Play in a content 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.

Prerequisites

These instructions assume you are running in Linux or Mac OS X. You can run this sandbox on a local machine or on a virtual machine. You will need to have sudo privileges on your local machine or in the VM.

This sandbox requires you to install two Docker tools: Docker Engine and Docker Compose. To install the Docker Engine, choose from the list of supported platforms. To install Docker Compose, see the detailed instructions here.

Finally, you'll need to have git installed on your local system or VM.

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 requires these additional components:

Container	Description
notarysandbox	A container with the latest version of Docker Engine and with some preconfigured certifications. 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
Notary signer	A service that ensures that your keys are secure.
MySQL	The database where all of the trust information will be stored

The sandbox uses the Docker daemon on your local system. Within the notarysandbox you interact with a 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'll also create root and repository keys. The sandbox is configured to store all the keys and files inside the notarysandbox container. Since the keys you create in the sandbox are for play only, destroying the container destroys them as well.

Build the sandbox

In this section, you build the Docker components for your trust sandbox. If you work exclusively with the Docker Hub, you would not need with these components. They are built into the Docker Hub for you. For the sandbox, however, you must build your own entire, mock production environment and registry.

Configure /etc/hosts

The sandbox' notaryserver and sandboxregistry run on your local server. The client inside the notarysandbox container connects to them over your network. So, you'll need an entry for both the servers in your local /etc/hosts file.

Add an entry for the notaryserver to /etc/hosts.

$ sudo sh -c 'echo "127.0.0.1 notaryserver" >> /etc/hosts'

Add an entry for the sandboxregistry to /etc/hosts.

$ sudo sh -c 'echo "127.0.0.1 sandboxregistry" >> /etc/hosts'

Build the notarytest image

Create a notarytest directory on your system.
```
$ mkdir notarysandbox
```
Change into your notarysandbox directory.
```
$ cd notarysandbox
```
Create a notarytest directory then change into that.
```
$ mkdir notarytest
$ cd notarytest
```
Create a filed called Dockerfile with your favorite editor.

Add the following to the new file.

FROM debian:jessie

ADD https://master.dockerproject.org/linux/amd64/docker /usr/bin/docker
RUN chmod +x /usr/bin/docker \
  && apt-get update \
  && apt-get install -y \
  tree \
  vim \
  git \
  ca-certificates \
  --no-install-recommends

WORKDIR /root
RUN git clone -b trust-sandbox https://github.com/docker/notary.git
RUN cp /root/notary/fixtures/root-ca.crt /usr/local/share/ca-certificates/root-ca.crt
RUN update-ca-certificates

ENTRYPOINT ["bash"]

Save and close the file.

Build the testing container.

$ docker build -t notarysandbox .
Sending build context to Docker daemon 2.048 kB
Step 1 : FROM debian:jessie
 ...
 Successfully built 5683f17e9d72

Build and start up the trust servers

In this step, you get the source code for your notary and registry services. Then, you'll use Docker Compose to build and start them on your local system.

Change to back to the root of your notarysandbox directory.
```
$ cd notarysandbox
```

Clone the notary project.

  $ git clone -b trust-sandbox https://github.com/docker/notary.git

Clone the distribution project.

$ git clone https://github.com/docker/distribution.git

Change to the notary project directory.
```
$ cd notary
```

The directory contains a docker-compose file that you'll use to run a notary server together with a notary signer and the corresponding MySQL databases. The databases store the trust information for an image.

Build the server images.
```
$  docker-compose build
```
The first time you run this, the build takes some time.
Run the server containers on your local system.
```
$ docker-compose up -d
```
Once the trust services are up, you'll setup a local version of the Docker Registry v2.
Change to the notarysandbox/distribution directory.
Build the sandboxregistry server.
```
$ docker build -t sandboxregistry .
```

Start the sandboxregistry server running.

$ docker run -p 5000:5000 --name sandboxregistry sandboxregistry &

Playing in the sandbox

Now that everything is setup, you can go into your notarysandbox container and start testing Docker content trust.

