210 lines
11 KiB
Markdown
210 lines
11 KiB
Markdown
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## TL,DR
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A caching proxy for Docker; allows centralised management of (multiple) registries and their authentication; caches images from *any* registry.
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## What?
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Essentially, it's a [man in the middle](https://en.wikipedia.org/wiki/Man-in-the-middle_attack): an intercepting proxy based on `nginx`, to which all docker traffic is directed using the `HTTPS_PROXY` mechanism and injected CA root certificates.
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The main feature is Docker layer/image caching, including layers served from S3, Google Storage, etc.
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As a bonus it allows for centralized management of Docker registry credentials, which can in itself be the main feature, eg in Kubernetes environments.
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You configure the Docker clients (_err... Kubernetes Nodes?_) once, and then all configuration is done on the proxy --
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for this to work it requires inserting a root CA certificate into system trusted root certs.
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## master/:latest is unstable/beta
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- `:latest` and `:latest-debug` Docker tag is unstable, built from master, and amd64-only
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- Production/stable is `0.4.2`, see [0.4.2 tag on Github](https://github.com/rpardini/docker-registry-proxy/tree/0.4.2) - this image is multi-arch amd64/arm64
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- The previous version is `0.3.0`, see [0.3.0 tag on Github](https://github.com/rpardini/docker-registry-proxy/tree/0.3.0) (amd64 only)
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## Usage
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- Run the proxy on a host close (network-wise: high bandwidth, same-VPC, etc) to the Docker clients
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- Expose port 3128 to the network
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- Map volume `/docker_mirror_cache` for up to `CACHE_MAX_SIZE` (32gb by default) of cached images across all cached registries
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- Map volume `/ca`, the proxy will store the CA certificate here across restarts. **Important** this is security sensitive.
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- Env `CACHE_MAX_SIZE` (default `32g`): set the max size to be used for caching local Docker image layers. Use [Nginx sizes](http://nginx.org/en/docs/syntax.html).
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- Env `REGISTRIES`: space separated list of registries to cache; no need to include DockerHub, its already done internally.
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- Env `AUTH_REGISTRIES`: space separated list of `hostname:username:password` authentication info.
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- `hostname`s listed here should be listed in the REGISTRIES environment as well, so they can be intercepted.
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- Env `AUTH_REGISTRIES_DELIMITER` to change the separator between authentication info. By default, a space: "` `". If you use keys that contain spaces (as with Google Cloud Registry), you should update this variable, e.g. setting it to `AUTH_REGISTRIES_DELIMITER=";;;"`. In that case, `AUTH_REGISTRIES` could contain something like `registry1.com:user1:pass1;;;registry2.com:user2:pass2`.
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- Env `AUTH_REGISTRY_DELIMITER` to change the separator between authentication info *parts*. By default, a colon: "`:`". If you use keys that contain single colons, you should update this variable, e.g. setting it to `AUTH_REGISTRIES_DELIMITER=":::"`. In that case, `AUTH_REGISTRIES` could contain something like `registry1.com:::user1:::pass1 registry2.com:::user2:::pass2`.
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### Simple (no auth, all cache)
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```bash
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docker run --rm --name docker_registry_proxy -it \
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-p 0.0.0.0:3128:3128 \
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-v $(pwd)/docker_mirror_cache:/docker_mirror_cache \
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-v $(pwd)/docker_mirror_certs:/ca \
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rpardini/docker-registry-proxy:0.4.2
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```
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### DockerHub auth
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For Docker Hub authentication:
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- `hostname` should be `auth.docker.io`
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- `username` should NOT be an email, use the regular username
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```bash
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docker run --rm --name docker_registry_proxy -it \
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-p 0.0.0.0:3128:3128 \
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-v $(pwd)/docker_mirror_cache:/docker_mirror_cache \
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-v $(pwd)/docker_mirror_certs:/ca \
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-e REGISTRIES="k8s.gcr.io gcr.io quay.io your.own.registry another.public.registry" \
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-e AUTH_REGISTRIES="auth.docker.io:dockerhub_username:dockerhub_password your.own.registry:username:password" \
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rpardini/docker-registry-proxy:0.4.2
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```
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### Simple registries auth (HTTP Basic auth)
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For regular registry auth (HTTP Basic), the `hostname` should be the registry itself... unless your registry uses a different auth server.
