Mini Shell
# Copyright 2014-2015, Tresys Technology, LLC
#
# This file is part of SETools.
#
# SETools is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as
# published by the Free Software Foundation, either version 2.1 of
# the License, or (at your option) any later version.
#
# SETools 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with SETools. If not, see
# <http://www.gnu.org/licenses/>.
#
import sys
import logging
import copy
from collections import OrderedDict
from errno import ENOENT
from contextlib import suppress
import pkg_resources
from . import exception
from . import policyrep
from .descriptors import PermissionMapDescriptor
from .policyrep import TERuletype
infoflow_directions = ["r", "w", "b", "n", "u"]
min_weight = 1
max_weight = 10
class PermissionMap:
"""Permission Map for information flow analysis."""
def __init__(self, permmapfile=None):
"""
Parameter:
permmapfile The path to the permission map to load.
"""
self.log = logging.getLogger(__name__)
self.permmap = OrderedDict()
self.permmapfile = None
if permmapfile:
self.load(permmapfile)
else:
distro = pkg_resources.get_distribution("setools")
# pylint: disable=no-member
path = "{0}/setools/perm_map".format(distro.location)
self.load(path)
def __str__(self):
return self.permmapfile
def __deepcopy__(self, memo):
newobj = PermissionMap.__new__(PermissionMap)
newobj.log = self.log
newobj.permmap = copy.deepcopy(self.permmap)
newobj.permmapfile = self.permmapfile
memo[id(self)] = newobj
return newobj
def __iter__(self):
for cls in self.classes():
for mapping in self.perms(cls):
yield mapping
def load(self, permmapfile):
"""
Parameter:
permmapfile The path to the permission map to load.
"""
self.log.info("Opening permission map \"{0}\"".format(permmapfile))
# state machine
# 1 = read number of classes
# 2 = read class name and number of perms
# 3 = read perms
with open(permmapfile, "r") as mapfile:
total_perms = 0
class_count = 0
num_classes = 0
state = 1
self.permmap.clear()
for line_num, line in enumerate(mapfile, start=1):
entry = line.split()
if len(entry) == 0 or entry[0][0] == '#':
continue
if state == 1:
try:
num_classes = int(entry[0])
except ValueError as ex:
raise exception.PermissionMapParseError(
"{0}:{1}:Invalid number of classes: {2}".
format(permmapfile, line_num, entry[0])) from ex
if num_classes < 1:
raise exception.PermissionMapParseError(
"{0}:{1}:Number of classes must be positive: {2}".
format(permmapfile, line_num, entry[0]))
state = 2
elif state == 2:
if len(entry) != 3 or entry[0] != "class":
raise exception.PermissionMapParseError(
"{0}:{1}:Invalid class declaration: {2}".
format(permmapfile, line_num, entry))
class_name = str(entry[1])
try:
num_perms = int(entry[2])
except ValueError as ex:
raise exception.PermissionMapParseError(
"{0}:{1}:Invalid number of permissions: {2}".
format(permmapfile, line_num, entry[2])) from ex
if num_perms < 1:
raise exception.PermissionMapParseError(
"{0}:{1}:Number of permissions must be positive: {2}".
format(permmapfile, line_num, entry[2]))
class_count += 1
if class_count > num_classes:
raise exception.PermissionMapParseError(
"{0}:{1}:Extra class found: {2}".
format(permmapfile, line_num, class_name))
self.permmap[class_name] = OrderedDict()
perm_count = 0
state = 3
elif state == 3:
perm_name = str(entry[0])
flow_direction = str(entry[1])
if flow_direction not in infoflow_directions:
raise exception.PermissionMapParseError(
"{0}:{1}:Invalid information flow direction: {2}".
format(permmapfile, line_num, entry[1]))
try:
weight = int(entry[2])
except ValueError as ex:
raise exception.PermissionMapParseError(
"{0}:{1}:Invalid permission weight: {2}".
