/usr/lib/python2.7/dist-packages/rekall/cache.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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import cStringIO
import os
import time
from rekall import config
from rekall import io_manager
from rekall import obj
from rekall import utils
from rekall.ui import json_renderer
config.DeclareOption(
"--cache", default="file", type="String",
choices=["file", "memory", "timed"],
help="Type of cache to use. ")
class PicklingDirectoryIOManager(io_manager.DirectoryIOManager):
def __init__(self, *args, **kwargs):
super(PicklingDirectoryIOManager, self).__init__(*args, **kwargs)
self.renderer = json_renderer.JsonRenderer(session=self.session)
def Encoder(self, data, **_):
data = self.renderer.encoder.Encode(data)
try:
return cPickle.dumps(data, -1)
except TypeError:
raise io_manager.EncodeError("Unable to pickle data")
def Decoder(self, raw):
"""Safe Unpickling.
Unpickle only safe primitives like tuples, dicts and
strings. Specifically does not allow arbitrary instances to be
recovered.
"""
now = time.time()
unpickler = cPickle.Unpickler(cStringIO.StringIO(raw))
unpickler.find_global = None
try:
decoded = unpickler.load()
except Exception:
raise io_manager.DecodeError("Unable to unpickle cached object")
result = self.renderer.decoder.Decode(decoded)
self.session.logging.debug("Decoded in %s sec.", time.time() - now)
return result
class Cache(object):
def __init__(self, session):
self.data = {}
self.session = session
if session == None:
raise RuntimeError("Session must be set")
def Get(self, item, default=None):
return self.data.get(item, default)
def Set(self, item, value, volatile=True):
_ = volatile
if value is None:
self.data.pop(item, None)
else:
self.data[item] = value
def Clear(self):
self.data.clear()
def Flush(self):
"""Called to sync the cache to external storage if required."""
def __str__(self):
"""Print the contents somewhat concisely."""
result = []
for k, v in self.data.iteritems():
if isinstance(v, obj.BaseObject):
v = repr(v)
value = "\n ".join(str(v).splitlines())
if len(value) > 100:
value = "%s ..." % value[:100]
result.append(" %s = %s" % (k, value))
return "{\n" + "\n".join(sorted(result)) + "\n}"
class TimedCache(Cache):
"""A limited time Cache.
This is useful for live analysis to ensure that information is not stale.
"""
@utils.safe_property
def expire_time(self):
# Change this via the session.SetParameter("cache_expiry_time", XXX)
return self.data.get("cache_expiry_time", 600)
def Get(self, item, default=None):
now = time.time()
data, timestamp = self.data.get(item, (default, now))
if timestamp + self.expire_time < now:
del self.data[item]
return default
return data
def Set(self, item, value, volatile=True):
"""Sets the item to the value.
The value will be cached for the expiry time if it is volatile (by
default). Non-volatile data will never expire.
Even on a live system, we cache information which can not change for the
life of the system (e.g. the profile or dtb values). These are marked
non-volatile and will not be expired.
"""
if value is None:
self.data.pop(item, None)
else:
if volatile:
now = time.time()
else:
now = 2**63
self.data[item] = (value, now)
def __str__(self):
"""Print the contents somewhat concisely."""
result = []
now = time.time()
for k, (v, timestamp) in self.data.items():
if timestamp + self.expire_time < now:
self.data.pop(k)
continue
if isinstance(v, obj.BaseObject):
v = repr(v)
value = "\n ".join(str(v).splitlines())
if len(value) > 1000:
value = "%s ..." % value[:1000]
result.append(" %s = %s" % (k, value))
return "{\n" + "\n".join(sorted(result)) + "\n}"
class FileCache(Cache):
"""A cache which syncs to a persistent on disk representation.
