/usr/lib/python2.7/dist-packages/rekall/plugins/overlays/linux/vfs.py is in python-rekall-core 1.6.0+dfsg-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""
@author: Michael Cohen
@license: GNU General Public License 2.0 or later
@contact: scudette@gmail.com
@organization: Google Inc.
This file encapsulates various virtual file system operations for supported
linux versions. The code is basically copied from the kernel sources of the
relevant versions.
"""
import posixpath
import math
from rekall import obj
from rekall import utils
from rekall.plugins.overlays import basic
class File(object):
"""Represents a Linux file."""
def __init__(self, filename=None, mountpoint=None, dentry=None,
is_root=False, session=None):
if isinstance(filename, (basestring, basic.String)):
self.filename = utils.SmartUnicode(filename).split("/")
elif isinstance(filename, list):
self.filename = filename
elif not filename:
self.filename = []
else:
raise TypeError("Invalid filename.")
self.mountpoint = mountpoint or MountPoint()
self.dentry = dentry
self.is_root = is_root
self.session = session
@utils.safe_property
def fullpath(self):
if self.is_root:
return self.mountpoint.name
else:
return '/'.join([self.mountpoint.name.rstrip("/"),
'/'.join(self.filename)])
@utils.safe_property
def name(self):
try:
return self.filename[-1] or obj.NoneObject()
except IndexError:
return obj.NoneObject()
@utils.safe_property
def size(self):
return self.dentry.d_inode.i_size
@utils.safe_property
def extents(self):
"""Returns a list of ranges for which we have data in memory."""
page_size = self.session.kernel_address_space.PAGE_SIZE
range_start = None
index = 0
while index <= (self.size / page_size):
page = self._radix_tree_lookup(index)
if page:
# Start a new range if previously there was no data.
if range_start == None:
range_start = index * page_size
else:
# Finish the current range if previously we had data.
if range_start != None:
range_end = (index * page_size) -1
range_end = min(self.size, range_end)
yield (range_start, range_end)
range_start = None
index += 1
# Close the last range, as if there was data in the tail of the file, we
# wouldn't have outputted it.
# Since we cannot guarantee that there won't be data in the last index+1
# of the radix tree we do an explicit check, instead of walking
# total_indexes+1 in the algorithm above.
if range_start != None:
range_end = (index * page_size) - 1
range_end = min(self.size, range_end)
yield (range_start, range_end)
def _radix_tree_is_indirect_ptr(self, ptr):
"""See include/linux/radix-tree.h -> is_indirect_ptr()."""
return ptr & 1
def _radix_tree_indirect_to_ptr(self, node_p):
"""See lib/radix-tree.c -> indirect_to_ptr()."""
return self.dentry.obj_profile.Object(
"Pointer", target="radix_tree_node",
value=node_p.v() & ~1,
profile=node_p.obj_profile,
vm=node_p.obj_vm)
def _radix_tree_lookup_element(self, index, is_slot):
"""See lib/radix-tree.c -> radix_tree_lookup_element().
Searches either for the slot or the node of the index of a radix_tree.
"""
root = self.dentry.d_inode.i_mapping.page_tree
node = root.rnode
if not node:
return obj.NoneObject()
# The RADIX_TREE_MAP_SIZE is the length of the node.slots array.
self.RADIX_TREE_MAP_SIZE = len(node.slots)
self.RADIX_TREE_MAP_SHIFT = int(
math.log(self.RADIX_TREE_MAP_SIZE) / math.log(2))
self.RADIX_TREE_MAP_MASK = self.RADIX_TREE_MAP_SIZE - 1
if not self._radix_tree_is_indirect_ptr(node):
if index > 0:
return obj.NoneObject()
if is_slot:
return node.reference()
else:
return node
node = self._radix_tree_indirect_to_ptr(node)
height = node.height
shift = (height - 1) * self.RADIX_TREE_MAP_SHIFT
slot = -1
while 1:
idx = (index >> shift) & self.RADIX_TREE_MAP_MASK
node = node.slots[idx]
node = node.cast("Pointer", target="radix_tree_node")
slot = node.reference()
shift -= self.RADIX_TREE_MAP_SHIFT
height -= 1
if height <= 0:
break
if slot == -1:
return obj.NoneObject()
if is_slot:
return slot
else:
return self._radix_tree_indirect_to_ptr(node)
def _radix_tree_lookup_slot(self, index):
"""See lib/radix-tree.c ."""
