Add support for X-Forwarded-For header (e.g. if accessed via reverse proxy)

Author: Programie

config.sample.json

@@ -2,6 +2,7 @@
     "server": "localhost",
     "ttl": 60,
     "nsupdate_options": "-k /path/to/keyfile",
+    "trusted_proxies": ["172.18.0.2"],
     "users": {
         "myuser": {
             "password_hash": "$5$qS83kPfObw5$hOL2P9IwOdGXOIhyoy3hir5KN4YT7x2gauQMHSOHxv2",

index.php

@@ -1,6 +1,7 @@
 <?php
 use com\selfcoders\phpdyndns\config\Config;
 use com\selfcoders\phpdyndns\ErrorCode;
+use com\selfcoders\phpdyndns\IPUtils;
 use com\selfcoders\phpdyndns\NSUpdate;
 
 require_once __DIR__ . "/vendor/autoload.php";
@@ -38,7 +39,7 @@
 $username = $_GET["username"] ?? $_SERVER["PHP_AUTH_USER"] ?? null;
 $password = $_GET["password"] ?? $_SERVER["PHP_AUTH_PW"] ?? null;
 $hostname = $_GET["hostname"] ?? null;
-$ipAddress = $_GET["ipaddress"] ?? $_SERVER["REMOTE_ADDR"];
+$ipAddress = $_GET["ipaddress"] ?? IPUtils::getClientIP($config->trustedProxies);
 
 if ($username === null or $password === null) {
     header("WWW-Authenticate: Basic realm=\"DynDNS Update\"");

src/main/php/com/selfcoders/phpdyndns/IPUtils.php

@@ -0,0 +1,15 @@
+<?php
+namespace com\selfcoders\phpdyndns;
+
+class IPUtils
+{
+    public static function getClientIP($trustedProxies = [])
+    {
+        if (isset($_SERVER["X_FORWARDED_FOR"]) and in_array($_SERVER["REMOTE_ADDR"], $trustedProxies)) {
+            $ips = explode(",", $_SERVER["X_FORWARDED_FOR"]);
+            return trim(end($ips));
+        }
+
+        return $_SERVER["REMOTE_ADDR"];
+    }
+}

src/main/php/com/selfcoders/phpdyndns/config/Config.php

@@ -21,6 +21,10 @@ class Config
      * @var string
      */
     public $nsupdateOptions = "";
+    /**
+     * @var string[]
+     */
+    public $trustedProxies = [];
 
     /**
      * @param string $username
@@ -45,8 +49,19 @@ public function setUsers(array $users)
         }
     }
 
+    /**
+     * @param string $options
+     */
     public function setNsupdateOptions(string $options)
     {
         $this->nsupdateOptions = $options;
     }
+
+    /**
+     * @param string[] $ips
+     */
+    public function setTrustedProxies(array $ips)
+    {
+        $this->trustedProxies = $ips;
+    }
 }

src/test/php/com/selfcoders/phpdyndns/ConfigTest.php

@@ -36,6 +36,7 @@ public function testConfig(): void
         $this->assertEquals("localhost", $this->config->server);
         $this->assertEquals(60, $this->config->ttl);
         $this->assertEquals("-k /path/to/keyfile", $this->config->nsupdateOptions);
+        $this->assertEquals(["172.18.0.2"], $this->config->trustedProxies);
 
         $user = $this->config->getUser("myuser");