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<pre class="metadata">
Title: Secure Payment Confirmation
Shortname: secure-payment-confirmation
Repository: w3c/secure-payment-confirmation
TR: https://www.w3.org/TR/secure-payment-confirmation/
ED: https://w3c.github.io/secure-payment-confirmation/
Prepare for TR: true
Inline Github Issues: true
Group: web-payments
Status: w3c/ED
Deadline: 2023-08-01
Level:
URL: https://w3c.github.io/secure-payment-confirmation/
Editor: Rouslan Solomakhin, w3cid 83784, Google https://www.google.com/, rouslan@chromium.org
Editor: Stephen McGruer, w3cid 96463, Google https://www.google.com/, smcgruer@chromium.org
!Contributors: <a href="mailto:ij@w3.org">Ian Jacobs</a> (<a href="https://w3.org">W3C</a>)
!Contributors: <a href="mailto:nburris@chromium.org">Nick Burris</a> (<a href="https://www.google.com">Google</a>)
Abstract: Secure Payment Confirmation (SPC) is a Web API to support streamlined
authentication during a payment transaction. It is designed to scale authentication
across merchants, to be used within a wide range of authentication protocols, and
to produce cryptographic evidence that the user has confirmed transaction details.
Complain About: missing-example-ids true
Local Boilerplate: status yes
Markup Shorthands: markdown yes
WPT Display: closed
WPT Path Prefix: /secure-payment-confirmation/
Implementation Report: https://wpt.fyi/results/secure-payment-confirmation
</pre>
<pre class="anchors">
spec: credential-management-1; urlPrefix: https://w3c.github.io/webappsec-credential-management/
type: dfn
text: same-origin with its ancestors; url: same-origin-with-its-ancestors
text: request a credential; url: abstract-opdef-request-a-credential
spec: ECMAScript; urlPrefix: https://tc39.github.io/ecma262/#
type: dfn
url: sec-object-internal-methods-and-internal-slots
text: internal slot
text: internal method
spec: i18n-glossary; urlPrefix: https://www.w3.org/TR/i18n-glossary/
type: dfn
text: locale; url: dfn-locale
spec: payment-request; urlPrefix: https://w3c.github.io/payment-request/
type: dfn
text: payment method; url: dfn-payment-method
text: payment method additional data type; url: dfn-additional-data-type
text: payment request details; url: dfn-details
text: steps to validate payment method data; url: dfn-steps-to-validate-payment-method-data
text: steps to check if a payment can be made; url: dfn-steps-to-check-if-a-payment-can-be-made
text: steps to respond to a payment request; url: dfn-steps-to-respond-to-a-payment-request
text: payment permission string; url: dfn-payment
text: payment request accessibility considerations; url: accessibility-considerations
spec: payment-method-id; urlPrefix: https://w3c.github.io/payment-method-id/
type: dfn
text: registry of standardized payment methods; url: registry
spec: web-authn; urlPrefix: https://w3c.github.io/webauthn/
type: dfn
text: authentication ceremony; url: authentication-ceremony
text: credential ID; url: credential-id
text: discoverable credential; url: discoverable-credential
text: relying party; url: relying-party
text: relying party identifier; url: relying-party-identifier
text: public key credential; url: public-key-credential
text: WebAuthn Extension; url: webauthn-extensions
text: client extension; url: client-extension
text: registration extension; url: registration-extension
text: authentication extension; url: authentication-extension
text: extension identifier; url: extension-identifier
text: user member; url: dom-publickeycredentialcreationoptions-user
spec: webdriver; urlPrefix: https://w3c.github.io/webdriver/
type: dfn
text: extension command; url: dfn-extension-commands
text: getting a property; url: dfn-getting-properties
text: invalid argument; url: dfn-invalid-argument
text: remote end steps; url: dfn-remote-end-steps
text: success; url: dfn-success
text: undefined; url: dfn-undefined
text: WebDriver error; url: dfn-error
text: WebDriver error code; url: dfn-error-code
</pre>
<pre class="link-defaults">
spec:fetch; type:dfn; for:/; text:request;
spec:i18n-glossary; type:dfn; text:bidi isolation
spec:i18n-glossary; type:dfn; text:language priority list
spec:url; type:dfn; text:valid domain;
spec:html; type:dfn; for:environment settings object; text:origin
</pre>
<pre class="biblio">
{
"webauthn-conditional-ui": {
"title": "WebAuthn Conditional UI Proposal",
"href": "https://github.com/w3c/webauthn/issues/1545"
},
"IANA-WebAuthn-Registries": {
"title": "Registries for Web Authentication (WebAuthn)",
"href": "https://www.rfc-editor.org/rfc/rfc8809.html"
}
}
</pre>
<div class="non-normative">
# Introduction # {#sctn-intro}
*This section and its sub-sections are non-normative.*
This specification defines an API that enables the use of strong authentication
methods in payment flows on the web. It aims to provide the same authentication
benefits and user privacy focus as [[webauthn-3]] with enhancements to meet the
needs of payment processing.
