feat(protocol): credential mediation

This adds support for credential mediation.

protocol/authenticator.go

@@ -57,6 +57,36 @@ type AttestedCredentialData struct {
 	CredentialPublicKey []byte `json:"public_key"`
 }
 
+// CredentialMediationRequirement represents mediation requirements for clients. When making a request via get(options)
+// or create(options), developers can set a case-by-case requirement for user mediation by choosing the appropriate
+// CredentialMediationRequirement enum value.
+//
+// See https://www.w3.org/TR/credential-management-1/#mediation-requirements
+type CredentialMediationRequirement string
+
+const (
+	// MediationSilent indicates user mediation is suppressed for the given operation. If the operation can be performed
+	// without user involvement, wonderful. If user involvement is necessary, then the operation will return null rather
+	// than involving the user.
+	MediationSilent CredentialMediationRequirement = "silent"
+
+	// MediationOptional indicates if credentials can be handed over for a given operation without user mediation, they
+	// will be. If user mediation is required, then the user agent will involve the user in the decision.
+	MediationOptional CredentialMediationRequirement = "optional"
+
+	// MediationConditional indicates for get(), discovered credentials are presented to the user in a non-modal dialog
+	// along with an indication of the origin which is requesting credentials. If the user makes a gesture outside of
+	// the dialog, the dialog closes without resolving or rejecting the Promise returned by the get() method and without
+	// causing a user-visible error condition. If the user makes a gesture that selects a credential, that credential is
+	// returned to the caller. The prevent silent access flag is treated as being true regardless of its actual value:
+	// the conditional behavior always involves user mediation of some sort if applicable credentials are discovered.
+	MediationConditional CredentialMediationRequirement = "conditional"
+
+	// MediationRequired indicates the user agent will not hand over credentials without user mediation, even if the
+	// prevent silent access flag is unset for an origin.
+	MediationRequired CredentialMediationRequirement = "required"
+)
+
 // AuthenticatorAttachment represents the IDL enum of the same name, and is used as part of the Authenticator Selection
 // Criteria.
 //

protocol/options.go

@@ -5,11 +5,13 @@ import (
 )
 
 type CredentialCreation struct {
-	Response PublicKeyCredentialCreationOptions `json:"publicKey"`
+	Response  PublicKeyCredentialCreationOptions `json:"publicKey"`
+	Mediation CredentialMediationRequirement     `json:"mediation,omitempty"`
 }
 
 type CredentialAssertion struct {
-	Response PublicKeyCredentialRequestOptions `json:"publicKey"`
+	Response  PublicKeyCredentialRequestOptions `json:"publicKey"`
+	Mediation CredentialMediationRequirement    `json:"mediation,omitempty"`
 }
 
 // PublicKeyCredentialCreationOptions represents the IDL of the same name.

webauthn/login.go

@@ -31,6 +31,16 @@ type DiscoverableUserHandler func(rawID, userHandle []byte) (user User, err erro
 //
 // Specification: §5.5. Options for Assertion Generation (https://www.w3.org/TR/webauthn/#dictionary-assertion-options)
 func (webauthn *WebAuthn) BeginLogin(user User, opts ...LoginOption) (*protocol.CredentialAssertion, *SessionData, error) {
+	return webauthn.BeginMediatedLogin(user, "", opts...)
+}
+
+// BeginDiscoverableLogin begins a client-side discoverable login, previously known as Resident Key logins.
+func (webauthn *WebAuthn) BeginDiscoverableLogin(opts ...LoginOption) (*protocol.CredentialAssertion, *SessionData, error) {
+	return webauthn.beginLogin(nil, nil, "", opts...)
+}
+
+// BeginMediatedLogin is similar to BeginLogin however it also allows specifying a credential mediation requirement.
+func (webauthn *WebAuthn) BeginMediatedLogin(user User, mediation protocol.CredentialMediationRequirement, opts ...LoginOption) (*protocol.CredentialAssertion, *SessionData, error) {
 	credentials := user.WebAuthnCredentials()
 
 	if len(credentials) == 0 { // If the user does not have any credentials, we cannot perform an assertion.
@@ -43,15 +53,16 @@ func (webauthn *WebAuthn) BeginLogin(user User, opts ...LoginOption) (*protocol.
 		allowedCredentials[i] = credential.Descriptor()
 	}
 
-	return webauthn.beginLogin(user.WebAuthnID(), allowedCredentials, opts...)
+	return webauthn.beginLogin(user.WebAuthnID(), allowedCredentials, mediation, opts...)
 }
 
-// BeginDiscoverableLogin begins a client-side discoverable login, previously known as Resident Key logins.
-func (webauthn *WebAuthn) BeginDiscoverableLogin(opts ...LoginOption) (*protocol.CredentialAssertion, *SessionData, error) {
-	return webauthn.beginLogin(nil, nil, opts...)
+// BeginDiscoverableMediatedLogin begins a client-side discoverable login with a mediation requirement, previously known
+// as Resident Key logins.
+func (webauthn *WebAuthn) BeginDiscoverableMediatedLogin(mediation protocol.CredentialMediationRequirement, opts ...LoginOption) (*protocol.CredentialAssertion, *SessionData, error) {
+	return webauthn.beginLogin(nil, nil, mediation, opts...)
 }
 
-func (webauthn *WebAuthn) beginLogin(userID []byte, allowedCredentials []protocol.CredentialDescriptor, opts ...LoginOption) (assertion *protocol.CredentialAssertion, session *SessionData, err error) {
+func (webauthn *WebAuthn) beginLogin(userID []byte, allowedCredentials []protocol.CredentialDescriptor, mediation protocol.CredentialMediationRequirement, opts ...LoginOption) (assertion *protocol.CredentialAssertion, session *SessionData, err error) {
 	if err = webauthn.Config.validate(); err != nil {
 		return nil, nil, fmt.Errorf(errFmtConfigValidate, err)
 	}
@@ -62,6 +73,7 @@ func (webauthn *WebAuthn) beginLogin(userID []byte, allowedCredentials []protoco
 			UserVerification:   webauthn.Config.AuthenticatorSelection.UserVerification,
 			AllowedCredentials: allowedCredentials,
 		},
+		Mediation: mediation,
 	}
 
 	for _, opt := range opts {

webauthn/registration.go

@@ -21,6 +21,11 @@ type RegistrationOption func(*protocol.PublicKeyCredentialCreationOptions)
 
 // BeginRegistration generates a new set of registration data to be sent to the client and authenticator.
 func (webauthn *WebAuthn) BeginRegistration(user User, opts ...RegistrationOption) (creation *protocol.CredentialCreation, session *SessionData, err error) {
+	return webauthn.BeginMediatedRegistration(user, "", opts...)
+}
+
+// BeginMediatedRegistration is similar to BeginRegistration however it also allows specifying a credential mediation requirement.
+func (webauthn *WebAuthn) BeginMediatedRegistration(user User, mediation protocol.CredentialMediationRequirement, opts ...RegistrationOption) (creation *protocol.CredentialCreation, session *SessionData, err error) {
 	if err = webauthn.Config.validate(); err != nil {
 		return nil, nil, fmt.Errorf(errFmtConfigValidate, err)
 	}
@@ -64,6 +69,7 @@ func (webauthn *WebAuthn) BeginRegistration(user User, opts ...RegistrationOptio
 			AuthenticatorSelection: webauthn.Config.AuthenticatorSelection,
 			Attestation:            webauthn.Config.AttestationPreference,
 		},
+		Mediation: mediation,
 	}
 
 	for _, opt := range opts {