[GITEA] rework long-term authentication

- The current architecture is inherently insecure, because you can
construct the 'secret' cookie value with values that are available in
the database. Thus provides zero protection when a database is
dumped/leaked.
- This patch implements a new architecture that's inspired from: [Paragonie Initiative](https://paragonie.com/blog/2015/04/secure-authentication-php-with-long-term-persistence#secure-remember-me-cookies).
- Integration testing is added to ensure the new mechanism works.
- Removes a setting, because it's not used anymore.

(cherry picked from commit eff097448b)

[GITEA] rework long-term authentication (squash) add migration

Reminder: the migration is run via integration tests as explained
in the commit "[DB] run all Forgejo migrations in integration tests"

(cherry picked from commit 4accf7443c)
(cherry picked from commit 99d06e344ebc3b50bafb2ac4473dd95f057d1ddc)
(cherry picked from commit d8bc98a8f0)
(cherry picked from commit 6404845df9)
(cherry picked from commit 72bdd4f3b9)
(cherry picked from commit 4b01bb0ce8)
(cherry picked from commit c26ac31816)

models/auth/auth_token.go

@@ -0,0 +1,96 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/modules/util"
+)
+
+// AuthorizationToken represents a authorization token to a user.
+type AuthorizationToken struct {
+	ID              int64  `xorm:"pk autoincr"`
+	UID             int64  `xorm:"INDEX"`
+	LookupKey       string `xorm:"INDEX UNIQUE"`
+	HashedValidator string
+	Expiry          timeutil.TimeStamp
+}
+
+// TableName provides the real table name.
+func (AuthorizationToken) TableName() string {
+	return "forgejo_auth_token"
+}
+
+func init() {
+	db.RegisterModel(new(AuthorizationToken))
+}
+
+// IsExpired returns if the authorization token is expired.
+func (authToken *AuthorizationToken) IsExpired() bool {
+	return authToken.Expiry.AsLocalTime().Before(time.Now())
+}
+
+// GenerateAuthToken generates a new authentication token for the given user.
+// It returns the lookup key and validator values that should be passed to the
+// user via a long-term cookie.
+func GenerateAuthToken(ctx context.Context, userID int64, expiry timeutil.TimeStamp) (lookupKey, validator string, err error) {
+	// Request 64 random bytes. The first 32 bytes will be used for the lookupKey
+	// and the other 32 bytes will be used for the validator.
+	rBytes, err := util.CryptoRandomBytes(64)
+	if err != nil {
+		return "", "", err
+	}
+	hexEncoded := hex.EncodeToString(rBytes)
+	validator, lookupKey = hexEncoded[64:], hexEncoded[:64]
+
+	_, err = db.GetEngine(ctx).Insert(&AuthorizationToken{
+		UID:             userID,
+		Expiry:          expiry,
+		LookupKey:       lookupKey,
+		HashedValidator: HashValidator(rBytes[32:]),
+	})
+	return lookupKey, validator, err
+}
+
+// FindAuthToken will find a authorization token via the lookup key.
+func FindAuthToken(ctx context.Context, lookupKey string) (*AuthorizationToken, error) {
+	var authToken AuthorizationToken
+	has, err := db.GetEngine(ctx).Where("lookup_key = ?", lookupKey).Get(&authToken)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, fmt.Errorf("lookup key %q: %w", lookupKey, util.ErrNotExist)
+	}
+	return &authToken, nil
+}
+
+// DeleteAuthToken will delete the authorization token.
+func DeleteAuthToken(ctx context.Context, authToken *AuthorizationToken) error {
+	_, err := db.DeleteByBean(ctx, authToken)
+	return err
+}
+
+// DeleteAuthTokenByUser will delete all authorization tokens for the user.
+func DeleteAuthTokenByUser(ctx context.Context, userID int64) error {
+	if userID == 0 {
+		return nil
+	}
+
+	_, err := db.DeleteByBean(ctx, &AuthorizationToken{UID: userID})
+	return err
+}
+
+// HashValidator will return a hexified hashed version of the validator.
+func HashValidator(validator []byte) string {
+	h := sha256.New()
+	h.Write(validator)
+	return hex.EncodeToString(h.Sum(nil))
+}

