[PATCH 2/5] Cryptomount support key files

[John Lane <grub@jelmail.com>]

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

---
 grub-core/disk/cryptodisk.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-
 grub-core/disk/geli.c       |  4 +++-
 grub-core/disk/luks.c       | 44 +++++++++++++++++++++++++++++--------------
 include/grub/cryptodisk.h   |  5 ++++-
 4 files changed, 82 insertions(+), 17 deletions(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index 6f596a0..a27e70c 100644
--- a/grub-core/disk/cryptodisk.c
+++ b/grub-core/disk/cryptodisk.c
@@ -41,6 +41,9 @@ 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},
     {"header", 'H', 0, N_("Read LUKS header from file"), 0, ARG_TYPE_STRING},
+    {"keyfile", '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}
   };
 
@@ -805,6 +808,8 @@ grub_util_cryptodisk_get_uuid (grub_disk_t disk)
 static int check_boot, have_it;
 static char *search_uuid;
 static grub_file_t hdr;
+static grub_uint8_t *key, keyfile_buffer[GRUB_CRYPTODISK_MAX_KEYFILE_SIZE];
+static grub_size_t keyfile_size;
 
 static void
 cryptodisk_close (grub_cryptodisk_t dev)
@@ -835,7 +840,7 @@ grub_cryptodisk_scan_device_real (const char *name, grub_disk_t source)
     if (!dev)
       continue;
     
-    err = cr->recover_key (source, dev, hdr);
+    err = cr->recover_key (source, dev, hdr, key, keyfile_size);
     if (err)
     {
       cryptodisk_close (dev);
@@ -943,6 +948,45 @@ grub_cmd_cryptomount (grub_extcmd_context_t ctxt, int argc, char **args)
     hdr = NULL;
 
   have_it = 0;
+  key = NULL;
+
+  if (state[4].set) /* Key file; fails back to passphrase entry */
+    {
+      grub_file_t keyfile;
+      int keyfile_offset;
+      grub_size_t requested_keyfile_size;
+
+      requested_keyfile_size = state[6].set ? grub_strtoul(state[6].arg, 0, 0) : 0;
+
+      if (requested_keyfile_size > GRUB_CRYPTODISK_MAX_KEYFILE_SIZE)
+        grub_printf (N_("Key file size exceeds maximum (%llu)\n"), \
+	                     (unsigned long long) GRUB_CRYPTODISK_MAX_KEYFILE_SIZE);
+      else
+        {
+          keyfile_offset = state[5].set ? grub_strtoul (state[5].arg, 0, 0) : 0;
+          keyfile_size = requested_keyfile_size ? requested_keyfile_size : \
+		                             GRUB_CRYPTODISK_MAX_KEYFILE_SIZE;
+
+          keyfile = grub_file_open (state[4].arg);
+          if (!keyfile)
+            grub_printf (N_("Unable to open key file %s\n"), state[4].arg);
+          else if (grub_file_seek (keyfile, keyfile_offset) == (grub_off_t)-1)
+            grub_printf (N_("Unable to seek to offset %d in key file\n"), keyfile_offset);
+          else
+            {
+              keyfile_size = grub_file_read (keyfile, keyfile_buffer, keyfile_size);
+              if (keyfile_size == (grub_size_t)-1)
+                 grub_printf (N_("Error reading key file\n"));
+	      else if (requested_keyfile_size && (keyfile_size != requested_keyfile_size))
+                 grub_printf (N_("Cannot read %llu bytes for key file (read %llu bytes)\n"),
+                                                (unsigned long long) requested_keyfile_size,
+						(unsigned long long) keyfile_size);
+              else
+                key = keyfile_buffer;
+	    }
+        }
+    }
+
   if (state[0].set)
     {
       grub_cryptodisk_t dev;
diff --git a/grub-core/disk/geli.c b/grub-core/disk/geli.c
index f4394eb..da6aa6a 100644
--- a/grub-core/disk/geli.c
+++ b/grub-core/disk/geli.c
@@ -401,7 +401,9 @@ configure_ciphers (grub_disk_t disk, const char *check_uuid,
 
