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Catch struct.errors when verifying png files, convert to SyntaxErrors, fixes #1755

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This commit is contained in:
wiredfool 2016-04-04 03:08:22 -07:00
parent fd7fa4e61d
commit 77da73c90f
2 changed files with 40 additions and 16 deletions
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14
PIL/PngImagePlugin.py
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@ -36,6 +36,7 @@ from __future__ import print_function
import logging import logging
import re import re
import zlib import zlib
import struct
from PIL import Image, ImageFile, ImagePalette, _binary from PIL import Image, ImageFile, ImagePalette, _binary
@ -106,7 +107,8 @@ class ChunkStream(object):
def read(self): def read(self):
"Fetch a new chunk. Returns header information." "Fetch a new chunk. Returns header information."
cid = None
try:
if self.queue: if self.queue:
cid, pos, length = self.queue[-1] cid, pos, length = self.queue[-1]
del self.queue[-1] del self.queue[-1]
@ -116,6 +118,8 @@ class ChunkStream(object):
cid = s[4:] cid = s[4:]
pos = self.fp.tell() pos = self.fp.tell()
length = i32(s) length = i32(s)
except struct.error:
SyntaxError("truncated PNG file (chunk %s)" % repr(cid))
if not is_cid(cid): if not is_cid(cid):
raise SyntaxError("broken PNG file (chunk %s)" % repr(cid)) raise SyntaxError("broken PNG file (chunk %s)" % repr(cid))
@ -138,11 +142,15 @@ class ChunkStream(object):
def crc(self, cid, data): def crc(self, cid, data):
"Read and verify checksum" "Read and verify checksum"
try:
crc1 = Image.core.crc32(data, Image.core.crc32(cid)) crc1 = Image.core.crc32(data, Image.core.crc32(cid))
crc2 = i16(self.fp.read(2)), i16(self.fp.read(2)) crc2 = i16(self.fp.read(2)), i16(self.fp.read(2))
if crc1 != crc2: if crc1 != crc2:
raise SyntaxError("broken PNG file" raise SyntaxError("broken PNG file (bad header checksum in %s)"
"(bad header checksum in %s)" % cid) % cid)
except struct.error:
raise SyntaxError("broken PNG file (incomplete checksum in %s)"
% cid)
def crc_skip(self, cid, data): def crc_skip(self, cid, data):
"Read checksum. Used if the C module is not present" "Read checksum. Used if the C module is not present"

16
Tests/test_file_png.py
View File

@ -253,6 +253,22 @@ class TestFilePng(PillowTestCase):
im.load() im.load()
self.assertRaises(RuntimeError, im.verify) self.assertRaises(RuntimeError, im.verify)
def test_verify_struct_error(self):
# Check open/load/verify exception (#1755)
# offsets to test, -10: breaks in i32() in read.
# -13: breaks in crc, txt chunk.
# -14: malformed chunk
for offset in (-10, -13, -14):
with open(TEST_PNG_FILE,'rb') as f:
test_file = f.read()[:offset]
im = Image.open(BytesIO(test_file))
self.assertTrue(im.fp is not None)
self.assertRaises(SyntaxError, im.verify)
def test_roundtrip_dpi(self): def test_roundtrip_dpi(self):
# Check dpi roundtripping # Check dpi roundtripping