feat: add Internet-Only captcha rule (#3919)

util/network.go

@@ -0,0 +1,47 @@
+// Copyright 2025 The Casdoor Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"net"
+)
+
+func IsInternetIp(ip string) bool {
+	ipStr, _, err := net.SplitHostPort(ip)
+	if err != nil {
+		ipStr = ip
+	}
+
+	parsedIP := net.ParseIP(ipStr)
+	if parsedIP == nil {
+		return false
+	}
+
+	return !parsedIP.IsPrivate() && !parsedIP.IsLoopback() && !parsedIP.IsMulticast() && !parsedIP.IsUnspecified()
+}
+
+func IsHostIntranet(ip string) bool {
+	ipStr, _, err := net.SplitHostPort(ip)
+	if err != nil {
+		ipStr = ip
+	}
+
+	parsedIP := net.ParseIP(ipStr)
+	if parsedIP == nil {
+		return false
+	}
+
+	return parsedIP.IsPrivate() || parsedIP.IsLoopback() || parsedIP.IsLinkLocalUnicast() || parsedIP.IsLinkLocalMulticast()
+}