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 CredentialCreationOptions options = {});
  Promise<undefined> preventSilentAccess();
};

dictionary CredentialData {
  required USVString id;
};

2.3.1. The CredentialRequestOptions Dictionary

In order to retrieve a Credential via get(), the caller specifies a few parameters in a CredentialRequestOptions object.

Note: The CredentialRequestOptions dictionary is an extension point. If and when new types of credentials are introduced that require options, their dictionary types will be added to the dictionary so they can be passed into the request. See § 8.2 Extension Points.

dictionary CredentialRequestOptions {
  CredentialMediationRequirement mediation = "optional";
  AbortSignal signal;
};

2.3.2. Mediation Requirements

When making a request via get(options) or create(options), developers can set a case-by-case requirement for user mediation by choosing the appropriate CredentialMediationRequirement enum value.

Note: The § 5 User Mediation section gives more detail on the concept in general, and its implications on how the user agent deals with individual requests for a given origin).

enum CredentialMediationRequirement {
  "silent",
  "optional",
  "conditional",
  "required"
};

2.3.2.1. Examples

window.addEventListener('load', async () => {
  const credentials = await navigator.credentials.get({
    ...,
    mediation: 'silent'
  });
  if (credentials) {
    // Hooray! Let’s sign the user in using these credentials!
  }
});

document.querySelector('#sign-in').addEventListener('click', async () => {
  const credentials = await navigator.credentials.get({
    ...,
    mediation: 'optional'
  });
  if (credentials) {
    // Hooray! Let’s sign the user in using these credentials!
  }
});

document.querySelector('#important-form').addEventListener('submit', async () => {
  const credentials = await navigator.credentials.get({
    ...,
    mediation: 'required'
  });
  if (credentials) {
    // Verify that |credentials| enables access, and cancel the submission
    // if it doesn’t.
  } else {
    e.preventDefault();
  }
});

document.querySelector('#switch-button').addEventListener('click', e => {
  var c = await navigator.credentials.get({
    ...,
    mediation: 'required'
  });
  if (c) {
    // Sign the user in using |c|.
  }
});

2.4. The CredentialCreationOptions Dictionary

In order to create a Credential via create(), the caller specifies a few parameters in a CredentialCreationOptions object.

Note: The CredentialCreationOptions dictionary is an extension point. If and when new types of credentials are introduced, they will add to the dictionary so they can be passed into the creation method. See § 8.2 Extension Points, and the extensions introduced in this document: § 3.2 The PasswordCredential Interface and § 4.1 The FederatedCredential Interface.

dictionary CredentialCreationOptions {
  CredentialMediationRequirement mediation = "optional";
  AbortSignal signal;
};

2.5. Algorithms

2.5.1. Request a Credential

The Request a Credential algorithm accepts a CredentialRequestOptions (options), and returns a Promise that resolves with a Credential if one can be unambigiously obtained, or with null if not.

1. Let settings be the current settings object.

2. Assert: settings is a secure context.

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

4. If document is not fully active, then return a promise rejected with an "InvalidStateError" DOMException.

5. If options.signal is aborted, then return a promise rejected with options.signal’s abort reason.

6. Let interfaces be options’s relevant credential interface objects.

7. If interfaces is empty, then returna promise rejected with a "NotSupportedError" DOMException.

8. For each interface of interfaces:

   1. If options.mediation is conditional and interface does not support conditional user mediation, return a promise rejected with a "TypeError" DOMException.

   2. If settings’ active credential types contains interface’s [[type]], return a promise rejected with a "NotAllowedError" DOMException.

   3. Append interface’s [[type]] to settings’ active credential types.

9. Let origin be settings’ origin.

10. Let sameOriginWithAncestors be true if settings is same-origin with its ancestors, and false otherwise.

11. For each interface in options’ relevant credential interface objects:

    1. Let permission be the interface’s [[type]] Get Permissions Policy.

    2. If permission is null, continue.

    3. If document is not allowed to use permission, return a promise rejected with a "NotAllowedError" DOMException.

12. Let p be a new promise.

13. Run the following steps in parallel:

    1. Let credentials be the result of collecting Credentials from the credential store, given origin, options, and sameOriginWithAncestors.

    2. If credentials is an exception, reject p with credentials.

    3. If all of the following statements are true, resolve p with credentials[0] and skip the remaining steps:

       1. credentials’ size is 1

       2. origin does not require user mediation

       3. options is matchable a priori.

       4. options.mediation is not "required".

       5. options.mediation is not "conditional".

       This might be the wrong model. It would be nice to support a site that wished to accept either username/passwords or webauthn-style credentials without forcing a chooser for those users who use the former, and who wish to remain signed in.

