How to Impersonate Two Service Accounts in GCP at the Same Time

Learn how to effectively impersonate multiple service accounts in Google Cloud Platform for seamless data management and operations across multiple projects.
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This video is based on the question https://stackoverflow.com/q/72703060/ asked by the user 'Clark McCauley' ( https://stackoverflow.com/u/13906951/ ) and on the answer https://stackoverflow.com/a/72705265/ provided by the user 'John Hanley' ( https://stackoverflow.com/u/8016720/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Impersonate Two Service Accounts in GCP at the Same Time

When working with Google Cloud Platform (GCP), managing resources across multiple projects can often lead to complex scenarios, especially when multiple service accounts are involved. A common challenge arises when you need to perform an operation that requires permissions from two different service accounts—specifically, when trying to clone a persistent disk from one project to another. In this guide, we'll explore a solution to effectively impersonate two service accounts to achieve this goal.

The Problem: Managing Two GCP Projects

Let’s break down the scenario. You have two distinct GCP projects:

Project A with Service Account A.

Project B with Service Account B.

Your goal is to read a persistent disk from Project A and create a new persistent disk in Project B. However, impersonating either one of the service accounts via a single API call isn’t sufficient. GCP's API policies dictate that you can only impersonate one identity at a time, which presents a significant hurdle in your workflow.

The Challenge

You need to make an API call that:

Reads the disk from Project A.

Creates a new disk in Project B.

Since both actions require permissions from two different service accounts, impersonating one or the other won’t work. Therefore, you need to find a way to generate an impersonation token that grants permissions for both actions simultaneously.

The Solution: Use a Service Account with Permissions in Both Projects

The recommended approach is to utilize a service account that has the necessary permissions for both projects. Here's how you can achieve that:

Step-by-Step Implementation

Create a New Service Account: If you don't already have one, create a service account that has the required roles and permissions for both Project A and Project B. This service account should have:

Read access to persistent disks in Project A.

Write access to create disks in Project B.

Grant Required Roles: You need to assign appropriate roles to this new service account in both GCP projects for it to access resources across the projects effectively:

For Project A: Grant Compute Viewer or similar roles.

For Project B: Grant Compute Admin or roles that permit disk creation.

Modify Your Impersonation Code: Adjust your existing Go code to use this new service account. Below is a refined example based on the initial code shared:

[[See Video to Reveal this Text or Code Snippet]]

Implement API Call: Now that you can obtain a token representing permissions for both projects, you can proceed with the API call to duplicate your persistent disk across projects smoothly.

Important Considerations

Service Account Policy: Ensure that any accounts you create or manage comply with your organization's policies regarding permissions and access.

Testing Permissions: After setting up the impersonation, test your implementation to confirm that the new service account can perform the intended actions without issues.

Conclusion

Using a single service account with permissions for both GCP projects is the most effective way to manage your operations involving multiple resources. By following the outlined steps, you can successfully clone a persistent disk from one GCP project to another while avoiding the problem of limited impersonation capabilities.

By implementing this strategy, you can streamline your workflow, enhance efficiency, and better manage your cloud resources. If you have further questions or need additional assistance, feel free to reach out!

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