fix(webauthn): empty aaguid fails login

[james-d-elliott]

This fixes an issue where an empty AAGUID would cause a failed login when it should be left to metadata validation.

[coderabbitai]

Walkthrough

The changes adjust the control flow in two components. In the metadata validation logic, the condition order in the ValidateMetadata function is reversed to first check that an attestation type is non-empty before evaluating the validation flag. In the WebAuthn login process, the validateLogin method now first checks if the AAGUID is empty to avoid attempting a conversion, setting it to uuid.Nil when no value is provided and proceeding with the usual conversion and error handling otherwise.

Changes

File(s)	Change Summary
protocol/metadata.go	Reordered the if-condition in ValidateMetadata to first check for a non-empty attestation type, then evaluate mds.GetValidateAttestationTypes(ctx).
webauthn/login.go	Updated validateLogin to include a conditional check for an empty credential.Authenticator.AAGUID; returns uuid.Nil when empty and otherwise proceeds with byte-to-UUID conversion and error handling.

Sequence Diagram(s)

sequenceDiagram
    participant Caller as Caller
    participant Validator as ValidateMetadata
    Note over Validator: Reordered conditions
    Caller->>Validator: Call ValidateMetadata(attestationType)
    alt Attestation Type is Non-Empty
        Validator->>Validator: Evaluate mds.GetValidateAttestationTypes(ctx)
        Note over Validator: Continue based on condition result
    else Attestation Type is Empty
        Note over Validator: Short-circuit evaluation, bypass further check
    end

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sequenceDiagram
    participant Client as Client
    participant Login as validateLogin
    Client->>Login: Initiate login process
    Login->>Login: Check if AAGUID is empty
    alt AAGUID is empty
        Login->>Login: Set aaguid = uuid.Nil
    else
        Login->>Login: Convert AAGUID bytes to UUID
        alt Conversion fails
            Login->>Client: Return conversion error
        else Conversion succeeds
            Login->>Client: Continue login processing
        end
    end

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Possibly related PRs

• fix(webauthn): login validates attestation format #384: Modifies conditional logic in the validateLogin method and interactions with ValidateMetadata, indicating a direct relationship between the changes.
• feat(metadata)!: rework as a provider #239: Introduces modifications to the ValidateMetadata function in a new metadata.go file, showing a direct code-level connection with these changes.

Poem

Hop along in code so bright,
I’m a rabbit dancing through the night,
Conditions now align just right,
AAGUID safe from conversion’s plight,
With hops and bytes, we code with might! 🐇🥕

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📜 Recent review details

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Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between f9a563b and 46750bf.

📒 Files selected for processing (2)

• protocol/metadata.go (1 hunks)
• webauthn/login.go (1 hunks)

🧰 Additional context used

🧬 Code Definitions (1)

webauthn/login.go (1)

webauthn/authenticator.go (1)

• Authenticator (7-26)

⏰ Context from checks skipped due to timeout of 90000ms (1)

• GitHub Check: Analyze (go)

🔇 Additional comments (2)

protocol/metadata.go (1)

39-39: Good optimization: Condition order improvement

Reordering the condition to check attestationType != "" first is a logical improvement. This change ensures that the mds.GetValidateAttestationTypes(ctx) function is only called when necessary, following the fail-fast principle.

webauthn/login.go (1)

346-348: Good fix for the empty AAGUID issue

This change properly handles the case when credential.Authenticator.AAGUID is empty by setting aaguid to uuid.Nil instead of attempting to convert an empty byte array. This fixes the login failure issue mentioned in the PR description.

The code now correctly:

1. Checks if the AAGUID byte array is empty
2. Sets aaguid to uuid.Nil if empty
3. Only attempts conversion for non-empty AAGUIDs

This ensures that login with authenticators that have empty AAGUIDs will continue to metadata validation rather than failing.

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• 📝 Generate Docstrings

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