    4. If options’ mediation is "silent", resolve p with null, and skip the remaining steps.

    5. Let result be the result of asking the user to choose a Credential, given options and credentials.

    6. If result is an interface object:

       1. Set result to the result of executing result’s [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors), given origin, options, and sameOriginWithAncestors.

          If that threw an exception:

          1. Let e be the thrown exception.

          2. Queue a task on global’s DOM manipulation task source to run the following substeps:

             1. Reject p with e.

          3. Terminate these substeps.

    7. Assert: result is null, or a Credential.

    8. If result is a Credential, resolve p with result.

    9. If result is null and options.mediation is not conditional, resolve p with result.

       Note: if options.mediation is conditional and a null credential is discovered, promise p is not resolved.

14. React to p:

    1. For each interface in interfaces:

       1. Remove interface’s [[type]] from settings’ active credential types.

15. Return p.

2.5.2. Collect Credentials from the credential store

Given an origin (origin), a CredentialRequestOptions (options), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors), the user agent may collect Credentials from the credential store, returning a set of Credential objects stored by the user agent locally that match options’ filter. If no such Credential objects are known, the returned set will be empty:

1. Let possible matches be an empty set.

2. For each interface in options’ relevant credential interface objects:

   1. Let r be the result of executing interface’s [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors) internal method on origin, options, and sameOriginWithAncestors. If that threw an exception, rethrow that exception.

   2. Assert: r is a list of interface objects.

   3. For each c in r:

      1. Append c to possible matches.

3. Return possible matches.

2.5.3. Store a Credential

The Store a Credential algorithm accepts a Credential (credential), and returns a Promise which resolves once the object is persisted to the credential store.

1. Let settings be the current settings object.

2. Assert: settings is a secure context.

3. If settings’s relevant global object's associated Document is not fully active, then return a promise rejected with an "InvalidStateError" DOMException.

4. Let sameOriginWithAncestors be true if the current settings object is same-origin with its ancestors, and false otherwise.

5. Let p be a new promise.

6. If settings’ active credential types contains credential’s [[type]], return a promise rejected with a "NotAllowedError" DOMException.

7. Append credential’s [[type]] to settings’ active credential types.

8. Run the following steps in parallel:

   1. Execute credential’s interface object's [[Store]](credential, sameOriginWithAncestors) internal method on credential and sameOriginWithAncestors.

      If that threw an exception:

      1. Let e be the thrown exception.

      2. Queue a task on global’s DOM manipulation task source to run the following substeps:

         1. Reject p with e.

      Otherwise, resolve p with undefined.

9. React to p:

   1. Remove credential’s [[type]] from settings’ active credential types.

10. Return p.

2.5.4. Create a Credential

The Create a Credential algorithm accepts a CredentialCreationOptions (options), and returns a Promise which resolves with a Credential if one can be created using the options provided, or null if no Credential can be created. In exceptional circumstances, the Promise may reject with an appropriate exception:

1. Let settings be the current settings object.

2. Assert: settings is a secure context.

3. Let global be settings’ global object.

4. Let document be the relevant global object's associated Document.

5. If document is not fully active, then return a promise rejected with an "InvalidStateError" DOMException.

6. Let sameOriginWithAncestors be true if the current settings object is same-origin with its ancestors, and false otherwise.

7. Let interfaces be the set of options’ relevant credential interface objects.

8. Return a promise rejected with NotSupportedError if any of the following statements are true:

   1. global does not have an associated Document.

   2. interfaces’ size is greater than 1.

      Note: It may be reasonable at some point in the future to loosen this restriction, and allow the user agent to help the user choose among one of many potential credential types in order to support a "sign-up" use case. For the moment, though, we’re punting on that by restricting the dictionary to a single entry.

9. For each interface in interfaces:

   1. Let permission be the interface’s [[type]] Create Permissions Policy.

   2. If permission is null, continue.

   3. If document is not allowed to use permission, return a promise rejected with a "NotAllowedError" DOMException.

10. If options.signal is aborted, then return a promise rejected with options.signal’s abort reason.

11. Let type be interfaces[0]'s [[type]].

12. If settings’ active credential types contains type, return a promise rejected with a "NotAllowedError" DOMException.

13. Append type to settings’ active credential types.

14. Let origin be settings’s origin.

15. Let p be a new promise.

16. Run the following steps in parallel:

    1. Let r be the result of executing interfaces[0]'s [[Create]](origin, options, sameOriginWithAncestors) internal method on origin, options, and sameOriginWithAncestors.

       If that threw an exception:

       1. Let e be the thrown exception.

       2. Queue a task on global’s DOM manipulation task source to run the following substeps:

          1. Reject p with e.

       3. Terminate these substeps.

    2. If r is a Credential or null, resolve p with r, and terminate these substeps.

    3. Assert: r is an algorithm (as defined in § 2.2.1.4 [[Create]] internal method).

    4. Queue a task on global’s DOM manipulation task source to run the following substeps:

       1. Resolve p with the result of promise-calling r given global.

17. React to p:

    1. Remove type from settings’ active credential types.

18. Return p.

2.5.5. Prevent Silent Access

The Prevent Silent Access algorithm accepts an environment settings object (settings), and returns a Promise which resolves once the prevent silent access flag is persisted to the credential store.

