Feature: Practical URL Parameter Encryption

.gitignore

@@ -232,6 +232,7 @@ config/*
 !config/nginx.conf
 !config/php-fpm.conf
 !config/php.ini
+docker-compose.*
 
 ######################
 ## VisualStudioCode ##

actions/DisplayAction.php

@@ -169,7 +169,7 @@ private function createResponse(Request $request, BridgeAbstract $bridge, string
             'last-modified' => gmdate('D, d M Y H:i:s ', $now) . 'GMT',
             'content-type'  => $format->getMimeType() . '; charset=' . $format->getCharset(),
         ];
-        return new Response($format->stringify(), 200, $headers);
+        return new Response($format->stringify($request), 200, $headers);
     }
 
     private function createFeedItemFromException($e, BridgeAbstract $bridge): FeedItem

config.default.ini.php

@@ -27,6 +27,16 @@
 ;enabled_bridges[] = YouTubeCommunityTabBridge
 enabled_bridges[] = *
 
+; Encrypted URL key. A random string between 16 and 64 characters long which is used to generate
+;   compressed and encrypted feed URLs, to keep private information secret.
+;
+; NEVER SHARE THIS KEY.
+; A password generator should be used to create this string. Whitespace is NOT ALLOWED.
+;
+; If this value is empty (default), then encrypted URLs cannot be used.
+;   Example key (DO NOT USE THIS): "b3c7@hsLqk)P(SJvjCBDUy]GMg6RamdHxEWV8K9nA4QN.p_5"
+enc_url_key = ""
+
 ; Defines the timezone used by RSS-Bridge
 ; Find a list of supported timezones at
 ; https://www.php.net/manual/en/timezones.php

formats/AtomFormat.php

@@ -14,7 +14,7 @@ class AtomFormat extends FormatAbstract
     protected const ATOM_NS = 'http://www.w3.org/2005/Atom';
     protected const MRSS_NS = 'http://search.yahoo.com/mrss/';
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         $document = new \DomDocument('1.0', $this->getCharset());
         $document->formatOutput = true;

formats/HtmlFormat.php

@@ -4,7 +4,7 @@ class HtmlFormat extends FormatAbstract
 {
     const MIME_TYPE = 'text/html';
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         // This query string is url encoded
         $queryString = $_SERVER['QUERY_STRING'];
@@ -13,14 +13,27 @@ public function stringify()
         $formatFactory = new FormatFactory();
         $formats = [];
 
+        if (str_contains(strtolower($queryString), strtolower(UrlEncryptionService::PARAMETER_NAME . '='))) {
+            $encryptionToken = 'yes';
+        } else {
+            $encryptionToken = null;
+        }
+
         // Create all formats (except HTML)
         $formatNames = $formatFactory->getFormatNames();
         foreach ($formatNames as $formatName) {
             if ($formatName === 'Html') {
                 continue;
             }
             // The format url is relative, but should be absolute in order to help feed readers.
-            $formatUrl = '?' . str_ireplace('format=Html', 'format=' . $formatName, $queryString);
+            if (str_contains(strtolower($queryString), 'format=html')) {
+                $formatUrl = '?' . str_ireplace('format=Html', 'format=' . $formatName, $queryString);
+            } else {
+                // If we're viewing the HtmlFormat and the 'format' GET parameter isn't here, this is likely an
+                //   encrypted URL being viewed. Handle this by reconstructing the raw URL with the new format.
+                $formatUrl = '?' . http_build_query($request->toArray());
+                $formatUrl .= (strlen($formatUrl) > 1 ? '&' : '') . 'format=' . $formatName;
+            }
             $formatObject = $formatFactory->create($formatName);
             $formats[] = [
                 'url'       => $formatUrl,
@@ -48,12 +61,14 @@ public function stringify()
         }
 
         $html = render_template(__DIR__ . '/../templates/html-format.html.php', [
-            'charset'       => $this->getCharset(),
-            'title'         => $feedArray['name'],
-            'formats'       => $formats,
-            'uri'           => $feedArray['uri'],
-            'items'         => $items,
-            'donation_uri'  => $donationUri,
+            'charset'          => $this->getCharset(),
+            'title'            => $feedArray['name'],
+            'formats'          => $formats,
+            'uri'              => $feedArray['uri'],
+            'items'            => $items,
+            'donation_uri'     => $donationUri,
+            'encryption_token' => $encryptionToken,
+            'bridge_name'      => $request->get('bridge'),
         ]);
         // Remove invalid characters
         ini_set('mbstring.substitute_character', 'none');

formats/JsonFormat.php

@@ -23,7 +23,7 @@ class JsonFormat extends FormatAbstract
         'uid',
     ];
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         $feedArray = $this->getFeed();
 

formats/MrssFormat.php

@@ -32,7 +32,7 @@ class MrssFormat extends FormatAbstract
     protected const ATOM_NS = 'http://www.w3.org/2005/Atom';
     protected const MRSS_NS = 'http://search.yahoo.com/mrss/';
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         $document = new \DomDocument('1.0', $this->getCharset());
         $document->formatOutput = true;

formats/PlaintextFormat.php

@@ -4,7 +4,7 @@ class PlaintextFormat extends FormatAbstract
 {
     const MIME_TYPE = 'text/plain';
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         $feed = $this->getFeed();
         foreach ($this->getItems() as $item) {

formats/SfeedFormat.php

@@ -4,7 +4,7 @@ class SfeedFormat extends FormatAbstract
 {
     const MIME_TYPE = 'text/plain';
 
