PICARD-1662: Do not save too large images to FLAC

picard/formats/vorbis.py

@@ -49,6 +49,7 @@ from picard.util import (
 )
 
 
+FLAC_MAX_BLOCK_SIZE = 2 ** 24 - 1  # FLAC block size is limited to a 24 bit integer
 INVALID_CHARS = re.compile('([^\x20-\x7d]|=)')
 
 
@@ -271,6 +272,14 @@ class VCommentFile(File):
             picture.height = image.height
             picture.type = image_type_as_id3_num(image.maintype)
             if is_flac:
+                # See https://xiph.org/flac/format.html#metadata_block_picture
+                expected_block_size = (8 * 4 + len(picture.data)
+                    + len(picture.mime)
+                    + len(picture.desc.encode('UTF-8')))
+                if expected_block_size > FLAC_MAX_BLOCK_SIZE:
+                    log.error('Failed saving image to %r: Image size of %d bytes exceeds maximum FLAC block size of %d bytes',
+                        filename, expected_block_size, FLAC_MAX_BLOCK_SIZE)
+                    continue
                 file.add_picture(picture)
             else:
                 tags.setdefault("METADATA_BLOCK_PICTURE", []).append(

test/formats/test_vorbis.py

@@ -10,7 +10,10 @@ from mutagen.flac import (
     VCFLACDict,
 )
 
-from test.picardtestcase import PicardTestCase
+from test.picardtestcase import (
+    PicardTestCase,
+    create_fake_png,
+)
 
 from picard import (
     config,
@@ -291,6 +294,15 @@ class FlacCoverArtTest(CommonCoverArtTests.CoverArtTestCase):
             self.assertNotEqual(pic.height, 0)
             self.assertEqual(pic.height, test.height)
 
+    def test_save_large_pics(self):
+        # 16 MB image
+        data = create_fake_png(b"a" * 1024 * 1024 * 16)
+        image = CoverArtImage(data=data)
+        file_save_image(self.filename, image)
+        raw_metadata = load_raw(self.filename)
+        # Images with more than 16 MB cannot be saved to FLAC
+        self.assertEqual(0, len(raw_metadata.pictures))
+
 
 class OggAudioVideoFileTest(PicardTestCase):
     def test_ogg_audio(self):