models/forgejo_migrations/migrate.go

@@ -41,6 +41,8 @@ var migrations = []*Migration{
 	NewMigration("Add Forgejo Blocked Users table", forgejo_v1_20.AddForgejoBlockedUser),
 	// v1 -> v2
 	NewMigration("create the forgejo_sem_ver table", forgejo_v1_20.CreateSemVerTable),
+	// v2 -> v3
+	NewMigration("create the forgejo_auth_token table", forgejo_v1_20.CreateAuthorizationTokenTable),
 }
 
 // GetCurrentDBVersion returns the current Forgejo database version.

models/forgejo_migrations/v1_20/v3.go

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: MIT
+
+package forgejo_v1_20 //nolint:revive
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+type AuthorizationToken struct {
+	ID              int64  `xorm:"pk autoincr"`
+	UID             int64  `xorm:"INDEX"`
+	LookupKey       string `xorm:"INDEX UNIQUE"`
+	HashedValidator string
+	Expiry          timeutil.TimeStamp
+}
+
+func (AuthorizationToken) TableName() string {
+	return "forgejo_auth_token"
+}
+
+func CreateAuthorizationTokenTable(x *xorm.Engine) error {
+	return x.Sync(new(AuthorizationToken))
+}

models/user/user.go

@@ -386,6 +386,11 @@ func (u *User) SetPassword(passwd string) (err error) {
 		return nil
 	}
 
+	// Invalidate all authentication tokens for this user.
+	if err := auth.DeleteAuthTokenByUser(db.DefaultContext, u.ID); err != nil {
+		return err
+	}
+
 	if u.Salt, err = GetUserSalt(); err != nil {
 		return err
 	}

modules/context/context_cookie.go

@@ -4,16 +4,14 @@
 package context
 
 import (
-	"crypto/sha256"
-	"encoding/hex"
 	"net/http"
 	"strings"
 
+	auth_model "code.gitea.io/gitea/models/auth"
+	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/web/middleware"
-
-	"golang.org/x/crypto/pbkdf2"
 )
 
 const CookieNameFlash = "gitea_flash"
@@ -46,41 +44,13 @@ func (ctx *Context) GetSiteCookie(name string) string {
 	return middleware.GetSiteCookie(ctx.Req, name)
 }
 
-// GetSuperSecureCookie returns given cookie value from request header with secret string.
+// SetLTACookie will generate a LTA token and add it as an cookie.
-func (ctx *Context) GetSuperSecureCookie(secret, name string) (string, bool) {
+func (ctx *Context) SetLTACookie(u *user_model.User) error {
-	val := ctx.GetSiteCookie(name)
+	days := 86400 * setting.LogInRememberDays
-	return ctx.CookieDecrypt(secret, val)
+	lookup, validator, err := auth_model.GenerateAuthToken(ctx, u.ID, timeutil.TimeStampNow().Add(int64(days)))
-}
-
-// CookieDecrypt returns given value from with secret string.
-func (ctx *Context) CookieDecrypt(secret, val string) (string, bool) {
-	if val == "" {
-		return "", false
-	}
-
-	text, err := hex.DecodeString(val)
 	if err != nil {
-		return "", false
+		return err
 	}
-
+	ctx.SetSiteCookie(setting.CookieRememberName, lookup+":"+validator, days)
-	key := pbkdf2.Key([]byte(secret), []byte(secret), 1000, 16, sha256.New)
+	return nil
-	text, err = util.AESGCMDecrypt(key, text)
-	return string(text), err == nil
-}
-
-// SetSuperSecureCookie sets given cookie value to response header with secret string.
-func (ctx *Context) SetSuperSecureCookie(secret, name, value string, maxAge int) {
-	text := ctx.CookieEncrypt(secret, value)
-	ctx.SetSiteCookie(name, text, maxAge)
-}
-
-// CookieEncrypt encrypts a given value using the provided secret
-func (ctx *Context) CookieEncrypt(secret, value string) string {
-	key := pbkdf2.Key([]byte(secret), []byte(secret), 1000, 16, sha256.New)
-	text, err := util.AESGCMEncrypt(key, []byte(value))
-	if err != nil {
-		panic("error encrypting cookie: " + err.Error())
-	}
-
-	return hex.EncodeToString(text)
 }