"""
def __init__(self, session):
super(FileCache, self).__init__(session)
self._io_manager = None
self.fingerprint = None
self.name = None
# Record all the dirty cached keys.
self.dirty = set()
self.cache_dir = None
self.enabled = True
# Make sure we get flushed when the session is closed.
self.session.register_flush_hook(self, self.Flush)
@utils.safe_property
def io_manager(self):
if not self.enabled:
return
cache_dir = os.path.expandvars(
self.session.GetParameter("cache_dir", cached=False))
cache_dir = os.path.join(config.GetHomeDir(self.session), cache_dir)
# Force the IO manager to be recreated if the cache dir has
# changed. This allows the session to change it's cache directory on the
# fly (which is actually done when setting it from the command line).
if cache_dir != self.cache_dir:
self._io_manager = None
self.cache_dir = cache_dir
if self._io_manager is None and cache_dir:
# Cache dir may be specified relative to the home directory.
if os.access(cache_dir, os.F_OK | os.R_OK | os.W_OK | os.X_OK):
self._io_manager = PicklingDirectoryIOManager(
"%s/sessions" % cache_dir, session=self.session,
mode="w")
self.cache_dir = cache_dir
else:
self.session.logging.warn(
"Cache directory inaccessible. Disabling.")
self.enabled = False
return self._io_manager
def SetName(self, name):
self.name = name
def SetFingerprint(self, fingerprint):
name = fingerprint["hash"]
if self.name != name and self.io_manager:
indexes = self.io_manager.GetData("sessions/index") or {}
indexes[name] = fingerprint["tests"]
self.name = name
self.io_manager.StoreData("sessions/index", indexes)
def Get(self, item, default=None):
if (self.io_manager and # We are backing to a file.
item not in self.data and # Item not already cached in memory.
item not in self.dirty): # Item was not previously changed.
try:
data = self.io_manager.GetData(
"sessions/%s/%s" % (self.name, item),
default=self)
if data is not self:
self.data[item] = data
except Exception:
self.session.logging.error(
"Unable to decode cached object %s", item)
return super(FileCache, self).Get(item, default=default)
def Set(self, item, value, volatile=True):
super(FileCache, self).Set(item, value, volatile=volatile)
self.dirty.add(item)
def Clear(self):
super(FileCache, self).Clear()
# Also delete the files backing this cache.
if self._io_manager:
self._io_manager.Destroy("sessions/%s" % self.name)
@utils.safe_property
def location(self):
return "%s/v1.0/sessions/%s" % (self._io_manager.location, self.name)
def Flush(self):
"""Write out all dirty items at once."""
if self.fingerprint is None and self.session.HasParameter("profile"):
self.SetFingerprint(self.session.GetParameter("image_fingerprint"))
if self.name and self.io_manager:
# Save to disk the dirty items.
for key, item in self.data.iteritems():
if key in self.dirty or getattr(item, "dirty", False):
now = time.time()
self.io_manager.StoreData(
"sessions/%s/%s" % (self.name, key), item)
self.session.logging.debug("Flushed %s in %s" % (
key, (time.time() - now)))
self.io_manager.FlushInventory()
self.data.clear()
self.dirty.clear()
def DetectImage(self, address_space):
if not self.io_manager:
return
session_index = self.io_manager.GetData("sessions/index")
for name, tests in session_index.iteritems():
item = SessionIndex(name, tests)
if item.Test(address_space):
self.SetName(item.name)
# Force current data to be flushed to disk so we do not lose it.
self.Flush()
return item.name
def __repr__(self):
if self._io_manager:
return "<FileCache @ %s>" % self.location
else:
return "<FileCache (unbacked)>"
class SessionIndex(object):
def __init__(self, name, tests):
self.name = name
self.test = tests
def Test(self, address_space):
for offset, expected in self.test:
expected = utils.SmartStr(expected)
if (offset and expected !=
address_space.read(offset, len(expected))):
return False
return True
def GetCacheDir(session):
"""Returns the path of a usable cache directory."""
cache_dir = os.path.expandvars(session.GetParameter("cache_dir"))
if not cache_dir:
raise io_manager.IOManagerError(
"Local profile cache is not configured - "
"add a cache_dir parameter to ~/.rekallrc.")
# Cache dir may be specified relative to the home directory.
cache_dir = os.path.join(config.GetHomeDir(session), cache_dir)
if not os.access(cache_dir, os.F_OK | os.R_OK | os.W_OK | os.X_OK):
try:
os.makedirs(cache_dir)
except (IOError, OSError):
raise io_manager.IOManagerError(
"Unable to create or access cache directory %s" % cache_dir)
return cache_dir
def Factory(session, cache_type):
"""Instantiate the most appropriate cache for this session."""
if cache_type == "memory":
return Cache(session)
if cache_type == "timed":
return TimedCache(session)
if cache_type == "file":
return FileCache(session)
return Cache(session)
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