lkml.org 
[lkml]   [2019]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH 1/5 v2] PM / hibernate: Create snapshot keys handler
    Date
    Am Mittwoch, 9. Januar 2019, 09:21:04 CET schrieb Eric Biggers:

    Hi Eric,
    >
    > FWIW, it's been very slow going since I've been working on other projects
    > and I also need to be very sure to get the API changes right, but I still
    > plan to change the KDF in fscrypt (a.k.a. ext4/f2fs/ubifs encryption) to
    > HKDF-SHA512 as part of a larger set of improvements to how fscrypt
    > encryption keys are managed. I sent the last patchset a year ago
    > (https://marc.info/?l=linux-fsdevel&m=150879493206257) but I'm working to
    > revive it. In the work-in-progress version in my git tree, this is the
    > commit that adds a HKDF implementation as fs/crypto/hkdf.c:
    > https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/commit/?i
    > d=e8a78767131c9717ee838f0c4e307948d65a4427 It basically just wraps a
    > crypto_shash for "hmac(sha512)".
    >
    > I'd be fine with using a common implementation instead, provided that it
    > gives the same functionality, including supporting user-specified salt and
    > application-specific info strings, and isn't slower or more complex to use.
    >
    > (This comment is solely on the tangential discussion about KDF
    > implementations; I've not looked at the hibernation image encryption stuff
    > yet.)

    Thanks for the clarification. I have started a generic HKDF implementation for
    the kernel crypto API which lead to the questions above. I would then also try
    to provide a HKDF proposal.

    To use the (H)KDF, I currently envision 2 calls apart from alloc/free. The
    following code would serve as an example.

    * Example without proper error handling:
    * char *keying_material = "\x00\x11\x22\x33\x44\x55\x66\x77";
    * char *label_context = "\xde\xad\xbe\xef\x00\xde\xad\xbe\xef";
    * kdf = crypto_alloc_rng(name, 0, 0);
    * crypto_rng_reset(kdf, keying_material, 8);
    * crypto_rng_generate(kdf, label_context, 9, outbuf, outbuflen);

    That hopefully should be simple enough.

    For HKDF, as mentioned, I would envision to use a struct instead of a char *
    for the label_context to communicate IKM, Salt, and the label/info
    information.

    Ciao
    Stephan


    \
     
     \ /
      Last update: 2019-01-09 11:19    [W:4.083 / U:0.220 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site