Libguestfs - Feb 2016 - [PATCHv2] inspect: get windows drive letters for GPT disks.

This patch updates the guestfs_inspect_get_drive_mappings API call to
also return drive letters for GPT paritions. Previously this worked
only for MBR partitions. This is achieved by matching the GPT partition
GUID with the info stored in the blob from
HKLM\SYSTEM\MountedDevices\DosDevices keys. For GPT partions this blob
contains a "DMIO:ID:" prefix followed by a 16 byte binary GUID.
---

changes since v1:
  * applied style changes from review                                  
  * use guestfs_list_partitions instead of guestfs_list_filesystems    
  * do the GUID endianness conversion correctly                        
  * check all API calls for errors                                     
  * do not call guestfs_canonical_device_name to prevent from changing 
  * block device names, i.e /dev/vda1 as it comes from list_partitions 
  * to /dev/sda1 in inspect_get_drive_mappings    

 src/inspect-fs-windows.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 102 insertions(+), 2 deletions(-)

diff --git a/src/inspect-fs-windows.c b/src/inspect-fs-windows.c
index ccf5cba..1698e81 100644
--- a/src/inspect-fs-windows.c
+++ b/src/inspect-fs-windows.c
@@ -25,6 +25,7 @@
 #include <string.h>
 #include <errno.h>
 #include <iconv.h>
+#include <inttypes.h>
 
 #ifdef HAVE_ENDIAN_H
 #include <endian.h>
@@ -57,6 +58,8 @@ static int check_windows_arch (guestfs_h *g, struct inspect_fs
*fs);
 static int check_windows_software_registry (guestfs_h *g, struct inspect_fs
*fs);
 static int check_windows_system_registry (guestfs_h *g, struct inspect_fs *fs);
 static char *map_registry_disk_blob (guestfs_h *g, const void *blob);
+static char *map_registry_disk_blob_gpt (guestfs_h *g, const void *blob);
+static char *extract_guid_from_registry_blob (guestfs_h *g, const void *blob);
 
 /* XXX Handling of boot.ini in the Perl version was pretty broken.  It
  * essentially didn't do anything for modern Windows guests.
@@ -386,6 +389,7 @@ check_windows_system_registry (guestfs_h *g, struct
inspect_fs *fs)
   int r;
   size_t len = strlen (fs->windows_systemroot) + 64;
   char system[len];
+  char gpt_prefix[] = "DMIO:ID:";
   snprintf (system, len, "%s/system32/config/system",
             fs->windows_systemroot);
 
@@ -490,12 +494,18 @@ check_windows_system_registry (guestfs_h *g, struct
inspect_fs *fs)
       CLEANUP_FREE char *blob = NULL;
       char *device;
       int64_t type;
+      bool is_gpt;
 
       type = guestfs_hivex_value_type (g, v);
       blob = guestfs_hivex_value_value (g, v, &len);
-      if (blob != NULL && type == 3 && len == 12) {
+      is_gpt = memcmp (blob, gpt_prefix, 8) == 0;
+      if (blob != NULL && type == 3 && (len == 12 || is_gpt)) {
         /* Try to map the blob to a known disk and partition. */
-        device = map_registry_disk_blob (g, blob);
+        if (is_gpt)
+          device = map_registry_disk_blob_gpt (g, blob);
+        else
+          device = map_registry_disk_blob (g, blob);
+
         if (device != NULL) {
           fs->drive_mappings[count++] = safe_strndup (g, &key[12], 1);
           fs->drive_mappings[count++] = device;
@@ -605,6 +615,96 @@ map_registry_disk_blob (guestfs_h *g, const void *blob)
   return safe_asprintf (g, "%s%d", devices[i],
partitions->val[j].part_num);
 }
 
