Re: Is there any userland implementations of fscrypt

[Eric Biggers <ebiggers@kernel.org>]

[+Cc linux-fscrypt]

On Mon, Mar 20, 2023 at 06:49:29PM +0800, Xiubo Li wrote:
> Hi Eric,
> 
> BTW, I am planing to support the fscrypt in userspace ceph client. Is there
> any userland implementation of fscrypt ? If no then what should I use
> instead ?
> 

I assume that you mean userspace code that encrypts files the same way the
kernel does?

There's some code in xfstests that reproduces all the fscrypt encryption for
testing purposes
(https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/tree/src/fscrypt-crypt-util.c?h=for-next).
It does *not* use production-quality implementations of the algorithms, though.
It just has minimal implementations for testing without depending on OpenSSL.

Similar testing code can also be found in Android's vts_kernel_encryption_test
(https://android.googlesource.com/platform/test/vts-testcase/kernel/+/refs/heads/master/encryption).
It uses BoringSSL for the algorithms when possible, but unlike the xfstest it
does not test filenames encryption.

There's also some code in mkfs.ubifs in mtd-utils
(http://git.infradead.org/mtd-utils.git) that supports creating encrypted files.
However, it's outdated since it only supports policy version 1.

Which algorithms do you need to support?  The HKDF-SHA512 + AES-256-XTS +
AES-256-CTS combo shouldn't be hard to support if your program can depend on
OpenSSL (1.1.0 or later).

- Eric