modules/setting/security.go

@@ -19,7 +19,6 @@ var (
 	SecretKey                          string
 	InternalToken                      string // internal access token
 	LogInRememberDays                  int
-	CookieUserName                     string
 	CookieRememberName                 string
 	ReverseProxyAuthUser               string
 	ReverseProxyAuthEmail              string
@@ -104,7 +103,6 @@ func loadSecurityFrom(rootCfg ConfigProvider) {
 	sec := rootCfg.Section("security")
 	InstallLock = HasInstallLock(rootCfg)
 	LogInRememberDays = sec.Key("LOGIN_REMEMBER_DAYS").MustInt(7)
-	CookieUserName = sec.Key("COOKIE_USERNAME").MustString("gitea_awesome")
 	SecretKey = loadSecret(sec, "SECRET_KEY_URI", "SECRET_KEY")
 	if SecretKey == "" {
 		// FIXME: https://github.com/go-gitea/gitea/issues/16832

modules/util/legacy.go

@@ -4,10 +4,6 @@
 package util
 
 import (
-	"crypto/aes"
-	"crypto/cipher"
-	"crypto/rand"
-	"errors"
 	"io"
 	"os"
 )
@@ -40,52 +36,3 @@ func CopyFile(src, dest string) error {
 	}
 	return os.Chmod(dest, si.Mode())
 }
-
-// AESGCMEncrypt (from legacy package): encrypts plaintext with the given key using AES in GCM mode. should be replaced.
-func AESGCMEncrypt(key, plaintext []byte) ([]byte, error) {
-	block, err := aes.NewCipher(key)
-	if err != nil {
-		return nil, err
-	}
-
-	gcm, err := cipher.NewGCM(block)
-	if err != nil {
-		return nil, err
-	}
-
-	nonce := make([]byte, gcm.NonceSize())
-	if _, err := rand.Read(nonce); err != nil {
-		return nil, err
-	}
-
-	ciphertext := gcm.Seal(nil, nonce, plaintext, nil)
-	return append(nonce, ciphertext...), nil
-}
-
-// AESGCMDecrypt (from legacy package): decrypts ciphertext with the given key using AES in GCM mode. should be replaced.
-func AESGCMDecrypt(key, ciphertext []byte) ([]byte, error) {
-	block, err := aes.NewCipher(key)
-	if err != nil {
-		return nil, err
-	}
-
-	gcm, err := cipher.NewGCM(block)
-	if err != nil {
-		return nil, err
-	}
-
-	size := gcm.NonceSize()
-	if len(ciphertext)-size <= 0 {
-		return nil, errors.New("ciphertext is empty")
-	}
-
-	nonce := ciphertext[:size]
-	ciphertext = ciphertext[size:]
-
-	plainText, err := gcm.Open(nil, nonce, ciphertext, nil)
-	if err != nil {
-		return nil, err
-	}
-
-	return plainText, nil
-}

modules/util/legacy_test.go

@@ -4,8 +4,6 @@
 package util
 
 import (
-	"crypto/aes"
-	"crypto/rand"
 	"fmt"
 	"os"
 	"testing"
@@ -37,21 +35,3 @@ func TestCopyFile(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, testContent, dstContent)
 }
-
-func TestAESGCM(t *testing.T) {
-	t.Parallel()
-
-	key := make([]byte, aes.BlockSize)
-	_, err := rand.Read(key)
-	assert.NoError(t, err)
-
-	plaintext := []byte("this will be encrypted")
-
-	ciphertext, err := AESGCMEncrypt(key, plaintext)
-	assert.NoError(t, err)
-
-	decrypted, err := AESGCMDecrypt(key, ciphertext)
-	assert.NoError(t, err)
-
-	assert.Equal(t, plaintext, decrypted)
-}

routers/install/install.go

@@ -553,18 +553,13 @@ func SubmitInstall(ctx *context.Context) {
 			u, _ = user_model.GetUserByName(ctx, u.Name)
 		}
 
