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Docker content trust documentation
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<!--[metadata]>
+++
title = "Content trust in Docker"
description = "Enabling content trust in Docker"
keywords = ["content, trust, security, docker, documentation"]
[menu.main]
parent= "smn_content_trust"
weight=-1
+++
<![end-metadata]-->
# Content trust in Docker
When transferring data among networked systems, *trust* is a central concern. In
particular, when communicating over an untrusted medium such as the internet, it
is critical to ensure the integrity and publisher of all the data a system
operates on. You use Docker to push and pull images (data) to a registry. Content trust
gives you the ability to both verify the integrity and the publisher of all the
data received from a registry over any channel.
Content trust is currently only available for users of the public Docker Hub. It
is currently not available for the Docker Trusted Registry or for private
registries.
## Understand trust in Docker
Content trust allows operations with a remote Docker registry to enforce
client-side signing and verification of image tags. Content trust provides the
ability to use digital signatures for data sent to and received from remote
Docker registries. These signatures allow client-side verification of the
integrity and publisher of specific image tags.
Currently, content trust is disabled by default. You must enabled it by setting
the `DOCKER_CONTENT_TRUST` environment variable.
Once content trust is enabled, image publishers can sign their images. Image consumers can
ensure that the images they use are signed. publishers and consumers can be
individuals alone or in organizations. Docker's content trust supports users and
automated processes such as builds.
### Image tags and content trust
An individual image record has the following identifier:
```
[REGISTRY_HOST[:REGISTRY_PORT]/]REPOSITORY[:TAG]
```
A particular image `REPOSITORY` can have multiple tags. For example, `latest` and
`3.1.2` are both tags on the `mongo` image. An image publisher can build an image
and tag combination many times changing the image with each build.
Content trust is associated with the `TAG` portion of an image. Each image
repository has a set of keys that image publishers use to sign an image tag.
Image publishers have discretion on which tags they sign.
An image repository can contain an image with one tag that is signed and another
tag that is not. For example, consider [the Mongo image
repository](https://hub.docker.com/r/library/mongo/tags/). The `latest`
tag could be unsigned while the `3.1.6` tag could be signed. It is the
responsibility of the image publisher to decide if an image tag is signed or
not. In this representation, some image tags are signed, others are not:
![Signed tags](../images/tag_signing.png)
Publishers can choose to sign a specific tag or not. As a result, the content of
an unsigned tag and that of a signed tag with the same name may not match. For
example, a publisher can push a tagged image `someimage:latest` and sign it.
Later, the same publisher can push an unsigned `someimage:latest` image. This second
push replaces the last unsigned tag `latest` but does not affect the signed `latest` version.
The ability to choose which tags they can sign, allows publishers to iterate over
the unsigned version of an image before officially signing it.
Image consumers can enable content trust to ensure that images they use were
signed. If a consumer enables content trust, they can only pull, run, or build
with trusted images. Enabling content trust is like wearing a pair of
rose-colored glasses. Consumers "see" only signed images tags and the less
desirable, unsigned image tags are "invisible" to them.
![Trust view](../images/trust_view.png)
To the consumer who does not enabled content trust, nothing about how they
work with Docker images changes. Every image is visible regardless of whether it
is signed or not.
### Content trust operations and keys
When content trust is enabled, `docker` CLI commands that operate on tagged images must
either have content signatures or explicit content hashes. The commands that
operate with content trust are:
* `push`
* `build`
* `create`
* `pull`
* `run`
For example, with content trust enabled a `docker pull someimage:latest` only
succeeds if `someimage:latest` is signed. However, an operation with an explicit
content hash always succeeds as long as the hash exists:
```bash
$ docker pull someimage@sha256:d149ab53f8718e987c3a3024bb8aa0e2caadf6c0328f1d9d850b2a2a67f2819a
```
Trust for an image tag is managed through the use of signing keys. Docker's content
trust makes use four different keys:
| Key | Description |
|---------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| offline key | Root of content trust for a image tag. When content trust is enabled, you create the offline key once. |
| target and snapshot | These two keys are known together as the "tagging" key. When content trust is enabled, you create this key when you add a new image repository. If you have the offline key, you can export the tagging key and allow other publishers to sign the image tags. |
| timestamp | This key applies to a repository. It allows Docker repositories to have freshness security guarantees without requiring periodic content refreshes on the client's side. |
With the exception of the timestamp, all the keys are generated and stored locally
client-side. The timestamp is safely generated and stored in a signing server that
is deployed alongside the Docker registry. All keys are generated in a backend
service that isn't directly exposed to the internet and are encrypted at rest.
