Enforce dedicated service account for Cloud Build triggers

[alex-doudou]

• Tests pass
• Appropriate changes to documentation are included in the PR

This PR:

• updated how_to_create_cloudbuild_trigger.md to include a mandatory step for creating/using a dedicated service account.
• explicitly assigned required roles (logging, artifactregistry, developerconnect) to the dedicated SA.
• mandated passing the dedicated SA email to the create_build_trigger tool.
• updated roles to grant for the dedicated Cloud Run service account and developer connect service agent

[gemini-code-assist]

Summary of Changes

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This pull request enhances the security posture for Cloud Build triggers by mandating the use of dedicated service accounts. It ensures that triggers operate with the principle of least privilege, thereby reducing potential security risks. The changes primarily involve updating documentation to guide users through the process of setting up and assigning appropriate roles to these dedicated service accounts, and explicitly requiring their use when creating new triggers.

Highlights

• Mandatory Dedicated Service Accounts: Enforced the use of dedicated, user-managed service accounts for Cloud Build triggers to adhere to the principle of least privilege, replacing the default Compute Engine service account.
• Required IAM Roles: Explicitly defined the minimum necessary IAM roles (roles/logging.logWriter, roles/artifactregistry.writer, roles/developerconnect.tokenAccessor) that must be granted to the dedicated service account.
• Tool Parameter Update: Mandated that the email of the dedicated service account must be provided to the service_account parameter when using the create_build_trigger tool.
• Documentation Update: Updated the how_to_create_cloudbuild_trigger.md guide to include detailed steps for checking, creating, and configuring the dedicated service account.

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[gemini-code-assist]

Code Review

This pull request updates the how_to_create_cloudbuild_trigger.md documentation to include a new section on ensuring a dedicated service account is used for Cloud Build triggers, detailing the creation process and required roles, and emphasizes providing this service account to the create_build_trigger tool. Feedback indicates a critical discrepancy where the create_build_trigger tool does not enforce the use of a dedicated service account, potentially leading to security issues, and suggests modifying the tool to require this parameter. Additionally, a minor markdown formatting issue was noted in a new heading.

[alex-doudou]

Added the follow up commit to enforce the service account behaviour in our go tool as well.

The commit:

• Modified create_build_trigger to require the service_account parameter.
• Removed silent fallback to the default Compute Engine service account.
• Updated unit tests to verify the mandatory behavior and removed obsolete fallback tests.

[haroonc]

/gemini review

[gemini-code-assist]

Code Review

This pull request mandates the use of a dedicated service account for Cloud Build triggers, removing the previous fallback to the default Compute Engine service account. It expands the setPermissionsForCloudBuildSA function to automate IAM role assignments for the Cloud Build service account and associated service agents. Documentation is updated to reflect these changes. Feedback points to a potential lack of idempotency in IAM bindings, missing test coverage for resource manager errors, and minor documentation inaccuracies.