8000 gh-118314: Fix padding edge case in binascii.a2b_base64 strict mode by zhangyoufu · Pull Request #118320 · python/cpython · GitHub
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gh-118314: Fix padding edge case in binascii.a2b_base64 strict mode #118320

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Merged
merged 6 commits into from
May 7, 2024
Merged

gh-118314: Fix padding edge case in binascii.a2b_base64 strict mode #118320

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84b8420
gh-118314: Fix padding edge case in binascii.a2b_base64 strict mode
zhangyoufu Apr 26, 2024
788c085
📜🤖 Added by blurb_it.
blurb-it[bot] Apr 26, 2024
03c6675
Update Misc/NEWS.d/next/Library/2024-04-26-12-42-29.gh-issue-118314.Z…
terryjreedy Apr 26, 2024
d2637b7
Merge branch 'main' into gh-118314
terryjreedy Apr 26, 2024
af5359e
adjust error message as requested
zhangyoufu Apr 29, 2024
33be76b
refine test cases as requested
zhangyoufu Apr 29, 2024
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gh-118314: Fix padding edge case in binascii.a2b_base64 strict mode
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@zhangyoufu
zhangyoufu committed Apr 26, 2024
commit 84b8420a41b5816e7c5c4fd434bb4416bc5747c5
6 changes: 6 additions & 0 deletions Lib/test/test_binascii.py
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Expand Up @@ -139,6 +139,9 @@ def assertLeadingPadding(data, non_strict_mode_expected_result: bytes):
def assertDiscontinuousPadding(data, non_strict_mode_expected_result: bytes):
_assertRegexTemplate(r'(?i)Discontinuous padding', data, non_strict_mode_expected_result)

def assertIncorrectPadding(data, non_strict_mode_expected_result: bytes):
_assertRegexTemplate(r'(?i)Incorrect padding', data, non_strict_mode_expected_result)

# Test excess data exceptions
assertExcessData(b'ab==a', b'i')
assertExcessData(b'ab===', b'i')
Expand All @@ -159,6 +162,9 @@ def assertDiscontinuousPadding(data, non_strict_mode_expected_result: bytes):
assertLeadingPadding(b'===', b'')
assertDiscontinuousPadding(b'ab=c=', b'i\xb7')
assertDiscontinuousPadding(b'ab=ab==', b'i\xb6\x9b')
assertIncorrectPadding(b'AAAA=', b'\x00\x00\x00')
assertIncorrectPadding(b'AAAA==', b'\x00\x00\x00')
assertIncorrectPadding(b'AAAA===', b'\x00\x00\x00')


def test_base64errors(self):
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7 changes: 7 additions & 0 deletions Modules/binascii.c
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Expand Up @@ -414,6 +414,13 @@ binascii_a2b_base64_impl(PyObject *module, Py_buffer *data, int strict_mode)
if (this_ch == BASE64_PAD) {
padding_started = 1;

if (strict_mode && quad_pos == 0) {
state = get_binascii_state(module);
if (state) {
PyErr_SetString(state->Error, "Incorrect padding");
}
goto error_end;
}
if (quad_pos >= 2 && quad_pos + ++pads >= 4) {
/* A pad sequence means we should not parse more input.
** We've already interpreted the data from the quad at this point.
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0