server: support out-of-band auth flow

When "urn:ietf:wg:oauth:2.0:oob" is used as a redirect URI, redirect to
an internal dex page where the user is shown the code and instructed to
paste it into their app.

server/config.go

@@ -299,35 +299,23 @@ func getTemplates(issuerName, issuerLogoURL string,
 }
 
 func setTemplates(srv *Server, tpls *template.Template) error {
-	ltpl, err := findTemplate(LoginPageTemplateName, tpls)
-	if err != nil {
-		return err
-	}
-	srv.LoginTemplate = ltpl
-
-	rtpl, err := findTemplate(RegisterTemplateName, tpls)
-	if err != nil {
-		return err
-	}
-	srv.RegisterTemplate = rtpl
-
-	vtpl, err := findTemplate(VerifyEmailTemplateName, tpls)
-	if err != nil {
-		return err
-	}
-	srv.VerifyEmailTemplate = vtpl
-
-	srtpl, err := findTemplate(SendResetPasswordEmailTemplateName, tpls)
-	if err != nil {
-		return err
-	}
-	srv.SendResetPasswordEmailTemplate = srtpl
-
-	rpwtpl, err := findTemplate(ResetPasswordTemplateName, tpls)
-	if err != nil {
-		return err
+	for _, t := range []struct {
+		templateName string
+		templatePtr  **template.Template
+	}{
+		{LoginPageTemplateName, &srv.LoginTemplate},
+		{RegisterTemplateName, &srv.RegisterTemplate},
+		{VerifyEmailTemplateName, &srv.VerifyEmailTemplate},
+		{SendResetPasswordEmailTemplateName, &srv.SendResetPasswordEmailTemplate},
+		{ResetPasswordTemplateName, &srv.ResetPasswordTemplate},
+		{OOBTemplateName, &srv.OOBTemplate},
+	} {
+		tpl, err := findTemplate(t.templateName, tpls)
+		if err != nil {
+			return err
+		}
+		*t.templatePtr = tpl
 	}
-	srv.ResetPasswordTemplate = rpwtpl
 
 	return nil
 }

server/http.go

@@ -44,6 +44,7 @@ var (
 	httpPathAcceptInvitation   = "/accept-invitation"
 	httpPathDebugVars          = "/debug/vars"
 	httpPathClientRegistration = "/registration"
+	httpPathOOB                = "/oob"
 
 	cookieLastSeen                 = "LastSeen"
 	cookieShowEmailVerifiedMessage = "ShowEmailVerifiedMessage"
@@ -548,6 +549,37 @@ func handleTokenFunc(srv OIDCServer) http.HandlerFunc {
 	}
 }
 
+func handleOOBFunc(s *Server, tpl *template.Template) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "GET" {
+			w.Header().Set("Allow", "GET")
+			phttp.WriteError(w, http.StatusMethodNotAllowed, "GET only acceptable method")
+			return
+		}
+
+		key := r.URL.Query().Get("code")
+		if key == "" {
+			phttp.WriteError(w, http.StatusBadRequest, "Invalid Session")
+			return
+		}
+		sessionID, err := s.SessionManager.ExchangeKey(key)
+		if err != nil {
+			phttp.WriteError(w, http.StatusBadRequest, "Invalid Session")
+			return
+		}
+		code, err := s.SessionManager.NewSessionKey(sessionID)
+		if err != nil {
+			log.Errorf("problem getting NewSessionKey: %v", err)
+			phttp.WriteError(w, http.StatusInternalServerError, "Internal Server Error")
+			return
+		}
+
+		execTemplate(w, tpl, map[string]string{
+			"code": code,
+		})
+	}
+}
+
 func makeHealthHandler(checks []health.Checkable) http.Handler {
 	return health.Checker{
 		Checks: checks,

server/server.go

@@ -38,8 +38,8 @@ const (
 	VerifyEmailTemplateName            = "verify-email.html"
 	SendResetPasswordEmailTemplateName = "send-reset-password.html"
 	ResetPasswordTemplateName          = "reset-password.html"
-
-	APIVersion = "v1"
+	OOBTemplateName                    = "oob-template.html"
+	APIVersion                         = "v1"
 )
 
 type OIDCServer interface {
@@ -72,6 +72,7 @@ type Server struct {
 	VerifyEmailTemplate            *template.Template
 	SendResetPasswordEmailTemplate *template.Template
 	ResetPasswordTemplate          *template.Template
+	OOBTemplate                    *template.Template
 
 	HealthChecks []health.Checkable
 	Connectors   []connector.Connector
@@ -214,6 +215,7 @@ func (s *Server) HTTPHandler() http.Handler {
 	mux := http.NewServeMux()
 	mux.HandleFunc(httpPathDiscovery, handleDiscoveryFunc(s.ProviderConfig()))
 	mux.HandleFunc(httpPathAuth, handleAuthFunc(s, s.Connectors, s.LoginTemplate, s.EnableRegistration))
+	mux.HandleFunc(httpPathOOB, handleOOBFunc(s, s.OOBTemplate))
 	mux.HandleFunc(httpPathToken, handleTokenFunc(s))
 	mux.HandleFunc(httpPathKeys, handleKeysFunc(s.KeyManager, clock))
 	mux.Handle(httpPathHealth, makeHealthHandler(checks))
@@ -399,6 +401,9 @@ func (s *Server) Login(ident oidc.Identity, key string) (string, error) {
 	}
 
 	ru := ses.RedirectURL
+	if ru.String() == client.OOBRedirectURI {
+		ru = s.absURL(httpPathOOB)
+	}
 	q := ru.Query()
 	q.Set("code", code)
 	q.Set("state", ses.ClientState)

static/html/oob-template.html

@@ -0,0 +1,11 @@
+{{ template "header.html" }}
+
+<div class="panel">
+  <h2 class="heading">Login Successful</h2>
+
+  Please copy this code, switch to your application and paste it there:
+  <br/>
+  <input type="text" value="{{ .code }}" />
+</div>
+
+{{ template "footer.html" }}