Refactor CORS handler (go-gitea#28587)

The CORS code has been unmaintained for long time, and the behavior is
not correct.

This PR tries to improve it. The key point is written as comment in
code. And add more tests.

Fix go-gitea#28515
Fix go-gitea#27642
Fix go-gitea#17098

custom/conf/app.example.ini

@@ -1158,15 +1158,9 @@ LEVEL = Info
 ;; enable cors headers (disabled by default)
 ;ENABLED = false
 ;;
-;; scheme of allowed requests
-;SCHEME = http
-;;
-;; list of requesting domains that are allowed
+;; list of requesting origins that are allowed, eg: "https://*.example.com"
 ;ALLOW_DOMAIN = *
 ;;
-;; allow subdomains of headers listed above to request
-;ALLOW_SUBDOMAIN = false
-;;
 ;; list of methods allowed to request
 ;METHODS = GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS
 ;;

docs/content/administration/config-cheat-sheet.en-us.md

@@ -196,9 +196,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
 ## CORS (`cors`)
 
 - `ENABLED`: **false**: enable cors headers (disabled by default)
-- `SCHEME`: **http**: scheme of allowed requests
-- `ALLOW_DOMAIN`: **\***: list of requesting domains that are allowed
-- `ALLOW_SUBDOMAIN`: **false**: allow subdomains of headers listed above to request
+- `ALLOW_DOMAIN`: **\***: list of requesting origins that are allowed, eg: "https://*.example.com"
 - `METHODS`: **GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS**: list of methods allowed to request
 - `MAX_AGE`: **10m**: max time to cache response
 - `ALLOW_CREDENTIALS`: **false**: allow request with credentials

docs/content/administration/config-cheat-sheet.zh-cn.md

@@ -195,9 +195,7 @@ menu:
 ## 跨域 (`cors`)
 
 - `ENABLED`: **false**: 启用 CORS 头部（默认禁用）
-- `SCHEME`: **http**: 允许请求的协议
 - `ALLOW_DOMAIN`: **\***: 允许请求的域名列表
-- `ALLOW_SUBDOMAIN`: **false**: 允许上述列出的头部的子域名发出请求。
 - `METHODS`: **GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS**: 允许发起的请求方式列表
 - `MAX_AGE`: **10m**: 缓存响应的最大时间
 - `ALLOW_CREDENTIALS`: **false**: 允许带有凭据的请求

modules/public/public.go

@@ -33,7 +33,7 @@ func FileHandlerFunc() http.HandlerFunc {
 	assetFS := AssetFS()
 	return func(resp http.ResponseWriter, req *http.Request) {
 		if req.Method != "GET" && req.Method != "HEAD" {
-			resp.WriteHeader(http.StatusNotFound)
+			resp.WriteHeader(http.StatusMethodNotAllowed)
 			return
 		}
 		handleRequest(resp, req, assetFS, req.URL.Path)

modules/setting/cors.go

@@ -12,9 +12,7 @@ import (
 // CORSConfig defines CORS settings
 var CORSConfig = struct {
 	Enabled          bool
-	Scheme           string
-	AllowDomain      []string
-	AllowSubdomain   bool
+	AllowDomain      []string // FIXME: this option is from legacy code, it actually works as "AllowedOrigins". When refactoring in the future, the config option should also be renamed together.
 	Methods          []string
 	MaxAge           time.Duration
 	AllowCredentials bool

modules/web/route.go

@@ -101,16 +101,18 @@ func (r *Route) wrapMiddlewareAndHandler(h []any) ([]func(http.Handler) http.Han
 	return middlewares, handlerFunc
 }
 
