On Fri, 16 Aug 2024, Ingo Franzki wrote:
> For the MAC based integrity operation, the integrity key size (i.e.
> key_mac_size) is currently set to the digest size of the used digest.
>
> For wrapped key HMAC algorithms, the key size is independent of the
> cryptographic key size. So there is no known size of the mac key in
> such cases. The desired key size can optionally be specified as argument
> when the dm-crypt device is configured via 'integrity_key_size:%u'.
> If no integrity_key_size argument is specified, the mac key size
> is still set to the digest size, as before.
>
> Increase version number to 1.28.0 so that support for the new
> argument can be detected by user space (i.e. cryptsetup).
Hi
I know you already discussed it with Milan. I'd like to ask, what's the
reason for this patch? Milan said that you need it for mainframes -
please, describe the specific configuration when this patch is needed.
Mikulas
> Signed-off-by: Ingo Franzki <ifran...@linux.ibm.com>
> ---
> Documentation/admin-guide/device-mapper/dm-crypt.rst | 4 ++++
> drivers/md/dm-crypt.c | 11 +++++++++--
> 2 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/device-mapper/dm-crypt.rst
> b/Documentation/admin-guide/device-mapper/dm-crypt.rst
> index e625830d335e..636b47c582f0 100644
> --- a/Documentation/admin-guide/device-mapper/dm-crypt.rst
> +++ b/Documentation/admin-guide/device-mapper/dm-crypt.rst
> @@ -160,6 +160,10 @@ iv_large_sectors
> The <iv_offset> must be multiple of <sector_size> (in 512 bytes units)
> if this flag is specified.
>
> +integrity_key_size:<bytes>
> + Use an integrity key of <bytes> size instead of using an integrity key
> size
> + of the digest size of the used HMAC algorithm.
> +
>
> Module parameters::
> max_read_size
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index 348b4b26c272..c4c706115870 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -2937,7 +2937,8 @@ static int crypt_ctr_auth_cipher(struct crypt_config
> *cc, char *cipher_api)
> if (IS_ERR(mac))
> return PTR_ERR(mac);
>
> - cc->key_mac_size = crypto_ahash_digestsize(mac);
> + if (!cc->key_mac_size)
> + cc->key_mac_size = crypto_ahash_digestsize(mac);
> crypto_free_ahash(mac);
>
> cc->authenc_key = kmalloc(crypt_authenckey_size(cc), GFP_KERNEL);
> @@ -3219,6 +3220,12 @@ static int crypt_ctr_optional(struct dm_target *ti,
> unsigned int argc, char **ar
> cc->cipher_auth = kstrdup(sval, GFP_KERNEL);
> if (!cc->cipher_auth)
> return -ENOMEM;
> + } else if (sscanf(opt_string, "integrity_key_size:%u", &val) ==
> 1) {
> + if (val == 0) {
> + ti->error = "Invalid integrity_key_size
> argument";
> + return -EINVAL;
> + }
> + cc->key_mac_size = val;
> } else if (sscanf(opt_string, "sector_size:%hu%c",
> &cc->sector_size, &dummy) == 1) {
> if (cc->sector_size < (1 << SECTOR_SHIFT) ||
> cc->sector_size > 4096 ||
> @@ -3758,7 +3765,7 @@ static void crypt_io_hints(struct dm_target *ti, struct
> queue_limits *limits)
>
> static struct target_type crypt_target = {
> .name = "crypt",
> - .version = {1, 27, 0},
> + .version = {1, 28, 0},
> .module = THIS_MODULE,
> .ctr = crypt_ctr,
> .dtr = crypt_dtr,
> --
> 2.43.0
>
