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    Scan images with twistcli

    Prisma Cloud ships a command-line scanner for scanning container images and serverless functions. It is supported on Linux, macOS, and Windows.

    Command reference

    The twistcli command has several subcommands. Use the twistcli images scan subcommand to invoke the scanner.

    Projects

    When users from a tenant project run twistcli, they must set the --project option to specify the proper context for the command.

    Command

    twistcli images scan — Scan an image for vulnerabilities and compliance issues. The image must reside on the system where twistcli runs. If not, retrieve the image with docker pull before scanning it. Twistcli does not pull images for you.

    Description

    The twistcli images scan function collects information about the packages and binaries in the container image, and then sends it to Console for analysis.
    Data collected by twistcli includes:
    • Packages in the image.
    • Files installed by each package.
    • Hashes for files in the image.
    After Console analyzes the image for vulnerabilities, twistcli:
    • Outputs a summary report.
    • Exits with a pass or fail return value.
    Scan results can be retrieved in JSON format from the Console using API calls.
    To specify an image to scan, use either the image ID, or repository name and tag. The image should be present on the system, having either been built or pulled there. If a repository is specified without a tag, twistcli looks for an image tagged latest.
    When invoking twistcli, the last parameter should be the image to scan. If you list options after the image, they will be ignored.

    Options

    RETURN VALUE

    The exit code is 0 if twistcli images scan finds no vulnerabilities or compliance issues. Otherwise, the exit code is 1.
    The criteria for passing or failing a scan is determined by the CI vulnerability and compliance policies set in Console. The default CI vulnerability policy alerts on all CVEs detected. The default CI compliance policy alerts on all critical and high compliance issues.
    There are two reasons why twistcli images scan might return an exit code of 1.
    • The scan failed because the scanner found issues that violate your CI policy.
    • Twistcli failed to run due to an error.
    Although the return value is ambiguous — you cannot determine the exact reason for the failure by just examining the return value — this setup supports automation. From an automation process perspective, you expect that the entire flow will work. If you scan an image, with or without a threshold, either it works or it does not work. If it fails, for whatever reason, you want to fail everything because there is a problem.

    Scan results

    To view scan reports in Console, go to
    Monitor > Vulnerabilities > Images > CI
     or
    Monitor > Compliance > Images > CI
    .
    You can also retrieve scan reports in JSON format using the Prisma Cloud API, see the API section.

    Output

    The twistcli tool can output scan results to several places:
    • stdout.
    • File. Scan results are saved in JSON format.
    • Console. Scan results can be viewed under
      Monitor > Vulnerabilities > Images > CI
      .
    By passing certain flags, you can adjust how the twistcli scan output looks and where it goes. By default, twistcli writes scan results to stdout and sends the results to Console.
    To write scan results to stdout in tabular format, pass the --details flag to twistcli. This does not affect where the results are sent.
    To write scan results to a file in JSON format, pass the --output-file flag to twistcli. If you specify an output file, then results cannot be sent to Console.

    API

    You can retrieve scan reports in JSON format using the Prisma Cloud Compute API. The API returns comprehensive information for each scan report, including the full list of packages, files, and vulnerabilities.
    The following example curl command calls the API with Basic authentication. You’ll need to apply some filtering with tools like jq to extract specific items from the response. For more information on accessing the API, see Accessing the API.
    $ curl \
  -u <COMPUTE_CONSOLE_USER> \
  -o scan_results.json \
  'https://<COMPUTE_CONSOLE>/api/v1/scans?type=ciImage'
    If you are using assigned collections, then specify the collection in a query parameter:
    $ curl \
  -u <COMPUTE_CONSOLE_USER> \
  -o scan_results.json \
  'https://<COMPUTE_CONSOLE>/api/v1/scans?type=ciImage&collections=<COLLECTION_NAME>'

    Dockerless scan

    By default, twistcli is run from outside the container image.

    Podman Twistcli scans

    Twistcli can run scans on Podman hosts. Use --podman-path PATH to specify the path to podman and force the twistcli scanner to use podman. For additional information, see the Podman section.

