Unify two factor check (#27915) (#27939)

Backport of #27915

Fixes #27819

We have support for two factor logins with the normal web login and with
basic auth. For basic auth the two factor check was implemented at three
different places and you need to know that this check is necessary. This
PR moves the check into the basic auth itself.

modules/context/api.go

@@ -11,7 +11,6 @@ import (
 	"net/url"
 	"strings"
 
-	"code.gitea.io/gitea/models/auth"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
@@ -197,32 +196,6 @@ func (ctx *APIContext) SetLinkHeader(total, pageSize int) {
 	}
 }
 
-// CheckForOTP validates OTP
-func (ctx *APIContext) CheckForOTP() {
-	if skip, ok := ctx.Data["SkipLocalTwoFA"]; ok && skip.(bool) {
-		return // Skip 2FA
-	}
-
-	otpHeader := ctx.Req.Header.Get("X-Gitea-OTP")
-	twofa, err := auth.GetTwoFactorByUID(ctx.Doer.ID)
-	if err != nil {
-		if auth.IsErrTwoFactorNotEnrolled(err) {
-			return // No 2FA enrollment for this user
-		}
-		ctx.Error(http.StatusInternalServerError, "GetTwoFactorByUID", err)
-		return
-	}
-	ok, err := twofa.ValidateTOTP(otpHeader)
-	if err != nil {
-		ctx.Error(http.StatusInternalServerError, "ValidateTOTP", err)
-		return
-	}
-	if !ok {
-		ctx.Error(http.StatusUnauthorized, "", nil)
-		return
-	}
-}
-
 // APIContexter returns apicontext as middleware
 func APIContexter() func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {

routers/api/v1/api.go

@@ -315,10 +315,6 @@ func reqToken() func(ctx *context.APIContext) {
 			return
 		}
 
-		if ctx.IsBasicAuth {
-			ctx.CheckForOTP()
-			return
-		}
 		if ctx.IsSigned {
 			return
 		}
@@ -340,7 +336,6 @@ func reqBasicAuth() func(ctx *context.APIContext) {
 			ctx.Error(http.StatusUnauthorized, "reqBasicAuth", "auth required")
 			return
 		}
-		ctx.CheckForOTP()
 	}
 }
 
@@ -687,12 +682,6 @@ func bind[T any](_ T) any {
 	}
 }
 
-// The OAuth2 plugin is expected to be executed first, as it must ignore the user id stored
-// in the session (if there is a user id stored in session other plugins might return the user
-// object for that id).
-//
-// The Session plugin is expected to be executed second, in order to skip authentication
-// for users that have already signed in.
 func buildAuthGroup() *auth.Group {
 	group := auth.NewGroup(
 		&auth.OAuth2{},

services/auth/basic.go

@@ -15,6 +15,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/modules/web/middleware"
 )
 
@@ -132,11 +133,30 @@ func (b *Basic) Verify(req *http.Request, w http.ResponseWriter, store DataStore
 		return nil, err
 	}
 
-	if skipper, ok := source.Cfg.(LocalTwoFASkipper); ok && skipper.IsSkipLocalTwoFA() {
-		store.GetData()["SkipLocalTwoFA"] = true
+	if skipper, ok := source.Cfg.(LocalTwoFASkipper); !ok || !skipper.IsSkipLocalTwoFA() {
+		if err := validateTOTP(req, u); err != nil {
+			return nil, err
+		}
 	}
 
 	log.Trace("Basic Authorization: Logged in user %-v", u)
 
 	return u, nil
 }
+
+func validateTOTP(req *http.Request, u *user_model.User) error {
+	twofa, err := auth_model.GetTwoFactorByUID(u.ID)
+	if err != nil {
+		if auth_model.IsErrTwoFactorNotEnrolled(err) {
+			// No 2FA enrollment for this user
+			return nil
+		}
+		return err
+	}
+	if ok, err := twofa.ValidateTOTP(req.Header.Get("X-Gitea-OTP")); err != nil {
+		return err
+	} else if !ok {
+		return util.NewInvalidArgumentErrorf("invalid provided OTP")
+	}
+	return nil
+}

services/auth/middleware.go

@@ -7,7 +7,6 @@ import (
 	"net/http"
 	"strings"
 
-	"code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/log"
@@ -216,31 +215,6 @@ func VerifyAuthWithOptionsAPI(options *VerifyOptions) func(ctx *context.APIConte
 				})
 				return
 			}
-			if ctx.IsSigned && ctx.IsBasicAuth {
-				if skip, ok := ctx.Data["SkipLocalTwoFA"]; ok && skip.(bool) {
-					return // Skip 2FA
-				}
-				twofa, err := auth.GetTwoFactorByUID(ctx.Doer.ID)
-				if err != nil {
-					if auth.IsErrTwoFactorNotEnrolled(err) {
-						return // No 2FA enrollment for this user
-					}
-					ctx.InternalServerError(err)
-					return
-				}
-				otpHeader := ctx.Req.Header.Get("X-Gitea-OTP")
-				ok, err := twofa.ValidateTOTP(otpHeader)
-				if err != nil {
-					ctx.InternalServerError(err)
-					return
-				}
-				if !ok {
-					ctx.JSON(http.StatusForbidden, map[string]string{
-						"message": "Only signed in user is allowed to call APIs.",
-					})
-					return
-				}
-			}
 		}
 
 		if options.AdminRequired {

tests/integration/api_twofa_test.go

@@ -0,0 +1,54 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	auth_model "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/pquerna/otp/totp"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAPITwoFactor(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 16})
+
+	req := NewRequestf(t, "GET", "/api/v1/user")
+	req = AddBasicAuthHeader(req, user.Name)
+	MakeRequest(t, req, http.StatusOK)
+
+	otpKey, err := totp.Generate(totp.GenerateOpts{
+		SecretSize:  40,
+		Issuer:      "gitea-test",
+		AccountName: user.Name,
+	})
+	assert.NoError(t, err)
+
+	tfa := &auth_model.TwoFactor{
+		UID: user.ID,
+	}
+	assert.NoError(t, tfa.SetSecret(otpKey.Secret()))
+
+	assert.NoError(t, auth_model.NewTwoFactor(tfa))
+
+	req = NewRequestf(t, "GET", "/api/v1/user")
+	req = AddBasicAuthHeader(req, user.Name)
+	MakeRequest(t, req, http.StatusUnauthorized)
+
+	passcode, err := totp.GenerateCode(otpKey.Secret(), time.Now())
+	assert.NoError(t, err)
+
+	req = NewRequestf(t, "GET", "/api/v1/user")
+	req = AddBasicAuthHeader(req, user.Name)
+	req.Header.Set("X-Gitea-OTP", passcode)
+	MakeRequest(t, req, http.StatusOK)
+}