The following image depicts the various signing keys and their relationships:
![Content trust components](../images/trust_components.png)
>**WARNING**: Loss of the offline key is **very difficult** to recover from.
>Correcting this loss requires intervention from [Docker
>Support](https://support.docker.com) to reset the repository state. This loss
>also requires **manual intervention** from every consumer that used a signed
>tag from this repository prior to the loss.
You should backup the offline key somewhere safe. Given that it is only required
to create new repositories, it is a good idea to store it offline. Make sure you
read [Manage keys for content trust](/security/trust/trust_key_mng) information
for details on creating, securing, and backing up your keys.
## Survey of typical content trust operations
This section surveys the typical trusted operations users perform with Docker
images.
### Enable content trust
Enable content trust by setting the `DOCKER_CONTENT_TRUST` environment variable.
Enabling per-shell is useful because you can have one shell configured for
trusted operations and another terminal shell for untrusted operations. You can
also add this declaration to your shell profile to have it turned on always by
default.
To enable content trust in a `bash` shell enter the following command:
```bash
export DOCKER_CONTENT_TRUST=1
```
Once set, each of the "tag" operations require key for trusted tag. All of these
commands also support the `--disable-content-trust` flag. This flag allows
publishers to run individual operations on tagged images without content trust on an
as-needed basis.
### Push trusted content
To create signed content for a specific image tag, simply enable content trust and push
a tagged image. If this is the first time you have pushed an image using content trust
on your system, the session looks like this:
```bash
$ docker push docker/trusttest:latest
The push refers to a repository [docker.io/docker/trusttest] (len: 1)
9a61b6b1315e: Image already exists
902b87aaaec9: Image already exists
latest: digest: sha256:d02adacee0ac7a5be140adb94fa1dae64f4e71a68696e7f8e7cbf9db8dd49418 size: 3220
Signing and pushing trust metadata
You are about to create a new offline 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 offline key with id a1d96fb:
Repeat passphrase for new offline key with id a1d96fb:
Enter passphrase for new tagging key with id docker.io/docker/trusttest (3a932f1):
Repeat passphrase for new tagging key with id docker.io/docker/trusttest (3a932f1):
Finished initializing "docker.io/docker/trusttest"
```
When you push your first tagged image with content trust enabled, the `docker` client
recognizes this is your first push and:
- alerts you that it will create a new offline key
- requests a passphrase for the key
- generates an offline key in the `~/.docker/trust` directory
- generates a tagging key for in the `~/.docker/trust` directory
The passphrase you chose for both the offline key and your content key-pair should
be randomly generated and stored in a *password manager*.
It is important to note, if you had left off the `latest` tag, content trust is skipped.
This is true even if content trust is enabled and even if this is your first push.
```bash
$ docker push docker/trusttest
The push refers to a repository [docker.io/docker/trusttest] (len: 1)
9a61b6b1315e: Image successfully pushed
902b87aaaec9: Image successfully pushed
latest: digest: sha256:a9a9c4402604b703bed1c847f6d85faac97686e48c579bd9c3b0fa6694a398fc size: 3220
No tag specified, skipping trust metadata push
```
It is skipped because as the message states, you did not supply an image `TAG`
value. In Docker content trust, signatures are associated with tags.
Once you have an offline key on your system, subsequent images repositories
you create can use that same offline key:
```bash
$ docker push docker.io/docker/seaside:latest
The push refers to a repository [docker.io/docker/seaside] (len: 1)
a9539b34a6ab: Image successfully pushed
b3dbab3810fc: Image successfully pushed
latest: digest: sha256:d2ba1e603661a59940bfad7072eba698b79a8b20ccbb4e3bfb6f9e367ea43939 size: 3346
Signing and pushing trust metadata
Enter key passphrase for offline key with id a1d96fb:
Enter passphrase for new tagging key with id docker.io/docker/seaside (bb045e3):
Repeat passphrase for new tagging key with id docker.io/docker/seaside (bb045e3):
Finished initializing "docker.io/docker/seaside"
```
The new image has its own tagging key and timestamp key. The `latest` tag is signed with both of
these.
### Pull image content
A common way to consume an image is to `pull` it. With content trust enabled, the Docker
client only allows `docker pull` to retrieve signed images.
```
$ docker pull docker/seaside
Using default tag: latest
Pull (1 of 1): docker/trusttest:latest@sha256:d149ab53f871
...
Tagging docker/trusttest@sha256:d149ab53f871 as docker/trusttest:latest
```
The `seaside:latest` image is signed. In the following example, the command does not specify a tag, so the system uses
the `latest` tag by default again and the `docker/cliffs:latest` tag is not signed.
