Deploy an EC2 Occasion with a KMS Encryption Key | by Teri Radichel | Cloud Safety | Oct, 2022 | Fantasy Tech

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ACM.89 Utilizing a KMS Buyer Managed Key (CMK) to restrict entry to information on EC2 cases and EBS volumes

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

Encrypting volumes while you deploy an EC2 occasion is an AWS safety greatest follow. The truth is, you may in all probability need to apply this all through your group. In the event you use the default AWS encryption, anybody who has permission to make use of KMS in your account can decrypt the contents of the volumes (drives) connected to your VM.

In the event you use your personal customer-managed key, you possibly can place restrictions on who can use the important thing that encrypts and decrypts the volumes related to the EC2 occasion. By doing so, somebody who would not have permission to make use of the important thing cannot connect the volumes to their very own occasion and see the information on it.


While you begin an EC2 occasion, it will possibly have a number of volumes: one root quantity in which there’s the working system and ephemeral information and a number of information volumes the place you possibly can retailer your utility code and information. While you encrypt an EC2 occasion, you could be sure that you encrypt all volumes. The strategy for encrypting the basis quantity is described on this AWS weblog submit:

From the above:

To configure root quantity properties for an EC2 occasion, you could establish the system identify of the basis quantity in your Amazon Machine Picture (AMI). You’ll be able to then use the BlockDeviceMapping property of an AWS::EC2::Occasion useful resource to set the properties of the basis quantity.

What does that imply? See the CloudFormation choices when creating an EC2 occasion.

One of many properties is known as BlockDeviceMappings:

Click on on that property to see its particulars:

From there, click on on the Ebs property. EBS stands for Elastic Block Retailer, or in regular nomenclature, a drive. Do not get all technical with me. I am attempting to elucidate this in a method that individuals can perceive as a result of once I first began utilizing AWS, “EBS” cycled by way of me till I spotted it was principally a digital drive. I fried some bodily drives in my life, I desire to cope with digital ones. Check out the Ebs properties:

Now our description as soon as once more:

To configure root quantity properties for an EC2 occasion, you could establish the system identify of the basis quantity in your Amazon Machine Picture (AMI). You’ll be able to then use the BlockDeviceMapping property of an AWS::EC2::Occasion useful resource to set the properties of the basis quantity.

This configuration above is the place we will override the defaults that had been used to deploy our EC2 occasion within the final submit as a result of we did not specify something.

system names

We have to specify the amount for the EC2 occasion and override the setting. For this we’d like the identify of the system. What’s that?

Head over to the EC2 Dashboard and click on on the occasion we simply created. Click on the Storage hyperlink and take a look at the “Gadget Identify” column. On this case we solely have one system and it’s the root system.

Here’s a bigger picture so you possibly can see that the system identify is /dev/xvda. You may also see within the Encrypted column that this system just isn’t encrypted. You may also see the basis system identify on the prime of the tab content material. There is just one system and it’s the root system.

I’ve one other occasion on my account the place I added two drives. You’ll be able to see which is the basis drive and that each are encrypted.

Now go examine all EC2 occasion volumes in your account. What? Are your volumes not encrypted? You’d higher try this earlier than you rent me for a cloud safety evaluation or cloud penetration take a look at, as that is one of many issues I will examine. 🙂

You’ll be able to encrypt your EBS volumes by specifying by creating a tool block mapping. If you wish to encrypt the basis quantity, set the system identify mapped to the basis quantity identify. Set encryption to true. Assign a KMS key ID to make use of a CMK (really useful).

Encrypted: Signifies whether or not the amount ought to be encrypted. The impact of setting the encryption state to true it will depend on the supply of the amount (new or from a snapshot), encryption startup standing, possession, and whether or not encryption is enabled by default.

So… what’s the impact? The documentation might be a bit clearer.

Related data from the AWS documentation:

Amazon EBS encrypts your quantity with a knowledge key utilizing business customary AES-256 information encryption. AWS KMS generates the information key, after which AWS KMS encrypts it along with your AWS KMS key earlier than storing it along with your quantity data. All snapshots and subsequent volumes created from these snapshots with the identical AWS KMS key share the identical information key. For extra data, see Knowledge Keys within the AWS Key Administration Service Developer Information.

Notice that should you attempt to share an encrypted quantity or AMI, the customers who want to make use of it should have permission to make use of the KMS key that encrypted the amount.

Create a KMS key

Alright, now we now have our developer encryption key used to encrypt secrets and techniques. We will even use it to encrypt our digital machines. In a manufacturing atmosphere, you’d in all probability create a separate KMS key for every vital utility and maybe every consumer, relying on the variety of shoppers that want help and the sensitivity of the information. The draw back, as talked about, is the price of every KMS key. You probably have hundreds of thousands of shoppers, they may add up rapidly.

On the very least utility segregation would assist restrict the blast radius in a knowledge breach like Capital One. Purposes that had buckets that encrypted information with a separate key that the function on the firewall’s EC2 occasion was not allowed to make use of wouldn’t be allowed to make use of. had been affected by the breach (in line with the account of somebody who used to work there that I spoke to not too long ago).

