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disk/cryptodisk: Allow user to retry failed passphrase

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Give the user a chance to re-enter their cryptodisk passphrase after a typo,
rather than immediately failing (and likely dumping them into a GRUB shell).

By default, we allow 3 tries before giving up. A value in the
cryptodisk_passphrase_tries environment variable will override this default.

The user can give up early by entering an empty passphrase, just as they
could before this patch.

Signed-off-by: Forest <forestix@nom.one>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Forest 2024-05-06 17:07:30 -07:00 committed by Daniel Kiper
parent 99b4c0c384
commit 386b59ddb4
2 changed files with 65 additions and 17 deletions
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9
docs/grub.texi
View File

@ -3277,6 +3277,7 @@ These variables have special meaning to GRUB.
* color_normal::
* config_directory::
* config_file::
* cryptodisk_passphrase_tries::
* debug::
* default::
* fallback::
@ -3441,6 +3442,14 @@ processed by commands @command{configfile} (@pxref{configfile}) or @command{norm
(@pxref{normal}). It is restored to the previous value when command completes.
@node cryptodisk_passphrase_tries
@subsection cryptodisk_passphrase_tries
When prompting the user for a cryptodisk passphrase, allow this many attempts
before giving up. Defaults to @samp{3} if unset or set to an invalid value.
(The user can give up early by entering an empty passphrase.)
@node debug
@subsection debug

73
grub-core/disk/cryptodisk.c
View File

@ -17,6 +17,7 @@
*/
#include <grub/cryptodisk.h>
#include <grub/env.h>
#include <grub/mm.h>
#include <grub/misc.h>
#include <grub/dl.h>
@ -1114,32 +1115,70 @@ grub_cryptodisk_scan_device_real (const char *name,
if (!dev)
continue;
if (!cargs->key_len)
if (cargs->key_len)
{
ret = cr->recover_key (source, dev, cargs);
if (ret != GRUB_ERR_NONE)
goto error;
}
else
{
/* Get the passphrase from the user, if no key data. */
askpass = 1;
part = grub_partition_get_name (source->partition);
grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
source->partition != NULL ? "," : "",
part != NULL ? part : N_("UNKNOWN"),
dev->uuid);
grub_free (part);
unsigned long tries = 3;
const char *tries_env;
askpass = 1;
cargs->key_data = grub_malloc (GRUB_CRYPTODISK_MAX_PASSPHRASE);
if (cargs->key_data == NULL)
goto error_no_close;
if (!grub_password_get ((char *) cargs->key_data, GRUB_CRYPTODISK_MAX_PASSPHRASE))
tries_env = grub_env_get ("cryptodisk_passphrase_tries");
if (tries_env != NULL && tries_env[0] != '\0')
{
grub_error (GRUB_ERR_BAD_ARGUMENT, "passphrase not supplied");
goto error;
}
cargs->key_len = grub_strlen ((char *) cargs->key_data);
}
unsigned long tries_env_val;
const char *p;
ret = cr->recover_key (source, dev, cargs);
if (ret != GRUB_ERR_NONE)
goto error;
tries_env_val = grub_strtoul (tries_env, &p, 0);
if (*p == '\0' && tries_env_val != ~0UL)
tries = tries_env_val;
else
grub_printf_ (N_("Invalid cryptodisk_passphrase_tries value `%s'. Defaulting to %lu.\n"),
tries_env,
tries);
}
for (; tries > 0; tries--)
{
part = grub_partition_get_name (source->partition);
grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
source->partition != NULL ? "," : "",
part != NULL ? part : N_("UNKNOWN"),
dev->uuid);
grub_free (part);
if (!grub_password_get ((char *) cargs->key_data, GRUB_CRYPTODISK_MAX_PASSPHRASE))
{
grub_error (GRUB_ERR_BAD_ARGUMENT, "passphrase not supplied");
goto error;
}
cargs->key_len = grub_strlen ((char *) cargs->key_data);
ret = cr->recover_key (source, dev, cargs);
if (ret == GRUB_ERR_NONE)
break;
if (ret != GRUB_ERR_ACCESS_DENIED || tries == 1)
goto error;
grub_puts_ (N_("Invalid passphrase."));
/*
* Since recover_key() calls a function that returns grub_errno,
* a leftover error value from a previously rejected passphrase
* will trigger a phantom failure. We therefore clear it before
* trying a new passphrase.
*/
grub_errno = GRUB_ERR_NONE;
}
}
ret = grub_cryptodisk_insert (dev, name, source);
if (ret != GRUB_ERR_NONE)