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Raise ValueError if PNG chunks are truncated

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This commit is contained in:
Andrew Murray 2022-05-01 13:45:58 +10:00
parent 7d5162cb37
commit 51bdc99b96
2 changed files with 32 additions and 0 deletions
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11
Tests/test_file_png.py
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@ -635,6 +635,17 @@ class TestFilePng:
assert_image_equal_tofile(im, "Tests/images/bw_gradient.png")
@pytest.mark.parametrize("cid", (b"IHDR", b"pHYs", b"acTL", b"fcTL", b"fdAT"))
def test_truncated_chunks(self, cid):
fp = BytesIO()
with PngImagePlugin.PngStream(fp) as png:
with pytest.raises(ValueError):
png.call(cid, 0, 0)
ImageFile.LOAD_TRUNCATED_IMAGES = True
png.call(cid, 0, 0)
ImageFile.LOAD_TRUNCATED_IMAGES = False
def test_specify_bits(self, tmp_path):
im = hopper("P")

21
src/PIL/PngImagePlugin.py
View File

@ -424,6 +424,10 @@ class PngStream(ChunkStream):
# image header
s = ImageFile._safe_read(self.fp, length)
if length < 13:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
raise ValueError("Truncated IHDR chunk")
self.im_size = i32(s, 0), i32(s, 4)
try:
self.im_mode, self.im_rawmode = _MODES[(s[8], s[9])]
@ -512,6 +516,10 @@ class PngStream(ChunkStream):
# pixels per unit
s = ImageFile._safe_read(self.fp, length)
if length < 9:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
raise ValueError("Truncated pHYs chunk")
px, py = i32(s, 0), i32(s, 4)
unit = s[8]
if unit == 1: # meter
@ -624,6 +632,10 @@ class PngStream(ChunkStream):
# APNG chunks
def chunk_acTL(self, pos, length):
s = ImageFile._safe_read(self.fp, length)
if length < 8:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
raise ValueError("APNG contains truncated acTL chunk")
if self.im_n_frames is not None:
self.im_n_frames = None
warnings.warn("Invalid APNG, will use default PNG image if possible")
@ -639,6 +651,10 @@ class PngStream(ChunkStream):
def chunk_fcTL(self, pos, length):
s = ImageFile._safe_read(self.fp, length)
if length < 26:
if ImageFile.LOAD_TRUNCATED_IMAGES:
return s
raise ValueError("APNG contains truncated fcTL chunk")
seq = i32(s)
if (self._seq_num is None and seq != 0) or (
self._seq_num is not None and self._seq_num != seq - 1
@ -660,6 +676,11 @@ class PngStream(ChunkStream):
return s
def chunk_fdAT(self, pos, length):
if length < 4:
if ImageFile.LOAD_TRUNCATED_IMAGES:
s = ImageFile._safe_read(self.fp, length)
return s
raise ValueError("APNG contains truncated fDAT chunk")
s = ImageFile._safe_read(self.fp, 4)
seq = i32(s)
if self._seq_num != seq - 1: