[PATCH v9 4/7] cryptodisk: Add support for LUKS1 detached headers

[Glenn Washburn]

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

cryptsetup supports having a detached header through the --header command
line argument for both LUKS1 and LUKS2. Allow the LUKS1 backend to use a
given file as the LUKS1 header (aka detached header) instead of looking for
the header on the disk.

Signed-off-by: John Lane <john@lane.uk.net>
GNUtoo@cyberdimension.org: rebase, small fixes, commit message
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
development@efficientek.com: rebase, improve commit message
Signed-off-by: Glenn Washburn <development@efficientek.com>
---
 grub-core/disk/luks.c | 48 ++++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 14 deletions(-)

diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
index fe1655c3c2..195c4bb8da 100644
--- a/grub-core/disk/luks.c
+++ b/grub-core/disk/luks.c
@@ -23,6 +23,7 @@
 #include <grub/dl.h>
 #include <grub/err.h>
 #include <grub/disk.h>
+#include <grub/file.h>
 #include <grub/crypto.h>
 #include <grub/partition.h>
 #include <grub/i18n.h>
@@ -73,17 +74,23 @@ luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
   char ciphername[sizeof (header.cipherName) + 1];
   char ciphermode[sizeof (header.cipherMode) + 1];
   char hashspec[sizeof (header.hashSpec) + 1];
-  grub_err_t err;
-
-  /* Detached headers are not implemented yet */
-  if (cargs->hdr_file)
-    return NULL;
+  grub_err_t err = GRUB_ERR_NONE;
 
   if (cargs->check_boot)
     return NULL;
 
   /* Read the LUKS header.  */
-  err = grub_disk_read (disk, 0, 0, sizeof (header), &header);
+  if (cargs->hdr_file)
+    {
+      if (grub_file_seek (cargs->hdr_file, 0) == (grub_off_t) -1)
+       return NULL;
+
+      if (grub_file_read (cargs->hdr_file, &header, sizeof (header)) != sizeof 
(header))
+       return NULL;
+    }
+  else
+    err = grub_disk_read (disk, 0, 0, sizeof (header), &header);
+
   if (err)
     {
       if (err == GRUB_ERR_OUT_OF_RANGE)
@@ -162,17 +169,24 @@ luks_recover_key (grub_disk_t source,
   grub_uint8_t candidate_digest[sizeof (header.mkDigest)];
   unsigned i;
   grub_size_t length;
-  grub_err_t err;
+  grub_err_t err = GRUB_ERR_NONE;
   grub_size_t max_stripes = 1;
+  grub_uint32_t sector;
 
   if (cargs->key_data == NULL || cargs->key_len == 0)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, "no key data");
 
-  /* Detached headers are not implemented yet */
   if (cargs->hdr_file)
-     return GRUB_ERR_NOT_IMPLEMENTED_YET;
+    {
+      if (grub_file_seek (cargs->hdr_file, 0) == (grub_off_t) -1)
+       return grub_errno;
+
+      if (grub_file_read (cargs->hdr_file, &header, sizeof (header)) != sizeof 
(header))
+       return grub_errno;
+    }
+  else
+    err = grub_disk_read (source, 0, 0, sizeof (header), &header);
 
-  err = grub_disk_read (source, 0, 0, sizeof (header), &header);
   if (err)
     return err;
 
@@ -227,13 +241,19 @@ luks_recover_key (grub_disk_t source,
          return grub_crypto_gcry_error (gcry_err);
        }
 
+      sector = grub_be_to_cpu32 (header.keyblock[i].keyMaterialOffset);
       length = (keysize * grub_be_to_cpu32 (header.keyblock[i].stripes));
 
       /* Read and decrypt the key material from the disk.  */
-      err = grub_disk_read (source,
-                           grub_be_to_cpu32 (header.keyblock
-                                             [i].keyMaterialOffset), 0,
-                           length, split_key);
+      if (cargs->hdr_file)
+      {
+        if (grub_file_seek (cargs->hdr_file, sector * 512) == (grub_off_t) -1)
+          return grub_errno;
+        if (grub_file_read (cargs->hdr_file, split_key, length) != 
(grub_ssize_t)length)
+          return grub_errno;
+      }
+      else
+        err = grub_disk_read (source, sector, 0, length, split_key);
       if (err)
        {
          grub_free (split_key);
-- 
2.25.1