-		days := 86400 * setting.LogInRememberDays
+		if err := ctx.SetLTACookie(u); err != nil {
-		ctx.SetSiteCookie(setting.CookieUserName, u.Name, days)
-
-		ctx.SetSuperSecureCookie(base.EncodeMD5(u.Rands+u.Passwd),
-			setting.CookieRememberName, u.Name, days)
-
-		// Auto-login for admin
-		if err = ctx.Session.Set("uid", u.ID); err != nil {
 			ctx.RenderWithErr(ctx.Tr("install.save_config_failed", err), tplInstall, &form)
 			return
 		}
-		if err = ctx.Session.Set("uname", u.Name); err != nil {
+
+		// Auto-login for admin
+		if err = ctx.Session.Set("uid", u.ID); err != nil {
 			ctx.RenderWithErr(ctx.Tr("install.save_config_failed", err), tplInstall, &form)
 			return
 		}

routers/web/auth/auth.go

@@ -5,6 +5,8 @@
 package auth
 
 import (
+	"crypto/subtle"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"net/http"
@@ -50,21 +52,47 @@ func AutoSignIn(ctx *context.Context) (bool, error) {
 		return false, nil
 	}
 
-	uname := ctx.GetSiteCookie(setting.CookieUserName)
+	authCookie := ctx.GetSiteCookie(setting.CookieRememberName)
-	if len(uname) == 0 {
+	if len(authCookie) == 0 {
 		return false, nil
 	}
 
 	isSucceed := false
 	defer func() {
 		if !isSucceed {
-			log.Trace("auto-login cookie cleared: %s", uname)
+			log.Trace("Auto login cookie is cleared: %s", authCookie)
-			ctx.DeleteSiteCookie(setting.CookieUserName)
 			ctx.DeleteSiteCookie(setting.CookieRememberName)
 		}
 	}()
 
-	u, err := user_model.GetUserByName(ctx, uname)
+	lookupKey, validator, found := strings.Cut(authCookie, ":")
+	if !found {
+		return false, nil
+	}
+
+	authToken, err := auth.FindAuthToken(ctx, lookupKey)
+	if err != nil {
+		if errors.Is(err, util.ErrNotExist) {
+			return false, nil
+		}
+		return false, err
+	}
+
+	if authToken.IsExpired() {
+		err = auth.DeleteAuthToken(ctx, authToken)
+		return false, err
+	}
+
+	rawValidator, err := hex.DecodeString(validator)
+	if err != nil {
+		return false, err
+	}
+
+	if subtle.ConstantTimeCompare([]byte(authToken.HashedValidator), []byte(auth.HashValidator(rawValidator))) == 0 {
+		return false, nil
+	}
+
+	u, err := user_model.GetUserByID(ctx, authToken.UID)
 	if err != nil {
 		if !user_model.IsErrUserNotExist(err) {
 			return false, fmt.Errorf("GetUserByName: %w", err)
@@ -72,17 +100,11 @@ func AutoSignIn(ctx *context.Context) (bool, error) {
 		return false, nil
 	}
 
-	if val, ok := ctx.GetSuperSecureCookie(
-		base.EncodeMD5(u.Rands+u.Passwd), setting.CookieRememberName); !ok || val != u.Name {
-		return false, nil
-	}
-
 	isSucceed = true
 
 	if err := updateSession(ctx, nil, map[string]any{
 		// Set session IDs
-		"uid":   u.ID,
+		"uid": authToken.UID,
-		"uname": u.Name,
 	}); err != nil {
 		return false, fmt.Errorf("unable to updateSession: %w", err)
 	}
@@ -291,10 +313,10 @@ func handleSignIn(ctx *context.Context, u *user_model.User, remember bool) {
 
