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scout: create exceptions in dashboard #20581

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335 changes: 61 additions & 274 deletions content/scout/explore/exceptions.md
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Expand Up @@ -9,9 +9,8 @@ keywords: scout, cves, suppress, vex, exceptions

Vulnerabilities found in container images sometimes need additional context.
Just because an image contains a vulnerable package, it doesn't mean that the
vulnerability is exploitable. **Exceptions** in Docker Scout lets you address
false positives in image analysis using Vulnerability Exploitability
eXchange (VEX) documents.
vulnerability is exploitable. **Exceptions** in Docker Scout lets you
acknowledge accepted risks or address false positives in image analysis.

By negating non-applicable vulnerabilities, you can make it easier for yourself
and downstream consumers of your images to understand the security implications
Expand All @@ -21,296 +20,84 @@ In Docker Scout, exceptions are automatically factored into the results.
If an image contains an exception that flags a CVE as non-applicable,
then that CVE is excluded from analysis results.

## Create an exception
## Create exceptions

To add an exception to an image, you need a VEX document. VEX is a standard
format for documenting vulnerabilities in the context of a software package or
product.
To create an exception for an image, you can:

There are multiple implementations and formats of VEX. Docker Scout supports
the [OpenVex](https://github.com/openvex/spec) implementation. To create an
OpenVEX document, use the [`vexctl`](https://github.com/openvex/vexctl) command
line tool.
- Create an exception in the [GUI](/scout/how-tos/create-exceptions-gui.md) of
Docker Scout Dashboard.

The following example command creates a VEX document stating that:
- Create a [VEX](/scout/how-tos/create-exceptions-vex.md) document and attach
it to the image.

- The software product described by this VEX document is the Docker image
`example/app:v1`
- The image contains the npm package `[email protected]`
- The npm package is affected by a known vulnerability: `CVE-2022-24999`
- The image is unaffected by the CVE, because the vulnerable code is never
executed in containers that run this image
The recommended way to create exceptions is to use Docker Scout Dashboard. The
GUI provides a user-friendly interface for creating exceptions. It also lets
you create exceptions for multiple images, or your entire organization, all at
once.

```console
$ vexctl create \
--author="[email protected]" \
--product="pkg:docker/example/app@v1" \
--subcomponents="pkg:npm/[email protected]" \
--vuln="CVE-2022-24999" \
--status="not_affected" \
--justification="vulnerable_code_not_in_execute_path" \
--file="CVE-2022-24999.vex.json"
```

Here's a description of the options in this example:

`--author`
: The email of the author of the VEX document.

`--product`
: Package URL (PURL) of the Docker image. A PURL is an identifier
for the image in a standardized format, defined in the PURL
[specification](https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst#docker).

Docker image PURL strings begin with a `pkg:docker` type prefix, followed by
the image repository and version (the image tag or SHA256 digest). Unlike
image tags, where the version is specified like `example/app:v1`, in PURL the
image repository and version are separated by an `@`.

`--subcomponents`
: PURL of the vulnerable package in the image. In this example, the
vulnerability exists in an npm package, so the `--subcomponents` PURL is the
identifier for the npm package name and version (`pkg:npm/[email protected]`).

If the same vulnerability exists in multiple packages, `vexctl` lets you
specify the `--subcomponents` flag multiple times for a single `create`
command.

You can also omit `--subcomponents`, in which case the VEX statement applies
to the entire image.

`--vuln`
: ID of the CVE that the VEX statement addresses.

`--status`
: This is the status label of the vulnerability. This describes the
relationship between the software (`--product`) and the CVE (`--vuln`).
The possible values for the status label in OpenVEX are:

- `not_affected`
- `affected`
- `fixed`
- `under_investigation`

In this example, the VEX statement asserts that the Docker image is
`not_affected` by the vulnerability. The `not_affected` status is the only
status that results in CVE suppression, where the CVE is filtered out of the
analysis results. The other statuses are useful for documentation purposes,
but they do not work for creating exceptions. For more information about all
the possible status labels, see [Status Labels](https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md#status-labels)
in the OpenVEX specification.

`--justification`
: Justifies the `not_affected` status label, informing why the product is not
affected by the vulnerability. In this case, the justification given is
`vulnerable_code_not_in_execute_path`, signalling that the vulnerability
can't be executed as used by the product.

In OpenVEX, status justifications can have one of the five possible values:

- `component_not_present`
- `vulnerable_code_not_present`
- `vulnerable_code_not_in_execute_path`
- `vulnerable_code_cannot_be_controlled_by_adversary`
- `inline_mitigations_already_exist`

For more information about these values and their definitions, see
[Status Justifications](https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md#status-justifications)
in the OpenVEX specification.

