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    6. Serverless function scanning

    Serverless function scanning

    Prisma Cloud can scan serverless functions for vulnerabilities. Prisma Cloud supports AWS Lambda, Google Cloud Functions, and Azure Functions.
    Serverless computing is an execution model in which a cloud provider dynamically manages the allocation of machine resources and schedules the execution of functions provided by users. Serverless architectures delegate the operational responsibilities, along with many security concerns, to the cloud provider. In particular, your app itself is still prone to attack. The vulnerabilities in your code and associated dependencies are the footholds attackers use to compromise an app. Prisma Cloud can show you a function’s dependencies, and surface the vulnerabilities in those dependent components.

    Capabilities

    For serverless, Prisma Cloud can scan Node.js, Python, Java, C#, Ruby, and Go packages. For a list of supported runtimes see system requirements.
    Prisma Cloud scans are triggered by the following events:
    • When the settings change, including when new functions are added for scanning.
    • When you explicitly click the
      Scan
       button in the
      Monitor > Vulnerabilities > Functions > Scanned Functions
       page.
    • Periodically. By default, Prisma Cloud rescans serverless functions every 24 hours, but you can configure a custom interval in
      Manage > System > Scan
      .

    Scanning a serverless function

    Configure Prisma Cloud to periodically scan your serverless functions. Unlike image scanning, all function scanning is handled by Console.
    1. Open Console.
    2. Go to
      Defend > Vulnerabilities > Functions > Functions
      .
    3. Click on
      Add scope
      . In the dialog, enter the following settings:
      1. (AWS only) Select
        Scan only latest versions
         to only scan the latest version of each function. Otherwise, the scanning will cover all versions of each function up to the specified
        Limit
         value.
      2. (AWS only) Select
        Scan Lambda Layers
         to enable scanning function layers as well.
      3. (AWS only) Specify which regions to scan in
        AWS Scanning scope
        . By default, the scope is applied to
        Regular regions
        . Other options include
        China regions
         or
        Government regions
        .
      4. Specify a
        Limit
         for the number of functions to scan.
        Prisma Cloud scans the X most recent functions, where X is the limit value. Set this value to '0' to scan all functions.
        For scanning Google Cloud Functions with GCP organization level credentials, the limit value is for the entire organization. Increase the limit as needed to cover all the projects within your GCP organization.
      5. Select the accounts to scan by credential. If you wish to add an account, click on
        Add credential
        .
        If you create a credential in the credentials store (
        Manage > Authentication > Credentials store
        ), your service principal authenticates with a password. To authenticate with a certificate, create a cloud account.
      6. Click
        Add
        .
    4. Click the green save button.
    5. View the scan report.
      Go to
      Monitor > Vulnerabilities > Functions > Scanned functions
      .
      All vulnerabilities identified in the latest serverless scan report can be exported to a CSV file by clicking on the CSV button in the top right of the table.

    View AWS Lambda Layers scan report

    Prisma Cloud can scan the AWS Lambda Layers code as part of the Lambda function’s code scanning. This capability can help you determine whether the vulnerability issues are associated with the function or function Layers. Follow the steps below to view the Lambda Layers scan results:
    1. Open Console.
    2. Make sure you selected the
      Scan Lambda layers
       in the Defend > Vulnerabilities > Functions > Functions > Serverless Accounts >
      Function scan scope
    3. Go to
      Monitor > Vulnerabilities > Functions > Scanned functions
      .
    4. Filter the table to include functions with the desired Layer by adding the
      Layers
       filter.
      You can also filter the results by a specific layer name or postfix wildcards. Example: Layers:* OR Layers:arn:aws:lambda:*
    5. Open the
      Function details
       dialog to view the details about the Layers and the vulnerabilities associated with them:
      1. Click on a specific function
      2. See the Function’s vulnerabilities, compliance issues and package info in the related tabs. Use the
        Found in
         column to determine if the component is associated with the Function or with the Function’s Layers.
      3. Use the
        Layers info
         tab to see the full list of the Function’s Layers, and aggregated information about the Layers vulnerabilities. In case that there are vulnerabilities associated with the layer you will be able to expand the layer raw to list all the vulnerabilities.

    Authenticating with AWS

    The serverless scanner is implemented as part of Console. The scanner requires the following permissions policy:
    +
    {
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "PrismaCloudComputeServerlessScan",
            "Effect": "Allow",
            "Action": [
                "lambda:ListFunctions",
                "lambda:GetFunction",
                "iam:GetPolicy",
                "iam:GetPolicyVersion",
                "iam:GetRole",
                "iam:GetRolePolicy",
                "iam:ListAttachedRolePolicies",
                "iam:ListRolePolicies",
                "lambda:GetLayerVersion",
                "kms:Decrypt"
            ],
            "Resource": "*"
        }
    ]
}
    IAM User
    If authenticating with an IAM user, use the Security Token Service (STS) to temporarily issue security credentials to Prisma Cloud to scan your Lambda functions. AWS STS is considered a best practice for IAM users per the AWS Well-Architected Framework. Learn how to use AWS STS.
    When authenticating with an IAM user, Console can access and scan functions across multiple regions.
    IAM Role
    IAM roles cannot be used in Prisma Cloud serverless scanning as the Console is not hosted within AWS for Enterprise Edition.

    Scanning Azure Functions

    Azure Functions are architected differently than AWS Lambda and Google Cloud Functions. Azure function apps can hold multiple functions. The functions are not segregated from each other. They share the same file system. Rather than separately scanning each function in a function app, download the root directory of the function app, which contains all its functions, and scan them as a bundle.
    Prisma Cloud supports scanning both Windows and Linux functions. For Linux functions, the support is only for functions that use
    External package URL
     as the deployment technology. For more information, see Deployment technologies in Azure Functions.
    To do this, you must know the Region, Name (of the function), and Service Key. To get the Service Key, download and install the Azure CLI, then:
    1. Within your Azure portal, create a custom role with the following permissions:
      {
    "permissions": [
        {
            "actions": [
                "Microsoft.Web/sites/Read",
                "Microsoft.Web/sites/config/list/Action",
                "Microsoft.web/sites/functions/action",
                "Microsoft.web/sites/functions/read",
                "Microsoft.Web/sites/publishxml/Action"
            ],
            "notActions": [],
            "dataActions": [],
            "notDataActions": []
        }
    ]
}
    2. Using the CLI, log into your account with a user that has the User Administrator role.
      $ az login
    3. Get the service key.
      $ az ad sp create-for-rbac --sdk-auth --name twistlock-azure-serverless-scanning --role CUSTOM_ROLE_NAME
      Sample output from the previous command:
      {
  "clientId": "f8e9de2o-45bd-af94-ae11-b9r8c5tfy3b6",
  "clientSecret": "4dfds482-6sdd-4dsb-b5ff-56123043c4dc",
  "subscriptionId": "ea19322m-z2bd-501c-dd11-234m547a944e",
  "tenantId": "c189c61a-6c27-41c3-9949-ca5c8cc4a624",
  "activeDirectoryEndpointUrl": "https://login.microsoftonline.com",