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. 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
    .

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
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
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 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
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  2. Get the service key.
    $ az ad sp create-for-rbac --sdk-auth --name twistlock-azure-serverless-scanning --role contributor
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    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/" }
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  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.

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

Twistcli Options

To get the address for your Console, go to
Compute > Manage > System > Downloads
, and copy the string under
Path to Console
.
Access Key ID and Secret Key are generated from the Prisma Cloud user interface. For more information, see access keys
  • Show all vulnerability details.
  • Path to Prisma Cloud CA certificate file. If no CA certificate is specified, the connection to Console is insecure.
  • Include javascript package dependencies.
  • 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.
  • 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 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.
  • Report APIs used by the function
  • Publish the scan result to the Console. True by default.

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