// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.identity.authentication;

using zx;

/// The maxium size of the prekey material in bytes.
const uint32 PREKEY_MATERIAL_MAX_SIZE = 32;

/// The maxium size of enrollment data in bytes.
const uint32 ENROLLMENT_DATA_MAX_SIZE = 256;

/// Specifies the reason that a fuchsia.identity.authentication method failed.
enum Error {
    /// Some other problem occurred that cannot be classified using one of the
    /// more specific statuses. Retry is optional.
    UNKNOWN = 1;

    /// An internal error occurred. This usually indicates a bug within the
    /// component implementing the authentication mechanism. Retry is optional.
    INTERNAL = 2;

    /// The requested operation is not supported. This generally indicates that
    /// implementation of a new feature is not yet complete. The request should
    /// not be retried.
    UNSUPPORTED_OPERATION = 3;

    /// An invalid or non-functional `AuthenticationContextProvider` was
    /// provided. Retrying is unlikely to correct this error.
    INVALID_AUTH_CONTEXT = 4;

    /// The request was malformed in some way, such as supplying duplicate
    /// enrollment entries. The request should not be retried.
    INVALID_REQUEST = 5;

    /// Data supplied with the request was malformed in some way, such as
    /// supplying corrupted enrollment data. The request should not be retried.
    INVALID_DATA_FORMAT = 6;

    /// A local resource error occurred such as I/O, FIDL, or memory allocation
    /// failure. Retry, after a delay, is recommended.
    RESOURCE = 7;

    /// An interactive authentication operation was cancelled by the user.
    ABORTED = 8;

    // This enumeration may expand to include additional statuses in the future.
    // Examples are likely to include: MECHANISM_NOT_FOUND,
    // MECHANISM_NOT_AVAILABLE.
};

/// The maximum number of active enrollments per authentication mechanism and
/// account.
const uint32 MAX_ENROLLMENTS = 16;

/// Enrollments allow some authentication mechanisms to produce authentication
/// events. An enrollment must first be created in order to be authenticated
/// against. Both creation and authentication may involve user interaction.
/// An enrollment is typically tied to a user controlled authentication factor,
/// such as a fingerprint, a password or a security key.
[MaxHandles = "0"]
struct Enrollment {
    /// A unique identifier associated with the enrollment.
    EnrollmentId id;

    /// Data associated with the enrollment.
    EnrollmentData data;

    // TODO(dnordstrom): We might want to version label all persistent data in
    // the future.
};

/// A unique identifier for an `Enrollment` within an account and an
/// authentication mechanism.
alias EnrollmentId = uint64;

/// Arbitrary opaque data associated with an authentication enrollment, created
/// and subsequently read by the authentication mechanism that produced the
/// enrollment. It is meaningful only to the authenticator, and opaque to its
/// clients.
alias EnrollmentData = bytes:ENROLLMENT_DATA_MAX_SIZE;

/// Pseudo-random data associated with an enrollment of an authentication
/// mechanism capable of storage unlock. It is reproduced only upon
/// successful authentication against that enrollment.
alias PrekeyMaterial = bytes:PREKEY_MATERIAL_MAX_SIZE;

/// An authentication event is a statement which an authentication mechanism
/// makes about the presence and/or engagement of an account owner, and thus
/// affecting the entity's authentication state. The effect of an event depends
/// on the properties of the authentication mechanism which created it.
/// A positive authentication event may contribute to an increase in
/// authentication state.
[MaxHandles = "0"]
struct PositiveEvent {
    /// The UTC time when the event completed.
    zx.time timestamp;

    // TODO(dnordstrom): Add fields for account, confidence, range, engagement
    // and mobility.
};

/// A negative authentication event may contribute to a decrease in
/// authentication state.
[MaxHandles = "0"]
struct NegativeEvent {
    /// The UTC time when the event completed.
    zx.time timestamp;

    // TODO(dnordstrom): Add fields for account, range and disengagement.
};

/// A attempted authentication event may contribute to an increase in
/// authentication state if and only if the pre-key material is correct.
/// Otherwise, it does not affect the authentication state.
[MaxHandles = "0"]
struct AttemptedEvent {
    /// The UTC time when the event completed.
    zx.time timestamp;

    /// The id of the enrollment used to produce this attempt.
    EnrollmentId enrollment_id;

    /// Enrollment data which should should replace the old enrollment data upon
    /// successful authentication. This field is only populated if a
    /// change in enrollment data is required.
    EnrollmentData? updated_enrollment_data;

    /// Pre-key material produced during the authentication attempt.
    PrekeyMaterial prekey_material;

    // TODO(dnordstrom): Add fields for account, confidence, range, engagement
    // and mobility (or a shared type with PositiveEvent).
};