Merge branch 'document-container-scanning-options' into 'master'

Document available container scanning options

Closes #10123

See merge request gitlab-org/gitlab!17964

doc/user/application_security/container_scanning/index.md

@@ -87,7 +87,7 @@ The results will be saved as a
 that you can later download and analyze.
 Due to implementation limitations, we always take the latest Container Scanning
 artifact available. Behind the scenes, the
-[GitLab Container Scanning analyzer](https://gitlab.com/gitlab-org/security-products/container-scanning)
+[GitLab Klar analyzer](https://gitlab.com/gitlab-org/security-products/analyzers/klar/)
 is used and runs the scans.
 
 ## Example
@@ -145,6 +145,23 @@ container_scanning:
     GIT_STRATEGY: fetch
 ```
 
+### Available variables
+
+Container Scanning can be [configured](#overriding-the-container-scanning-template)
+using environment variables.
+
+| Environment Variable           | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   | Default                                  |
+| ------                         | ------                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | ------                                   |
+| `KLAR_TRACE`                   | Set to true to enable more verbose output from klar.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | `"false"`                                |
+| `DOCKER_USER`                  | Username for accessing a Docker registry requiring authentication.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            | `$CI_REGISTRY_USER`                      |
+| `DOCKER_PASSWORD`              | Password for accessing a Docker registry requiring authentication.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            | `$CI_REGISTRY_PASSWORD`                  |
+| `CLAIR_OUTPUT`                 | Severity level threshold. Vulnerabilities with severity level higher than or equal to this threshold will be outputted. Supported levels are `Unknown`, `Negligible`, `Low`, `Medium`, `High`, `Critical` and `Defcon1`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | `Unknown`                                |
+| `REGISTRY_INSECURE`            | Allow [Klar](https://github.com/optiopay/klar) to access insecure registries (HTTP only). Should only be set to `true` when testing the image locally.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | `"false"`                                |
+| `CLAIR_VULNERABILITIES_DB_URL` | This variable is explicitly set in the [services section](https://gitlab.com/gitlab-org/gitlab/blob/30522ca8b901223ac8c32b633d8d67f340b159c1/lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml#L17-19) of the `Container-Scanning.gitlab-ci.yml` file and defaults to `clair-vulnerabilities-db`.  This value represents the address that the [postgres server hosting the vulnerabilities definitions](https://hub.docker.com/r/arminc/clair-db) is running on and **shouldn't be changed** unless you're running the image locally as described in the [Running the scanning tool](https://gitlab.com/gitlab-org/security-products/analyzers/klar/#running-the-scanning-tool) section of the [klar readme](https://gitlab.com/gitlab-org/security-products/analyzers/klar). | `clair-vulnerabilities-db`               |
+| `CI_APPLICATION_REPOSITORY`    | Docker repository URL for the image to be scanned.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            | `$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG` |
+| `CI_APPLICATION_TAG`           | Docker respository tag for the image to be scanned.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           | `$CI_COMMIT_SHA`                         |
+| `CLAIR_DB_IMAGE_TAG`           | The Docker image tag for the [postgres server hosting the vulnerabilities definitions](https://hub.docker.com/r/arminc/clair-db). It can be useful to override this value with a specific version, for example, to provide a consistent set of vulnerabilities for integration testing purposes.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              | `latest`                                 |
+
 ## Security Dashboard
 
 The Security Dashboard is a good place to get an overview of all the security