Ensure that Lambda Function's environment variables 'Encryption at Rest' feature uses Customer Master Keys (CMK)

Lambda Function's environment variables are encrypted by default using the AWS default keys. Use Customer Master Keys to add another layer of control to the encryption.

Risk Level: Low
Cloud Entity: AWS Lambda
CloudGuard Rule ID: D9.AWS.CRY.68
Category: Compute


Lambda where not environmentVariables isEmpty() should have kmsKeyArn


From Portal

  1. Go to 'Lambda' dashboard
  2. In the left menu, select 'Functions'
  3. Select the relevant Lambda Function
  4. Under 'Configurations', go to 'Environment variables' and press 'Edit'
  5. Under 'Encryption configuration', set 'AWS KMS key to encrypt at rest' to 'Use a customer master key'
  6. Configure your 'Customer master key' and save

From TF
To update a Lambda Function with a key for environment variables encryption, add the 'kms_key_arn' to the 'aws_lambda_function block:

resource "aws_lambda_function" "lambda_function_example" {
	kms_key_arn = KEY-ARN

From Command Line
To update a Lambda Function with a key for environment variables encryption, use:

aws lambda update-function-configuration --function-name FUNCTION-NAME --kms-key-arn KEY-ARN


  1. https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
  2. https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/lambda_function#kms_key_arn
  3. https://awscli.amazonaws.com/v2/documentation/api/latest/reference/lambda/update-function-configuration.html

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