Serverless functions compliance checks

Prisma Cloud Labs has developed compliance checks for serverless functions. Currently, only AWS Lambda is supported.
In AWS Lambda, every function has an execution role. Execution roles are identities with permission policies that control what functions can and cannot do in AWS. When you create a function, you specify an execution role. When the function is invoked, it assumes this role.
When Prisma Cloud scans the functions in your environment, it inspects the execution role for overly permissive access to AWS services and resources. Two fields are inspected:
resource
and
action
.

Resource

Specifies the objects to which the permission policy applies. Resources are specified with ARNs. ARNs let you unambiguously specify a resource across all of AWS. ARNs have the following format:
arn:partition:service:region:account-id:resource
Where:
  • service
     — Identifies the AWS product, such as Amazon S3, IAM, or CloudWatch Logs.
  • resource
     — Identies the objects in the service. It often includes the resource type, followed by the resource name itself. For example, the following ARN uniquely identifies the user Francis in the IAM service:
    arn:aws:iam::586975633310:user/Francis

Action

Describes the tasks that can be performed on the service. For example, ec2:StartInstances, iam:ChangePassword, and s3:GetObject. Wildcards can be used to grant access to all the actions of a given AWS service. For example, s3:* applies to all S3 actions.

Types of issues

The following permission policy is tightly scoped. It grants read-write only access to the Books table. Prisma Cloud would not flag an execution role with this type of permissions policy.
{ "Version": "2012-10-17", "Statement": { "Effect": "Allow", "Action": [ "dynamodb:GetItem", "dynamodb:BatchGetItem" ], "Resource": "arn:aws:dynamodb:us-east-1:125643784111:table/Books" } }
The following permissions policy has been implemented carelessly. It allows all DyanmoDB operations on all tables owned by the AWS account in the current region, including dynamodb:DeleteTable, which has serious implications for the integrity and availability of your data. This type of configuration would raise compliance check 437 because the execution role permits all DyanmoDB operations, and it’s unlikely a function actually needs this range of capabilities.
{ "Version": "2012-10-17", "Statement": { "Sid": "AllAPIActionsOnBooks", "Effect": "Allow", "Action": "dynamodb:*", "Resource": "*" } }

Compliance check details

The following checks are supported:
  • 434: Sensitive information provided in environment variables
    --
    Detects when functions contain environments vars, such as MYSQL_PASSWORD, that expose sensitive information.
  • 435: Private keys stored in function
    --
    Detects private keys in functions.
  • 436: Unbounded service access
    --
    Detects functions that have permission to run all actions on all services and their resources.
  • 437: Overly permissive service access
    --
    Detects functions that have permission to run all actions on one or more services.
  • 438: Broad resource access
    --
    Detects functions that granted access to all resources in one or more services.
  • 439: Suspicious function actions
    --
    Detects functions that have permission to run actions that are used in exploits and attacks. Includes things like cloudtrail:StopLogging, cloudtrail:UpdateTrail that allow disabling and changing the output of CloudTrail logging.

Scanning serverless functions

Configure Prisma Cloud to periodically scan your serverless functions. Function scanning is handled by Defender. Console dynamically selects an available Defender to execute the scan job.
  1. Open Console.
  2. Go to
    Defend > Vulnerabilities > Functions
    .
  3. Click
    Add serverless account
    .
  4. In the dialog, enter the following settings:
    1. In
      Provider
      , select
      AWS Lambda
      .
    2. Specify a Region.
    3. Specify a function name.
      Wildcards are supported. See the table at the top of the page for the supported syntax and examples.
    4. Select or create credentials so that Prisma Cloud can access your account.
      Specify either an AWS IAM user credential (access key ID and secret access key) or IAM role.
    5. Specify a cap for the number of functions to scan.
      Prisma Cloud scans the X most recent functions, where X is the cap value.
    6. Click
      Add
      .
  5. Click the yellow save button.
    save_button.png
  6. To view the scan report, go to
    Monitor > Compliance > Functions
    .

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