fix(webauthn): missing passkey finish tooling

[james-d-elliott]

This includes a function similar to ValidatePasskeyLogin and FinishDiscoverableLogin. This allows both validating a discoverable credential and deterministically finding the user in question. This is effectively missing tooling making it more difficult for people to perform this specific action.

[coderabbitai]

Walkthrough

The update refactors several login-related methods in the WebAuthn module to use named return variables and explicit response variable declarations. A new method, FinishPasskeyLogin, is introduced to handle passkey logins. The authenticator counter update in the internal validation logic is moved to occur after backup flag checks, and related error messages are clarified.

Changes

File(s)	Change Summary
webauthn/login.go	Refactored method signatures to use named return variables; added FinishPasskeyLogin; moved authenticator counter update after backup flag checks; clarified error messages.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant WebAuthn
    participant Handler
    participant Authenticator

    Client->>WebAuthn: Send login/passkey request (response)
    WebAuthn->>WebAuthn: Parse response
    alt Passkey login
        WebAuthn->>Handler: Lookup user (if discoverable)
        WebAuthn->>WebAuthn: ValidatePasskeyLogin
    else Regular login
        WebAuthn->>WebAuthn: ValidateLogin
    end
    WebAuthn->>Authenticator: Check backup flags
    WebAuthn->>Authenticator: Update counter (after flag checks)
    WebAuthn-->>Client: Return user, credential, error

Loading

Poem

A bunny hops through code so bright,
Refactors methods left and right.
Passkey logins join the show,
Authenticator counters move below.
With clearer words and tidy flow,
This WebAuthn is good to go!
🐇✨

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between cb74620 and 62b0643.

📒 Files selected for processing (1)

• webauthn/login.go (3 hunks)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: Analyze (go)

🔇 Additional comments (7)

webauthn/login.go (7)

199-207: LGTM - Good refactoring to named return variables

The refactoring to use named return variables improves code readability and follows Go best practices. The explicit declaration of parsedResponse before parsing is also a good practice that makes the code more maintainable.

---

212-220: LGTM - Consistent refactoring pattern

The changes maintain consistency with the FinishLogin method refactoring, using the same pattern of named return variables and explicit variable declaration.

---

222-233: LGTM - Well-implemented new method following established patterns

The new FinishPasskeyLogin method correctly follows the established pattern of the other Finish* methods while appropriately returning both user and credential for passkey authentication. The implementation properly delegates to ValidatePasskeyLogin and handles error cases consistently.

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236-246: LGTM - Consistent method signature update

The method signature update maintains consistency with the other refactored methods while preserving the existing logic and error handling.

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392-392: LGTM - Improved error message clarity

The error message is more descriptive and clearly indicates the nature of the backup flag inconsistency issue.

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397-397: LGTM - Clear and specific error message

The error message clearly explains the invalid flag combination (BE=0 and BS=1), making it easier for developers to understand the validation failure.

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400-401: LGTM - Security improvement by moving counter update

Moving the authenticator counter update to after the backup flag validation is a security improvement. This ensures that the counter is only incremented after all validations pass, preventing counter manipulation through failed validation attempts.

✨ Finishing Touches

• 📝 Generate Docstrings

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