-func (r *Route) Methods(method, pattern string, h ...any) {
+// Methods adds the same handlers for multiple http "methods" (separated by ",").
+// If any method is invalid, the lower level router will panic.
+func (r *Route) Methods(methods, pattern string, h ...any) {
 	middlewares, handlerFunc := r.wrapMiddlewareAndHandler(h)
 	fullPattern := r.getPattern(pattern)
-	if strings.Contains(method, ",") {
-		methods := strings.Split(method, ",")
+	if strings.Contains(methods, ",") {
+		methods := strings.Split(methods, ",")
 		for _, method := range methods {
 			r.R.With(middlewares...).Method(strings.TrimSpace(method), fullPattern, handlerFunc)
 		}
 	} else {
-		r.R.With(middlewares...).Method(method, fullPattern, handlerFunc)
+		r.R.With(middlewares...).Method(methods, fullPattern, handlerFunc)
 	}
 }
 
@@ -136,20 +138,6 @@ func (r *Route) Get(pattern string, h ...any) {
 	r.Methods("GET", pattern, h...)
 }
 
-func (r *Route) Options(pattern string, h ...any) {
-	r.Methods("OPTIONS", pattern, h...)
-}
-
-// GetOptions delegate get and options method
-func (r *Route) GetOptions(pattern string, h ...any) {
-	r.Methods("GET,OPTIONS", pattern, h...)
-}
-
-// PostOptions delegate post and options method
-func (r *Route) PostOptions(pattern string, h ...any) {
-	r.Methods("POST,OPTIONS", pattern, h...)
-}
-
 // Head delegate head method
 func (r *Route) Head(pattern string, h ...any) {
 	r.Methods("HEAD", pattern, h...)

routers/api/v1/api.go

@@ -822,9 +822,7 @@ func Routes() *web.Route {
 	m.Use(securityHeaders())
 	if setting.CORSConfig.Enabled {
 		m.Use(cors.Handler(cors.Options{
-			// Scheme:           setting.CORSConfig.Scheme, // FIXME: the cors middleware needs scheme option
-			AllowedOrigins: setting.CORSConfig.AllowDomain,
-			// setting.CORSConfig.AllowSubdomain // FIXME: the cors middleware needs allowSubdomain option
+			AllowedOrigins:   setting.CORSConfig.AllowDomain,
 			AllowedMethods:   setting.CORSConfig.Methods,
 			AllowCredentials: setting.CORSConfig.AllowCredentials,
 			AllowedHeaders:   append([]string{"Authorization", "X-Gitea-OTP"}, setting.CORSConfig.Headers...),

routers/web/githttp.go

@@ -28,16 +28,16 @@ func requireSignIn(ctx *context.Context) {
 
 func gitHTTPRouters(m *web.Route) {
 	m.Group("", func() {
-		m.PostOptions("/git-upload-pack", repo.ServiceUploadPack)
-		m.PostOptions("/git-receive-pack", repo.ServiceReceivePack)
-		m.GetOptions("/info/refs", repo.GetInfoRefs)
-		m.GetOptions("/HEAD", repo.GetTextFile("HEAD"))
-		m.GetOptions("/objects/info/alternates", repo.GetTextFile("objects/info/alternates"))
-		m.GetOptions("/objects/info/http-alternates", repo.GetTextFile("objects/info/http-alternates"))
-		m.GetOptions("/objects/info/packs", repo.GetInfoPacks)
-		m.GetOptions("/objects/info/{file:[^/]*}", repo.GetTextFile(""))
-		m.GetOptions("/objects/{head:[0-9a-f]{2}}/{hash:[0-9a-f]{38}}", repo.GetLooseObject)
-		m.GetOptions("/objects/pack/pack-{file:[0-9a-f]{40}}.pack", repo.GetPackFile)
-		m.GetOptions("/objects/pack/pack-{file:[0-9a-f]{40}}.idx", repo.GetIdxFile)
+		m.Methods("POST,OPTIONS", "/git-upload-pack", repo.ServiceUploadPack)
+		m.Methods("POST,OPTIONS", "/git-receive-pack", repo.ServiceReceivePack)
+		m.Methods("GET,OPTIONS", "/info/refs", repo.GetInfoRefs)
+		m.Methods("GET,OPTIONS", "/HEAD", repo.GetTextFile("HEAD"))
+		m.Methods("GET,OPTIONS", "/objects/info/alternates", repo.GetTextFile("objects/info/alternates"))
+		m.Methods("GET,OPTIONS", "/objects/info/http-alternates", repo.GetTextFile("objects/info/http-alternates"))
+		m.Methods("GET,OPTIONS", "/objects/info/packs", repo.GetInfoPacks)
+		m.Methods("GET,OPTIONS", "/objects/info/{file:[^/]*}", repo.GetTextFile(""))
+		m.Methods("GET,OPTIONS", "/objects/{head:[0-9a-f]{2}}/{hash:[0-9a-f]{38}}", repo.GetLooseObject)
+		m.Methods("GET,OPTIONS", "/objects/pack/pack-{file:[0-9a-f]{40}}.pack", repo.GetPackFile)
+		m.Methods("GET,OPTIONS", "/objects/pack/pack-{file:[0-9a-f]{40}}.idx", repo.GetIdxFile)
 	}, ignSignInAndCsrf, requireSignIn, repo.HTTPGitEnabledHandler, repo.CorsHandler(), context_service.UserAssignmentWeb())
 }

