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[3.9] bpo-38256: Fix binascii.crc32 large input. #32015

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Merged
gpshead merged 1 commit into from
Mar 21, 2022
Merged

[3.9] bpo-38256: Fix binascii.crc32 large input. #32015

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10 changes: 10 additions & 0 deletions Lib/test/test_binascii.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,8 @@
import array
import re
from test import support
from test.support import bigmemtest, _1G, _4G, warnings_helper


# Note: "*_hex" functions are aliases for "(un)hexlify"
b2a_functions = ['b2a_base64', 'b2a_hex', 'b2a_hqx', 'b2a_qp', 'b2a_uu',
Expand Down Expand Up @@ -448,6 +450,14 @@ 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 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Library/2022-03-19-15-54-41.bpo-38256.FoMbjE.rst
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@@ -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.
22 changes: 13 additions & 9 deletions Modules/binascii.c
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Expand Up @@ -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;

buf = (Byte*)data->buf;
len = data->len;
signed_val = crc32(crc, buf, len);
return (unsigned int)signed_val & 0xffffffffU;
unsigned char *buf = data->buf;
Py_ssize_t len = data->len;

/* 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 */
Expand Down