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Re: [PATCH 1/3] cryptodisk: Add infrastructure to pass data from cryptom
From: |
Patrick Steinhardt |
Subject: |
Re: [PATCH 1/3] cryptodisk: Add infrastructure to pass data from cryptomount to cryptodisk modules |
Date: |
Mon, 30 Aug 2021 19:55:59 +0200 |
On Thu, Aug 26, 2021 at 12:08:50AM -0500, Glenn Washburn wrote:
> As an example, passing a password as a cryptomount argument is implemented.
> However, the backends are not implemented, so testing this will return a not
> implemented error.
>
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
> grub-core/disk/cryptodisk.c | 31 ++++++++++++++++++++++---------
> grub-core/disk/geli.c | 4 ++++
> grub-core/disk/luks.c | 4 ++++
> grub-core/disk/luks2.c | 4 ++++
> include/grub/cryptodisk.h | 8 ++++++++
> 5 files changed, 42 insertions(+), 9 deletions(-)
>
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index 90f82b2d3..b966b19ab 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -41,6 +41,7 @@ static const struct grub_arg_option options[] =
> /* TRANSLATORS: It's still restricted to cryptodisks only. */
> {"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},
> {0, 0, 0, 0, 0, 0}
> };
>
> @@ -996,7 +997,9 @@ cryptodisk_close (grub_cryptodisk_t dev)
> }
>
> static grub_err_t
> -grub_cryptodisk_scan_device_real (const char *name, grub_disk_t source)
> +grub_cryptodisk_scan_device_real (const char *name,
> + grub_disk_t source,
> + grub_cryptomount_args_t cargs)
> {
> grub_err_t err;
> grub_cryptodisk_t dev;
> @@ -1015,7 +1018,9 @@ grub_cryptodisk_scan_device_real (const char *name,
> grub_disk_t source)
> if (!dev)
> continue;
>
> + *dev->cargs = *cargs;
> err = cr->recover_key (source, dev);
> + *dev->cargs = NULL;
> if (err)
> {
> cryptodisk_close (dev);
Is there any specific reason why you choose to set `cargs` as a struct
field? Seeing uses like this makes me wonder whether it wouldn't be
better to pass in `cargs` as explicit arguments whenever required. This
would also automatically answer any lifetime questions which arise.
[snip]
> diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
> index 13103ea6a..e2a4a3bf5 100644
> --- a/grub-core/disk/luks.c
> +++ b/grub-core/disk/luks.c
> @@ -165,6 +165,10 @@ luks_recover_key (grub_disk_t source,
> grub_size_t max_stripes = 1;
> char *tmp;
>
> + /* Keyfiles are not implemented yet */
> + if (dev->cargs->key_data || dev->cargs->key_len)
> + return GRUB_ERR_NOT_IMPLEMENTED_YET;
> +
> err = grub_disk_read (source, 0, 0, sizeof (header), &header);
> if (err)
> return err;
Hum. This makes me wonder whether we'll have to adjust all backends
whenever we add a new parameter to `cargs` to return `NOT_IMPLEMENTED`.
I fear that it won't scale nicely, and that it is a recipe for passing
unsupported arguments to backends even though they don't know to handle
them.
Not sure about a nice alternative though. The only idea I have right now
is something like a capabilities bitfield exposed by backends: only if a
specific bit is set will we pass the corresponding field to such a
backend. This would allow us to easily centralize the logic into a
single function which only receives both the capabilities bitset and the
`cargs` struct.
Other than that I really like where this is going.
Patrick
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