`--file`
: Filename of the VEX document output

Here's the OpenVEX JSON generated by this command:

```json
{
"@context": "https://openvex.dev/ns/v0.2.0",
"@id": "https://openvex.dev/docs/public/vex-749f79b50f5f2f0f07747c2de9f1239b37c2bda663579f87a35e5f0fdfc13de5",
"author": "[email protected]",
"timestamp": "2024-05-27T13:20:22.395824+02:00",
"version": 1,
"statements": [
{
"vulnerability": {
"name": "CVE-2022-24999"
},
"timestamp": "2024-05-27T13:20:22.395829+02:00",
"products": [
{
"@id": "pkg:docker/example/app@v1",
"subcomponents": [
{
"@id": "pkg:npm/[email protected]"
}
]
}
],
"status": "not_affected",
"justification": "vulnerable_code_not_in_execute_path"
}
]
}
```

Understanding how VEX documents are supposed to be structured can be a bit of a
mouthful. The [OpenVEX specification](https://github.com/openvex/spec)
describes the format and all the possible properties of documents and
statements. For the full details, refer to the specification to learn more
about the available fields and how to create a well-formed OpenVEX document.

To learn more about the available flags and syntax of the `vexctl` CLI tool and
how to install it, refer to the [`vexctl` GitHub repository](https://github.com/openvex/vexctl).

For an introduction to VEX, you may also want to check out this use-case guide:
[Suppress image vulnerabilities with VEX](/scout/guides/vex.md).

## Verifying VEX documents

To test whether the VEX documents you create are well-formed and produce the
expected results, use the `docker scout cves` command with the `--vex-location`
flag to apply a VEX document to a local image analysis using the CLI.

The following command invokes a local image analysis that incorporates all VEX
documents in the specified location, using the `--vex-location` flag. In this
example, the CLI is instructed to look for VEX documents in the current working
directory.

```console
$ docker scout cves <IMAGE> --vex-location .
```

The output of the `docker scout cves` command displays the results with any VEX
statements found in under the `--vex-location` location factored into the
results. For example, CVEs assigned a status of `not_affected` are filtered out
from the results. If the output doesn't seem to take the VEX statements into
account, that's an indication that the VEX documents might be invalid in some
way.

Things to look out for include:

- The PURL of a Docker image must begin with `pkg:docker/` followed by the image name.
- In a Docker image PURL, the image name and version is separated by `@`.
An image named `example/myapp:1.0` has the following PURL: `pkg:docker/example/[email protected]`.
- Remember to specify an `author` (it's a mandatory field in OpenVEX)
- The [OpenVEX specification](https://github.com/openvex/spec) describes how
and when to use `justification`, `impact_statement`, and other fields in the
VEX documents. Specifying these in an incorrect way results in an invalid
document. Make sure your VEX documents comply with the OpenVEX specification.

## Attach exceptions to images

When you've created an exception,
you can attach it to your image in the following ways:

- Attach the document as an [attestation](#attestation)
- Embed the document in the [image filesystem](#image-filesystem)

You can't remove a VEX document from an image once it's been added. For
documents attached as attestations, you can create a new VEX document and
attach it to the image again. Doing so will overwrite the previous VEX document
(but it won't remove the attestation). For images where the VEX document has
been embedded in the image's filesystem, you need to rebuild the image to
change the VEX document.

### Attestation

To attach exceptions as an attestation, you can use the `docker scout
attestation add` CLI command. Using attestations is the recommended option for attaching exceptions to
images.
## View exceptions

You can attach attestations to images that have already been pushed to a
registry. You don't need to build or push the image again. Additionally, having
the exceptions attached to the image as attestations means consumers can
inspect the exceptions for an image, directly from the registry.
To view exceptions for images, you need to have the appropriate permissions.

To attach an attestation to an image:
- Exceptions created [using the GUI](/scout/how-tos/create-exceptions-gui.md)
are visible to members of your Docker organization. Unauthenticated users or
users who aren't members of your organization cannot see these exceptions.
- Exceptions created [using VEX documents](/scout/how-tos/create-exceptions-vex.md)
are visible to anyone who can pull the image, since the VEX document is
stored in the image manifest or on filesystem of the image.