 func handleSignInFull(ctx *context.Context, u *user_model.User, remember, obeyRedirect bool) string {
 	if remember {
-		days := 86400 * setting.LogInRememberDays
+		if err := ctx.SetLTACookie(u); err != nil {
-		ctx.SetSiteCookie(setting.CookieUserName, u.Name, days)
+			ctx.ServerError("GenerateAuthToken", err)
-		ctx.SetSuperSecureCookie(base.EncodeMD5(u.Rands+u.Passwd),
+			return setting.AppSubURL + "/"
-			setting.CookieRememberName, u.Name, days)
+		}
 	}
 
 	if err := updateSession(ctx, []string{
@@ -307,8 +329,7 @@ func handleSignInFull(ctx *context.Context, u *user_model.User, remember, obeyRe
 		"twofaRemember",
 		"linkAccount",
 	}, map[string]any{
-		"uid":   u.ID,
+		"uid": u.ID,
-		"uname": u.Name,
 	}); err != nil {
 		ctx.ServerError("RegenerateSession", err)
 		return setting.AppSubURL + "/"
@@ -369,7 +390,6 @@ func getUserName(gothUser *goth.User) string {
 func HandleSignOut(ctx *context.Context) {
 	_ = ctx.Session.Flush()
 	_ = ctx.Session.Destroy(ctx.Resp, ctx.Req)
-	ctx.DeleteSiteCookie(setting.CookieUserName)
 	ctx.DeleteSiteCookie(setting.CookieRememberName)
 	ctx.Csrf.DeleteCookie(ctx)
 	middleware.DeleteRedirectToCookie(ctx.Resp)
@@ -732,8 +752,7 @@ func handleAccountActivation(ctx *context.Context, user *user_model.User) {
 	log.Trace("User activated: %s", user.Name)
 
 	if err := updateSession(ctx, nil, map[string]any{
-		"uid":   user.ID,
+		"uid": user.ID,
-		"uname": user.Name,
 	}); err != nil {
 		log.Error("Unable to regenerate session for user: %-v with email: %s: %v", user, user.Email, err)
 		ctx.ServerError("ActivateUserEmail", err)

routers/web/auth/oauth.go

@@ -1118,8 +1118,7 @@ func handleOAuth2SignIn(ctx *context.Context, source *auth.Source, u *user_model
 	// we can't sign the user in just yet. Instead, redirect them to the 2FA authentication page.
 	if !needs2FA {
 		if err := updateSession(ctx, nil, map[string]any{
-			"uid":   u.ID,
+			"uid": u.ID,
-			"uname": u.Name,
 		}); err != nil {
 			ctx.ServerError("updateSession", err)
 			return

routers/web/home.go

@@ -54,8 +54,7 @@ func Home(ctx *context.Context) {
 	}
 
 	// Check auto-login.
-	uname := ctx.GetSiteCookie(setting.CookieUserName)
+	if len(ctx.GetSiteCookie(setting.CookieRememberName)) != 0 {
-	if len(uname) != 0 {
 		ctx.Redirect(setting.AppSubURL + "/user/login")
 		return
 	}

routers/web/user/setting/account.go

@@ -78,6 +78,15 @@ func AccountPost(ctx *context.Context) {
 			ctx.ServerError("UpdateUser", err)
 			return
 		}
+
+		// Re-generate LTA cookie.
+		if len(ctx.GetSiteCookie(setting.CookieRememberName)) != 0 {
+			if err := ctx.SetLTACookie(ctx.Doer); err != nil {
+				ctx.ServerError("SetLTACookie", err)
+				return
+			}
+		}
+
 		log.Trace("User password updated: %s", ctx.Doer.Name)
 		ctx.Flash.Success(ctx.Tr("settings.change_password_success"))
 	}

routers/web/web.go

@@ -181,7 +181,7 @@ func verifyAuthWithOptions(options *common.VerifyOptions) func(ctx *context.Cont
 
