Re: how to get keyslog PBKDF settings via libcryptsetup

Jonas Meurer <[email protected]> Fri, 31 Jan 2020 14:55:49 +0100

Newsgroups	gmane.linux.kernel.device-mapper.dm-crypt
Message-ID	<[email protected]>

Hello,

Ondrej Kozina:
> For anyone interested,
> 
> there was a minor bug in LUKS1 crypt_keyslot_get_pbkdf() where we
> returned pbkdf values even for an inactive keyslot. It was fixed with
> commit
> https://gitlab.com/cryptsetup/cryptsetup/commit/47d0cf495dae03822c76ef2ef482f940208d9062
> and it will get distributed with upstream 2.3.0 release.

And for anyone interested in my code example, the major bug was there. I
passed 'ki' (which is the flag that indicates the keyslot status)
instead of 'j' (the keyslot number) to crypt_keyslot_get_pbkdf(). Thanks
to Ondrej for pointing that out!

Here's a fixed version of my example code:

#include <stdlib.h>
#include <stdio.h>
#include <err.h>
#include <string.h>

#include <libcryptsetup.h>

int main(int argc, char *argv[]) {
    if (argc != 3 || (strcmp(argv[1], CRYPT_LUKS1) != 0 &&
strcmp(argv[1], CRYPT_LUKS2) != 0))
        errx(EXIT_FAILURE, "expects LUKS1/LUKS2 as first and LUKS device
as second argument");
    struct crypt_device *cd = NULL;
    if (crypt_init(&cd, argv[2]) < 0)
        err(EXIT_FAILURE, "crypt_init failed");
    if (crypt_load(cd, argv[1], NULL) < 0)
        err(EXIT_FAILURE, "crypt_load failed");
    fprintf(stderr, "Device %s (type %s)\n", argv[2], crypt_get_type(cd));
    int ks_max = crypt_keyslot_max(crypt_get_type(cd));
    for (int j = 0; j < ks_max; j++) {
        crypt_keyslot_info ki = crypt_keyslot_status(cd, j);
        if (ki != CRYPT_SLOT_ACTIVE && ki != CRYPT_SLOT_ACTIVE_LAST)
            continue;
        fprintf(stderr, "Active keyslot %d: %d\n", j, ki);
        struct crypt_pbkdf_type pbkdf_ki;
        int res = crypt_keyslot_get_pbkdf(cd, j, &pbkdf_ki);
        fprintf(stderr, "  return code: %d\n", res);
        fprintf(stderr, "  iterations: %d\n", pbkdf_ki.iterations);
        fprintf(stderr, "  max_memory_kb: %d\n", pbkdf_ki.max_memory_kb);
    }
    crypt_free(cd);
}

Cheers
 jonas

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