This comes from Dmitry author of the previously submitted LUKS2 master
key support. Since he's not on the list, I'm taking some of his
response and re-posting it here (modified to be faithful to his
original message) and will add him to future discussions on this.
Glenn
On Tue, 4 Jan 2022 21:25:14 +0300
Dmitry <reagen...@gmail.com> wrote:
> Signed-off-by: John Lane <j...@lane.uk.net>
> gnu...@cyberdimension.org: rebase, patch split, small fixes, commit message
> Signed-off-by: Denis 'GNUtoo' Carikli <gnu...@cyberdimension.org>
> developm...@efficientek.com: rebase, rework for cryptomount parameter passing
> Signed-off-by: Glenn Washburn <developm...@efficientek.com>
> ---
> grub-core/disk/cryptodisk.c | 15 ++++++++++++++-
> grub-core/disk/geli.c | 10 ++++++++++
> grub-core/disk/luks.c | 8 ++++++++
> grub-core/disk/luks2.c | 8 ++++++++
> include/grub/cryptodisk.h | 2 ++
> include/grub/file.h | 2 ++
> 6 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index 497097394..e90f680f0 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -42,6 +42,7 @@ static const struct grub_arg_option options[] =
> {"all", 'a', 0, N_("Mount all."), 0, 0},
> {"boot", 'b', 0, N_("Mount all volumes with `boot' flag set."), 0, 0},
> {"password", 'p', 0, N_("Password to open volumes."), 0,
> ARG_TYPE_STRING},
> + {"header", 'H', 0, N_("Read header from file"), 0, ARG_TYPE_STRING},
> {0, 0, 0, 0, 0, 0}
> };
>
> @@ -1173,6 +1174,18 @@ grub_cmd_cryptomount (grub_extcmd_context_t ctxt, int
> argc, char **args)
> cargs.key_len = grub_strlen (state[3].arg);
> }
>
> + if (state[4].set) /* Detached header */
> + {
> + if (state[0].set)
> + return grub_error (GRUB_ERR_BAD_ARGUMENT,
> + N_("Cannot use UUID lookup with detached header"));
> +
> + cargs.hdr_file = grub_file_open (state[4].arg,
> + GRUB_FILE_TYPE_CRYPTODISK_DETACHED_HEADER);
> + if (!cargs.hdr_file)
> + return grub_errno;
> + }
> +
> if (state[0].set) /* uuid */
> {
> int found_uuid;
> @@ -1385,7 +1398,7 @@ GRUB_MOD_INIT (cryptodisk)
> {
> grub_disk_dev_register (&grub_cryptodisk_dev);
> cmd = grub_register_extcmd ("cryptomount", grub_cmd_cryptomount, 0,
> - N_("[-p password] <SOURCE|-u UUID|-a|-b>"),
> + N_("[-p password] [-H file] <SOURCE|-u
> UUID|-a|-b>"),
> N_("Mount a crypto device."), options);
> grub_procfs_register ("luks_script", &luks_script);
> }
> diff --git a/grub-core/disk/geli.c b/grub-core/disk/geli.c
> index 5b3a11881..0b8046746 100644
> --- a/grub-core/disk/geli.c
> +++ b/grub-core/disk/geli.c
> @@ -52,6 +52,7 @@
> #include <grub/dl.h>
> #include <grub/err.h>
> #include <grub/disk.h>
> +#include <grub/file.h>
> #include <grub/crypto.h>
> #include <grub/partition.h>
> #include <grub/i18n.h>
> @@ -121,6 +122,7 @@ enum
>
> /* FIXME: support version 0. */
> /* FIXME: support big-endian pre-version-4 volumes. */
> +/* FIXME: support for detached headers. */
> /* FIXME: support for keyfiles. */
> /* FIXME: support for HMAC. */
> const char *algorithms[] = {
> @@ -252,6 +254,10 @@ geli_scan (grub_disk_t disk, grub_cryptomount_args_t
> cargs)
> grub_disk_addr_t sector;
> grub_err_t err;
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return NULL;
> +
> if (2 * GRUB_MD_SHA256->mdlen + 1 > GRUB_CRYPTODISK_MAX_UUID_LENGTH)
> return NULL;
>
> @@ -412,6 +418,10 @@ geli_recover_key (grub_disk_t source, grub_cryptodisk_t
> dev, grub_cryptomount_ar
> if (cargs->key_data == NULL || cargs->key_len == 0)