1. Let origin be settings’ origin.

2. If settings’s relevant global object's associated Document is not fully active, then return a promise rejected with an "InvalidStateError" DOMException.

3. Let p be a new promise.

4. Run the following seps in parallel:

   1. Set origin’s prevent silent access flag in the credential store.

   2. Resolve p with undefined.

5. Return p.

3. Password Credentials

For good or for ill, many websites rely on username/password pairs as an authentication mechanism. The PasswordCredential interface is a credential meant to enable this use case, storing both a username and password, as well as metadata that can help a user choose the right account from within a credential chooser.

3.1. Examples

3.1.1. Password-based Sign-in

navigator.credentials
  .get({ 'password': true })
  .then(credential => {
    if (!credential) {
      // The user either doesn’t have credentials for this site, or
      // refused to share them. Insert some code here to fall back to
      // a basic login form.
      return;
    }
    if (credential.type == 'password') {
      var form = new FormData();
      form.append('username_field', credential.id);
      form.append('password_field', credential.password);
      var opt = {
        method: 'POST',
        body: form,
        credentials: 'include'  // Send cookies.
      };
      fetch('https://example.com/loginEndpoint', opt)
        .then(function (response) {
          if (/* |response| indicates a successful login */) {
            // Record that the credential was effective. See note below.
            navigator.credentials.store(credential);
            // Notify the user that sign-in succeeded! Do amazing, signed-in things!
            // Maybe navigate to a landing page via location.href =
            // '/signed-in-experience'?
          } else {
            // Insert some code here to fall back to a basic login form.
          }
        });
    }
  });

navigator.credentials
  .get({ 'password': true })
  .then(credential => {
    if (!credential) {
      return; // as above...
    }
    if (credential.type === 'password') {
      document.querySelector('input[name=username_field]').value =
        credential.id;
      document.querySelector('input[name=password_field]').value =
        credential.password;
      document.getElementById('myform').submit();
    }
  });

Note: The credential chooser presented by the user agent could allow the user to choose credentials that aren’t actually stored for the current origin. For instance, it might offer up credentials from https://m.example.com when signing into https://www.example.com (as described in § 6.1 Cross-domain credential access), or it might allow a user to create a new credential on the fly. Developers can deal gracefully with this uncertainty by calling store() every time credentials are successfully used, even right after credentials have been retrieved from get(): if the credentials aren’t yet stored for the origin, the user will be given the opportunity to do so. If they are stored, the user won’t be prompted.

3.1.2. Post-sign-in Confirmation

To ensure that users are offered to store new credentials after a successful sign-in, they can to be passed to store().

<form action="https://example.com/login" method="POST" id="theForm">
  <label for="username">Username</label>
  <input type="text" id="username" name="username" autocomplete="username">
  <label for="password">Password</label>
  <input type="password" id="password" name="password" autocomplete="current-password">
  <input type="submit">
</form>

document.querySelector('#theForm').addEventListener('submit', e => {
    if (window.PasswordCredential) {
      e.preventDefault();

      // Construct a new PasswordCredential from the HTMLFormElement
      // that fired the "submit" event: this will suck up the values of the fields
      // labeled with "username" and "current-password" autocomplete
      // attributes:
      var c = new PasswordCredential(e.target);

      // Fetch the form’s action URL, passing that new credential object in
      // as a FormData object. If the response indicates success, tell the user agent
      // so it can ask the user to store the password for future use:
      var opt = {
        method: 'POST',
        body: new FormData(e.target),
        credentials: 'include'  // Send cookies.
      };
      fetch(e.target.action, opt).then(r => {
        if (/* |r| is a "successful" Response */)
          navigator.credentials.store(c);
      });
    }
});

3.1.3. Change Password

This same storage mechanism can be reused for "password change" with no modifications: if the user changes their credentials, the website can notify the user agent that they’ve successfully signed in with new credentials. The user agent can then update the credentials it stores:

<form action="https://example.com/changePassword" method="POST" id="theForm">
  <input type="hidden" name="username" autocomplete="username" value="user">
  <label for="password">New Password</label>
  <input type="password" id="password" name="password" autocomplete="new-password">
  <input type="submit">
</form>

document.querySelector('#theForm').addEventListener('submit', e => {
  if (window.PasswordCredential) {
    e.preventDefault();