return self._radix_tree_lookup_element(index, 1)
def _radix_tree_lookup(self, index):
"""See lib/radix-tree.c ."""
return self._radix_tree_lookup_element(index, 0)
def GetPage(self, page_index):
page_size = self.session.kernel_address_space.PAGE_SIZE
page = self._radix_tree_lookup(page_index)
if page:
page = page.dereference_as("page")
return page.read(0, page_size)
def walk(self, recursive=False, unallocated=False):
if not self.is_directory():
return
results = []
for dentry in self.dentry.d_subdirs.list_of_type_fast("dentry", "d_u"):
filename = dentry.d_name.name.deref()
inode = dentry.d_inode
# If we are the root pseudofile, we have no name.
if self.is_root:
child_filename = unicode(filename)
else:
child_filename = self.filename + [unicode(filename)]
new_file = File(filename=child_filename,
mountpoint=self.mountpoint,
dentry=dentry,
session=self.session)
if unallocated or (filename != None and inode):
results.append(new_file)
if recursive and inode and inode.type.S_IFDIR:
if recursive and inode.type.S_IFDIR:
for sub_file in new_file.walk(recursive=recursive,
unallocated=unallocated):
results.append(sub_file)
for file_ in sorted(results, key=lambda x: x.fullpath):
yield file_
def __eq__(self, other):
if isinstance(other, File):
return (self.fullpath == other.fullpath and
self.dentry == other.dentry and
self.mountpoint == other.mountpoint)
return False
def is_directory(self):
return self.dentry and self.dentry.d_inode.type.S_IFDIR
class MountPoint(object):
"""Represents a Linux mount point."""
def __init__(self, device="(undefined device)",
mount_path="(undefined mount path)",
superblock=None, flags=None, session=None):
self.device = device
self.name = unicode(mount_path)
self.sb = superblock
self.flags = flags
self.session = session
def walk(self, recursive=False, unallocated=False):
"""Yields Files for each file in this mountpoint."""
if self.sb and self.sb.s_root.d_inode.type.S_IFDIR:
# Create a dummy file for the root of the filesystem to walk it.
root_file = File(mountpoint=self,
dentry=self.sb.s_root,
is_root=True,
session=self.session)
for sub_file in root_file.walk(recursive=recursive,
unallocated=unallocated):
yield sub_file
@utils.safe_property
def fstype(self):
return self.sb.s_type.name.deref()
def __eq__(self, other):
if isinstance(other, MountPoint):
return (self.sb == other.sb
and self.device == other.device
and self.name == other.name)
return False
class FileName(object):
"""An object to represent a filename."""
MAX_DEPTH = 15
def __init__(self, components=None, start_dentry=None):
self.start_dentry = start_dentry
self.mount_point = "/"
self.deleted = False
if components is None:
components = []
self.path_components = components
def PrependName(self, component):
self.path_components.insert(0, utils.SmartUnicode(component))
def FormatName(self, root_dentry):
# For sockets we need more info.
if len(self.path_components) >= self.MAX_DEPTH:
return obj.NoneObject(
u"Depth exceeded at %s" % "/".join(self.path_components))
if self.mount_point == "socket:":
return "{0}/{1}[{2}]".format(
self.mount_point, root_dentry.d_name.name.deref(),
self.start_dentry.d_inode.i_ino)
elif self.mount_point == "pipe:":
return "{0}[{1}]".format(
self.mount_point, self.start_dentry.d_inode.i_ino)
elif self.mount_point == "anon_inode:":
return u"anon_inode:%s" % self.start_dentry.d_name.name.deref()
# This is the normal condition for files.
else:
return self.__unicode__()
def __unicode__(self):
if self.deleted:
deleted = " (deleted) "
else:
deleted = ""
return u"%s%s%s" % (self.mount_point,
"/".join(self.path_components), deleted)
class Linux3VFS(object):
"""This is the implementation specific VFS operations.
