Go

IDRA_ISSUER=https://<your-org>.idra.team/api/auth
IDRA_CLIENT_ID=<Client ID>
IDRA_CLIENT_SECRET=<client secret>
APP_URL=http://localhost:8080
SESSION_SECRET=<output of: openssl rand -hex 32>

mkdir idra-go && cd idra-go
go mod init idra-go-quickstart
go get github.com/coreos/go-oidc/v3/oidc golang.org/x/oauth2

package main

import (
	"context"
	"crypto/rand"
	"encoding/json"
	"fmt"
	"html"
	"log"
	"net/http"
	"net/url"
	"os"
	"sync"

	"github.com/coreos/go-oidc/v3/oidc"
	"golang.org/x/oauth2"
)

type session struct {
	Verifier, State, Nonce string
	User                   map[string]any
	IDToken                string
}

// ponytail: sessions live in memory, so they end on restart and don't span replicas. Use a shared store in production.
var (
	sessions = map[string]*session{}
	mu       sync.Mutex
)

// sessionFor returns the browser's session, creating it (and its cookie) if needed.
func sessionFor(w http.ResponseWriter, r *http.Request, secure bool) *session {
	mu.Lock()
	defer mu.Unlock()
	if c, err := r.Cookie("app_session"); err == nil && sessions[c.Value] != nil {
		return sessions[c.Value]
	}
	id := rand.Text()
	sessions[id] = &session{}
	http.SetCookie(w, &http.Cookie{
		Name: "app_session", Value: id, Path: "/", HttpOnly: true, Secure: secure, SameSite: http.SameSiteLaxMode,
	})
	return sessions[id]
}

func main() {
	ctx := context.Background()
	appURL := os.Getenv("APP_URL")
	clientID := os.Getenv("IDRA_CLIENT_ID")
	secret := os.Getenv("IDRA_CLIENT_SECRET")
	secure := len(appURL) > 5 && appURL[:5] == "https"

	provider, err := oidc.NewProvider(ctx, os.Getenv("IDRA_ISSUER"))
	if err != nil {
		log.Fatal(err)
	}
	var meta struct {
		EndSession string `json:"end_session_endpoint"`
	}
	if err := provider.Claims(&meta); err != nil {
		log.Fatal(err)
	}
	endpoint := provider.Endpoint()
	// With a secret: client_secret_basic. Without one: a public client.
	endpoint.AuthStyle = oauth2.AuthStyleInParams
	if secret != "" {
		endpoint.AuthStyle = oauth2.AuthStyleInHeader
	}
	conf := oauth2.Config{
		ClientID:     clientID,
		ClientSecret: secret,
		Endpoint:     endpoint,
		RedirectURL:  appURL + "/callback",
		Scopes:       []string{oidc.ScopeOpenID, "profile", "email", "groups"},
	}
	verifier := provider.Verifier(&oidc.Config{ClientID: clientID})

	http.HandleFunc("GET /{$}", func(w http.ResponseWriter, r *http.Request) {
		s := sessionFor(w, r, secure)
		w.Header().Set("Content-Type", "text/html")
		if s.User == nil {
			fmt.Fprint(w, `<h1>Signed out</h1><a href="/login">Sign in with IdRa</a>`)
			return
		}
		body, _ := json.MarshalIndent(s.User, "", "  ")
		fmt.Fprintf(w, `<h1>Signed in</h1><pre>%s</pre><a href="/logout">Sign out</a>`, html.EscapeString(string(body)))
	})

	http.HandleFunc("GET /login", func(w http.ResponseWriter, r *http.Request) {
		s := sessionFor(w, r, secure)
		mu.Lock()
		s.Verifier, s.State, s.Nonce = oauth2.GenerateVerifier(), rand.Text(), rand.Text()
		url := conf.AuthCodeURL(s.State, oauth2.S256ChallengeOption(s.Verifier), oidc.Nonce(s.Nonce))
		mu.Unlock()
		http.Redirect(w, r, url, http.StatusFound)
	})

	http.HandleFunc("GET /callback", func(w http.ResponseWriter, r *http.Request) {
		s := sessionFor(w, r, secure)
		mu.Lock()
		verifierValue, state, nonce := s.Verifier, s.State, s.Nonce
		mu.Unlock()
		user, idToken, err := func() (map[string]any, string, error) {
			if q := r.URL.Query(); q.Get("state") != state || state == "" {
				return nil, "", fmt.Errorf("state mismatch")
			} else if e := q.Get("error"); e != "" {
				return nil, "", fmt.Errorf("%s: %s", e, q.Get("error_description"))
			}
			token, err := conf.Exchange(r.Context(), r.URL.Query().Get("code"), oauth2.VerifierOption(verifierValue))
			if err != nil {
				return nil, "", err
			}
			raw, _ := token.Extra("id_token").(string)
			idt, err := verifier.Verify(r.Context(), raw)
			if err != nil {
				return nil, "", err
			}
			if idt.Nonce != nonce {
				return nil, "", fmt.Errorf("nonce mismatch")
			}
			// The ID token has no email or name: they come from UserInfo.
			info, err := provider.UserInfo(r.Context(), oauth2.StaticTokenSource(token))
			if err != nil {
				return nil, "", err
			}
			var claims map[string]any
			if err := info.Claims(&claims); err != nil {
				return nil, "", err
			}
			return claims, raw, nil
		}()
		if err != nil {
			log.Print(err)
			http.Error(w, "Sign-in failed: "+err.Error(), http.StatusBadRequest)
			return
		}
		mu.Lock()
		s.User, s.IDToken = user, idToken
		mu.Unlock()
		http.Redirect(w, r, "/", http.StatusFound)
	})

	http.HandleFunc("GET /logout", func(w http.ResponseWriter, r *http.Request) {
		s := sessionFor(w, r, secure)
		mu.Lock()
		idToken := s.IDToken
		s.User, s.IDToken = nil, ""
		mu.Unlock()
		if idToken == "" {
			http.Redirect(w, r, "/", http.StatusFound)
			return
		}
		q := url.Values{"id_token_hint": {idToken}, "post_logout_redirect_uri": {appURL + "/"}}
		http.Redirect(w, r, meta.EndSession+"?"+q.Encode(), http.StatusFound)
	})

	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}
	log.Printf("Listening on %s", appURL)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

set -a; source .env; set +a
go run .