Comprehensive Detailed Explanation with all AWS References

To resolve AccessDenied errors:

IAM Policy Validation:

Use IAM Access Analyzer to ensure that the policy attached to the role allows the necessary S3 actions (e.g., s3:GetObject).

Validate that the role is correctly assumed by the application.

The correct answer is A. Revoke all versions of the signing profile assigned to the developer.

According to the AWS documentation1, AWS Signer is a fully managed code-signing service that helps you ensure the trust and integrity of your code. You can use Signer to sign code artifacts, such as Lambda deployment packages, with code-signing certificates that you control and manage.

A signing profile is a collection of settings that Signer uses to sign your code artifacts. A signing profile includes information such as the following:

The type of signature that you want to create (for example, a code-signing signature).

The signing algorithm that you want Signer to use to sign your code.

The code-signing certificate and its private key that you want Signer to use to sign your code.

You can create multiple versions of a signing profile, each with a different code-signing certificate. You can also revoke a version of a signing profile if you no longer want to use it for signing code artifacts.

In this case, the company wants to ensure that all the code that the developer wrote can no longer be deployed to the Lambda functions. One way to achieve this is to revoke all versions of the signing profile that was assigned to the developer. This will prevent Signer from using that signing profile to sign any new code artifacts, and also invalidate any existing signatures that were created with that signing profile. This way, the company can ensure that only trusted and authorized code can be deployed to the Lambda functions.

The other options are incorrect because:

B. Examining the developer’s IAM roles and removing all permissions that grant access to Signer may not be sufficient to prevent the deployment of the developer’s code. The developer may have already signed some code artifacts with a valid signing profile before leaving the company, and those signatures may still be accepted by Lambda unless the signing profile is revoked.

C. Re-encrypting all source code with a new AWS Key Management Service (AWS KMS) key may not be effective or practical. AWS KMS is a service that lets you create and manage encryption keys for your data. However, Lambda does not require encryption keys for deploying code artifacts, only valid signatures from Signer. Therefore, re-encrypting the source code may not prevent the deployment of the developer’s code if it has already been signed with a valid signing profile. Moreover, re-encrypting all source code may be time-consuming and disruptive for other developers who are working on the same code base.

D. Using Amazon CodeGuru to profile all the code that the Lambda functions use may not help with preventing the deployment of the developer’s code. Amazon CodeGuru is a service that provides intelligent recommendations to improve your code quality and identify an application’s most expensive lines of code. However, CodeGuru does not perform any security checks or validations on your code artifacts, nor does it interact with Signer or Lambda in any way. Therefore, using CodeGuru may not prevent unauthorized or untrusted code from being deployed to the Lambda functions.

To enforce end-to-end encryption in transit, the company should do the following:

Update the web application configuration on the web servers to use HTTPS instead of HTTP when connecting to DynamoDB. This ensures that the data is encrypted when it travels from the web servers to the data store.

Update the CloudFront distribution to redirect HTTP requests to HTTPS. This ensures that the viewers always use HTTPS when they access the website through CloudFront.

Update the ALB to listen using HTTPS using the public ACM TLS certificate. Update the CloudFront distribution to connect to the HTTPS listener. This ensures that the data is encrypted when it travels from CloudFront to the ALB and from the ALB to the web servers.

Understand IMDSv2 Metrics:

IMDSv2 adds a layer of security to EC2 instance metadata by requiring a session token.

TheEC2MetadataNoTokenCloudWatch metric tracks the number of calls to IMDSv1.

Enable the IMDS Metrics:

Ensure that the EC2 instances have theDetailed Monitoringfeature enabled to publish metrics to CloudWatch.

Create a CloudWatch Dashboard:

In the CloudWatch console, create a dashboard that displays theEC2MetadataNoTokenmetric for all instances.

Verify Zero Value:

Monitor theEC2MetadataNoTokenmetric. If the value is zero for all instances, it confirms that IMDSv1 is no longer in use.

Secure Access and Validation:

Regularly monitor the dashboard to ensure no instance reverts to using IMDSv1.

Instance Metadata Service (IMDS) Documentation

CloudWatch Metrics for EC2 Instances

AWS Security Best Practices for Metadata Service

Understanding Gateway VPC Endpoint:

A gateway VPC endpoint allows traffic from the VPC to specific AWS services (e.g., Amazon S3) without traversing the public internet.

Key Configuration Points to Verify:

The route table is correctly configured to send traffic for Amazon S3 through the gateway VPC endpoint.

IAM permissions and bucket policies are correct and allow access to the specific S3 bucket.

Verify the Endpoint Policy:

Check the VPC endpoint policy to ensure it allows access to the S3 bucket. The policy might be restricting access to certain buckets, prefixes, or IAM principals.

Example VPC Endpoint Policy:

{

"Version": "2012-10-17",

"Statement": [

{

"Effect": "Allow",

"Principal": "*",

"Action": "s3:*",

"Resource": [

"arn:aws:s3:::example-bucket",

"arn:aws:s3:::example-bucket/*"

]

}

]

}

Testing and Validation:

Modify the endpoint policy if required and test access again from the EC2 instance.

Gateway VPC Endpoints Documentation

VPC Endpoint Policies for Amazon S3

To avoid AccessDeniedExceptions when users first attempt to encrypt using the CMK, the security specialist should recommend the following solution:

Instruct the engineering team to pass the grant token returned in the CreateGrant response to users. This allows the engineering team to use the grant token as a form of temporary authorization for the grant.

Instruct users to use that grant token in their call to encrypt. This allows the users to use the grant token as a proof that they have permission to use the CMK, and to avoid any eventual consistency issues with the grant creation.

the aws kms get-key-rotation-status command returns a boolean value that indicates whetherautomatic rotation of the customer master key (CMK) is enabled1. This commandalsoshowsthe date and time when the CMK was last rotated2. The other options are not valid ways to check the CMK rotation status.