1. Overview

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.

2. 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.

3. 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. Specify a cap for the number of functions to scan.

      Prisma Cloud scans the X most recent functions, where X is the cap value. Set this value to '0' to scan all functions.
    2. (AWS only) Specify which regions to scan. By default, the scope is applied to Regular regions. Other options include China regions or Goverment regins.

    3. (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 cap value.

    4. (AWS only) Select Scan Lambda Layers to enable scanning function layers as well.

    5. Select the accounts to scan by credential. If you wish to add an account, click on Add credential.

    6. Click Add.

  4. Click the green save button.

  5. View the scan report.

    Go to Monitor > Vulnerabilities > Functions > Scanned functions.

4. 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

    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:*

    function vuls layers filter
  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.

      vul function details
    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.

      vuls functions layers info

5. Authenticating with AWS

The serverless scanner is implemented as part of Console. The scanner requires the AWSLambdaReadOnlyAccess permissions policy.

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. For more on how to use AWS STS, see here.

When authenticating with an IAM user, Console can access and scan functions across multiple regions.

IAM Role

The Prisma Cloud serverless scanner can also authenticate with AWS using an IAM role. If Console authenticates with AWS using an IAM role, it can assume roles using STS to assume roles in other regions.

6. 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 only scans Linux 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. Log into your account with a user that has the User Account Administrator role.

    $ az login
  2. Get the service key.

    $ az ad sp create-for-rbac --sdk-auth --name twistlock-azure-serverless-scanning --role contributor

    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",
      "resourceManagerEndpointUrl": "https://management.azure.com/",
      "activeDirectoryGraphResourceId": "https://graph.windows.net/",
      "sqlManagementEndpointUrl": "https://management.core.windows.net:8443/",
      "galleryEndpointUrl": "https://gallery.azure.com/",
      "managementEndpointUrl": "https://management.core.windows.net/"
    }
  3. Copy the JSON output, which is your secret key, and paste it into the Service Key field for your Azure credentials in Prisma Cloud Console.

7. Scanning functions at build time with twistcli

You can also use the twistcli command line utility to scan your serverless functions. First download your serverless function as a ZIP file, then run:

$ twistcli serverless scan <SERVERLESS_FUNCTION.ZIP>

To view scan reports in Console, go to Monitor > Vulnerabilities > Functions > CI or Monitor > Compliance > Functions > CI.

7.1. Twistcli Options

--address URI

Required. Complete URI for Console, including the protocol and port. Only the HTTPS protocol is supported. By default, Console listens to HTTPS on port 8083, although your administrator can configure Console to listen on a different port.

-u, --user USERNAME

Username to access Console. If not provided, the TWISTLOCK_USER environment variable will be used if defined, or "admin" is used as the default.

-p, --password PASSWORD

Password for the user specified with -u, --user. If not specified on the command-line, the TWISTLOCK_PASSWORD environment variable will be used if defined, or otherwise will prompt for the user’s password before the scan runs.

--project PROJECT NAME

Interface with a specific supervisor Console to retrieve policy and publish results.

Example: --project "Tenant Console"

--details

Show all vulnerability details.

--tlscacert PATH

Path to Prisma Cloud CA certificate file. If no CA certificate is specified, the connection to Console is insecure.

--include-js-dependencies

Include javascript package dependencies.

--token TOKEN

Token to use for Prisma Cloud Console authentication. Tokens can be retrieved from the API endpoint api/v1/authenticate or from the Manage > Authenticate > User Certificates page in Console.

--cloudformation-template PATH

Path to the CloudFormation template file in JSON or YAML format. Prisma Cloud scans the function source code for AWS service APIs being used, compares the APIs being used to the function permissions, and reports when functions have permissions for APIs they don’t need.

--function NAME

Function name to be used in policy detection and Console results. When creating policy rules in Console, you can target specific rules to specific functions by function name. If this field is left unspecified, the function zip file name is used.

--output-used-apis

Report APIs used by the function

--publish

Publish the scan result to the Console. True by default.