From f39e8ee5696f15860c73b07e652a8b59fcc834c7 Mon Sep 17 00:00:00 2001
From: John Lane <john@lane.uk.net>
Date: Fri, 26 Jun 2015 13:49:58 +0100
Subject: [PATCH 04/10] Cryptomount luks allow multiple passphrase attempts

---
 grub-core/disk/luks.c | 278 ++++++++++++++++++++++++++------------------------
 1 file changed, 143 insertions(+), 135 deletions(-)

diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
index 5882368..11e437e 100644
--- a/grub-core/disk/luks.c
+++ b/grub-core/disk/luks.c
@@ -321,10 +321,10 @@ 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_uint8_t *keyfile_bytes,
-		  grub_size_t keyfile_bytes_size)
+                  grub_cryptodisk_t dev,
+                  grub_file_t hdr,
+                  grub_uint8_t *keyfile_bytes,
+                  grub_size_t keyfile_bytes_size)
 {
   struct grub_luks_phdr header;
   grub_size_t keysize;
@@ -339,6 +339,7 @@ luks_recover_key (grub_disk_t source,
   grub_size_t max_stripes = 1;
   char *tmp;
   grub_uint32_t sector;
+  unsigned attempts = 2;
 
   err = GRUB_ERR_NONE;
 
@@ -361,151 +362,158 @@ luks_recover_key (grub_disk_t source,
 
   for (i = 0; i < ARRAY_SIZE (header.keyblock); i++)
     if (grub_be_to_cpu32 (header.keyblock[i].active) == LUKS_KEY_ENABLED
-	&& grub_be_to_cpu32 (header.keyblock[i].stripes) > max_stripes)
+        && grub_be_to_cpu32 (header.keyblock[i].stripes) > max_stripes)
       max_stripes = grub_be_to_cpu32 (header.keyblock[i].stripes);
 
   split_key = grub_malloc (keysize * max_stripes);
   if (!split_key)
     return grub_errno;
 
-  if (keyfile_bytes)
+  while (attempts)
     {
-      /* 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))
+      if (keyfile_bytes)
         {
-          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.  */
-  for (i = 0; i < ARRAY_SIZE (header.keyblock); i++)
-    {
-      gcry_err_code_t gcry_err;
-      grub_uint8_t candidate_key[GRUB_CRYPTODISK_MAX_KEYLEN];
-      grub_uint8_t digest[GRUB_CRYPTODISK_MAX_KEYLEN];
-
-      /* Check if keyslot is enabled.  */
-      if (grub_be_to_cpu32 (header.keyblock[i].active) != LUKS_KEY_ENABLED)
-	continue;
-
-      grub_dprintf ("luks", "Trying keyslot %d\n", i);
-
-      /* Calculate the PBKDF2 of the user supplied passphrase.  */
-      gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
-				     passphrase_length,
-				     header.keyblock[i].passwordSalt,
-				     sizeof (header.keyblock[i].passwordSalt),
-				     grub_be_to_cpu32 (header.keyblock[i].
-						       passwordIterations),
-				     digest, keysize);
-
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  return grub_crypto_gcry_error (gcry_err);
-	}
-
-      grub_dprintf ("luks", "PBKDF2 done\n");
-
-      gcry_err = grub_cryptodisk_setkey (dev, digest, keysize); 
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  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.  */
-      if (hdr)
-        {
-	  grub_file_seek (hdr, sector * 512);
-          if (grub_file_read (hdr, split_key, length) != (grub_ssize_t)length)
-            err = GRUB_ERR_READ_ERROR;
+          /* Use bytestring from key file as passphrase */
+          passphrase = keyfile_bytes;
+          passphrase_length = keyfile_bytes_size;
+	  keyfile_bytes = NULL; /* use it only once */
         }
       else
-        err = grub_disk_read (source, sector, 0, length, split_key);
-      if (err)
-	{
-	  grub_free (split_key);
-	  return err;
-	}
-
-      gcry_err = grub_cryptodisk_decrypt (dev, split_key, length, 0);
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  return grub_crypto_gcry_error (gcry_err);
-	}
-
-      /* Merge the decrypted key material to get the candidate master key.  */
-      gcry_err = AF_merge (dev->hash, split_key, candidate_key, keysize,
-			   grub_be_to_cpu32 (header.keyblock[i].stripes));
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  return grub_crypto_gcry_error (gcry_err);
-	}
-
-      grub_dprintf ("luks", "candidate key recovered\n");
-
-      /* Calculate the PBKDF2 of the candidate master key.  */
-      gcry_err = grub_crypto_pbkdf2 (dev->hash, candidate_key,
-				     grub_be_to_cpu32 (header.keyBytes),
-				     header.mkDigestSalt,
-				     sizeof (header.mkDigestSalt),
-				     grub_be_to_cpu32
-				     (header.mkDigestIterations),
-				     candidate_digest,
-				     sizeof (candidate_digest));
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  return grub_crypto_gcry_error (gcry_err);
-	}
-
-      /* Compare the calculated PBKDF2 to the digest stored
-         in the header to see if it's correct.  */
-      if (grub_memcmp (candidate_digest, header.mkDigest,
-		       sizeof (header.mkDigest)) != 0)
-	{
-	  grub_dprintf ("luks", "bad digest\n");
-	  continue;
-	}
+        {
+          /* 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);
 
