main.go hinzugefügt

main.go

@@ -0,0 +1,196 @@
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/coreos/go-oidc/v3/oidc"
+	"golang.org/x/oauth2"
+)
+
+const (
+	keycloakURL = "https://keycloak.example.com/realms/myrealm"
+
+	clientID     = "go-demo"
+	clientSecret = "CHANGE_ME"
+
+	redirectURL = "https://app.example.com/callback"
+)
+
+var (
+	oauthConfig *oauth2.Config
+	verifier    *oidc.IDTokenVerifier
+)
+
+func main() {
+
+	ctx := context.Background()
+
+	// OIDC Discovery (.well-known/openid-configuration)
+	provider, err := oidc.NewProvider(ctx, keycloakURL)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	verifier = provider.Verifier(
+		&oidc.Config{
+			ClientID: clientID,
+		},
+	)
+
+	oauthConfig = &oauth2.Config{
+		ClientID:     clientID,
+		ClientSecret: clientSecret,
+		Endpoint:     provider.Endpoint(),
+		RedirectURL:  redirectURL,
+		Scopes: []string{
+			"openid",
+			"profile",
+			"email",
+		},
+	}
+
+	http.HandleFunc("/", home)
+	http.HandleFunc("/login", login)
+	http.HandleFunc("/callback", callback)
+	http.HandleFunc("/logout", logout)
+
+	log.Println("running :8080")
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}
+
+
+// Startet OIDC Login
+func login(w http.ResponseWriter, r *http.Request) {
+
+	// CSRF-Schutz: State erzeugen
+	state := randomString()
+
+	http.SetCookie(w, &http.Cookie{
+		Name:  "oidc_state",
+		Value: state,
+		Path:  "/",
+	})
+
+	url := oauthConfig.AuthCodeURL(
+		state,
+	)
+
+	http.Redirect(w, r, url, http.StatusFound)
+}
+
+
+// Callback von Keycloak
+func callback(w http.ResponseWriter, r *http.Request) {
+
+	stateCookie, _ := r.Cookie("oidc_state")
+
+	if stateCookie == nil ||
+		stateCookie.Value != r.URL.Query().Get("state") {
+		http.Error(w, "invalid state", 400)
+		return
+	}
+
+
+	token, err := oauthConfig.Exchange(
+		r.Context(),
+		r.URL.Query().Get("code"),
+	)
+
+	if err != nil {
+		http.Error(w, err.Error(), 500)
+		return
+	}
+
+
+	rawIDToken, ok := token.Extra("id_token").(string)
+
+	if !ok {
+		http.Error(w, "missing id_token", 500)
+		return
+	}
+
+
+	idToken, err := verifier.Verify(
+		r.Context(),
+		rawIDToken,
+	)
+
+	if err != nil {
+		http.Error(w, "invalid token", 500)
+		return
+	}
+
+
+	// Userinformationen aus Token lesen
+	var claims struct {
+		Username string `json:"preferred_username"`
+		Email    string `json:"email"`
+	}
+
+	idToken.Claims(&claims)
+
+
+	http.SetCookie(w, &http.Cookie{
+		Name:  "user",
+		Value: claims.Username,
+		Path:  "/",
+	})
+
+
+	http.Redirect(w, r, "/", 302)
+}
+
+
+func home(w http.ResponseWriter, r *http.Request) {
+
+	cookie, err := r.Cookie("user")
+
+	if err != nil {
+
+		fmt.Fprint(w, `
+<h1>OIDC Demo</h1>
+<a href="/login">
+<button>Anmeldung über OIDC</button>
+</a>
+`)
+
+		return
+	}
+
+
+	fmt.Fprintf(w, `
+<h1>Hallo %s</h1>
+
+<form action="/logout" method="post">
+<button>Abmelden</button>
+</form>
+`, cookie.Value)
+}
+
+
+func logout(w http.ResponseWriter, r *http.Request) {
+
+	http.SetCookie(w, &http.Cookie{
+		Name:   "user",
+		Value:  "",
+		Path:   "/",
+		MaxAge: -1,
+	})
+
+	http.Redirect(w, r, "/", 302)
+}
+
+
+// kleiner State Generator
+func randomString() string {
+
+	b := make([]byte, 16)
+	rand.Read(b)
+
+	return base64.RawURLEncoding.EncodeToString(b)
+}