[PATCH v22 28/33] cryptodisk: Fallback to passphrase

[Gary Lin]

From: Patrick Colp <patrick.colp@oracle.com>

If a protector is specified, but it fails to unlock the disk, fall back
to asking for the passphrase.

Before requesting the passphrase, the error from the key protector(s)
has to be cleared, or the later code (e.g., LUKS code) may stop as
'grub_errno' is set. This commit prints error from the key protector(s)
and sets 'grub_errno' to 'GRUB_ERR_NONE' to have a fresh start.

Signed-off-by: Patrick Colp <patrick.colp@oracle.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/disk/cryptodisk.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index 6f7394942..4219f1fb6 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -1167,6 +1167,10 @@ grub_cryptodisk_scan_device_real (const char *name,
          ret = cr->recover_key (source, dev, cargs);
          if (ret != GRUB_ERR_NONE)
            {
+             /* Reset key data to trigger the passphrase prompt later */
+             cargs->key_data = NULL;
+             cargs->key_len = 0;
+
              part = grub_partition_get_name (source->partition);
              grub_dprintf ("cryptodisk",
                            "recovered a key from key protector %s but it "
@@ -1192,7 +1196,6 @@ grub_cryptodisk_scan_device_real (const char *name,
                  source->name, source->partition != NULL ? "," : "",
                  part != NULL ? part : N_("UNKNOWN"), dev->uuid);
       grub_free (part);
-      goto error;
     }
 
   if (cargs->key_len)
@@ -1207,6 +1210,24 @@ grub_cryptodisk_scan_device_real (const char *name,
       unsigned long tries = 3;
       const char *tries_env;
 
+      /*
+       * Print the error from key protectors and clear grub_errno.
+       *
+       * Since '--protector' cannot coexist with '--password' and
+       * '--key-file', in case key protectors fail, only
+       * "cargs->key_len == 0" is expected, so cryptomount falls back
+       * here to request the passphrase.
+       *
+       * To avoid the error from key protectors stops the further code,
+       * print the error to notify the user why key protectors fail and
+       * clear grub_errno to have a fresh start.
+       */
+      if (grub_errno != GRUB_ERR_NONE)
+       {
+         grub_print_error ();
+         grub_errno = GRUB_ERR_NONE;
+       }
+
       askpass = 1;
       cargs->key_data = grub_malloc (GRUB_CRYPTODISK_MAX_PASSPHRASE);
       if (cargs->key_data == NULL)
-- 
2.43.0