Remove Request Headers CORS Preflight Requirement

pkg/middlewares/headers/headers.go

@@ -221,13 +221,11 @@ func (s *Header) processCorsHeaders(rw http.ResponseWriter, req *http.Request) b
 	}
 
 	reqAcMethod := req.Header.Get("Access-Control-Request-Method")
-	reqAcHeaders := req.Header.Get("Access-Control-Request-Headers")
 	originHeader := req.Header.Get("Origin")
 
-	if reqAcMethod != "" && reqAcHeaders != "" && originHeader != "" && req.Method == http.MethodOptions {
+	if reqAcMethod != "" && originHeader != "" && req.Method == http.MethodOptions {
 		// If the request is an OPTIONS request with an Access-Control-Request-Method header,
-		// and Access-Control-Request-Headers headers, and Origin headers,
+		// and Origin headers, then it is a CORS preflight request,
-		// then it is a CORS preflight request,
 		// and we need to build a custom response: https://www.w3.org/TR/cors/#preflight-request
 		if s.headers.AccessControlAllowCredentials {
 			rw.Header().Set("Access-Control-Allow-Credentials", "true")

pkg/middlewares/headers/headers_test.go

@@ -275,6 +275,25 @@ func TestCORSPreflights(t *testing.T) {
 				"Access-Control-Allow-Headers": {"origin,X-Forwarded-For"},
 			},
 		},
+		{
+			desc: "No Request Headers Preflight",
+			header: NewHeader(emptyHandler, dynamic.Headers{
+				AccessControlAllowMethods: []string{"GET", "OPTIONS", "PUT"},
+				AccessControlAllowOrigin:  "*",
+				AccessControlAllowHeaders: []string{"origin", "X-Forwarded-For"},
+				AccessControlMaxAge:       600,
+			}),
+			requestHeaders: map[string][]string{
+				"Access-Control-Request-Method": {"GET", "OPTIONS"},
+				"Origin":                        {"https://foo.bar.org"},
+			},
+			expected: map[string][]string{
+				"Access-Control-Allow-Origin":  {"*"},
+				"Access-Control-Max-Age":       {"600"},
+				"Access-Control-Allow-Methods": {"GET,OPTIONS,PUT"},
+				"Access-Control-Allow-Headers": {"origin,X-Forwarded-For"},
+			},
+		},
 	}
 
 	for _, test := range testCases {