[PATCH 3/4] cryptodisk: Add options to cryptomount to support keyfiles

[Glenn Washburn]

From: John Lane <john@lane.uk.net>

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 (eg. LUKS1)
because the key data is passed just as if it were a password.

Signed-off-by: John Lane <john@lane.uk.net>
GNUtoo@cyberdimension.org: rebase, patch split, small fixes, commit message
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
development@efficientek.com: rebase and rework to use cryptomount arg passing,
  minor fixes, improve commit message
Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 grub-core/disk/cryptodisk.c | 86 ++++++++++++++++++++++++++++++++++++-
 include/grub/cryptodisk.h   |  2 +
 include/grub/file.h         |  2 +
 3 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index 9f5dc7acb..19af4fa49 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/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 +1175,85 @@ 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 */
+       {
+         keyfile_offset = grub_strtoull (state[5].arg, &p, 0);
+
+         if (grub_errno != GRUB_ERR_NONE)
+           return grub_errno;
+
+         if (state[5].arg[0] == '\0' || *p != '\0')
+           return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                              N_("non-numeric or invalid keyfile offset `%s'"),
+                              state[5].arg);
+       }
+
+      if (state[6].set) /* keyfile-size */
+       {
+         keyfile_size = grub_strtoul (state[6].arg, &p, 0);
+
+         if (state[6].arg[0] == '\0' || *p != '\0')
+           return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                              N_("non-numeric or invalid keyfile size `%s'"),
+                              state[6].arg);
+
+         if (grub_errno != GRUB_ERR_NONE)
+           return grub_errno;
+
+         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);
+
+         if (keyfile_size == 0)
+           return grub_error (GRUB_ERR_OUT_OF_RANGE, N_("key file size is 0"));
+       }
+
+      keyfile = grub_file_open (state[4].arg,
+                               GRUB_FILE_TYPE_CRYPTODISK_ENCRYPTION_KEY);
+      if (keyfile == NULL)
+       return grub_errno;
+
+      if (keyfile_offset > keyfile->size)
+       {
+         keyfile_offset = keyfile->size;
+         grub_dprintf ("cryptodisk","Keyfile offset, %llu, is greater than"
+                                    "keyfile size, %" PRIuGRUB_UINT64_T "\n",
+                                    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"),
+                              keyfile_size,
+                              keyfile->size);
+
+         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_("reading key file")));
+    }
+
   if (state[0].set) /* uuid */
     {
       int found_uuid;
@@ -1384,7 +1466,9 @@ 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);
 }
diff --git a/include/grub/cryptodisk.h b/include/grub/cryptodisk.h
index c6524c9ea..467065f00 100644
--- a/include/grub/cryptodisk.h
+++ b/include/grub/cryptodisk.h
@@ -61,6 +61,8 @@ typedef enum
 #define GRUB_CRYPTODISK_MAX_KEYLEN 128
 #define GRUB_CRYPTODISK_MAX_PASSPHRASE 256
 
+#define GRUB_CRYPTODISK_MAX_KEYFILE_SIZE 8192
+
 struct grub_cryptodisk;
 
 typedef gcry_err_code_t
diff --git a/include/grub/file.h b/include/grub/file.h
index 31567483c..d53ee8edd 100644
--- a/include/grub/file.h
+++ b/include/grub/file.h
@@ -90,6 +90,8 @@ enum grub_file_type
     GRUB_FILE_TYPE_FONT,
     /* File holding encryption key for encrypted ZFS.  */
     GRUB_FILE_TYPE_ZFS_ENCRYPTION_KEY,
+    /* File holding the encryption key */
+    GRUB_FILE_TYPE_CRYPTODISK_ENCRYPTION_KEY,
     /* File we open n grub-fstest.  */
     GRUB_FILE_TYPE_FSTEST,
     /* File we open n grub-mount.  */
-- 
2.34.1