The need for this feature/functionality in the fist place is questioned by some:
> As someone who works on the Linux kernel's cryptography code, the regularly occurring AF_ALG exploits are really frustrating. AF_ALG, which was added to the kernel many years ago without sufficient review, should not exist. It's very complex, and it exposes a massive attack surface to unprivileged userspace programs. And it's almost completely unnecessary, as userspace already has its own cryptography code to use. The kernel's cryptography code is just for in-kernel users (for example, dm-crypt).
> The algorithm being used in this [specific] exploit, "authencesn", is even an IPsec implementation detail, which never should have been exposed to userspace as a general-purpose en/decryption API. […]
* https://news.ycombinator.com/item?id=47952181#unv_47956312
More than one time.
> a cryptographic performance enhancement feature
It's very rarely used.
> Did we blacklist OpenSSL's binaries after Heartbleed?
No, but lots of companies have since migrated away. OpenSSL was harder to move away from because there weren't as obvious drop-in replacements. Blocking a syscall that you never actually used is simple and effective.
But I am disappointed that we still don't have clear OpenSSL successor, there is nothing to be salvaged from this mess of a project
Yes, the syscall API is (famously) stable, but the drivers, for example, are such a mess that many non-Linux projects prefer to take BSD drivers for e.g. WiFi despite them supporting far fewer devices (even if the Linux ones would be license compatible).
To my knowledge, not many things were using the in-kernel code anyways, the recommended way is to use userland tools...
It's optional for openssl, systemd apparently needs it, but deleting the module from one of my systems didn't cause any issues. /shrug