    // Construct a new PasswordCredential from the HTMLFormElement
    // that fired the "submit" event: this will suck up the values of the fields
    // labeled with "username" and "new-password" autocomplete
    // attributes:
    var c = new PasswordCredential(e.target);

    // Fetch the form’s action URL, passing that new credential object in
    // as a FormData object. If the response indicates success, tell the user agent
    // so it can ask the user to store the password for future use:
    var opt = {
      method: 'POST',
      body: new FormData(e.target),
      credentials: 'include'  // Send cookies.
    };
    fetch(e.target.action, opt).then(r => {
      if (/* |r| is a "successful" Response */)
        navigator.credentials.store(c);
    });
  }
});

3.2. The PasswordCredential Interface

[Exposed=Window,
 SecureContext]
interface PasswordCredential : Credential {
  constructor(HTMLFormElement form);
  constructor(PasswordCredentialData data);
  readonly attribute USVString password;
};
PasswordCredential includes CredentialUserData;

partial dictionary CredentialRequestOptions {
  boolean password = false;
};

PasswordCredential objects can be created via navigator.credentials.create() either explicitly by passing in a PasswordCredentialData dictionary, or based on the contents of an HTMLFormElement's submittable elements.

dictionary PasswordCredentialData : CredentialData {
  USVString name;
  USVString iconURL;
  required USVString origin;
  required USVString password;
};

typedef (PasswordCredentialData or HTMLFormElement) PasswordCredentialInit;

partial dictionary CredentialCreationOptions {
  PasswordCredentialInit password;
};

PasswordCredential objects are origin bound.

PasswordCredential's interface object inherits Credential's implementation of [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors), and defines its own implementation of [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors), [[Create]](origin, options, sameOriginWithAncestors), and [[Store]](credential, sameOriginWithAncestors).

3.3. Algorithms

3.3.1. PasswordCredential’s [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors)

[[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors) is called with an origin (origin), a CredentialRequestOptions (options), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns a set of Credential objects from the credential store. If no matching Credential objects are available, the returned set will be empty.

The algorithm will throw a NotAllowedError if sameOriginWithAncestors is not true.

1. Assert: options["password"] exists.

2. If sameOriginWithAncestors is false, throw a "NotAllowedError" DOMException.

   Note: This restriction aims to address the concern raised in § 6.4 Origin Confusion.

3. Return the empty set if options["password"] is not true.

4. Return the result of retrieving credentials from the credential store that match the following filter:

   1. The credential is a PasswordCredential

   2. The credential’s [[origin]] is the same origin as origin.

3.3.2. PasswordCredential’s [[Create]](origin, options, sameOriginWithAncestors)

[[Create]](origin, options, sameOriginWithAncestors) is called with an origin (origin), a CredentialCreationOptions (options), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns a PasswordCredential if one can be created, null otherwise. The CredentialCreationOptions dictionary must have a password member which holds either an HTMLFormElement or a PasswordCredentialData. If that member’s value cannot be used to create a PasswordCredential, this algorithm will throw a TypeError exception.

1. Assert: options["password"] exists, and sameOriginWithAncestors is unused.

2. If options["password"] is an HTMLFormElement, return the result of executing Create a PasswordCredential from an HTMLFormElement given options["password"] and origin. Rethrow any exceptions.

3. If options["password"] is a PasswordCredentialData, return the result of executing Create a PasswordCredential from PasswordCredentialData given options["password"]. Rethrow any exceptions.

4. Throw a TypeError exception.

3.3.3. PasswordCredential’s [[Store]](credential, sameOriginWithAncestors)

[[Store]](credential, sameOriginWithAncestors) is called with a PasswordCredential (credential), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns undefined once credential is persisted to the credential store.

The algorithm will return a NotAllowedError if sameOriginWithAncestors is not true.

1. Throw a "NotAllowedError" DOMException without altering the user agent’s credential store if sameOriginWithAncestors is false.

   Note: This restriction aims to address the concern raised in § 6.4 Origin Confusion.

2. If the user agent’s credential store contains a PasswordCredential (stored) whose id attribute is credential’s id and whose [[origin]] slot is the same origin as credential’s [[origin]], then:

   1. If the user grants permission to update credentials (as discussed when defining user mediation), then:

      1. Set stored’s password to credential’s password.

      2. Set stored’s name to credential’s name.

      3. Set stored’s iconURL to credential’s iconURL.

   Otherwise, if the user grants permission to store credentials (as discussed when defining user mediation, then:

   1. Store a PasswordCredential in the credential store with the following properties:

      id

      credential’s id

      name,

      credential’s name

      iconURL

      credential’s iconURL

      [[origin]]

      credential’s [[origin]]

      password

      credential’s password

3.3.4. Create a PasswordCredential from an HTMLFormElement

To Create a PasswordCredential from an HTMLFormElement, given an HTMLFormElement (form) and an origin (origin), run these steps.

