Automation with content trustEstimated reading time: 2 minutes
Your automation systems that pull or build images can also work with trust. Any automation environment must set
DOCKER_CONTENT_TRUST either manually or in a scripted fashion before processing images.
Bypass requests for passphrases
To allow tools to wrap docker and push trusted content, there are two environment variables that allow you to provide the passphrases without an expect script, or typing them in:
Docker attempts to use the contents of these environment variables as passphrase
for the keys. For example, an image publisher can export the repository
$ export DOCKER_CONTENT_TRUST_ROOT_PASSPHRASE="u7pEQcGoebUHm6LHe6" $ export DOCKER_CONTENT_TRUST_REPOSITORY_PASSPHRASE="l7pEQcTKJjUHm6Lpe4"
Then, when pushing a new tag the Docker client does not request these values but signs automatically:
$ docker push docker/trusttest:latest The push refers to a repository [docker.io/docker/trusttest] (len: 1) a9539b34a6ab: Image already exists b3dbab3810fc: Image already exists latest: digest: sha256:d149ab53f871 size: 3355 Signing and pushing trust metadata
When working directly with the Notary client, it uses its own set of environment variables.
Building with content trust
You can also build with content trust. Before running the
docker build command, you should set the environment variable
DOCKER_CONTENT_TRUST either manually or in a scripted fashion. Consider the simple Dockerfile below.
FROM docker/trusttest:latest RUN echo
FROM tag is pulling a signed image. You cannot build an image that has a
FROM that is not either present locally or signed. Given that content trust
data exists for the tag
latest, the following build should succeed:
$ docker build -t docker/trusttest:testing . Using default tag: latest latest: Pulling from docker/trusttest b3dbab3810fc: Pull complete a9539b34a6ab: Pull complete Digest: sha256:d149ab53f871
If content trust is enabled, building from a Dockerfile that relies on tag without trust data, causes the build command to fail:
$ docker build -t docker/trusttest:testing . unable to process Dockerfile: No trust data for notrust
- Content trust in Docker
- Manage keys for content trust
- Delegations for content trust
- Play in a content trust sandbox