routers/web/misc/misc.go

@@ -33,10 +33,6 @@ func DummyOK(w http.ResponseWriter, req *http.Request) {
 	w.WriteHeader(http.StatusOK)
 }
 
-func DummyBadRequest(w http.ResponseWriter, req *http.Request) {
-	w.WriteHeader(http.StatusBadRequest)
-}
-
 func RobotsTxt(w http.ResponseWriter, req *http.Request) {
 	robotsTxt := util.FilePathJoinAbs(setting.CustomPath, "public/robots.txt")
 	if ok, _ := util.IsExist(robotsTxt); !ok {

routers/web/web.go

@@ -60,13 +60,12 @@ const (
 	GzipMinSize = 1400
 )
 
-// CorsHandler return a http handler who set CORS options if enabled by config
-func CorsHandler() func(next http.Handler) http.Handler {
+// optionsCorsHandler return a http handler which sets CORS options if enabled by config, it blocks non-CORS OPTIONS requests.
+func optionsCorsHandler() func(next http.Handler) http.Handler {
+	var corsHandler func(next http.Handler) http.Handler
 	if setting.CORSConfig.Enabled {
-		return cors.Handler(cors.Options{
-			// Scheme:           setting.CORSConfig.Scheme, // FIXME: the cors middleware needs scheme option
-			AllowedOrigins: setting.CORSConfig.AllowDomain,
-			// setting.CORSConfig.AllowSubdomain // FIXME: the cors middleware needs allowSubdomain option
+		corsHandler = cors.Handler(cors.Options{
+			AllowedOrigins:   setting.CORSConfig.AllowDomain,
 			AllowedMethods:   setting.CORSConfig.Methods,
 			AllowCredentials: setting.CORSConfig.AllowCredentials,
 			AllowedHeaders:   setting.CORSConfig.Headers,
@@ -75,7 +74,23 @@ func CorsHandler() func(next http.Handler) http.Handler {
 	}
 
 	return func(next http.Handler) http.Handler {
-		return next
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if r.Method == http.MethodOptions {
+				if corsHandler != nil && r.Header.Get("Access-Control-Request-Method") != "" {
+					corsHandler(next).ServeHTTP(w, r)
+				} else {
+					// it should explicitly deny OPTIONS requests if CORS handler is not executed, to avoid the next GET/POST handler being incorrectly called by the OPTIONS request
+					w.WriteHeader(http.StatusMethodNotAllowed)
+				}
+				return
+			}
+			// for non-OPTIONS requests, call the CORS handler to add some related headers like "Vary"
+			if corsHandler != nil {
+				corsHandler(next).ServeHTTP(w, r)
+			} else {
+				next.ServeHTTP(w, r)
+			}
+		})
 	}
 }
 
