Unify two factor check (#27915) (#27929)

Backport #27915 by @KN4CK3R

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.

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

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
 		}
@@ -343,7 +339,6 @@ func reqBasicOrRevProxyAuth() func(ctx *context.APIContext) {
 			ctx.Error(http.StatusUnauthorized, "reqBasicAuth", "auth required")
 			return
 		}
-		ctx.CheckForOTP()
 	}
 }
 
@@ -700,12 +695,6 @@ 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{},
@@ -785,31 +774,6 @@ func verifyAuthWithOptions(options *common.VerifyOptions) func(ctx *context.APIC
 				})
 				return
 			}
-			if ctx.IsSigned && ctx.IsBasicAuth {
-				if skip, ok := ctx.Data["SkipLocalTwoFA"]; ok && skip.(bool) {
-					return // Skip 2FA
-				}
-				twofa, err := auth_model.GetTwoFactorByUID(ctx, ctx.Doer.ID)
-				if err != nil {
-					if auth_model.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 {