Similarly to [[webauthn-3]], this specification defines two related processes
involving a user. The first is [[#sctn-registration]] (formerly "enrollment"),
where a relationship is created between the user and the [=Relying Party=]. The
second is [[#sctn-authentication]], where the user responds to a challenge from
the [=Relying Party=] (possibly via an intermediary payment service provider)
to consent to a specific payment.
It is a goal of this specification to reduce authentication friction during
checkout, and one aspect of that is to maximize the number of authentications
that the user can perform for a given registration. That is, with consent
from the [=Relying Party=], ideally the user could "register once" and
authenticate on any merchant origin (and via payment service provider),
not just the merchant origin where the user first registered.
To that end, an important feature of Secure Payment Confirmation is
that the merchant (or another entity) may initiate the authentication
ceremony on the [=Relying Party's=] behalf. The [=Relying Party=] must
opt-in to allowing this behavior during credential creation.
Functionally, this specification defines a new [=payment method=] for the
{{PaymentRequest}} API, and adds a [=WebAuthn Extension=] to extend
[[webauthn-3]] with payment-specific datastructures and to relax assumptions to
allow the API to be called in payment contexts.
## Use Cases ## {#sctn-use-cases}
Although [[webauthn-3]] provides general authentication capabilities for the
Web, the following use cases illustrate the value of the payment-specific
extension defined in this specification.
We presume that the general use case of cryptographic-based authentication for
online transactions is well established.
### Cryptographic evidence of transaction confirmation ### {#sctn-use-case-verifying-payment}
In many online payment systems, it is common for the entity (e.g., bank) that
issues a payment instrument to seek to reduce fraud through authentication.
[[webauthn-3]] and this specification make it possible to use authenticators to
cryptographically sign important payment-specific information such as the
origin of the merchant and the transaction amount and currency. The bank, as
the [=Relying Party=], can then verify the signed payment-specific information
as part of the decision to authorize the payment.
If the bank uses plain [[webauthn-3]], the payment-specific information to be
verified must be stored in the WebAuthn
{{PublicKeyCredentialRequestOptions/challenge}}. This raises several issues:
1. It is a misuse of the `challenge` field (which is intended to defeat replay
attacks).
1. There is no specification for this, so each bank is likely to have
to devise its own format for how payment-specific information should be
formatted and encoded in the challenge, complicating deployment and
increasing fragmentation.
1. Regulations may require evidence that the user was shown and agreed to the
payment-specific information. Plain [[webauthn-3]] does not provide for
this display: there is no specified UX associated with information stored
in the `challenge` field.
These limitations motivate the following Secure Payment Confirmation behaviors:
1. The `challenge` field is only used to defeat replay attacks, as with plain
[[webauthn-3]].
1. SPC specifies a format for payment-specific information. This will enable
development of generic verification code and test suites.
1. SPC guarantees that the user agent has presented the payment-specific
information to the user in a way that a malicious website (or maliciously
introduced JavaScript code on a trusted website) cannot bypass.
* The payment-specific information is included in the
{{CollectedClientData}} dictionary, which cannot be tampered with via
JavaScript.
NOTE: Banks and other stakeholders in the payments ecosystem trust payments
via browsers sufficiently today using TLS, iframes, and other Web features.
The current specification is designed to increase the security and usability
of Web payments.
### Registration in a third-party iframe ### {#sctn-use-case-iframe-registration}
If a bank wishes to use [[webauthn-3]] as the [=Relying Party=], that
specification requires the bank to register the user in a first party context.
Registration can happen outside of a transaction while the user is visiting the
bank's site. It is also useful to be able to register the user during a
transaction, but any registration that interrupts the payment journey creates a
risk of transaction abandonment.
This limitation motivates the following Secure Payment Confirmation behavior:
1. SPC supports cross-origin registration from an iframe in a third-party
context. For instance, this registration might take place following some
other identity and verification (<abbr>ID&V</abbr>) flow (e.g., SMS OTP).
* See <a href="https://github.com/w3c/webauthn/issues/1656">discussion
on WebAuthn issue 1656</a>.
### Merchant control of authentication ### {#sctn-use-case-merchant-authentication}
Merchants seek to avoid user drop-off during checkout, in particular by
reducing authentication friction. A [=Relying Party=] (e.g., a bank) that
wishes to use [[webauthn-3]] to authenticate the user typically does so from an
iframe. However, merchants would prefer to manage the user experience of
authenticating the user while still enabling the [=Relying Party=] to verify
the results of authentication.
This limitation motivates the following Secure Payment Confirmation behavior:
* With SPC, other parties than the [=Relying Party=] can use authentication
credentials *on behalf of* the Relying Party. The Relying Party can then
verify the authentication results.
An additional benefit of this feature to Relying Parties is that they no longer
need to build their own front-end experiences for authentication. Instead,
payment service providers are likely to build them on behalf of merchants.
NOTE: Relying Parties that wish to provide the authentication user experience
may still do so using SPC from an iframe.
## Sample API Usage Scenarios ## {#sctn-sample-scenarios}
In this section, we walk through some scenarios for Secure Payment Confirmation
and the corresponding sample code for using this API. Note that these are
example flows and do not limit the scope of how the API can be used.
