def decode_b(encoded):
defects = []
pad_err = len(encoded) % 4
if pad_err:
defects.append(errors.InvalidBase64PaddingDefect())
padded_encoded = encoded + b'==='[:4 - pad_err]
else:
padded_encoded = encoded
try:
return base64.b64decode(padded_encoded, validate=True), defects
except binascii.Error:
# Since we had correct padding, this must an invalid char error.
defects = [errors.InvalidBase64CharactersDefect()]
# The non-alphabet characters are ignored as far as padding
# goes, but we don't know how many there are. So we'll just
# try various padding lengths until something works.
for i in 0, 1, 2, 3:
try:
return base64.b64decode(encoded + b'=' * i,
validate=False), defects
except binascii.Error:
if i == 0:
defects.append(errors.InvalidBase64PaddingDefect())
else:
# This should never happen.
raise AssertionError("unexpected binascii.Error")
def decode_b(encoded):
# First try encoding with validate=True, fixing the padding if needed.
# This will succeed only if encoded includes no invalid characters.
pad_err = len(encoded) % 4
missing_padding = b'==='[:4 - pad_err] if pad_err else b''
try:
return (
base64.b64decode(encoded + missing_padding, validate=True),
[errors.InvalidBase64PaddingDefect()] if pad_err else [],
)
except binascii.Error:
# Since we had correct padding, this is likely an invalid char error.
#
# The non-alphabet characters are ignored as far as padding
# goes, but we don't know how many there are. So try without adding
# padding to see if it works.
try:
return (
base64.b64decode(encoded, validate=False),
[errors.InvalidBase64CharactersDefect()],
)
except binascii.Error:
# Add as much padding as could possibly be necessary (extra padding
# is ignored).
try:
return (
base64.b64decode(encoded + b'==', validate=False),
[
errors.InvalidBase64CharactersDefect(),
errors.InvalidBase64PaddingDefect()
],
)
except binascii.Error:
# This only happens when the encoded string's length is 1 more
# than a multiple of 4, which is invalid.
#
# bpo-27397: Just return the encoded string since there's no
# way to decode.
return encoded, [errors.InvalidBase64LengthDefect()]
def decode_b(encoded):
pad_err = len(encoded) % 4
missing_padding = '==='[:4 - pad_err] if pad_err else ''
try:
return (
base64.b64decode((encoded + missing_padding), validate=True),
[errors.InvalidBase64PaddingDefect()] if pad_err else [])
except binascii.Error:
try:
return (
base64.b64decode(encoded, validate=False),
[
errors.InvalidBase64CharactersDefect()])
except binascii.Error:
try:
return (
base64.b64decode((encoded + '=='), validate=False),
[
errors.InvalidBase64CharactersDefect(),
errors.InvalidBase64PaddingDefect()])
except binascii.Error:
return (
encoded, [errors.InvalidBase64LengthDefect()])
def decode_b(encoded):
defects = []
pad_err = len(encoded) % 4
if pad_err:
defects.append(errors.InvalidBase64PaddingDefect())
padded_encoded = encoded + b'==='[:4 - pad_err]
else:
padded_encoded = encoded
try:
return (base64.b64decode(padded_encoded, validate=True), defects)
except binascii.Error:
defects = [errors.InvalidBase64CharactersDefect()]
for i in (0, 1, 2, 3):
try:
return (base64.b64decode(encoded + b'=' * i,
validate=False), defects)
except binascii.Error:
if i == 0:
defects.append(errors.InvalidBase64PaddingDefect())
raise AssertionError('unexpected binascii.Error')
