init

2026-05-14 13:38:41 +02:00
parent 5d1ced594d
commit be7bd79fc7
16 changed files with 1434 additions and 1 deletions
@@ -0,0 +1,358 @@
+package web
+
+import (
+	"context"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+)
+
+type AuthMode string
+
+const (
+	AuthModeLocal AuthMode = "local"
+	AuthModeOIDC  AuthMode = "oidc"
+)
+
+type AuthConfig struct {
+	Mode          AuthMode
+	Issuer        string
+	ClientID      string
+	ClientSecret  string
+	RedirectURL   string
+	Scopes        []string
+	SessionSecret []byte
+}
+
+type oidcDiscovery struct {
+	AuthorizationEndpoint string `json:"authorization_endpoint"`
+	TokenEndpoint         string `json:"token_endpoint"`
+	UserInfoEndpoint      string `json:"userinfo_endpoint"`
+	Issuer                string `json:"issuer"`
+}
+
+type oauthTokenResponse struct {
+	AccessToken string `json:"access_token"`
+	TokenType   string `json:"token_type"`
+	IDToken     string `json:"id_token"`
+	ExpiresIn   int    `json:"expires_in"`
+}
+
+type userClaims struct {
+	Subject           string `json:"sub"`
+	PreferredUsername string `json:"preferred_username"`
+	Name              string `json:"name"`
+	Email             string `json:"email"`
+}
+
+type sessionData struct {
+	Username string `json:"username"`
+	Subject  string `json:"sub,omitempty"`
+	Email    string `json:"email,omitempty"`
+	Expires  int64  `json:"exp"`
+}
+
+func AuthConfigFromEnv(logger *slog.Logger) (AuthConfig, error) {
+	mode := AuthMode(strings.ToLower(strings.TrimSpace(getenv("AUTH_MODE", "local"))))
+	if mode != AuthModeLocal && mode != AuthModeOIDC {
+		return AuthConfig{}, fmt.Errorf("unsupported AUTH_MODE %q", mode)
+	}
+
+	secret := strings.TrimSpace(os.Getenv("SESSION_SECRET"))
+	var secretBytes []byte
+	if secret == "" {
+		secretBytes = make([]byte, 32)
+		if _, err := rand.Read(secretBytes); err != nil {
+			return AuthConfig{}, err
+		}
+		logger.Warn("SESSION_SECRET is not set; generated a temporary secret. Existing sessions will be invalid after restart")
+	} else {
+		decoded, err := base64.StdEncoding.DecodeString(secret)
+		if err == nil && len(decoded) >= 32 {
+			secretBytes = decoded
+		} else {
+			secretBytes = []byte(secret)
+		}
+		if len(secretBytes) < 32 {
+			return AuthConfig{}, errors.New("SESSION_SECRET must be at least 32 bytes or a base64 encoded 32 byte value")
+		}
+	}
+
+	cfg := AuthConfig{
+		Mode:          mode,
+		Issuer:        strings.TrimRight(strings.TrimSpace(os.Getenv("OIDC_ISSUER")), "/"),
+		ClientID:      strings.TrimSpace(os.Getenv("OIDC_CLIENT_ID")),
+		ClientSecret:  strings.TrimSpace(os.Getenv("OIDC_CLIENT_SECRET")),
+		RedirectURL:   strings.TrimSpace(os.Getenv("OIDC_REDIRECT_URL")),
+		Scopes:        splitScopes(getenv("OIDC_SCOPES", "openid profile email")),
+		SessionSecret: secretBytes,
+	}
+	if cfg.Mode == AuthModeOIDC {
+		if cfg.Issuer == "" || cfg.ClientID == "" || cfg.ClientSecret == "" || cfg.RedirectURL == "" {
+			return AuthConfig{}, errors.New("AUTH_MODE=oidc requires OIDC_ISSUER, OIDC_CLIENT_ID, OIDC_CLIENT_SECRET and OIDC_REDIRECT_URL")
+		}
+	}
+	return cfg, nil
+}
+
+func (s *Server) discoverOIDC() error {
+	if s.auth.Mode != AuthModeOIDC {
+		return nil
+	}
+	discoveryURL := s.auth.Issuer + "/.well-known/openid-configuration"
+	req, err := http.NewRequest(http.MethodGet, discoveryURL, nil)
