Added opt-in thumbnail proxying in upload

Rationale: some services thought that images linked from /posts/upload
are hotlinked. This is because they were receiving referrer set to a
host that is unknown for them. By using proxying, referrer is blank,
which increases thumbnail coverage at the expense of increased
server-side traffic.

data/config.ini

@@ -19,6 +19,7 @@ title           = "szurubooru"
 
 [misc]
 featuredPostMaxDays=7
+proxyThumbsInUpload=0
 debugQueries=0
 githubLink = http://github.com/rr-/szurubooru
 

public_html/media/js/post-upload.js

@@ -189,7 +189,7 @@ $(function()
 	{
 		$(img)
 			.css('background-image', 'none')
-			.attr('src', url)
+			.attr('src', '/posts/upload/thumb/' + btoa(url))
 			.data('custom-thumb', true);
 	}
 

src/Controllers/PostController.php

@@ -143,6 +143,34 @@ class PostController extends AbstractController
 			$this->redirectToPostList();
 	}
 
+	public function uploadThumbnailView($url)
+	{
+		$url = base64_decode($url);
+
+		if (!Core::getConfig()->misc->proxyThumbsInUpload)
+		{
+			$this->redirect($url);
+			return;
+		}
+
+		$tmpPath = tempnam(sys_get_temp_dir(), 'thumb4upload');
+		try
+		{
+			TransferHelper::download($url, $tmpPath);
+			$context = Core::getContext();
+			$context->transport->lastModified = time();
+			$context->transport->mimeType = mime_content_type($tmpPath);
+			$context->transport->cacheDaysToLive = 0.5;
+			$context->transport->fileHash = md5($url);
+			$context->transport->fileContent = file_get_contents($tmpPath);
+			$this->renderFile();
+		}
+		finally
+		{
+			TransferHelper::remove($tmpPath);
+		}
+	}
+
 	public function editView($identifier)
 	{
 		$jobArgs = [];

src/Router.php

@@ -56,6 +56,7 @@ class Router extends \Chibi\Routing\Router
 		$this->register(['PostController', 'editAction'], 'POST', '/post/{identifier}/edit', $postValidation);
 		$this->register(['PostController', 'deleteAction'], null, '/post/{identifier}/delete', $postValidation);
 
+		$this->register(['PostController', 'uploadThumbnailView'], 'GET', '/posts/upload/thumb/{url}', ['url' => '.*']);
 		$this->register(['PostController', 'listView'], 'GET', '/{source}', $postValidation);
 		$this->register(['PostController', 'listView'], 'GET', '/{source}/{page}', $postValidation);
 		$this->register(['PostController', 'listView'], 'GET', '/{source}/{query}/{page}', $postValidation);