[issue21306] PEP 466: backport hmac.compare_digest
Donald Stufft added the comment: That's also a security sensitive thing, you don't want to compare two different encoding and have it accidentally fail. Strictly speaking you can only do a constant time comparison on bytes, the fact it accepts unicode at all (even on Python 3.x) is a convenience feature. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Matthias Urlichs added the comment: Currently (Debian's 2.7.7-rc1 package) hmac.compare_digest accepts two bytestring arguments, or two Unicode stings, but not one bytestring and one unicode. I don't think that's a good idea. -- nosy: +smurfix ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Nick Coghlan added the comment: That restriction is deliberate (and documented). As a 3.x backport, this utility inherits some of Python 3's pedantry about requiring explicit conversions between binary and text data and being consistent as to which domain you're operating in. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Roundup Robot added the comment: New changeset b40f1a00b134 by Benjamin Peterson in branch '2.7': backport hmac.compare_digest to partially implement PEP 466 (closes #21306) http://hg.python.org/cpython/rev/b40f1a00b134 -- nosy: +python-dev resolution: - fixed stage: needs patch - resolved status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Donald Stufft added the comment: The attached patch looks good to me. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Alex Gaynor added the comment: Attached patch now includes documentation and should be complete. -- keywords: +needs review Added file: http://bugs.python.org/file35122/compare_digest.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Alex Gaynor added the comment: Design question here: compare_digest on Python 3 supports comparing str (text) objects, if they're both ascii-only. This feature is provided, primarily, so you can compare hexdigests or similar. Should the Python 2 version support comparing unicodes? Arguments in favor: some amount of consistency. Against: it's not necessary because hexdigest is still a str (binary), further it's not actually posisble to replicate the ascii only semantic. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Donald Stufft added the comment: try: data = data.encode(ascii) except UnicodeEncodeError: raise TypeError(comparing unicode with non-ASCII characters is not supported) ? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Nick Coghlan added the comment: 8-bit str only makes more sense to me. The wishy-washiness of some APIs in Py3 is mostly to work around porting issues where stuff that should have become bytes was left as str. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Alex Gaynor added the comment: encode(ascii) has data dependent branches, so it's to be avoided. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Alex Gaynor added the comment: Thanks Nick. I'll get a patch up for str (bytes) only this afternoon. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Donald Stufft added the comment: I'm not sure that the timing leakage in an encode is actually something to be worried about. I'm not sure what secret information would be getting leaked in a way that you could determine it by examining the timing. However I think the bigger thing is if I'm an app developer and I attempt to pass a unicode to hmac.compare_digest() and it tells me it only accepts bytes, the first thing I'm going to do is is .encode() it myself before I pass it in. IOW hmac.compare_digest could avoid the encode, but it's just pushing that back up to the user of hmac.compare_digest, who might possibly have a byte string laying around that they won't have to do the encode/decode dance on (although if they have a unicode they have already done it at least once), or they only have a unicode available to them then they'll be forced to do the encode themselves. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
Alex Gaynor added the comment: Attached patch implements compare_digest. Code is mostly a 1-1 from 3.x, except the Unicode paths are changed, and the tests are a tiny bit different. * Still needs to backport the docs. * Compares all unicode objects, not just ascii ones. If the patch looks good to folks I'll add the docs as well. -- keywords: +patch Added file: http://bugs.python.org/file35005/compare_digest.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21306] PEP 466: backport hmac.compare_digest
New submission from Nick Coghlan: Tracker issue for the hmac.compare_digest backport to 2.7 described in PEP 466. -- messages: 216826 nosy: alex, benjamin.peterson, christian.heimes, dstufft, giampaolo.rodola, janssen, ncoghlan, pitrou priority: normal severity: normal stage: needs patch status: open title: PEP 466: backport hmac.compare_digest type: enhancement versions: Python 2.7 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21306 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
