Perform validation of redirect URLs during the redirect process.

Previously, validation was only done after all redirects and the final request had completed.  This approach ensures all redirects are to URLs that pass extended validation.

1 files changed, 23 insertions, 2 deletions

diff --git a/classes/UrlHelper.php b/classes/UrlHelper.php
index 03202cff8..82b8bf36e 100644
--- a/classes/UrlHelper.php
+++ b/classes/UrlHelper.php
@@ -1,4 +1,9 @@
 <?php
+
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\UriInterface;
+
 class UrlHelper {
 	const EXTRA_HREF_SCHEMES = [
 		"magnet",
@@ -312,13 +317,28 @@ class UrlHelper {
 		$req_options = [
 			GuzzleHttp\RequestOptions::CONNECT_TIMEOUT => $timeout ?: Config::get(Config::FILE_FETCH_CONNECT_TIMEOUT),
 			GuzzleHttp\RequestOptions::TIMEOUT => $timeout ?: Config::get(Config::FILE_FETCH_TIMEOUT),
-			GuzzleHttp\RequestOptions::ALLOW_REDIRECTS => $followlocation ? ['max' => 20, 'track_redirects' => true] : false,
 			GuzzleHttp\RequestOptions::HEADERS => [
 				'User-Agent' => $useragent ?: Config::get_user_agent(),
 			],
 			'curl' => [],
 		];
 
+		if ($followlocation) {
+			$req_options[GuzzleHttp\RequestOptions::ALLOW_REDIRECTS] = [
+				'max' => 20,
+				'track_redirects' => true,
+				'on_redirect' => function(RequestInterface $request, ResponseInterface $response, UriInterface $uri) {
+					if (!self::validate($uri, true)) {
+						self::$fetch_effective_url = (string) $uri;
+						throw new GuzzleHttp\Exception\RequestException('URL received during redirection failed extended validation.',
+							$request, $response);
+					}
+				},
+			];
+		} else {
+			$req_options[GuzzleHttp\RequestOptions::ALLOW_REDIRECTS] = false;
+		}
+
 		if ($last_modified && !$post_query)
 			$req_options[GuzzleHttp\RequestOptions::HEADERS]['If-Modified-Since'] = $last_modified;
 
@@ -355,7 +375,7 @@ class UrlHelper {
 			};
 
 			# Alternative/supplement to `progress` checking
-			$req_options[GuzzleHttp\RequestOptions::ON_HEADERS] = function(Psr\Http\Message\ResponseInterface $response) use(&$max_size, $url) {
+			$req_options[GuzzleHttp\RequestOptions::ON_HEADERS] = function(ResponseInterface $response) use(&$max_size, $url) {
 				$content_length = $response->getHeaderLine('Content-Length');
 				if ($content_length > $max_size) {
 					Debug::log("[UrlHelper] fetch error: server indicated (via 'Content-Length: {$content_length}') max size of $max_size bytes " .
@@ -426,6 +446,7 @@ class UrlHelper {
 		$history_header = $response->getHeader(GuzzleHttp\RedirectMiddleware::HISTORY_HEADER);
 		self::$fetch_effective_url = $history_header ? end($history_header) : $url;
 
+		// This shouldn't be necessary given the checks that occur during potential redirects, but we'll do it anyway.
 		if (!self::validate(self::$fetch_effective_url, true)) {
 			self::$fetch_last_error = "URL received after redirection failed extended validation.";
 			$span->setAttribute('error', self::$fetch_last_error);