bpo-40645: use C implementation of HMAC

[tiran]

• fix tests
• add test scenarios for old/new code.

Signed-off-by: Christian Heimes [email protected]

https://bugs.python.org/issue40645

Automerge-Triggered-By: GH:tiran

[gpshead]

This makes the assumption that if we have _hashopenssl, all possible digests anyone could use will be available as part of openssl for use via its hmac implementation. I don't think that is necessarily true. A digestmod that supplies a string name can be supplied but not be something available in openssl.

presumably the easiest way around this while retaining the optimal openssl computation when possible is to catch an exception from _init_hmac (due to _hashopenssl.hmac_new raising) and fall back to _init_old instead.

a test should be added to cover this case. (via a custom digestmod-like-object with a name and blocksize perhaps)

[gpshead]

fallback logic needed here as when digestname isn't supported by openssl.

[bedevere-bot]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[tiran]

Thanks for the feedback, @gpshead!

I'm not happy with the first draft. It's not elegant. It's easier to track builtin constructors in C and map them directly in _hashopenssl.c.

[pablogsal]

Seems that commit 933dfd7 introduced some reference leaks:

commit 933dfd7
Author: Christian Heimes [email protected]
Date: Sat Mar 27 14:55:03 2021 +0100

[bpo-40645](https://bugs.python.org/issue40645): use C implementation of HMAC (GH-24920) 

𓋹 ./python.exe -m test test_hashlib -R 3:3
0:00:00 load avg: 5.67 Run tests sequentially
0:00:00 load avg: 5.67 [1/1] test_hashlib
beginning 6 repetitions
123456
......
test_hashlib leaked [1, 1, 1] references, sum=3
test_hashlib failed

== Tests result: FAILURE ==

1 test failed:
test_hashlib

Total duration: 8.7 sec
Tests result: FAILURE

- [x] fix tests - [ ] add test scenarios for old/new code. Signed-off-by: Christian Heimes <[email protected]> 

Lib/hashlib.py | 1 +
Lib/hmac.py | 86 +++++++-----
Lib/test/test_hmac.py | 114 +++++++++-------
.../2021-03-19-10-22-17.bpo-40645.5pXhb-.rst | 2 +
Modules/_hashopenssl.c | 150 +++++++++++++++++++--
Modules/clinic/_hashopenssl.c.h | 38 +-----
6 files changed, 267 insertions(+), 124 deletions(-)
create mode 100644 bpo-40645.5pXhb-.rst">Misc/NEWS.d/next/Library/2021-03-19-10-22-17.bpo-40645.5pXhb-.rst

[pablogsal]

Opened #25063 to address it