parcoursmob/utils/identification/oidc.go

package identification

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
	"net/http"

	"git.coopgo.io/coopgo-apps/parcoursmob/services"
	"git.coopgo.io/coopgo-apps/parcoursmob/utils/storage"
	"github.com/coreos/go-oidc"
	"github.com/gorilla/sessions"
	"github.com/spf13/viper"
	"golang.org/x/oauth2"
)

type ContextKey string

const IdtokenKey ContextKey = "idtoken"
const ClaimsKey ContextKey = "claims"

type IdentificationProvider struct {
	SessionsStore sessions.Store
	Provider      *oidc.Provider
	OAuth2Config  oauth2.Config
	TokenVerifier *oidc.IDTokenVerifier
	Services      *services.ServicesHandler
}

func NewIdentificationProvider(cfg *viper.Viper, services *services.ServicesHandler, kv storage.KVHandler) (*IdentificationProvider, error) {
	var (
		providerURL    = cfg.GetString("identification.oidc.provider")
		clientID       = cfg.GetString("identification.oidc.client_id")
		clientSecret   = cfg.GetString("identification.oidc.client_secret")
		redirectURL    = cfg.GetString("identification.oidc.redirect_url")
		sessionsSecret = cfg.GetString("identification.sessions.secret")
	)

	provider, err := oidc.NewProvider(context.Background(), providerURL)
	if err != nil {
		return nil, err
	}

	oauth2Config := oauth2.Config{
		ClientID:     clientID,
		ClientSecret: clientSecret,
		RedirectURL:  redirectURL,

		// Discovery returns the OAuth2 endpoints.
		Endpoint: provider.Endpoint(),

		// "openid" is a required scope for OpenID Connect flows.
		Scopes: []string{oidc.ScopeOpenID, "groups", "first_name", "last_name", "display_name"},
	}

	store := storage.NewSessionStore(kv, []byte(sessionsSecret))
	verifier := provider.Verifier(&oidc.Config{ClientID: oauth2Config.ClientID})

	return &IdentificationProvider{
		SessionsStore: store,
		Provider:      provider,
		OAuth2Config:  oauth2Config,
		TokenVerifier: verifier,
		Services:      services,
	}, nil
}

func (p *IdentificationProvider) Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		session, _ := p.SessionsStore.Get(r, "parcoursmob_session")

		if session.Values["idtoken"] == nil || session.Values["idtoken"] == "" {

			state, err := newState()
			if err != nil {
				panic(err)
			}
			session.Values["state"] = state
			session.Save(r, w)
			http.Redirect(w, r, p.OAuth2Config.AuthCodeURL(state), http.StatusFound)
			return
		}

		idtoken, err := p.TokenVerifier.Verify(context.Background(), session.Values["idtoken"].(string))
		if err != nil {
			state, err := newState()
			if err != nil {
				panic(err)
			}
			session.Values["state"] = state
			delete(session.Values, "idtoken")
			http.Redirect(w, r, p.OAuth2Config.AuthCodeURL(state), http.StatusFound)
			return
		}

		var claims map[string]any

		err = idtoken.Claims(&claims)
		if err != nil {
			fmt.Println(err)
		}

		ctx := context.WithValue(r.Context(), IdtokenKey, idtoken)
		ctx = context.WithValue(ctx, ClaimsKey, claims)

		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func newState() (string, error) {
	b := make([]byte, 16)
	if _, err := io.ReadFull(rand.Reader, b); err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(b), nil
}