HMAC.copy() does not correctly copy its attributes

[YuanchengJiang]

Crash report

What happened?

import hmac
import hashlib

h = hmac.HMAC(b'key', digestmod=hashlib.sha256)
h_copy = h.copy()
print(h_copy.name)

python: ../Modules/_hashopenssl.c:610: const char *get_asn1_utf8name_by_nid(int): Assertion `ERR_peek_last_error() != 0' failed

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Output from running 'python -VV' on the command line:

No response

Linked PRs

• gh-142451: correctly copy HMAC attributes in HMAC.copy() #142510
• [3.14] gh-142451: correctly copy HMAC attributes in HMAC.copy() (GH-142510) #142698
• [3.13] gh-142451: correctly copy HMAC attributes in HMAC.copy() (GH-142510) #142701

[yihong0618]

macos works fine

python3.14 works fine

it happens in linux main

errror

Traceback (most recent call last):
  File "/home/yihong/cpython/ttt.py", line 6, in <module>
    print(h_copy.name)
          ^^^^^^^^^^^
  File "/home/yihong/cpython/Lib/hmac.py", line 157, in name
    return self._hmac.name
           ^^^^^^^^^^^^^^^
ValueError: [object identifier routines] unknown nid

seems with openssl problen

yihong@ubuntu:~/cpython$ openssl version
OpenSSL 3.3.1 4 Jun 2024 (Library: OpenSSL 3.3.1 4 Jun 2024)

[yihong0618]

bisect this commit bring this issue

cc @picnixz

b9c50b4

[picnixz]

OK, I know the issue. I forgot to copy the evp_md_nid in hmac.copy so it get initialized to 0, which leads to a crash. Thanks for catching this!

Note: I'm actually surprised that the error indicator is not set in this case, because it goes against OpenSSL docs actually:

OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID n to an ASN1_OBJECT structure, its long name and its short name respectively, or NULL if an error occurred.

[picnixz]

So actually we have two issues:

• On some OpenSSL versions it seems that OBJ_nid2obj may return NULL without an error indicator set (which is a bit weird though but I guess I can also remove the assertion, it could have been a too strict guard).
• The copy is lacking the NID because I forgot to copy the field as well...

[yihong0618]

So actually we have two issues:

• On some OpenSSL versions it seems that OBJ_nid2obj may return NULL without an error indicator set (which is a bit weird though but I guess I can also remove the assertion, it could have been a too strict guard).
• The copy is lacking the NID because I forgot to copy the field as well...

yes different OpenSSL version behavior

[picnixz]

Thank you for the report!