Most of the code here is a direct copy of the methods in linux/fs/dcache.c
http://lxr.free-electrons.com/source/fs/mount.h?v=3.7#L53
http://lxr.free-electrons.com/source/fs/dcache.c?v=3.7#L2576
"""
def __init__(self, profile=None):
# Autodetect kernel version
self.profile = profile
if self.profile.get_constant("set_mphash_entries"):
self.prepend_path = self._prepend_path314
elif self.profile.has_type("mount"):
self.prepend_path = self._prepend_path303
else:
self.prepend_path = self._prepend_path300
def get_path(self, task, filp):
"""Resolve the dentry, vfsmount relative to this task's chroot.
Returns:
An absolute path to the global filesystem mount. (I.e. we do not
truncate the path at the chroot point as the kernel does).
"""
return posixpath.normpath(self.prepend_path(filp.f_path, task.fs.root))
def _real_mount(self, vfsmnt):
"""Return the mount container of the vfsmnt object."""
return basic.container_of(vfsmnt, "mount", "mnt").reference()
def _mnt_has_parent(self, mnt):
return mnt != mnt.mnt_parent
def _prepend_path300(self, path, root):
"""Return the path of a dentry for 3.0-3.2 kernels.
http://lxr.free-electrons.com/source/fs/dcache.c?v=3.2#L2576
"""
# Ensure we can not get into an infinite loop here by limiting the
# depth.
depth = 0
dentry = path.dentry
vfsmnt = path.mnt
result = FileName(start_dentry=dentry)
# Check for deleted dentry.
if dentry.d_flags.DCACHE_UNHASHED and not dentry.is_root:
result.deleted = True
while dentry != root.dentry or vfsmnt != root.mnt:
# Control the depth.
depth += 1
if depth >= result.MAX_DEPTH:
break
if dentry == vfsmnt.mnt_root or dentry.is_root:
# Global root?
if vfsmnt.mnt_parent == vfsmnt:
result.PrependName("")
break
dentry = vfsmnt.mnt_mountpoint
vfsmnt = vfsmnt.mnt_parent
continue
parent = dentry.d_parent
if dentry.d_name.name:
result.PrependName(dentry.d_name.name.deref())
dentry = parent
# When we get here dentry is a root dentry and mnt is the mount point it
# is mounted on. There are some special mount points we want to
# highlight.
result.mount_point = vfsmnt.mnt_mountpoint.d_name.name.deref()
return result.FormatName(dentry)
def _prepend_path303(self, path, root):
"""Return the path of a dentry for 3.3-3.13 kernels.
Linxu 3.3 introduced the struct mount, and moved some fields between
struct mount and struct vfsmount.
http://lxr.free-electrons.com/source/fs/dcache.c?v=3.7#L2576
"""
# Ensure we can not get into an infinite loop here by limiting the
# depth.
depth = 0
dentry = path.dentry
vfsmnt = path.mnt
mnt = self._real_mount(vfsmnt)
slash = False
result = FileName(start_dentry=dentry)
# Check for deleted dentry.
if dentry.d_flags.DCACHE_UNHASHED and not dentry.is_root:
result.deleted = True
while dentry != root.dentry or vfsmnt != root.mnt:
# Control the depth.
depth += 1
if depth >= result.MAX_DEPTH:
break
if dentry == vfsmnt.mnt_root or dentry.is_root:
