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<!-- *********** Web Authentication - Level 1 - Spec source file ***********
Notes:
* the h1 tag is spec title that is rendered within the document window. Wrapping
may be controlled with break tags. The spec 'Level' value is not appended.
* the Title metadata value is what is rendered in the browser's titlebar, any break
tags will be rendered. It also has the spec 'Level' value (gratuitously) appended.
-->
<h1>Web Authentication:<br>An API for accessing Public Key Credentials<br>Level 1</h1>
<pre class='metadata'>
Title: Web Authentication: An API for accessing Public Key Credentials - Level
Status: ED
Prepare for TR: true
TR: https://www.w3.org/TR/webauthn/
ED: https://w3c.github.io/webauthn/
Previous Version: https://www.w3.org/TR/2017/WD-webauthn-20170811/
Previous Version: https://www.w3.org/TR/2017/WD-webauthn-20170505/
Previous Version: https://www.w3.org/TR/2017/WD-webauthn-20170216/
Previous Version: https://www.w3.org/TR/2016/WD-webauthn-20161207/
Previous Version: https://www.w3.org/TR/2016/WD-webauthn-20160928/
Previous Version: https://www.w3.org/TR/2016/WD-webauthn-20160902/
Previous Version: https://www.w3.org/TR/2016/WD-webauthn-20160531/
Shortname: webauthn
Level: 1
Editor: Vijay Bharadwaj, w3cid 55440, Microsoft, vijay.bharadwaj@microsoft.com
Editor: Hubert Le Van Gong, w3cid 84817, PayPal, hlevangong@paypal.com
Editor: Dirk Balfanz, w3cid 47648, Google, balfanz@google.com
Editor: Alexei Czeskis, w3cid 87258, Google, aczeskis@google.com
Editor: Arnar Birgisson, w3cid 87332, Google, arnarb@google.com
Editor: Jeff Hodges, w3cid 43843, PayPal, Jeff.Hodges@paypal.com
Editor: Michael B. Jones, w3cid 38745, Microsoft, mbj@microsoft.com
Editor: Rolf Lindemann, w3cid 84447, Nok Nok Labs, rolf@noknok.com
Editor: J.C. Jones, w3cid 87240, Mozilla, jc@mozilla.com
group: webauthn
Issue Tracking: Github https://github.com/w3c/webauthn/issues
!Tests: <a href=https://github.com/w3c/web-platform-tests/tree/master/webauthn>web-platform-tests webauthn/</a> (<a href=https://github.com/w3c/web-platform-tests/labels/webauthn>ongoing work</a>)
Text Macro: RP Relying Party
Text Macro: RPS Relying Parties
Text Macro: INFORMATIVE <em>This section is not normative.</em>
Text Macro: WAC WebAuthn Client
Ignored Vars: op, alg, type, algorithm
Abstract: This specification defines an API enabling the creation and use of strong, attested, scoped, public key-based
credentials by web applications, for the purpose of strongly authenticating users. Conceptually, one or more [=public key
credentials=], each scoped to a given [=Relying Party=], are created and stored on an [=authenticator=] by the user agent in
conjunction with the web application. The user agent mediates access to [=public key credentials=] in order to preserve user
privacy. [=Authenticators=] are responsible for ensuring that no operation is performed without [=user consent=].
[=Authenticators=] provide cryptographic proof of their properties to [=relying parties=] via [=attestation=]. This
specification also describes the functional model for WebAuthn conformant [=authenticators=], including their signature and
[=attestation=] functionality.
Boilerplate: omit conformance, omit feedback-header, omit abstract-header
Markup Shorthands: css off, markdown on
</pre>
<!-- TODO: Clean out these anchor lists once they appear in Shepherd -->
<pre class="anchors">
spec: ECMAScript; urlPrefix: https://tc39.github.io/ecma262/#
type: method
for: JSON; text: stringify; url: sec-json.stringify
type: dfn
text: %ArrayBuffer%; url: sec-arraybuffer-constructor
url: sec-object-internal-methods-and-internal-slots
text: internal method
text: internal slot
spec: HTML52; urlPrefix: https://w3c.github.io/html/
type: dfn
urlPrefix: browsers.html
text: origin; url: concept-cross-origin
text: opaque origin; url: opaque-origin
text: tuple origin
text: document.domain; url:dom-document-domain
spec: TokenBinding; urlPrefix: https://tools.ietf.org/html/draft-ietf-tokbind-protocol#
type: dfn
text: Token Binding
text: Token Binding ID; url: section-3.2
spec: WebCryptoAPI; urlPrefix: https://www.w3.org/TR/WebCryptoAPI/
type: dfn
text: recognized algorithm name
spec: credential-management-1; urlPrefix: https://w3c.github.io/webappsec-credential-management/
type: dictionary
text: CredentialCreationOptions; url: dictdef-credentialcreationoptions
type: dictionary
text: CredentialRequestOptions; url: dictdef-credentialrequestoptions
for: Credential
type: method
text: [[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors)
text: [[Create]](origin, options, sameOriginWithAncestors)
text: [[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors)
text: [[Store]](credential, sameOriginWithAncestors)
for: CredentialsContainer
type: method
text: create(); url: dom-credentialscontainer-create
type: dfn
text: signal
text: same-origin with its ancestors; url: same-origin-with-its-ancestors
spec: mixed-content; urlPrefix: www.w3.org/TR/mixed-content/
type: dfn
text: a priori authenticated
spec: page-visibility; urlPrefix: https://www.w3.org/TR/page-visibility/
type: dfn
text: visibility states
spec: WHATWG HTML; urlPrefix: https://html.spec.whatwg.org/
type: dfn
text: focus
</pre> <!-- class=anchors -->
<!-- L128 spec:webappsec-credential-management-1; type:dictionary; for:/; text:CredentialRequestOptions -->
<pre class="link-defaults">
spec:credential-management; type:dfn; text:credentials
spec:html; type:dfn; for:environment settings object; text:global object
spec:infra; type:dfn; text:list
spec:infra; type:dfn; for:struct; text:item
spec:url; type:dfn; text:domain
spec:url; type:dfn; for:url; text:host
spec:url; type:dfn; text:valid domain;
spec:webidl; type:interface; text:Promise
</pre>
<pre class=biblio>
{
"IANA-COSE-ALGS-REG": {
"href": "https://www.iana.org/assignments/cose/cose.xhtml#algorithms",
"title": "IANA CBOR Object Signing and Encryption (COSE) Algorithms Registry",
"publisher": "IANA"
},
"Feature-Policy": {
"href": "https://wicg.github.io/feature-policy/",
"title": "Feature Policy",
"publisher": "WICG: Web Incubator Community Group",
"status": "Draft Community Group Report"
}
}
</pre>
# Introduction # {#intro}
[INFORMATIVE]
This specification defines an API enabling the creation and use of strong, attested, scoped, public key-based
credentials by web applications, for the purpose of strongly authenticating users. A [=public key credential=] is
created and stored by an <em>[=authenticator=]</em> at the behest of a <em>[=[RP]=]</em>, subject to <em>[=user
consent=]</em>. Subsequently, the [=public key credential=] can only be accessed by [=origins=] belonging to that [=[RP]=].
