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gh-148016: Improve "Leading padding not allowed" error in Base32 and Base64 decoders #148017

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gh-148016: Improve "Leading padding not allowed" error in Base32 and Base64 decoders #148017

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21 changes: 12 additions & 9 deletions Lib/test/test_binascii.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,20 +159,20 @@ def addnoise(line):
def test_base64_bad_padding(self):
# Test malformed padding
def _assertRegexTemplate(assert_regex, data,
non_strict_mode_expected_result):
non_strict_mode_expected_result, **kwargs):
data = self.type2test(data)
with self.assertRaisesRegex(binascii.Error, assert_regex):
binascii.a2b_base64(data, strict_mode=True)
binascii.a2b_base64(data, strict_mode=True, **kwargs)
self.assertEqual(binascii.a2b_base64(data, strict_mode=False),
non_strict_mode_expected_result)
self.assertEqual(binascii.a2b_base64(data, strict_mode=True,
ignorechars=b'='),
ignorechars=b' ='),
non_strict_mode_expected_result)
self.assertEqual(binascii.a2b_base64(data),
non_strict_mode_expected_result)

def assertLeadingPadding(*args):
_assertRegexTemplate(r'(?i)Leading padding', *args)
def assertLeadingPadding(*args, **kwargs):
_assertRegexTemplate(r'(?i)Leading padding', *args, **kwargs)

def assertDiscontinuousPadding(*args):
_assertRegexTemplate(r'(?i)Discontinuous padding', *args)
Expand Down Expand Up @@ -200,6 +200,7 @@ def assertInvalidLength(*args):
assertLeadingPadding(b'===abcd', b'i\xb7\x1d')
assertLeadingPadding(b'====abcd', b'i\xb7\x1d')
assertLeadingPadding(b'=====abcd', b'i\xb7\x1d')
assertLeadingPadding(b' =abcd', b'i\xb7\x1d', ignorechars=b' ')

assertInvalidLength(b'a=b==', b'i')
assertInvalidLength(b'a=bc=', b'i\xb7')
Expand Down Expand Up @@ -763,9 +764,10 @@ def _fixPadding(data):
p = 8 - len_8 if len_8 else 0
return fixed + b"=" * p

def _assertRegexTemplate(assert_regex, data, good_padding_result=None):
def _assertRegexTemplate(assert_regex, data, good_padding_result=None,
**kwargs):
with self.assertRaisesRegex(binascii.Error, assert_regex):
binascii.a2b_base32(self.type2test(data))
binascii.a2b_base32(self.type2test(data), **kwargs)
if good_padding_result:
fixed = self.type2test(_fixPadding(data))
self.assertEqual(binascii.a2b_base32(fixed), good_padding_result)
Expand All @@ -779,8 +781,8 @@ def assertExcessData(*args):
def assertExcessPadding(*args):
_assertRegexTemplate(r"(?i)Excess padding", *args)

def assertLeadingPadding(*args):
_assertRegexTemplate(r"(?i)Leading padding", *args)
def assertLeadingPadding(*args, **kwargs):
_assertRegexTemplate(r"(?i)Leading padding", *args, **kwargs)

def assertIncorrectPadding(*args):
_assertRegexTemplate(r"(?i)Incorrect padding", *args)
Expand Down Expand Up @@ -844,6 +846,7 @@ def assertInvalidLength(*args):
assertLeadingPadding(b"=======BEEFCAKE", b"\t\x08Q\x01D")
assertLeadingPadding(b"========BEEFCAKE", b"\t\x08Q\x01D")
assertLeadingPadding(b"=========BEEFCAKE", b"\t\x08Q\x01D")
assertLeadingPadding(b" =BEEFCAKE", ignorechars=b' ')

assertIncorrectPadding(b"AB")
assertIncorrectPadding(b"ABCD")
Expand Down
6 changes: 4 additions & 2 deletions Modules/binascii.c
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Original file line number Diff line number Diff line change
Expand Up @@ -816,8 +816,9 @@ binascii_a2b_base64_impl(PyObject *module, Py_buffer *data, int strict_mode,
}
state = get_binascii_state(module);
if (state) {
unsigned char *bin_data_start = PyBytesWriter_GetData(writer);
PyErr_SetString(state->Error,
(quad_pos == 0 && ascii_data == data->buf)
(quad_pos == 0 && bin_data == bin_data_start)
? "Leading padding not allowed"
: "Excess padding not allowed");
}
Expand Down Expand Up @@ -1601,8 +1602,9 @@ binascii_a2b_base32_impl(PyObject *module, Py_buffer *data,
}
state = get_binascii_state(module);
if (state) {
unsigned char *bin_data_start = PyBytesWriter_GetData(writer);
PyErr_SetString(state->Error,
(octa_pos == 0 && ascii_data == data->buf)
(octa_pos == 0 && bin_data == bin_data_start)
? "Leading padding not allowed"
: "Excess padding not allowed");
}
Expand Down
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