Allow container scanning to run offline

changelogs/unreleased/allow-container-scanning-to-run-offline.yml

+---
+title: Allow container scanning to run offline by specifying the Clair DB image to use.
+merge_request: 19161
+author:
+type: changed

lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml

@@ -9,16 +9,17 @@ container_scanning:
     name: registry.gitlab.com/gitlab-org/security-products/analyzers/klar:$CS_MAJOR_VERSION
     entrypoint: []
   variables:
-    # By default, use the latest clair vulnerabilities database, however, allow it to be overridden here
-    # with a specific version to provide consistency for integration testing purposes
-    CLAIR_DB_IMAGE_TAG: latest
-    # Override this variable in your `.gitlab-ci.yml` file and set it to `fetch` if you want to provide a `clair-whitelist.yaml` file.
-    # See https://docs.gitlab.com/ee/user/application_security/container_scanning/index.html#overriding-the-container-scanning-template
+    # By default, use the latest clair vulnerabilities database, however, allow it to be overridden here with a specific image
+    # to enable container scanning to run offline, or to provide a consistent list of vulnerabilities for integration testing purposes
+    CLAIR_DB_IMAGE_TAG: "latest"
+    CLAIR_DB_IMAGE: "arminc/clair-db:$CLAIR_DB_IMAGE_TAG"
+    # Override the GIT_STRATEGY variable in your `.gitlab-ci.yml` file and set it to `fetch` if you want to provide a `clair-whitelist.yml`
+    # file. See https://docs.gitlab.com/ee/user/application_security/container_scanning/index.html#overriding-the-container-scanning-template
     # for details
     GIT_STRATEGY: none
   allow_failure: true
   services:
-    - name: arminc/clair-db:$CLAIR_DB_IMAGE_TAG
+    - name: $CLAIR_DB_IMAGE
       alias: clair-vulnerabilities-db
   script:
     # the kubernetes executor currently ignores the Docker image entrypoint value, so the start.sh script must