[PATCH v7 5/6] cryptodisk: enable the backends to implement key files

[Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>]

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

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>
Reviewed-by: Patrick Steinhardt <ps@pks.im>
---
Changelog since v3:
-------------------
- Fixed the size formating with PRIuGRUB_SIZE
- Added Reviewed-by

ChangeLog since v4:
-------------------
- Style fixes:
  - Added missing space between function and '('
  - Removed trailing backslashes in split strings

ChangeLog since v5:
-------------------
- No changes

ChangeLog since v6:
-------------------
- Fixed format string conversions issues found by Glenn Washburn:
  - "The type of keyfile->size is grub_off_t which is 
     typedef'd from grub_uint64_t. 
     [...] when compiling for i386, PRIuGRUB_SIZE expands
     to %lu, which accepts a 32-bit uint.
     This will cause the strict format string checking to fail 
     the build."
  - "The macro GRUB_CRYPTODISK_MAX_KEYFILE_SIZE gets expanded
     to an integer literal which gets type cast as an int,
     but PRIuGRUB_SIZE expects long or long long."
- Rebased. The rebase was needed due this commits:
  - 0eb44d319 luks2: Rename source disk variable named
                     "disk" to "source" as in luks.c
    => No changes to this patch, it just shows in the
       context lines.


---
 grub-core/disk/cryptodisk.c | 86 ++++++++++++++++++++++++++++++++++++-
 grub-core/disk/geli.c       |  7 +--
 grub-core/disk/luks.c       |  7 ++-
 grub-core/disk/luks2.c      |  7 +--
 include/grub/cryptodisk.h   |  5 ++-
 include/grub/file.h         |  2 +
 6 files changed, 105 insertions(+), 9 deletions(-)

diff --git a/grub-core/disk/cryptodisk.c b/grub-core/disk/cryptodisk.c
index fec949ad0..11c0f7ab6 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},
     {"header", 'H', 0, N_("Read 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}
   };
 
@@ -969,6 +972,8 @@ 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_ssize_t key_size;
 
 static void
 cryptodisk_close (grub_cryptodisk_t dev)
@@ -999,7 +1004,7 @@ 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, key_size);
     if (err)
     {
       cryptodisk_close (dev);
@@ -1109,6 +1114,85 @@ grub_cmd_cryptomount (grub_extcmd_context_t ctxt, int argc, char **args)
     hdr = NULL;
 
   have_it = 0;
+  key = NULL;
+
+  if (state[4].set) /* keyfile */
+    {
+      const char *p = NULL;
+      grub_file_t keyfile;
+      int keyfile_offset;
+      grub_size_t requested_keyfile_size = 0;
+
+
+      if (state[5].set) /* keyfile-offset */
+	{
+	  keyfile_offset = grub_strtoul (state[5].arg, &p, 0);
+
+	  if (grub_errno != GRUB_ERR_NONE)
+	    return grub_errno;
+
+	  if (*p != '\0')
+	    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+			       N_("unrecognized number"));
+	}
+      else
+	{
+	  keyfile_offset = 0;
+	}
+
+      if (state[6].set) /* keyfile-size */
+	{
+	  requested_keyfile_size = grub_strtoul (state[6].arg, &p, 0);
+
+	  if (*p != '\0')
+	    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+			       N_("unrecognized number"));
+
+	  if (grub_errno != GRUB_ERR_NONE)
+	    return grub_errno;
+
+	  if (requested_keyfile_size > GRUB_CRYPTODISK_MAX_KEYFILE_SIZE)
+	    return grub_error (GRUB_ERR_OUT_OF_RANGE,
+			      N_("Key file size exceeds maximum (%d)\n"),
+			      GRUB_CRYPTODISK_MAX_KEYFILE_SIZE);
+
+	  if (requested_keyfile_size == 0)
+	    return grub_error (GRUB_ERR_OUT_OF_RANGE,
+			      N_("Key file size is 0\n"));
+	}
+
+      keyfile = grub_file_open (state[4].arg,
+				GRUB_FILE_TYPE_CRYPTODISK_ENCRYPTION_KEY);
+      if (!keyfile)
+	return grub_errno;
+
+      if (grub_file_seek (keyfile, keyfile_offset) == (grub_off_t)-1)
+	return grub_errno;
+
+      if (requested_keyfile_size)
+	{
+	  if (requested_keyfile_size > (keyfile->size - keyfile_offset))
+	    return grub_error (GRUB_ERR_FILE_READ_ERROR,
+			       N_("Keyfile is too small: "
+				  "requested %" PRIuGRUB_SIZE " bytes, "
+				  "but the file only has %" PRIuGRUB_UINT64_T
+				  " bytes.\n"),
+			       requested_keyfile_size,
+			       keyfile->size);
+
+	  key_size = requested_keyfile_size;
+	}
+      else
+	{
+	  key_size = keyfile->size - keyfile_offset;
+	}
+
+      if (grub_file_read (keyfile, keyfile_buffer, key_size) != key_size)
+	return grub_error (GRUB_ERR_FILE_READ_ERROR,
+			   (N_("Error reading key file\n")));
+      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 d4d537e05..8fb24cc5b 100644
--- a/grub-core/disk/geli.c
+++ b/grub-core/disk/geli.c
@@ -404,7 +404,8 @@ geli_scan (grub_disk_t disk, const char *check_uuid, int boot_only,
 }
 