    Running from inside of the container

    In some cases, you might need to copy twistcli to the container’s file system, and then run the scanner from inside the container.
    One reason you might want to run the scanner this way is when your build platform doesn’t give you access to the Docker socket. CodeFresh is an example of such a platform.
    There are some shortcomings with scanning from inside a container, so you should only use this approach when no other approach is viable. The shortcomings are:
    • Automating the scan in your continuous integration pipeline is more difficult.
    • Image metadata, such as registry, repository, and tag aren’t available in the scan report. When twistcli is run from outside the container, this information is retrieved from the Docker API.
    • The image ID isn’t available in the scan report because it cannot be determined when the scan is run from inside a container.
    • The scan report won’t show a layer-by-layer analysis of the image.

    Usage

    When running the scanner from inside a container, you need to properly orient it by passing it the --containerized flag. There are a couple of ways to run twistcli with the --containerized flag: build-time and run-time.
    For security reasons, Prisma Cloud recommends that you create a user with the CI User role for running scans.

    Build-time invocation

    After building an image, run it. Mount the host directory that holds the twistcli binary, pass the Prisma Cloud Console user credentials to the container with environment variables, then run the scanner inside the container. The <REPORT_ID> is a user defined string that uniquely identifies the scan report in the Console UI.
    $ docker run \
  -v /PATH/TO/TWISTCLIDIR:/tools \
  -e TW_USER=<COMPUTE_CONSOLE_USER> \
  -e TW_PASS=<COMPUTE_CONSOLE_PASSWD> \
  -e TW_CONSOLE=<COMPUTE_CONSOLE> \
  --entrypoint="" \
  <IMAGE_NAME> \
  /tools/twistcli images scan \
    --containerized \
    --details \
    --address $TW_CONSOLE \
    --user $TW_USER \
    --password $TW_PASS \
    <REPORT_ID>
    Rather than username and password, twistcli can also authenticate to Console with a token. Your API token can be found in Console under
    Manage > Authentication > User Certificates > API token
    . For security reasons, API tokens expire.
    $ docker run \
  -v /PATH/TO/TWISTCLI_DIR:/tools \
  -e TW_TOKEN=<API_TOKEN> \
  -e TW_CONSOLE=<COMPUTE_CONSOLE> \
  --entrypoint="" \
  <IMAGE_NAME> \
  /tools/twistcli images scan \
    --containerized \
    --details \
    --address $TW_CONSOLE \
    --token $TW_TOKEN \
    <REPORT_ID>

    Run-time invocation

    If you have access to the orchestrator, you can exec into the running container to run the twistcli scanner. Alternatively, you could SSH to the container. Once you have a shell on the running container, invoke the scanner:
    $ ./twistcli images scan \
  --address <COMPUTE_CONSOLE> \
  --user <COMPUTE_CONSOLE_USER> \
  --password <COMPUTE_CONSOLE_PASSWD> \
  --containerized \
  <REPORT_ID>
    To invoke the scanner with an API token:
    $ ./twistcli images scan \
  --address <COMPUTE_CONSOLE> \
  --token <API_TOKEN> \
  --containerized \
  <REPORT_ID>

    Simple scan

    Scan an image with twistcli and print the summary report to stdout.
    1. Scan an image named myimage:latest.
      $ twistcli images scan \
  --address <COMPUTE_CONSOLE> \
  --user <COMPUTE_CONSOLE_USER> \
  --password <COMPUTE_CONSOLE_PASSWD> \
  myimage:latest
      Command output:

