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Amazon Lambda controls

These controls are related to Lambda resources.

These controls may not be available in all Amazon Web Services Regions. For more information, see Availability of controls by Region.

[Lambda.1] Lambda function policies should prohibit public access

Related requirements: PCI DSS v3.2.1/1.2.1, PCI DSS v3.2.1/1.3.1, PCI DSS v3.2.1/1.3.2, PCI DSS v3.2.1/1.3.4, PCI DSS v3.2.1/7.2.1, NIST.800-53.r5 AC-21, NIST.800-53.r5 AC-3, NIST.800-53.r5 AC-3(7), NIST.800-53.r5 AC-4, NIST.800-53.r5 AC-4(21), NIST.800-53.r5 AC-6, NIST.800-53.r5 SC-7, NIST.800-53.r5 SC-7(11), NIST.800-53.r5 SC-7(16), NIST.800-53.r5 SC-7(20), NIST.800-53.r5 SC-7(21), NIST.800-53.r5 SC-7(3), NIST.800-53.r5 SC-7(4), NIST.800-53.r5 SC-7(9)

Category: Protect > Secure network configuration

Severity: Critical

Resource type: AWS::Lambda::Function

Amazon Config rule: lambda-function-public-access-prohibited

Schedule type: Change triggered

Parameters: None

This control checks whether the Lambda function resource-based policy prohibits public access outside of your account. The control fails if public access is permitted. The control also fails if a Lambda function is invoked from Amazon S3, and the policy doesn't include a condition to limit public access, such as AWS:SourceAccount. We recommend using other S3 conditions along with AWS:SourceAccount in your bucket policy for more refined access.

The Lambda function should not be publicly accessible, as this may allow unintended access to your function code.

Remediation

To remediate this issue, you must update your function's resource-based policy to remove permissions or to add the AWS:SourceAccount condition. You can only update the resource-based policy from the Lambda API or Amazon CLI.

To start, review the resource-based policy on the Lambda console. Identify the policy statement that has Principal field values that make the policy public, such as "*" or { "AWS": "*" }.

You cannot edit the policy from the console. To remove permissions from the function, run the remove-permission command from the Amazon CLI.

$ aws lambda remove-permission --function-name <function-name> --statement-id <statement-id>

Replace <function-name> with the name of the Lambda function, and <statement-id> with the statement ID (Sid) of the statement that you want to remove.

[Lambda.2] Lambda functions should use supported runtimes

Related requirements: NIST.800-53.r5 CA-9(1), NIST.800-53.r5 CM-2, NIST.800-53.r5 SI-2, NIST.800-53.r5 SI-2(2), NIST.800-53.r5 SI-2(4), NIST.800-53.r5 SI-2(5)

Category: Protect > Secure development

Severity: Medium

Resource type: AWS::Lambda::Function

Amazon Config rule: lambda-function-settings-check

Schedule type: Change triggered

Parameters:

This control checks whether the Lambda function settings for runtimes match the expected values set for the supported runtimes for each language. The control fails if a Lambda function doesn't use a supported runtime.

The control checks function settings for the runtimes noted previously under parameters. Security Hub ignores functions that have a package type of Image.

Lambda runtimes are built around a combination of operating system, programming language, and software libraries that are subject to maintenance and security updates. When a runtime component is no longer supported for security updates, Lambda deprecates the runtime. Even though you can't create functions that use the deprecated runtime, the function is still available to process invocation events. We recommend ensuring that your Lambda functions are current and don't use deprecated runtime environments. For a list of supported runtimes, see Lambda runtimes in the Amazon Lambda Developer Guide.

Remediation

For more information about supported runtimes and deprecation schedules, see Runtime deprecation policy in the Amazon Lambda Developer Guide. When you migrate your runtimes to the latest version, follow the syntax and guidance from the publishers of the language. We also recommend applying runtime updates to help reduce the risk of impact to your workloads in the rare event of a runtime version incompatibility.