This scoping is enforced jointly by <em>[=conforming User Agents=]</em> and <em>[=authenticators=]</em>.
Additionally, privacy across [=[RPS]=] is maintained; [=[RPS]=] are not able to detect any properties, or even
the existence, of credentials scoped to other [RPS].
[=[RPS]=] employ the [=Web Authentication API=] during two distinct, but related, [=ceremonies=] involving a user. The first
is [=Registration=], where a [=public key credential=] is created on an [=authenticator=], and associated by a [=[RP]=]
with the present user's account (the account may already exist or may be created at this time). The second is
[=Authentication=], where the [=[RP]=] is presented with an <em>[=Authentication Assertion=]</em> proving the presence
and [=user consent|consent=] of the user who registered the [=public key credential=]. Functionally, the [=Web Authentication
API=] comprises a {{PublicKeyCredential}} which extends the Credential Management API [[!CREDENTIAL-MANAGEMENT-1]], and
infrastructure which allows those credentials to be used with {{CredentialsContainer/create()|navigator.credentials.create()}} and
{{CredentialsContainer/get()|navigator.credentials.get()}}. The former is used during [=Registration=], and the
latter during [=Authentication=].
Broadly, compliant [=authenticators=] protect [=public key credentials=], and interact with user agents to implement the
[=Web Authentication API=]. Some authenticators may run on the same computing device (e.g., smart phone, tablet, desktop PC) as
the user agent is running on. For instance, such an authenticator might consist of a Trusted Execution Environment (TEE) applet,
a Trusted Platform Module (TPM), or a Secure Element (SE) integrated into the computing device in conjunction with some means
for [=user verification=], along with appropriate platform software to mediate access to these components' functionality. Other
authenticators may operate autonomously from the computing device running the user agent, and be accessed over a transport such
as Universal Serial Bus (USB), Bluetooth Low Energy (BLE) or Near Field Communications (NFC).
## Use Cases ## {#use-cases}
The below use case scenarios illustrate use of two very different types of [=authenticators=], as well as outline further
scenarios. Additional scenarios, including sample code, are given later in [[#sample-scenarios]].
### Registration ### {#usecase-registration}
- On a phone:
* User navigates to example.com in a browser and signs in to an existing account using whatever method they have been using
(possibly a legacy method such as a password), or creates a new account.
* The phone prompts, "Do you want to register this device with example.com?"
* User agrees.
* The phone prompts the user for a previously configured [=authorization gesture=] (PIN, biometric, etc.); the user
provides this.
* Website shows message, "Registration complete."
### Authentication ### {#usecase-authentication}
- On a laptop or desktop:
* User navigates to example.com in a browser, sees an option to "Sign in with your phone."
* User chooses this option and gets a message from the browser, "Please complete this action on your phone."
- Next, on their phone:
* User sees a discrete prompt or notification, "Sign in to example.com."
* User selects this prompt / notification.
* User is shown a list of their example.com identities, e.g., "Sign in as Alice / Sign in as Bob."
* User picks an identity, is prompted for an [=authorization gesture=] (PIN, biometric, etc.) and provides this.
- Now, back on the laptop:
* Web page shows that the selected user is signed-in, and navigates to the signed-in page.
### Other use cases and configurations ### {#other-configurations}
A variety of additional use cases and configurations are also possible, including (but not limited to):
- A user navigates to example.com on their laptop, is guided through a flow to create and register a credential on their phone.
- A user obtains an discrete, [=roaming authenticator=], such as a "fob" with USB or USB+NFC/BLE connectivity options, loads
example.com in their browser on a laptop or phone, and is guided though a flow to create and register a credential on the
fob.
- A [=[RP]=] prompts the user for their [=authorization gesture=] in order to authorize a single transaction, such as a payment
or other financial transaction.
# Conformance # {#conformance}
This specification defines three conformance classes. Each of these classes is specified so that conforming members of the class
are secure against non-conforming or hostile members of the other classes.
## User Agents ## {#conforming-user-agents}
A User Agent MUST behave as described by [[#api]] in order to be considered conformant. [=Conforming User Agents=] MAY implement
algorithms given in this specification in any way desired, so long as the end result is indistinguishable from the result that
would be obtained by the specification's algorithms.
A conforming User Agent MUST also be a conforming implementation of the IDL fragments of this specification, as described in the
“Web IDL” specification. [[!WebIDL-1]]
## Authenticators ## {#conforming-authenticators}
An [=authenticator=] MUST provide the operations defined by [[#authenticator-model]], and those operations MUST behave as
described there. This is a set of functional and security requirements for an authenticator to be usable by a [=Conforming User
Agent=].
As described in [[#use-cases]], an authenticator may be implemented in the operating system underlying the User Agent, or in
external hardware, or a combination of both.
## [RPS] ## {#conforming-relying-parties}
A [=[RP]=] MUST behave as described in [[#rp-operations]] to get the security benefits offered by this specification.
# Dependencies # {#dependencies}
This specification relies on several other underlying specifications, listed
below and in [[#index-defined-elsewhere]].
: Base64url encoding
:: The term <dfn>Base64url Encoding</dfn> refers to the base64 encoding using the URL- and filename-safe character set defined
in Section 5 of [[!RFC4648]], with all trailing '=' characters omitted (as permitted by Section 3.2) and without the
inclusion of any line breaks, whitespace, or other additional characters.
: CBOR
:: A number of structures in this specification, including attestation statements and extensions, are encoded using the Compact
Binary Object Representation (<dfn>CBOR</dfn>) [[!RFC7049]].
: CDDL
:: This specification describes the syntax of all CBOR-encoded data using the CBOR Data Definition Language (CDDL) [[!CDDL]].
: COSE
:: CBOR Object Signing and Encryption (COSE) [[!RFC8152]]. The IANA COSE Algorithms registry established by this specification is also used.
: Credential Management
:: The API described in this document is an extension of the {{Credential}} concept defined in [[!CREDENTIAL-MANAGEMENT-1]].
: DOM
:: {{DOMException}} and the DOMException values used in this specification are defined in [[!DOM4]].
: ECMAScript
:: [=%ArrayBuffer%=] is defined in [[!ECMAScript]].
: HTML
:: The concepts of [=relevant settings object=], [=origin=],
[=opaque origin=], and [=is a registrable domain suffix of or is equal to=] are defined in [[!HTML52]].
: Web IDL
:: Many of the interface definitions and all of the IDL in this specification depend on [[!WebIDL-1]]. This updated version of
the Web IDL standard adds support for {{Promise}}s, which are now the preferred mechanism for asynchronous
interaction in all new web APIs.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in [[!RFC2119]].