### Registration during a checkout ### {#sctn-sample-registration}
This is a first-time flow, in which a new credential is created and stored by
an issuing bank during a checkout by the user on some merchant.
1. The user visits `merchant.com`, selects an item to purchase, and proceeds to
the checkout flow. They enter their payment instrument details, and indicate
that they wish to pay (e.g., by pressing a "Pay" button).
1. The merchant communicates out-of-band (e.g., using another protocol) with the
bank that issued the payment instrument. The issuing bank requests
verification of the user, and provides a bank-controlled URL for the
merchant to open in an iframe.
1. The merchant opens an iframe to `bank.com`, with the `allow` attribute set to
"[=payment permission string|payment=]".
1. In the iframe, the issuing bank confirms the user's identity via a
traditional means (e.g., SMS OTP). After confirmation, the bank invites the
user to register in SPC authentication for future payments.
1. The user consents (e.g., by clicking an "Register" button in the bank UX),
and the bank runs code in the iframe (see example below).
1. The user goes through a WebAuthn registration flow. A new credential is
created and returned to the issuing bank who stores it in their server-side
database associated with the user and payment instrument(s).
1. The verification completes; the bank iframe closes and the merchant finishes
the checkout process for the user.
Sample code for registering the user in this way follows:
<pre class="example" id="registration-example" highlight="js">
if (!window.PublicKeyCredential) { /* Client not capable. Handle error. */ }
const publicKey = {
// The challenge should be created by the bank server and sent to the iframe.
challenge: new Uint8Array([21,31,105 /* 29 more random bytes generated by the server */]),
// Relying Party:
rp: {
name: "Fancy Bank",
},
// User:
user: {
// Part of WebAuthn. This information is not required by SPC
// but may be used by the bank server to identify this user in
// future transactions. Inconsistent values for the same user
// can result in the creation of multiple credentials for the user
// and thus potential UX friction due to credential selection.
id: Uint8Array.from(window.atob("MIIBkzCCATigAwIBAjCCAZMwggE4oAMCAQIwggGTMII="), c=>c.charCodeAt(0)),
name: "jane.doe@example.com",
displayName: "Jane Doe",
},
// In this example the Relying Party accepts either an ES256 or RS256
// credential, but prefers an ES256 credential.
pubKeyCredParams: [
{
type: "public-key",
alg: -7 // "ES256"
},
{
type: "public-key",
alg: -257 // "RS256"
}
],
authenticatorSelection: {
userVerification: "required",
residentKey: "required",
authenticatorAttachment: "platform",
},
timeout: 360000, // 6 minutes
// Indicate that this is an SPC credential. This is currently required so
// that the browser knows this credential relates to SPC. It also enables
// credential creation in a cross-origin iframe, which is required for this
// example.
//
// A future version of the spec may remove the need for this extension.
extensions: {
"payment": {
isPayment: true,
}
}
};
// Note: The following call will cause the authenticator to display UI.
navigator.credentials.create({ publicKey })
.then(function (newCredentialInfo) {
// Send new credential info to server for verification and registration.
}).catch(function (err) {
// No acceptable authenticator or user refused consent. Handle appropriately.
});
</pre>
</div> <!-- non-normative -->
### Authentication on merchant site ### {#sctn-sample-authentication}
This is the flow when a user with an already registered credential is
performing a transaction and the issuing bank and merchant wish to use Secure
Payment Confirmation.
1. The user visits `merchant.com`, selects an item to purchase, and proceeds
to the checkout flow. They enter their payment instrument details, and
indicate that they wish to pay (e.g., by pressing a "Pay" button).
1. The merchant communicates out-of-band with the issuing bank of the payment
instrument (e.g., using another protocol). The issuing bank requests
verification of the user, and at the same time informs the merchant that it
accepts SPC by providing the information necessary to use the API. This
information includes a challenge and any credential IDs associated with this
user and payment instrument(s).
1. The merchant runs the example code shown below.
1. The user agrees to the payment-specific information displayed in the SPC UX,
and performs a subsequent WebAuthn authentication ceremony. The signed
cryptogram is returned to the merchant.
1. The merchant communicates the signed cryptogram to the issuing bank
out-of-band. The issuing bank verifies the cryptogram, and knows that the
user is valid, what payment-specific information has been displayed, and
that the user has consented to the transaction. The issuing bank authorizes
the transaction and the merchant finishes the checkout process for the user.
The sample code for authenticating the user follows. Note that the example code
presumes access to await/async, for easier to read promise handling.
