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    6. Serverless functions compliance checks

    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 environment variables (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 with permission to run all actions on all services and their resources.
    • 437: Overly permissive service access
       --
      Detects functions with permission to run all actions on one or more services.