Subsequent, add our block system mapping properties to our EC2 CloudFormation template:

Add the KMS key export identify to the parameters and default to the developer useful resource key that we created earlier to encrypt our KMS key.

That is the place the cryptic error messages begin. While you attempt to deploy this template, you will note an error like this. In the event you did not know that the KMS key was the one factor that modified, you may need a tough time decoding this error. That is why it is good to implement issues in small items at a time so you possibly can take a look at them.

I bear in mind how this error drove builders loopy at Capital One. Occasion i-xxxxxxxx did not stabilize. Present state: shutting-down. Motive: Consumer.InternalError: Consumer error on launchThe corporate enforced that each one EC2 cases had been launched with encryption. The one downside was that we had 11,000 builders who did not all get the message. We had a whole lot of inside channels to get assist and this query got here up time and again once they couldn't launch photos. Why it needs to be a secret you could't launch the picture as a consequence of a selected KMS error is past me. It wasted tons of our time and triggered the builders a whole lot of grief.

Head over to CloudTrail to see what sort of error message we get there. Keep in mind that we’re utilizing the AppDeploy function.

Now you would possibly suppose you may discover the error by wanting on the EC2 occasion supply, however no.

Cloud formation? No. If you consider what we simply arrange, it was KMS. So search for the supply of the KMS occasion. Click on on the log entry that claims Entry Denied (bear in mind we added the Error column in a earlier submit).

Right here we get a extra cheap and helpful error message:

"errorMessage": "Consumer: arn:aws:sts::xxx:assumed-role/AppDeploymentGroup/botocore-session-xxx just isn't licensed to carry out: kms:GenerateDataKeyWithoutPlaintext on useful resource: arn:aws:kms:xxx:xxx:key/xxx as a result of no resource-based coverage permits the kms:GenerateDataKeyWithoutPlaintext motion"

We have to give our AppDeploy function permission to carry out the next KMS motion:


Give this function permission to encrypt information in our KMS key coverage. We will merely lookup the ARN and add it to our comma-separated listing in our deployment script:

Add the permissions to the AppDeploy function coverage as effectively.

I get the identical error. Why? Our situation… we now have specified that our key can solely be used with Secrets and techniques Supervisor. Now we now have a dilemma. We will create separate keys for the secretsmanager and EC2 cases, or we will generically permit the DeveloperResources KMS key for use with any service.

Let’s take a look at the request being denied in somewhat extra element:

"eventSource": ""

If we create an EC2 occasion key and go that service identify, our key coverage ought to work. Let’s create a brand new key. It will value me one other greenback, however that is not breaking the financial institution.

Earlier than I applied that, I attempted to take away every part associated to the DeveloperResources key in CloudFormation. However we have to replace just a few different issues first earlier than we will try this.

So I gave the 2 new keys completely different names and applied them first.

I then fastened the insurance policies that reference the outdated key to make use of the brand new key. I renamed the export to DeveloperSecrets as an alternative of DeveloperResources within the AppSec and IAMAdmins function insurance policies:

I then needed to replace the ImportValue for the brand new DeveloperComputeResources key within the AppDeploy function:

Then I might delete the opposite key.

We additionally must re-implement our SSH secret.

I additionally needed to replace the important thing reference within the Consumer Secrets and techniques Coverage.

Then we will redeploy our VM… Getting KMS error with AppDeploy Group. Nothing is so easy…

Consumer: arn:aws:sts::xxxxx:assumed-role/AppDeploymentGroup/botocore-session-xxxx just isn't licensed to carry out: kms:GenerateDataKeyWithoutPlaintext on useful resource: arn:aws:kms:xxx:xxx:key/xx as a result of no resource-based coverage permits the kms:GenerateDataKeyWithoutPlaintext motion

Right here is the related a part of the coverage:

Clearly kms motion is current. The AppDeploymentGroup function is right. The one factor left is the eventSource situation.

Clearly the supply of the occasion is KMS:

Effectively, let’s attempt to take away the situation.

Sure, eradicating the situation works. That looks as if a bug for AWS to repair. Clearly, the eventSource is In any case, let’s get this working.

Now we get a unique error.

"errorMessage": "Consumer: arn:aws:sts::xxxx:assumed-role/AppDeploymentGroup/botocore-session-xxxx just isn't licensed to carry out: kms:CreateGrant on useful resource: arn:aws:kms:xxx:xxxx:key/xxxx as a result of no resource-based coverage permits the kms:CreateGrant motion",

We do not have that motion in our coverage:

Let’s add it. We might strive including it conditionally in some way, however in the meanwhile I am simply including it to see if we will get this to work.

And… that works.


And encrypted!

Phew it took fairly just a few weblog posts to get right here. We nonetheless want to determine why the KMS key coverage situation just isn’t working accurately. I am going to take one other take a look at that within the subsequent submit and take a look at our SSH key to see if we will log in to our EC2 occasion.

Since I am taking a break now, I am going to cease that occasion to avoid wasting cash. Do not pay for assets while you’re not utilizing them!

Observe for updates.

Teri Radichel

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Deploy an EC2 Instance with a KMS Encryption Key | by Teri Radichel | Cloud Security | Oct, 2022