<pre class="example" id="authentication-example" highlight="js">
/* isSecurePaymentConfirmationAvailable indicates whether the browser */
/* supports SPC. It does not indicate whether the user has a credential */
/* ready to go on this device. */
const spcAvailable =
PaymentRequest &&
PaymentRequest.isSecurePaymentConfirmationAvailable &&
await PaymentRequest.isSecurePaymentConfirmationAvailable();
if (!spcAvailable) {
/* Browser does not support SPC; merchant should fallback to traditional flows. */
}
const request = new PaymentRequest([{
supportedMethods: "secure-payment-confirmation",
data: {
// List of credential IDs obtained from the bank.
credentialIds,
rpId: "fancybank.com",
// The challenge is also obtained from the bank.
challenge: new Uint8Array([21,31,105 /* 29 more random bytes generated by the bank */]),
instrument: {
displayName: "Fancy Card ****1234",
icon: "https://fancybank.com/card-art.png",
},
payeeName: "Merchant Shop",
payeeOrigin: "https://merchant.com",
// Caller’s requested localized experience
locale: ["en"],
timeout: 360000, // 6 minutes
}], {
total: {
label: "Total",
amount: {
currency: "USD",
value: "5.00",
},
},
});
try {
const response = await request.show();
await response.complete('success');
// response.data is a PublicKeyCredential, with a clientDataJSON that
// contains the transaction data for verification by the issuing bank.
/* send response.data to the issuing bank for verification */
} catch (err) {
/* SPC cannot be used; merchant should fallback to traditional flows */
}
</pre>
# Terminology # {#sctn-terminology}
: <dfn export>SPC Credential</dfn>
:: A [=public key credential|WebAuthn credential=] that can be used for the
behaviors defined in this specification.
This specification does not intend to limit how SPC credentials may (or may
not) be used by a [=Relying Party=] for other authentication flows (e.g.,
login).
Note: The current version of this specification requires the [=Relying
Party=] to explicitly opt in for a credential to be used in
either a first-party or third-party context. Longer-term, our
intention is that all [=public key credential|WebAuthn credentials=]
will be usable for SPC in a first-party context (e.g., on the
[=Relying Party's=] domain) and opt-in will only be required to allow
a credential to be used by a third-party.
: <dfn export>Third-party enabled SPC Credential</dfn>
:: An [=SPC Credential=] where the [=Relying Party=] has explicitly opted in at
credential creation time to allow use of the credential in a Secure Payment
Confirmation authentication by a party other than the [=Relying Party=].
: <dfn>Steps to silently determine if an SPC Credential is third-party enabled</dfn>
:: An as-yet undefined process by which a user agent can, given a
[=Relying Party Identifier=] and a [=credential ID=], silently (i.e.,
without user interaction) determine if the credential represented by that ID
is a [=third-party enabled SPC Credential=].
NOTE: See <a href="https://github.com/w3c/webauthn/issues/1667">WebAuthn
issue 1667</a>.
: <dfn>Steps to silently determine if a credential is available for the current device</dfn>
:: An as-yet undefined process by which a user agent can, given a
[=Relying Party Identifier=] and a [=credential ID=], silently (i.e.,
without user interaction) determine if the credential represented by that
credential ID is available for the current device (i.e., could be
successfully used as part of a WebAuthn [[webauthn-3#sctn-getAssertion|Get]]
call).
This allows the user agent to only conditionally display
[[#sctn-transaction-confirmation-ux|the transaction UX]] to the user if
there is some chance that they can successfully complete the transaction.
NOTE: This property will likely require that [=SPC Credentials=] be
[=discoverable credential|discoverable=]; as such this specification
currently encodes that as a requirement.
NOTE: This property is very similar to that which is required for the
[[webauthn-conditional-ui inline]]. It is likely that both it and SPC could
be supported by the same underlying API.
# Registration # {#sctn-registration}
To register a user for Secure Payment Confirmation, relying parties should call
{{CredentialsContainer/create()|navigator.credentials.create()}}, with the
{{AuthenticationExtensionsClientInputs/payment}} [=WebAuthn Extension=]
specified.
<wpt>
enrollment.https.html
enrollment-in-iframe.sub.https.html
</wpt>
Note: In this specification we define an extension in order to allow
(1) credential creation in a cross-origin iframe (which WebAuthn
Levels 1 and 2 do not allow, but Level 3 <a
href="https://github.com/w3c/webauthn/pull/1801">is expected to
allow</a>) and (2) the browser to cache SPC credential IDs in the
absence of [[webauthn-conditional-ui|Conditional UI]]. If these
capabilities are available in future versions of WebAuthn, we
may remove the requirement for the extension from SPC. Note that
SPC credentials (with the extension) are otherwise full-fledged
WebAuthn credentials.
Note: At registration time, Web Authentication requires both
{{PublicKeyCredentialEntity/name}} and
{{PublicKeyCredentialUserEntity/displayName}}, although per the
definition of the [=user member=], implementations are not
required to display either of them in subsequent authentication
ceremonies. Of the two, as of October 2023
{{PublicKeyCredentialEntity/name}} is shown more
consistently. Developers should continue to monitor
implementations.
# Authentication # {#sctn-authentication}
To authenticate a payment via Secure Payment Confirmation, this specification
defines a new [=payment method=], "[=secure-payment-confirmation=]". This
payment method confirms the transaction with the user and then performs an
[=authentication ceremony=] to authenticate the user and create a signed blob
representing the authentication ceremony.
