fix(previews): Don't crash on animated WEBP images

Fixes #30029 and #37263

libgd handles animated WEBP images poorly and generates a meaningless error message as a result. We were returning a 500 error for these preview requests (web) and a fatal error at the command-line (occ). Now we bypass libgd if the we detect an animated WEBP image (and simply don't generate the preview). No more 500 error. Should fix occ too.

Signed-off-by: Josh Richards <josh.t.richards@gmail.com>
Signed-off-by: Richard Steinmetz <richard@steinmetz.cloud>

diff --git a/lib/private/legacy/OC_Image.php b/lib/private/legacy/OC_Image.php
index 794d59b25fe171deb9d55f2ff56bdf4325b99fca..7496702140572ea4500b0623184f909dac8149bf 100644 (file)
--- a/lib/private/legacy/OC_Image.php
+++ b/lib/private/legacy/OC_Image.php
@@ -748,9 +748,56 @@ class OC_Image implements \OCP\IImage {
                                        if (!$this->checkImageSize($imagePath)) {
                                                return false;
                                        }
-                                       $this->resource = @imagecreatefromwebp($imagePath);
+
+                                       // Check for animated header before generating preview since libgd does not handle them well
+                                       // Adapted from here: https://stackoverflow.com/a/68491679/4085517 (stripped to only to check for animations + added additional error checking)
+                                       // Header format details here: https://developers.google.com/speed/webp/docs/riff_container
+
+                                       // Load up the header data, if any
+                                       $fp = fopen($imagePath, 'rb');
+                                       if (!$fp) {
+                                               return false;
+                                       }
+                                       $data = fread($fp, 90);
+                                       if (!$data) {
+                                               return false;
+                                       }
+                                       fclose($fp);
+                                       unset($fp);
+
+                                       $headerFormat = 'A4Riff/' . // get n string
+                                               'I1Filesize/' . // get integer (file size but not actual size)
+                                               'A4Webp/' . // get n string
+                                               'A4Vp/' . // get n string
+                                               'A74Chunk';
+
+                                       $header = unpack($headerFormat, $data);
+                                       unset($data, $headerFormat);
+                                       if (!$header) {
+                                               return false;
+                                       }
+
+                                       // Check if we're really dealing with a valid WEBP header rather than just one suffixed ".webp"
+                                       if (!isset($header['Riff']) || strtoupper($header['Riff']) !== 'RIFF') {
+                                               return false;
+                                       }
+                                       if (!isset($header['Webp']) || strtoupper($header['Webp']) !== 'WEBP') {
+                                               return false;
+                                       }
+                                       if (!isset($header['Vp']) || strpos(strtoupper($header['Vp']), 'VP8') === false) {
+                                               return false;
+                                       }
+
+                                       // Check for animation indicators
+                                       if (strpos(strtoupper($header['Chunk']), 'ANIM') !== false || strpos(strtoupper($header['Chunk']), 'ANMF') !== false) {
+                                               // Animated so don't let it reach libgd
+                                               $this->logger->debug('OC_Image->loadFromFile, animated WEBP images not supported: ' . $imagePath, ['app' => 'core']);
+                                       } else {
+                                               // We're safe so give it to libgd
+                                               $this->resource = @imagecreatefromwebp($imagePath);
+                                       }
                                } else {
-                                       $this->logger->debug('OC_Image->loadFromFile, webp images not supported: ' . $imagePath, ['app' => 'core']);
+                                       $this->logger->debug('OC_Image->loadFromFile, WEBP images not supported: ' . $imagePath, ['app' => 'core']);
                                }
                                break;
                                /*