# Terminology # {#terminology}
: <dfn>Assertion</dfn>
:: See [=Authentication Assertion=].
: <dfn>Attestation</dfn>
:: Generally, <em>attestation</em> is a statement serving to bear witness, confirm, or authenticate.
In the WebAuthn context, [=attestation=] is employed to <em>attest</em> to the <em>provenance</em> of an [=authenticator=]
and the data it emits; including, for example: [=credential IDs=], [=credential key pairs=], signature counters, etc. An
[=attestation statement=] is conveyed in an [=attestation object=] during [=registration=]. See also [[#sctn-attestation]]
and [Figure 3](#fig-attStructs). Whether or how the client platform conveys the [=attestation statement=] and [=AAGUID=]
portions of the [=attestation object=] to the [=[RP]=] is described by [=attestation conveyance=].
: <dfn>Attestation Certificate</dfn>
:: A X.509 Certificate for the <dfn>attestation key pair</dfn> used by an [=authenticator=] to attest to its manufacture
and capabilities. At [=registration=] time, the [=authenticator=] uses the <dfn>attestation private key</dfn> to sign
the [=[RP]=]-specific [=credential public key=] (and additional data) that it generates and returns via the
[=authenticatorMakeCredential=] operation. [=[RPS]=] use the <dfn>attestation public key</dfn> conveyed in the [=attestation
certificate=] to verify the [=attestation signature=]. Note that in the case of [=self attestation=], the
[=authenticator=] has no distinct [=attestation key pair=] nor [=attestation certificate=], see [=self
attestation=] for details.
: <dfn>Authentication</dfn>
:: The [=ceremony=] where a user, and the user's computing device(s) (containing at least one [=authenticator=]) work in
concert to cryptographically prove to an [=[RP]=] that the user controls the [=credential private key=] associated with a
previously-registered [=public key credential=] (see [=Registration=]). Note that this includes a [=test of user presence=] or
[=user verification=].
: <dfn>Authentication Assertion</dfn>
:: The cryptographically signed {{AuthenticatorAssertionResponse}} object returned by an [=authenticator=] as the result of a
[=authenticatorGetAssertion=] operation.
This corresponds to the [[CREDENTIAL-MANAGEMENT-1]] specification's single-use <a
spec="credential-management">credentials</a>.
: <dfn>Authenticator</dfn>
:: A cryptographic entity used by a [=[WAC]=] to (i) generate a [=public key credential=] and register it with a [=[RP]=],
and (ii) [=authentication|authenticate=] by potentially [=user verification|verifying the user=], and then
cryptographically signing and returning, in the form of an [=Authentication Assertion=],
a challenge and other data presented by a [=[RP]=] (in concert with the [=[WAC]=]).
: <dfn>Authorization Gesture</dfn>
:: An [=authorization gesture=] is a physical interaction performed by a user with an authenticator as part of a [=ceremony=],
such as [=registration=] or [=authentication=]. By making such an [=authorization gesture=], a user [=user consent|provides
consent=] for (i.e., <em>authorizes</em>) a [=ceremony=] to proceed. This may involve [=user verification=] if the
employed [=authenticator=] is capable, or it may involve a simple [=test of user presence=].
: <dfn>Biometric Recognition</dfn
:: The automated recognition of individuals based on their biological and behavioral characteristics [[ISOBiometricVocabulary]].
: <dfn>Ceremony</dfn>
:: The concept of a [=ceremony=] [[Ceremony]] is an extension of the concept of a network protocol, with human nodes alongside
computer nodes and with communication links that include user interface(s), human-to-human communication, and transfers of
physical objects that carry data. What is out-of-band to a protocol is in-band to a ceremony. In this specification,
[=Registration=] and [=Authentication=] are ceremonies, and an [=authorization gesture=] is often a component of
those [=ceremonies=].
: <dfn>Client</dfn>
:: See [=Conforming User Agent=].
: <dfn>Client-Side</dfn>
:: This refers in general to the combination of the user's platform device, user agent, authenticators, and everything gluing
it all together.
: <dfn>Client-side-resident Credential Private Key</dfn>
:: A [=Client-side-resident Credential Private Key=] is stored either on the client platform, or in some cases on the
authenticator itself, e.g., in the case of a discrete first-factor roaming authenticator. Such <dfn>client-side credential
private key storage</dfn> has the property that the authenticator is able to select the [=credential private key=] given
only an [=RP ID=], possibly with user assistance (e.g., by providing the user a pick list of credentials associated with the RP
ID). By definition, the private key is always exclusively controlled by the Authenticator. In the case of a
[=Client-side-resident Credential Private Key=], the Authenticator might offload storage of wrapped key material to the
client platform, but the client platform is not expected to offload the key storage to remote entities (e.g. RP Server).
: <dfn>Conforming User Agent</dfn>
:: A user agent implementing, in conjunction with the underlying platform, the [=Web Authentication API=] and algorithms
given in this specification, and handling communication between [=authenticators=] and [=[RPS]=].
: <dfn>Credential ID</dfn>
:: A probabilistically-unique [=byte sequence=] identifying a [=public key credential source=] and its [=authentication assertions=].
Credential IDs are generated by [=authenticators=] in two forms:
1. At least 16 bytes that include at least 100 bits of entropy, or
1. The [=public key credential source=], without its [=Credential ID=], encrypted so only its [=managing authenticator=] can
decrypt it. This form allows the [=authenticator=] to be nearly stateless, by having the [=[RP]=] store any necessary
state.
Note: [[FIDO-UAF-AUTHNR-CMDS]] includes guidance on encryption techniques under "Security Guidelines".
[=[RPS]=] do not need to distinguish these two [=Credential ID=] forms.
: <dfn>Credential Public Key</dfn>
:: The public key portion of an [=[RP]=]-specific <dfn>credential key pair</dfn>, generated by an [=authenticator=] and
returned to an [=[RP]=] at [=registration=] time (see also [=public key credential=]). The private key portion of the
[=credential key pair=] is known as the <dfn>credential private key</dfn>. Note that in the case of [=self
attestation=], the [=credential key pair=] is also used as the [=attestation key pair=], see [=self attestation=]
for details.
: <dfn>Public Key Credential Source</dfn>
:: A [=credential source=] ([[CREDENTIAL-MANAGEMENT-1]]) used by an [=authenticator=] to generate [=authentication assertions=]. A public key credential source has:
* A [=Credential ID=].
* A [=credential private key=].
* The [=Relying Party Identifier=] for the [=[RP]=] that created this credential source.
* An optional [=user handle=] for the person who created this credential source.
* Optional other information used by the authenticator to inform its UI. For example, this might include the user's
{{displayName}}.
The [=authenticatorMakeCredential=] operation creates a [=public key credential source=] bound to a <dfn for="public key
credential source">managing authenticator</dfn> and returns the [=credential public key=] associated with its [=credential
private key=]. The [=[RP]=] can use this [=credential public key=] to verify the [=authentication assertions=] created by
this [=public key credential source=].