```bash
$ docker pull docker/cliffs
Using default tag: latest
no trust data available
```
Because the tag `docker/cliffs:latest` is not trusted, the `pull` fails.
### Disable content trust for specific operations
A user that wants to disable content trust for a particular operation can use the
`--disable-content-trust` flag. **Warning: this flag disables content trust for
this operation**. With this flag, Docker will ignore content-trust and allow all
operations to be done without verifying any signatures. If we wanted the
previous untrusted build to succeed we could do:
```
$ cat Dockerfile
FROM docker/trusttest:notrust
RUN echo
$ docker build --disable-content-trust -t docker/trusttest:testing .
Sending build context to Docker daemon 42.84 MB
...
Successfully built f21b872447dc
```
The same is true for all the other commands, such as `pull` and `push`:
```
$ docker pull --disable-content-trust docker/trusttest:untrusted
...
$ docker push --disable-content-trust docker/trusttest:untrusted
...
```
## Related information
* [Manage keys for content trust](/security/trust/trust_key_mng)
* [Automation with content trust](/security/trust/trust_automation)
* [Play in a content trust sandbox](/security/trust/trust_sandbox)

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<!--[metadata]>
+++
title = "Use trusted images"
description = "Use trusted images"
keywords = ["trust, security, docker, index"]
[menu.main]
identifier="smn_content_trust"
parent= "mn_docker_hub"
weight=4
+++
<![end-metadata]-->
# Use trusted images
The following topics are available:
* [Content trust in Docker](/security/trust/content_trust)
* [Manage keys for content trust](/security/trust/trust_key_mng)
* [Automation with content trust](/security/trust/trust_automation)
* [Play in a content trust sandbox](/security/trust/trust_sandbox)

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<!--[metadata]>
+++
title = "Automation with content trust"
description = "Automating content push pulls with trust"
keywords = ["trust, security, docker, documentation, automation"]
[menu.main]
parent= "smn_content_trust"
+++
<![end-metadata]-->
# Automation with content trust
Your automation systems that pull or build images can also work with trust. Any automation environment must set `DOCKER_TRUST_ENABLED` either manually or in 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_CONTENT_TRUST_OFFLINE_PASSPHRASE`
- `DOCKER_CONTENT_TRUST_TAGGING_PASSPHRASE`
Docker attempts to use the contents of these environment variables as passphrase
for the keys. For example, an image publisher can export the repository `target`
and `snapshot` passphrases:
```bash
$ export DOCKER_CONTENT_TRUST_OFFLINE_PASSPHRASE="u7pEQcGoebUHm6LHe6"
$ export DOCKER_CONTENT_TRUST_TAGGING_PASSPHRASE="l7pEQcTKJjUHm6Lpe4"
```
Then, when pushing a new tag the Docker client does not request these values but signs automatically:
``bash
$ 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
```
## 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 in a scripted fashion. Consider the simple Dockerfile below.
```Dockerfilea
FROM docker/trusttest:latest
RUN echo
```
The `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:
```bash
$ 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:
```bash
$ docker build -t docker/trusttest:testing .
unable to process Dockerfile: No trust data for notrust
```
## Related information
* [Content trust in Docker](/security/trust/content_trust)
* [Manage keys for content trust](/security/trust/trust_key_mng)
* [Play in a content trust sandbox](/security/trust/trust_sandbox)

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<!--[metadata]>
+++
title = "Manage keys for content trust"
description = "Manage keys for content trust"
keywords = ["trust, security, root, keys, repository"]
[menu.main]
parent= "smn_content_trust"
+++
<![end-metadata]-->
# Manage keys for content trust
Trust for an image tag is managed through the use of keys. Docker's content
trust makes use four different keys:
| Key | Description |
|---------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| offline key | Root of content trust for a image tag. When content trust is enabled, you create the offline key once. |
| target and snapshot | These two keys are known together as the "tagging" key. When content trust is enabled, you create this key when you add a new image repository. If you have the offline key, you can export the tagging key and allow other publishers to sign the image tags. |
| timestamp | This key applies to a repository. It allows Docker repositories to have freshness security guarantees without requiring periodic content refreshes on the client's side. |
With the exception of the timestamp, all the keys are generated and stored locally
client-side. The timestamp is safely generated and stored in a signing server that
is deployed alongside the Docker registry. All keys are generated in a backend
service that isn't directly exposed to the internet and are encrypted at rest.
