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

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

Encrypting volumes if you deploy an EC2 occasion is an AWS safety greatest observe. In actual fact, you may most likely need to apply this all through your group. Should 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) hooked up to your VM.

Should 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 info on it.


Once you begin an EC2 occasion, it might 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. Once you encrypt an EC2 occasion, you will need to make sure that you encrypt all volumes. The tactic for encrypting the foundation quantity is described on this AWS weblog put up:

From the above:

To configure root quantity properties for an EC2 occasion, you will need to establish the gadget identify of the foundation quantity on your Amazon Machine Picture (AMI). You possibly can then use the BlockDeviceMapping property of an AWS::EC2::Occasion useful resource to set the properties of the foundation quantity.

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

One of many properties is named 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 making an attempt to elucidate this in a manner that individuals can perceive as a result of once I first began utilizing AWS, “EBS” cycled by way of me till I noticed it was mainly a digital drive. I fried some bodily drives in my life, I choose 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 will need to establish the gadget identify of the foundation quantity on your Amazon Machine Picture (AMI). You possibly can then use the BlockDeviceMapping property of an AWS::EC2::Occasion useful resource to set the properties of the foundation quantity.

This configuration above is the place we are able to override the defaults that have been used to deploy our EC2 occasion within the final put up as a result of we did not specify something.

gadget names

We have to specify the quantity for the EC2 occasion and override the setting. For this we’d like the identify of the gadget. 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 gadget and it’s the root gadget.

Here’s a bigger picture so you possibly can see that the gadget identify is /dev/xvda. You can even see within the Encrypted column that this gadget shouldn’t be encrypted. You can even see the foundation gadget identify on the high of the tab content material. There is just one gadget and it’s the root gadget.

I’ve one other occasion on my account the place I added two drives. You possibly can see which is the foundation drive and that each are encrypted.

Now go verify 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 check, as that is one of many issues I’ll verify. 🙂

You possibly can encrypt your EBS volumes by specifying by creating a tool block mapping. If you wish to encrypt the foundation quantity, set the gadget identify mapped to the foundation 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 quantity must be encrypted. The impact of setting the encryption state to true it is determined by the supply of the quantity (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 may very well be a bit clearer.

Related info from the AWS documentation:

Amazon EBS encrypts your quantity with an information key utilizing trade normal AES-256 information encryption. AWS KMS generates the info key, after which AWS KMS encrypts it together with your AWS KMS key earlier than storing it together with your quantity info. All snapshots and subsequent volumes created from these snapshots with the identical AWS KMS key share the identical information key. For extra info, see Information Keys within the AWS Key Administration Service Developer Information.

Observe that in case 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 quantity.

Create a KMS key

Alright, now we now have our developer encryption key used to encrypt secrets and techniques. We may also use it to encrypt our digital machines. In a manufacturing setting, you’ll most likely create a separate KMS key for every crucial utility and maybe every consumer, relying on the variety of shoppers that want assist and the sensitivity of the info. The draw back, as talked about, is the price of every KMS key. When you have thousands and thousands of shoppers, they may add up rapidly.

On the very least utility segregation would assist restrict the blast radius in an information breach like Capital One. Functions 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. have been affected by the breach (in response to the account of somebody who used to work there that I spoke to not too long ago).

Subsequent, add our block gadget 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. Once you attempt to deploy this template, you will notice an error like this. Should you did not know that the KMS key was the one factor that modified, you may need a tough time decoding this error. Because of this it is good to implement issues in small items at a time so you possibly can check them.

I keep in mind how this error drove builders loopy at Capital One. Occasion i-xxxxxxxx did not stabilize. Present state: shutting-down. Motive: Shopper.InternalError: Shopper error on launchThe corporate enforced that every one EC2 cases have been launched with encryption. The one drawback 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 again and again after they couldn't launch photos. Why it needs to be a secret that you would be able to't launch the picture resulting from a particular KMS error is past me. It wasted tons of our time and precipitated 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 may assume you may discover the error by trying on the EC2 occasion supply, however no.

Cloud formation? No. If you concentrate on 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 (keep in mind we added the Error column in a earlier put up).

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

"errorMessage": "Person: arn:aws:sts::xxx:assumed-role/AppDeploymentGroup/botocore-session-xxx shouldn't be approved 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 search for the ARN and add it to our comma-separated checklist in our deployment script:

Add the permissions to the AppDeploy function coverage as nicely.

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 are able to generically enable the DeveloperResources KMS key for use with any service.

Let us take a look at the request being denied in just a little extra element:

"eventSource": ""

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

Earlier than I carried out that, I attempted to take away the whole lot associated to the DeveloperResources key in CloudFormation. However we have to replace a number of different issues first earlier than we are able to try this.

So I gave the 2 new keys completely different names and carried out 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 may delete the opposite key.

We additionally must re-implement our SSH secret.

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

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

Person: arn:aws:sts::xxxxx:assumed-role/AppDeploymentGroup/botocore-session-xxxx shouldn't be approved 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 appropriate. The one factor left is the eventSource situation.

Clearly the supply of the occasion is KMS:

Nicely, 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": "Person: arn:aws:sts::xxxx:assumed-role/AppDeploymentGroup/botocore-session-xxxx shouldn't be approved 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 may attempt including it conditionally in some way, however in the meanwhile I am simply including it to see if we are able to get this to work.

And… that works.


And encrypted!

Phew it took fairly a number of weblog posts to get right here. We nonetheless want to determine why the KMS key coverage situation shouldn’t be working accurately. I will take one other take a look at that within the subsequent put up and check our SSH key to see if we are able to log in to our EC2 occasion.

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

Comply with for updates.

Teri Radichel

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