: <dfn>Public Key Credential</dfn>
:: Generically, a *credential* is data one entity presents to another in order to *authenticate* the former to the latter
[[RFC4949]]. The term [=public key credential=] refers to one of: a [=public key credential source=], the
possibly-[=attestation|attested=] [=credential public key=] corresponding to a [=public key credential source=], or an
[=authentication assertion=]. Which one is generally determined by context.
<div class="note">
Note: This is a [=willful violation=] of [[RFC4949]]. In English, a "credential" is both a) the thing presented to prove
a statement and b) intended to be used multiple times. It's impossible to achieve both criteria securely with a single
piece of data in a public key system. [[RFC4949]] chooses to define a credential as the thing that can be used multiple
times (the public key), while this specification gives "credential" the English term's flexibility. This specification
uses more specific terms to identify the data related to an [[RFC4949]] credential:
: "Authentication information" (possibly including a private key)
:: [=Public key credential source=]
: "Signed value"
:: [=Authentication assertion=]
: [[RFC4949]] "credential"
:: [=Credential public key=] or [=attestation object=]
</div>
At [=registration=] time, the [=authenticator=] creates an asymmetric key pair, and stores its [=credential private
key|private key portion=] and information from the [=[RP]=] into a [=public key credential source=]. The [=credential public
key|public key portion=] is returned to the [=[RP]=], who then stores it in conjunction with the present user's account.
Subsequently, only that [=[RP]=], as identified by its [=RP ID=], is able to employ the [=public key credential=] in
[=authentication|authentication ceremonies=], via the {{CredentialsContainer/get()}} method. The [=[RP]=] uses its stored
copy of the [=credential public key=] to verify the resultant [=authentication assertion=].
: <dfn>Rate Limiting</dfn>
:: The process (also known as throttling) by which an authenticator implements controls against brute force attacks by limiting
the number of consecutive failed authentication attempts within a given period of time. If the limit is reached, the
authenticator should impose a delay that increases exponentially with each successive attempt, or disable the current
authentication modality and offer a different authentication factor if available. Rate limiting is often implemented as an
aspect of [=user verification=].
: <dfn>Registration</dfn>
:: The [=ceremony=] where a user, a [=[RP]=], and the user's computing device(s) (containing at least one
[=authenticator=]) work in concert to create a [=public key credential=] and associate it with the user's [=[RP]=] account.
Note that this includes employing a [=test of user presence=] or [=user verification=].
: <dfn>[RP]</dfn>
:: The entity whose web application utilizes the [=Web Authentication API=] to register and authenticate users. See
[=Registration=] and [=Authentication=], respectively.
Note: While the term [=[RP]=] is used in other contexts (e.g., X.509 and OAuth), an entity acting as a [=[RP]=] in one
context is not necessarily a [=[RP]=] in other contexts.
: <dfn>Relying Party Identifier</dfn>
: <dfn>RP ID</dfn>
:: A [=valid domain string=] that identifies the [=[RP]=] on whose behalf a given [=registration=] or
[=authentication|authentication ceremony=] is being performed. A [=public key credential=] can only be used for
[=authentication=] with the same entity (as identified by [=RP ID=]) it was registered with. By default, the [=RP ID=] for a
WebAuthn operation is set to the caller's [=environment settings object/origin=]'s [=effective domain=]. This default MAY be
overridden by the caller, as long as the caller-specified [=RP ID=] value [=is a registrable domain suffix of or is equal
to=] the caller's [=environment settings object/origin=]'s [=effective domain=]. See also [[#createCredential]] and
[[#getAssertion]].
<div class="note" id="note-pkcredscope">
Note: A [=Public key credential=]'s scope is for a [=[RP]=]'s [=origin=], with the following <em>restrictions</em> and
<em>relaxations</em>:
- The scheme is always `https` (i.e., <em>a restriction</em>), and,
- the host may be equal to the [=[RP]=]'s [=origin=]'s [=effective domain=], or it may be equal to a registrable
domain suffix of the [=[RP]=]'s [=origin=]'s [=effective domain=] (i.e., <em>an available relaxation</em>), and,
- all (TCP) ports on that host (i.e., <em>a relaxation</em>).
This is done in order to match the behavior of pervasively deployed ambient credentials (e.g., cookies, [[RFC6265]]).
Please note that this is a greater relaxation of "same-origin" restrictions than what
[=document.domain=]'s setter provides.
</div>
: <dfn>Test of User Presence</dfn>
:: A [=test of user presence=] is a simple form of [=authorization gesture=] and technical process where a user interacts with
an [=authenticator=] by (typically) simply touching it (other modalities may also exist), yielding a boolean result. Note
that this does not constitute [=user verification=] because a [=test of user presence|user presence test=], by definition,
is not capable of [=biometric recognition=], nor does it involve the presentation of a shared secret such as a password or
PIN.
: <dfn>User Consent</dfn>
:: User consent means the user agrees with what they are being asked, i.e., it encompasses reading and understanding prompts.
An [=authorization gesture=] is a [=ceremony=] component often employed to indicate [=user consent=].
: <dfn>User Handle</dfn>
:: The user handle is specified by a [=[RP]=] and is a unique identifier for a user account with that [=[RP]=]. A user handle is
an opaque [=byte sequence=] with a maximum size of 64 bytes.
The user handle is not meant to be displayed to the user, but is used by the [=[RP]=] to control the number of credentials - an
authenticator will never contain more than one credential for a given [=[RP]=] under the same user handle.
: <dfn>User Verification</dfn>
:: The technical process by which an [=authenticator=] <em>locally authorizes</em> the invocation of the
[=authenticatorMakeCredential=] and [=authenticatorGetAssertion=] operations. [=User verification=] may be instigated
through various [=authorization gesture=] modalities; for example, through a touch plus pin code, password entry, or
[=biometric recognition=] (e.g., presenting a fingerprint) [[ISOBiometricVocabulary]]. The intent is to be able to
distinguish individual users. Note that invocation of the [=authenticatorMakeCredential=] and [=authenticatorGetAssertion=]
operations implies use of key material managed by the authenticator. Note that for security, [=user verification=] and use
of [=credential private keys=] must occur within a single logical security boundary defining the [=authenticator=].
: <dfn id=concept-user-present>User Present</dfn>
: <dfn>UP</dfn>
:: Upon successful completion of a [=test of user presence|user presence test=], the user is said to be
"[=user present|present=]".
: <dfn id=concept-user-verified>User Verified</dfn>
: <dfn>UV</dfn>
:: Upon successful completion of a [=user verification=] process, the user is said to be "[=user verified|verified=]".
: <dfn>[WAC]</dfn>
:: Also referred to herein as simply a [=client=]. See also [=Conforming User Agent=].
