feat(credential_store): add GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND env var

[jpoehnelt]

Summary

Adds gogcli-style backend selection for encryption key storage, inspired by gogcli.

GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND

Value	Behavior
keyring (default)	OS keyring with .encryption_key file fallback
file	.encryption_key file only — for Docker/CI/headless

Key changes

• Never delete .encryption_key — it always serves as a durable fallback for ephemeral keyring environments
• When generating new keys with backend=keyring, save to both keyring and file
• Extract KeyringProvider trait + resolve_key() for testability
• 25 unit tests covering both backends and all edge cases
• Updated env var help, README, AGENTS.md

Root cause (#344)

The previous fix for #344 deleted .encryption_key when the OS keyring succeeded. In Docker containers, the keyring is ephemeral, so the key was permanently lost on container restart. This PR preserves the file and adds an explicit env var to bypass the keyring entirely.

Fixes #344

[changeset-bot]

🦋 Changeset detected

Latest commit: 80ce461

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@googleworkspace/cli	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new environment variable to provide explicit control over the encryption key storage backend, addressing a critical issue where keys were lost in ephemeral environments. By ensuring the .encryption_key file is always preserved as a durable fallback and refining the key resolution process, the changes significantly enhance the reliability and flexibility of credential management, particularly for headless and containerized deployments. The update also includes substantial refactoring for testability and comprehensive new unit tests.

Highlights

• Keyring Backend Selection: Introduced the GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND environment variable, allowing users to explicitly choose between keyring (OS keyring with file fallback) and file (file-only) for encryption key storage.
• Durable Key Fallback: Ensured that the .encryption_key file is never deleted, establishing it as a permanent and durable fallback for encryption keys, especially crucial for ephemeral environments like Docker or CI/CD.
• Key Generation Strategy: Modified key generation to save new keys to both the OS keyring and the .encryption_key file when the keyring backend is active, enhancing resilience.
• Improved Testability: Refactored the key resolution logic by extracting a KeyringProvider trait and a resolve_key() function, significantly improving the testability of the credential store.
• Comprehensive Testing: Added 25 new unit tests to cover all new key resolution scenarios, including both backend types and various edge cases, ensuring robust behavior.
• Documentation Updates: Updated relevant documentation files, including AGENTS.md, README.md, and CLI usage help, to reflect the new environment variable and the updated key storage behavior.

Changelog

• .changeset/fix-keyring-fallback.md
  • Added a new changeset entry documenting the GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND environment variable and the fix for credential key loss.
• AGENTS.md
  • Updated the environment variable documentation to include GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND.
• README.md
  • Updated the interactive authentication section to mention the .encryption_key file as an alternative key storage location when GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND=file.
• src/auth_commands.rs
  • Updated the authentication success message to include information about the new GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND for headless environments.
• src/credential_store.rs
  • Refactored the key management logic to introduce KeyringProvider trait, KeyringBackend enum, read_key_file, generate_random_key, and resolve_key functions.
  • Ensured the .encryption_key file is never deleted and handles different backend selections.
  • Added extensive unit tests for the new key resolution logic.
• src/main.rs
  • Added GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND to the printed CLI usage help.
• src/token_storage.rs
  • Updated a comment to reflect that encryption uses AES-256-GCM generally, rather than specifically mentioning the OS keyring as the sole key derivation source.

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[gemini-code-assist]

Code Review

This pull request introduces a robust solution for managing encryption keys by adding the GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND environment variable and ensuring the .encryption_key file is always preserved as a fallback. The refactoring of the key retrieval logic into a testable KeyringProvider trait and resolve_key function, along with the comprehensive new test suite, significantly improves the code's maintainability and correctness.

I have one high-severity concern regarding a potential race condition during initial key generation if multiple processes run simultaneously. Please see the detailed comment in src/credential_store.rs.

_{Note: Security Review did not run due to the size of the PR.}

[github-actions]

/gemini review

[codecov]

Codecov Report

❌ Patch coverage is 95.60440% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.21%. Comparing base (5e7d120) to head (80ce461).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/credential_store.rs	96.12%	14 Missing ⚠️
src/auth_commands.rs	50.00%	1 Missing ⚠️
src/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #359      +/-   ##
==========================================
+ Coverage   62.17%   63.21%   +1.04%     
==========================================
  Files          38       38              
  Lines       14797    15102     +305     
==========================================
+ Hits         9200     9547     +347     
+ Misses       5597     5555      -42     

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[github-actions]

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[github-actions]

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