disk/cryptodisk: Add options to cryptomount to support keyfiles

Add the options --key-file, --keyfile-offset, and --keyfile-size to
cryptomount and code to put read the requested key file data and pass
via the cargs struct. Note, key file data is for all intents and purposes
equivalent to a password given to cryptomount. So there is no need to
enable support for key files in the various crypto backends (e.g. LUKS1)
because the key data is passed just as if it were a password.

Signed-off-by: John Lane <john@lane.uk.net>
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/disk/cryptodisk.c

@@ -42,6 +42,9 @@ static const struct grub_arg_option options[] =
     {"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},
+    {"key-file", 'k', 0, N_("Key file"), 0, ARG_TYPE_STRING},
+    {"keyfile-offset", 'O', 0, N_("Key file offset (bytes)"), 0, ARG_TYPE_INT},
+    {"keyfile-size", 'S', 0, N_("Key file data size (bytes)"), 0, ARG_TYPE_INT},
     {0, 0, 0, 0, 0, 0}
   };
 
@@ -1172,6 +1175,80 @@ grub_cmd_cryptomount (grub_extcmd_context_t ctxt, int argc, char **args)
       cargs.key_len = grub_strlen (state[3].arg);
     }
 
+  if (state[4].set) /* keyfile */
+    {
+      const char *p = NULL;
+      grub_file_t keyfile;
+      unsigned long long keyfile_offset = 0, keyfile_size = 0;
+
+      if (state[5].set) /* keyfile-offset */
+	{
+	  grub_errno = GRUB_ERR_NONE;
+	  keyfile_offset = grub_strtoull (state[5].arg, &p, 0);
+
+	  if (state[5].arg[0] == '\0' || *p != '\0')
+	    return grub_error (grub_errno,
+			       N_("non-numeric or invalid keyfile offset `%s'"),
+			       state[5].arg);
+	}
+
+      if (state[6].set) /* keyfile-size */
+	{
+	  grub_errno = GRUB_ERR_NONE;
+	  keyfile_size = grub_strtoull (state[6].arg, &p, 0);
+
+	  if (state[6].arg[0] == '\0' || *p != '\0')
+	    return grub_error (grub_errno,
+			       N_("non-numeric or invalid keyfile size `%s'"),
+			       state[6].arg);
+
+	  if (keyfile_size == 0)
+	    return grub_error (GRUB_ERR_OUT_OF_RANGE, N_("key file size is 0"));
+
+	  if (keyfile_size > GRUB_CRYPTODISK_MAX_KEYFILE_SIZE)
+	    return grub_error (GRUB_ERR_OUT_OF_RANGE,
+			       N_("key file size exceeds maximum (%d)"),
+			       GRUB_CRYPTODISK_MAX_KEYFILE_SIZE);
+	}
+
+      keyfile = grub_file_open (state[4].arg,
+				GRUB_FILE_TYPE_CRYPTODISK_ENCRYPTION_KEY);
+      if (keyfile == NULL)
+	return grub_errno;
+
+      if (keyfile_offset > keyfile->size)
+	return grub_error (GRUB_ERR_OUT_OF_RANGE,
+			   N_("Keyfile offset, %llu, is greater than"
+			      "keyfile size, %" PRIuGRUB_UINT64_T),
+			   keyfile_offset, keyfile->size);
+
+      if (grub_file_seek (keyfile, (grub_off_t) keyfile_offset) == (grub_off_t) -1)
+	return grub_errno;
+
+      if (keyfile_size != 0)
+	{
+	  if (keyfile_size > (keyfile->size - keyfile_offset))
+	    return grub_error (GRUB_ERR_FILE_READ_ERROR,
+			       N_("keyfile is too small: requested %llu bytes,"
+				  " but the file only has %" PRIuGRUB_UINT64_T
+				  " bytes left at offset %llu"),
+			       keyfile_size,
+			       (grub_off_t) (keyfile->size - keyfile_offset),
+			       keyfile_offset);
+
+	  cargs.key_len = keyfile_size;
+	}
+      else
+	cargs.key_len = keyfile->size - keyfile_offset;
+
+      cargs.key_data = grub_malloc (cargs.key_len);
+      if (cargs.key_data == NULL)
+	return GRUB_ERR_OUT_OF_MEMORY;
+
+      if (grub_file_read (keyfile, cargs.key_data, cargs.key_len) != (grub_ssize_t) cargs.key_len)
+	return grub_error (GRUB_ERR_FILE_READ_ERROR, (N_("failed to read key file")));
+    }
+
   if (state[0].set) /* uuid */
     {
       int found_uuid;
@@ -1384,7 +1461,9 @@ GRUB_MOD_INIT (cryptodisk)
 {
   grub_disk_dev_register (&grub_cryptodisk_dev);
   cmd = grub_register_extcmd ("cryptomount", grub_cmd_cryptomount, 0,
-			      N_("[-p password] <SOURCE|-u UUID|-a|-b>"),
+			      N_("[ [-p password] | [-k keyfile"
+				 " [-O keyoffset] [-S keysize] ] ]"
+				 " <SOURCE|-u UUID|-a|-b>"),
 			      N_("Mount a crypto device."), options);
   grub_procfs_register ("luks_script", &luks_script);
 }