From b770f2217434b37557b33e490b59fee8bf43af76 Mon Sep 17 00:00:00 2001
From: Trong Huu Nguyen <trong.huu.nguyen@nav.no>
Date: Mon, 11 Jul 2022 13:37:40 +0200
Subject: [PATCH] refactor(handler/logoutcallback): extract to openid client

---
 pkg/openid/client/client.go           |  7 ++--
 pkg/openid/client/logout_callback.go  | 60 ++++++++++++++++++++++++---
 pkg/router/handler_logout_callback.go | 15 ++-----
 3 files changed, 61 insertions(+), 21 deletions(-)

diff --git a/pkg/openid/client/client.go b/pkg/openid/client/client.go
index 4fb4b30..5a34dd7 100644
--- a/pkg/openid/client/client.go
+++ b/pkg/openid/client/client.go
@@ -22,7 +22,7 @@ type Client interface {
 	Login(r *http.Request) (Login, error)
 	LoginCallback(r *http.Request, p provider.Provider, cookie *openid.LoginCookie) LoginCallback
 	Logout() (Logout, error)
-	LogoutCallback(r *http.Request) error
+	LogoutCallback(r *http.Request, cookie *openid.LogoutCookie) LogoutCallback
 	LogoutFrontchannel(r *http.Request) LogoutFrontchannel
 
 	AuthCodeGrant(ctx context.Context, code string, opts []oauth2.AuthCodeOption) (*oauth2.Token, error)
@@ -83,9 +83,8 @@ func (c client) Logout() (Logout, error) {
 	return logout, nil
 }
 
-func (c client) LogoutCallback(r *http.Request) error {
-	//TODO implement me
-	panic("implement me")
+func (c client) LogoutCallback(r *http.Request, cookie *openid.LogoutCookie) LogoutCallback {
+	return NewLogoutCallback(r, cookie)
 }
 
 func (c client) LogoutFrontchannel(r *http.Request) LogoutFrontchannel {
diff --git a/pkg/openid/client/logout_callback.go b/pkg/openid/client/logout_callback.go
index 4c1304a..f25b6f5 100644
--- a/pkg/openid/client/logout_callback.go
+++ b/pkg/openid/client/logout_callback.go
@@ -1,10 +1,60 @@
 package client
 
-type LogoutCallback struct {
-	Client
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/nais/wonderwall/pkg/openid"
+)
+
+type LogoutCallback interface {
+	ValidateRequest() error
 }
 
-func (in LogoutCallback) ValidateRequest() (bool, error) {
-	// TODO
-	panic("not implemented")
+type logoutCallback struct {
+	cookie        *openid.LogoutCookie
+	requestParams url.Values
+}
+
+func NewLogoutCallback(r *http.Request, cookie *openid.LogoutCookie) LogoutCallback {
+	return &logoutCallback{
+		requestParams: r.URL.Query(),
+		cookie:        cookie,
+	}
+}
+
+func (in logoutCallback) ValidateRequest() error {
+	if err := in.emptyRedirectError(); err != nil {
+		return err
+	}
+
+	if err := in.stateMismatchError(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (in logoutCallback) emptyRedirectError() error {
+	if len(in.cookie.RedirectTo) == 0 {
+		return fmt.Errorf("empty redirect")
+	}
+
+	return nil
+}
+
+func (in logoutCallback) stateMismatchError() error {
+	expectedState := in.cookie.State
+	actualState := in.requestParams.Get("state")
+
+	if len(actualState) <= 0 {
+		return fmt.Errorf("missing state parameter in request (possible csrf)")
+	}
+
+	if expectedState != actualState {
+		return fmt.Errorf("state parameter mismatch (possible csrf): expected %s, got %s", expectedState, actualState)
+	}
+
+	return nil
 }
diff --git a/pkg/router/handler_logout_callback.go b/pkg/router/handler_logout_callback.go
index 8e18e47..2e0a810 100644
--- a/pkg/router/handler_logout_callback.go
+++ b/pkg/router/handler_logout_callback.go
@@ -23,18 +23,9 @@ func (h *Handler) LogoutCallback(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	params := r.URL.Query()
-	expectedState := logoutCookie.State
-	actualState := params.Get("state")
-
-	if expectedState != actualState {
-		logger.Warn().Msgf("logout/callback: state parameter mismatch: expected %s, got %s; falling back to ingress", expectedState, actualState)
-		http.Redirect(w, r, h.Cfg.Wonderwall().Ingress, http.StatusTemporaryRedirect)
-		return
-	}
-
-	if len(logoutCookie.RedirectTo) == 0 {
-		logger.Warn().Msgf("logout/callback: empty redirect; falling back to ingress")
+	logoutCallback := h.Client.LogoutCallback(r, logoutCookie)
+	if err := logoutCallback.ValidateRequest(); err != nil {
+		logger.Warn().Msgf("logout/callback: %+v; falling back to ingress", err)
 		http.Redirect(w, r, h.Cfg.Wonderwall().Ingress, http.StatusTemporaryRedirect)
 		return
 	}