 		// Redirect to log in page if auto-signin info is provided and has not signed in.
 		if !options.SignOutRequired && !ctx.IsSigned &&
-			len(ctx.GetSiteCookie(setting.CookieUserName)) > 0 {
+			len(ctx.GetSiteCookie(setting.CookieRememberName)) > 0 {
 			if ctx.Req.URL.Path != "/user/events" {
 				middleware.SetRedirectToCookie(ctx.Resp, setting.AppSubURL+ctx.Req.URL.RequestURI())
 			}

services/auth/auth.go

@@ -76,10 +76,6 @@ func handleSignIn(resp http.ResponseWriter, req *http.Request, sess SessionStore
 	if err != nil {
 		log.Error(fmt.Sprintf("Error setting session: %v", err))
 	}
-	err = sess.Set("uname", user.Name)
-	if err != nil {
-		log.Error(fmt.Sprintf("Error setting session: %v", err))
-	}
 
 	// Language setting of the user overwrites the one previously set
 	// If the user does not have a locale set, we save the current one.

tests/integration/auth_token_test.go

@@ -0,0 +1,163 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"encoding/hex"
+	"net/http"
+	"net/url"
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// GetSessionForLTACookie returns a new session with only the LTA cookie being set.
+func GetSessionForLTACookie(t *testing.T, ltaCookie *http.Cookie) *TestSession {
+	t.Helper()
+
+	ch := http.Header{}
+	ch.Add("Cookie", ltaCookie.String())
+	cr := http.Request{Header: ch}
+
+	session := emptyTestSession(t)
+	baseURL, err := url.Parse(setting.AppURL)
+	assert.NoError(t, err)
+	session.jar.SetCookies(baseURL, cr.Cookies())
+
+	return session
+}
+
+// GetLTACookieValue returns the value of the LTA cookie.
+func GetLTACookieValue(t *testing.T, sess *TestSession) string {
+	t.Helper()
+
+	rememberCookie := sess.GetCookie(setting.CookieRememberName)
+	assert.NotNil(t, rememberCookie)
+
+	cookieValue, err := url.QueryUnescape(rememberCookie.Value)
+	assert.NoError(t, err)
+
+	return cookieValue
+}
+
+// TestSessionCookie checks if the session cookie provides authentication.
+func TestSessionCookie(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	sess := loginUser(t, "user1")
+	assert.NotNil(t, sess.GetCookie(setting.SessionConfig.CookieName))
+
+	req := NewRequest(t, "GET", "/user/settings")
+	sess.MakeRequest(t, req, http.StatusOK)
+}
+
+// TestLTACookie checks if the LTA cookie that's returned is valid, exists in the database
+// and provides authentication of no session cookie is present.
+func TestLTACookie(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+	sess := emptyTestSession(t)
+
+	req := NewRequestWithValues(t, "POST", "/user/login", map[string]string{
+		"_csrf":     GetCSRF(t, sess, "/user/login"),
+		"user_name": user.Name,
+		"password":  userPassword,
+		"remember":  "true",
+	})
+	sess.MakeRequest(t, req, http.StatusSeeOther)
+
+	// Checks if the database entry exist for the user.
+	ltaCookieValue := GetLTACookieValue(t, sess)
+	lookupKey, validator, found := strings.Cut(ltaCookieValue, ":")
+	assert.True(t, found)
+	rawValidator, err := hex.DecodeString(validator)
+	assert.NoError(t, err)
+	unittest.AssertExistsAndLoadBean(t, &auth.AuthorizationToken{LookupKey: lookupKey, HashedValidator: auth.HashValidator(rawValidator), UID: user.ID})
+
+	// Check if the LTA cookie it provides authentication.
+	// If LTA cookie provides authentication /user/login shouldn't return status 200.
+	session := GetSessionForLTACookie(t, sess.GetCookie(setting.CookieRememberName))
+	req = NewRequest(t, "GET", "/user/login")
+	session.MakeRequest(t, req, http.StatusSeeOther)
+}
+
+// TestLTAPasswordChange checks that LTA doesn't provide authentication when a