@@ -218,7 +233,7 @@ func Routes() *web.Route {
 	routes := web.NewRoute()
 
 	routes.Head("/", misc.DummyOK) // for health check - doesn't need to be passed through gzip handler
-	routes.Methods("GET, HEAD", "/assets/*", CorsHandler(), public.FileHandlerFunc())
+	routes.Methods("GET, HEAD, OPTIONS", "/assets/*", optionsCorsHandler(), public.FileHandlerFunc())
 	routes.Methods("GET, HEAD", "/avatars/*", storageHandler(setting.Avatar.Storage, "avatars", storage.Avatars))
 	routes.Methods("GET, HEAD", "/repo-avatars/*", storageHandler(setting.RepoAvatar.Storage, "repo-avatars", storage.RepoAvatars))
 	routes.Methods("GET, HEAD", "/apple-touch-icon.png", misc.StaticRedirect("/assets/img/apple-touch-icon.png"))
@@ -458,8 +473,8 @@ func registerRoutes(m *web.Route) {
 		m.Get("/change-password", func(ctx *context.Context) {
 			ctx.Redirect(setting.AppSubURL + "/user/settings/account")
 		})
-		m.Any("/*", CorsHandler(), public.FileHandlerFunc())
-	}, CorsHandler())
+		m.Methods("GET, HEAD", "/*", public.FileHandlerFunc())
+	}, optionsCorsHandler())
 
 	m.Group("/explore", func() {
 		m.Get("", func(ctx *context.Context) {
@@ -532,14 +547,11 @@ func registerRoutes(m *web.Route) {
 		// TODO manage redirection
 		m.Post("/authorize", web.Bind(forms.AuthorizationForm{}), auth.AuthorizeOAuth)
 	}, ignSignInAndCsrf, reqSignIn)
-	m.Options("/login/oauth/userinfo", CorsHandler(), misc.DummyBadRequest)
-	m.Get("/login/oauth/userinfo", ignSignInAndCsrf, auth.InfoOAuth)
-	m.Options("/login/oauth/access_token", CorsHandler(), misc.DummyBadRequest)
-	m.Post("/login/oauth/access_token", CorsHandler(), web.Bind(forms.AccessTokenForm{}), ignSignInAndCsrf, auth.AccessTokenOAuth)
-	m.Options("/login/oauth/keys", CorsHandler(), misc.DummyBadRequest)
-	m.Get("/login/oauth/keys", ignSignInAndCsrf, auth.OIDCKeys)
-	m.Options("/login/oauth/introspect", CorsHandler(), misc.DummyBadRequest)
-	m.Post("/login/oauth/introspect", CorsHandler(), web.Bind(forms.IntrospectTokenForm{}), ignSignInAndCsrf, auth.IntrospectOAuth)
+
+	m.Methods("GET, OPTIONS", "/login/oauth/userinfo", optionsCorsHandler(), ignSignInAndCsrf, auth.InfoOAuth)
+	m.Methods("POST, OPTIONS", "/login/oauth/access_token", optionsCorsHandler(), web.Bind(forms.AccessTokenForm{}), ignSignInAndCsrf, auth.AccessTokenOAuth)
+	m.Methods("GET, OPTIONS", "/login/oauth/keys", optionsCorsHandler(), ignSignInAndCsrf, auth.OIDCKeys)
+	m.Methods("POST, OPTIONS", "/login/oauth/introspect", optionsCorsHandler(), web.Bind(forms.IntrospectTokenForm{}), ignSignInAndCsrf, auth.IntrospectOAuth)
 
 	m.Group("/user/settings", func() {
 		m.Get("", user_setting.Profile)
@@ -770,7 +782,7 @@ func registerRoutes(m *web.Route) {
 
 	m.Group("", func() {
 		m.Get("/{username}", user.UsernameSubRoute)
-		m.Get("/attachments/{uuid}", repo.GetAttachment)
+		m.Methods("GET, OPTIONS", "/attachments/{uuid}", optionsCorsHandler(), repo.GetAttachment)
 	}, ignSignIn)
 
 	m.Post("/{username}", reqSignIn, context_service.UserAssignmentWeb(), user.Action)

tests/integration/cors_test.go

@@ -7,17 +7,88 @@ import (
 	"net/http"
 	"testing"
 
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
+	"code.gitea.io/gitea/routers"
 	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
 )
 