+/* Matches Windows registry HKLM\SYSYTEM\MountedDevices\DosDevices blob to
+ * to libguestfs GPT partition device. For GPT disks, the blob is made of
+ * "DMIO:ID:" prefix followed by the GPT partition GUID.
+ */
+static char *
+map_registry_disk_blob_gpt (guestfs_h *g, const void *blob)
+{
+  CLEANUP_FREE_STRING_LIST char **parts = NULL;
+  size_t i;
+
+  parts = guestfs_list_partitions (g);
+
+  if (parts == NULL)
+    return NULL;
+
+  for (i = 0; parts[i] != NULL; i += 2) {
+    CLEANUP_FREE char *fs_guid = NULL;
+    CLEANUP_FREE char *blob_guid = NULL;
+    int partnum;
+    CLEANUP_FREE char *device = NULL;
+    CLEANUP_FREE char *type = NULL;
+
+    partnum = guestfs_part_to_partnum (g, parts[i]);
+
+    if (partnum == -1)
+        continue;
+
+    device = guestfs_part_to_dev (g, parts[i]);
+
+    if (device == NULL)
+        continue;
+
+    type = guestfs_part_get_parttype (g, device);
+
+    if (type == NULL)
+        continue;
+
+    if (STRCASENEQ (type, "gpt"))
+        continue;
+
+    /* get the GPT parition GUID from the partition block device */
+    fs_guid = guestfs_part_get_gpt_guid (g, device, partnum);
+
+    if (fs_guid == NULL)
+      continue;
+
+    /* extract the GUID from the Windows registry blob */
+    blob_guid = extract_guid_from_registry_blob (g, blob);
+
+    /* if both GUIDs match, we have found mapping for out device */
+    if (STRCASEEQ (fs_guid, blob_guid))
+        return safe_strdup (g, parts[i]);
+  }
+
+  return NULL;
+}
+
+/* Extracts the binary GUID stored in blob from Windows registry
+ * HKLM\SYSTYEM\MountedDevices\DosDevices value and converts it to a
+ * GUID string so that it can be matched against libguestfs partition
+ * device GPT GUID.
+ */
+static char *
+extract_guid_from_registry_blob (guestfs_h *g, const void *blob)
+{
+  char guid_bytes[16];
+  uint32_t data1;
+  uint16_t data2, data3;
+  uint64_t data4;
+
+  /* get the GUID bytes from blob (skip 8 byte "DMIO:ID:" prefix) */
+  memcpy (&guid_bytes, (char *) blob + 8, sizeof (guid_bytes));
+
+  /* copy relevant sections from blob to respective ints */
+  memcpy (&data1, guid_bytes, sizeof (data1));
+  memcpy (&data2, guid_bytes + 4, sizeof (data2));
+  memcpy (&data3, guid_bytes + 6, sizeof (data3));
+  memcpy (&data4, guid_bytes + 8, sizeof (data4));
+
+  /* ensure proper endianness */
+  data1 = le32toh (data1);
+  data2 = le16toh (data2);
+  data3 = le16toh (data3);
+  data4 = be64toh (data4);
+
+  return safe_asprintf (g,
+           "%08" PRIX32 "-%04" PRIX16 "-%04"
PRIX16 "-%04" PRIX64 "-%06" PRIX64,
+           data1, data2, data3, (data4 >> 48), (data4 << 16));
+}
+
 /* NB: This function DOES NOT test for the existence of the file.  It
  * will return non-NULL even if the file/directory does not exist.
  * You have to call guestfs_is_file{,_opts} etc.
-- 
2.5.0

On Fri, Feb 05, 2016 at 05:14:43PM -0500, Dawid Zamirski
wrote:
> This patch updates the guestfs_inspect_get_drive_mappings API call to
> also return drive letters for GPT paritions. Previously this worked
> only for MBR partitions. This is achieved by matching the GPT partition
> GUID with the info stored in the blob from
> HKLM\SYSTEM\MountedDevices\DosDevices keys. For GPT partions this blob
> contains a "DMIO:ID:" prefix followed by a 16 byte binary GUID.
Yup, this looks OK to me.  I'll have a play with it tomorrow as I
believe somewhere I have a UEFI (hence GPT) Windows disk image.  If it
works I'll push it upstream.