Note: § 3.1.2 Post-sign-in Confirmation and § 3.1.3 Change Password provide examples of the intended usage.

1. Let data be a new PasswordCredentialData dictionary.

2. Set data’s origin member’s value to origin’s value.

3. Let formData be the result of executing the FormData constructor on form.

4. Let elements be a list of all the submittable elements whose form owner is form, in tree order.

5. Let newPasswordObserved be false.

6. For each field in elements, run the following steps:

   1. If field does not have an autocomplete attribute, then skip to the next field.

   2. Let name be the value of field’s name attribute.

   3. If formData’s has() method returns false when executed on name, then skip to the next field.

   4. If field’s autocomplete attribute’s value contains one or more autofill detail tokens (tokens), then:

      1. For each token in tokens:

         1. If token is an ASCII case-insensitive match for one of the following strings, run the associated steps:

            "new-password"

            Set data’s password member’s value to the result of executing formData’s get() method on name, and newPasswordObserved to true.

            "current-password"

            If newPasswordObserved is false, set data’s password member’s value to the result of executing formData’s get() method on name.

            Note: By checking that newPasswordObserved is false, new-password fields take precedence over current-password fields.

            "photo"

            Set data’s iconURL member’s value to the result of executing formData’s get() method on name.

            "name"

            "nickname"

            Set data’s name member’s value to the result of executing formData’s get() method on name.

            "username"

            Set data’s id member’s value to the result of executing formData’s get() method on name.

7. Let c be the result of executing Create a PasswordCredential from PasswordCredentialData on data. If that threw an exception, rethrow that exception.

8. Assert: c is a PasswordCredential.

9. Return c.

3.3.5. Create a PasswordCredential from PasswordCredentialData

To Create a PasswordCredential from PasswordCredentialData, given an PasswordCredentialData (data), run these steps.

1. Let c be a new PasswordCredential object.

2. If any of the following are the empty string, throw a TypeError exception:

   • data’s id member’s value

   • data’s origin member’s value

   • data’s password member’s value

3. Set c’s properties as follows:

   password

   data’s password member’s value

   id

   data’s id member’s value

   iconURL

   data’s iconURL member’s value

   name

   data’s name member’s value

   [[origin]]

   data’s origin member’s value.

4. Return c.

3.3.6. CredentialRequestOptions Matching for PasswordCredential

Given a CredentialRequestOptions (options), the following algorithm returns "Matches" if the PasswordCredential should be available as a response to a get() request, and "Does Not Match" otherwise.

1. If options has a password member whose value is true, then return "Matches".

2. Return "Does Not Match".

4. Federated Credentials

4.1. The FederatedCredential Interface

[Exposed=Window,
 SecureContext]
interface FederatedCredential : Credential {
  constructor(FederatedCredentialInit data);
  readonly attribute USVString provider;
  readonly attribute DOMString? protocol;
};
FederatedCredential includes CredentialUserData;

dictionary FederatedCredentialRequestOptions {
  sequence<USVString> providers;
  sequence<DOMString> protocols;
};

partial dictionary CredentialRequestOptions {
  FederatedCredentialRequestOptions federated;
};

FederatedCredential objects can be created by passing a FederatedCredentialInit dictionary into navigator.credentials.create().

dictionary FederatedCredentialInit : CredentialData {
  USVString name;
  USVString iconURL;
  required USVString origin;
  required USVString provider;
  DOMString protocol;
};

partial dictionary CredentialCreationOptions {
  FederatedCredentialInit federated;
};

FederatedCredential objects are origin bound.

FederatedCredential's interface object inherits Credential's implementation of [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors), and defines its own implementation of [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors), [[Create]](origin, options, sameOriginWithAncestors), and [[Store]](credential, sameOriginWithAncestors).

Note: If, in the future, we teach the user agent to obtain authentication tokens on a user’s behalf, we could do so by building an implementation of [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors).

4.1.1. Identifying Providers

Every site should use the same identifier when referring to a specific federated identity provider. For example, Facebook Login shouldn’t be referred to as "Facebook" and "Facebook Login" and "FB" and "FBL" and "Facebook.com" and so on. It should have a canonical identifier which everyone can make use of, as consistent identification makes it possible for user agents to be helpful.

For consistency, federations passed into the APIs defined in this document (e.g. FederatedCredentialRequestOptions's providers array, or FederatedCredential's provider property) MUST be identified by the ASCII serialization of the origin the provider uses for sign in. That is, Facebook would be represented by https://www.facebook.com and Google by https://accounts.google.com.

This serialization of an origin does _not_ include a trailing U+002F SOLIDUS ("/"), but user agents SHOULD accept them silently: https://accounts.google.com/ is clearly intended to be the same as https://accounts.google.com.

