68 lines
1.7 KiB
Go
68 lines
1.7 KiB
Go
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// SPDX-License-Identifier: AGPL-3.0-or-later
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package middleware
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import (
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"context"
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"net"
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"net/http"
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"strings"
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)
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// RealIP extracts the real client IP from X-Forwarded-For, but only if the
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// direct connection comes from a trusted proxy. This is essential when Caddy
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// runs on a different machine (e.g. connected via WireGuard/Tailscale).
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func RealIP(trustedProxies []*net.IPNet) func(http.Handler) http.Handler {
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return func(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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ip := extractRealIP(r, trustedProxies)
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ctx := context.WithValue(r.Context(), realIPKey, ip)
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next.ServeHTTP(w, r.WithContext(ctx))
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})
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}
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}
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func extractRealIP(r *http.Request, trusted []*net.IPNet) string {
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// Get the direct connection IP.
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directIP, _, _ := net.SplitHostPort(r.RemoteAddr)
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if directIP == "" {
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directIP = r.RemoteAddr
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}
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// Only trust X-Forwarded-For if the direct connection is from a trusted proxy.
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if !isTrusted(directIP, trusted) {
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return directIP
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}
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// Parse X-Forwarded-For: client, proxy1, proxy2
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// The rightmost non-trusted IP is the real client.
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xff := r.Header.Get("X-Forwarded-For")
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if xff == "" {
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return directIP
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}
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ips := strings.Split(xff, ",")
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// Walk from right to left, finding the first non-trusted IP.
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for i := len(ips) - 1; i >= 0; i-- {
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ip := strings.TrimSpace(ips[i])
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if !isTrusted(ip, trusted) {
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return ip
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}
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}
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// All IPs in the chain are trusted; use the leftmost.
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return strings.TrimSpace(ips[0])
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}
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func isTrusted(ipStr string, nets []*net.IPNet) bool {
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ip := net.ParseIP(ipStr)
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if ip == nil {
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return false
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}
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for _, n := range nets {
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if n.Contains(ip) {
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return true
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}
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}
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return false
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}
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