fix(auth): robustly enforce readonly scopes by injecting prompt=consent

[dumko2001]

Description

Robustly enforce readonly scopes by injecting prompt=consent into the OAuth flow when the --readonly flag is used. This ensures that Google always returns a refresh token and honors the requested readonly scopes, even if the user had previously authenticated with broader scopes.

The implementation:

• Updates CliFlowDelegate to handle a force_consent flag.
• Dynamically injects or modifies the prompt parameter in the OAuth URL to include consent, while preserving existing prompt values (e.g. select_account) using space-delimiting as per RFC 6749.
• Passes the force_consent flag to the authenticator based on the presence of --readonly in the login arguments.

Fixes #168

Dry Run Output:
N/A (Authentication flow change)

Checklist:

• My code follows the AGENTS.md guidelines (no generated google-* crates).
• I have run cargo fmt --all to format the code perfectly.
• I have run cargo clippy -- -D warnings and resolved all warnings.
• I have added tests that prove my fix is effective or that my feature works.
• I have provided a Changeset file (e.g. via pnpx changeset) to document my changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 937c6bf

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

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 addresses an issue where readonly scopes might not be consistently enforced during the OAuth authentication process. By introducing a mechanism to explicitly inject prompt=consent into the OAuth URL when the --readonly flag is active, the system now guarantees that Google always returns a refresh token and respects the requested readonly permissions, thereby improving the reliability and security of authentication for readonly operations.

Highlights

• Enforce Readonly Scopes: The OAuth flow now robustly enforces readonly scopes by injecting prompt=consent into the authorization URL when the --readonly flag is used. This ensures a refresh token is always returned and requested readonly scopes are honored, even if prior authentication had broader scopes.
• CliFlowDelegate Update: The CliFlowDelegate struct was updated to include a force_consent flag, which controls the injection of the prompt=consent parameter.
• Dynamic Prompt Injection: The InstalledFlowDelegate implementation now dynamically modifies or injects the prompt parameter in the OAuth URL to include consent, while carefully preserving any other existing prompt values (e.g., select_account) using space-delimiting.
• Readonly Flag Detection: The handle_login function was updated to detect the presence of the --readonly command-line argument and pass this information as the force_consent flag to the authenticator.

Changelog

• .changeset/fix-issue-168-readonly-scope.md
  • Added a new changeset entry documenting the fix for issue gws auth login --readonly + auth export --unmasked appears to allow full access on external machine #168.
• src/auth_commands.rs
  • Added a force_consent field to the CliFlowDelegate struct.
  • Modified the InstalledFlowDelegate::present_user_url method to dynamically inject prompt=consent into the OAuth URL if force_consent is true, handling existing prompt parameters gracefully.
  • Updated the handle_login function to detect the --readonly command-line argument.
  • Configured the CliFlowDelegate with the force_consent flag based on the detection of the --readonly argument during authenticator setup.

Activity

• No specific activity (comments, reviews, or progress updates) has been recorded for this pull request yet.

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[gemini-code-assist]

Code Review

This pull request robustly enforces readonly scopes by injecting prompt=consent into the OAuth flow. The changes are well-structured, adding a force_consent flag to CliFlowDelegate and dynamically modifying the OAuth URL. My main feedback is to improve the robustness of the check for an existing consent value in the prompt parameter to avoid potential issues with partial matches.

[dumko2001]

Applied the suggested fix for robust prompt=consent injection. Now splitting by %20 and performing an exact match check, while also handling empty prompt parameters.

[googleworkspace-bot]

/gemini review

[gemini-code-assist]

Code Review

This pull request correctly implements the logic to enforce readonly scopes by injecting prompt=consent into the OAuth flow. The changes to pass the --readonly flag down to the CliFlowDelegate are well done.