format(permmapfile, line_num, entry[2])) from ex
if not min_weight <= weight <= max_weight:
raise exception.PermissionMapParseError(
"{0}:{1}:Permission weight must be {3}-{4}: {2}".
format(permmapfile, line_num, entry[2],
min_weight, max_weight))
self.log.debug("Read {0}:{1} {2} {3}".format(
class_name, perm_name, flow_direction, weight))
if flow_direction == 'u':
self.log.info("Permission {0}:{1} is unmapped.".format(
class_name, perm_name))
mapping = Mapping(self.permmap, class_name, perm_name, create=True)
mapping.direction = flow_direction
mapping.weight = weight
total_perms += 1
perm_count += 1
if perm_count >= num_perms:
state = 2
self.permmapfile = permmapfile
self.log.info("Successfully opened permission map \"{0}\"".format(permmapfile))
self.log.debug("Read {0} classes and {1} total permissions.".format(
class_count, total_perms))
def save(self, permmapfile):
"""
Save the permission map to the specified path. Existing files
will be overwritten.
Parameter:
permmapfile The path to write the permission map.
"""
with open(permmapfile, "w") as mapfile:
self.log.info("Writing permission map to \"{0}\"".format(permmapfile))
mapfile.write("{0}\n\n".format(len(self.permmap)))
for classname, perms in self.permmap.items():
mapfile.write("class {0} {1}\n".format(classname, len(perms)))
for permname, settings in perms.items():
direction = settings['direction']
weight = settings['weight']
assert min_weight <= weight <= max_weight, \
"{0}:{1} weight is out of range ({2}). This is an SETools bug.".format(
classname, permname, weight)
assert direction in infoflow_directions, \
"{0}:{1} flow direction ({2}) is invalid. This is an SETools bug.".format(
classname, permname, direction)
if direction == 'u':
self.log.warning("Warning: permission {0} in class {1} is unmapped.".format(
permname, classname))
mapfile.write("{0:>20} {1:>9} {2:>9}\n".format(permname, direction, weight))
mapfile.write("\n")
self.log.info("Successfully wrote permission map to \"{0}\"".format(permmapfile))
def classes(self):
"""
Generate class names in the permission map.
Yield:
class An object class name.
"""
yield from self.permmap.keys()
def perms(self, class_):
"""
Generate permission mappings for the specified class.
Parameter:
class_ An object class name.
Yield:
Mapping A permission's complete map (weight, direction, enabled)
"""
try:
for perm in self.permmap[class_].keys():
yield Mapping(self.permmap, class_, perm)
except KeyError as ex:
raise exception.UnmappedClass("{0} is not mapped.".format(class_)) from ex
def mapping(self, class_, perm):
"""Retrieve a specific permission's mapping."""
return Mapping(self.permmap, class_, perm)
def exclude_class(self, class_):
"""
Exclude all permissions in an object class for calculating rule weights.
Parameter:
class_ The object class to exclude.
Exceptions:
UnmappedClass The specified object class is not mapped.
"""
for perm in self.perms(class_):
perm.enabled = False
def exclude_permission(self, class_, permission):
"""
Exclude a permission for calculating rule weights.
Parameter:
class_ The object class of the permission.
permission The permission name to exclude.
Exceptions:
UnmappedClass The specified object class is not mapped.
UnmappedPermission The specified permission is not mapped for the object class.
"""
Mapping(self.permmap, class_, permission).enabled = False
def include_class(self, class_):
"""
Include all permissions in an object class for calculating rule weights.
Parameter:
class_ The object class to include.
Exceptions:
UnmappedClass The specified object class is not mapped.
"""
for perm in self.perms(class_):
perm.enabled = True
def include_permission(self, class_, permission):
"""
Include a permission for calculating rule weights.
Parameter:
class_ The object class of the permission.
permission The permission name to include.
Exceptions:
UnmappedClass The specified object class is not mapped.
UnmappedPermission The specified permission is not mapped for the object class.
