upstream-ory-kratos/selfservice/strategy/passkey/passkey_registration.go

// Copyright © 2023 Ory Corp
// SPDX-License-Identifier: Apache-2.0

package passkey

import (
	"context"
	_ "embed"
	"encoding/json"
	"net/http"
	"net/url"
	"strings"

	"go.opentelemetry.io/otel/attribute"

	"github.com/ory/x/otelx"

	"github.com/go-webauthn/webauthn/protocol"
	"github.com/go-webauthn/webauthn/webauthn"
	"github.com/pkg/errors"
	"github.com/tidwall/gjson"
	"github.com/tidwall/sjson"

	"github.com/ory/herodot"
	"github.com/ory/kratos/identity"
	"github.com/ory/kratos/schema"
	"github.com/ory/kratos/selfservice/flow"
	"github.com/ory/kratos/selfservice/flow/registration"
	"github.com/ory/kratos/ui/container"
	"github.com/ory/kratos/ui/node"
	"github.com/ory/kratos/x/webauthnx"
	"github.com/ory/x/randx"
)

var _ registration.FormHydrator = new(Strategy)

// Update Registration Flow with Passkey Method
//
// swagger:model updateRegistrationFlowWithPasskeyMethod
type updateRegistrationFlowWithPasskeyMethod struct {
	// Register a WebAuthn Security Key
	//
	// It is expected that the JSON returned by the WebAuthn registration process
	// is included here.
	Register string `json:"passkey_register"`

	// CSRFToken is the anti-CSRF token
	CSRFToken string `json:"csrf_token"`

	// The identity's traits
	//
	// required: true
	Traits json.RawMessage `json:"traits"`

	// Method
	//
	// Should be set to "passkey" when trying to add, update, or remove a Passkey.
	//
	// required: true
	Method string `json:"method"`

	// Flow is flow ID.
	//
	// swagger:ignore
	Flow string `json:"flow"`

	// Transient data to pass along to any webhooks
	//
	// required: false
	TransientPayload json.RawMessage `json:"transient_payload,omitempty"`
}

func (s *Strategy) handleRegistrationError(_ http.ResponseWriter, r *http.Request, f *registration.Flow, p *updateRegistrationFlowWithPasskeyMethod, err error) error {
	if f != nil {
		if p != nil {
			for _, n := range container.NewFromJSON("", node.DefaultGroup, p.Traits, "traits").Nodes {
				// we only set the value and not the whole field because we want to keep types from the initial form generation
				f.UI.Nodes.SetValueAttribute(n.ID(), n.Attributes.GetValue())
			}
		}

		if f.Type == flow.TypeBrowser {
			f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
		}
	}

	return err
}

func (s *Strategy) decode(r *http.Request, ds *url.URL) (*updateRegistrationFlowWithPasskeyMethod, error) {
	var p updateRegistrationFlowWithPasskeyMethod
	err := registration.DecodeBody(&p, r, registrationSchema, ds)
	return &p, err
}

func (s *Strategy) Register(w http.ResponseWriter, r *http.Request, regFlow *registration.Flow, ident *identity.Identity) (err error) {
	ctx, span := s.d.Tracer(r.Context()).Tracer().Start(r.Context(), "selfservice.strategy.passkey.Strategy.Register")
	defer otelx.End(span, &err)

	ds, err := regFlow.IdentitySchema.URL(ctx, s.d.Config())
	if err != nil {
		return err
	}

	params, err := s.decode(r, ds)
	if err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, err)
	}

	regFlow.TransientPayload = params.TransientPayload

	if params.Register == "" ||
		params.Register == "true" { // The React SDK sends "true" on empty values, so we ignore these.
		span.SetAttributes(attribute.String("not_responsible_reason", "register is empty"))
		return flow.ErrStrategyNotResponsible
	}

	if err := flow.EnsureCSRF(s.d, r, regFlow.Type, s.d.Config().DisableAPIFlowEnforcement(ctx), s.d.GenerateCSRFToken, params.CSRFToken); err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, err)
	}

	params.Method = s.ID().String()
	if err := flow.MethodEnabledAndAllowed(ctx, regFlow.GetFlowName(), params.Method, params.Method, s.d); err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, err)
	}

	if len(params.Traits) == 0 {
		params.Traits = json.RawMessage("{}")
	}
	ident.Traits = identity.Traits(params.Traits)

	webAuthnSession := gjson.GetBytes(regFlow.InternalContext, flow.PrefixInternalContextKey(s.ID(), InternalContextKeySessionData))
	if !webAuthnSession.IsObject() {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Expected WebAuthN in internal context to be an object.")))
	}
	var webAuthnSess webauthn.SessionData
	if err := json.Unmarshal([]byte(webAuthnSession.Raw), &webAuthnSess); err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Expected WebAuthN in internal context to be an object but got: %s", err)))
	}

