disk/cryptodisk: Allows UUIDs to be compared in a dash-insensitive manner

A user can now specify UUID strings with dashes, instead of having to remove
dashes. This is backwards-compatibility preserving and also fixes a source
of user confusion over the inconsistency with how UUIDs are specified
between file system UUIDs and cryptomount UUIDs. Since cryptsetup, the
reference implementation for LUKS, displays and generates UUIDs with dashes
there has been additional confusion when using the UUID strings from
cryptsetup as exact input into GRUB does not find the expected cryptodisk.

A new function grub_uuidcasecmp() is added that is general enough to be used
other places where UUIDs are being compared.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Patrick Steinhardt <ps@pks.im>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/disk/cryptodisk.c

@@ -702,7 +702,7 @@ grub_cryptodisk_open (const char *name, grub_disk_t disk)
   if (grub_memcmp (name, "cryptouuid/", sizeof ("cryptouuid/") - 1) == 0)
     {
       for (dev = cryptodisk_list; dev != NULL; dev = dev->next)
-	if (grub_strcasecmp (name + sizeof ("cryptouuid/") - 1, dev->uuid) == 0)
+	if (grub_uuidcasecmp (name + sizeof ("cryptouuid/") - 1, dev->uuid, sizeof (dev->uuid)) == 0)
 	  break;
     }
   else
@@ -929,7 +929,7 @@ grub_cryptodisk_get_by_uuid (const char *uuid)
 {
   grub_cryptodisk_t dev;
   for (dev = cryptodisk_list; dev != NULL; dev = dev->next)
-    if (grub_strcasecmp (dev->uuid, uuid) == 0)
+    if (grub_uuidcasecmp (dev->uuid, uuid, sizeof (dev->uuid)) == 0)
       return dev;
   return NULL;
 }

grub-core/disk/geli.c

@@ -305,7 +305,7 @@ geli_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
       return NULL;
     }
 
-  if (cargs->search_uuid != NULL && grub_strcasecmp (cargs->search_uuid, uuid) != 0)
+  if (cargs->search_uuid != NULL && grub_uuidcasecmp (cargs->search_uuid, uuid, sizeof (uuid)) != 0)
     {
       grub_dprintf ("geli", "%s != %s\n", uuid, cargs->search_uuid);
       return NULL;

grub-core/disk/luks.c

@@ -66,10 +66,7 @@ static grub_cryptodisk_t
 luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
 {
   grub_cryptodisk_t newdev;
-  const char *iptr;
   struct grub_luks_phdr header;
-  char *optr;
-  char uuid[sizeof (header.uuid) + 1];
   char ciphername[sizeof (header.cipherName) + 1];
   char ciphermode[sizeof (header.cipherMode) + 1];
   char hashspec[sizeof (header.hashSpec) + 1];
@@ -92,19 +89,9 @@ luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
       || grub_be_to_cpu16 (header.version) != 1)
     return NULL;
 
-  grub_memset (uuid, 0, sizeof (uuid));
-  optr = uuid;
-  for (iptr = header.uuid; iptr < &header.uuid[ARRAY_SIZE (header.uuid)];
-       iptr++)
+  if (cargs->search_uuid != NULL && grub_uuidcasecmp (cargs->search_uuid, header.uuid, sizeof (header.uuid)) != 0)
     {
-      if (*iptr != '-')
-	*optr++ = *iptr;
-    }
-  *optr = 0;
-
-  if (cargs->search_uuid != NULL && grub_strcasecmp (cargs->search_uuid, uuid) != 0)
-    {
-      grub_dprintf ("luks", "%s != %s\n", uuid, cargs->search_uuid);
+      grub_dprintf ("luks", "%s != %s\n", header.uuid, cargs->search_uuid);
       return NULL;
     }
 