"""
Mapping(self.permmap, class_, permission).enabled = True
def map_policy(self, policy):
"""Create mappings for all classes and permissions in the specified policy."""
for class_ in policy.classes():
class_name = str(class_)
if class_name not in self.permmap:
self.log.debug("Adding unmapped class {0} from {1}".format(class_name, policy))
self.permmap[class_name] = OrderedDict()
perms = class_.perms
with suppress(exception.NoCommon):
perms |= class_.common.perms
for perm_name in perms:
if perm_name not in self.permmap[class_name]:
self.log.debug("Adding unmapped permission {0} in {1} from {2}".
format(perm_name, class_name, policy))
Mapping(self.permmap, class_name, perm_name, create=True)
def rule_weight(self, rule):
"""
Get the type enforcement rule's information flow read and write weights.
Parameter:
rule A type enforcement rule.
Return: Tuple(read_weight, write_weight)
read_weight The type enforcement rule's read weight.
write_weight The type enforcement rule's write weight.
"""
write_weight = 0
read_weight = 0
class_name = str(rule.tclass)
if rule.ruletype != TERuletype.allow:
raise exception.RuleTypeError("{0} rules cannot be used for calculating a weight".
format(rule.ruletype))
# iterate over the permissions and determine the
# weight of the rule in each direction. The result
# is the largest-weight permission in each direction
for perm_name in rule.perms:
mapping = Mapping(self.permmap, class_name, perm_name)
if not mapping.enabled:
continue
if mapping.direction == "r":
read_weight = max(read_weight, mapping.weight)
elif mapping.direction == "w":
write_weight = max(write_weight, mapping.weight)
elif mapping.direction == "b":
read_weight = max(read_weight, mapping.weight)
write_weight = max(write_weight, mapping.weight)
return (read_weight, write_weight)
def set_direction(self, class_, permission, direction):
"""
Set the information flow direction of a permission.
Parameter:
class_ The object class of the permission.
permission The permission name.
direction The information flow direction the permission (r/w/b/n).
Exceptions:
UnmappedClass The specified object class is not mapped.
UnmappedPermission The specified permission is not mapped for the object class.
"""
Mapping(self.permmap, class_, permission).direction = direction
def set_weight(self, class_, permission, weight):
"""
Set the weight of a permission.
Parameter:
class_ The object class of the permission.
permission The permission name.
weight The weight of the permission (1-10).
Exceptions:
UnmappedClass The specified object class is not mapped.
UnmappedPermission The specified permission is not mapped for the object class.
"""
Mapping(self.permmap, class_, permission).weight = weight
#
# Settings Validation Functions
#
def validate_weight(weight):
if not min_weight <= weight <= max_weight:
raise ValueError("Permission weights must be 1-10: {0}".format(weight))
return weight
def validate_direction(direction):
if direction not in infoflow_directions:
raise ValueError("Invalid information flow direction: {0}".format(direction))
return direction
def validate_enabled(enabled):
return bool(enabled)
class Mapping:
"""A mapping for a permission in the permission map."""
weight = PermissionMapDescriptor("weight", validate_weight)
direction = PermissionMapDescriptor("direction", validate_direction)
enabled = PermissionMapDescriptor("enabled", validate_enabled)
def __init__(self, perm_map, classname, permission, create=False):
self.perm_map = perm_map
self.class_ = classname
self.perm = permission
if create:
if classname not in self.perm_map:
self.perm_map[classname] = OrderedDict()
self.perm_map[classname][permission] = {'direction': 'u',
'weight': 1,
'enabled': True}
else:
if classname not in self.perm_map:
raise exception.UnmappedClass("{0} is not mapped.".format(classname))
if permission not in self.perm_map[classname]:
raise exception.UnmappedPermission("{0}:{1} is not mapped.".
format(classname, permission))
def __lt__(self, other):
if self.class_ == other.class_:
return self.perm < other.perm
else:
return self.class_ < other.class_
Zerion Mini Shell 1.0