4.2. Algorithms

4.2.1. FederatedCredential’s [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors)

[[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors) is called with an origin (origin), a CredentialRequestOptions (options), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns a set of Credential objects from the credential store. If no matching Credential objects are available, the returned set will be empty.

1. Assert: options["federated"] exists.

2. If sameOriginWithAncestors is false, throw a "NotAllowedError" DOMException.

   Note: This restriction aims to address the concern raised in § 6.4 Origin Confusion.

3. Return the empty set if options["federated"] is not true.

4. Return the result of retrieving credentials from the credential store that match the following filter:

   1. The credential is a FederatedCredential

   2. The credential’s [[origin]] is the same origin as origin.

   3. If options["federated"]["providers"] exists, its value contains the credentials’s provider.

   4. If options["federated"]["protocols"] exists, its value contains the credentials’s protocol.

4.2.2. FederatedCredential’s [[Create]](origin, options, sameOriginWithAncestors)

[[Create]](origin, options, sameOriginWithAncestors) is called with an origin (origin), a CredentialCreationOptions (options), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns a FederatedCredential if one can be created, null otherwise, or throws an exception in exceptional circumstances:

1. Assert: options["federated"] exists, and sameOriginWithAncestors is unused.

2. Set options["federated"]'s origin member’s value to origin’s value.

3. Return the result of executing Create a FederatedCredential from FederatedCredentialInit given options["federated"]. If that threw an exception, then rethrow that exception.

4.2.3. FederatedCredential’s [[Store]](credential, sameOriginWithAncestors)

[[Store]](credential, sameOriginWithAncestors) is called with a FederatedCredential (credential), and a boolean which is true if and only if the calling context is same-origin with its ancestors (sameOriginWithAncestors). The algorithm returns undefined once credential is persisted to the credential store.

The algorithm will return a NotAllowedError if sameOriginWithAncestors is not true.

1. Throw a "NotAllowedError" DOMException without altering the user agent’s credential store if sameOriginWithAncestors is false.

   Note: This restriction aims to address the concern raised in § 6.4 Origin Confusion.

2. If the user agent’s credential store contains a FederatedCredential whose id attribute is credential’s id and whose [[origin]] slot is the same origin as credential’s [[origin]], and whose provider is credential’s provider, then return.

3. If the user grants permission to store credentials (as discussed when defining user mediation), then store a FederatedCredential in the credential store with the following properties:

   id

   credential’s id

   name,

   credential’s name

   iconURL

   credential’s iconURL

   [[origin]]

   credential’s [[origin]]

   provider

   credential’s provider

   protocol

   credential’s protocol

4.2.4. Create a FederatedCredential from FederatedCredentialInit

To Create a FederatedCredential from FederatedCredentialInit, given a FederatedCredentialInit (init), run these steps.

1. Let c be a new FederatedCredential object.

2. If any of the following are the empty string, throw a TypeError exception:

   • init.id's value

   • init.provider's value

3. Set c’s properties as follows:

   id

   init.id's value

   provider

   init.provider's value

   iconURL

   init.iconURL's value

   name

   init.name's value

   [[origin]]

   init.origin's value.

4. Return c.

5. User Mediation

Exposing credential information to the web via an API has a number of potential impacts on user privacy. The user agent, therefore, MUST involve the user in a number of cases in order to ensure that they clearly understands what’s going on, and with whom their credentials are being shared.

We call a particular action user mediated if it takes place after gaining a user’s explicit consent. Consent might be expressed through a user’s direct interaction with a credential chooser interface, for example. In general, user mediated actions will involve presenting the user some sort of UI, and asking them to make a decision.

An action is unmediated if it takes place silently, without explicit user consent. For example, if a user configures their browser to grant persistent credential access to a particular origin, credentials may be provided without presenting the user with a UI requesting a decision.

Here we’ll spell out a few requirements that hold for all credential types, but note that there’s a good deal of latitude left up to the user agent (which is in a priviliged position to assist the user). Moreover, specific credential types may have distinct requirements that exceed the requirements laid out more generally here.

5.1. Storing and Updating Credentials

Credential information is sensitive data, and users MUST remain in control of that information’s storage. Inadvertent credential storage could, for instance, unexpectedly link a user’s local profile on a particular device to a specific online persona. To mitigate the risk of surprise:

1. Credential information SHOULD NOT be stored or updated without user mediation. For example, the user agent could display a "Save this credential?" dialog box to the user in response to each call to store().

   User consent MAY be inferred if a user agent chooses to offer a persistant grant of consent in the form of an "Always save passwords" option (though we’d suggest that user agents should err on the side of something more narrowly scoped: perhaps "Always save _generated_ passwords.", or "Always save passwords for this site.").

2. User agents SHOULD notify users when credentials are stored. This might take the form of an icon in the address bar, or some similar location.

