Changed APFS container back-end to support apfs{GUID} alias #739 (#740)

dfvfs/lib/apfs_helper.py

@@ -2,38 +2,6 @@
 """Helper functions for Apple File System (APFS) support."""
 
 
-_APFS_LOCATION_PREFIX = '/apfs'
-_APFS_LOCATION_PREFIX_LENGTH = len(_APFS_LOCATION_PREFIX)
-
-
-def APFSContainerPathSpecGetVolumeIndex(path_spec):
-  """Retrieves the volume index from the path specification.
-
-  Args:
-    path_spec (PathSpec): path specification.
-
-  Returns:
-    int: volume index or None if the index cannot be determined.
-  """
-  volume_index = getattr(path_spec, 'volume_index', None)
-  if volume_index is not None:
-    return volume_index
-
-  location = getattr(path_spec, 'location', None)
-  if location is None or not location.startswith(_APFS_LOCATION_PREFIX):
-    return None
-
-  try:
-    volume_index = int(location[_APFS_LOCATION_PREFIX_LENGTH:], 10) - 1
-  except (TypeError, ValueError):
-    volume_index = None
-
-  if volume_index is None or volume_index < 0 or volume_index > 99:
-    volume_index = None
-
-  return volume_index
-
-
 def APFSUnlockVolume(fsapfs_volume, path_spec, key_chain):
   """Unlocks an APFS volume using the path specification.
 

dfvfs/vfs/apfs_container_directory.py

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 """The APFS container directory implementation."""
 
-from dfvfs.lib import apfs_helper
 from dfvfs.path import apfs_container_path_spec
 from dfvfs.vfs import directory
 
@@ -19,19 +18,15 @@ def _EntriesGenerator(self):
       APFSContainerPathSpec: a path specification.
     """
     # Only the virtual root file has directory entries.
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(
-        self.path_spec)
-    if volume_index is not None:
-      return
-
-    location = getattr(self.path_spec, 'location', None)
-    if location is None or location != self._file_system.LOCATION_ROOT:
-      return
-
-    fsapfs_container = self._file_system.GetAPFSContainer()
-
-    for volume_index in range(0, fsapfs_container.number_of_volumes):
-      apfs_volume_index = volume_index + 1
-      yield apfs_container_path_spec.APFSContainerPathSpec(
-          location=f'/apfs{apfs_volume_index:d}', parent=self.path_spec.parent,
-          volume_index=volume_index)
+    volume_index = self._file_system.GetVolumeIndexByPathSpec(self.path_spec)
+    if volume_index is None:
+      location = getattr(self.path_spec, 'location', None)
+      if location and location == self._file_system.LOCATION_ROOT:
+        fsapfs_container = self._file_system.GetAPFSContainer()
+
+        for volume_index in range(0, fsapfs_container.number_of_volumes):
+          apfs_volume_index = volume_index + 1
+          apfs_volume_location = f'/apfs{apfs_volume_index:d}'
+          yield apfs_container_path_spec.APFSContainerPathSpec(
+              location=apfs_volume_location, parent=self.path_spec.parent,
+              volume_index=volume_index)

dfvfs/vfs/apfs_container_file_entry.py

@@ -16,7 +16,7 @@ class APFSContainerFileEntry(file_entry.FileEntry):
 
   def __init__(
       self, resolver_context, file_system, path_spec, is_root=False,
-      is_virtual=False):
+      is_virtual=False, volume_index=None):
     """Initializes a file entry.
 
     Args:
@@ -27,6 +27,7 @@ def __init__(
           of the corresponding file system.
       is_virtual (Optional[bool]): True if the file entry is a virtual file
           entry emulated by the corresponding file system.
+      volume_index (Optional[int]): volume index or None.
 
     Raises:
       BackEndError: when the fsapfs volume is missing in a non-virtual
@@ -42,6 +43,7 @@ def __init__(
         is_virtual=is_virtual)
     self._name = None
     self._fsapfs_volume = fsapfs_volume
+    self._volume_index = volume_index
 
     if self._is_virtual:
       self.entry_type = definitions.FILE_ENTRY_TYPE_DIRECTORY
@@ -80,17 +82,17 @@ def _GetSubFileEntries(self):
   def name(self):
     """str: name of the file entry, which does not include the full path."""
     if self._name is None:
-      location = getattr(self.path_spec, 'location', None)
-      if location is not None:
-        self._name = self._file_system.BasenamePath(location)
+      self._name = ''
+
+      # Prefer generating the name seeing that the APFS container back-end
+      # supports aliases, such as "/apfs1" and "/apfs{UUID}".
+      if self._volume_index is not None:
+        apfs_volume_index = self._volume_index + 1
+        self._name = f'apfs{apfs_volume_index:d}'
       else:
-        volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(
-            self.path_spec)
-        if volume_index is not None:
-          apfs_volume_index = volume_index + 1
-          self._name = f'apfs{apfs_volume_index:d}'
-        else:
-          self._name = ''
+        location = getattr(self.path_spec, 'location', None)
+        if location is not None:
+          self._name = self._file_system.BasenamePath(location)
 
     return self._name
 
@@ -122,9 +124,7 @@ def GetParentFileEntry(self):
     Returns:
       APFSContainerFileEntry: parent file entry or None if not available.
     """
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(
-        self.path_spec)
-    if volume_index is None:
+    if self._volume_index is None:
       return None
 
     return self._file_system.GetRootFileEntry()

dfvfs/vfs/apfs_container_file_system.py

@@ -3,7 +3,6 @@
 
 import pyfsapfs
 
-from dfvfs.lib import apfs_helper
 from dfvfs.lib import definitions
 from dfvfs.lib import errors
 from dfvfs.path import apfs_container_path_spec
@@ -17,6 +16,8 @@ class APFSContainerFileSystem(file_system.FileSystem):
 
   TYPE_INDICATOR = definitions.TYPE_INDICATOR_APFS_CONTAINER
 
+  _APFS_LOCATION_PREFIX = '/apfs'
+
   def __init__(self, resolver_context, path_spec):
     """Initializes an APFS container file system.
 
