---
description: Play in a trust sandbox
keywords: trust, security, root, keys, repository, sandbox
title: Play in a content trust sandbox
aliases:
- /security/trust/trust_sandbox/
---
This page explains how to set up and use a sandbox for experimenting with trust.
The sandbox allows you to configure and try trust operations locally without
impacting your production images.
Before working through this sandbox, you should have read through the
[trust overview](index.md).
## Prerequisites
These instructions assume you are running in Linux or macOS. You can run
this sandbox on a local machine or on a virtual machine. You need to
have privileges to run docker commands on your local machine or in the VM.
This sandbox requires you to install two Docker tools: Docker Engine >= 1.10.0
and Docker Compose >= 1.6.0. To install the Docker Engine, choose from the
[list of supported platforms](../../install/index.md). To install
Docker Compose, see the
[detailed instructions here](../../../compose/install/index.md).
## What is in the sandbox?
If you are just using trust out-of-the-box you only need your Docker Engine
client and access to the Docker Hub. The sandbox mimics a
production trust environment, and sets up these additional components.
| Container | Description |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------|
| trustsandbox | A container with the latest version of Docker Engine and with some preconfigured certificates. This is your sandbox where you can use the `docker` client to test trust operations. |
| Registry server | A local registry service. |
| Notary server | The service that does all the heavy-lifting of managing trust |
This means you run your own content trust (Notary) server and registry.
If you work exclusively with the Docker Hub, you would not need these components.
They are built into the Docker Hub for you. For the sandbox, however, you build
your own entire, mock production environment.
Within the `trustsandbox` container, you interact with your local registry rather
than the Docker Hub. This means your everyday image repositories are not used.
They are protected while you play.
When you play in the sandbox, you also create root and repository keys. The
sandbox is configured to store all the keys and files inside the `trustsandbox`
container. Since the keys you create in the sandbox are for play only,
destroying the container destroys them as well.
By using a docker-in-docker image for the `trustsandbox` container, you also
don't pollute your real Docker daemon cache with any images you push and pull.
The images are stored in an anonymous volume attached to this container,
and can be destroyed after you destroy the container.
## Build the sandbox
In this section, you use Docker Compose to specify how to set up and link together
the `trustsandbox` container, the Notary server, and the Registry server.
1. Create a new `trustsandbox` directory and change into it.
$ mkdir trustsandbox
$ cd trustsandbox
2. Create a file called `compose.yml` with your favorite editor. For example, using vim:
$ touch compose.yml
$ vim compose.yml
3. Add the following to the new file.
version: "2"
services:
notaryserver:
image: dockersecurity/notary_autobuilds:server-v0.5.1
volumes:
- notarycerts:/var/lib/notary/fixtures
networks:
- sandbox
environment:
- NOTARY_SERVER_STORAGE_TYPE=memory
- NOTARY_SERVER_TRUST_SERVICE_TYPE=local
sandboxregistry:
image: registry:2.4.1
networks:
- sandbox
container_name: sandboxregistry
trustsandbox:
image: docker:dind
networks:
- sandbox
volumes:
- notarycerts:/notarycerts
privileged: true
container_name: trustsandbox
entrypoint: ""
command: |-
sh -c '
cp /notarycerts/root-ca.crt /usr/local/share/ca-certificates/root-ca.crt &&
update-ca-certificates &&
dockerd-entrypoint.sh --insecure-registry sandboxregistry:5000'
volumes:
notarycerts:
external: false
networks:
sandbox:
external: false
4. Save and close the file.
5. Run the containers on your local system.
$ docker compose up -d
The first time you run this, the docker-in-docker, Notary server, and registry
images are downloaded from Docker Hub.
## Play in the sandbox
Now that everything is setup, you can go into your `trustsandbox` container and
start testing Docker content trust. From your host machine, obtain a shell
in the `trustsandbox` container.
$ docker container exec -it trustsandbox sh
/ #
### Test some trust operations
Now, pull some images from within the `trustsandbox` container.
1. Download a `docker` image to test with.
/ # docker pull docker/trusttest
docker pull docker/trusttest
Using default tag: latest
latest: Pulling from docker/trusttest
b3dbab3810fc: Pull complete
a9539b34a6ab: Pull complete
Digest: sha256:d149ab53f8718e987c3a3024bb8aa0e2caadf6c0328f1d9d850b2a2a67f2819a
Status: Downloaded newer image for docker/trusttest:latest
2. Tag it to be pushed to our sandbox registry:
/ # docker tag docker/trusttest sandboxregistry:5000/test/trusttest:latest
3. Enable content trust.
/ # export DOCKER_CONTENT_TRUST=1
4. Identify the trust server.
/ # export DOCKER_CONTENT_TRUST_SERVER=https://notaryserver:4443
This step is only necessary because the sandbox is using its own server.
Normally, if you are using the Docker Public Hub this step isn't necessary.
5. Pull the test image.
/ # docker pull sandboxregistry:5000/test/trusttest
Using default tag: latest
Error: remote trust data does not exist for sandboxregistry:5000/test/trusttest: notaryserver:4443 does not have trust data for sandboxregistry:5000/test/trusttest
You see an error, because this content doesn't exist on the `notaryserver` yet.