 static grub_err_t
-geli_recover_key (grub_disk_t source, grub_cryptodisk_t dev, grub_file_t hdr)
+geli_recover_key (grub_disk_t source, grub_cryptodisk_t dev, grub_file_t hdr,
+		  grub_uint8_t *key, grub_size_t keyfile_size)
 {
   grub_size_t keysize;
   grub_uint8_t digest[GRUB_CRYPTO_MAX_MDLEN];
@@ -420,8 +421,8 @@ geli_recover_key (grub_disk_t source, grub_cryptodisk_t dev, grub_file_t hdr)
   grub_disk_addr_t sector;
   grub_err_t err;
 
-  /* Detached headers are not implemented yet */
-  if (hdr)
+  /* Detached headers and keyfiles are not implemented yet */
+  if (hdr || key || keyfile_size)
     return GRUB_ERR_NOT_IMPLEMENTED_YET;
 
   if (dev->cipher->cipher->blocksize > GRUB_CRYPTO_MAX_CIPHER_BLOCKSIZE)
diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
index 1c518902b..b7867585a 100644
--- a/grub-core/disk/luks.c
+++ b/grub-core/disk/luks.c
@@ -162,7 +162,8 @@ luks_scan (grub_disk_t disk, const char *check_uuid, int check_boot,
 }
 
 static grub_err_t
-luks_recover_key (grub_disk_t source, grub_cryptodisk_t dev, grub_file_t hdr)
+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)
 {
   struct grub_luks_phdr header;
   grub_size_t keysize;
@@ -176,6 +177,10 @@ luks_recover_key (grub_disk_t source, grub_cryptodisk_t dev, grub_file_t hdr)
   char *tmp;
   grub_uint32_t sector;
 
+  /* Keyfiles are not implemented yet */
+  if (keyfile_bytes || keyfile_bytes_size)
+     return GRUB_ERR_NOT_IMPLEMENTED_YET;
+
   if (hdr)
     {
       if (grub_file_seek (hdr, 0) == (grub_off_t) -1)
diff --git a/grub-core/disk/luks2.c b/grub-core/disk/luks2.c
index 237b2aa77..f3e293a9e 100644
--- a/grub-core/disk/luks2.c
+++ b/grub-core/disk/luks2.c
@@ -536,7 +536,8 @@ luks2_decrypt_key (grub_uint8_t *out_key,
 
 static grub_err_t
 luks2_recover_key (grub_disk_t source, grub_cryptodisk_t crypt,
-		   grub_file_t hdr_file)
+		   grub_file_t hdr_file, grub_uint8_t *key,
+		   grub_size_t keyfile_size)
 {
   grub_uint8_t candidate_key[GRUB_CRYPTODISK_MAX_KEYLEN];
   char passphrase[MAX_PASSPHRASE], cipher[32];
@@ -550,8 +551,8 @@ luks2_recover_key (grub_disk_t source, grub_cryptodisk_t crypt,
   grub_json_t *json = NULL, keyslots;
   grub_err_t ret;
 
-  /* Detached headers are not implemented yet */
-  if (hdr_file)
+  /* Detached headers and keyfiles are not implemented yet */
+  if (hdr_file || key || keyfile_size)
     return GRUB_ERR_NOT_IMPLEMENTED_YET;
 
   ret = luks2_read_header (source, &header);
diff --git a/include/grub/cryptodisk.h b/include/grub/cryptodisk.h
index d6f2f6e2c..572dbc782 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
@@ -115,7 +117,8 @@ 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_file_t hdr, grub_uint8_t *key,
+			     grub_size_t keyfile_size);
 };
 typedef struct grub_cryptodisk_dev *grub_cryptodisk_dev_t;
 
diff --git a/include/grub/file.h b/include/grub/file.h
index a7d7be853..97678aa45 100644
--- a/include/grub/file.h
+++ b/include/grub/file.h
@@ -92,6 +92,8 @@ enum grub_file_type
     GRUB_FILE_TYPE_ZFS_ENCRYPTION_KEY,
     /* File holiding the encryption metadata header */
     GRUB_FILE_TYPE_CRYPTODISK_DETACHED_HEADER,
+    /* File holiding 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.  */
-- 
2.29.2