Boulder - An ACME CA

This is an implementation of an ACME-based CA. The ACME protocol allows the CA to automatically verify that an applicant for a certificate actually controls an identifier, and allows domain holders to issue and revoke certificates for their domains.

Development Setup

Boulder has a Dockerfile to make it easy to install and set up all its dependencies. This is how the maintainers work on Boulder, and is our main recommended way to run it.

Make sure you have a local copy of Boulder in your $GOPATH, and that you are in that directory:

export GOPATH=~/gopath
git clone https://github.com/letsencrypt/boulder/ $GOPATH/src/github.com/letsencrypt/boulder
cd $GOPATH/src/github.com/letsencrypt/boulder

Additionally, make sure you have Docker Engine 1.13.0+ and Docker Compose 1.10.0+ installed. If you do not, you can follow Docker's installation instructions.

We recommend having at least 2GB of RAM available on your Docker host. In practice using less RAM may result in the MariaDB container failing in non-obvious ways.

By default Boulder is configured to track the production Let's Encrypt environment. To run Boulder with new features enabled to track the staging environment (and to test ACME v2 support), edit docker-compose.yml to change BOULDER_CONFIG_DIR to test/config-next.

To start Boulder in a Docker container, run:

docker-compose up

To run tests:

docker-compose run --use-aliases boulder ./test.sh

To run a specific unittest:

docker-compose run --use-aliases boulder go test ./ra

The configuration in docker-compose.yml mounts your $GOPATH on top of its own $GOPATH. So you can edit code on your host and it will be immediately reflected inside Docker images run with docker-compose.

If docker-compose fails with an error message like "Cannot start service boulder: oci runtime error: no such file or directory" or "Cannot create container for service boulder" you should double check that your $GOPATH exists and doesn't contain any characters other than letters, numbers, - and _.

If you have problems with Docker, you may want to try removing all containers and volumes.

By default, Boulder uses a fake DNS resolver that resolves all hostnames to 127.0.0.1. This is suitable for running integration tests inside the Docker container. If you want Boulder to be able to communicate with a client running on your host instead, you should find your host's Docker IP with:

ifconfig docker0 | grep "inet addr:" | cut -d: -f2 | awk '{ print $1}'

And edit docker-compose.yml to change the FAKE_DNS environment variable to match.

Alternatively, you can override the docker-compose.yml default with an environmental variable using -e (replace 172.17.0.1 with the host IPv4 address found in the command above)

docker-compose run --use-aliases -e FAKE_DNS=172.17.0.1 --service-ports boulder ./start.py

Boulder's default VA configuration (test/config/va.json) is configured to connect to port 5002 to validate HTTP-01 challenges and port 5001 to validate TLS-SNI-01 challenges. If you want to solve challenges with a client running on your host you should make sure it uses these ports to respond to validation requests, or update the VA configuration's portConfig to use ports 80 and 443 to match how the VA operates in production and staging environments. If you use a host-based firewall (e.g. ufw or iptables) make sure you allow connections from the Docker instance to your host on the required ports.

By default Boulder runs the legacy ACME v1 API endpoint on port 4000 and the ACME v2 API endpoint on port 4001.

If a base image changes (i.e. letsencrypt/boulder-tools) you will need to rebuild images for both the boulder and bhsm containers and re-create them. The quickest way to do this is with this command:

./docker-rebuild.sh

Working with a client:

Check out the Certbot client from https://github.com/certbot/certbot and follow the setup instructions there. Once you've got the client set up, you'll probably want to run it against your local Boulder. There are a number of command line flags that are necessary to run the client against a local Boulder, and without root access. The simplest way to run the client locally is to source a file that provides an alias for certbot (certbot_test) that has all those flags:

source ~/certbot/tests/integration/_common.sh
certbot_test certonly -a standalone -d example.com

Your local Boulder instance uses a fake DNS server that returns 127.0.0.1 for any query, so you can use any value for the -d flag. You can also override that value by setting the environment variable FAKE_DNS=1.2.3.4

By default certbot_test will use -server 127.0.0.1:4000/directory, the ACME v1 API endpoint. To test ACME v2 (e.g. for wildcard issuance) please use --server 127.0.0.1:4001/directory to access the ACME v2 endpoint on port 4001.