@@ -123,7 +110,7 @@ luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
   newdev->source_disk = NULL;
   newdev->log_sector_size = GRUB_LUKS1_LOG_SECTOR_SIZE;
   newdev->total_sectors = grub_disk_native_sectors (disk) - newdev->offset_sectors;
-  grub_memcpy (newdev->uuid, uuid, sizeof (uuid));
+  grub_memcpy (newdev->uuid, header.uuid, sizeof (header.uuid));
   newdev->modname = "luks";
 
   /* Configure the hash used for the AF splitter and HMAC.  */
@@ -143,7 +130,7 @@ luks_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
       return NULL;
     }
 
-  COMPILE_TIME_ASSERT (sizeof (newdev->uuid) >= sizeof (uuid));
+  COMPILE_TIME_ASSERT (sizeof (newdev->uuid) >= sizeof (header.uuid));
   return newdev;
 }
 

grub-core/disk/luks2.c

@@ -350,8 +350,6 @@ luks2_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
 {
   grub_cryptodisk_t cryptodisk;
   grub_luks2_header_t header;
-  char uuid[sizeof (header.uuid) + 1];
-  grub_size_t i, j;
 
   if (cargs->check_boot)
     return NULL;
@@ -362,14 +360,9 @@ luks2_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
       return NULL;
     }
 
-  for (i = 0, j = 0; i < sizeof (header.uuid); i++)
-    if (header.uuid[i] != '-')
-      uuid[j++] = header.uuid[i];
-  uuid[j] = '\0';
-
-  if (cargs->search_uuid != NULL && grub_strcasecmp (cargs->search_uuid, uuid) != 0)
+  if (cargs->search_uuid != NULL && grub_uuidcasecmp (cargs->search_uuid, header.uuid, sizeof (header.uuid)) != 0)
     {
-      grub_dprintf ("luks2", "%s != %s\n", uuid, cargs->search_uuid);
+      grub_dprintf ("luks2", "%s != %s\n", header.uuid, cargs->search_uuid);
       return NULL;
     }
 
@@ -377,8 +370,8 @@ luks2_scan (grub_disk_t disk, grub_cryptomount_args_t cargs)
   if (!cryptodisk)
     return NULL;
 
-  COMPILE_TIME_ASSERT (sizeof (cryptodisk->uuid) >= sizeof (uuid));
-  grub_memcpy (cryptodisk->uuid, uuid, sizeof (uuid));
+  COMPILE_TIME_ASSERT (sizeof (cryptodisk->uuid) >= sizeof (header.uuid));
+  grub_memcpy (cryptodisk->uuid, header.uuid, sizeof (header.uuid));
 
   cryptodisk->modname = "luks2";
   return cryptodisk;

include/grub/misc.h

@@ -244,6 +244,36 @@ grub_strncasecmp (const char *s1, const char *s2, grub_size_t n)
     - (int) grub_tolower ((grub_uint8_t) *s2);
 }
 
+/*
+ * Do a case insensitive compare of two UUID strings by ignoring all dashes.
+ * Note that the parameter n, is the number of significant characters to
+ * compare, where significant characters are any except the dash.
+ */
+static inline int
+grub_uuidcasecmp (const char *uuid1, const char *uuid2, grub_size_t n)
+{
+  if (n == 0)
+    return 0;
+
+  while (*uuid1 && *uuid2 && --n)
+    {
+      /* Skip forward to non-dash on both UUIDs. */
+      while ('-' == *uuid1)
+        ++uuid1;
+
+      while ('-' == *uuid2)
+        ++uuid2;
+
+      if (grub_tolower ((grub_uint8_t) *uuid1) != grub_tolower ((grub_uint8_t) *uuid2))
+	break;
+
+      uuid1++;
+      uuid2++;
+    }
+
+  return (int) grub_tolower ((grub_uint8_t) *uuid1) - (int) grub_tolower ((grub_uint8_t) *uuid2);
+}
+
 /*
  * Note that these differ from the C standard's definitions of strtol,
  * strtoul(), and strtoull() by the addition of two const qualifiers on the end