terraform.aws.security.aws-lambda-environment-unencrypted.aws-lambda-environment-unencrypted

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By default, the AWS Lambda Environment is encrypted using AWS-managed keys. However, for added security, it's recommended to configure your own AWS KMS encryption key to protect your environment variables in Lambda. You can either create a new aws_kms_key resource or use the ARN of an existing key in your AWS account to do so.

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Defintion

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rules:
  - id: aws-lambda-environment-unencrypted
    patterns:
      - pattern-inside: |
          resource "aws_lambda_function" $ANYTHING {
            ...
          }
      - pattern-either:
          - patterns:
              - pattern: |
                  environment { ... }
              - pattern-not-inside: |
                  resource $A $B {
                    ...
                    kms_key_arn = ...
                    ...
                  }
          - patterns:
              - pattern: |
                  kms_key_arn = ...
              - pattern-not-inside: |
                  resource $A $B {
                    ...
                    environment { ... }
                    ...
                  }
          - pattern: kms_key_arn = ""
    message: By default, the AWS Lambda Environment is encrypted using AWS-managed
      keys. However, for added security, it's recommended to configure your own
      AWS KMS encryption key to protect your environment variables in Lambda.
      You can either create a new aws_kms_key resource or use the ARN of an
      existing key in your AWS account to do so.
    languages:
      - hcl
    severity: WARNING
    metadata:
      owasp:
        - A03:2017 - Sensitive Data Exposure
      cwe:
        - "CWE-320: CWE CATEGORY: Key Management Errors"
      technology:
        - aws
        - terraform
      category: security
      references:
        - https://owasp.org/Top10/A02_2021-Cryptographic_Failures
      subcategory:
        - audit
      likelihood: LOW
      impact: LOW
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cryptographic Issues

Examples

aws-lambda-environment-unencrypted.tf

resource "aws_lambda_function" "fail" {
   function_name                  = var.function_name
   role                           = aws_iam_role.lambda-messageprocessor.arn
   runtime                        = "python3.6"
   handler                        = "handler.lambda_handler"
   filename                       = data.archive_file.notify.output_path
   source_code_hash               = data.archive_file.notify.output_base64sha256
   reserved_concurrent_executions = var.concurrency
   tracing_config {
      mode = "PassThrough"
   }

   # ruleid: aws-lambda-environment-unencrypted
   environment {
      test="true"
   }
}
resource "aws_lambda_function" "failkmsnovars" {
   function_name                  = var.function_name
   role                           = aws_iam_role.lambda-messageprocessor.arn
   runtime                        = "python3.6"
   handler                        = "handler.lambda_handler"
   filename                       = data.archive_file.notify.output_path
   source_code_hash               = data.archive_file.notify.output_base64sha256
   reserved_concurrent_executions = var.concurrency
   tracing_config {
       mode = "PassThrough"
    }
   # ruleid: aws-lambda-environment-unencrypted
   kms_key_arn = aws_kms_key.anyoldguff.arn
}

resource "aws_lambda_function" "ignore" {
   function_name                  = var.function_name
   role                           = aws_iam_role.lambda-messageprocessor.arn
   runtime                        = "python3.6"
   handler                        = "handler.lambda_handler"
   filename                       = data.archive_file.notify.output_path
   source_code_hash               = data.archive_file.notify.output_base64sha256
   reserved_concurrent_executions = var.concurrency
   tracing_config {
       mode = "PassThrough"
    }
}

resource "aws_lambda_function" "pass" {
   function_name                  = var.function_name
   role                           = aws_iam_role.lambda-messageprocessor.arn
   runtime                        = "python3.6"
   handler                        = "handler.lambda_handler"
   filename                       = data.archive_file.notify.output_path
   source_code_hash               = data.archive_file.notify.output_base64sha256
   reserved_concurrent_executions = var.concurrency
   tracing_config {
       mode = "PassThrough"
    }
    environment {
        test="true"
    }
   kms_key_arn = aws_kms_key.anyoldguff.arn
}
resource "aws_lambda_function" "failasempty" {
   function_name                  = var.function_name
   role                           = aws_iam_role.lambda-messageprocessor.arn
   runtime                        = "python3.6"
   handler                        = "handler.lambda_handler"
   filename                       = data.archive_file.notify.output_path
   source_code_hash               = data.archive_file.notify.output_base64sha256
   reserved_concurrent_executions = var.concurrency
   tracing_config {
       mode = "PassThrough"
    }
   # ruleid: aws-lambda-environment-unencrypted
   kms_key_arn = ""
}