Merge branch 'document-container-scanning-docker-insecure-var' into 'master'

Document Container Scanning DOCKER_INSECURE var

See merge request gitlab-org/gitlab!25223

doc/user/application_security/container_scanning/index.md

@@ -170,6 +170,7 @@ using environment variables.
 | `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"`                                                                                                       |
+| `DOCKER_INSECURE`              | Allow [Klar](https://github.com/optiopay/klar) to access secure Docker registries using HTTPS with bad (or self-signed) SSL certificates.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | `"false"`                                                                                                       |
 | `CLAIR_VULNERABILITIES_DB_URL` | (**DEPRECATED - use `CLAIR_DB_CONNECTION_STRING` instead**) This variable is explicitly set in the [services section](https://gitlab.com/gitlab-org/gitlab/-/blob/898c5da43504eba87b749625da50098d345b60d6/lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml#L23) 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 standalone Container Scanning Tool](#running-the-standalone-container-scanning-tool) section.                                      | `clair-vulnerabilities-db`                                                                                      |
 | `CLAIR_DB_CONNECTION_STRING`   | This variable represents the [connection string](https://www.postgresql.org/docs/9.3/libpq-connect.html#AEN39692) to the [Postgres server hosting the vulnerabilities definitions](https://hub.docker.com/r/arminc/clair-db) database and **shouldn't be changed** unless you're running the image locally as described in the [Running the standalone Container Scanning Tool](#running-the-standalone-container-scanning-tool) section. The host value for the connection string must match the [alias](https://gitlab.com/gitlab-org/gitlab/-/blob/898c5da43504eba87b749625da50098d345b60d6/lib/gitlab/ci/templates/Security/Container-Scanning.gitlab-ci.yml#L23) value of the `Container-Scanning.gitlab-ci.yml` template file, which defaults to `clair-vulnerabilities-db`. | `postgresql://postgres:password@clair-vulnerabilities-db:5432/postgres?sslmode=disable&statement_timeout=60000` |
 | `CI_APPLICATION_REPOSITORY`    | Docker repository URL for the image to be scanned.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 | `$CI_REGISTRY_IMAGE/$CI_COMMIT_REF_SLUG`                                                                        |
@@ -226,6 +227,10 @@ Container Scanning can be executed on an offline air-gapped GitLab Ultimate inst
        CLAIR_DB_IMAGE: $CI_REGISTRY/namespace/clair-vulnerabilities-db
    ```
 
+1. If your local Docker container registry is running securely over `HTTPS`, but you're using a
+   self-signed certificate, then you must set `DOCKER_INSECURE: true` in the above
+   `container_scanning` section of your `.gitlab-ci.yml`.
+
 It may be worthwhile to set up a [scheduled pipeline](../../project/pipelines/schedules.md) to automatically build a new version of the vulnerabilities database on a preset schedule. You can use the following `.gitlab-yml.ci` as a template:
 
 ```yaml