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Fix for #318: Catch truncated zTXt errors. #321

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merged 2 commits into from
Aug 21, 2013
Merged

Fix for #318: Catch truncated zTXt errors. #321

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dbf40a0
Catch truncated zTXt errors.
vytisb Aug 20, 2013
febfd1e
Python3 fix.
vytisb Aug 20, 2013
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24 changes: 17 additions & 7 deletions PIL/PngImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -305,18 +305,28 @@ def chunk_zTXt(self, pos, len):

# compressed text
s = ImageFile._safe_read(self.fp, len)
k, v = s.split(b"\0", 1)
comp_method = i8(v[0])
try:
k, v = s.split(b"\0", 1)
except ValueError:
k = s; v = b""
if v:
comp_method = i8(v[0])
else:
comp_method = 0
if comp_method != 0:
raise SyntaxError("Unknown compression method %s in zTXt chunk" % comp_method)
import zlib
v = zlib.decompress(v[1:])
try:
v = zlib.decompress(v[1:])
except zlib.error:
v = b""

if bytes is not str:
k = k.decode('latin-1', 'strict')
v = v.decode('latin-1', 'replace')
if k:
if bytes is not str:
k = k.decode('latin-1', 'strict')
v = v.decode('latin-1', 'replace')

self.im_info[k] = self.im_text[k] = v
self.im_info[k] = self.im_text[k] = v
return s

# --------------------------------------------------------------------
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22 changes: 22 additions & 0 deletions Tests/test_file_png.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

from PIL import Image
from PIL import PngImagePlugin
import zlib

codecs = dir(Image.core)

Expand Down Expand Up @@ -99,6 +100,27 @@ def test_bad_text():
im = load(HEAD + chunk(b'tEXt', b'spam\0egg\0') + TAIL)
assert_equal(im.info, {'spam': 'egg\x00'})

def test_bad_ztxt():
# Test reading malformed zTXt chunks (python-imaging/Pillow#318)

im = load(HEAD + chunk(b'zTXt') + TAIL)
assert_equal(im.info, {})

im = load(HEAD + chunk(b'zTXt', b'spam') + TAIL)
assert_equal(im.info, {'spam': ''})

im = load(HEAD + chunk(b'zTXt', b'spam\0') + TAIL)
assert_equal(im.info, {'spam': ''})

im = load(HEAD + chunk(b'zTXt', b'spam\0\0') + TAIL)
assert_equal(im.info, {'spam': ''})

im = load(HEAD + chunk(b'zTXt', b'spam\0\0' + zlib.compress(b'egg')[:1]) + TAIL)
assert_equal(im.info, {'spam': ''})

im = load(HEAD + chunk(b'zTXt', b'spam\0\0' + zlib.compress(b'egg')) + TAIL)
assert_equal(im.info, {'spam': 'egg'})

def test_interlace():

file = "Tests/images/pil123p.png"
Expand Down