fix: prevent error reason leakage in case of IgnoreUnknownUsernames (#8372)

# Which Problems Are Solved

ZITADEL administrators can enable a setting called "Ignoring unknown
usernames" which helps mitigate attacks that try to guess/enumerate
usernames. If enabled, ZITADEL will show the password prompt even if the
user doesn't exist and report "Username or Password invalid".
Due to a implementation change to prevent deadlocks calling the
database, the flag would not be correctly respected in all cases and an
attacker would gain information if an account exist within ZITADEL,
since the error message shows "object not found" instead of the generic
error message.

# How the Problems Are Solved

- Proper check of the error using an error function / type and
`errors.Is`

# Additional Changes

None.

# Additional Context

- raised in a support request

Co-authored-by: Silvan <silvan.reusser@gmail.com>

internal/auth/repository/eventsourcing/eventstore/auth_request.go

@@ -2,6 +2,7 @@ package eventstore
 
 import (
 	"context"
+	"errors"
 	"slices"
 	"strings"
 	"time"
@@ -29,6 +30,12 @@ import (
 
 const unknownUserID = "UNKNOWN"
 
+var (
+	ErrUserNotFound = func(err error) error {
+		return zerrors.ThrowNotFound(err, "EVENT-hodc6", "Errors.User.NotFound")
+	}
+)
+
 type AuthRequestRepo struct {
 	Command      *command.Commands
 	Query        *query.Queries
@@ -53,6 +60,7 @@ type AuthRequestRepo struct {
 	ApplicationProvider       applicationProvider
 	CustomTextProvider        customTextProvider
 	PasswordReset             passwordReset
+	PasswordChecker           passwordChecker
 
 	IdGenerator id.Generator
 }
@@ -72,7 +80,7 @@ type userSessionViewProvider interface {
 }
 
 type userViewProvider interface {
-	UserByID(string, string) (*user_view_model.UserView, error)
+	UserByID(context.Context, string, string) (*user_view_model.UserView, error)
 }
 
 type loginPolicyViewProvider interface {
@@ -131,6 +139,10 @@ type passwordReset interface {
 	RequestSetPassword(ctx context.Context, userID, resourceOwner string, notifyType domain.NotificationType, authRequestID string) (objectDetails *domain.ObjectDetails, err error)
 }
 
+type passwordChecker interface {
+	HumanCheckPassword(ctx context.Context, resourceOwner, userID, password string, authReq *domain.AuthRequest) error
+}
+
 func (repo *AuthRequestRepo) Health(ctx context.Context) error {
 	return repo.AuthRequests.Health(ctx)
 }
@@ -347,23 +359,25 @@ func (repo *AuthRequestRepo) VerifyPassword(ctx context.Context, authReqID, user
 	request, err := repo.getAuthRequestEnsureUser(ctx, authReqID, userAgentID, userID)
 	if err != nil {
 		if isIgnoreUserNotFoundError(err, request) {
+			// use the same errorID as below (otherwise it would expose the error reason)
 			return zerrors.ThrowInvalidArgument(nil, "EVENT-SDe2f", "Errors.User.UsernameOrPassword.Invalid")
 		}
 		return err
 	}
-	err = repo.Command.HumanCheckPassword(ctx, resourceOwner, userID, password, request.WithCurrentInfo(info))
+	err = repo.PasswordChecker.HumanCheckPassword(ctx, resourceOwner, userID, password, request.WithCurrentInfo(info))
 	if isIgnoreUserInvalidPasswordError(err, request) {
-		return zerrors.ThrowInvalidArgument(nil, "EVENT-Jsf32", "Errors.User.UsernameOrPassword.Invalid")
+		// use the same errorID as above (otherwise it would expose the error reason)
+		return zerrors.ThrowInvalidArgument(nil, "EVENT-SDe2f", "Errors.User.UsernameOrPassword.Invalid")
 	}
 	return err
 }
 
 func isIgnoreUserNotFoundError(err error, request *domain.AuthRequest) bool {
-	return request != nil && request.LoginPolicy != nil && request.LoginPolicy.IgnoreUnknownUsernames && zerrors.IsNotFound(err) && zerrors.Contains(err, "Errors.User.NotFound")
+	return request != nil && request.LoginPolicy != nil && request.LoginPolicy.IgnoreUnknownUsernames && errors.Is(err, ErrUserNotFound(nil))
 }
 
 func isIgnoreUserInvalidPasswordError(err error, request *domain.AuthRequest) bool {
-	return request != nil && request.LoginPolicy != nil && request.LoginPolicy.IgnoreUnknownUsernames && zerrors.IsErrorInvalidArgument(err) && zerrors.Contains(err, "Errors.User.Password.Invalid")
+	return request != nil && request.LoginPolicy != nil && request.LoginPolicy.IgnoreUnknownUsernames && errors.Is(err, command.ErrPasswordInvalid(nil))
 }
 
 func lockoutPolicyToDomain(policy *query.LockoutPolicy) *domain.LockoutPolicy {
@@ -1646,7 +1660,7 @@ func userByID(ctx context.Context, viewProvider userViewProvider, eventProvider
 	ctx, span := tracing.NewSpan(ctx)
 	defer func() { span.EndWithError(err) }()
 
-	user, viewErr := viewProvider.UserByID(userID, authz.GetInstance(ctx).InstanceID())
+	user, viewErr := viewProvider.UserByID(ctx, userID, authz.GetInstance(ctx).InstanceID())
 	if viewErr != nil && !zerrors.IsNotFound(viewErr) {
 		return nil, viewErr
 	} else if user == nil {
@@ -1659,9 +1673,10 @@ func userByID(ctx context.Context, viewProvider userViewProvider, eventProvider
 	}
 	if len(events) == 0 {
 		if viewErr != nil {
-			return nil, viewErr
+			// We already returned all errors apart from not found, but need to make sure that can be checked in case IgnoreUnknownUsernames option is active.
+			return nil, ErrUserNotFound(viewErr)
 		}
-		return user_view_model.UserToModel(user), viewErr
+		return user_view_model.UserToModel(user), nil
 	}
 	userCopy := *user
 	for _, event := range events {

internal/auth/repository/eventsourcing/eventstore/auth_request_test.go

@@ -10,9 +10,11 @@ import (
 	"github.com/stretchr/testify/assert"
 	"go.uber.org/mock/gomock"
 
+	"github.com/zitadel/zitadel/internal/api/authz"
 	"github.com/zitadel/zitadel/internal/auth/repository/eventsourcing/view"
 	cache "github.com/zitadel/zitadel/internal/auth_request/repository"
 	"github.com/zitadel/zitadel/internal/auth_request/repository/mock"
+	"github.com/zitadel/zitadel/internal/command"
 	"github.com/zitadel/zitadel/internal/crypto"
 	"github.com/zitadel/zitadel/internal/database"
 	"github.com/zitadel/zitadel/internal/domain"
@@ -103,7 +105,7 @@ func (m *mockViewUserSession) GetLatestUserSessionSequence(ctx context.Context,
 
 type mockViewNoUser struct{}
 
-func (m *mockViewNoUser) UserByID(string, string) (*user_view_model.UserView, error) {
+func (m *mockViewNoUser) UserByID(context.Context, string, string) (*user_view_model.UserView, error) {
 	return nil, zerrors.ThrowNotFound(nil, "id", "user not found")
 }
 
@@ -203,7 +205,7 @@ func (m *mockPasswordAgePolicy) PasswordAgePolicyByOrg(context.Context, bool, st
 	return m.policy, nil
 }
 
-func (m *mockViewUser) UserByID(string, string) (*user_view_model.UserView, error) {
+func (m *mockViewUser) UserByID(context.Context, string, string) (*user_view_model.UserView, error) {
 	return &user_view_model.UserView{
 		State:    int32(user_model.UserStateActive),
 		UserName: "UserName",
@@ -325,6 +327,14 @@ func (m *mockPasswordReset) RequestSetPassword(ctx context.Context, userID, reso
 	return nil, err
 }
 
+type mockPasswordChecker struct {
+	err error
+}
+
+func (m *mockPasswordChecker) HumanCheckPassword(ctx context.Context, resourceOwner, userID, password string, authReq *domain.AuthRequest) error {
+	return m.err
+}
+
 func TestAuthRequestRepo_nextSteps(t *testing.T) {
 	type fields struct {
 		AuthRequests              cache.AuthRequestCache
@@ -2482,3 +2492,153 @@ func Test_userByID(t *testing.T) {
 		})
 	}
 }
+
+func TestAuthRequestRepo_VerifyPassword_IgnoreUnknownUsernames(t *testing.T) {
+	authRequest := func(userID string) *domain.AuthRequest {
+		a := &domain.AuthRequest{
+			ID:      "authRequestID",
+			AgentID: "userAgentID",
+			UserID:  userID,
+			LoginPolicy: &domain.LoginPolicy{
+				ObjectRoot:            es_models.ObjectRoot{},
+				Default:               true,
+				AllowUsernamePassword: true,
+				AllowRegister:         true,
+				AllowExternalIDP:      true,
+				IDPProviders: []*domain.IDPProvider{
+					{
+						ObjectRoot:  es_models.ObjectRoot{},
+						Type:        domain.IdentityProviderTypeSystem,
+						IDPConfigID: "idpConfig1",
+						Name:        "IdP",
+						IDPType:     domain.IDPTypeOIDC,
+						IDPState:    domain.IDPConfigStateActive,
+					},
+				},
+				IgnoreUnknownUsernames: true,
+			},
+			AllowedExternalIDPs: []*domain.IDPProvider{
+				{
+					ObjectRoot:  es_models.ObjectRoot{},
+					Type:        domain.IdentityProviderTypeSystem,
+					IDPConfigID: "idpConfig1",
+					Name:        "IdP",
+					IDPType:     domain.IDPTypeOIDC,
+					IDPState:    domain.IDPConfigStateActive,
+				},
+			},
+			LabelPolicy: &domain.LabelPolicy{
+				ObjectRoot: es_models.ObjectRoot{},
+				State:      domain.LabelPolicyStateActive,
+				Default:    true,
+			},
+			PrivacyPolicy: &domain.PrivacyPolicy{
+				ObjectRoot: es_models.ObjectRoot{},
+				State:      domain.PolicyStateActive,
+				Default:    true,
+			},
+			LockoutPolicy: &domain.LockoutPolicy{
+				Default: true,
+			},
+			PasswordAgePolicy: &domain.PasswordAgePolicy{
+				ObjectRoot:     es_models.ObjectRoot{},
+				MaxAgeDays:     0,
+				ExpireWarnDays: 0,
+			},
+			DefaultTranslations: []*domain.CustomText{{}},
+			OrgTranslations:     []*domain.CustomText{{}},
+			SAMLRequestID:       "",
+		}
+		a.SetPolicyOrgID("instance1")
+		return a
+	}
+	type fields struct {
+		AuthRequests      func(*testing.T, string) cache.AuthRequestCache
+		UserViewProvider  userViewProvider
+		UserEventProvider userEventProvider
+		OrgViewProvider   orgViewProvider
+		PasswordChecker   passwordChecker
+	}
+	type args struct {
+		ctx           context.Context
+		authReqID     string
+		userID        string
+		resourceOwner string
+		password      string
+		userAgentID   string
+		info          *domain.BrowserInfo
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+	}{
+		{
+			name: "no user",
+			fields: fields{
+				AuthRequests: func(tt *testing.T, userID string) cache.AuthRequestCache {
+					m := mock.NewMockAuthRequestCache(gomock.NewController(tt))
+					a := authRequest(userID)
+					m.EXPECT().GetAuthRequestByID(gomock.Any(), "authRequestID").Return(a, nil)
+					m.EXPECT().CacheAuthRequest(gomock.Any(), a)
+					return m
+				},
+				UserViewProvider:  &mockViewNoUser{},
+				UserEventProvider: &mockEventUser{},
+			},
+			args: args{
+				ctx:           authz.NewMockContext("instance1", "", ""),
+				authReqID:     "authRequestID",
+				userID:        unknownUserID,
+				resourceOwner: "org1",
+				password:      "password",
+				userAgentID:   "userAgentID",
+				info: &domain.BrowserInfo{
+					UserAgent: "useragent",
+				},
+			},
+		},
+		{
+			name: "invalid password",
+			fields: fields{
+				AuthRequests: func(tt *testing.T, userID string) cache.AuthRequestCache {
+					m := mock.NewMockAuthRequestCache(gomock.NewController(tt))
+					a := authRequest(userID)
+					m.EXPECT().GetAuthRequestByID(gomock.Any(), "authRequestID").Return(a, nil)
+					m.EXPECT().CacheAuthRequest(gomock.Any(), a)
+					return m
+				},
+				UserViewProvider:  &mockViewUser{},
+				UserEventProvider: &mockEventUser{},
+				OrgViewProvider:   &mockViewOrg{State: domain.OrgStateActive},
+				PasswordChecker: &mockPasswordChecker{
+					err: command.ErrPasswordInvalid(nil),
+				},
+			},
+			args: args{
+				ctx:           authz.NewMockContext("instance1", "", ""),
+				authReqID:     "authRequestID",
+				userID:        "user1",
+				resourceOwner: "org1",
+				password:      "password",
+				userAgentID:   "userAgentID",
+				info: &domain.BrowserInfo{
+					UserAgent: "useragent",
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			repo := &AuthRequestRepo{
+				AuthRequests:      tt.fields.AuthRequests(t, tt.args.userID),
+				UserViewProvider:  tt.fields.UserViewProvider,
+				UserEventProvider: tt.fields.UserEventProvider,
+				OrgViewProvider:   tt.fields.OrgViewProvider,
+				PasswordChecker:   tt.fields.PasswordChecker,
+			}
+			err := repo.VerifyPassword(tt.args.ctx, tt.args.authReqID, tt.args.userID, tt.args.resourceOwner, tt.args.password, tt.args.userAgentID, tt.args.info)
+			assert.ErrorIs(t, err, zerrors.ThrowInvalidArgument(nil, "EVENT-SDe2f", "Errors.User.UsernameOrPassword.Invalid"))
+		})
+	}
+}