At a high level, authentication for Secure Payment Confirmation is similar to
[[webauthn-3]], with one major conceptual shift. Secure Payment Confirmation
allows a third-party (e.g., the merchant) to trigger an authentication ceremony
on behalf of the [=Relying Party=], passing in credentials that it has obtained
from the Relying Party on some other unspecified channel. See
[[#sctn-use-case-merchant-authentication]].
<!-- This WPT is to be removed after issue #216 is closed. -->
<wpt hidden>
authentication-requires-user-activation.https.html
</wpt>
## Payment Method: Secure Payment Confirmation ## {#sctn-payment-method-spc}
This specification defines a new [=payment handler=], the <dfn>Secure Payment
Confirmation payment handler</dfn>, which handles requests to authenticate a
given payment.
NOTE: To quickly support an initial SPC experiment, this API was designed atop
existing implementations of the Payment Request and Payment Handler APIs. There
is now general agreement to explore a design of SPC independent of Payment
Request. We therefore expect (without a concrete timeline) that SPC will move
away from its Payment Request origins. For developers, this should improve
feature detection, invocation, and other aspects of the API.
### Payment Method Identifier ### {#sctn-payment-method-identifier}
The [=standardized payment method identifier=] for the [=Secure Payment
Confirmation payment handler=] is "<dfn>secure-payment-confirmation</dfn>".
### Registration in [[payment-method-id]] ### {#sctn-registration-in-payment-method-id}
Add the following to the [=registry of standardized payment methods=] in
[[payment-method-id]]:
: "[=secure-payment-confirmation=]"
:: The <a href="https://w3c.github.io/secure-payment-confirmation/">Secure Payment Confirmation</a> specification.
### Modification of Payment Request constructor ### {#sctn-modify-payment-request-constructor}
In the steps for the {{PaymentRequest/constructor|PaymentRequest object's constructor}},
add a new step after step 4.3:
4. Process payment methods: *[substeps 1-3 elided]*
4. If |seenPMIs| contains "[=secure-payment-confirmation=]" and the size
of |seenPMIs| is greater than 1, throw a {{RangeError}}.
### Modification of user activation requirement ### {#sctn-modify-user-activation-requirement}
In the steps for the {{PaymentRequest/show|PaymentRequest.show()}} method,
modify steps 2 and 3:
2. If the [=relevant global object=] of [=request=] does not have
[=transient activation=], the user agent MAY:
1. Return [=a promise rejected with=] with a {{"SecurityError"}}
{{DOMException}}.
3. Otherwise, [=consume user activation=] of the [=relevant global object=].
NOTE: This allows the user agent to not require user activation, for
example to support redirect authentication flows where a user activation
may not be present upon redirect. See
[[#sctn-security-user-activation-requirement]] for security considerations.
### <dfn dictionary>SecurePaymentConfirmationRequest</dfn> Dictionary ### {#sctn-securepaymentconfirmationrequest-dictionary}
<xmp class="idl">
dictionary SecurePaymentConfirmationRequest {
required BufferSource challenge;
required USVString rpId;
required sequence<BufferSource> credentialIds;
required PaymentCredentialInstrument instrument;
unsigned long timeout;
USVString payeeName;
USVString payeeOrigin;
AuthenticationExtensionsClientInputs extensions;
sequence<USVString> locale;
boolean showOptOut;
};
</xmp>
The {{SecurePaymentConfirmationRequest}} dictionary contains the following
members:
<dl dfn-type="dict-member" dfn-for="SecurePaymentConfirmationRequest">
: <dfn>challenge</dfn> member
:: A random challenge that the relying party generates on the server side
to prevent replay attacks.
: <dfn>rpId</dfn> member
:: The [=Relying Party Identifier=] of the credentials.
: <dfn>credentialIds</dfn> member
:: The list of credential identifiers for the given instrument.
: <dfn>instrument</dfn> member
:: The description of the instrument name and icon to display during
registration and to be signed along with the transaction details.
: <dfn>timeout</dfn> member
:: The number of milliseconds before the request to sign the transaction
details times out. At most 1 hour. Default values and the range of
allowed values is defined by the user agent. Web Authentication
provides [[webauthn-3#sctn-createCredential|additional timeout guidance]].
: <dfn>payeeName</dfn> member
:: The display name of the payee that this SPC call is for (e.g., the
merchant). Optional, may be provided alongside or instead of
{{SecurePaymentConfirmationRequest/payeeOrigin}}.
: <dfn>payeeOrigin</dfn> member
:: The [=/origin=] of the payee that this SPC call is for (e.g., the
merchant). Optional, may be provided alongside or instead of
{{SecurePaymentConfirmationRequest/payeeName}}.
: <dfn>extensions</dfn> member
:: Any [=WebAuthn extensions=] that should be used for the passed
credential(s). The caller does not need to specify the
[[#sctn-payment-extension-registration| payment extension]]; it is added
automatically.
: <dfn>locale</dfn> member
:: An optional list of well-formed [[BCP47]] language tags, in descending
order of priority, that identify the [=locale=] preferences of the
website, i.e. a [=language priority list=] [[RFC4647]], which the user
agent can use to perform [=language negotiation=] and locale-affected
formatting with the caller.
