Building cifs.ko without any support for insecure crypto?

Steve French smfrench at
Tue Aug 24 16:41:01 UTC 2021

On Mon, Aug 23, 2021 at 5:05 AM Simo Sorce <simo at> wrote:
> Another way to handle this part is to calculate the hash in userspace
> and handle the kernel just the hashes. This would allow you to remove
> MD4 from the kernel. I guess it would break putting a password on the
> kernel command line, but is that really a thing to do? Kernels do not
> boot from cifs shares so you can always use userspace tools (or pass
> hexed hashes directly on the command line in a pinch).

We can boot from cifs (and given the security features of SMB3.1.1 it probably
makes more sense than some of the alternatives) albeit with some POSIX
restrictions unless booting from ksmbd with POSIX extensions enabled.
Paulo added the support for booting from cifs.ko in the 5.5 kernel.

> > I have patches for both DES removal and forking ARC4 prepared for linux-cifs.
> > MD4 will require more work since we use it via the crypto_alloc_hash()
> > api but we will do that too.
> >
> > What about MD5? Is it also scheduled for removal? if so we will need
> > to fork it too.
> MD5 is still used for a ton of stuff, however it may make sense to
> consider moving it in /lib and our of /lib/crypto as it is not usable
> in cryptographic settings anymore anyway.

Seems reasonable



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