Making a Function for an EC2 Occasion with CloudFormation | by Teri Radichel | Cloud Safety | Nov, 2022 | Throne Tech

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ACM.107 Utilizing an IAM position profile with an EC2 occasion for short-term rotating credentials

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

Within the final put up, we created a VPC endpoint for CloudFormation in order that we are able to entry the AWS service from a non-public community. The put up additionally confirmed you while you won’t truly be utilizing a non-public community when you might have a VPC Endpoint configured.

On this put up, we wish to check our VPC endpoint, however earlier than we are able to try this, we’d like some credentials on the digital machine we wish to use to check CloudFormation.

We’re going to create a job on this put up that we are able to assign to this occasion to carry out CloudFormation actions. We’re going to use our AppDeploy position and modify it in order that it may be assigned to an EC2 occasion.

This position will look just like different roles we created with one exception. To allow the flexibility to affiliate this position with an EC2 occasion, we have to create a occasion profile.

Occasion Profiles within the AWS Console

If you assign a job to an EC2 occasion within the AWS console, you need not create the occasion profile. You possibly can right-click an occasion to assign a job to it, or do the identical from the actions menu.

The roles you see on the following display screen would be the roles which have a belief coverage that permits EC2 to make use of that position. I defined what belief insurance policies are right here:

You possibly can see the assigned position within the occasion particulars of the EC2 dashboard.

AWS routinely provides an occasion profile to the roles that you simply create within the console for EC2 situations.

Function profiles in CloudFormation

In CloudFormation, you have to explicitly outline the position’s profile:

We’ll add an occasion profile and belief coverage to the AppDeploy position we created and check it. If you create a server to deploy functions for you, they often run with a job. Utilizing a job moderately than long-term developer credentials is most well-liked when utilizing non-human-initiated automation. In different phrases, a server runs unattended and takes no matter steps are essential to carry out some activity.

Why use an AWS IAM position on an EC2 occasion as a substitute of developer credentials?

Should you use an AWS Entry Key ID and a Secret Entry Key ID in that situation, any attacker who obtains the credentials can use them on some other machine so long as these credentials are legitimate. Please keep in mind that we can not implement MFA with long-term credentials, aside from assumption of duties.

If you use an AWS position, the credentials are nonetheless current. Nonetheless, they rotate steadily. If stolen by an attacker, they are going to be good for a shorter time frame. Additionally, when you use AWS GuardDuty, it is going to detect when position credentials are used exterior of your AWS account.

MFA can trump IAM roles

Utilizing IAM roles on EC2 situations is an effective apply; nonetheless, that additionally assumes that you’re not making use of MFA. Should you require customers to imagine a job via MFA to carry out actions, it is most likely pretty much as good or higher than an IAM position. be began with no second issue, not like an all the time obtainable position on an EC2 occasion.

We have checked out eventualities all through this collection the place you’ll be able to and may’t apply MFA in IAM insurance policies. You may have to be cautious to grasp when MFA does not actually apply. For instance, we take a look at coverage weaknesses by utilizing if it exists and the truth that the AWS documentation on the time the weblog put up was written was presumably deceptive on that time. It could have been up to date since then.

When you must use a job

If in case you have any automation that responds to occasions with out human interplay, you will want to make use of an IAM position or another type of credentials apart from MFA. In fact, you’ll be able to request MFA at an earlier occasion that triggers the chain of occasions that led to automation. That is what we will attempt to do on this batch job weblog collection.

This isn’t a typical implementation, by the way in which. It is roughly an experiment simply because I wish to see if I could make it work and think about the downsides of my method.

Add ec2 to our service position template

Use the perform we created to deploy service roles to deploy a brand new EC2 position, on this case known as EC2AppDeployRole:

That implements the position and belief coverage, however not the permissions:

We will use the prevailing AppDeployment Group Function Insurance policies for this function.

We’ve two insurance policies utilized to the AppDeploymentGroup and we are able to merely add this position to these coverage templates.