NOTE: The {{SecurePaymentConfirmationRequest/locale}} is distinct from
language or direction metadata associated with specific input
members, in that it represents the caller's requested localized
experience rather than assertion about a specific string value.
See [[#sctn-i18n-considerations]] for more discussion.
: <dfn>showOptOut</dfn> member
:: Whether the user should be given a chance to opt-out during the
[[#sctn-transaction-confirmation-ux|transaction confirmation UX]].
Optional, default false.
</dl>
### Payment Method additional data type ### {#sctn-payment-method-additional-data-type}
The [=payment method additional data type=] for this payment method is
{{SecurePaymentConfirmationRequest}}.
### Checking if Secure Payment Confirmation is available ### {#sctn-secure-payment-confirmation-available-api}
A static API is added to {{PaymentRequest}} in order to provide developers a
simplified method of checking whether Secure Payment Confirmation is available.
<xmp class="idl">
partial interface PaymentRequest {
static Promise<boolean> isSecurePaymentConfirmationAvailable();
};
</xmp>
<dl dfn-type="attribute" dfn-for="PaymentRequest">
: {{PaymentRequest/isSecurePaymentConfirmationAvailable()}}
:: Upon invocation, a promise is returned that resolves with a value of
`true` if the Secure Payment Confirmation feature is available, or
`false` otherwise.
</dl>
This allows a developer to perform the following check when deciding whether to
initiate a SPC flow:
<pre class="example" id="available-example" highlight="js">
const spcAvailable =
PaymentRequest &&
PaymentRequest.isSecurePaymentConfirmationAvailable &&
await PaymentRequest.isSecurePaymentConfirmationAvailable();
</pre>
NOTE: The use of the static {{PaymentRequest/isSecurePaymentConfirmationAvailable}} method is recommended for
SPC feature detection, instead of calling {{PaymentRequest/canMakePayment}} on an already-constructed
PaymentRequest object.
### Steps to validate payment method data ### {#sctn-steps-to-validate-payment-method-data}
The [=steps to validate payment method data=] for this payment method, for an
input {{PaymentRequest}} |request| and {{SecurePaymentConfirmationRequest}} |data|, are:
<wpt>
constructor.https.html
constructor-validate-payment-method-data.https.html
</wpt>
1. If |data|["{{SecurePaymentConfirmationRequest/credentialIds}}"] is empty,
throw a {{RangeError}}.
1. For each |id| in |data|["{{SecurePaymentConfirmationRequest/credentialIds}}"]:
1. If |id| is empty, throw a {{RangeError}}.
1. If |data|["{{SecurePaymentConfirmationRequest/challenge}}"] is null or
empty, throw a {{TypeError}}.
1. If |data|["{{SecurePaymentConfirmationRequest/instrument}}"]["{{PaymentCredentialInstrument/displayName}}"]
is empty, throw a {{TypeError}}.
1. If |data|["{{SecurePaymentConfirmationRequest/instrument}}"]["{{PaymentCredentialInstrument/icon}}"]
is empty, throw a {{TypeError}}.
1. Run the URL parser on data["{{SecurePaymentConfirmationRequest/instrument}}"]
["{{PaymentCredentialInstrument/icon}}"]. If this returns failure, throw a
{{TypeError}}.
1. If |data|["{{SecurePaymentConfirmationRequest/rpId}}"] is not a
[=valid domain=], throw a {{TypeError}}.
1. If both |data|["{{SecurePaymentConfirmationRequest/payeeName}}"] and
|data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] are omitted,
throw a {{TypeError}}.
1. If either of |data|["{{SecurePaymentConfirmationRequest/payeeName}}"] or
|data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] is present and
empty, throw a {{TypeError}}.
1. If |data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] is present:
1. Let |parsedURL| be the result of running the [=URL parser=] on
|data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"].
1. If |parsedURL| is failure, then throw a {{TypeError}}.
1. If |parsedURL|'s [=url/scheme=] is not "`https`", then throw a {{TypeError}}.
### Steps to check if a payment can be made ### {#sctn-steps-to-check-if-a-payment-can-be-made}
The [=steps to check if a payment can be made=] for this payment method, for an
input {{SecurePaymentConfirmationRequest}} |data|, are:
<wpt>
constructor.https.html
authentication-invalid-icon.https.html
authentication-icon-data-url.https.html
authentication-rejected.https.html
</wpt>
1. If |data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] is present:
1. Let |parsedURL| be the result of running the [=URL parser=] on
|data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"].
1. Assert that |parsedURL| is not failure.
1. Assert that |parsedURL|'s [=url/scheme=] is "`https`".
NOTE: These pre-conditions were previously checked in the
[[#sctn-steps-to-validate-payment-method-data|steps to validate payment
method data]].
1. Set |data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] to the
[=serialization of an origin|serialization of=] |parsedURL|'s [=url/origin=].
1. [=fetch an image resource|Fetch the image resource=] for the icon, passing «["{{ImageResource/src}}" →
|data|["{{SecurePaymentConfirmationRequest/instrument}}"]["{{PaymentCredentialInstrument/icon}}"]]»
for *image*. If this fails:
1. If |data|["{{SecurePaymentConfirmationRequest/instrument}}"]["{{PaymentCredentialInstrument/iconMustBeShown}}"]
is `true`, then return `false`.