# <dfn>Web Authentication API</dfn> # {#api}
This section normatively specifies the API for creating and using [=public key credentials=]. The basic
idea is that the credentials belong to the user and are managed by an authenticator, with which the [=[RP]=] interacts through the
client (consisting of the browser and underlying OS platform). Scripts can (with the [=user consent|user's consent=]) request the
browser to create a new credential for future use by the [=[RP]=]. Scripts can also request the user’s permission to perform
authentication operations with an existing credential. All such operations are performed in the authenticator and are mediated by
the browser and/or platform on the user's behalf. At no point does the script get access to the credentials themselves; it only
gets information about the credentials in the form of objects.
In addition to the above script interface, the authenticator may implement (or come with client software that implements) a user
interface for management. Such an interface may be used, for example, to reset the authenticator to a clean state or to inspect
the current state of the authenticator. In other words, such an interface is similar to the user interfaces provided by browsers
for managing user state such as history, saved passwords and cookies. Authenticator management actions such as credential
deletion are considered to be the responsibility of such a user interface and are deliberately omitted from the API exposed to
scripts.
The security properties of this API are provided by the client and the authenticator working together. The authenticator, which
holds and manages credentials, ensures that all operations are scoped to a particular [=origin=], and cannot be replayed against
a different [=origin=], by incorporating the [=origin=] in its responses. Specifically, as defined in [[#authenticator-ops]],
the full [=origin=] of the requester is included, and signed over, in the [=attestation object=] produced when a new credential
is created as well as in all assertions produced by WebAuthn credentials.
Additionally, to maintain user privacy and prevent malicious [=[RPS]=] from probing for the presence of [=public key
credentials=] belonging to other [=[RPS]=], each [=public key credential|credential=] is also associated with a [=Relying Party
Identifier=], or [=RP ID=]. This [=RP ID=] is provided by the client to the [=authenticator=] for all operations, and the
[=authenticator=] ensures that [=public key credential|credentials=] created by a [=[RP]=] can only be used in operations
requested by the same [=RP ID=]. Separating the [=origin=] from the [=RP ID=] in this way allows the API to be used in cases
where a single [=[RP]=] maintains multiple [=origins=].
The client facilitates these security measures by providing the [=[RP]=]'s [=origin=] and [=RP ID=] to the [=authenticator=] for
each operation. Since this is an integral part of the WebAuthn security model, user agents only expose this API to callers in
[=secure contexts=].
The Web Authentication API is defined by the union of the Web IDL fragments presented in the following sections. A combined IDL
listing is given in the [[#idl-index]].
## <dfn interface>PublicKeyCredential</dfn> Interface ## {#iface-pkcredential}
The {{PublicKeyCredential}} interface inherits from {{Credential}} [[!CREDENTIAL-MANAGEMENT-1]], and contains the attributes
that are returned to the caller when a new credential is created, or a new assertion is requested.
<xmp class="idl">
[SecureContext, Exposed=Window]
interface PublicKeyCredential : Credential {
[SameObject] readonly attribute ArrayBuffer rawId;
[SameObject] readonly attribute AuthenticatorResponse response;
AuthenticationExtensions getClientExtensionResults();
};
</xmp>
<dl dfn-type="attribute" dfn-for="PublicKeyCredential">
: {{Credential/id}}
:: This attribute is inherited from {{Credential}}, though {{PublicKeyCredential}} overrides {{Credential}}'s getter,
instead returning the [=base64url encoding=] of the data contained in the object's
{{PublicKeyCredential/[[identifier]]}} [=internal slot=].
: {{PublicKeyCredential/rawId}}
:: This attribute returns the {{ArrayBuffer}} contained in the {{PublicKeyCredential/[[identifier]]}} internal slot.
: <dfn>response</dfn>
:: This attribute contains the [=authenticator=]'s response to the client's request to either create a [=public key
credential=], or generate an [=authentication assertion=]. If the {{PublicKeyCredential}} is created in response to
{{CredentialsContainer/create()}}, this attribute's value will be an {{AuthenticatorAttestationResponse}}, otherwise,
the {{PublicKeyCredential}} was created in response to {{CredentialsContainer/get()}}, and this attribute's value
will be an {{AuthenticatorAssertionResponse}}.
: {{PublicKeyCredential/getClientExtensionResults()}}
:: This operation returns the value of {{PublicKeyCredential/[[clientExtensionsResults]]}}, which is a [=map=] containing
[=extension identifier=] → [=client extension output=] entries produced by the extension's
[=client extension processing=].
: <dfn>\[[type]]</dfn>
:: The {{PublicKeyCredential}} [=interface object=]'s {{Credential/[[type]]}} [=internal slot=]'s value is the string
"`public-key`".
Note: This is reflected via the {{Credential/type}} attribute getter inherited from {{Credential}}.
: <dfn>\[[discovery]]</dfn>
:: The {{PublicKeyCredential}} [=interface object=]'s {{Credential/[[discovery]]}} [=internal slot=]'s value is
"{{Credential/[[discovery]]/remote}}".
: <dfn>\[[identifier]]</dfn>
:: This [=internal slot=] contains an identifier for the credential, chosen by the platform with help from the
authenticator. This identifier is used to look up credentials for use, and is therefore expected to be globally unique
with high probability across all credentials of the same type, across all authenticators. This API does not constrain
the format or length of this identifier, except that it must be sufficient for the platform to uniquely select a key.
For example, an authenticator without on-board storage may create identifiers containing a [=credential private key=]
wrapped with a symmetric key that is burned into the authenticator.
: <dfn>\[[clientExtensionsResults]]</dfn>
:: This [=internal slot=] contains the results of processing client extensions requested by the [=[RP]=] upon the
[=[RP]=]'s invocation of either {{CredentialsContainer/create()|navigator.credentials.create()}} or
{{CredentialsContainer/get()|navigator.credentials.get()}}.
</dl>
{{PublicKeyCredential}}'s [=interface object=] inherits {{Credential}}'s implementation of
{{Credential/[[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors)}}, and defines its own
implementation of {{PublicKeyCredential/[[Create]](origin, options, sameOriginWithAncestors)}}, {{PublicKeyCredential/[[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors)}}, and
{{Credential/[[Store]](credential, sameOriginWithAncestors)}}.
