From 31de5ab9716df36202127e9b1657ace23d499c4c Mon Sep 17 00:00:00 2001
From: Mischa POSLAWSKY <perl@shiar.org>
Date: Wed, 4 Jul 2018 18:53:30 +0200
Subject: [PATCH] thumb: error image also on unexpected exceptions

Output is expected to be an image so avoid HTML responses.
Replace 501 placeholder by a common 500.png on any resize error.
Preserve message in X-Error header for debugging.
---
 thumb/index.php | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/thumb/index.php b/thumb/index.php
index 66de106..e8b3bcb 100644
--- a/thumb/index.php
+++ b/thumb/index.php
@@ -5,14 +5,6 @@ list ($height, $imgpath) = explode('/', ltrim($Args, '/'), 2);
 $width= 1000;
 $imgpath = preg_replace('{^(?=[0-9]+/)}', 'data/', $imgpath, 1);
 
-if (!function_exists('popen')) {
-	http_response_code(501);
-	$target = '501.png';
-	header('Content-type: '.mime_content_type($target));
-	readfile($target);
-	exit;
-}
-
 if (!file_exists($imgpath)) {
 	http_response_code(404);
 	exit;
@@ -24,7 +16,14 @@ if (!file_exists($target)) {
 		mkthumb($imgpath, $target, $width, $height);
 	}
 	catch (Exception $e) {
-		http_response_code(500);
+		http_response_code($e->getCode() ?: 500);
+		$target = '500.png';
+		if (file_exists($target)) {
+			header("X-Error: ".$e->getMessage());
+			header('Content-type: '.mime_content_type($target));
+			readfile($target);
+			exit;
+		}
 		trigger_error("thumbnail creation failed: ".$e->getMessage(), E_USER_WARNING);
 		exit;
 	}
@@ -42,6 +41,9 @@ function mkthumb($source, $target, $width, $height)
 
 function mkthumb_exec($source, $target, $width, $height)
 {
+	if (!function_exists('popen')) {
+		throw new Exception("exec disallowed on this server", 501);
+	}
 	$cmd = implode(' ', array_map('escapeshellarg', [
 		'convert',
 		'-trim',
-- 
2.30.0