On Sat, 27 Apr 2024 17:48:31 -0700
Forest <fores...@nom.one> wrote:
> 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 <fores...@nom.one>
> ---
> Note: This is identical to the v3 patch. The change I had in mind proved
> unviable.
LGTM.
Reviewed-by: Glenn Washburn <developm...@efficientek.com>
Glenn
>
> docs/grub.texi | 9 +++++
> grub-core/disk/cryptodisk.c | 74 +++++++++++++++++++++++++++++--------
> 2 files changed, 67 insertions(+), 16 deletions(-)
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index a225f9a88..6ac603a32 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -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. The default is @samp{3}. (The user can give up early by
> +entering an empty passphrase.)
> +
> +
> @node debug
> @subsection debug
>
> diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
> index 2246af51b..4fa7dc58d 100644
> --- a/grub-core/disk/cryptodisk.c
> +++ b/grub-core/disk/cryptodisk.c
> @@ -17,6 +17,7 @@
> */
>
> #include <grub/cryptodisk.h>
> +#include <grub/env.h>
> #include <grub/mm.h>
> #include <grub/misc.h>
> #include <grub/dl.h>
> @@ -1063,6 +1064,8 @@ grub_cryptodisk_scan_device_real (const char *name,
> grub_cryptodisk_dev_t cr;
> struct cryptodisk_read_hook_ctx read_hook_data = {0};
> int askpass = 0;
> + unsigned long tries = 3;
> + const char *tries_env;
> char *part = NULL;
>
> dev = grub_cryptodisk_get_by_source_disk (source);
> @@ -1114,32 +1117,71 @@ 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);
> -
> 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;
> + const char *p = NULL;
> + tries = grub_strtoul (tries_env, &p, 0);
> + if (*p != '\0')
> + {
> + /* Account for grub_strtoul() ignoring trailing text. */
> + grub_err_t err = grub_errno;
> + if (p > tries_env && tries != ~0UL)
> + err = GRUB_ERR_BAD_NUMBER;
> +
> + grub_error (err,
> + N_("non-numeric or invalid value for
> cryptodisk_passphrase_tries: `%s'"),
> + tries_env);
> + goto error;
> + }
> }
> - cargs->key_len = grub_strlen ((char *) cargs->key_data);
> - }
>
> - ret = cr->recover_key (source, dev, cargs);
> - if (ret != GRUB_ERR_NONE)
> - goto error;
> + 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)
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