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See the example above for DockerHub, adapt the `your.own.registry` parts (in both ENVs).
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This should work for quay.io also, but I have no way to test.
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### GitLab auth
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GitLab may use a different/separate domain to handle the authentication procedure.
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Just like DockerHub uses `auth.docker.io`, GitLab uses its primary (git) domain for the authentication.
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If you run GitLab on `git.example.com` and its registry on `reg.example.com`, you need to include both in `REGISTRIES` and use the primary domain for `AUTH_REGISTRIES`.
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For GitLab.com itself the authentication domain should be `gitlab.com`.
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```bash
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docker run --rm --name docker_registry_proxy -it \
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-p 0.0.0.0:3128:3128 \
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-v $(pwd)/docker_mirror_cache:/docker_mirror_cache \
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-v $(pwd)/docker_mirror_certs:/ca \
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-e REGISTRIES="reg.example.com git.example.com" \
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-e AUTH_REGISTRIES="git.example.com:USER:PASSWORD" \
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rpardini/docker-registry-proxy:0.4.2
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```
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### Google Container Registry (GCR) auth
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For Google Container Registry (GCR), username should be `_json_key` and the password should be the contents of the service account JSON.
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Check out [GCR docs](https://cloud.google.com/container-registry/docs/advanced-authentication#json_key_file).
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The service account key is in JSON format, it contains spaces ("` `") and colons ("`:`").
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To be able to use GCR you should set `AUTH_REGISTRIES_DELIMITER` to something different than space (e.g. `AUTH_REGISTRIES_DELIMITER=";;;"`) and `AUTH_REGISTRY_DELIMITER` to something different than a single colon (e.g. `AUTH_REGISTRY_DELIMITER=":::"`).
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Example with GCR using credentials from a service account from a key file `servicekey.json`:
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```bash
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docker run --rm --name docker_registry_proxy -it \
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-p 0.0.0.0:3128:3128 \
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-v $(pwd)/docker_mirror_cache:/docker_mirror_cache \
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-v $(pwd)/docker_mirror_certs:/ca \
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-e REGISTRIES="k8s.gcr.io gcr.io quay.io your.own.registry another.public.registry" \
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-e AUTH_REGISTRIES_DELIMITER=";;;" \
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-e AUTH_REGISTRY_DELIMITER=":::" \
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-e AUTH_REGISTRIES="gcr.io:::_json_key:::$(cat servicekey.json);;;auth.docker.io:::dockerhub_username:::dockerhub_password" \
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rpardini/docker-registry-proxy:0.4.2
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```
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## Configuring the Docker clients / Kubernetes nodes
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Let's say you setup the proxy on host `192.168.66.72`, you can then `curl http://192.168.66.72:3128/ca.crt` and get the proxy CA certificate.
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On each Docker host that is to use the cache:
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- [Configure Docker proxy](https://docs.docker.com/config/daemon/systemd/#httphttps-proxy) pointing to the caching server
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- Add the caching server CA certificate to the list of system trusted roots.
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- Restart `dockerd`
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Do it all at once, tested on Ubuntu Xenial, Bionic, and Focal, all systemd based:
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```bash
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# Add environment vars pointing Docker to use the proxy
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mkdir -p /etc/systemd/system/docker.service.d
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cat << EOD > /etc/systemd/system/docker.service.d/http-proxy.conf
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[Service]
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Environment="HTTP_PROXY=http://192.168.66.72:3128/"
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Environment="HTTPS_PROXY=http://192.168.66.72:3128/"
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EOD
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# Get the CA certificate from the proxy and make it a trusted root.