3. User agents MUST allow users to manually remove stored credentials. This functionality might be implemented as a settings page, or via interaction with a notification as described above.

5.2. Requiring User Mediation

By default, user mediation is required for all origins, as the relevant prevent silent access flag in the credential store is set to true. Users MAY choose to grant an origin persistent access to credentials (perhaps in the form of a "Stay signed into this site." option), which would set this flag to false. In this case, the user would always be signed into that site, which is desirable from the perspective of usability and convinience, but which might nevertheless have surprising implications (consider a user agent which syncs this flag’s state across devices, for instance).

To mitigate the risk of surprise:

1. User agents MUST allow users to require user mediation for a given origin or for all origins. This functionality might be implemented as a global toggle that overrides each origin’s prevent silent access flag to return false, or via more granular settings for specific origins (or specific credentials on specific origins).

2. User agents MUST NOT set an origin's prevent silent access flag to false without user mediation. For example, the credential chooser described in § 5.3 Credential Selection could have a checkbox which the user could toggle to mark a credential as available without mediation for the origin, or the user agent could have an onboarding process for its credential manager which asked a user for a default setting.

3. User agents MUST notify users when credentials are provided to an origin. This could take the form of an icon in the address bar, or some similar location.

4. If a user clears her browsing data for an origin (cookies, localStorage, and so on), the user agent MUST set the prevent silent access flag to true for that origin.

5.3. Credential Selection

When responding to a call to get() on an origin which requires user mediation, user agents MUST ask the user for permission to share credential information. This SHOULD take the form of a credential chooser which presents the user with a list of credentials that are available for use on a site, allowing them to select one which should be provided to the website, or to abort the request entirely.

The chooser’s user interface SHOULD be implemented in such a way as to be distinguishable from UI which a website could produce. For example, the chooser might overlap the user agent’s UI in some unspoofable way.

The chooser’s user interface MUST include an indication of the origin which is requesting credentials.

The chooser’s user interface SHOULD include all Credential objects associated with the origin that requested credentials.

User agents MAY internally associate information with each Credential object beyond the attributes specified in this document in order to enhance the utility of such a chooser. For example, favicons could help disambiguate identity providers, etc. Any additional information stored MUST not be exposed directly to the web.

The chooser’s behavior is not defined here: user agents are encouraged to experiment with UI treatments that educate users about their authentication options, and guide them through the process of choosing a credential to present. That said, the interface to the chooser is as follows:

6. Security Considerations

The following sections represent guidelines for various security and privacy considerations. Individual credential types may enforce stricter or more relaxed versions of these guidelines.

6.1. Cross-domain credential access

Credentials are sensitive information, and user agents need to exercise caution in determining when they can be safely shared with a website. The safest option is to restrict credential sharing to the exact origin on which they were saved. That is likely too restrictive for the web, however: consider sites which divide functionality into subdomains like example.com vs admin.example.com.

As a compromise between annoying users, and securing their credentials, user agents:

1. MUST NOT share credentials between origins whose scheme components represent a downgrade in security. That is, it may make sense to allow credentials saved on http://example.com/ to be made available to https://example.com/ (in order to encourage developers to migrate to secure transport), but the inverse would be dangerous.

2. MAY use the Public Suffix List [PSL] to determine the effective scope of a credential by comparing the registerable domain of the credential’s [[origin]] with the origin in which get() is called. That is: credentials saved on https://admin.example.com/ and https://example.com/ MAY be offered to users when get() is called from https://www.example.com/, and vice versa.

3. MUST NOT offer credentials to an origin in response to get() without user mediation if the credential’s origin is not an exact match for the calling origin. That is, Credential objects for https://example.com would not be returned directly to https://www.example.com, but could be offered to the user via the chooser.

6.2. Credential Leakage

Developers are well-advised to take some precautions to mitigate the risk that a cross-site scripting attack could turn into persistent access to a user’s account by setting a reasonable Content Security Policy [CSP] which restricts the endpoints to which data can be sent. In particular, developers should ensure that the following directives are set, explicitly or implicitly, in their pages' policies:

• [=script-src=] and [=object-src=] both restrict script execution on a page, making it less likely that a cross-site scripting attack will succeed in the first place. If sites are populating form elements, also [=form-action=] directives should be set.

• [=connect-src=] restricts the origins to which fetch() may submit data (which mitigates the risk that credentials could be exfiltrated to evil.com.

• [=child-src=] restricts the nested browsing contexts which may be embedded in a page, making it more difficult to inject a malicious postMessage() target. [HTML]

Developers should, of course, also properly escape input and output, and consider using other layers of defense, such as Subresource Integrity [SRI] to further reduce risk.

When defining specific credential types, specific credential types SHOULD give due consideration to the ways in which credential data can be transmitted over the wire. It might be reasonable, for example, to define transmission mechanisms which are restricted to same-origin endpoints.