    Scan with detailed report

    You can have twistcli generate a detailed report for each scan. The following procedure shows you how to scan an image with twistcli, and then retrieve the results from Console.
    1. Scan an image named myimage:latest.
      $ twistcli images scan \
  --address <COMPUTE_CONSOLE> \
  --user <COMPUTE_CONSOLE_USER> \
  --password <COMPUTE_CONSOLE_PASSWD> \
  --details \
  myimage:latest
      Sample command output (results have been truncated):
    2. This outputs a tabular representation of your scan results to stdout. If you need to retrieve the results of your scan in JSON format, this can be done using the API. For more information on the API, refer to Accessing the API.
      1. Call the API with authentication (demonstrated here using Basic authentication) to fetch the results of the scan.
        $ curl \
  -o scan_results.json \
  -H 'Authorization: Basic YXBpOmFwaQ==' \
  'https://<COMPUTE_CONSOLE>/api/v1/scans?search=myimage&limit=1&reverse=true&type=ciImage'
      2. Format the scan results into human-readable format.
        $ python -m json.tool scan_results.json > scan_results_pp.json
      3. Inspect the results.
        Open scan_results_pp.json to view the results. Vulnerability information can be found in the vulnerabilities array, and compliance results can be found in the complianceIssues array.
        [
  {
    "entityInfo": {
      "_id": "",
      "type": "ciImage",
      ...
      "complianceIssues": [
        {
          "text": "",
          "id": 41,
          "severity": "high",
          "cvss": 0,
          "status": "",
          "cve": "",
          "cause": "",
          "description": "It is a good practice to run the container as a non-root user, if possible. Though user\nnamespace mapping is now available, if a user is already defined in the container image, the\ncontainer is run as that user by default and specific user namespace remapping is not\nrequired",
          "title": "(CIS_Docker_CE_v1.1.0 - 4.1) Image should be created with a non-root user",
          "vecStr": "",
          "exploit": "",
          "riskFactors": null,
          "link": "",
          "type": "image",
          "packageName": "",
          "packageVersion": "",
          "layerTime": 0,
          "templates": [],
          "twistlock": false,
          "published": 0,
          "discovered": "0001-01-01T00:00:00Z"
        }
      ],
      ...
      "vulnerabilities": [
        {
          "text": "",
          "id": 46,
          "severity": "medium",
          "cvss": 9.8,
          "status": "deferred",
          "cve": "CVE-2018-20839",
          "cause": "",
          "description": "systemd 242 changes the VT1 mode upon a logout, which allows attackers to read cleartext passwords in certain circumstances, such as watching a shutdown, or using Ctrl-Alt-F1 and Ctrl-Alt-F2. This occurs because the KDGKBMODE (aka current keyboard mode) check is mishandled.",
          "title": "",
          "vecStr": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "exploit": "",
          "riskFactors": {
            "Attack complexity: low": {},
            "Attack vector: network": {},
            "Medium severity": {}
          },
          "link": "https://people.canonical.com/~ubuntu-security/cve/2018/CVE-2018-20839",
          "type": "image",
          "packageName": "systemd",
          "packageVersion": "237-3ubuntu10.39",
          "layerTime": 1587690420,
          "templates": [],
          "twistlock": false,
          "published": 1558067340,
          "discovered": "0001-01-01T00:00:00Z",
          "binaryPkgs": [
            "libnss-systemd",
            "libsystemd0",
            "libpam-systemd",
            "udev",
            "systemd-sysv",
            "libudev1",
            "systemd"
          ]
        },
        ...
      ],
      ...
    },
    ...
  }
]

    Scan images built with Jenkins in an OpenShift environment

    If you are building and deploying images on OpenShift Container Platform (OCP), and you are utilizing their Jenkins infrastructure, then invoke a scan with the twistcli hosts scan command, not the twistcli images scan command.
    You can scan images generated by Jenkins with the OpenShift plugin by invoking twistcli from a build hook. Build hooks let you inject custom logic into the build process. They run your commands inside a temporary container instantiated from build output image. Build hooks are called when the last layer of the image has been committed, but before the image is pushed to a registry. An non-zero exit code fails the build. A zero exit code passes the build, and allows it to proceed to the next step.
    To call twistcli from a build hook:
    1. Download twistcli into your build environment. Depending on your build strategy, one option is to download it as an external artifact using a save-artifacts S2I script.
    2. In your BuildConfig, call twistcli as a script from the postCommit hook.