	if len(webAuthnSess.UserID) == 0 {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Expected WebAuthN session data to contain a user ID")))
	}

	webAuthnResponse, err := protocol.ParseCredentialCreationResponseBody(strings.NewReader(params.Register))
	if err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrBadRequest().WithReasonf("Unable to parse WebAuthn response: %s", err)))
	}

	webAuthn, err := webauthn.New(s.d.Config().PasskeyConfig(ctx))
	if err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Unable to get webAuthn config").WithDebug(err.Error())))
	}

	credential, err := webAuthn.CreateCredential(&webauthnx.User{
		ID:     webAuthnSess.UserID,
		Config: webAuthn.Config,
	}, webAuthnSess, webAuthnResponse)
	if err != nil {
		if devErr := new(protocol.Error); errors.As(err, &devErr) {
			s.d.Logger().WithError(err).WithField("error_devinfo", devErr.DevInfo).Error("Failed to create WebAuthn credential")
		}
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Unable to create WebAuthn credential: %s", err)))
	}

	credentialWebAuthn := identity.CredentialFromWebAuthn(credential, true)
	credentialWebAuthnConfig, err := json.Marshal(identity.CredentialsWebAuthnConfig{
		Credentials: identity.CredentialsWebAuthn{*credentialWebAuthn},
		UserHandle:  webAuthnSess.UserID,
	})
	if err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, errors.WithStack(
			herodot.ErrInternalServerError().WithReasonf("Unable to encode identity credentials.").WithDebug(err.Error())))
	}

	ident.UpsertCredentialsConfig(s.ID(), credentialWebAuthnConfig, 1)
	passkeyCred, _ := ident.GetCredentials(s.ID())
	passkeyCred.Identifiers = []string{string(webAuthnSess.UserID)}
	ident.SetCredentials(s.ID(), *passkeyCred)
	if err := s.validateCredentials(ctx, ident); err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, err)
	}

	if err := s.d.RegistrationFlowPersister().UpdateRegistrationFlow(ctx, regFlow); err != nil {
		return s.handleRegistrationError(w, r, regFlow, params, err)
	}

	return nil
}

// passkeyCreateData carries the WebAuthn registration ceremony options to
// the bundled JS. Both display-name fields are populated from the identity
// schema's flagged traits: DisplayNameFieldName is the alphabetically-first
// candidate kept for backward compatibility with custom UIs that only read
// the singular field; DisplayNameFieldNames is the full sorted list. Newer
// clients should consume DisplayNameFieldNames and pick the first form
// field with a non-empty value.
type passkeyCreateData struct {
	CredentialOptions     *protocol.CredentialCreation `json:"credentialOptions"`
	DisplayNameFieldName  string                       `json:"displayNameFieldName"`
	DisplayNameFieldNames []string                     `json:"displayNameFieldNames"`
}

// skipMethodOnMissingDisplayName downgrades errNoDisplayNameTrait to a
// warning so that a passkey method without a usable display-name trait drops
// its UI nodes instead of failing the whole registration flow: all other
// enabled methods must keep working even when the passkey method is
// misconfigured. Any other error is returned unchanged.
func (s *Strategy) skipMethodOnMissingDisplayName(r *http.Request, err error) error {
	if !errors.Is(err, errNoDisplayNameTrait) {
		return err
	}
	s.d.Logger().WithRequest(r).Warn("The passkey method is enabled, but the identity schema does not mark any trait as a passkey display name (passkey.display_name) or WebAuthn identifier (webauthn.identifier). The passkey method will not be offered on registration flows. Update the identity schema or disable the passkey method.")
	return nil
}

func (s *Strategy) PopulateRegistrationMethod(r *http.Request, f *registration.Flow) error {
	ctx := r.Context()

	f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
	opts, err := s.hydratePassKeyRegistrationOptions(ctx, f)
	if err != nil {
		return s.skipMethodOnMissingDisplayName(r, err)
	}

	f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
	f.UI.Nodes.Upsert(injectOptions(opts))

	trigger := passkeyRegisterTrigger()
	if f.Type == flow.TypeAPI {
		// API flows should not have raw JS onClick handlers, but keep onClickTrigger
		// as a semantic enum for SPA/native apps to key off of.
		if attr, ok := trigger.Attributes.(*node.InputAttributes); ok {
			attr.OnClick = ""
		}
	}
	f.UI.Nodes.Upsert(trigger)

	if f.Type == flow.TypeBrowser {
		f.UI.Nodes.Upsert(webauthnx.NewWebAuthnScript(s.d.Config().SelfPublicURL(ctx)))
	}