+// password change has happened and that the new LTA does provide authentication.
+func TestLTAPasswordChange(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+
+	sess := loginUserWithPasswordRemember(t, user.Name, userPassword, true)
+	oldRememberCookie := sess.GetCookie(setting.CookieRememberName)
+	assert.NotNil(t, oldRememberCookie)
+
+	// Make a simple password change.
+	req := NewRequestWithValues(t, "POST", "/user/settings/account", map[string]string{
+		"_csrf":        GetCSRF(t, sess, "/user/settings/account"),
+		"old_password": userPassword,
+		"password":     "password2",
+		"retype":       "password2",
+	})
+	sess.MakeRequest(t, req, http.StatusSeeOther)
+	rememberCookie := sess.GetCookie(setting.CookieRememberName)
+	assert.NotNil(t, rememberCookie)
+
+	// Check if the password really changed.
+	assert.NotEqualValues(t, unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1}).Passwd, user.Passwd)
+
+	// /user/settings/account should provide with a new LTA cookie, so check for that.
+	// If LTA cookie provides authentication /user/login shouldn't return status 200.
+	session := GetSessionForLTACookie(t, rememberCookie)
+	req = NewRequest(t, "GET", "/user/login")
+	session.MakeRequest(t, req, http.StatusSeeOther)
+
+	// Check if the old LTA token is invalidated.
+	session = GetSessionForLTACookie(t, oldRememberCookie)
+	req = NewRequest(t, "GET", "/user/login")
+	session.MakeRequest(t, req, http.StatusOK)
+}
+
+// TestLTAExpiry tests that the LTA expiry works.
+func TestLTAExpiry(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+
+	sess := loginUserWithPasswordRemember(t, user.Name, userPassword, true)
+
+	ltaCookieValie := GetLTACookieValue(t, sess)
+	lookupKey, _, found := strings.Cut(ltaCookieValie, ":")
+	assert.True(t, found)
+
+	// Ensure it's not expired.
+	lta := unittest.AssertExistsAndLoadBean(t, &auth.AuthorizationToken{UID: user.ID, LookupKey: lookupKey})
+	assert.False(t, lta.IsExpired())
+
+	// Manually stub LTA's expiry.
+	_, err := db.GetEngine(db.DefaultContext).ID(lta.ID).Table("forgejo_auth_token").Cols("expiry").Update(&auth.AuthorizationToken{Expiry: timeutil.TimeStampNow()})
+	assert.NoError(t, err)
+
+	// Ensure it's expired.
+	lta = unittest.AssertExistsAndLoadBean(t, &auth.AuthorizationToken{UID: user.ID, LookupKey: lookupKey})
+	assert.True(t, lta.IsExpired())
+
+	// Should return 200 OK, because LTA doesn't provide authorization anymore.
+	session := GetSessionForLTACookie(t, sess.GetCookie(setting.CookieRememberName))
+	req := NewRequest(t, "GET", "/user/login")
+	session.MakeRequest(t, req, http.StatusOK)
+
+	// Ensure it's deleted.
+	unittest.AssertNotExistsBean(t, &auth.AuthorizationToken{UID: user.ID, LookupKey: lookupKey})
+}

tests/integration/integration_test.go

@@ -17,6 +17,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"testing"
@@ -299,6 +300,12 @@ func loginUser(t testing.TB, userName string) *TestSession {
 
 func loginUserWithPassword(t testing.TB, userName, password string) *TestSession {
 	t.Helper()
+
+	return loginUserWithPasswordRemember(t, userName, password, false)
+}
+
+func loginUserWithPasswordRemember(t testing.TB, userName, password string, rememberMe bool) *TestSession {
+	t.Helper()
 	req := NewRequest(t, "GET", "/user/login")
 	resp := MakeRequest(t, req, http.StatusOK)
 
@@ -307,6 +314,7 @@ func loginUserWithPassword(t testing.TB, userName, password string) *TestSession
 		"_csrf":     doc.GetCSRF(),
 		"user_name": userName,
 		"password":  password,
+		"remember":  strconv.FormatBool(rememberMe),
 	})
 	resp = MakeRequest(t, req, http.StatusSeeOther)