1. Otherwise, set |data|["{{SecurePaymentConfirmationRequest/instrument}}"]["{{PaymentCredentialInstrument/icon}}"]
to an empty string.
Note: This lets the RP know that the specified icon was not shown, as the output
{{CollectedClientAdditionalPaymentData/instrument}} will have an empty icon
string.
Note: The image resource must be fetched whether or not any credential
matches, to defeat attempts to [[#sctn-privacy-probing-credential-ids|probe
for credential existence]].
1. For each |id| in |data|["{{SecurePaymentConfirmationRequest/credentialIds}}"]:
1. Run the [=steps to silently determine if a credential is available for
the current device=], passing in
|data|["{{SecurePaymentConfirmationRequest/rpId}}"] and |id|.
If the result is `false`, remove |id| from
|data|["{{SecurePaymentConfirmationRequest/credentialIds}}"].
1. If the |data|["{{SecurePaymentConfirmationRequest/rpId}}"] is
not the [=origin=] of the [=relevant settings object=] of |request|,
run the [=steps to silently determine if an SPC Credential is
third-party enabled=], passing in
|data|["{{SecurePaymentConfirmationRequest/rpId}}"] and |id|. If the
result is `false`, remove |id| from
|data|["{{SecurePaymentConfirmationRequest/credentialIds}}"].
1. If |data|["{{SecurePaymentConfirmationRequest/credentialIds}}"] is now empty,
return `false`. The user agent must maintain
[[#sctn-privacy-probing-credential-ids|authentication ceremony privacy]]
and not leak this lack of matching credentials to the caller, by:
1. Not allowing the caller to perform a timing attack on this outcome versus
the user declining to authenticate on the
[[#sctn-transaction-confirmation-ux|transaction confirmation UX]], e.g.,
by presenting an alternative interstitial that the user must interact
with.
1. Rejecting the {{PaymentRequest/show|show()}} promise with a
"{{NotAllowedError}}" {{DOMException}}.
1. Return `true`.
### Displaying a transaction confirmation UX ### {#sctn-transaction-confirmation-ux}
To avoid restricting User Agent implementation choice, this specification does
not require a User Agent to display a particular user interface when
{{PaymentRequest/show|PaymentRequest.show()}} is called and the [=Secure
Payment Confirmation payment handler=] is selected. However, so that a
[=Relying Party=] can trust the information included in
{{CollectedClientPaymentData}}, the User Agent MUST ensure that the following
is communicated to the user and that the user's consent is collected for the
authentication:
* The {{CollectedClientAdditionalPaymentData/payeeName}} if it is present.
* The {{CollectedClientAdditionalPaymentData/payeeOrigin}} if it is present.
* The {{CollectedClientAdditionalPaymentData/total}}, that is the
{{PaymentCurrencyAmount/currency}} and {{PaymentCurrencyAmount/value}} of the
transaction.
* The {{CollectedClientAdditionalPaymentData/instrument}} details, that is the
payment instrument {{PaymentCredentialInstrument/displayName}} and
{{PaymentCredentialInstrument/icon}}. If an image resource could not be
fetched or decoded from the input {{PaymentCredentialInstrument/icon}},
then the User Agent may show no icon or a generic payment instrument
icon in its place.
NOTE: If the specified icon could not be fetched or decoded, then
{{PaymentCredentialInstrument/iconMustBeShown}} must be `false` here as
otherwise the [[#sctn-steps-to-check-if-a-payment-can-be-made|the steps
to check if a payment can be made]] would have failed previously.
The user agent MAY utilize the information in
{{SecurePaymentConfirmationRequest/locale}}, if any, to display a UX localized
into a language and using locale-based formatting consistent with that of the
website.
If {{SecurePaymentConfirmationRequest/showOptOut}} is `true`, the user agent
MUST give the user the opportunity to indicate that they want to opt out of the
process for the {{SecurePaymentConfirmationRequest/rpId|given relying party}}.
If the user indicates that they wish to opt-out, then the user agent must reject
the {{PaymentRequest/show|show()}} promise with an
"{{OptOutError}}" {{DOMException}}. See [[#sctn-user-opt-out]].
<wpt>
authentication-optout.https.html
</wpt>
If the [=current transaction automation mode=] is not "`none`", the user agent
should first verify that it is in an automation context (see
[[WebDriver2#security|WebDriver's Security considerations]]). The user agent
should then bypass the above communication of information and gathering of user
consent, and instead do the following based on the value of the [=current
transaction automation mode=]:
: "`autoAccept`"
:: Act as if the user has seen the transaction details and accepted
the authentication.
: "`autoReject`"
:: Act as if the user has seen the transaction details and rejected
the authentication.
: "`autoOptOut`"
:: Act as if the user has seen the transaction details and indicated
they want to opt out.
