After upgrading to Python 3.7.5, several algorithms are unavailable in the hashlib module.

This seems to have been caused by the "fix" for https://bugs.python.org/issue33936. I will submit a PR with a more appropriate change shortly.

Python 3.7.4:
>>> hashlib.algorithms_available
{'ripemd160', 'blake2s256', 'sha512', 'sha3-224', 'sha3_224', 'blake2s', 'shake_128', 'sha3-384', 'sha3_384', 'whirlpool', 'md4', 'md5', 'sha512-224', 'sha3-512', 'sha1', 'blake2b', 'sha384', 'md5-sha1', 'sha3-256', 'shake_256', 'mdc2', 'sha224', 'blake2b512', 'shake128', 'sm3', 'sha256', 'shake256', 'sha3_512', 'sha512-256', 'sha3_256'}

Python 3.7.5:
>>> hashlib.algorithms_available
{'sha224', 'sha256', 'sha3_224', 'blake2s', 'md5', 'sha3_256', 'sha384', 'sha3_512', 'sha3_384', 'shake_256', 'blake2b', 'sha512', 'shake_128', 'sha1'}

According to OpenSSL documentation it is not necessary to call any init function. All ciphers and all digests are default options.

As of version 1.1.0 OpenSSL will automatically allocate all resources that it needs so no explicit initialisation is required. Similarly it will also automatically deinitialise as required.

OPENSSL_INIT_ADD_ALL_CIPHERS
With this option the library will automatically load and make available all libcrypto ciphers. This option is a default option.

OPENSSL_INIT_ADD_ALL_DIGESTS
With this option the library will automatically load and make available all libcrypto digests. This option is a default option.

https://www.openssl.org/docs/man1.1.0/man3/OPENSSL_init_crypto.html

Then the OpenSSL documentation is wrong, or Python is subsequently doing something to disable some algorithms.

I see that generate_hash_name_list() calls EVP_MD_do_all() which calls  OPENSSL_init_crypto(OPENSSL_INIT_ADD_ALL_DIGESTS, NULL);

I'm not sure why that doesn't do the job here.

Ok, so this appears to be working correctly on master. Just the 3.7 branch is broken.

I think this is because we use OBJ_NAME_do_all instead of EVP_MD_do_all in 3.7.

I think backporting https://github.com/python/cpython/pull/16083 to 3.7 would resolve this.