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curl http://192.168.66.72:3128/ca.crt > /usr/share/ca-certificates/docker_registry_proxy.crt
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echo "docker_registry_proxy.crt" >> /etc/ca-certificates.conf
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update-ca-certificates --fresh
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# Reload systemd
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systemctl daemon-reload
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# Restart dockerd
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systemctl restart docker.service
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```
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## Testing
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Clear `dockerd` of everything not currently running: `docker system prune -a -f` *beware*
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Then do, for example, `docker pull k8s.gcr.io/kube-proxy-amd64:v1.10.4` and watch the logs on the caching proxy, it should list a lot of MISSes.
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Then, clean again, and pull again. You should see HITs! Success.
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Do the same for `docker pull ubuntu` and rejoice.
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Test your own registry caching and authentication the same way; you don't need `docker login`, or `.docker/config.json` anymore.
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## Developing/Debugging
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Since `0.4` there is a separate `-debug` version of the image, which includes `nginx-debug`, and (since 0.5.x) has a `mitmproxy` (actually `mitmweb`) inserted after the CONNECT proxy but before the caching logic, and a second `mitmweb` between the caching layer and DockerHub.
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This allows very in-depth debugging. Use sparingly, and definitely not in production.
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```bash
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docker run --rm --name docker_registry_proxy -it
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-e DEBUG_NGINX=true -e DEBUG=true -e DEBUG_HUB=true -p 0.0.0.0:8081:8081 -p 0.0.0.0:8082:8082 \
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-p 0.0.0.0:3128:3128 \
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-v $(pwd)/docker_mirror_cache:/docker_mirror_cache \
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-v $(pwd)/docker_mirror_certs:/ca \
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rpardini/docker-registry-proxy:0.4.2-debug
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```
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- `DEBUG=true` enables the mitmweb proxy between Docker clients and the caching layer, accessible on port 8081
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- `DEBUG_HUB=true` enables the mitmweb proxy between the caching layer and DockerHub, accessible on port 8082 (since 0.5.x)
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- `DEBUG_NGINX=true` enables nginx-debug and debug logging, which probably is too much. Seriously.
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## Gotchas
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- If you authenticate to a private registry and pull through the proxy, those images will be served to any client that can reach the proxy, even without authentication. *beware*
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- Repeat, **this will make your private images very public if you're not careful**.
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- **Currently you cannot push images while using the proxy** which is a shame. PRs welcome.
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- Setting this on Linux is relatively easy.
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- On Mac and Windows the CA-certificate part will be very different but should work in principle.
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- Please send PRs with instructions for Windows and Mac if you succeed!
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### Why not use Docker's own registry, which has a mirror feature?
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Yes, Docker offers [Registry as a pull through cache](https://docs.docker.com/registry/recipes/mirror/), *unfortunately*
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it only covers the DockerHub case. It won't cache images from `quay.io`, `k8s.gcr.io`, `gcr.io`, or any such, including any private registries.
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That means that your shiny new Kubernetes cluster is now a bandwidth hog, since every image will be pulled from the
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Internet on every Node it runs on, with no reuse.
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This is due to the way the Docker "client" implements `--registry-mirror`, it only ever contacts mirrors for images
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with no repository reference (eg, from DockerHub).
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When a repository is specified `dockerd` goes directly there, via HTTPS (and also via HTTP if included in a
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`--insecure-registry` list), thus completely ignoring the configured mirror.
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### Docker itself should provide this.
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Yeah. Docker Inc should do it. So should NPM, Inc. Wonder why they don't. 😼
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### TODO:
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- [ ] Test and make auth work with quay.io, unfortunately I don't have access to it (_hint, hint, quay_)
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- [x] Hide the mitmproxy building code under a Docker build ARG.
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- [ ] "Developer Office" proxy scenario, where many developers on a fast LAN share a proxy for bandwidth and speed savings (already works for pulls, but messes up pushes, which developers tend to use a lot)
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