internal/auth/repository/eventsourcing/repository.go

@@ -79,6 +79,7 @@ func Start(ctx context.Context, conf Config, systemDefaults sd.SystemDefaults, c
 			ApplicationProvider:       queries,
 			CustomTextProvider:        queries,
 			PasswordReset:             command,
+			PasswordChecker:           command,
 			IdGenerator:               id.SonyFlakeGenerator(),
 		},
 		eventstore.TokenRepo{

internal/auth/repository/eventsourcing/view/user.go

@@ -16,8 +16,8 @@ const (
 	userTable = "auth.users3"
 )
 
-func (v *View) UserByID(userID, instanceID string) (*model.UserView, error) {
+func (v *View) UserByID(ctx context.Context, userID, instanceID string) (*model.UserView, error) {
-	return view.UserByID(v.Db, userTable, userID, instanceID)
+	return view.UserByID(ctx, v.Db, userID, instanceID)
 }
 
 func (v *View) UserByLoginName(ctx context.Context, loginName, instanceID string) (*model.UserView, error) {
@@ -27,7 +27,7 @@ func (v *View) UserByLoginName(ctx context.Context, loginName, instanceID string
 	}
 
 	//nolint: contextcheck // no lint was added because refactor would change too much code
-	return view.UserByID(v.Db, userTable, queriedUser.ID, instanceID)
+	return view.UserByID(ctx, v.Db, queriedUser.ID, instanceID)
 }
 
 func (v *View) UserByLoginNameAndResourceOwner(ctx context.Context, loginName, resourceOwner, instanceID string) (*model.UserView, error) {
@@ -37,7 +37,7 @@ func (v *View) UserByLoginNameAndResourceOwner(ctx context.Context, loginName, r
 	}
 