@@ -72,7 +73,7 @@ def FileEntryExistsByPathSpec(self, path_spec):
     Returns:
       bool: True if the file entry exists.
     """
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
+    volume_index = self.GetVolumeIndexByPathSpec(path_spec)
 
     # The virtual root file has no corresponding volume index but
     # should have a location.
@@ -99,7 +100,7 @@ def GetAPFSVolumeByPathSpec(self, path_spec):
     Returns:
       pyfsapfs.volume: an APFS volume or None if not available.
     """
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
+    volume_index = self.GetVolumeIndexByPathSpec(path_spec)
     if volume_index is None:
       return None
 
@@ -114,7 +115,7 @@ def GetFileEntryByPathSpec(self, path_spec):
     Returns:
       APFSContainerFileEntry: a file entry or None if not exists.
     """
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
+    volume_index = self.GetVolumeIndexByPathSpec(path_spec)
 
     # The virtual root file has no corresponding volume index but
     # should have a location.
@@ -132,7 +133,7 @@ def GetFileEntryByPathSpec(self, path_spec):
       return None
 
     return apfs_container_file_entry.APFSContainerFileEntry(
-        self._resolver_context, self, path_spec)
+        self._resolver_context, self, path_spec, volume_index=volume_index)
 
   def GetRootFileEntry(self):
     """Retrieves the root file entry.
@@ -143,3 +144,40 @@ def GetRootFileEntry(self):
     path_spec = apfs_container_path_spec.APFSContainerPathSpec(
         location=self.LOCATION_ROOT, parent=self._path_spec.parent)
     return self.GetFileEntryByPathSpec(path_spec)
+
+  def GetVolumeIndexByPathSpec(self, path_spec):
+    """Retrieves the volume index for a path specification.
+
+    Args:
+      path_spec (PathSpec): path specification.
+
+    Returns:
+      int: volume index or None if the index cannot be determined.
+    """
+    volume_index = getattr(path_spec, 'volume_index', None)
+    if volume_index is not None:
+      return volume_index
+
+    location = getattr(path_spec, 'location', None)
+    if location is None or location[:5] != self._APFS_LOCATION_PREFIX:
+      return None
+
+    volume_index = None
+
+    if len(location) > 6 and location[5] == '{' and location[-1] == '}':
+      for index, fsapfs_volume in enumerate(
+          self._fsapfs_container.volumes):
+        if fsapfs_volume.identifier == location[6:-1]:
+          volume_index = index
+          break
+
+    else:
+      try:
+        volume_index = int(location[5:], 10) - 1
+      except (TypeError, ValueError):
+        pass
+
+    if volume_index is None or volume_index < 0 or volume_index > 99:
+      volume_index = None
+
+    return volume_index

tests/lib/apfs_helper.py

@@ -6,9 +6,7 @@
 
 from dfvfs.lib import apfs_helper
 from dfvfs.lib import definitions
-from dfvfs.path import apfs_container_path_spec
 from dfvfs.path import factory as path_spec_factory
-from dfvfs.path import fake_path_spec
 from dfvfs.resolver import context
 from dfvfs.resolver import resolver
 
@@ -20,54 +18,6 @@ class APFSContainerHelperTest(shared_test_lib.BaseTestCase):
 
   _APFS_PASSWORD = 'apfs-TEST'
 
-  def testAPFSContainerPathSpecGetVolumeIndex(self):
-    """Tests the APFSContainerPathSpecGetVolumeIndex function."""
-    test_fake_path_spec = fake_path_spec.FakePathSpec(location='/')
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        parent=test_fake_path_spec)
-
-    self.assertIsNotNone(path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertIsNone(volume_index)
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        location='/apfs2', parent=test_fake_path_spec)
-
-    self.assertIsNotNone(path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertEqual(volume_index, 1)
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        volume_index=1, parent=test_fake_path_spec)
-
-    self.assertIsNotNone(path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertEqual(volume_index, 1)
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        location='/apfs2', volume_index=1, parent=test_fake_path_spec)
-
-    self.assertIsNotNone(path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertEqual(volume_index, 1)
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        location='/apfs', parent=test_fake_path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertIsNone(volume_index)
-
-    path_spec = apfs_container_path_spec.APFSContainerPathSpec(
-        location='/apfs101', parent=test_fake_path_spec)
-
-    volume_index = apfs_helper.APFSContainerPathSpecGetVolumeIndex(path_spec)
-    self.assertIsNone(volume_index)
-
   def testAPFSUnlockVolumeOnAPFS(self):
     """Tests the APFSUnlockVolume function on an APFS image."""
     resolver_context = context.Context()