	f.UI.Nodes.Upsert(passkeyRegister())
	return nil
}

func (s *Strategy) validateCredentials(ctx context.Context, i *identity.Identity) error {
	if err := s.d.IdentityValidator().Validate(ctx, i); err != nil {
		return err
	}

	c := i.GetCredentialsOr(identity.CredentialsTypePasskey, &identity.Credentials{})
	if len(c.Identifiers) == 0 {
		return schema.NewMissingIdentifierError()
	}

	return nil
}

func (s *Strategy) PopulateRegistrationMethodCredentials(r *http.Request, f *registration.Flow, options ...registration.FormHydratorModifier) error {
	ctx := r.Context()

	f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
	opts, err := s.hydratePassKeyRegistrationOptions(ctx, f)
	if err != nil {
		return s.skipMethodOnMissingDisplayName(r, err)
	}

	f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
	f.UI.Nodes.Upsert(injectOptions(opts))

	trigger := passkeyRegisterTrigger()
	if f.Type == flow.TypeAPI {
		// API flows should not have raw JS onClick handlers, but keep onClickTrigger
		// as a semantic enum for SPA/native apps to key off of.
		if attr, ok := trigger.Attributes.(*node.InputAttributes); ok {
			attr.OnClick = ""
		}
	}
	f.UI.Nodes.Upsert(trigger)

	if f.Type == flow.TypeBrowser {
		f.UI.Nodes.Upsert(webauthnx.NewWebAuthnScript(s.d.Config().SelfPublicURL(ctx)))
	}

	f.UI.Nodes.Upsert(passkeyRegister())
	return nil
}

func (s *Strategy) PopulateRegistrationMethodProfile(r *http.Request, f *registration.Flow, options ...registration.FormHydratorModifier) error {
	ctx := r.Context()

	opts, err := s.hydratePassKeyRegistrationOptions(ctx, f)
	if err != nil {
		// Without hydrated options no passkey nodes were added by
		// PopulateRegistrationMethodCredentials either, so there is nothing
		// to remove here.
		return s.skipMethodOnMissingDisplayName(r, err)
	}

	f.UI.SetCSRF(s.d.GenerateCSRFToken(r))
	f.UI.Nodes.RemoveMatching(injectOptions(opts))
	f.UI.Nodes.RemoveMatching(passkeyRegisterTrigger())
	f.UI.Nodes.RemoveMatching(webauthnx.NewWebAuthnScript(s.d.Config().SelfPublicURL(ctx)))
	f.UI.Nodes.RemoveMatching(passkeyRegister())
	return nil
}

func (s *Strategy) hydratePassKeyRegistrationOptions(ctx context.Context, f *registration.Flow) ([]byte, error) {
	defaultSchemaURL, err := f.IdentitySchema.URL(ctx, s.d.Config())
	if err != nil {
		return nil, err
	}

	if options := gjson.GetBytes(f.InternalContext, flow.PrefixInternalContextKey(s.ID(), InternalContextKeySessionOptions)); options.IsObject() {
		return []byte(options.Raw), nil
	}

	createData := new(passkeyCreateData)
	fieldNames, err := s.PasskeyDisplayNameFromSchema(ctx, defaultSchemaURL.String())
	if err != nil {
		return nil, err
	}
	// fieldNames is guaranteed non-empty here: PasskeyDisplayNameFromSchema
	// returns at least one candidate or an error. The singular field keeps the
	// alphabetically-first candidate for backward compatibility with custom UIs
	// that only read it.
	createData.DisplayNameFieldNames = fieldNames
	createData.DisplayNameFieldName = fieldNames[0]

	webAuthn, err := webauthn.New(s.d.Config().PasskeyConfig(ctx))
	if err != nil {
		return nil, errors.WithStack(err)
	}

	user := &webauthnx.User{
		Name:   "",
		ID:     []byte(randx.MustString(64, randx.AlphaNum)),
		Config: s.d.Config().PasskeyConfig(ctx),
	}

	option, sessionData, err := webAuthn.BeginRegistration(user)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	createData.CredentialOptions = option
	injectWebAuthnOptions, err := json.Marshal(createData)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	f.InternalContext, err = sjson.SetBytes(
		f.InternalContext,
		flow.PrefixInternalContextKey(s.ID(), InternalContextKeySessionData),
		sessionData,
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	f.InternalContext, err = sjson.SetRawBytes(
		f.InternalContext,
		flow.PrefixInternalContextKey(s.ID(), InternalContextKeySessionOptions),
		injectWebAuthnOptions,
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return injectWebAuthnOptions, nil
}