AppDeploymentGroupRolePolicy.yaml

AppDeploymentGroupRoleKMSPolicy.yaml

As soon as carried out, you need to see two insurance policies related to the IAM position:

Add an occasion profile to our AppDeployment position template

Now we have to add the position profile of the EC2 occasion by way of a CloudFormation template. The place ought to we create this position profile? Ought to it’s created by the AppDeployment position, or ought to we have now IAM directors create it? As all the time, there isn’t a proper reply, however on this POC we’re going to let IAM directors outline which roles can be utilized with EC2 situations. These position profiles might be outlined within the IAM listing, and IAM directors will deploy the template.

We actually solely want two properties: the identify and the roles. The trail is an non-obligatory identifier. Right here is our template that we as soon as once more hold generic so we are able to reuse it.

We are going to create a typical perform to implement the profile:

Name the perform from the deployment.sh script utilizing the position identify we simply deployed.

Now you can see that this position has an occasion profile:

Assign the position to the EC2 occasion within the EC2 CloudFormation template

Now we are able to assign the position to the occasion utilizing the IAMInstanceProfile property:

We will use the output export to make sure that solely legitimate CloudFormation exports are used for position profiles:

Okay, that is the place some funky CloudFormation stuff occurred once more. There’s all the time one thing*.

Initially, when including that line to affiliate the IAM profile, I received the next error in CloudFormation saying that this person doesn’t have permissions to run situations:

Now, I do know that this person and group had this permission the final time I deployed this digital machine and I did not change something. To verify, I eliminated the brand new line I simply added above.

I then received an error saying {that a} new useful resource couldn’t be created as a result of current EIP affiliation. Hmm. That could possibly be an issue, however I am ignoring it for now. I eliminated the affiliation and carried out it once more.

Now I get a unique error message which is the precise drawback:

That makes extra sense and is suitable. It seems to be like a CloudForamtion error there. In both case, we have to add that permission to our AppDeploy Roles Coverage. Whereas I am at it, I’ll enable all actions from the Ec2 occasion profile:

Deploy that coverage after which strive the digital machine deployment once more.

I received an error a couple of totally different motion. I initially thought it was associated to the * on the finish of the above motion, however it wasn’t.

I parse and decode the related error message by following these steps:

It seems that the reported motion reported as not allowed in CloudFormation shouldn’t be the motion within the encoded message. It says the motion is IAM:PassRole. This seems to be like one other CloudFormation error.

Our coverage has permission for the IAM::PassRole motion however just for a particular position:

We have to add our new EC2 position.

Redeploy the coverage. Retry the digital machine deployment.

It’s nonetheless not right. We’ve to make use of the position ARN on this case, not the occasion profile ARN. Trace: Take a look at the position that IAM:PassRole is making an attempt to make use of within the error message. Copy and paste to avoid wasting your self some trouble.

Redeploy the coverage. Retry the digital machine deployment.

I saved getting errors so I ended up coding all actions associated to occasion profiles:

This works:

Lastly. That took too lengthy for one thing that needs to be easy.

Return to the Community folder and redeploy the EIP affiliation.

Confirm that the AWS CLI exists or set up it on the EC2 occasion

Launch and log in to the Developer VM that we simply up to date.

Comply with the steps to obtain the GitHub repository. If I’ve time, I will present you create an AMI so you do not have to do it time and again. Keep in mind that we configured our community to permit entry to GitHub in a earlier put up utilizing an inventory of prefixes.

sudo yum set up git
git clone [repo]

Run the next command to validate that the AWS CLI is put in.

aws --version

run aws configure to outline the area through which you wish to run your instructions. I assume you are acquainted with this, but when not, please overview the AWS CLI set up and configuration documentation.

Now keep in mind that our deployment position has permission to deploy particular CloudFormation stacks. I’ve added permission to the AppDeploy perform for DescribeStacks for any “*” assets to make it simpler to check this specific performance. After doing that, the person can run this command:

aws cloudformation describe-stacks

It doesn’t work. As a result of it doesn’t work?

We are going to see that within the subsequent put up. We’ll troubleshoot our VPC endpoint and talk about the DNS settings required for personal connections.

Comply with for updates.

Teri Radichel

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Creating a Role for an EC2 Instance with CloudFormation | by Teri Radichel | Cloud Security | Nov, 2022