### `CredentialCreationOptions` Extension ### {#credentialcreationoptions-extension}
To support registration via {{CredentialsContainer/create()|navigator.credentials.create()}}, this document extends
the {{CredentialCreationOptions}} dictionary as follows:
<pre class="idl">
partial dictionary CredentialCreationOptions {
MakePublicKeyCredentialOptions publicKey;
};
</pre>
### `CredentialRequestOptions` Extension ### {#credentialrequestoptions-extension}
To support obtaining assertions via {{CredentialsContainer/get()|navigator.credentials.get()}}, this document extends the
{{CredentialRequestOptions}} dictionary as follows:
<pre class="idl">
partial dictionary CredentialRequestOptions {
PublicKeyCredentialRequestOptions publicKey;
};
</pre>
### Create a new credential - PublicKeyCredential's `[[Create]](origin, options, sameOriginWithAncestors)` method ### {#createCredential}
<div link-for-hint="PublicKeyCredential/[[Create]](origin, options, sameOriginWithAncestors)">
{{PublicKeyCredential}}'s [=interface object=]'s implementation of the
<dfn for="PublicKeyCredential" method>\[[Create]](origin, options, sameOriginWithAncestors)</dfn> [=internal method=] [[CREDENTIAL-MANAGEMENT-1]] allows
[=[RP]=] scripts to call {{CredentialsContainer/create()|navigator.credentials.create()}} to request the creation of a new
[=public key credential source=], bound to an [=authenticator=]. This
{{CredentialsContainer/create()|navigator.credentials.create()}} operation can be aborted by leveraging the {{AbortController}};
see [[dom#abortcontroller-api-integration]] for detailed instructions.
This [=internal method=] accepts three arguments:
<dl dfn-type="argument" dfn-for="PublicKeyCredential/[[Create]](origin, options, sameOriginWithAncestors)">
: <dfn>origin</dfn>
:: This argument is the [=relevant settings object=]'s [=environment settings object/origin=], as determined by the
calling {{CredentialsContainer/create()}} implementation.
: <dfn>options</dfn>
:: This argument is a {{CredentialCreationOptions}} object whose
<code>|options|.{{CredentialCreationOptions/publicKey}}</code> member contains a {{MakePublicKeyCredentialOptions}}
object specifying the desired attributes of the to-be-created [=public key credential=].
: <dfn>sameOriginWithAncestors</dfn>
:: This argument is a boolean which is true if and only if the caller's [=environment settings object=] is
[=same-origin with its ancestors=].
</dl>
Note: <strong>This algorithm is synchronous:</strong> the {{Promise}} resolution/rejection is handled by
{{CredentialsContainer/create()|navigator.credentials.create()}}.
When this method is invoked, the user agent MUST execute the following algorithm:
1. Assert: <code>|options|.{{CredentialCreationOptions/publicKey}}</code> is [=present=].
1. If <var ignore>sameOriginWithAncestors</var> is `false`, return a "{{NotAllowedError}}" {{DOMException}}.
Note: This "sameOriginWithAncestors" restriction aims to address the concern raised in the
[[CREDENTIAL-MANAGEMENT-1#security-origin-confusion|Origin Confusion]] section of [[CREDENTIAL-MANAGEMENT-1]],
while allowing [=[RP]=] script access to Web Authentication functionality, e.g., when running in
a [=secure context=] framed document that is [=same-origin with its ancestors=].
However, in the future, this specification (in conjunction with
[[CREDENTIAL-MANAGEMENT-1]]) may provide [=[RPS]=] with more fine-grained control--e.g., ranging
from allowing only top-level access to Web Authentication functionality,
to allowing cross-origin embedded cases--by leveraging
[[Feature-Policy]] once the latter specification becomes stably implemented in user agents.
1. Let |options| be the value of <code>|options|.{{CredentialCreationOptions/publicKey}}</code>.
1. If the {{MakePublicKeyCredentialOptions/timeout}} member of |options| is [=present=], check if its value lies within a
reasonable range as defined by the platform and if not, correct it to the closest value lying within that range. Set a timer
|lifetimeTimer| to this adjusted value. If the {{MakePublicKeyCredentialOptions/timeout}} member of |options| is [=present|not
present=], then set |lifetimeTimer| to a platform-specific default.
1. Let |callerOrigin| be {{PublicKeyCredential/[[Create]](origin, options, sameOriginWithAncestors)/origin}}. If |callerOrigin| is an [=opaque origin=], return a {{DOMException}} whose name is
"{{NotAllowedError}}", and terminate this algorithm.
1. Let |effectiveDomain| be the |callerOrigin|'s [=effective domain=].
If [=effective domain=] is not a [=valid domain=], then return a
{{DOMException}} whose name is "{{SecurityError}}" and terminate this algorithm.
Note: An [=effective domain=] may resolve to a [=host=], which can be represented in various manners,
such as [=domain=], [=ipv4 address=], [=ipv6 address=], [=opaque host=], or [=empty host=].
Only the [=domain=] format of [=host=] is allowed here.
<!-- Note: this next step is actually a top-level step, but bikeshed wanted it indented this much in order to compile w/o errors
-->
<li id='CreateCred-DetermineRpId'>
If <code>|options|.{{MakePublicKeyCredentialOptions/rp}}.{{PublicKeyCredentialEntity/id}}</code>
<dl class="switch">
: Is [=present=]
:: If <code>|options|.{{MakePublicKeyCredentialOptions/rp}}.{{PublicKeyCredentialEntity/id}}</code> [=is not a
registrable domain suffix of and is not equal to=] |effectiveDomain|, return a {{DOMException}} whose name
is "{{SecurityError}}", and terminate this algorithm.
: Is [=present|not present=]
:: Set <code>|options|.{{MakePublicKeyCredentialOptions/rp}}.{{PublicKeyCredentialEntity/id}}</code> to
|effectiveDomain|.
</dl>
Note: <code>|options|.{{MakePublicKeyCredentialOptions/rp}}.{{PublicKeyCredentialEntity/id}}</code> represents the
caller's [=RP ID=]. The [=RP ID=] defaults to being the caller's [=environment settings object/origin=]'s
[=effective domain=] unless the caller has explicitly set
<code>|options|.{{MakePublicKeyCredentialOptions/rp}}.{{PublicKeyCredentialEntity/id}}</code> when calling
{{CredentialsContainer/create()}}.
</li>
1. Let |credTypesAndPubKeyAlgs| be a new [=list=] whose [=list/items=] are pairs of {{PublicKeyCredentialType}} and
a {{COSEAlgorithmIdentifier}}.
1. [=list/For each=] |current| of <code>|options|.{{MakePublicKeyCredentialOptions/pubKeyCredParams}}</code>:
1. If <code>|current|.{{PublicKeyCredentialParameters/type}}</code> does not contain a {{PublicKeyCredentialType}} supported
by this implementation, then [=continue=].
1. Let |alg| be <code>|current|.{{PublicKeyCredentialParameters/alg}}</code>.
1. [=list/Append=] the pair of <code>|current|.{{PublicKeyCredentialParameters/type}}</code> and |alg| to
|credTypesAndPubKeyAlgs|.
1. If |credTypesAndPubKeyAlgs| [=list/is empty=] and <code>|options|.{{MakePublicKeyCredentialOptions/pubKeyCredParams}}</code>
[=list/is not empty=], return a {{DOMException}} whose name is "{{NotSupportedError}}", and terminate this algorithm.
