Refactor CORS handler (#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 #28515
Fix #27642
Fix #17098

1 files changed, 78 insertions, 7 deletions

diff --git a/tests/integration/cors_test.go b/tests/integration/cors_test.go
index 83d200402c..25dfbabf41 100644
--- a/tests/integration/cors_test.go
+++ b/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")
+		})
+	})
 }