[RedditBridge] Use OAuth2 token and endpoint for accessing the JSON API

bridges/RedditBridge.php

@@ -3,7 +3,10 @@
 /**
  * This bridge does NOT use reddit's official rss feeds.
  *
- * This bridge uses reddit's json api: https://old.reddit.com/search.json?q=
+ * This bridge uses Reddit's JSON API.
+ *
+ * It uses the legacy unauthenticated API by default.
+ * Configure both `app_id` and `app_secret` to use OAuth2 instead.
  */
 class RedditBridge extends BridgeAbstract
 {
@@ -13,6 +16,15 @@ class RedditBridge extends BridgeAbstract
     const CACHE_TIMEOUT = 60 * 60 * 2; // 2h
     const DESCRIPTION = 'Return hot submissions from Reddit';
 
+    const CONFIGURATION = [
+        'app_id' => [
+            'required' => false,
+        ],
+        'app_secret' => [
+            'required' => false,
+        ],
+    ];
+
     const PARAMETERS = [
         'global' => [
             'score' => [
@@ -112,6 +124,8 @@ class RedditBridge extends BridgeAbstract
         ]
     ];
 
+    private ?RedditClient $redditClient = null;
+
     public function collectData()
     {
         $forbiddenKey = 'reddit_forbidden';
@@ -167,17 +181,14 @@ private function collectDataInternal(): void
 
         $search = $this->getInput('search');
         $flareInput = $this->getInput('f');
+        $min_score = $this->getInput('score');
+        $min_comments = $this->getInput('min_comments');
 
         foreach ($subreddits as $subreddit) {
-            $version = 'v0.0.2';
-            $useragent = "rss-bridge $version (https://github.com/RSS-Bridge/rss-bridge)";
-            $url = self::createUrl($search, $flareInput, $subreddit, $user, $section, $time, $this->queriedContext);
+            $parameters = self::createSearchParameters($search, $flareInput, $subreddit, $user, $section, $time, $this->queriedContext);
+            $response = $this->getRedditClient()->search($parameters);
 
-            $response = getContents($url, ['User-Agent: ' . $useragent], [], true);
-
-            $json = $response->getBody();
-
-            $parsedJson = Json::decode($json, false);
+            $parsedJson = Json::decode($response->getBody(), false);
 
             foreach ($parsedJson->data->children as $post) {
                 if ($post->kind == 't1' && !$comments) {
@@ -186,8 +197,6 @@ private function collectDataInternal(): void
 
                 $data = $post->data;
 
-                $min_score = $this->getInput('score');
-                $min_comments = $this->getInput('min_comments');
                 if ($min_score >= 0 && $min_comments >= 0) {
                     if ($data->num_comments < $min_comments || $data->score < $min_score) {
                         continue;
@@ -299,7 +308,7 @@ private function collectDataInternal(): void
         });
     }
 
-    public static function createUrl($search, $flareInput, $subreddit, bool $user, $section, $time, $queriedContext): string
+    private static function createSearchParameters($search, $flareInput, $subreddit, bool $user, $section, $time, $queriedContext): array
     {
         $keywords = '';
 
@@ -316,13 +325,12 @@ public static function createUrl($search, $flareInput, $subreddit, bool $user, $
             $flair = '';
         }
         $name = trim($subreddit);
-        $query = [
+        return [
             'q' => $keywords . $flair . ($user ? 'author:' : 'subreddit:') . $name,
             'sort' => $section,
             'include_over_18' => 'on',
             't' => $time
         ];
-        return 'https://old.reddit.com/search.json?' . http_build_query($query);
     }
 
     public function getIcon()
@@ -397,4 +405,16 @@ public function detectParameters($url)
             return null;
         }
     }
+
+    private function getRedditClient(): RedditClient
+    {
+        if ($this->redditClient === null) {
+            $this->redditClient = new RedditClient(
+                $this->cache,
+                $this->getOption('app_id'),
+                $this->getOption('app_secret')
+            );
+        }
+        return $this->redditClient;
+    }
 }