+	if err != nil {
+		return err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("OIDC discovery failed: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return fmt.Errorf("OIDC discovery returned %s", resp.Status)
+	}
+	var d oidcDiscovery
+	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&d); err != nil {
+		return err
+	}
+	if d.AuthorizationEndpoint == "" || d.TokenEndpoint == "" || d.UserInfoEndpoint == "" {
+		return errors.New("OIDC discovery response is missing required endpoints")
+	}
+	s.oidc = d
+	return nil
+}
+
+func (s *Server) handleOIDCLogin(w http.ResponseWriter, r *http.Request) {
+	if s.auth.Mode != AuthModeOIDC {
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+		return
+	}
+	state, err := randomString(32)
+	if err != nil {
+		http.Error(w, "could not create login state", http.StatusInternalServerError)
+		return
+	}
+	setCookie(w, &http.Cookie{Name: "oauth_state", Value: state, MaxAge: 10 * 60, Path: "/auth", HttpOnly: true, SameSite: http.SameSiteLaxMode, Secure: isSecure(r)})
+
+	q := url.Values{}
+	q.Set("response_type", "code")
+	q.Set("client_id", s.auth.ClientID)
+	q.Set("redirect_uri", s.auth.RedirectURL)
+	q.Set("scope", strings.Join(s.auth.Scopes, " "))
+	q.Set("state", state)
+	authURL := s.oidc.AuthorizationEndpoint + "?" + q.Encode()
+	http.Redirect(w, r, authURL, http.StatusFound)
+}
+
+func (s *Server) handleOIDCCallback(w http.ResponseWriter, r *http.Request) {
+	if s.auth.Mode != AuthModeOIDC {
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+		return
+	}
+	if errText := r.URL.Query().Get("error"); errText != "" {
+		s.renderStatus(w, r, http.StatusUnauthorized, "login.html", map[string]any{"Title": "Login", "AuthMode": s.auth.Mode, "Error": "Login abgebrochen: " + errText})
+		return
+	}
+	stateCookie, err := r.Cookie("oauth_state")
+	if err != nil || stateCookie.Value == "" || stateCookie.Value != r.URL.Query().Get("state") {
+		http.Error(w, "invalid oauth state", http.StatusBadRequest)
+		return
+	}
+	clearCookie(w, "oauth_state", "/auth")
+	code := r.URL.Query().Get("code")
+	if code == "" {
+		http.Error(w, "missing authorization code", http.StatusBadRequest)
+		return
+	}
+	tok, err := s.exchangeCode(r.Context(), code)
+	if err != nil {
+		s.logger.Error("oauth token exchange", "error", err)
+		http.Error(w, "token exchange failed", http.StatusBadGateway)
+		return
+	}
+	claims, err := s.fetchUserInfo(r.Context(), tok.AccessToken)
+	if err != nil {
+		s.logger.Error("oauth userinfo", "error", err)
+		http.Error(w, "could not fetch user info", http.StatusBadGateway)
+		return
+	}
+	username := normalizeUsername(claims)
+	if username == "" {
+		http.Error(w, "identity provider did not return a usable username", http.StatusBadGateway)
+		return
+	}
+	if err := s.setSession(w, r, sessionData{Username: username, Subject: claims.Subject, Email: claims.Email, Expires: time.Now().Add(30 * 24 * time.Hour).Unix()}); err != nil {
+		http.Error(w, "could not create session", http.StatusInternalServerError)
+		return
+	}
+	http.Redirect(w, r, "/rooms", http.StatusSeeOther)
+}
+
+func (s *Server) exchangeCode(ctx context.Context, code string) (oauthTokenResponse, error) {
+	// Keep the public signature simple for Go 1.22 without adding external OAuth dependencies.
