add autoredirect auth config

It redirects the user to to the Host header's domain whenever they try to use
token auth.

Signed-off-by: David Wu <david.wu@docker.com>

registry/auth/auth.go

@@ -21,7 +21,7 @@
 // 			if ctx, err := accessController.Authorized(ctx, access); err != nil {
 //				if challenge, ok := err.(auth.Challenge) {
 //					// Let the challenge write the response.
-//					challenge.SetHeaders(w)
+//					challenge.SetHeaders(r, w)
 //					w.WriteHeader(http.StatusUnauthorized)
 //					return
 //				} else {
@@ -87,7 +87,7 @@ type Challenge interface {
 	// adding the an HTTP challenge header on the response message. Callers
 	// are expected to set the appropriate HTTP status code (e.g. 401)
 	// themselves.
-	SetHeaders(w http.ResponseWriter)
+	SetHeaders(r *http.Request, w http.ResponseWriter)
 }
 
 // AccessController controls access to registry resources based on a request

registry/auth/htpasswd/access.go

@@ -111,7 +111,7 @@ type challenge struct {
 var _ auth.Challenge = challenge{}
 
 // SetHeaders sets the basic challenge header on the response.
-func (ch challenge) SetHeaders(w http.ResponseWriter) {
+func (ch challenge) SetHeaders(r *http.Request, w http.ResponseWriter) {
 	w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q", ch.realm))
 }
 

registry/auth/silly/access.go

@@ -82,7 +82,7 @@ type challenge struct {
 var _ auth.Challenge = challenge{}
 
 // SetHeaders sets a simple bearer challenge on the response.
-func (ch challenge) SetHeaders(w http.ResponseWriter) {
+func (ch challenge) SetHeaders(r *http.Request, w http.ResponseWriter) {
 	header := fmt.Sprintf("Bearer realm=%q,service=%q", ch.realm, ch.service)
 
 	if ch.scope != "" {

registry/auth/token/accesscontroller.go

@@ -78,6 +78,7 @@ var (
 type authChallenge struct {
 	err          error
 	realm        string
+	autoRedirect bool
 	service      string
 	accessSet    accessSet
 }
@@ -97,8 +98,14 @@ func (ac authChallenge) Status() int {
 // challengeParams constructs the value to be used in
 // the WWW-Authenticate response challenge header.
 // See https://tools.ietf.org/html/rfc6750#section-3
-func (ac authChallenge) challengeParams() string {
-	str := fmt.Sprintf("Bearer realm=%q,service=%q", ac.realm, ac.service)
+func (ac authChallenge) challengeParams(r *http.Request) string {
+	var realm string
+	if ac.autoRedirect {
+		realm = fmt.Sprintf("https://%s/auth/token", r.Host)
+	} else {
+		realm = ac.realm
+	}
+	str := fmt.Sprintf("Bearer realm=%q,service=%q", realm, ac.service)
 
 	if scope := ac.accessSet.scopeParam(); scope != "" {
 		str = fmt.Sprintf("%s,scope=%q", str, scope)
@@ -114,13 +121,14 @@ func (ac authChallenge) challengeParams() string {
 }
 
 // SetChallenge sets the WWW-Authenticate value for the response.
-func (ac authChallenge) SetHeaders(w http.ResponseWriter) {
-	w.Header().Add("WWW-Authenticate", ac.challengeParams())
+func (ac authChallenge) SetHeaders(r *http.Request, w http.ResponseWriter) {
+	w.Header().Add("WWW-Authenticate", ac.challengeParams(r))
 }
 
 // accessController implements the auth.AccessController interface.
 type accessController struct {
 	realm        string
+	autoRedirect bool
 	issuer       string
 	service      string
 	rootCerts    *x509.CertPool
@@ -131,6 +139,7 @@ type accessController struct {
 // options to the contstructor of an accessController.
 type tokenAccessOptions struct {
 	realm          string
+	autoRedirect   bool
 	issuer         string
 	service        string
 	rootCertBundle string
@@ -153,6 +162,12 @@ func checkOptions(options map[string]interface{}) (tokenAccessOptions, error) {
 
 	opts.realm, opts.issuer, opts.service, opts.rootCertBundle = vals[0], vals[1], vals[2], vals[3]
 
+	autoRedirect, ok := options["autoredirect"].(bool)
+	if !ok {
+		return opts, fmt.Errorf("token auth requires a valid option bool: autoredirect")
+	}
+	opts.autoRedirect = autoRedirect
+
 	return opts, nil
 }
 
@@ -206,6 +221,7 @@ func newAccessController(options map[string]interface{}) (auth.AccessController,
 
 	return &accessController{
 		realm:        config.realm,
+		autoRedirect: config.autoRedirect,
 		issuer:       config.issuer,
 		service:      config.service,
 		rootCerts:    rootPool,
@@ -218,6 +234,7 @@ func newAccessController(options map[string]interface{}) (auth.AccessController,
 func (ac *accessController) Authorized(ctx context.Context, accessItems ...auth.Access) (context.Context, error) {
 	challenge := &authChallenge{
 		realm:        ac.realm,
+		autoRedirect: ac.autoRedirect,
 		service:      ac.service,
 		accessSet:    newAccessSet(accessItems...),
 	}

registry/handlers/app.go

@@ -847,7 +847,7 @@ func (app *App) authorized(w http.ResponseWriter, r *http.Request, context *Cont
 		switch err := err.(type) {
 		case auth.Challenge:
 			// Add the appropriate WWW-Auth header
-			err.SetHeaders(w)
+			err.SetHeaders(r, w)
 
 			if err := errcode.ServeJSON(w, errcode.ErrorCodeUnauthorized.WithDetail(accessRecords)); err != nil {
 				dcontext.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)