-func TestCORSNotSet(t *testing.T) {
+func TestCORS(t *testing.T) {
 	defer tests.PrepareTestEnv(t)()
-	req := NewRequest(t, "GET", "/api/v1/version")
-	session := loginUser(t, "user2")
-	resp := session.MakeRequest(t, req, http.StatusOK)
-	assert.Equal(t, resp.Code, http.StatusOK)
-	corsHeader := resp.Header().Get("Access-Control-Allow-Origin")
-	assert.Empty(t, corsHeader, "Access-Control-Allow-Origin: generated header should match") // header not set
+	t.Run("CORS enabled", func(t *testing.T) {
+		defer test.MockVariableValue(&setting.CORSConfig.Enabled, true)()
+		defer test.MockVariableValue(&testWebRoutes, routers.NormalRoutes())()
+
+		t.Run("API with CORS", func(t *testing.T) {
+			// GET api with no CORS header
+			req := NewRequest(t, "GET", "/api/v1/version")
+			resp := MakeRequest(t, req, http.StatusOK)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Contains(t, resp.Header().Values("Vary"), "Origin")
+
+			// OPTIONS api for CORS
+			req = NewRequest(t, "OPTIONS", "/api/v1/version").
+				SetHeader("Origin", "https://example.com").
+				SetHeader("Access-Control-Request-Method", "GET")
+			resp = MakeRequest(t, req, http.StatusOK)
+			assert.NotEmpty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Contains(t, resp.Header().Values("Vary"), "Origin")
+		})
+
+		t.Run("Web with CORS", func(t *testing.T) {
+			// GET userinfo with no CORS header
+			req := NewRequest(t, "GET", "/login/oauth/userinfo")
+			resp := MakeRequest(t, req, http.StatusUnauthorized)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Contains(t, resp.Header().Values("Vary"), "Origin")
+
+			// OPTIONS userinfo for CORS
+			req = NewRequest(t, "OPTIONS", "/login/oauth/userinfo").
+				SetHeader("Origin", "https://example.com").
+				SetHeader("Access-Control-Request-Method", "GET")
+			resp = MakeRequest(t, req, http.StatusOK)
+			assert.NotEmpty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Contains(t, resp.Header().Values("Vary"), "Origin")
+
+			// OPTIONS userinfo for non-CORS
+			req = NewRequest(t, "OPTIONS", "/login/oauth/userinfo")
+			resp = MakeRequest(t, req, http.StatusMethodNotAllowed)
+			assert.NotContains(t, resp.Header().Values("Vary"), "Origin")
+		})
+	})
+
+	t.Run("CORS disabled", func(t *testing.T) {
+		defer test.MockVariableValue(&setting.CORSConfig.Enabled, false)()
+		defer test.MockVariableValue(&testWebRoutes, routers.NormalRoutes())()
+
+		t.Run("API without CORS", func(t *testing.T) {
+			req := NewRequest(t, "GET", "/api/v1/version")
+			resp := MakeRequest(t, req, http.StatusOK)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Empty(t, resp.Header().Values("Vary"))
+
+			req = NewRequest(t, "OPTIONS", "/api/v1/version").
+				SetHeader("Origin", "https://example.com").
+				SetHeader("Access-Control-Request-Method", "GET")
+			resp = MakeRequest(t, req, http.StatusMethodNotAllowed)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.Empty(t, resp.Header().Values("Vary"))
+		})
+
+		t.Run("Web without CORS", func(t *testing.T) {
+			req := NewRequest(t, "GET", "/login/oauth/userinfo")
+			resp := MakeRequest(t, req, http.StatusUnauthorized)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.NotContains(t, resp.Header().Values("Vary"), "Origin")
+
+			req = NewRequest(t, "OPTIONS", "/login/oauth/userinfo").
+				SetHeader("Origin", "https://example.com").
+				SetHeader("Access-Control-Request-Method", "GET")
+			resp = MakeRequest(t, req, http.StatusMethodNotAllowed)
+			assert.Empty(t, resp.Header().Get("Access-Control-Allow-Origin"))
+			assert.NotContains(t, resp.Header().Values("Vary"), "Origin")
+		})
+	})
 }