-      /* TRANSLATORS: It's a cryptographic key slot: one element of an array
-	 where each element is either empty or holds a key.  */
-      grub_printf_ (N_("Slot %d opened\n"), i);
+        }
 
-      /* Set the master key.  */
-      gcry_err = grub_cryptodisk_setkey (dev, candidate_key, keysize); 
-      if (gcry_err)
-	{
-	  grub_free (split_key);
-	  return grub_crypto_gcry_error (gcry_err);
-	}
+      /* Try to recover master key from each active keyslot.  */
+      for (i = 0; i < ARRAY_SIZE (header.keyblock); i++)
+        {
+          gcry_err_code_t gcry_err;
+          grub_uint8_t candidate_key[GRUB_CRYPTODISK_MAX_KEYLEN];
+          grub_uint8_t digest[GRUB_CRYPTODISK_MAX_KEYLEN];
+
+          /* Check if keyslot is enabled.  */
+          if (grub_be_to_cpu32 (header.keyblock[i].active) != LUKS_KEY_ENABLED)
+            continue;
+
+          grub_dprintf ("luks", "Trying keyslot %d\n", i);
+
+          /* Calculate the PBKDF2 of the user supplied passphrase.  */
+          gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
+                                         passphrase_length,
+                                         header.keyblock[i].passwordSalt,
+                                         sizeof (header.keyblock[i].passwordSalt),
+                                         grub_be_to_cpu32 (header.keyblock[i].
+                                         passwordIterations),
+                                         digest, keysize);
+
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              return grub_crypto_gcry_error (gcry_err);
+            }
+
+          grub_dprintf ("luks", "PBKDF2 done\n");
+
+          gcry_err = grub_cryptodisk_setkey (dev, digest, keysize);
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              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.  */
+          if (hdr)
+            {
+              grub_file_seek (hdr, sector * 512);
+              if (grub_file_read (hdr, split_key, length) != (grub_ssize_t)length)
+                err = GRUB_ERR_READ_ERROR;
+            }
+          else
+            err = grub_disk_read (source, sector, 0, length, split_key);
+          if (err)
+            {
+              grub_free (split_key);
+              return err;
+            }
+
+          gcry_err = grub_cryptodisk_decrypt (dev, split_key, length, 0);
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              return grub_crypto_gcry_error (gcry_err);
+            }
+
+          /* Merge the decrypted key material to get the candidate master key.  */
+          gcry_err = AF_merge (dev->hash, split_key, candidate_key, keysize,
+                               grub_be_to_cpu32 (header.keyblock[i].stripes));
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              return grub_crypto_gcry_error (gcry_err);
+            }
+
+          grub_dprintf ("luks", "candidate key recovered\n");
+
+          /* Calculate the PBKDF2 of the candidate master key.  */
+          gcry_err = grub_crypto_pbkdf2 (dev->hash, candidate_key,
+                                     grub_be_to_cpu32 (header.keyBytes),
+                                     header.mkDigestSalt,
+                                     sizeof (header.mkDigestSalt),
+                                     grub_be_to_cpu32
+                                     (header.mkDigestIterations),
+                                     candidate_digest,
+                                     sizeof (candidate_digest));
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              return grub_crypto_gcry_error (gcry_err);
+            }
+
+          /* Compare the calculated PBKDF2 to the digest stored
+             in the header to see if it's correct.  */
+          if (grub_memcmp (candidate_digest, header.mkDigest,
+                                             sizeof (header.mkDigest)) != 0)
+            {
+              grub_dprintf ("luks", "bad digest\n");
+              continue;
+            }
+
+          /* TRANSLATORS: It's a cryptographic key slot: one element of an array
+             where each element is either empty or holds a key.  */
+          grub_printf_ (N_("Slot %d opened\n"), i);
+
+          /* Set the master key.  */
+          gcry_err = grub_cryptodisk_setkey (dev, candidate_key, keysize);
+          if (gcry_err)
+            {
+              grub_free (split_key);
+              return grub_crypto_gcry_error (gcry_err);
+            }
 
-      grub_free (split_key);
+          grub_free (split_key);
 
-      return GRUB_ERR_NONE;
+          return GRUB_ERR_NONE;
+        }
+      grub_printf_ (N_("Failed to decrypt master key.\n"));
+      if (--attempts) grub_printf_ (N_("%u attempt%s remaining.\n"), attempts,
+		                    (attempts==1) ? "" : "s");
     }
 
   grub_free (split_key);
-- 
1.9.1

