I've written a blog post here and this is the backend auth service described there.
Firebase Keysafe is a super-simple back end service designed to be deployed to Google App Engine Standard Environment, to protect the encryption keys of mobile users authenticated using Google Firebase by means of Google Cloud KMS.
First you need to initialise your environment:
# download and install google app engine sdk, (https://cloud.google.com/appengine/docs/standard/python/download)
# sort your path, restart your terminal
gcloud components install app-engine-python
virtualenv env
To configure:
- Make sure you edit app.yaml and replace <YOUR_APPENGINE_APP_ID_HERE> with the name of your App Engine app.
- In main.py, plug in values for <USE_A_SECURE_RANDOM_PASSWORD_HERE>, <KMS_KEYRING_NAME>, <KMS_KEY_ID> and <PUT_SOME_RANDOM_API_KEY_THAT_YOU_REQUIRE_HERE>
Then each time you want to test you do this:
source env/bin/activate
pip install -t lib -r requirements.txt
dev_appserver.py app.yaml
deactivate
To use:
- All requests need a query parameter 'key=<PUT_SOME_RANDOM_API_KEY_THAT_YOU_REQUIRE_HERE>' and an "Authorization" HTTP header of the form "Bearer "
- POST to '/key' to generate yourself a new encryption key. Returns JSON with "key" (the actual encryption key / DEK) and "encrypted" (that you can store safely in Firebase)
- On a new device, make a GET to '/decrypt?value=<encrypted_key>' (where encrypted_key is the value you stored in Firebase in the previous step). This will return JSON with "key" being the decrypted DEK.
It also supports group encryption keys if you use Firebase Custom Claims to add "groups=g1,g2,g3" to your users' JWTs. POST to '/groupkey?group=g1' to generate a group key, and any member of that group can then use the same '/decrypt?value=<encrypted_key>' endpoint to decrypt that key.
To deploy:
gcloud app deploy
To run unit tests:
python runner.py "{google-cloud-sdk-path}"
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