the operate to create the consumer key.

In my deployment.sh file, I will cross “y” or “n” to point whether or not or not I need to create a key for every consumer. For now, I am simply going to create an SSH key for the Developer consumer.

Okay, now run the deployment script.

Error: No permission. What permissions do we’d like?

ec2 create-key-pair
ec2 wait key-pair-exists
aws ssm put-parameter

What’s fascinating to me is that an SSH key is definitely an IAM management, however it exists below EC2. That has implications for IAM permissions administration. If you happen to give somebody the ec2.* permission, that individual can do two issues which can be very crucial to cloud safety:

  1. change networks
  2. Implement SSH keys

So an individual may arrange a brand new community with entry to your delicate assets on no matter account you are on and set up a brand new ec2 occasion with an SSH key, log in and hook up with different assets in your community. If one thing is not protected by IAM controls, encryption, and key insurance policies, it could possibly be accessed by that consumer.

The ethical of the story: Watch out with * in IAM Insurance policies!

We nonetheless have to return and restrict our community administration permissions to a zero-trust coverage once we end implementing community controls. For now, let’s add the mandatory permissions to our IAM Admins group position coverage.

Use the deployment_iam_role.sh deployment script to deploy the position. Deploy once more. My script labored the primary time however not the second time as a result of I want so as to add a line to delete the important thing if it already exists after which add that permission to the IAM admin group coverage.

You could have observed that I’m utilizing a command with the phrase “Waiter”. That key phrase causes the command to attend for a useful resource to exist, on this case a key pair.

Apparently the KeyPairExists command additionally requires ec2.DescribeKeyPairs.

And works.

Works! Have we completed effectively?

Not fairly. Let’s replicate on our script for a minute. How does it work? Obtain the SSH key and retailer the output to a file. It then manipulates the output of that file to extract a sound .pem file that we are able to use as an SSH key to log in to an AWS host. (You’ve got saved the general public key in AWS to be used with EC2 situations.)

So the place did these two recordsdata find yourself?

They’re in our residence listing (specified by ~ under):

Anybody who can entry this host, or its backups, would have entry to these keys. Somebody may additionally detach the EBS quantity (digital drive) and fix it to a different occasion. Somebody may create a picture of this machine and launch one other similar to it to entry these recordsdata.

Nicely, we may delete these keys. That ought to resolve the issue, proper? Not fairly. I will present you why within the subsequent submit.

What different downside do we have now? We needed to give the IAM administrator full entry to create and delete parameters in SSM. That is okay? Perhaps it’s, possibly it is not. It is dependent upon whether or not you retailer delicate knowledge within the parameter retailer or not and whether or not you encrypt it.

Talking of encryption, we do not encrypt our credentials. Anybody who has entry to the parameter retailer can see them. As already talked about, if we use the parameter retailer, we can’t assign a useful resource coverage to limit entry to our parameters, so we must use an encryption key with restricted entry to unravel this downside.

So if we create a KMS key and assign it to a consumer, we are able to create the credentials and even the IAM administrator cannot see them, since solely that consumer would be capable of encrypt and decrypt with that key. What’s the potential draw back of that strategy? Now we have to pay $1 per encryption key on AWS final time I checked. You probably have 11,000 builders like Capital One had after I was there, that is $11,000 a month. That is okay? Perhaps it’s, possibly it is not.

Is there an alternate? We will retailer the credentials in Secrets and techniques Supervisor. If we retailer the credentials in Secrets and techniques Supervisor, we are able to create a coverage to robotically rotate the credentials. We will additionally create a coverage that solely permits the precise developer who owns the credentials to entry them. We may use a generic key to encrypt the credentials, however we’ll nonetheless pay extra for Secrets and techniques Supervisor. What’s the distinction?

On the whole, if I am this accurately, the parameter retailer with a KMS key per consumer would price $1.05 per thirty days, whereas the key supervisor with a single KMS key for all builders, however a coverage that restricts every developer to entry solely your personal SSH key secret. price .40 per consumer plus $1 per thirty days. If you happen to solely have one consumer then it’s $1.05 vs. $1.40. You probably have two customers, Secrets and techniques Supervisor looks as if a greater possibility. The operations price the identical.

All proper, we have now to consider how we’re going to resolve the above issues. Keep tuned for the following submit.

Teri Radichel

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Automated Creation of an SSH Key for an AWS User | by Teri Radichel | Cloud Security | Oct, 2022