On 2019-08-09 19:21, Larry Martell wrote:
On Fri, Aug 9, 2019 at 12:23 PM Chris Angelico <ros...@gmail.com> wrote:
On Sat, Aug 10, 2019 at 2:09 AM Larry Martell <larry.mart...@gmail.com> wrote:
>
> I have some python 2 code:
>
> def decode(key, string):
> decoded_chars = []
> string = base64.urlsafe_b64decode(string)
> for i in range(len(string)):
> key_c = key[i % len(key)]
> encoded_c = chr(abs(ord(string[i]) - ord(key_c) % 256))
> decoded_chars.append(encoded_c)
> decoded_string = "".join(decoded_chars)
> return decoded_string
>
> and if I call it like this in py2 it works as expected:
>
> s = 'V3NYVY95iImnnJWCmqphWFFzU1qvqsV6x83Mxa7HipZitZeMxbe709jJtbfW6Y6blQ=='
> key = '!@#$VERYsecRet)('
> decode(key, s)
>
> In py3 it fails with
>
> TypeError: ord() expected string of length 1, but int found
>
> I know that in py3 base64.urlsafe_b64decode is returning bytes not
> chars and that is what that is happening, and I thought the solution
> would be to decode it, but what codec would I use for this?
Should be safe to decode it as ASCII, since Base 64 uses strictly
ASCII characters. But since you're working with bytes, possibly all
you need to do is remove the ord calls, since ord(u"x") is the same as
b"x"[0]. You'll then need to change the join() at the end to be just
"decoded_string = bytes(decoded_chars)", or possibly that followed by
a decode-to-text, depending on how your data works.
That doesn't work:
-> encoded_c = chr(abs(string[i] - ord(key_c) % 256))
(Pdb) n
TypeError: "unsupported operand type(s) for -: 'str' and 'int'"
(Pdb) string
'WsXU\x8fy\x88\x89\xa7\x9c\x95\x82\x9a\xaaaXQsSZ\xaf\xaa\xc5z\xc7\xcd\xcc\xc5\xae\xc7\x8a\x96b\xb5\x97\x8c\xc5\xb7\xbb\xd3\xd8\xc9\xb5\xb7\xd6\xe9\x8e\x9b\x95'
(Pdb) string[i]
'\x8f'
(Pdb) bytes(string[i])
'\x8f'
(Pdb) type(string[i])
<type 'str'>
'string' is a 'str' (in Python 2 that would've been 'unicode'), so
string[i] is also a 'str' and you need 'ord':
encoded_c = chr(abs(ord(string[i]) - ord(key_c) % 256))
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