Re: [PATCH 02/11] crypto: enforce that LUKS stripes is always a fixed value

[Richard W.M. Jones]

On Tue, Sep 06, 2022 at 09:41:38AM +0100, Daniel P. Berrangé wrote:
> Although the LUKS stripes are encoded in the keyslot header and so
> potentially configurable, in pratice the cryptsetup impl mandates
> this has the fixed value 4000. To avoid incompatibility apply the
> same enforcement in QEMU too. This also caps the memory usage for
> key material when QEMU tries to open a LUKS volume.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  crypto/block-luks.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/crypto/block-luks.c b/crypto/block-luks.c
> index 27d1b34c1d..81744e2a8e 100644
> --- a/crypto/block-luks.c
> +++ b/crypto/block-luks.c
> @@ -582,8 +582,9 @@ qcrypto_block_luks_check_header(const QCryptoBlockLUKS 
> *luks, Error **errp)
>                                                     header_sectors,
>                                                     slot1->stripes);
>  
> -        if (slot1->stripes == 0) {
> -            error_setg(errp, "Keyslot %zu is corrupted (stripes == 0)", i);
> +        if (slot1->stripes != QCRYPTO_BLOCK_LUKS_STRIPES) {
> +            error_setg(errp, "Keyslot %zu is corrupted (stripes %d != %d)",
> +                       i, slot1->stripes, QCRYPTO_BLOCK_LUKS_STRIPES);
>              return -1;
>          }

In nbdkit I decided to just check that this number < 10000, but I
agree that the only important implementation (the kernel) always fixes
this at 4000 (cryptsetup.git/lib/keymanage.c), so:

Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

Rich.

-- 
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