1. Build the image and push it to a registry.
### View exceptions in Docker Scout Dashboard

```console
$ docker build --provenance=true --sbom=true --tag <IMAGE> --push .
```
The [**Exceptions** tab](https://scout.docker.com/reports/vulnerabilities/exceptions)
of the Vulnerabilities page in Docker Scout Dashboard lists all exceptions for
for all images in your organization. From here, you can see more details about
each exception, the CVEs being suppressed, the images that exceptions apply to,
the type of exception and how it was created, and more.

2. Attach the exception to the image as an attestation.
For exceptions created using the [GUI](/scout/how-tos/create-exceptions-gui.md),
selecting the action menu lets you edit or remove the exception.

```console
$ docker scout attestation add \
--file <cve-id>.vex.json \
--predicate-type https://openvex.dev/ns/v0.2.0 \
<IMAGE>
```
To view all exceptions for a specific image tag:

The options for this command are:
1. Go to the [Images page](https://scout.docker.com/reports/images).
2. Select the tag that you want to inspect.
3. Open the **Exceptions** tab.

- `--file`: the location and filename of the VEX document
- `--predicate-type`: the in-toto `predicateType` for OpenVEX
### View exceptions in the CLI

### Image filesystem
{{% experimental %}}
Viewing exceptions in the CLI is an experimental feature.
It requires the latest version of the Docker Scout CLI plugin.
Some exceptions may not appear correctly in the CLI.
{{% /experimental %}}

Embedding exceptions directly on the image filesystem is a good option if you
know the exceptions ahead of time, before you build the image. And it's easy;
just `COPY` the VEX document to the image in your Dockerfile.
Vulnerability exceptions are highlighted in the CLI when you run `docker scout
cves <image>`. If a CVE is suppressed by an exception, a `SUPPRESSED` label
appears next to the CVE ID. Details about the exception are also displayed.

The downside with this approach is that you can't change or update the
exception later. Image layers are immutable, so anything you put in the image's
filesystem is there forever. Attaching the document as an
[attestation](#attestation) provides better flexibility.
![SUPPRESSED label in the CLI output](/scout/images/suppressed-cve-cli.png)

> [!NOTE]
> [!IMPORTANT]
> In order to view exceptions in the CLI, you must configure the CLI to use
> the same Docker organization that you used to create the exceptions.
>
> VEX documents embedded in the image filesystem are not considered for images
> that have attestations. If your image has **any** attestations, Docker Scout
> will only look for exceptions in the attestations, and not in the image
> filesystem.
> To configure an organization for the CLI, run:
>
> If you want to use the VEX document embedded in the image filesystem, you
> must remove the attestation from the image. Note that provenance attestations
> may be added automatically for images. To ensure that no attestations are
> added to the image, you can explicitly disable both SBOM and provenance
> attestations using the `--provenance=false` and `--sbom=false` flags when
> building the image.

To embed a VEX document on the image filesystem, `COPY` the file into the image
as part of the image build. The following example shows how to copy all VEX
documents under `.vex/` in the build context, to `/var/lib/db` in the image.
> ```console
> $ docker scout configure organization <organization>
> ```
>
> Replace `<organization>` with the name of your Docker organization.
>
> You can also set the organization on a per-command basis by using the
> `--org` flag:
>
> ```console
> $ docker scout cves --org <organization> <image>
> ```

```dockerfile
# syntax=docker/dockerfile:1
To exclude suppressed CVEs from the output, use the `--ignore-suppressed` flag:

FROM alpine
COPY .vex/* /var/lib/db/
```console
$ docker scout cves --ignore-suppressed <image>
```

The filename of the VEX document must match the `*.vex.json` glob pattern.
It doesn't matter where on the image's filesystem you store the file.

Note that the copied files must be part of the filesystem of the final image,
For multi-stage builds, the documents must persist in the final stage.

## View exceptions

The **Exceptions** page on the [Docker Scout Dashboard](https://scout.docker.com/)
lists the exceptions for all images in your organization. Selecting a row in
the list opens the exception side panel, which displays more information about
the exception and where it comes from.

To view all exceptions for a specific image tag:

{{< tabs >}}
{{< tab name="Docker Scout Dashboard" >}}

1. Go to the [Images page](https://scout.docker.com/reports/images).
2. Select the tag that you want to inspect.
3. Open the **Image attestations** tab.

{{< /tab >}}
{{< tab name="Docker Desktop" >}}

1. Open the **Images** view in Docker Desktop.
2. Open the **Hub** tab.
3. Select the tag you want to inspect.
4. Open the **Image attestations** tab.

{{< /tab >}}
{{< /tabs >}}
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