Source code for dfvfs.file_io.cs_file_io

# -*- coding: utf-8 -*-
"""The Core Storage (CS) file-like object."""

import os

from dfvfs.file_io import file_io
from dfvfs.lib import cs_helper
from dfvfs.lib import errors
from dfvfs.resolver import resolver


[docs] class CSFile(file_io.FileIO): """File input/output (IO) object using pyfvde."""
[docs] def __init__(self, resolver_context, path_spec): """Initializes a file input/output (IO) object. Args: resolver_context (Context): resolver context. path_spec (PathSpec): a path specification. """ super(CSFile, self).__init__(resolver_context, path_spec) self._file_system = None self._fvde_logical_volume = None
def _Close(self): """Closes the file-like object.""" self._fvde_logical_volume = None self._file_system = None def _Open(self, mode='rb'): """Opens the file-like object defined by path specification. Args: mode (Optional[str]): file access mode. Raises: AccessError: if the access to open the file was denied. IOError: if the file-like object could not be opened or the Core Storage logical volume could not be retrieved or unlocked. OSError: if the file-like object could not be opened or the Core Storage logical volume could not be retrieved or unlocked. PathSpecError: if the path specification is incorrect. """ volume_index = cs_helper.CSPathSpecGetVolumeIndex(self._path_spec) if volume_index is None: raise errors.PathSpecError( 'Unable to retrieve volume index from path specification.') resolver.Resolver.key_chain.ExtractCredentialsFromPathSpec(self._path_spec) self._file_system = resolver.Resolver.OpenFileSystem( self._path_spec, resolver_context=self._resolver_context) fvde_volume_group = self._file_system.GetFVDEVolumeGroup() if (volume_index < 0 or volume_index >= fvde_volume_group.number_of_logical_volumes): raise errors.PathSpecError(( f'Unable to retrieve logical volume index: {volume_index:d} from ' f'path specification.')) fvde_logical_volume = fvde_volume_group.get_logical_volume(volume_index) try: is_locked = not cs_helper.CSUnlockLogicalVolume( fvde_logical_volume, self._path_spec, resolver.Resolver.key_chain) except IOError as exception: raise IOError(f'Unable to unlock volume with error: {exception!s}') if is_locked: raise IOError('Unable to unlock volume.') self._fvde_logical_volume = fvde_logical_volume @property def is_locked(self): """bool: True if the volume is locked.""" return self._fvde_logical_volume.is_locked() # Note: that the following functions do not follow the style guide # because they are part of the file-like object interface. # pylint: disable=invalid-name
[docs] def read(self, size=None): """Reads a byte string from the file-like object at the current offset. The function will read a byte string of the specified size or all of the remaining data if no size was specified. Args: size (Optional[int]): number of bytes to read, where None is all remaining data. Returns: bytes: data read. Raises: IOError: if the read failed. OSError: if the read failed. """ if not self._is_open: raise IOError('Not opened.') return self._fvde_logical_volume.read(size)
[docs] def seek(self, offset, whence=os.SEEK_SET): """Seeks to an offset within the file-like object. Args: offset (int): offset to seek to. whence (Optional(int)): value that indicates whether offset is an absolute or relative position within the file. Raises: IOError: if the seek failed. OSError: if the seek failed. """ if not self._is_open: raise IOError('Not opened.') self._fvde_logical_volume.seek(offset, whence)
[docs] def get_offset(self): """Retrieves the current offset into the file-like object. Returns: int: current offset into the file-like object. Raises: IOError: if the file-like object has not been opened. OSError: if the file-like object has not been opened. """ if not self._is_open: raise IOError('Not opened.') return self._fvde_logical_volume.get_offset()
[docs] def get_size(self): """Retrieves the size of the file-like object. Returns: int: size of the file-like object data. Raises: IOError: if the file-like object has not been opened. OSError: if the file-like object has not been opened. """ if not self._is_open: raise IOError('Not opened.') return self._fvde_logical_volume.size