[PATCH 2/2] devmapper/getroot: Set up cheated LUKS2 cryptodisk mount from DM parameters

[Josselin Poiret]

This lets a LUKS2 cryptodisk have all the cipher, hash, and sizes
filled out, otherwise they wouldn't be initialized if cheat mounted.
---
 grub-core/osdep/devmapper/getroot.c | 51 ++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/grub-core/osdep/devmapper/getroot.c 
b/grub-core/osdep/devmapper/getroot.c
index ad1daf9c8..574d07a20 100644
--- a/grub-core/osdep/devmapper/getroot.c
+++ b/grub-core/osdep/devmapper/getroot.c
@@ -51,6 +51,8 @@
 #include <grub/emu/misc.h>
 #include <grub/emu/hostdisk.h>
 
+#include <grub/cryptodisk.h>
+
 static int
 grub_util_open_dm (const char *os_dev, struct dm_tree **tree,
                   struct dm_tree_node **node)
@@ -183,7 +185,6 @@ grub_util_pull_devmapper (const char *os_dev)
       && lastsubdev)
     {
       char *grdev = grub_util_get_grub_dev (lastsubdev);
-      dm_tree_free (tree);
       if (grdev)
        {
          grub_err_t err;
@@ -191,7 +192,55 @@ grub_util_pull_devmapper (const char *os_dev)
          if (err)
            grub_util_error (_("can't mount encrypted volume `%s': %s"),
                             lastsubdev, grub_errmsg);
+          if (strncmp (uuid, "CRYPT-LUKS2-", sizeof ("CRYPT-LUKS2-") - 1) == 0)
+            {
+              /* set LUKS2 cipher and size from dm parameter, since it is not
+                 possible to determine the correct ones without unlocking, as
+                 there might be multiple segments. */
+              grub_disk_t source = grub_disk_open (grdev);
+              grub_cryptodisk_t cryptodisk = 
grub_cryptodisk_get_by_source_disk (source);
+              grub_disk_close (source);
+              grub_addr_t start, length;
+              char *target_type = NULL;
+              char *params;
+              const char *name = dm_tree_node_get_name (node);
+              char *cipher, *cipher_mode;
+              struct dm_task *dmt;
+              grub_util_info ("creating dm task for `%s'", name);
+              if (!(dmt = dm_task_create (DM_DEVICE_TABLE)))
+                grub_util_error (_("can't create dm task DM_DEVICE_TABLE"));
+              if (!dm_task_set_name (dmt, name))
+                grub_util_error (_("can't set dm task name to `%s'"), name);
+              if (!dm_task_run (dmt))
+                grub_util_error (_("can't run dm task for `%s'"), name);
+              dm_get_next_target (dmt, NULL, &start, &length,
+                                  &target_type, &params);
+              if (strncmp (target_type, "crypt", sizeof ("crypt")) != 0)
+                grub_util_error (_("dm target is not `crypt'"));
+
+              cryptodisk->total_sectors = length;
+              cryptodisk->log_sector_size = GRUB_LUKS1_LOG_SECTOR_SIZE;
+
+              char *seek_head, *c;
+              c = params;
+              if (!(seek_head = grub_memchr (c, '-', grub_strlen (c))))
+                grub_util_error (_("can't get cipher from dm task"));
+              cipher = grub_strndup (c, seek_head - c);
+
+              c = seek_head + 1;
+              if (!(seek_head = grub_memchr (c, ' ', grub_strlen (c))))
+                grub_util_error (_("can't get cipher mode from dm task"));
+              cipher_mode = grub_strndup (c, seek_head - c);
+
+              grub_cryptodisk_setcipher (cryptodisk, cipher, cipher_mode);
+
+              /* This is the only hash usable by PBKDF2, so set it as such */
+              cryptodisk->hash = grub_crypto_lookup_md_by_name ("sha256");
+
+              dm_task_destroy (dmt);
+            }
        }
+      dm_tree_free (tree);
       grub_free (grdev);
     }
   else
-- 
2.34.0