1. Let |clientExtensions| be a new [=map=] and let |authenticatorExtensions| be a new [=map=].
1. If the {{MakePublicKeyCredentialOptions/extensions}} member of |options| is [=present=], then [=map/for each=]
|extensionId| → |clientExtensionInput| of <code>|options|.{{MakePublicKeyCredentialOptions/extensions}}</code>:
1. If |extensionId| is not supported by this client platform or is not a [=registration extension=], then [=continue=].
1. [=map/Set=] |clientExtensions|[|extensionId|] to |clientExtensionInput|.
1. If |extensionId| is not an [=authenticator extension=], then [=continue=].
1. Let |authenticatorExtensionInput| be the ([=CBOR=]) result of running |extensionId|'s [=client extension processing=]
algorithm on |clientExtensionInput|. If the algorithm returned an error, [=continue=].
1. [=map/Set=] |authenticatorExtensions|[|extensionId|] to the [=base64url encoding=] of |authenticatorExtensionInput|.
1. Let |collectedClientData| be a new {{CollectedClientData}} instance whose fields are:
: {{CollectedClientData/type}}
:: The string "webauthn.create".
: {{CollectedClientData/challenge}}
:: The [=base64url encoding=] of |options|.{{MakePublicKeyCredentialOptions/challenge}}.
: {{CollectedClientData/origin}}
:: The [=ascii serialization of an origin|serialization of=] |callerOrigin|.
: {{CollectedClientData/hashAlgorithm}}
:: The [=recognized algorithm name=] of the hash algorithm selected by the client for generating the
[=hash of the serialized client data=].
: {{CollectedClientData/tokenBindingId}}
:: The [=Token Binding ID=] associated with |callerOrigin|, if one is available.
: {{CollectedClientData/clientExtensions}}
:: |clientExtensions|
: {{CollectedClientData/authenticatorExtensions}}
:: |authenticatorExtensions|
1. Let |clientDataJSON| be the [=JSON-serialized client data=] constructed from |collectedClientData|.
1. Let |clientDataHash| be the [=hash of the serialized client data=] represented by |clientDataJSON|.
1. If the <code>|options|.{{CredentialCreationOptions/signal}}</code> is [=present=] and its
[=AbortSignal/aborted flag=] is set to true, return a {{DOMException}} whose name is "{{AbortError}}"
and terminate this algorithm.
1. Start |lifetimeTimer|.
1. Let |issuedRequests| be a new [=ordered set=].
1. [=set/For each=] |authenticator| that becomes available on this platform during the lifetime of |lifetimeTimer|, do the
following:
Issue: The definitions of "lifetime of" and "becomes available" are intended to represent how
devices are hotplugged into (USB) or discovered by (NFC) browsers, and are under-specified.
Resolving this with good definitions or some other means will be addressed by resolving
[Issue #613](https://github.com/w3c/webauthn/issues/613).
1. If <code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}</code> is [=present=]:
1. If <code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}.{{authenticatorAttachment}}</code> is
[=present|present=] and its value is not equal to |authenticator|'s attachment modality, [=iteration/continue=].
1. If <code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}.{{requireResidentKey}}</code> is set to
`true` and the |authenticator| is not capable of storing a [=Client-Side-Resident Credential Private Key=],
[=iteration/continue=].
1. If <code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}.{{AuthenticatorSelectionCriteria/userVerification}}</code> is
set to {{UserVerificationRequirement/required}} and the |authenticator| is not capable of performing [=user
verification=], [=iteration/continue=].
1. Let |userVerification| be the <dfn>effective user verification requirement for credential creation</dfn>, a Boolean value,
as follows. If
<code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}.{{AuthenticatorSelectionCriteria/userVerification}}</code>
<dl class="switch">
: is set to {{UserVerificationRequirement/required}}
:: Let |userVerification| be `true`.
: is set to {{UserVerificationRequirement/preferred}}
:: If the |authenticator|
<dl class="switch">
: is capable of [=user verification=]
:: Let |userVerification| be `true`.
: is not capable of [=user verification=]
:: Let |userVerification| be `false`.
</dl>
: is set to {{UserVerificationRequirement/discouraged}}
:: Let |userVerification| be `false`.
</dl>
1. Let |userPresence| be a Boolean value set to the inverse of |userVerification|.
1. Let |excludeCredentialDescriptorList| be a new [=list=].
1. [=list/For each=] credential descriptor |C| in <code>|options|.{{MakePublicKeyCredentialOptions/excludeCredentials}}</code>:
1. If <code>|C|.{{transports}}</code> [=list/is not empty=], and |authenticator| is connected over a transport not
mentioned in <code>|C|.{{transports}}</code>, the client MAY [=continue=].
1. Otherwise, [=list/Append=] |C| to |excludeCredentialDescriptorList|.
<!-- @@EDITOR-ANCHOR-01A: KEEP THIS LIST SYNC'D WITH THE LIST UP AT @@EDITOR-ANCHOR-01B -->
1. Invoke the [=authenticatorMakeCredential=] operation on |authenticator| with
|clientDataHash|,
<code>|options|.{{MakePublicKeyCredentialOptions/rp}}</code>, <code>|options|.{{MakePublicKeyCredentialOptions/user}}</code>,
<code>|options|.{{MakePublicKeyCredentialOptions/authenticatorSelection}}.{{AuthenticatorSelectionCriteria/requireResidentKey}}</code>,
|userPresence|,
|userVerification|,
|credTypesAndPubKeyAlgs|,
|excludeCredentialDescriptorList|,
and |authenticatorExtensions| as parameters.
1. [=set/Append=] |authenticator| to |issuedRequests|.
1. [=While=] |issuedRequests| [=list/is not empty=], perform the following actions depending upon
|lifetimeTimer| and responses from the authenticators:
<dl class="switch">
: If |lifetimeTimer| expires,
:: [=set/For each=] |authenticator| in |issuedRequests| invoke the [=authenticatorCancel=] operation on |authenticator|
and [=set/remove=] |authenticator| from |issuedRequests|.
: If the <code>|options|.{{CredentialCreationOptions/signal}}</code> is [=present=] and its
[=AbortSignal/aborted flag=] is set to true,
:: [=set/For each=] |authenticator| in |issuedRequests| invoke the [=authenticatorCancel=]
operation on |authenticator| and [=set/remove=] |authenticator| from |issuedRequests|. Then return a {{DOMException}}
whose name is "{{AbortError}}" and terminate this algorithm.
: If any |authenticator| returns a status indicating that the user cancelled the operation,
:: 1. [=set/Remove=] |authenticator| from |issuedRequests|.
2. [=set/For each=] remaining |authenticator| in |issuedRequests| invoke the [=authenticatorCancel=] operation on
|authenticator| and [=set/remove=] it from |issuedRequests|.
: If any |authenticator| returns an error status,
:: [=set/Remove=] |authenticator| from |issuedRequests|.
: If any |authenticator| indicates success,
:: 1. [=set/Remove=] |authenticator| from |issuedRequests|.
