On Fri, 13 Nov 2020 14:25:08 -0800
James Bottomley <j...@linux.ibm.com> wrote:
> For AMD SEV environments, the grub boot password has to be retrieved
> from a given memory location rather than prompted for. This means
> that the standard password getter needs to be replaced with one that
> gets the passphrase from the SEV area and uses that instead. Adding
> the password getter as a passed in argument to recover_key() makes
> this possible.
>
> Signed-off-by: James Bottomley <j...@linux.ibm.com>
>
> ---
>
> v2: add conditional prompting to geli.c
> ---
> grub-core/disk/cryptodisk.c | 2 +-
> grub-core/disk/geli.c | 12 +++++++-----
> grub-core/disk/luks.c | 12 +++++++-----
> grub-core/disk/luks2.c | 12 +++++++-----
> include/grub/cryptodisk.h | 6 +++++-
> 5 files changed, 27 insertions(+), 17 deletions(-)
>
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index a3d672f68..682f5a55d 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -997,7 +997,7 @@ grub_cryptodisk_scan_device_real (const char
> *name, grub_disk_t source) if (!dev)
> continue;
>
> - err = cr->recover_key (source, dev);
> + err = cr->recover_key (source, dev, grub_password_get);
> if (err)
> {
> cryptodisk_close (dev);
> diff --git a/grub-core/disk/geli.c b/grub-core/disk/geli.c
> index e9d23299a..3fece3f4a 100644
> --- a/grub-core/disk/geli.c
> +++ b/grub-core/disk/geli.c
> @@ -398,7 +398,8 @@ configure_ciphers (grub_disk_t disk, const char
> *check_uuid, }
>
> static grub_err_t
> -recover_key (grub_disk_t source, grub_cryptodisk_t dev)
> +recover_key (grub_disk_t source, grub_cryptodisk_t dev,
> + grub_passwd_cb *password_get)
> {
> grub_size_t keysize;
> grub_uint8_t digest[GRUB_CRYPTO_MAX_MDLEN];
> @@ -438,11 +439,12 @@ recover_key (grub_disk_t source,
> grub_cryptodisk_t dev) tmp = NULL;
> if (source->partition)
> tmp = grub_partition_get_name (source->partition);
> - grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "),
> source->name,
> - source->partition ? "," : "", tmp ? : "",
> - dev->uuid);
> + if (password_get == grub_password_get)
> + grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "),
> source->name,
> + source->partition ? "," : "", tmp ? : "",
> + dev->uuid);
> grub_free (tmp);
> - if (!grub_password_get (passphrase, MAX_PASSPHRASE))
> + if (!password_get (passphrase, MAX_PASSPHRASE))
> return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not
> supplied");
> /* Calculate the PBKDF2 of the user supplied passphrase. */
> diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
> index 59702067a..165f4a6bd 100644
> --- a/grub-core/disk/luks.c
> +++ b/grub-core/disk/luks.c
> @@ -152,7 +152,8 @@ configure_ciphers (grub_disk_t disk, const char
> *check_uuid,
> static grub_err_t
> luks_recover_key (grub_disk_t source,
> - grub_cryptodisk_t dev)
> + grub_cryptodisk_t dev,
> + grub_passwd_cb *password_get)
> {
> struct grub_luks_phdr header;
> grub_size_t keysize;
> @@ -187,11 +188,12 @@ luks_recover_key (grub_disk_t source,
> tmp = NULL;
> if (source->partition)
> tmp = grub_partition_get_name (source->partition);
> - grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "),
> source->name,
> - source->partition ? "," : "", tmp ? : "",
> - dev->uuid);
> + if (password_get == grub_password_get)
> + grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "),
> source->name,
> + source->partition ? "," : "", tmp ? : "",
> + dev->uuid);
I don't really like this added if statement. It feels hackish. I also
don't have an unambiguously better alternative.
What feels like an imperfect alternative is to define a function
grub_password_prompt(char buf[], unsigned buf_size, const char
*prompt), which calls grub_password_get after displaying the string
prompt. Typedef grub_passwd_cb to grub_password_prompt's signature.
Then some grub_passwd_cb implementations can decide when not to use the
given prompt. Perhaps grub_password_prompt should have snprintf's
signature to be more complete and combine the grub_printf_ and
grub_password_get.
Any other ideas?
Glenn
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