Credential Management Level 1

1. Introduction

This section is not normative.

Signing into websites is more difficult than it should be. The user agent is in a unique position to improve the experience in a number of ways, and most modern user agents have recognized this by providing some measure of credential management natively in the browser. For example, users can save usernames and passwords for websites; those credentials are later autofilled into sign-in forms, albeit with varying degrees of success.

The autocomplete attribute offers a declarative mechanism by which websites can work with user agents to improve the latter’s ability to detect and fill sign-in forms by marking specific fields as "username" or "password", and user agents implement a wide variety of detection heuristics to work with websites which haven’t taken the time to provide this detail in markup.

While this combination of heuristic and declarative detection works relatively well, the status quo leaves some large gaps where detection is problematic. Sites with uncommon sign-in mechanisms (submitting credentials via XMLHttpRequest [XMLHTTPREQUEST], for instance) are difficult to reliably detect, as is the increasingly common case in which users wish to authenticate themselves using a federated identity provider. Allowing websites to more directly interact with the user agent’s credential manager would allow the credential manager to be more accurate on the one hand, and to assist users with federated sign-in on the other.

These use cases are explored in more detail in § 1.1 Use Cases and in Credential Management: Use Cases and Requirements; this specification attempts to address many of the requirements that document outlines by defining a Credential Manager API which a website can use to request credentials for a user, and to ask the user agent to persist credentials when a user signs in successfully.

Note: The API defined here is intentionally small and simple: it does not intend to provide authentication in and of itself, but is limited to providing an interface to the existing credential managers implemented by existing user agents. That functionality is valuable right now, without significant effort on the part of either vendors or authors. There’s certainly quite a bit more which could be done, of course. See § 9 Future Work for some thoughts we’ve punted for now, but which could be explored in future iterations of this API.

1.1. Use Cases

Modern user agents generally offer users the capability to save passwords when signing into a website, and likewise offer the capability to fill those passwords into sign-in forms fully- or semi-automatically when users return to a website. From the perspective of a website, this behavior is completely invisible: the website doesn’t know that passwords have been stored, and it isn’t notified that passwords have been filled. This is both good and bad. On the one hand, a user agent’s password manager works regardless of whether or not a site cooperates, which is excellent for users. On the other, the password managers' behaviors are a fragile and proprietary hodgepodge of heuristics meant to detect and fill sign-in forms, password change forms, etc.

A few problems with the status quo stand out as being particularly noteworthy:

• User agents have an incredibly difficult time helping users with federated identity providers. While detecting a username/password form submission is fairly straightforward, detecting sign-in via a third-party is quite difficult to reliably do well. It would be nice if a website could help the user agent understand the intent behind the redirects associated with a typical federated sign-in action.

• Likewise, user agents struggle to detect more esoteric sign-in mechanisms than simple username/password forms. Authors increasingly asynchronously sign users in via XMLHttpRequest or similar mechanisms in order to improve the experience and take more control over the presentation. This is good for users, but tough for user agents to integrate into their password managers. It would be nice if a website could help the user agent make sense of the sign-in mechanism they choose to use.

• Finally, changing passwords is less well-supported than it could be if the website explicitly informed the user agent that credentials had changed.

2. Core API

From a developer’s perspective, a credential is an object which allows a developer to make an authentication decision for a particular action. This section defines a generic and extensible Credential interface which serves as a base class for credentials defined in this and other documents, along with a set of APIs hanging off of navigator.credentials.* which enable developers to obtain them.

Various credential types are each represented to JavaScript as an interface which inherits, either directly or indirectly, from the Credential interface. This document defines two such interfaces, PasswordCredential and FederatedCredential. Other specifications, for example [WEBAUTHN], define other credential types.

A credential is effective for a particular origin if it is accepted as authentication on that origin. Even if a credential is effective at a particular point in time, the UA can’t assume that the same credential will be effective at any future time, for a couple reasons:

1. A password credential may stop being effective if the account holder changes their password.

2. A credential made from a token received over SMS is likely to only be effective for a single use.

Single-use credentials are generated by a credential source, which could be a private key, access to a federated account, the ability to receive SMS messages at a particular phone number, or something else. Credential sources are not exposed to Javascript or explicitly represented in this specification. To unify the model, we consider a password to be a credential source on its own, which is simply copied to create password credentials.

Even though the UA can’t assume that an effective credential will still be effective if used a second time, or that a credential source that has generated an effective credential will be able to generate a second effective credential in the future, the second is more likely than the first. By recording (with store()) which credentials have been effective in the past, the UA has a better chance of offering effective credential sources to the user in the future.

2.1. Infrastructure

User agents MUST internally provide a credential store, which is a vendor-specific, opaque storage mechanism to record which credentials have been effective. It offers the following capabilities for credential access and persistence:

1. Store a credential for later retrieval. This accepts a credential, and inserts it into the credential store.

2. Retrieve a list of credentials. This accepts an arbitrary filter, and returns a set of credentials that match the filter.

3. Modify a credential. This accepts a credential, and overwrites the state of an existing credential in the credential store.

Additionally, the credential store should maintain a prevent silent access flag for origins (which is set to true unless otherwise specified). An origin requires user mediation if its flag is set to true.

Note: The importance of user mediation is discussed in more detail in § 5 User Mediation.