-    public function stringify()
+    public function stringify(?Request $request)
     {
         $text = '';
         foreach ($this->getItems() as $item) {

lib/BridgeAbstract.php

@@ -104,9 +104,27 @@ public function getMaintainer(): string
     /**
      * A more correct method name would have been "getContexts"
      */
-    public function getParameters(): array
+    final public function getParameters(): array
     {
-        return static::PARAMETERS;
+        $parameters = static::PARAMETERS;
+
+        if (UrlEncryptionService::enabled()) {
+            // A parameter cannot be defined which collides with the special encryption parameter.
+            $illegalToken = array_key_exists(UrlEncryptionService::PARAMETER_NAME, $parameters);
+            foreach ($parameters as $k => $v) {
+                $illegalToken |= array_key_exists(UrlEncryptionService::PARAMETER_NAME, $v);
+            }
+
+            if ($illegalToken) {
+                throw new \Exception(
+                    'The parameter name "' . UrlEncryptionService::PARAMETER_NAME
+                    . '" is reserved for encrypted URLs. Remove this from the PARAMETERS definition in bridge "'
+                    . $this->getName() . '".'
+                );
+            }
+        }
+
+        return $parameters;
     }
 
     public function getItems()

lib/FormatAbstract.php

@@ -12,7 +12,7 @@ abstract class FormatAbstract
 
     protected array $feed = [];
 
-    abstract public function stringify();
+    abstract public function stringify(?Request $request);
 
     public function setFeed(array $feed)
     {

lib/ParameterValidator.php

@@ -10,7 +10,13 @@ public function validateInput(array &$input, $contexts): array
         $errors = [];
 
         foreach ($input as $name => $value) {
+            if ($name === UrlEncryptionService::PARAMETER_NAME && UrlEncryptionService::enabled()) {
+                // Do not validate against encrypted URL tokens.
+                continue;
+            }
+
             $registered = false;
+
             foreach ($contexts as $contextName => $contextParameters) {
                 if (!array_key_exists($name, $contextParameters)) {
                     continue;

lib/RssBridge.php

@@ -18,28 +18,22 @@ public function __construct(
 
     public function main(array $argv = []): Response
     {
-        if ($argv) {
-            parse_str(implode('&', array_slice($argv, 1)), $cliArgs);
-            $request = Request::fromCli($cliArgs);
-        } else {
-            $request = Request::fromGlobals();
-        }
-
-        foreach ($request->toArray() as $key => $value) {
-            if (!is_string($value)) {
-                return new Response(render(__DIR__ . '/../templates/error.html.php', [
-                    'message' => "Query parameter \"$key\" is not a string.",
-                ]), 400);
-            }
-        }
-
+        // The check for maintenance mode should always occur first since it has no
+        //   dependencies, and nothing else needs to come before it for bootstrapping.
         if (Configuration::getConfig('system', 'enable_maintenance_mode')) {
             return new Response(render(__DIR__ . '/../templates/error.html.php', [
                 'title'     => '503 Service Unavailable',
                 'message'   => 'RSS-Bridge is down for maintenance.',
             ]), 503);
         }
 
+        if ($argv) {
+            parse_str(implode('&', array_slice($argv, 1)), $cliArgs);
+            $request = Request::fromCli($cliArgs);
+        } else {
+            $request = Request::fromGlobals();
+        }
+
         // HTTP Basic auth check
         if (Configuration::getConfig('authentication', 'enable')) {
             if (Configuration::getConfig('authentication', 'password') === '') {
@@ -65,6 +59,33 @@ public function main(array $argv = []): Response
             // At this point the username and password was correct
         }
 
+        // If the URL contains an encrypted token, then the rest of the current URL
+        //   parameters are discarded and the encrypted token is decrypted, decompressed,
+        //   and expanded into the Request object's 'get' container. The user should NEVER
+        //   be redirected to another URL that would expose what params that are in the
+        //   current page.
+        if (
+            $request->get(UrlEncryptionService::PARAMETER_NAME)
+            && UrlEncryptionService::enabled()
+        ) {
+            try {
+                $request->tryDecryptUrl();
+            } catch (\Exception $e) {
+                return new Response(
+                    render(__DIR__ . '/../templates/error.html.php', ['message' => $e->getMessage()]),
+                    401
+                );
+            }
+        }
+
+        foreach ($request->toArray() as $key => $value) {
+            if (!is_string($value)) {
+                return new Response(render(__DIR__ . '/../templates/error.html.php', [
+                    'message' => "Query parameter \"$key\" is not a string.",
+                ]), 400);
+            }
+        }
+
         // Add token as attribute to request
         $request = $request->withAttribute('token', $request->get('token'));