[Lambda.3] Lambda functions should be in a VPC

Related requirements: PCI DSS v3.2.1/1.2.1, PCI DSS v3.2.1/1.3.1, PCI DSS v3.2.1/1.3.2, PCI DSS v3.2.1/1.3.4, NIST.800-53.r5 AC-21, NIST.800-53.r5 AC-3, NIST.800-53.r5 AC-3(7), NIST.800-53.r5 AC-4, NIST.800-53.r5 AC-4(21), NIST.800-53.r5 AC-6, NIST.800-53.r5 SC-7, NIST.800-53.r5 SC-7(11), NIST.800-53.r5 SC-7(16), NIST.800-53.r5 SC-7(20), NIST.800-53.r5 SC-7(21), NIST.800-53.r5 SC-7(3), NIST.800-53.r5 SC-7(4), NIST.800-53.r5 SC-7(9)

Severity: Low

Resource type: AWS::Lambda::Function

Amazon Config rule: lambda-inside-vpc

Schedule type: Change triggered

Parameters: None

This control checks whether a Lambda function is deployed in a virtual private cloud (VPC). The control fails if the Lambda function isn't deployed in a VPC. Security Hub doesn't evaluate the VPC subnet routing configuration to determine public reachability. You might see failed findings for Lambda@Edge resources.

Deploying resources in a VPC strengthens security and control over network configurations. Such deployments also offer scalability and high fault tolerance across multiple Availability Zones. You can customize VPC deployments to meet diverse application requirements.

Remediation

To configure an existing function to connect to private subnets in your VPC, see Configuring VPC access in the Amazon Lambda Developer Guide. We recommend choosing at least two private subnets for high availability and at least one security group that meets the connectivity requirements of the function.

[Lambda.5] VPC Lambda functions should operate in multiple Availability Zones

Related requirements: NIST.800-53.r5 CP-10, NIST.800-53.r5 CP-6(2), NIST.800-53.r5 SC-36, NIST.800-53.r5 SC-5(2), NIST.800-53.r5 SI-13(5)

Category: Recover > Resilience > High Availability

Severity: Medium

Resource type: AWS::Lambda::Function

Amazon Config rule: lambda-vpc-multi-az-check

Schedule type: Change triggered

Parameters:

This control checks if an Amazon Lambda function that connects to a virtual private cloud (VPC) operates in at least the specified number of Availability Zone (AZs). The control fails if the function doesn't operate in at least the specified number of AZs. Unless you provide a custom parameter value for the minimum number of AZs, Security Hub uses a default value of two AZs.

Deploying resources across multiple AZs is an Amazon best practice to ensure high availability within your architecture. Availability is a core pillar in the confidentiality, integrity, and availability triad security model. All Lambda functions that connect to a VPC should have a multi-AZ deployment to ensure that a single zone of failure doesn't cause a total disruption of operations.

Remediation

If you configure your function to connect to a VPC in your account, specify subnets in multiple AZs to ensure high availability. For instructions, see Configuring VPC access in the Amazon Lambda Developer Guide.

Lambda automatically runs other functions in multiple AZs to ensure that it is available to process events in case of a service interruption in a single zone.

[Lambda.6] Lambda functions should be tagged

Category: Identify > Inventory > Tagging

Severity: Low

Resource type: Amazon::Lambda::Function

Amazon Config rule: tagged-lambda-function (custom Security Hub rule)

Schedule type: Change triggered

Parameters:

This control checks whether an Amazon Lambda function has tags with the specific keys defined in the parameter requiredTagKeys. The control fails if the function doesn’t have any tag keys or if it doesn’t have all the keys specified in the parameter requiredTagKeys. If the parameter requiredTagKeys isn't provided, the control only checks for the existence of a tag key and fails if the function isn't tagged with any key. System tags, which are automatically applied and begin with aws:, are ignored.

A tag is a label that you assign to an Amazon resource, and it consists of a key and an optional value. You can create tags to categorize resources by purpose, owner, environment, or other criteria. Tags can help you identify, organize, search for, and filter resources. Tagging also helps you track accountable resource owners for actions and notifications. When you use tagging, you can implement attribute-based access control (ABAC) as an authorization strategy, which defines permissions based on tags. You can attach tags to IAM entities (users or roles) and to Amazon resources. You can create a single ABAC policy or a separate set of policies for your IAM principals. You can design these ABAC policies to allow operations when the principal's tag matches the resource tag. For more information, see What is ABAC for Amazon? in the IAM User Guide.

Remediation

To add tags to a Lambda function, see Using tags on Lambda functions in the Amazon Lambda Developer Guide.