docs/10_Bridge_Specific/Reddit.md

@@ -0,0 +1,35 @@
+RedditBridge
+============
+
+Since Reddit shut down unauthorized JSON API access:
+https://www.reddit.com/r/modnews/comments/1tq9vxo/protecting_communities_from_scrapers_and_platform/
+
+Unfortunately, Reddit also blocked "easy" setup for developer apps:
+https://old.reddit.com/wiki/api#wiki_read_the_full_api_terms_and_sign_up_for_usage
+
+The bridge uses Reddit's legacy unauthenticated endpoint by default.
+To use Reddit's OAuth2 API instead, configure both credentials below.
+
+If you want to use the OAuth2 API, you need to either:
+
+ - Submit a request for an app using Reddit's Data API **and somehow get it approved by Reddit**.
+
+ - Already have an existing app - they still seem to work.
+
+In both cases you need to have a private "script" app and its "id" and "secret":
+https://old.reddit.com/prefs/apps
+
+"Id" should be visible right in the base view; secret is available when selecting "edit".
+
+You'll also need a private RSS-Bridge instance to set up your own configuration.
+
+In `config.ini.php` add the following configuration:
+
+```ini
+[RedditBridge]
+app_id = "<ID>"
+app_secret = "<secret>"
+```
+
+The bridge will handle OAuth, refresh bearer, etc., if both `app_id` and `app_secret` are configured.
+If either, or both, are missing, then the bridge falls back to legacy unauthenticated access.

lib/RedditClient.php

@@ -0,0 +1,94 @@
+<?php
+
+class RedditClient
+{
+    private const LEGACY_API_URI = 'https://old.reddit.com';
+    private const OAUTH_API_URI = 'https://oauth.reddit.com';
+    private const OAUTH_TOKEN_KEY = 'reddit_oauth_token';
+    private const VERSION = 'v0.0.3';
+    private const USER_AGENT = 'rss-bridge ' . self::VERSION . ' (https://github.com/RSS-Bridge/rss-bridge)';
+
+    private CacheInterface $cache;
+    private ?string $appId;
+    private ?string $appSecret;
+
+    public function __construct(CacheInterface $cache, ?string $appId = null, ?string $appSecret = null)
+    {
+        $this->cache = $cache;
+        $this->appId = $appId === '' ? null : $appId;
+        $this->appSecret = $appSecret === '' ? null : $appSecret;
+    }
+
+    public function search(array $parameters): Response
+    {
+        if ($this->appId === null || $this->appSecret === null) {
+            return $this->searchUnauthenticated($parameters);
+        }
+        return $this->searchAuthenticated($parameters);
+    }
+
+    private function searchUnauthenticated(array $parameters): Response
+    {
+        $url = self::createSearchUrl(self::LEGACY_API_URI, $parameters);
+        return getContents($url, ['User-Agent: ' . self::USER_AGENT], [], true);
+    }
+
+    private function searchAuthenticated(array $parameters): Response
+    {
+        $url = self::createSearchUrl(self::OAUTH_API_URI, $parameters);
+        try {
+            return $this->requestAuthenticated($url);
+        } catch (HttpException $e) {
+            if ($e->getCode() !== 401 && $e->getCode() !== 403) {
+                throw $e;
+            }
+            $this->cache->delete(self::OAUTH_TOKEN_KEY);
+            return $this->requestAuthenticated($url);
+        }
+    }
+
+    private function requestAuthenticated(string $url): Response
+    {
+        $headers = [
+            'User-Agent: ' . self::USER_AGENT,
+            'Authorization: Bearer ' . $this->getAccessToken(),
+        ];
+        return getContents($url, $headers, [], true);
+    }
+
+    private function getAccessToken(): string
+    {
+        $cachedToken = $this->cache->get(self::OAUTH_TOKEN_KEY);
+        if ($cachedToken) {
+            return $cachedToken;
+        }
+
+        $headers = [
+            'User-Agent: ' . self::USER_AGENT,
+            'Authorization: Basic ' . base64_encode((string) $this->appId . ':' . (string) $this->appSecret),
+        ];
+        $data = [
+            'grant_type' => 'client_credentials',
+            'scope' => 'read',
+        ];
+        $curlopts = [
+            CURLOPT_POST => true,
+            CURLOPT_POSTFIELDS => http_build_query($data),
+        ];
+        $response = getContents('https://www.reddit.com/api/v1/access_token', $headers, $curlopts);
+
+        $data = Json::decode($response, false);
+        $token = $data->access_token;
+        if (!isset($token)) {
+            throw new \Exception('Failed to obtain Reddit OAuth access token: ' . $response);
+        }
+        $expiresIn = $data->expires_in ?? 3600;
+        $this->cache->set(self::OAUTH_TOKEN_KEY, $token, $expiresIn - 60);
+        return $token;
+    }
+
+    private static function createSearchUrl(string $apiUri, array $parameters): string
+    {
+        return $apiUri . '/search.json?' . http_build_query($parameters);
+    }
+}