6. Push and sign the trusted image.
/ # docker push sandboxregistry:5000/test/trusttest:latest
The push refers to a repository [sandboxregistry:5000/test/trusttest]
5f70bf18a086: Pushed
c22f7bc058a9: Pushed
latest: digest: sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926 size: 734
Signing and pushing trust metadata
You are about to create a new root signing key passphrase. This passphrase
will be used to protect the most sensitive key in your signing system. Please
choose a long, complex passphrase and be careful to keep the password and the
key file itself secure and backed up. It is highly recommended that you use a
password manager to generate the passphrase and keep it safe. There will be no
way to recover this key. You can find the key in your config directory.
Enter passphrase for new root key with ID 27ec255:
Repeat passphrase for new root key with ID 27ec255:
Enter passphrase for new repository key with ID 58233f9 (sandboxregistry:5000/test/trusttest):
Repeat passphrase for new repository key with ID 58233f9 (sandboxregistry:5000/test/trusttest):
Finished initializing "sandboxregistry:5000/test/trusttest"
Successfully signed "sandboxregistry:5000/test/trusttest":latest
Because you are pushing this repository for the first time, Docker creates
new root and repository keys and asks you for passphrases with which to
encrypt them. If you push again after this, it only asks you for repository
passphrase so it can decrypt the key and sign again.
7. Try pulling the image you just pushed:
/ # docker pull sandboxregistry:5000/test/trusttest
Using default tag: latest
Pull (1 of 1): sandboxregistry:5000/test/trusttest:latest@sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926
sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926: Pulling from test/trusttest
Digest: sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926
Status: Downloaded newer image for sandboxregistry:5000/test/trusttest@sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926
Tagging sandboxregistry:5000/test/trusttest@sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926 as sandboxregistry:5000/test/trusttest:latest
### Test with malicious images
What happens when data is corrupted and you try to pull it when trust is
enabled? In this section, you go into the `sandboxregistry` and tamper with some
data. Then, you try and pull it.
1. Leave the `trustsandbox` shell and container running.
2. Open a new interactive terminal from your host, and obtain a shell into the
`sandboxregistry` container.
$ docker container exec -it sandboxregistry bash
root@65084fc6f047:/#
3. List the layers for the `test/trusttest` image you pushed:
```console
root@65084fc6f047:/# ls -l /var/lib/registry/docker/registry/v2/repositories/test/trusttest/_layers/sha256
total 12
drwxr-xr-x 2 root root 4096 Jun 10 17:26 a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
drwxr-xr-x 2 root root 4096 Jun 10 17:26 aac0c133338db2b18ff054943cee3267fe50c75cdee969aed88b1992539ed042
drwxr-xr-x 2 root root 4096 Jun 10 17:26 cc7629d1331a7362b5e5126beb5bf15ca0bf67eb41eab994c719a45de53255cd
```
4. Change into the registry storage for one of those layers (this is in a different directory):
root@65084fc6f047:/# cd /var/lib/registry/docker/registry/v2/blobs/sha256/aa/aac0c133338db2b18ff054943cee3267fe50c75cdee969aed88b1992539ed042
5. Add malicious data to one of the `trusttest` layers:
root@65084fc6f047:/# echo "Malicious data" > data
6. Go back to your `trustsandbox` terminal.
7. List the `trusttest` image.
/ # docker image ls | grep trusttest
REPOSITORY TAG IMAGE ID CREATED SIZE
docker/trusttest latest cc7629d1331a 11 months ago 5.025 MB
sandboxregistry:5000/test/trusttest latest cc7629d1331a 11 months ago 5.025 MB
sandboxregistry:5000/test/trusttest <none> cc7629d1331a 11 months ago 5.025 MB
8. Remove the `trusttest:latest` image from our local cache.
/ # docker image rm -f cc7629d1331a
Untagged: docker/trusttest:latest
Untagged: sandboxregistry:5000/test/trusttest:latest
Untagged: sandboxregistry:5000/test/trusttest@sha256:ebf59c538accdf160ef435f1a19938ab8c0d6bd96aef8d4ddd1b379edf15a926
Deleted: sha256:cc7629d1331a7362b5e5126beb5bf15ca0bf67eb41eab994c719a45de53255cd
Deleted: sha256:2a1f6535dc6816ffadcdbe20590045e6cbf048d63fd4cc753a684c9bc01abeea
Deleted: sha256:c22f7bc058a9a8ffeb32989b5d3338787e73855bf224af7aa162823da015d44c
Docker does not re-download images that it already has cached, but we want
Docker to attempt to download the tampered image from the registry and reject
it because it is invalid.
9. Pull the image again. This downloads the image from the registry, because we don't have it cached.
/ # docker pull sandboxregistry:5000/test/trusttest
Using default tag: latest
Pull (1 of 1): sandboxregistry:5000/test/trusttest:latest@sha256:35d5bc26fd358da8320c137784fe590d8fcf9417263ef261653e8e1c7f15672e
sha256:35d5bc26fd358da8320c137784fe590d8fcf9417263ef261653e8e1c7f15672e: Pulling from test/trusttest
aac0c133338d: Retrying in 5 seconds
a3ed95caeb02: Download complete
error pulling image configuration: unexpected EOF
The pull did not complete because the trust system couldn't verify the
image.
## More play in the sandbox
Now, you have a full Docker content trust sandbox on your local system,
feel free to play with it and see how it behaves. If you find any security
issues with Docker, feel free to send us an email at <security@docker.com>.
## Clean up your sandbox
When you are done, and want to clean up all the services you've started and any
anonymous volumes that have been created, just run the following command in the
directory where you've created your Docker Compose file:
$ docker compose down -v