openssl: Bug (crash) when stopping provider

Detailed story is in this issue, though I’d recommend starting here.

TL;DR OpenSSL crashes after running liboqs tests, hitting NULL ptr when cleaning up/deallocating things. Great analysis is here. It occurs when several “additional” providers are defined in openssl.cnf - by “additional” I mean pkcs11-provider and oqs-provider, though legacy provider seems to also contribute to this problem when it’s defined (I stopped enabling it, precisely because of that).

Quoting from the referring issue:

With both pkcs11-provider and oqs-provider enabled - liboqs tests will pass (reporting == 464 passed, 220 skipped in 40.80s ==), but crash in the end:

Segmentation fault
FAILED: tests/CMakeFiles/run_tests /Users/ur20980/src/liboqs/build/tests/CMakeFiles/run_tests 
cd /Users/ur20980/src/liboqs && /opt/local/bin/cmake -E env OQS_BUILD_DIR=/Users/ur20980/src/liboqs/build python3 -m pytest --verbose --numprocesses=auto --ignore=scripts/copy_from_upstream/repos
ninja: build stopped: subcommand failed.

and crash report:

Termination Reason:    Namespace SIGNAL, Code 11 Segmentation fault: 11
Terminating Process:   exc handler [18302]

VM Region Info: 0 is not in any region.  Bytes before following region: 4310319104
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                      100ea4000-100ea8000    [   16K] r-x/r-x SM=COW  .../MacOS/Python

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   libsystem_pthread.dylib       	       0x1a1c948c4 pthread_rwlock_wrlock + 0
1   libcrypto.3.dylib             	       0x10564add4 CRYPTO_THREAD_write_lock + 12 (threads_pthread.c:110)
2   libcrypto.3.dylib             	       0x1055f2c14 ERR_unload_strings + 92 (err.c:314)
3   libcrypto.3.dylib             	       0x105647720 ossl_provider_free + 92 (provider_core.c:688)
4   libcrypto.3.dylib             	       0x1056ad138 OPENSSL_sk_pop_free + 76 (stack.c:439)
5   libcrypto.3.dylib             	       0x105647104 sk_OSSL_PROVIDER_pop_free + 12 (provider_core.c:199) [inlined]
6   libcrypto.3.dylib             	       0x105647104 ossl_provider_store_free + 76 (provider_core.c:295)
7   libcrypto.3.dylib             	       0x105637d6c context_deinit_objs + 124 (context.c:250)
8   libcrypto.3.dylib             	       0x105637564 context_deinit + 16 (context.c:334) [inlined]
9   libcrypto.3.dylib             	       0x105637564 OSSL_LIB_CTX_free + 132 (context.c:465)
10  oqsprovider.0.5.0-dev.dylib   	       0x10436f560 oqsx_freeprovctx + 24 (oqsprov_keys.c:178)
11  oqsprovider.0.5.0-dev.dylib   	       0x10436e9a0 oqsprovider_teardown + 12 (oqsprov.c:553)
12  libcrypto.3.dylib             	       0x104547400 ossl_provider_free + 76
13  libcrypto.3.dylib             	       0x10459b5a0 OPENSSL_sk_pop_free + 60
14  libcrypto.3.dylib             	       0x104546ec0 ossl_provider_store_free + 72
15  libcrypto.3.dylib             	       0x10453b5c4 context_deinit_objs + 124
16  libcrypto.3.dylib             	       0x10453ae5c context_deinit + 32
17  libcrypto.3.dylib             	       0x10453ae2c ossl_lib_ctx_default_deinit + 20
18  libcrypto.3.dylib             	       0x10453dd80 OPENSSL_cleanup + 204
19  libsystem_c.dylib             	       0x1a1b55ed4 __cxa_finalize_ranges + 492
20  libsystem_c.dylib             	       0x1a1b55c4c exit + 44
21  libdyld.dylib                 	       0x1a1cb0554 dyld4::LibSystemHelpers::exit(int) const + 20
22  dyld                          	       0x1a193ff7c start + 2320