Note: The credential store is an internal implementation detail of a user agent’s implementation of the API specified in this document, and is not exposed to the web directly. More capabilities may be specified by other documents in support of specific credential types.

This document depends on the Infra Standard for a number of foundational concepts used in its algorithms and prose [INFRA].

Each environment settings object has an associated active credential types, a set which is initially empty.

2.1.1. Infrastructure Algorithms

2.1.1.1. Same-Origin with its Ancestors

An environment settings object (settings) is same-origin with its ancestors if the following algorithm returns true:

1. If settings’s relevant global object has no associated Document, return false.

2. Let document be settings’ relevant global object's associated Document.

3. If document has no browsing context, return false.

4. Let origin be settings’ origin.

5. Let navigable be document’s node navigable.

6. While navigable has a non-null parent:

   1. Set navigable to navigable’s parent.

   2. If navigable’s active document's origin is not same origin with origin, return false.

7. Return true.

2.1.2. Credential Type Registry

This registry maps credential types (i.e., [[type]] values) to various values associated with a given credential type. For example: the Options Member Identifier (formally, a dictionary member identifier) used in CredentialCreationOptions and CredentialRequestOptions (i.e., "options dictionaries") by their specifications.

Note: This registry is used by the relevant credential interface objects algorithm.

2.1.2.1. Registration Entry Requirements and Update Process

• Each credential type must be unique amongst the set of credential types.

• Each registry entry must state the dictionary member identifier (known as the Options Member Identifier in the registry) used in the credential specification’s extentions of CredentialCreationOptions and CredentialRequestOptions.

• Each registry entry must state the Appropriate Interface Object identifier for the credential type.

• Each registry entry must state the Get Permissions Policy permission used when executing Request a Credential for a credential type, or null if no permissions policy is specified.

• Each registry entry must state the Create Permissions Policy permission used when executing Create a Credential for a credential type, or null if no permissions policy is specified.

• Each registry entry must include a link that references a publicly available specification defining the credential type and the dictionary member identifier.

• Each registry entry’s specification must include the requestor’s contact information.

An update to this registry is an addition, change or deletion of a credential type's registry entry. Any person can request an update to this registry by pull requests to the webappsec-credential-management repository. The Web Applications Security Working Group will place it on an upcoming meeting agenda and notify the requestor. Consideration and disposition of the request is by consensus of the W3C Web Applications Security Working Group. The Chair will then notify the requestor of the outcome and update the registry accordingly.

2.2. The Credential Interface

[Exposed=Window, SecureContext]
interface Credential {
  readonly attribute USVString id;
  readonly attribute DOMString type;
  static Promise<boolean> isConditionalMediationAvailable();
  static Promise<undefined> willRequestConditionalCreation();
};

Talk to Tobie/Dominic about the interface object bits, here and in § 2.5.1 Request a Credential, etc. I’m not sure I’ve gotten the terminology right. interface prototype object, maybe?

Some Credential objects are origin bound: these contain an internal slot named [[origin]], which stores the origin for which the Credential may be effective.

2.2.1. Credential Internal Methods

The Credential interface object features several internal methods facilitating retrieval and storage of Credential objects, with default "no-op" implementations as specified in this section, below.

Unless otherwise specified, each interface object created for interfaces which inherit from Credential MUST provide implementations for at least one of these internal methods, overriding Credential's default implementations, as appropriate for the credential type. E.g., § 3.2 The PasswordCredential Interface, § 4.1 The FederatedCredential Interface, and [WEBAUTHN].

2.2.1.1. [[CollectFromCredentialStore]] internal method

Credential's default implementation of [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors):

1. Return an empty set.

2.2.1.2. [[DiscoverFromExternalSource]] internal method

Credential's default implementation of [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors):

1. Return null.

2.2.1.3. [[Store]] internal method

Credential's default implementation of [[Store]](credential, sameOriginWithAncestors):

1. Throw a NotSupportedError.

2.2.1.4. [[Create]] internal method

• creates a Credential, or

• does not create a credential and returns null, or

• throws an error if creation fails due to exceptional situations (for example, incorrect options could produce a TypeError).

When creating a Credential, it will return an algorithm that takes a global object and returns an interface object inheriting from Credential. This algorithm MUST be invoked from a task.

Note: This algorithm’s steps are defined on a per-credential type basis.

Credential's default implementation of [[Create]](origin, options, sameOriginWithAncestors):

1. Return null.

2.2.2. CredentialUserData Mixin

Some Credential objects contain data which aims to give users a human-readable disambiguation mechanism in the credential chooser by providing a friendly name and icon:

[SecureContext]
interface mixin CredentialUserData {
  readonly attribute USVString name;
  readonly attribute USVString iconURL;
};

2.3. navigator.credentials

Developers retrieve Credentials and interact with the user agent’s credential store via methods exposed on the CredentialsContainer interface, which hangs off the Navigator object as navigator.credentials.

partial interface Navigator {
  [SecureContext, SameObject] readonly attribute CredentialsContainer credentials;
};

The credentials attribute MUST return the CredentialsContainer associated with the active document's browsing context.

Note: As discussed in § 6.3 Insecure Sites, the credential management API is exposed only in Secure Contexts.

[Exposed=Window, SecureContext]
interface CredentialsContainer {
  Promise<Credential?> get(optional CredentialRequestOptions options = {});
  Promise<undefined> store(Credential credential);
  Promise<Credential?> create(optional