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[3.10] bpo-38256: Fix binascii.crc32 large input. (GH-32000) (GH-32013)

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Inputs >= 4GiB to `binascii.crc32(...)` when compiled to use the zlib
crc32 implementation (the norm on POSIX) no longer return the wrong
result.
This commit is contained in:
Gregory P. Smith 2022-03-20 14:46:52 -07:00 • committed by GitHub
parent 94f038cbb2
commit 4c989e19c8
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 26 additions and 9 deletions
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10
Lib/test/test_binascii.py
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@ -4,7 +4,7 @@ import unittest
import binascii
import array
import re
from test.support import warnings_helper
from test.support import bigmemtest, _1G, _4G, warnings_helper
# Note: "*_hex" functions are aliases for "(un)hexlify"
@ -449,6 +449,14 @@ class BytearrayBinASCIITest(BinASCIITest):
class MemoryviewBinASCIITest(BinASCIITest):
type2test = memoryview
class ChecksumBigBufferTestCase(unittest.TestCase):
"""bpo-38256 - check that inputs >=4 GiB are handled correctly."""
@bigmemtest(size=_4G + 4, memuse=1, dry_run=False)
def test_big_buffer(self, size):
data = b"nyan" * (_1G + 1)
self.assertEqual(binascii.crc32(data), 1044521549)
if __name__ == "__main__":
unittest.main()

5
Misc/NEWS.d/next/Library/2022-03-19-15-54-41.bpo-38256.FoMbjE.rst Normal file
View file

@ -0,0 +1,5 @@
Fix :func:`binascii.crc32` when it is compiled to use zlib'c crc32 to
work properly on inputs 4+GiB in length instead of returning the wrong
result. The workaround prior to this was to always feed the function
data in increments smaller than 4GiB or to just call the zlib module
function.

20
Modules/binascii.c
View file

@ -1120,16 +1120,20 @@ binascii_crc32_impl(PyObject *module, Py_buffer *data, unsigned int crc)
/*[clinic end generated code: output=52cf59056a78593b input=bbe340bc99d25aa8]*/
#ifdef USE_ZLIB_CRC32
/* This was taken from zlibmodule.c PyZlib_crc32 (but is PY_SSIZE_T_CLEAN) */
/* The same core as zlibmodule.c zlib_crc32_impl. */
{
const Byte *buf;
Py_ssize_t len;
int signed_val;
unsigned char *buf = data->buf;
Py_ssize_t len = data->len;
buf = (Byte*)data->buf;
len = data->len;
signed_val = crc32(crc, buf, len);
return (unsigned int)signed_val & 0xffffffffU;
/* Avoid truncation of length for very large buffers. crc32() takes
length as an unsigned int, which may be narrower than Py_ssize_t. */
while ((size_t)len > UINT_MAX) {
crc = crc32(crc, buf, UINT_MAX);
buf += (size_t) UINT_MAX;
len -= (size_t) UINT_MAX;
}
crc = crc32(crc, buf, (unsigned int)len);
return crc & 0xffffffff;
}
#else /* USE_ZLIB_CRC32 */
{ /* By Jim Ahlstrom; All rights transferred to CNRI */