> return grub_error (GRUB_ERR_BAD_ARGUMENT, "no key data");
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return GRUB_ERR_NOT_IMPLEMENTED_YET;
> +
> if (dev->cipher->cipher->blocksize > GRUB_CRYPTO_MAX_CIPHER_BLOCKSIZE)
> return grub_error (GRUB_ERR_BUG, "cipher block is too long");
>
> diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
> index d57257b3e..032a9db3c 100644
> --- a/grub-core/disk/luks.c
> +++ b/grub-core/disk/luks.c
> @@ -75,6 +75,10 @@ luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
> char hashspec[sizeof (header.hashSpec) + 1];
> grub_err_t err;
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return NULL;
> +
> if (cargs->check_boot)
> return NULL;
>
> @@ -164,6 +168,10 @@ luks_recover_key (grub_disk_t source,
> if (cargs->key_data == NULL || cargs->key_len == 0)
> return grub_error (GRUB_ERR_BAD_ARGUMENT, "no key data");
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return GRUB_ERR_NOT_IMPLEMENTED_YET;
> +
> err = grub_disk_read (source, 0, 0, sizeof (header), &header);
> if (err)
> return err;
> diff --git a/grub-core/disk/luks2.c b/grub-core/disk/luks2.c
> index ccfacb63a..567368f11 100644
> --- a/grub-core/disk/luks2.c
> +++ b/grub-core/disk/luks2.c
> @@ -353,6 +353,10 @@ luks2_scan (grub_disk_t disk, grub_cryptomount_args_t
> cargs)
> char uuid[sizeof (header.uuid) + 1];
> grub_size_t i, j;
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return NULL;
> +
> if (cargs->check_boot)
> return NULL;
>
> @@ -560,6 +564,10 @@ luks2_recover_key (grub_disk_t source,
> if (cargs->key_data == NULL || cargs->key_len == 0)
> return grub_error (GRUB_ERR_BAD_ARGUMENT, "no key data");
>
> + /* Detached headers are not implemented yet */
> + if (cargs->hdr_file)
> + return GRUB_ERR_NOT_IMPLEMENTED_YET;
> +
> ret = luks2_read_header (source, &header);
> if (ret)
> return ret;
> diff --git a/include/grub/cryptodisk.h b/include/grub/cryptodisk.h
> index c6524c9ea..9fe451de9 100644
> --- a/include/grub/cryptodisk.h
> +++ b/include/grub/cryptodisk.h
> @@ -20,6 +20,7 @@
> #define GRUB_CRYPTODISK_HEADER 1
>
> #include <grub/disk.h>
> +#include <grub/file.h>
> #include <grub/crypto.h>
> #include <grub/list.h>
> #ifdef GRUB_UTIL
> @@ -77,6 +78,7 @@ struct grub_cryptomount_args
> grub_uint8_t *key_data;
> /* recover_key: Length of key_data */
> grub_size_t key_len;
> + grub_file_t hdr_file;
You pass the external header in the file using grub_file_t.
Wouldn't it be better to use grub_disk_t for this? This will greatly
shorten the code.
You don't have to change the code of the luks2_read_header() and
luks2_scan() functions.
Plus it will give more flexibility to the user. Optionally, the user
can use a separate disk for the header, or open the file with "loopback
hdr_loop (...)/path/to/hdr"
> };
> typedef struct grub_cryptomount_args *grub_cryptomount_args_t;
>
> diff --git a/include/grub/file.h b/include/grub/file.h
> index 31567483c..3a3c49a04 100644
> --- a/include/grub/file.h
> +++ b/include/grub/file.h
> @@ -90,6 +90,8 @@ enum grub_file_type
> GRUB_FILE_TYPE_FONT,
> /* File holding encryption key for encrypted ZFS. */
> GRUB_FILE_TYPE_ZFS_ENCRYPTION_KEY,
> + /* File holding the encryption metadata header */
> + GRUB_FILE_TYPE_CRYPTODISK_DETACHED_HEADER,
> /* File we open n grub-fstest. */
> GRUB_FILE_TYPE_FSTEST,
> /* File we open n grub-mount. */
Dmitry
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