Do you need to grant access to data on Google Cloud, but outside of a Terra workspace? Learn a bit of the "under the hood" workings that let you interact with Google Cloud Storage and Google Cloud Compute - without directly interfacing with the Google Cloud console. If you're a user who needs this level of detail for working in Terra, read on...
Overview: How Terra interfaces with Google Cloud
To maintain the high security required for working with controlled-access data in the cloud, Terra cannot use your user ID when interacting with cloud resources external to Terra. Instead, Terra creates and uses additional Google accounts (specific to you) called "pet service accounts." Terra also puts all of these "pet service accounts" into a convenient Google Group (specific to you) called a "Proxy Group."
Pet service accounts
In addition to the user account you have registered with Terra, you also have one or more service accounts that Terra creates for you. A service account is a special type of Google account that lets Terra interface directly with Google Cloud on your behalf. For example, with a service account, your workflows and notebooks can access your data in Google Cloud.
Your pet service account has the format: pet-7293562825402802834639@.iam.gserviceaccount.com
How to find your proxy group
1. On the upper left-hand side click on the menu button (three lines at the top of any page on Terra).
2. Next to your name, click the drop down arrow.
3. Click on the profile button under your name.
4. You'll see your proxy group listed near the bottom left.
Best Practices: Use a Terra group instead of a proxy
You can create a Terra group (with a sensible name) as a proxy for your proxy.
If your registered Terra account is j_doe@someplace.org, create a Terra Group named j_doe_at_someplace_org. Don't add anyone else to this group. You can then make grants to j_doe_at_someplace_org@firecloud.org. This group contains one member, the proxy group for j_doe@someplace.org. This is much easier for a human to recognize and remember!
Why use a Terra group for external access?While it's necessary for accessing resources that exist outside of Terra, the pre-defined Proxy Group identifier is not very human-friendly. If you're looking at a list of users with access to an external GCS bucket, seeing that there's a grant to PROXY_11564882405514439@firecloud.org is not helpful unless you happen to have a way to look up that Proxy Group.
Note: This approach extends to when you actually want to make grants to groups of Terra users. It is better to add them all to a Terra group and then grant access to that group's firecloud.org Google Group.
Create your personal Terra group in four steps
1. Go to your Groups page ("Main menu" --> "Groups" from the top left of any page in Terra).
2. In the Create a New Group card, click on the blue + icon.
3. Enter your human-friendly user-ID (can be the same as your Terra login) and click the Create Group button.
Terra creates a mirrored Google group that includes your Proxy (which already includes your user ID). When you (or the owner/admin) grant access on a Google Cloud resource to the <terra-group>@firecloud.org group, both your end-user credentials and your pet service accounts have access to the resource.
4. To access external resources, owners can now grant permission to your Terra group (i.e. j_doe_at_someplace_org@firecloud.org) in GCP console. 
Using "j_doe_at_someplace_org@firecloud.org," makes it easier to see who has access permissions!
Pro-tip: Granting permission to groups of Terra usersYou can extend this to groups of Terra users, by first setting up a group for each person's Terra proxy (following the steps above).
Then create a managed group (i.e.your-lab-group) that includes all these personal groups.
To give permission to everyone in the group, you would grant access to your-lab-group@firecloud.org. Since you can add or remove group members in the UI, it's easy to adjust who has access.
Additional resources
Want to learn more about how to access advanced Google Cloud features (ones not yet available in Terra)?
- WRITE to BigQuery
- Interact with Cloud Storage buckets other than the workspace bucket
- Run dsub jobs
- Run Cloud Dataflow jobs
- Run Cloud ML engine jobs
See Accessing Google Cloud features that are not in the Terra UI.
For recommendations, see Best practices for accessing external resources (Google buckets, Google Cloud VMs, etc.).