6.3. Insecure Sites

User agents MUST NOT expose the APIs defined here to environments which are not secure contexts. User agents might implement autofill mechanisms which store user credentials and fill sign-in forms on non-potentially trustworthy URLs, but those sites cannot be trusted to interact directly with the credential manager in any meaningful way, and those sites MUST NOT have access to credentials saved in secure contexts.

6.4. Origin Confusion

If framed pages have access to the APIs defined here, it might be possible to confuse a user into granting access to credentials for an origin other than the top-level browsing context, which is the only security origin which users can reasonably be expected to understand.

This document exposes the Credential Management APIs to those contexts, as it’s likely that some credential types will be straightforward to make available if user agents put enough thought and context into their UI.

Specific credential types, however, will be difficult to expose in those contexts without risk. Those credential types are restricted via checks in their [[Create]](origin, options, sameOriginWithAncestors), [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors), [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors), and [[Store]](credential, sameOriginWithAncestors) methods, as appropriate.

For example PasswordCredential's [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors) method will immedietely return an empty set if called from inside a Worker, or a non-top-level browsing context.

6.5. Signing-Out

If a user has chosen to automatically sign-in to websites, as discussed in § 5.2 Requiring User Mediation, then the user agent will provide credentials to an origin whenever it asks for them. The website can instruct the user agent to suppress this behavior by calling CredentialsContainer's preventSilentAccess() method, which will turn off automatic sign-in for a given origin.

The user agent relies on the website to do the right thing; an inattentive (or malicious) website could simply neglect to call this method, causing the user agent to continue providing credentials against the user’s apparent intention. This is marginally worse than the status-quo of a site that doesn’t clear user credentials when they click "Sign-out", as the user agent becomes complicit in the authentication.

The user MUST have some control over this behavior. As noted in § 5.2 Requiring User Mediation, clearing cookies for an origin will also reset that origin’s prevent silent access flag the credential store to true. Additionally, the user agent SHOULD provide some UI affordance for disabling automatic sign-in for a particular origin. This could be tied to the notification that credentials have been provided to an origin, for example.

7. Privacy Considerations

7.1. Timing Attacks

If the user has no credentials for an origin, a call to get() will resolve very quickly indeed. A malicious website could distinguish between a user with no credentials and a user with credentials who chooses not to share them.

User agents SHOULD also rate-limit credential requests. It’s almost certainly abusive for a page to request credentials more than a few times in a short period.

7.2. Chooser Leakage

If a user agent’s credential chooser displays images supplied by an origin (for example, if a Credential displays a site’s favicon), then, requests for these images MUST NOT be directly tied to instantiating the chooser in order to avoid leaking chooser usage. One option would be to fetch the images in the background when saving or updating a Credential, and to cache them for the lifetime of the Credential.

These images MUST be fetched with the credentials mode set to "omit", the service-workers mode set to "none", the client set to null, the initiator set to the empty string, and the destination "subresource".

Moreover, if the user agent allows the user to change either the name or icon associated with the credential, the alterations to the data SHOULD NOT be exposed to the website (consider a user who names two credentials for an origin "My fake account" and "My real account", for instance).

7.3. Locally Stored Data

This API offers an origin the ability to store data persistently along with a user’s profile. Since most user agents treat credential data differently than "browsing data" (cookies, etc.) this might have the side effect of surprising a user who might believe that all traces of an origin have been wiped out when they clear their cookies.

User agents SHOULD provide UI that makes it clear to a user that credential data is stored for an origin, and SHOULD make it easy for users to remove such data when they’re no longer interested in keeping it around.

9. Future Work

This section is non-normative.

The API defined here does the bare minimum to expose user agent’s credential managers to the web, and allows the web to help those credential managers understand when federated identity providers are in use. The next logical step will be along the lines sketched in documents like [WEB-LOGIN] (and, to some extent, Mozilla’s BrowserID [BROWSERID]).

The user agent is in the unique position of being able to effectively mediate the relationship between users, identity providers, and websites. If the user agent can remove some of the risk and confusion associated with the typical authentication flows, users will be in a significantly better position than today.

A natural way to expose this information might be to extend the FederatedCredential interface with properties like authentication tokens, and possibly to add some form of manifest format with properties that declare the authentication type which the provider supports.

The API described here is designed to be extensible enough to support use cases that require user interaction, perhaps with websites other than the one which requested credentials. We hope that the Promise-based system we’ve settled on is extensible enough to support these kinds of asynchronous flows which could require some level of interaction between multiple browsing contexts (e.g. mediated activity on idp.com might resolve a Promise handed back to rp.com) or between devices and user agents (e.g. [WEBAUTHN]) in the future without redesigning the API from the ground up.

Baby steps.