+	values := url.Values{}
+	values.Set("grant_type", "authorization_code")
+	values.Set("code", code)
+	values.Set("redirect_uri", s.auth.RedirectURL)
+	values.Set("client_id", s.auth.ClientID)
+	values.Set("client_secret", s.auth.ClientSecret)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.oidc.TokenEndpoint, strings.NewReader(values.Encode()))
+	if err != nil {
+		return oauthTokenResponse{}, err
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("Accept", "application/json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return oauthTokenResponse{}, err
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return oauthTokenResponse{}, err
+	}
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return oauthTokenResponse{}, fmt.Errorf("token endpoint returned %s: %s", resp.Status, string(body))
+	}
+	var tok oauthTokenResponse
+	if err := json.Unmarshal(body, &tok); err != nil {
+		return oauthTokenResponse{}, err
+	}
+	if tok.AccessToken == "" {
+		return oauthTokenResponse{}, errors.New("token endpoint did not return access_token")
+	}
+	return tok, nil
+}
+
+func (s *Server) fetchUserInfo(ctx context.Context, accessToken string) (userClaims, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, s.oidc.UserInfoEndpoint, nil)
+	if err != nil {
+		return userClaims{}, err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("Accept", "application/json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return userClaims{}, err
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return userClaims{}, err
+	}
+	if resp.StatusCode < 200 || resp.StatusCode > 299 {
+		return userClaims{}, fmt.Errorf("userinfo endpoint returned %s: %s", resp.Status, string(body))
+	}
+	var claims userClaims
+	if err := json.Unmarshal(body, &claims); err != nil {
+		return userClaims{}, err
+	}
+	return claims, nil
+}
+
+func (s *Server) setSession(w http.ResponseWriter, r *http.Request, data sessionData) error {
+	b, err := json.Marshal(data)
+	if err != nil {
+		return err
+	}
+	payload := base64.RawURLEncoding.EncodeToString(b)
+	sig := sign(payload, s.auth.SessionSecret)
+	setCookie(w, &http.Cookie{Name: "chat_session", Value: payload + "." + sig, Path: "/", MaxAge: 60 * 60 * 24 * 30, HttpOnly: true, SameSite: http.SameSiteLaxMode, Secure: isSecure(r)})
+	return nil
+}
+
+func (s *Server) readSession(r *http.Request) (sessionData, bool) {
+	c, err := r.Cookie("chat_session")
+	if err != nil || c.Value == "" {
+		return sessionData{}, false
+	}
+	parts := strings.Split(c.Value, ".")
+	if len(parts) != 2 || !verify(parts[0], parts[1], s.auth.SessionSecret) {
+		return sessionData{}, false
+	}
+	b, err := base64.RawURLEncoding.DecodeString(parts[0])
+	if err != nil {
+		return sessionData{}, false
+	}
+	var data sessionData
+	if err := json.Unmarshal(b, &data); err != nil {
+		return sessionData{}, false
+	}
+	if data.Expires < time.Now().Unix() || strings.TrimSpace(data.Username) == "" {
+		return sessionData{}, false
+	}
+	return data, true
+}
+
+func sign(payload string, secret []byte) string {
+	mac := hmac.New(sha256.New, secret)
+	_, _ = mac.Write([]byte(payload))
+	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
+}
+
+func verify(payload, got string, secret []byte) bool {
+	expected := sign(payload, secret)
+	return hmac.Equal([]byte(expected), []byte(got))
+}
+
+func randomString(n int) (string, error) {
+	b := make([]byte, n)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
+func normalizeUsername(c userClaims) string {
+	for _, v := range []string{c.PreferredUsername, c.Name, c.Email, c.Subject} {
+		v = strings.TrimSpace(v)
+		if v != "" {
+			if strings.Contains(v, "@") {
+				v = strings.Split(v, "@")[0]
+			}
+			if len(v) > 40 {
+				v = v[:40]
+			}
+			return v
+		}
+	}
+	return ""
+}
+
+func splitScopes(s string) []string {
+	fields := strings.Fields(s)
+	if len(fields) == 0 {
+		return []string{"openid", "profile", "email"}
+	}
+	return fields
+}
+
+func getenv(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}
+
+func setCookie(w http.ResponseWriter, c *http.Cookie) { http.SetCookie(w, c) }
+
+func clearCookie(w http.ResponseWriter, name, path string) {
+	http.SetCookie(w, &http.Cookie{Name: name, Value: "", Path: path, MaxAge: -1, HttpOnly: true, SameSite: http.SameSiteLaxMode})
+}
+
+func isSecure(r *http.Request) bool {
+	return r.TLS != nil || strings.EqualFold(r.Header.Get("X-Forwarded-Proto"), "https")
+}