## Choosing a passphrase
The passphrases you chose for both the offline key and your tagging key should
be randomly generated and stored in a password manager. Having the tagging key
allow users to sign image tags on a repository. Passphrases are used to encrypt
your keys at rest and ensures that a lost laptop or an unintended backup doesn't
put the private key material at risk.
## Back up your keys
All the Docker trust keys are stored encrypted using the passphrase you provide
on creation. Even so, you should still take care of the location where you back them up.
Good practice is to create two encrypted USB keys.
It is very important that you backup your keys to a safe, secure location. Loss
of the tagging key is recoverable; loss of the offline key is not.
The Docker client stores the keys in the `~/.docker/trust/private` directory.
Before backing them up, you should `tar` them into an archive:
```bash
$ tar -zcvf private_keys_backup.tar.gz ~/.docker/trust/private
$ chmod 600 private_keys_backup.tar.gz
```
## Lost keys
If a publisher loses keys it means losing the ability to sign trusted content for
your repositories. If you lose a key, contact [Docker
Support](https://support.docker.com) (support@docker.com) to reset the repository
state.
This loss also requires **manual intervention** from every consumer that pulled
the tagged image prior to the loss. Image consumers would get an error for
content that they already downloaded:
```
could not validate the path to a trusted root: failed to validate data with current trusted certificates
```
To correct this, they need to download a new image tag with that is signed with
the new key.
## Related information
* [Content trust in Docker](/security/trust/content_trust)
* [Automation with content trust](/security/trust/trust_automation)
* [Play in a content trust sandbox](/security/trust/trust_sandbox)

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<!--[metadata]>
+++
title = "Play in a content trust sandbox"
description = "Play in a trust sandbox"
keywords = ["trust, security, root, keys, repository, sandbox"]
[menu.main]
parent= "smn_content_trust"
+++
<![end-metadata]-->
# 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](content_trust.md).
### 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]({{< relref "installation.md" >}}). To install Docker Compose, see the
[detailed instructions here]({{< relref "compose/install" >}}).
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 Docker's own public hub. The sandbox mimics a
production trust environment, and requires these additional components:
| Container | Description |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------|
| nostarysandbox | 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 `nostarysandbox`
you interact with a local registry rather than the public 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 tagging 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.
1. Add an entry for the `notaryserver` to `/etc/hosts`.
$ sudo sh -c 'echo "127.0.0.1 notaryserver" >> /etc/hosts'
2. Add an entry for the `sandboxregistry` to `/etc/hosts`.
$ sudo sh -c 'echo "127.0.0.1 sandboxregistry" >> /etc/hosts'
### Build the notarytest image
1. Create a `notarytest` directory on your system.
$ mkdir notarysandbox
2. Change into your `notarysandbox` directory.
$ cd notarysandbox
3. Create a `notarytest` directory then change into that.
$ mkdir notarytest
$ cd nostarytest
4. Create a filed called `Dockerfile` with your favorite editor.
5. 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"]
6. Save and close the file.
7. Build the testing container.
$ docker build -t nostarysandbox .
Sending build context to Docker daemon 2.048 kB
Step 0 : 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.
1. Change to back to the root of your `notarysandbox` directory.
$ cd notarysandbox
2. Clone the `notary` project.
$ git clone -b trust-sandbox https://github.com/docker/notary.git
3. Clone the `distribution` project.
$ git clone https://github.com/docker/distribution.git
4. 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.
5. Build the server images.
$ docker-compose build
The first time you run this, the build takes some time.
6. 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.
7. Change to the `nostarysandbox/distribution` directory.
8. Build the `sandboxregistry` server.
$ docker build -t sandboxregistry .
9. 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 `nostarysandbox` 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 nostarysandbox
root@0710762bb59a:/#
```
Mounting the `docker.sock` gives the `nostarysandbox` access to the `docker`
deamon 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.
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
no trust data available
You see an error, because this content doesn't exist on the `sandboxregistry` yet.
6. 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 offline key with id 8c69e04:
Repeat passphrase for new offline key with id 8c69e04:
Enter passphrase for new tagging key with id sandboxregistry:5000/test/trusttest (93c362a):
Repeat passphrase for new tagging 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
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@sha256:1d871dcb16805f0604f10d31260e79c22070b35abc71a3d1e7ee54f1042c8c7c
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.
1. Leave the sandbox container running.
2. Open a new bash terminal from your host into the `sandboxregistry`.
$ docker exec -it sandboxregistry bash
296db6068327#
3. 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
4. Add malicious data to one of the trusttest layers:
# echo "Malicious data" > data
5. Got back to your sandbox terminal.
6. 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
7. 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
8. 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>.
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