Shorten and simplify path to CORS proxy (#2063)

## Motivation for the change, related issues

The CORS proxy URL is long and requires the user to remember a specific
PHP file path.
```
https://wordpress-playground-cors-proxy.net/cors-proxy.php
```

Let's shorten the URL and let people forget the PHP file name. With this
PR,

`https://wordpress-playground-cors-proxy.net/cors-proxy.php?https://example.com/`
can be replaced with
`https://wordpress-playground-cors-proxy.net/?https://example.com/`
or
`https://wordpress-playground-cors-proxy.net/https://example.com/`

## Implementation details

Instead of trying to derive the target URL by removing
`$_SERVER['SCRIPT_NAME']` from `$_SERVER['REQUEST_URI']`, we switch to
taking the target URL from `$_SERVER['PATH_INFO']` or
`$_SERVER['QUERY_STRING']`.

In addition, we take advantage of WP Cloud's default script path and
have that script define PATH_INFO if it doesn't exist. It shouldn't
exist because WP Cloud isn't configured to provide path info today.
(`$_SERVER['PATH_INFO']` === `/additional/info` when
`$_SERVER['REQUEST_URI']` === '/path-to-script.php/additional/info').

## Testing Instructions (or ideally a Blueprint)

- Run unit tests from php-cors-proxy dir with `sh test.sh`
- Run CORS proxy deploy workflow and test manually with proxy site. The
following proxy URLs should all work:
-
https://wordpress-playground-cors-proxy.net/cors-proxy.php?https://wordpress.org/
- https://wordpress-playground-cors-proxy.net/?https://wordpress.org/
    - https://wordpress-playground-cors-proxy.net/https://wordpress.org/

packages/playground/php-cors-proxy-deployment/__wp__/index.php

@@ -0,0 +1,11 @@
+<?php
+
+if (
+        empty( $_SERVER['PATH_INFO'] ) &&           
+        !str_starts_with($_SERVER['REQUEST_URI'], '/?')
+) {                                                 
+        // Allow proxied URL to be provided via request URI,
+        // even though WP cloud servers don't provided PATH_INFO.
+        $_SERVER['PATH_INFO'] = $_SERVER['REQUEST_URI'];
+}
+require __DIR__ . '/../cors-proxy.php';

packages/playground/php-cors-proxy-deployment/apply-update.sh

@@ -9,6 +9,7 @@ SITE_API_BASE="$( "$SITE_PHP" -r 'require "/scripts/env.php"; echo SITE_API_BASE
 
 echo Adding config file to updated proxy files
 cp ~/cors-proxy-deployment/cors-proxy-config.php ~/updated-proxy-files/
+cp -R ~/cors-proxy-deployment/__wp__ ~/updated-proxy-files/
 
 echo Syncing staged files to production
 rsync -av --delete --no-perms --omit-dir-times ~/updated-proxy-files/ /srv/htdocs/

packages/playground/php-cors-proxy/cors-proxy-functions.php

@@ -8,21 +8,18 @@ function get_target_url($server_data=null) {
     if ($server_data === null) {
         $server_data = $_SERVER;
     }
-    $requestUri = $server_data['REQUEST_URI'];
-    $targetUrl = $requestUri;
 
-    // Remove the current script name from the beginning of $targetUrl
-    if (strpos($targetUrl, $server_data['SCRIPT_NAME']) === 0) {
-        $targetUrl = substr($targetUrl, strlen($server_data['SCRIPT_NAME']));
+    $path_info = $server_data['PATH_INFO'] ?? '';
+    if (str_starts_with($path_info, '/') && strlen($path_info) > 1) {
+        return substr($path_info, 1);
     }
 
-    // Remove the leading slash or question mark, depending on the method
-    // used to access the script
-    if (str_starts_with($targetUrl, '/') || str_starts_with($targetUrl, '?')) {
-        $targetUrl = substr($targetUrl, 1);
+    $query_string = $server_data['QUERY_STRING'] ?? '';
+    if (!empty($server_data['QUERY_STRING'])) {
+        return $query_string;
     }
 
-    return $targetUrl;
+    return false;
 }
 
 function get_current_script_uri($targetUrl, $request_uri)

packages/playground/php-cors-proxy/cors-proxy.php

@@ -61,7 +61,15 @@
     echo "Bad Request\n\nNo URL provided";
     exit;
 }
-$resolved = url_validate_and_resolve($targetUrl);
+
+try {
+    $resolved = url_validate_and_resolve($targetUrl);
+} catch (CorsProxyException $e) {
+    http_response_code(400);
+    echo "Bad Request\n\n" . $e->getMessage();
+    exit;
+}
+
 $host = $resolved['host'];
 $resolvedIp = $resolved['ip'];
 

packages/playground/php-cors-proxy/tests/ProxyFunctionsTests.php

@@ -84,20 +84,48 @@ public function testGetTargetUrl($server_data, $expected_target_url)
 
     static public function providerGetTargetUrl() {
         return [
-            'Simple request' => [
+            'Request with server-provided PATH_INFO' => [
                 [
-                    'REQUEST_URI' => '/cors-proxy/proxy.php/http://example.com',
-                    'SCRIPT_NAME' => '/cors-proxy/proxy.php',
+                    'PATH_INFO' => '/http://example.com',
                 ],
                 'http://example.com'
             ],
-            'Request with query params' => [
+            'Request with server-provided single-slash PATH_INFO' => [
                 [
-                    'REQUEST_URI' => '/cors-proxy/proxy.php/http://example.com?test=1',
-                    'SCRIPT_NAME' => '/cors-proxy/proxy.php',
+                    'PATH_INFO' => '/',
                 ],
-                'http://example.com?test=1'
-            ]
+                false,
+            ],
+            'Request with server-provided empty PATH_INFO' => [
+                [
+                    'PATH_INFO' => '',
+                ],
+                false,
+            ],
+            'Request with server-provided PATH_INFO and QUERY_STRING' => [
+                [
+                    'PATH_INFO' => '/http://example.com/from-path-info',
+                    'QUERY_STRING' => 'http://example.com/from-query-string',
+                ],
+                'http://example.com/from-path-info'
+            ],
+            'Request with server-provided slash PATH_INFO and QUERY_STRING' => [
+                [
+                    'PATH_INFO' => '/',
+                    'QUERY_STRING' => 'http://example.com/from-query-string',
+                ],
+                'http://example.com/from-query-string'
+            ],
+            'Request with just query params' => [
+                [
+                    'QUERY_STRING' => 'http://example.com/from-query-string',
+                ],
+                'http://example.com/from-query-string'
+            ],
+            'Request with neither PATH_INFO nor QUERY_STRING' => [
+                [],
+                false
+            ],
         ];
     }
     public function testGetCurrentScriptUri()