Start the notarysandbox container

In this procedure, you start the notarysandbox and link it to the running notary_notaryserver_1 and sandboxregistry containers. The links allow communication among the containers.

$ docker run -it -v /var/run/docker.sock:/var/run/docker.sock --link notary_notaryserver_1:notaryserver --link sandboxregistry:sandboxregistry notarysandbox
root@0710762bb59a:/#

Mounting the docker.sock gives the notarysandbox access to the docker daemon on your host, while storing all the keys and files inside the sandbox container. When you destroy the container, you destroy the "play" keys.

Test some trust operations

Now, you'll pull some images.

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

Tag it to be pushed to our sandbox registry:

# docker tag docker/trusttest sandboxregistry:5000/test/trusttest:latest

Enable content trust.
```
# export DOCKER_CONTENT_TRUST=1
```
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.

Pull the test image.

# docker pull sandboxregistry:5000/test/trusttest
Using default tag: latest
no trust data available

You see an error, because this content doesn't exist on the sandboxregistry yet.

Push the trusted image.

# docker push sandboxregistry:5000/test/trusttest:latest
The push refers to a repository [sandboxregistry:5000/test/trusttest] (len: 1)
a9539b34a6ab: Image successfully pushed
b3dbab3810fc: Image successfully pushed
latest: digest: sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c size: 3348
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 8c69e04:
Repeat passphrase for new root key with id 8c69e04:
Enter passphrase for new repository key with id sandboxregistry:5000/test/trusttest (93c362a):
Repeat passphrase for new repository key with id sandboxregistry:5000/test/trusttest (93c362a):
Finished initializing "sandboxregistry:5000/test/trusttest"
latest: digest: sha256:d149ab53f8718e987c3a3024bb8aa0e2caadf6c0328f1d9d850b2a2a67f2819a size: 3355
Signing and pushing trust metadata

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@sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c
sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c: Pulling from test/trusttest
b3dbab3810fc: Already exists
a9539b34a6ab: Already exists
Digest: sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c
Status: Downloaded newer image for sandboxregistry:5000/test/trusttest@sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c
Tagging sandboxregistry:5000/test/trusttest@sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c 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.

Leave the sandbox container running.
Open a new bash terminal from your host into the sandboxregistry.
```
$ docker exec -it sandboxregistry bash
296db6068327#
```

Change into the registry storage.

You'll need to provide the sha you received when you pushed the image.

# cd /var/lib/registry/docker/registry/v2/blobs/sha256/aa/aac0c133338db2b18ff054943cee3267fe50c75cdee969aed88b1992539ed042

Add malicious data to one of the trusttest layers:
```
# echo "Malicious data" > data
```
Got back to your sandbox terminal.

List the trusttest image.

# docker images | grep trusttest
docker/trusttest                 latest              a9539b34a6ab        7 weeks ago         5.025 MB
sandboxregistry:5000/test/trusttest   latest              a9539b34a6ab        7 weeks ago         5.025 MB
sandboxregistry:5000/test/trusttest   <none>              a9539b34a6ab        7 weeks ago         5.025 MB

Remove the trusttest:latest image.

# docker rmi -f a9539b34a6ab
Untagged: docker/trusttest:latest
Untagged: sandboxregistry:5000/test/trusttest:latest
Untagged: sandboxregistry:5000/test/trusttest@sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c
Deleted: a9539b34a6aba01d3942605dfe09ab821cd66abf3cf07755b0681f25ad81f675
Deleted: b3dbab3810fc299c21f0894d39a7952b363f14520c2f3d13443c669b63b6aa20

Pull the image again.

# docker pull sandboxregistry:5000/test/trusttest
Using default tag: latest
...
b3dbab3810fc: Verifying Checksum
a9539b34a6ab: Pulling fs layer
filesystem layer verification failed for digest sha256:aac0c133338db2b18ff054943cee3267fe50c75cdee969aed88b1992539ed042

You'll see the the pull did not complete because the trust system was unable to verify the image.

More play in the sandbox

Now, that 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.