 	//nolint: contextcheck // no lint was added because refactor would change too much code
-	user, err := view.UserByID(v.Db, userTable, queriedUser.ID, instanceID)
+	user, err := view.UserByID(ctx, v.Db, queriedUser.ID, instanceID)
 	if err != nil {
 		return nil, err
 	}
@@ -103,7 +103,7 @@ func (v *View) userByID(ctx context.Context, instanceID string, queries ...query
 		OnError(err).
 		Errorf("could not get current sequence for userByID")
 
-	user, err := view.UserByID(v.Db, userTable, queriedUser.ID, instanceID)
+	user, err := view.UserByID(ctx, v.Db, queriedUser.ID, instanceID)
 	if err != nil && !zerrors.IsNotFound(err) {
 		return nil, err
 	}

internal/command/user_human_password.go

@@ -16,6 +16,15 @@ import (
 	"github.com/zitadel/zitadel/internal/zerrors"
 )
 
+var (
+	ErrPasswordInvalid = func(err error) error {
+		return zerrors.ThrowInvalidArgument(err, "COMMAND-3M0fs", "Errors.User.Password.Invalid")
+	}
+	ErrPasswordUnchanged = func(err error) error {
+		return zerrors.ThrowPreconditionFailed(err, "COMMAND-Aesh5", "Errors.User.Password.NotChanged")
+	}
+)
+
 func (c *Commands) SetPassword(ctx context.Context, orgID, userID, password string, oneTime bool) (objectDetails *domain.ObjectDetails, err error) {
 	ctx, span := tracing.NewSpan(ctx)
 	defer func() { span.EndWithError(err) }()
@@ -393,10 +402,10 @@ func convertPasswapErr(err error) error {
 		return nil
 	}
 	if errors.Is(err, passwap.ErrPasswordMismatch) {
-		return zerrors.ThrowInvalidArgument(err, "COMMAND-3M0fs", "Errors.User.Password.Invalid")
+		return ErrPasswordInvalid(err)
 	}
 	if errors.Is(err, passwap.ErrPasswordNoChange) {
-		return zerrors.ThrowPreconditionFailed(err, "COMMAND-Aesh5", "Errors.User.Password.NotChanged")
+		return ErrPasswordUnchanged(err)
 	}
 	return zerrors.ThrowInternal(err, "COMMAND-CahN2", "Errors.Internal")
 }

internal/user/repository/view/user_view.go

@@ -16,12 +16,12 @@ import (
 //go:embed user_by_id.sql
 var userByIDQuery string
 
-func UserByID(db *gorm.DB, table, userID, instanceID string) (*model.UserView, error) {
+func UserByID(ctx context.Context, db *gorm.DB, userID, instanceID string) (*model.UserView, error) {
 	user := new(model.UserView)
 
 	query := db.Raw(userByIDQuery, instanceID, userID)
 
-	tx := query.BeginTx(context.Background(), &sql.TxOptions{ReadOnly: true})
+	tx := query.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
 	defer func() {
 		if err := tx.Commit().Error; err != nil {
 			logging.OnError(err).Info("commit failed")
@@ -35,8 +35,8 @@ func UserByID(db *gorm.DB, table, userID, instanceID string) (*model.UserView, e
 		return user, nil
 	}
 	if errors.Is(err, gorm.ErrRecordNotFound) {
-		return nil, zerrors.ThrowNotFound(err, "VIEW-hodc6", "object not found")
+		return nil, zerrors.ThrowNotFound(err, "VIEW-hodc6", "Errors.User.NotFound")
 	}
-	logging.WithFields("table ", table).WithError(err).Warn("get from cache error")
+	logging.WithError(err).Warn("unable to get user by id")
-	return nil, zerrors.ThrowInternal(err, "VIEW-qJBg9", "cache error")
+	return nil, zerrors.ThrowInternal(err, "VIEW-qJBg9", "unable to get user by id")
 }