Component Model

The CA is divided into the following main components:

1. Web Front End
2. Registration Authority
3. Validation Authority
4. Certificate Authority
5. Storage Authority
6. OCSP Updater
7. OCSP Responder

This component model lets us separate the function of the CA by security context. The Web Front End and Validation Authority need access to the Internet, which puts them at greater risk of compromise. The Registration Authority can live without Internet connectivity, but still needs to talk to the Web Front End and Validation Authority. The Certificate Authority need only receive instructions from the Registration Authority. All components talk to the SA for storage, so lines indicating SA RPCs are not shown here.

                             +--------- OCSP Updater
                             |               |
                             v               |
                            CA               |
                             ^               |
                             |               v
       Subscriber -> WFE --> RA --> SA --> MariaDB
                             |               ^
Subscriber server <- VA <----+               |
                                             |
          Browser ------------------>  OCSP Responder

Internally, the logic of the system is based around four types of objects: registrations, authorizations, challenges, and certificates, mapping directly to the resources of the same name in ACME.

Requests from ACME clients result in new objects and changes to objects. The Storage Authority maintains persistent copies of the current set of objects.

Objects are also passed from one component to another on change events. For example, when a client provides a successful response to a validation challenge, it results in a change to the corresponding validation object. The Validation Authority forwards the new validation object to the Storage Authority for storage, and to the Registration Authority for any updates to a related Authorization object.

Boulder uses gRPC for inter-component communication. For components that you want to be remote, it is necessary to instantiate a "client" and "server" for that component. The client implements the component's Go interface, while the server has the actual logic for the component. More details on this communication model can be found in the gRPC documentation.

The full details of how the various ACME operations happen in Boulder are laid out in DESIGN.md

Dependencies

All Go dependencies are vendored under the vendor directory, to make dependency management easier.

Local development also requires a MariaDB 10 installation. MariaDB should be run on port 3306 for the default integration tests.

To update the Go dependencies:

# Fetch godep
go get -u github.com/tools/godep
# Check out the currently vendorized version of each dependency.
godep restore
# Clear the stored dependencies
rm -r Godeps/ vendor/
# Update to the latest version of a dependency. Note: Our integration tests will
# verify that they can re-generate Godeps.json from scratch, which means that
# it's important that you have the same set of tags in your local copy of any
# repositories as the origin does. That means you can't use `go get -u`, you
# must cd to the path and use `git remote update`, which fetches tags. Example:
cd $GOPATH/src/github.com/cloudflare/cfssl
git remote update
git checkout master
git pull origin master
# Re-vendor the dependencies from scratch
godep save ./...
git commit Godeps/ vendor/

NOTE: If you get "godep: no packages can be updated," there's a good chance you're trying to update a single package that belongs to a repo with other packages. For instance, godep update golang.org/x/crypto/ocsp will produce this error, because it's part of the golang.org/x/crypto repo, from which we also import the pkcs12 package. Godep requires that all packages from the same repo be on the same version, so it can't update just one. The error message is not particularly helpful. See tools/godep#164 for the issue dedicated to fixing it.

NOTE: Updating cfssl in particular is tricky, because cfssl vendors github.com/google/certificate-transparency/... and golang.org/x/crypto/ocsp/..., which we also vendor. In practice this means you need to check out those two dependencies to the same version cfssl uses (available in vendor/manifest in the cfssl repo). If you fail to do this, you will get conflicting types between our vendored version and the cfssl vendored version.

godep update golang.org/x/crypto/...  github.com/cloudflare/cfssl/... github.com/google/certificate-transparency/...
godep save ./...

Adding RPCs

Boulder uses gRPC for all RPCs. To add a new RPC method, add it to the relevant .proto file, then run:

docker-compose run boulder go generate ./path/to/pkg/...