Thanks,

Rich.
> 
> changes since v1:
>   * applied style changes from review                                  
>   * use guestfs_list_partitions instead of guestfs_list_filesystems    
>   * do the GUID endianness conversion correctly                        
>   * check all API calls for errors                                     
>   * do not call guestfs_canonical_device_name to prevent from changing 
>   * block device names, i.e /dev/vda1 as it comes from list_partitions 
>   * to /dev/sda1 in inspect_get_drive_mappings    
> 
>  src/inspect-fs-windows.c | 104
++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 102 insertions(+), 2 deletions(-)
> 
> diff --git a/src/inspect-fs-windows.c b/src/inspect-fs-windows.c
> index ccf5cba..1698e81 100644
> --- a/src/inspect-fs-windows.c
> +++ b/src/inspect-fs-windows.c
> @@ -25,6 +25,7 @@
>  #include <string.h>
>  #include <errno.h>
>  #include <iconv.h>
> +#include <inttypes.h>
>  
>  #ifdef HAVE_ENDIAN_H
>  #include <endian.h>
> @@ -57,6 +58,8 @@ static int check_windows_arch (guestfs_h *g, struct
inspect_fs *fs);
>  static int check_windows_software_registry (guestfs_h *g, struct
inspect_fs *fs);
>  static int check_windows_system_registry (guestfs_h *g, struct inspect_fs
*fs);
>  static char *map_registry_disk_blob (guestfs_h *g, const void *blob);
> +static char *map_registry_disk_blob_gpt (guestfs_h *g, const void *blob);
> +static char *extract_guid_from_registry_blob (guestfs_h *g, const void
*blob);
>  
>  /* XXX Handling of boot.ini in the Perl version was pretty broken.  It
>   * essentially didn't do anything for modern Windows guests.
> @@ -386,6 +389,7 @@ check_windows_system_registry (guestfs_h *g, struct
inspect_fs *fs)
>    int r;
>    size_t len = strlen (fs->windows_systemroot) + 64;
>    char system[len];
> +  char gpt_prefix[] = "DMIO:ID:";
>    snprintf (system, len, "%s/system32/config/system",
>              fs->windows_systemroot);
>  
> @@ -490,12 +494,18 @@ check_windows_system_registry (guestfs_h *g, struct
inspect_fs *fs)
>        CLEANUP_FREE char *blob = NULL;
>        char *device;
>        int64_t type;
> +      bool is_gpt;
>  
>        type = guestfs_hivex_value_type (g, v);
>        blob = guestfs_hivex_value_value (g, v, &len);
> -      if (blob != NULL && type == 3 && len == 12) {
> +      is_gpt = memcmp (blob, gpt_prefix, 8) == 0;
> +      if (blob != NULL && type == 3 && (len == 12 ||
is_gpt)) {
>          /* Try to map the blob to a known disk and partition. */
> -        device = map_registry_disk_blob (g, blob);
> +        if (is_gpt)
> +          device = map_registry_disk_blob_gpt (g, blob);
> +        else
> +          device = map_registry_disk_blob (g, blob);
> +
>          if (device != NULL) {
>            fs->drive_mappings[count++] = safe_strndup (g, &key[12],
1);
>            fs->drive_mappings[count++] = device;
> @@ -605,6 +615,96 @@ map_registry_disk_blob (guestfs_h *g, const void
*blob)
>    return safe_asprintf (g, "%s%d", devices[i],
partitions->val[j].part_num);
>  }
>  
> +/* Matches Windows registry HKLM\SYSYTEM\MountedDevices\DosDevices blob to
> + * to libguestfs GPT partition device. For GPT disks, the blob is made of
> + * "DMIO:ID:" prefix followed by the GPT partition GUID.
> + */
> +static char *
> +map_registry_disk_blob_gpt (guestfs_h *g, const void *blob)
> +{
> +  CLEANUP_FREE_STRING_LIST char **parts = NULL;
> +  size_t i;
> +
> +  parts = guestfs_list_partitions (g);
> +
> +  if (parts == NULL)
> +    return NULL;
> +
> +  for (i = 0; parts[i] != NULL; i += 2) {
> +    CLEANUP_FREE char *fs_guid = NULL;
> +    CLEANUP_FREE char *blob_guid = NULL;
> +    int partnum;
> +    CLEANUP_FREE char *device = NULL;
> +    CLEANUP_FREE char *type = NULL;
> +
> +    partnum = guestfs_part_to_partnum (g, parts[i]);
> +
> +    if (partnum == -1)
> +        continue;
> +
> +    device = guestfs_part_to_dev (g, parts[i]);
> +
> +    if (device == NULL)
> +        continue;
> +
> +    type = guestfs_part_get_parttype (g, device);
> +
> +    if (type == NULL)
> +        continue;
> +
> +    if (STRCASENEQ (type, "gpt"))
> +        continue;
> +
> +    /* get the GPT parition GUID from the partition block device */
> +    fs_guid = guestfs_part_get_gpt_guid (g, device, partnum);
> +
> +    if (fs_guid == NULL)
> +      continue;
> +
> +    /* extract the GUID from the Windows registry blob */
> +    blob_guid = extract_guid_from_registry_blob (g, blob);
> +
> +    /* if both GUIDs match, we have found mapping for out device */
> +    if (STRCASEEQ (fs_guid, blob_guid))
> +        return safe_strdup (g, parts[i]);
> +  }
> +
> +  return NULL;
> +}
> +
> +/* Extracts the binary GUID stored in blob from Windows registry
> + * HKLM\SYSTYEM\MountedDevices\DosDevices value and converts it to a
> + * GUID string so that it can be matched against libguestfs partition
> + * device GPT GUID.
> + */
> +static char *
> +extract_guid_from_registry_blob (guestfs_h *g, const void *blob)
> +{
> +  char guid_bytes[16];
> +  uint32_t data1;
> +  uint16_t data2, data3;
> +  uint64_t data4;
> +
> +  /* get the GUID bytes from blob (skip 8 byte "DMIO:ID:"
prefix) */
> +  memcpy (&guid_bytes, (char *) blob + 8, sizeof (guid_bytes));
> +
> +  /* copy relevant sections from blob to respective ints */
> +  memcpy (&data1, guid_bytes, sizeof (data1));
> +  memcpy (&data2, guid_bytes + 4, sizeof (data2));
> +  memcpy (&data3, guid_bytes + 6, sizeof (data3));
> +  memcpy (&data4, guid_bytes + 8, sizeof (data4));
> +
> +  /* ensure proper endianness */
> +  data1 = le32toh (data1);
> +  data2 = le16toh (data2);
> +  data3 = le16toh (data3);
> +  data4 = be64toh (data4);
> +
> +  return safe_asprintf (g,
> +           "%08" PRIX32 "-%04" PRIX16 "-%04"
PRIX16 "-%04" PRIX64 "-%06" PRIX64,
> +           data1, data2, data3, (data4 >> 48), (data4 << 16));
> +}
> +
>  /* NB: This function DOES NOT test for the existence of the file.  It
>   * will return non-NULL even if the file/directory does not exist.
>   * You have to call guestfs_is_file{,_opts} etc.
> -- 
> 2.5.0
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
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I got it to work by adding the attached patches.  If you agree
with these changes, please fold them into your patch v3.

Thanks,

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top