def add_padding(b):
# add padding chars
m = len(b) % 4
if m == 1:
# NOTE: for some reason b64decode raises *TypeError* if the
# padding is incorrect.
raise BadSyntax(b, "incorrect padding")
elif m == 2:
b += b"=="
elif m == 3:
b += b"="
return b
def b64d(b):
"""Decode some base64-encoded bytes.
Raises BadSyntax if the string contains invalid characters or padding.
:param b: bytes
"""
cb = b.rstrip(b"=") # shouldn't but there you are
# Python's base64 functions ignore invalid characters, so we need to
# check for them explicitly.
if not _b64_re.match(cb):
raise BadSyntax(cb, "base64-encoded data contains illegal characters")
if cb == b:
b = add_padding(b)
return base64.urlsafe_b64decode(b)
def split_token(token):
if not token.count(b"."):
raise BadSyntax(token, "expected token to contain at least one dot")
return tuple(token.split(b"."))