Use an alternative way to detect image

When parsing content to retrieve images to save locally, we only check for the content-type of the image response.
In some case, that value is empty.
Now we’re also checking for the first few bytes of the content as an alternative to detect if it’s an image wallabag can handle.
We might get higher image supports using that alternative method.

src/Wallabag/CoreBundle/Helper/DownloadImages.php

@@ -5,6 +5,7 @@ namespace Wallabag\CoreBundle\Helper;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\DomCrawler\Crawler;
 use GuzzleHttp\Client;
+use GuzzleHttp\Message\Response;
 use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeExtensionGuesser;
 use Symfony\Component\Finder\Finder;
 
@@ -116,13 +117,11 @@ class DownloadImages
             return false;
         }
 
-        $ext = $this->mimeGuesser->guess($res->getHeader('content-type'));
-        $this->logger->debug('DownloadImages: Checking extension', ['ext' => $ext, 'header' => $res->getHeader('content-type')]);
-        if (!in_array($ext, ['jpeg', 'jpg', 'gif', 'png'], true)) {
-            $this->logger->error('DownloadImages: Processed image with not allowed extension. Skipping: '.$imagePath);
-
+        $ext = $this->getExtensionFromResponse($res, $imagePath);
+        if (false === $res) {
             return false;
         }
+
         $hashImage = hash('crc32', $absolutePath);
         $localPath = $folderPath.'/'.$hashImage.'.'.$ext;
 
@@ -237,4 +236,45 @@ class DownloadImages
 
         return false;
     }
+
+    /**
+     * Retrieve and validate the extension from the response of the url of the image.
+     *
+     * @param Response $res       Guzzle Response
+     * @param string   $imagePath Path from the src image from the content (used for log only)
+     *
+     * @return string|false Extension name or false if validation failed
+     */
+    private function getExtensionFromResponse(Response $res, $imagePath)
+    {
+        $ext = $this->mimeGuesser->guess($res->getHeader('content-type'));
+        $this->logger->debug('DownloadImages: Checking extension', ['ext' => $ext, 'header' => $res->getHeader('content-type')]);
+
+        // ok header doesn't have the extension, try a different way
+        if (empty($ext)) {
+            $types = [
+                'jpeg' => "\xFF\xD8\xFF",
+                'gif' => 'GIF',
+                'png' => "\x89\x50\x4e\x47\x0d\x0a",
+            ];
+            $bytes = substr((string) $res->getBody(), 0, 8);
+
+            foreach ($types as $type => $header) {
+                if (0 === strpos($bytes, $header)) {
+                    $ext = $type;
+                    break;
+                }
+            }
+
+            $this->logger->debug('DownloadImages: Checking extension (alternative)', ['ext' => $ext]);
+        }
+
+        if (!in_array($ext, ['jpeg', 'jpg', 'gif', 'png'], true)) {
+            $this->logger->error('DownloadImages: Processed image with not allowed extension. Skipping: '.$imagePath);
+
+            return false;
+        }
+
+        return $ext;
+    }
 }

tests/Wallabag/CoreBundle/Helper/DownloadImagesTest.php

@@ -157,4 +157,29 @@ class DownloadImagesTest extends \PHPUnit_Framework_TestCase
 
         $this->assertFalse($res, 'Absolute image can not be determined, so it will not be replaced');
     }
+
+    public function testProcessRealImage()
+    {
+        $client = new Client();
+
+        $mock = new Mock([
+            new Response(200, ['content-type' => null], Stream::factory(file_get_contents(__DIR__.'/../fixtures/image-no-content-type.jpg'))),
+        ]);
+
+        $client->getEmitter()->attach($mock);
+
+        $logHandler = new TestHandler();
+        $logger = new Logger('test', array($logHandler));
+
+        $download = new DownloadImages($client, sys_get_temp_dir().'/wallabag_test', 'http://wallabag.io/', $logger);
+
+        $res = $download->processSingleImage(
+            123,
+            'https://cdn.theconversation.com/files/157200/article/width926/gsj2rjp2-1487348607.jpg',
+            'https://theconversation.com/conversation-avec-gerald-bronner-ce-nest-pas-la-post-verite-qui-nous-menace-mais-lextension-de-notre-credulite-73089'
+        );
+
+        $this->assertContains('http://wallabag.io/assets/images/9/b/9b0ead26/', $res, 'Content-Type was empty but data is ok for an image');
+        $this->assertContains('DownloadImages: Checking extension (alternative)', $logHandler->getRecords()[3]['message']);
+    }
 }