### Steps to respond to a payment request ### {#sctn-steps-to-respond-to-a-payment-request}
The [=steps to respond to a payment request=] for this payment method, for a given
{{PaymentRequest}} |request| and {{SecurePaymentConfirmationRequest}} |data|, are:
1. Let |topOrigin| be the [=top-level origin=] of the [=relevant settings object=] of |request|.
1. Let |payment| be a new a {{AuthenticationExtensionsPaymentInputs}} dictionary,
whose fields are:
: {{AuthenticationExtensionsPaymentInputs/isPayment}}
:: The boolean value `true`.
: {{AuthenticationExtensionsPaymentInputs/rpId}}
:: |data|["{{SecurePaymentConfirmationRequest/rpId}}"]
: {{AuthenticationExtensionsPaymentInputs/topOrigin}}
:: |topOrigin|
: {{AuthenticationExtensionsPaymentInputs/payeeName}}
:: |data|["{{SecurePaymentConfirmationRequest/payeeName}}"] if it is
present, otherwise omitted.
: {{AuthenticationExtensionsPaymentInputs/payeeOrigin}}
:: |data|["{{SecurePaymentConfirmationRequest/payeeOrigin}}"] if it is
present, otherwise omitted.
: {{AuthenticationExtensionsPaymentInputs/total}}
:: |request|.[=payment request details|[[details]]=]["{{PaymentDetailsInit/total}}"]
: {{AuthenticationExtensionsPaymentInputs/instrument}}
:: |data|["{{SecurePaymentConfirmationRequest/instrument}}"]
1. Let |extensions| be a new {{AuthenticationExtensionsClientInputs}} dictionary
whose {{AuthenticationExtensionsClientInputs/payment}} member is set to
|payment|, and whose other members are set from
|data|["{{SecurePaymentConfirmationRequest/extensions}}"].
1. Let |publicKeyOpts| be a new {{PublicKeyCredentialRequestOptions}}
dictionary, whose fields are:
: {{PublicKeyCredentialRequestOptions/challenge}}
:: |data|["{{SecurePaymentConfirmationRequest/challenge}}"]
: {{PublicKeyCredentialRequestOptions/timeout}}
:: |data|["{{SecurePaymentConfirmationRequest/timeout}}"]
: {{PublicKeyCredentialRequestOptions/rpId}}
:: |data|["{{SecurePaymentConfirmationRequest/rpId}}"]
: {{PublicKeyCredentialRequestOptions/userVerification}}
:: {{UserVerificationRequirement/required}}
: {{PublicKeyCredentialRequestOptions/extensions}}
:: |extensions|
Note: This algorithm hard-codes "required" as the value for {{PublicKeyCredentialRequestOptions/userVerification}}, because that is what Chrome's initial implementation supports. The current limitations may change. The Working Group invites implementers to share use cases that would benefit from support for other values (e.g., "preferred" or "discouraged").
1. For each |id| in |data|["{{SecurePaymentConfirmationRequest/credentialIds}}"]:
1. Let |descriptor| be a new {{PublicKeyCredentialDescriptor}} dictionary,
whose fields are:
: {{PublicKeyCredentialDescriptor/type}}
:: {{PublicKeyCredentialType/public-key}}
: {{PublicKeyCredentialDescriptor/id}}
:: |id|
: {{PublicKeyCredentialDescriptor/transports}}
:: A sequence of length 1 whose only member is
{{AuthenticatorTransport/internal}}.
1. [=list/Append=] |descriptor| to |publicKeyOpts|["{{PublicKeyCredentialRequestOptions/allowCredentials}}"].
1. Let |outputCredential| be the result of running the algorithm to
[=Request a Credential=], passing «["{{CredentialRequestOptions/publicKey}}"
→ |publicKeyOpts|]».
Note: Chrome's initial implementation does not pass the full `data.credentialIds` list to [=Request a Credential=]. Instead, it chooses one credential in the list that matches the current device and passes only that in.
Note: This triggers [[webauthn-3]]'s [[webauthn-3#sctn-getAssertion|Get]] behavior
1. Return |outputCredential|.
# WebAuthn Extension - "`payment`" # {#sctn-payment-extension-registration}
This [=client extension|client=] [=registration extension=] and
[=authentication extension=] indicates that a credential is either being
created for or used for Secure Payment Confirmation, respectively.
For registration, this extension relaxes the WebAuthn requirements to allow
credential creation in a cross-origin iframe, and also allows the browser to
identify and cache Secure Payment Confirmation credential IDs. For
authentication, this extension allows a third-party to perform an
authentication ceremony on behalf of the [=Relying Party=], and also adds
transaction information to the signed cryptogram.
Notably, a website should not call
{{CredentialsContainer/get()|navigator.credentials.get()}} with this extension
directly; for authentication the extension can only be accessed via
{{PaymentRequest}} with a "[=secure-payment-confirmation=]" payment method.
<wpt title="This test does not directly correspond to a spec line, but instead
tests that authentication can be triggered from inside a
cross-origin iframe. That behavior is specified by the lack of any
line forbidding it.">
authentication-in-iframe.sub.https.html
</wpt>
: Extension identifier
:: `payment`
: Operation applicability
:: [=registration extension|Registration=] and [=authentication extension|authentication=]
: Client extension input