 static grub_err_t
 recover_key (grub_disk_t source, grub_cryptodisk_t dev,
-	     grub_file_t hdr __attribute__ ((unused)) )
+	     grub_file_t hdr __attribute__ ((unused)),
+	     grub_uint8_t *key __attribute__ ((unused)),
+	     grub_size_t keyfile_size __attribute__ ((unused)) )
 {
   grub_size_t keysize;
   grub_uint8_t digest[GRUB_CRYPTO_MAX_MDLEN];
diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
index 66e64c0..5882368 100644
--- a/grub-core/disk/luks.c
+++ b/grub-core/disk/luks.c
@@ -322,12 +322,16 @@ configure_ciphers (grub_disk_t disk, const char *check_uuid,
 static grub_err_t
 luks_recover_key (grub_disk_t source,
 		  grub_cryptodisk_t dev,
-	          grub_file_t hdr)
+		  grub_file_t hdr,
+		  grub_uint8_t *keyfile_bytes,
+		  grub_size_t keyfile_bytes_size)
 {
   struct grub_luks_phdr header;
   grub_size_t keysize;
   grub_uint8_t *split_key = NULL;
-  char passphrase[MAX_PASSPHRASE] = "";
+  char interactive_passphrase[MAX_PASSPHRASE] = "";
+  grub_uint8_t *passphrase;
+  grub_size_t passphrase_length;
   grub_uint8_t candidate_digest[sizeof (header.mkDigest)];
   unsigned i;
   grub_size_t length;
@@ -364,18 +368,30 @@ luks_recover_key (grub_disk_t source,
   if (!split_key)
     return grub_errno;
 
-  /* Get the passphrase from the user.  */
-  tmp = NULL;
-  if (source->partition)
-    tmp = grub_partition_get_name (source->partition);
-  grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
-	       source->partition ? "," : "", tmp ? : "",
-	       dev->uuid);
-  grub_free (tmp);
-  if (!grub_password_get (passphrase, MAX_PASSPHRASE))
+  if (keyfile_bytes)
     {
-      grub_free (split_key);
-      return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not supplied");
+      /* Use bytestring from key file as passphrase */
+      passphrase = keyfile_bytes;
+      passphrase_length = keyfile_bytes_size;
+    }
+  else
+    {
+      /* Get the passphrase from the user.  */
+      tmp = NULL;
+      if (source->partition)
+        tmp = grub_partition_get_name (source->partition);
+      grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
+		    source->partition ? "," : "", tmp ? : "", dev->uuid);
+      grub_free (tmp);
+      if (!grub_password_get (interactive_passphrase, MAX_PASSPHRASE))
+        {
+          grub_free (split_key);
+          return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not supplied");
+        }
+
+      passphrase = (grub_uint8_t *)interactive_passphrase;
+      passphrase_length = grub_strlen (interactive_passphrase);
+
     }
 
   /* Try to recover master key from each active keyslot.  */
@@ -393,7 +409,7 @@ luks_recover_key (grub_disk_t source,
 
       /* Calculate the PBKDF2 of the user supplied passphrase.  */
       gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
-				     grub_strlen (passphrase),
+				     passphrase_length,
 				     header.keyblock[i].passwordSalt,
 				     sizeof (header.keyblock[i].passwordSalt),
 				     grub_be_to_cpu32 (header.keyblock[i].
diff --git a/include/grub/cryptodisk.h b/include/grub/cryptodisk.h
index 16dee3c..0299625 100644
--- a/include/grub/cryptodisk.h
+++ b/include/grub/cryptodisk.h
@@ -55,6 +55,8 @@ typedef enum
 #define GRUB_CRYPTODISK_GF_BYTES (1U << GRUB_CRYPTODISK_GF_LOG_BYTES)
 #define GRUB_CRYPTODISK_MAX_KEYLEN 128
 
+#define GRUB_CRYPTODISK_MAX_KEYFILE_SIZE 8192
+
 struct grub_cryptodisk;
 
 typedef gcry_err_code_t
@@ -108,7 +110,8 @@ struct grub_cryptodisk_dev
 
   grub_cryptodisk_t (*scan) (grub_disk_t disk, const char *check_uuid,
 			     int boot_only, grub_file_t hdr);
-  grub_err_t (*recover_key) (grub_disk_t disk, grub_cryptodisk_t dev, grub_file_t hdr);
+  grub_err_t (*recover_key) (grub_disk_t disk, grub_cryptodisk_t dev,
+			    grub_file_t hdr, grub_uint8_t *key, grub_size_t keyfile_size);
 };
 typedef struct grub_cryptodisk_dev *grub_cryptodisk_dev_t;
 
-- 
2.1.2