On Tue, Mar 21, 2023 at 09:03:02AM +0800, Xiubo Li wrote: > On 21/03/2023 05:19, Eric Biggers wrote: > > [+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? > > Yeah, a library just likes the fs/crypto/ in kernel space. > > I found the libkcapi, Linux Kernel Crypto API User Space Interface > Library(http://www.chronox.de/libkcapi.html) seems exposing the APIs from > crypto/ not the fs/crypto/. Much of fs/crypto/ is tightly coupled to how the Linux kernel implements filesystems, so I'm not sure what you are expecting exactly! The actual cryptography can definitely be replicated in userspace, though. > > 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. > > This is performed in software. > > > 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. > > This too. So you are looking for something that is *not* performed in software? What do you mean by that, exactly? Are you looking to use an off-CPU hardware crypto accelerator? The Linux kernel exposes those to userspace through AF_ALG. Though, it's worth noting that that style of crypto acceleration has fallen a bit out of favor these days, as modern CPUs have crypto instructions built-in. > > 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 However, it's outdated since it only supports policy version 1.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). > > Yeah, ceph has already depended on the OpenSSL. > > I think the OpenSSL will be the best choice for now. That seems like the right choice. Note that that is "software" too, but I think that's what you want! - Eric
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