# Global root?
if not self._mnt_has_parent(mnt):
if not slash:
result.PrependName("")
break
dentry = mnt.mnt_mountpoint
mnt = mnt.mnt_parent
vfsmnt = mnt.mnt
continue
parent = dentry.d_parent
if dentry.d_name.name:
result.PrependName(dentry.d_name.name.deref())
slash = True
dentry = parent
# When we get here dentry is a root dentry and mnt is the mount point it
# is mounted on. There are some special mount points we want to
# highlight.
result.mount_point = mnt.mnt_mountpoint.d_name.name.deref()
return result.FormatName(dentry)
def _prepend_path314(self, path, root):
"""Return the path of a dentry for 3.14 kernels.
http://lxr.free-electrons.com/source/fs/dcache.c?v=3.14#L2867
"""
# Ensure we can not get into an infinite loop here by limiting the
# depth.
depth = 0
dentry = path.dentry
vfsmnt = path.mnt
mnt = self._real_mount(vfsmnt)
result = FileName(start_dentry=dentry)
# Check for deleted dentry.
if dentry.d_flags.DCACHE_UNHASHED and not dentry.is_root:
result.deleted = True
while dentry != root.dentry or vfsmnt != root.mnt:
# Control the depth.
depth += 1
if depth >= result.MAX_DEPTH:
break
if dentry == vfsmnt.mnt_root or dentry.is_root:
parent = mnt.mnt_parent
# Global root?
if mnt != parent:
dentry = mnt.mnt_mountpoint
mnt = mnt.mnt_parent
vfsmnt = mnt.mnt
continue
parent = dentry.d_parent
if dentry.d_name.name:
result.PrependName(dentry.d_name.name.deref())
dentry = parent
# When we get here dentry is a root dentry and mnt is the mount point it
# is mounted on. There are some special mount points we want to
# highlight.
result.mount_point = mnt.mnt_mountpoint.d_name.name.deref()
return result.FormatName(dentry)
class Linux26VFS(Linux3VFS):
"""This is the implementation specific VFS operations.
Most of the code here is a direct copy of the methods in linux/fs/dcache.c
http://lxr.free-electrons.com/source/fs/dcache.c?v=2.6.26#L1782
"""
def get_path(self, task, filp):
"""Resolve the dentry, vfsmount relative to this task's chroot.
Returns:
An absolute path to the global filesystem mount. (I.e. we do not
truncate the path at the chroot point as the kernel does).
"""
root = task.fs.root.deref()
# For very old kernels (<=2.6.24) the root member is a dentry not a
# struct path, so we need to synthesize one.
if root.obj_type == "dentry":
root = task.obj_profile.path()
root.dentry = task.fs.root
root.mnt = task.fs.rootmnt
return self.__d_path(filp.f_path, root)
def d_unhashed(self, dentry):
return dentry.d_flags.DCACHE_UNHASHED
def __d_path(self, path, root):
"""A literal copy of the __d_path function from kernel 2.6.26."""
depth = 0
dentry = path.dentry
if dentry == None:
return ""
vfsmnt = path.mnt
result = FileName(start_dentry=dentry)
if not dentry.is_root and self.d_unhashed(dentry):
result.deleted = True
# Limit the recursion here to avoid getting stuck.
while depth < result.MAX_DEPTH:
if dentry == root.dentry and vfsmnt == root.mnt:
break
if dentry == vfsmnt.mnt_root or dentry.is_root:
if vfsmnt.mnt_parent == vfsmnt:
break
dentry = vfsmnt.mnt_mountpoint
vfsmnt = vfsmnt.mnt_parent
continue
parent = dentry.d_parent
result.PrependName(dentry.d_name.name.deref())
dentry = parent
# When we get here dentry is a root dentry and mnt is the mount point it
# is mounted on. There are some special mount points we want to
# highlight.
result.mount_point = utils.SmartUnicode(
vfsmnt.mnt_mountpoint.d_name.name.deref())
return result.FormatName(dentry)
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