Skip to content

[3.7] bpo-33770: improve base64 exception message for encoded inputs of invalid length (GH-7416) #7602

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ned-deily merged 1 commit into from
Jun 10, 2018
Merged

[3.7] bpo-33770: improve base64 exception message for encoded inputs of invalid length (GH-7416) #7602

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 28 additions & 0 deletions Lib/test/test_binascii.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,34 @@ def addnoise(line):
# empty strings. TBD: shouldn't it raise an exception instead ?
self.assertEqual(binascii.a2b_base64(self.type2test(fillers)), b'')

def test_base64errors(self):
# Test base64 with invalid padding
def assertIncorrectPadding(data):
with self.assertRaisesRegex(binascii.Error, r'(?i)Incorrect padding'):
binascii.a2b_base64(self.type2test(data))

assertIncorrectPadding(b'ab')
assertIncorrectPadding(b'ab=')
assertIncorrectPadding(b'abc')
assertIncorrectPadding(b'abcdef')
assertIncorrectPadding(b'abcdef=')
assertIncorrectPadding(b'abcdefg')
assertIncorrectPadding(b'a=b=')
assertIncorrectPadding(b'a\nb=')

# Test base64 with invalid number of valid characters (1 mod 4)
def assertInvalidLength(data):
with self.assertRaisesRegex(binascii.Error, r'(?i)invalid.+length'):
binascii.a2b_base64(self.type2test(data))

assertInvalidLength(b'a')
assertInvalidLength(b'a=')
assertInvalidLength(b'a==')
assertInvalidLength(b'a===')
assertInvalidLength(b'a' * 5)
assertInvalidLength(b'a' * (4 * 87 + 1))
assertInvalidLength(b'A\tB\nC ??DE') # only 5 valid characters

def test_uu(self):
MAX_UU = 45
for backtick in (True, False):
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2018-06-05-11-29-26.bpo-33770.oBhxxw.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
improve base64 exception message for encoded inputs of invalid length
13 changes: 12 additions & 1 deletion Modules/binascii.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -510,7 +510,18 @@ binascii_a2b_base64_impl(PyObject *module, Py_buffer *data)
}

if (leftbits != 0) {
PyErr_SetString(Error, "Incorrect padding");
if (leftbits == 6) {
/*
** There is exactly one extra valid, non-padding, base64 character.
** This is an invalid length, as there is no possible input that
** could encoded into such a base64 string.
*/
PyErr_SetString(Error,
"Invalid base64-encoded string: "
"length cannot be 1 more than a multiple of 4");
} else {
PyErr_SetString(Error, "Incorrect padding");
}
_PyBytesWriter_Dealloc(&writer);
return NULL;
}
Expand Down