1. Let |credentialCreationData| be a [=struct=] whose [=items=] are:
: <code><dfn for="credentialCreationData">attestationObjectResult</dfn></code>
:: whose value is the bytes returned from the successful [=authenticatorMakeCredential=] operation.
Note: this value is <code>attObj</code>, as defined in [[#generating-an-attestation-object]].
: <code><dfn for="credentialCreationData">clientDataJSONResult</dfn></code>
:: whose value is the bytes of |clientDataJSON|.
: <code><dfn for="credentialCreationData">attestationConveyancePreferenceOption</dfn></code>
:: whose value is the value of |options|.{{MakePublicKeyCredentialOptions/attestation}}.
: <code><dfn for="credentialCreationData">clientExtensionResults</dfn></code>
:: whose value is an {{AuthenticationExtensions}} object containing [=extension identifier=] →
[=client extension output=] entries. The entries are created by running each extension's
[=client extension processing=] algorithm to create the [=client extension outputs=], for each
[=client extension=] in <code>{{AuthenticatorResponse/clientDataJSON}}.clientExtensions</code>.
1. Let |constructCredentialAlg| be an algorithm that takes a [=global object=]
|global|, and whose steps are:
1. Let |attestationObject| be a new {{ArrayBuffer}}, created using |global|'s [=%ArrayBuffer%=], containing the
bytes of <code>|credentialCreationData|.[=attestationObjectResult=]</code>'s value.
1. If <code>|credentialCreationData|.[=attestationConveyancePreferenceOption=]</code>'s value is
<dl class="switch">
: "none"
:: Replace potentially uniquely identifying information (such as [=AAGUID=] and
[=attestation certificates=]) in the [=attested credential data=] and [=attestation statement=],
respectively, with blinded versions of the same data.
Issue(w3c/webauthn#694): need to define "blinding". See also
[#462](https://github.com/w3c/webauthn/issues/462).
: "indirect"
:: The client MAY replace the [=AAGUID=] and [=attestation statement=] with a more privacy-friendly
and/or more easily verifiable version of the same data (for example, by employing a [=Privacy CA=]).
: "direct"
:: Convey the [=authenticator=]'s [=AAGUID=] and [=attestation statement=], unaltered, to the RP.
Issue: @balfanz wishes to add to the "direct" case:
If the [=authenticator=] violates the privacy requirements of the [=attestation type=] it is using,
the client SHOULD terminate this algorithm with a "AttestationNotPrivateError".
</dl>
1. Let |id| be <code>|attestationObject|.authData.[=attestedCredentialData=].[=credentialId=]</code>.
1. Let |pubKeyCred| be a new {{PublicKeyCredential}} object associated with |global| whose fields are:
: {{PublicKeyCredential/[[identifier]]}}
:: |id|
: {{PublicKeyCredential/response}}
:: A new {{AuthenticatorAttestationResponse}} object associated with |global| whose fields are:
: {{AuthenticatorResponse/clientDataJSON}}
:: A new {{ArrayBuffer}}, created using |global|'s [=%ArrayBuffer%=], containing the bytes of
<code>|credentialCreationData|.[=credentialCreationData/clientDataJSONResult=]</code>.
: {{AuthenticatorAttestationResponse/attestationObject}}
:: |attestationObject|
: {{PublicKeyCredential/[[clientExtensionsResults]]}}
:: A new {{ArrayBuffer}}, created using |global|'s [=%ArrayBuffer%=], containing the bytes of
<code>|credentialCreationData|.[=credentialCreationData/clientExtensionResults=]</code>.
1. Return |pubKeyCred|.
1. [=set/For each=] remaining |authenticator| in |issuedRequests| invoke the [=authenticatorCancel=] operation on
|authenticator| and [=set/remove=] it from |issuedRequests|.
1. Return |constructCredentialAlg| and terminate this algorithm.
</dl>
1. Return a {{DOMException}} whose name is "{{NotAllowedError}}".
During the above process, the user agent SHOULD show some UI to the user to guide them in the process of selecting and
authorizing an authenticator.
</div>
### Use an existing credential to make an assertion - PublicKeyCredential's `[[Get]](options)` method ### {#getAssertion}
[=[RPS]=] call <code><a idl for="CredentialsContainer" lt="get()">navigator.credentials.get({publicKey:..., ...})</a></code> to
discover and use an existing [=public key credential=], with the [=user consent|user's consent=]. [=[RP]=] script optionally specifies some criteria
to indicate what [=credential sources=] are acceptable to it. The user agent and/or platform locates [=credential sources=]
matching the specified criteria, and guides the user to pick one that the script will be allowed to use. The user may choose to
decline the entire interaction even if a [=credential source=] is present, for example to maintain privacy. If the user picks a
[=credential source=], the user agent then uses
[[#op-get-assertion]] to sign a [RP]-provided challenge and other collected data into an assertion, which is used as a
[=credential=].
The {{CredentialsContainer/get()}} implementation [[CREDENTIAL-MANAGEMENT-1]] calls
<code>PublicKeyCredential.{{PublicKeyCredential/[[CollectFromCredentialStore]]()}}</code> to collect any [=credentials=] that
should be available without [=user mediation=] (roughly, this specification's [=authorization gesture=]), and if it does not find
exactly one of those, it then calls <code>PublicKeyCredential.{{PublicKeyCredential/[[DiscoverFromExternalSource]]()}}</code> to have
the user select a [=credential source=].
Since this specification requires an [=authorization gesture=] to create any [=credentials=], the <code>PublicKeyCredential.<dfn
for="PublicKeyCredential" method>\[[CollectFromCredentialStore]](origin, options, sameOriginWithAncestors)</dfn></code> [=internal method=] inherits the default behavior of
{{Credential/[[CollectFromCredentialStore]]()|Credential.[[CollectFromCredentialStore]]()}}, of returning an empty set.
<h5 id="discover-from-external-source" algorithm>PublicKeyCredential's <code><dfn for="PublicKeyCredential" method>\[[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors)</dfn></code> method</h5>
<div link-for-hint="PublicKeyCredential/[[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors)">
This [=internal method=] accepts three arguments:
<dl dfn-type="argument" dfn-for="PublicKeyCredential/[[DiscoverFromExternalSource]](origin, options, sameOriginWithAncestors)">
: <dfn>origin</dfn>
:: This argument is the [=relevant settings object=]'s [=environment settings object/origin=], as determined by the
calling {{CredentialsContainer/get()}} implementation, i.e., {{CredentialsContainer}}'s <a abstract-op>Request a `Credential`</a> abstract operation.
: <dfn>options</dfn>
:: This argument is a {{CredentialRequestOptions}} object whose
<code>|options|.{{CredentialRequestOptions/publicKey}}</code> member contains a {{PublicKeyCredentialRequestOptions}}
object specifying the desired attributes of the [=public key credential=] to discover.