/usr/lib/python3/dist-packages/setools/policyrep/constraint.py is in python3-setools 4.0.1-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# 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/>.
#
from . import qpol
from .exception import ConstraintUseError, InvalidConstraintType
from .role import role_factory
from .symbol import PolicySymbol
from .objclass import class_factory
from .typeattr import type_or_attr_factory
from .user import user_factory
def _is_mls(policy, sym):
"""Determine if this is a regular or MLS constraint/validatetrans."""
# this can only be determined by inspecting the expression.
for expr_node in sym.expr_iter(policy):
sym_type = expr_node.sym_type(policy)
expr_type = expr_node.expr_type(policy)
if expr_type == qpol.QPOL_CEXPR_TYPE_ATTR and sym_type >= qpol.QPOL_CEXPR_SYM_L1L2:
return True
return False
def validate_ruletype(t):
"""Validate constraint rule types."""
if t not in ["constrain", "mlsconstrain", "validatetrans", "mlsvalidatetrans"]:
raise InvalidConstraintType("{0} is not a valid constraint type.".format(t))
return t
def constraint_factory(policy, sym):
"""Factory function for creating constraint objects."""
try:
if _is_mls(policy, sym):
if isinstance(sym, qpol.qpol_constraint_t):
return Constraint(policy, sym, "mlsconstrain")
else:
return Validatetrans(policy, sym, "mlsvalidatetrans")
else:
if isinstance(sym, qpol.qpol_constraint_t):
return Constraint(policy, sym, "constrain")
else:
return Validatetrans(policy, sym, "validatetrans")
except AttributeError:
raise TypeError("Constraints cannot be looked-up.")
class BaseConstraint(PolicySymbol):
"""Base class for constraint rules."""
_role_syms = [qpol.QPOL_CEXPR_SYM_ROLE,
qpol.QPOL_CEXPR_SYM_ROLE + qpol.QPOL_CEXPR_SYM_TARGET,
qpol.QPOL_CEXPR_SYM_ROLE + qpol.QPOL_CEXPR_SYM_XTARGET]
_type_syms = [qpol.QPOL_CEXPR_SYM_TYPE,
qpol.QPOL_CEXPR_SYM_TYPE + qpol.QPOL_CEXPR_SYM_TARGET,
qpol.QPOL_CEXPR_SYM_TYPE + qpol.QPOL_CEXPR_SYM_XTARGET]
_user_syms = [qpol.QPOL_CEXPR_SYM_USER,
qpol.QPOL_CEXPR_SYM_USER + qpol.QPOL_CEXPR_SYM_TARGET,
qpol.QPOL_CEXPR_SYM_USER + qpol.QPOL_CEXPR_SYM_XTARGET]
def __init__(self, policy, qpol_symbol, ruletype):
PolicySymbol.__init__(self, policy, qpol_symbol)
self.ruletype = ruletype
def __str__(self):
raise NotImplementedError
# There is no levels function as specific
# levels cannot be used in expressions, only
# the l1, h1, etc. symbols
@property
def roles(self):
"""The roles used in the expression."""
return set(self._get_symbols(self._role_syms, role_factory))
@property
def perms(self):
raise NotImplementedError
def statement(self):
return str(self)
@property
def tclass(self):
"""Object class for this constraint."""
return class_factory(self.policy, self.qpol_symbol.object_class(self.policy))
@property
def types(self):
"""The types and type attributes used in the expression."""
return set(self._get_symbols(self._type_syms, type_or_attr_factory))
@property
def users(self):
"""The users used in the expression."""
return set(self._get_symbols(self._user_syms, user_factory))
def expression(self):
"""
The constraint's expression in infix notation.
Return: list
"""
_precedence = {
"not": 4,
"and": 2,
"or": 1,
"==": 3,
"!=": 3,
"dom": 3,
"domby": 3,
"incomp": 3}
_max_precedence = 4
_operands = ["u1", "u2", "u3",
"r1", "r2", "r3",
"t1", "t2", "t3",
"l1", "l2",
"h1", "h2"]
# qpol representation is in postfix notation. This code
# converts it to infix notation. Parentheses are added
# to ensure correct expressions, though they may end up
# being overused. Set previous operator at start to the
# highest precedence (op) so if there is a single binary
# operator, no parentheses are output
stack = []
prev_op_precedence = _max_precedence
for op in self.postfix_expression():
if isinstance(op, frozenset) or op in _operands:
# operands
stack.append(op)
else:
# operators
if op == "not":
# unary operator
operator = op
operand = stack.pop()
op_precedence = _precedence[op]
stack.append([operator, "(", operand, ")"])
else:
# binary operators
operand2 = stack.pop()
operand1 = stack.pop()
operator = op
# if previous operator is of higher precedence
# no parentheses are needed.
if _precedence[op] < prev_op_precedence:
stack.append([operand1, operator, operand2])
else:
stack.append(["(", operand1, operator, operand2, ")"])
prev_op_precedence = _precedence[op]
return self._flatten_expression(stack)
def postfix_expression(self):
"""
The constraint's expression in postfix notation.
Return: list
"""
_expr_type_to_text = {
qpol.QPOL_CEXPR_TYPE_NOT: "not",
qpol.QPOL_CEXPR_TYPE_AND: "and",
qpol.QPOL_CEXPR_TYPE_OR: "or"}
_expr_op_to_text = {
qpol.QPOL_CEXPR_OP_EQ: "==",
qpol.QPOL_CEXPR_OP_NEQ: "!=",
qpol.QPOL_CEXPR_OP_DOM: "dom",
qpol.QPOL_CEXPR_OP_DOMBY: "domby",
qpol.QPOL_CEXPR_OP_INCOMP: "incomp"}
_sym_to_text = {
qpol.QPOL_CEXPR_SYM_USER: "u1",
qpol.QPOL_CEXPR_SYM_ROLE: "r1",
qpol.QPOL_CEXPR_SYM_TYPE: "t1",
qpol.QPOL_CEXPR_SYM_USER + qpol.QPOL_CEXPR_SYM_TARGET: "u2",
qpol.QPOL_CEXPR_SYM_ROLE + qpol.QPOL_CEXPR_SYM_TARGET: "r2",
qpol.QPOL_CEXPR_SYM_TYPE + qpol.QPOL_CEXPR_SYM_TARGET: "t2",
qpol.QPOL_CEXPR_SYM_USER + qpol.QPOL_CEXPR_SYM_XTARGET: "u3",
qpol.QPOL_CEXPR_SYM_ROLE + qpol.QPOL_CEXPR_SYM_XTARGET: "r3",
qpol.QPOL_CEXPR_SYM_TYPE + qpol.QPOL_CEXPR_SYM_XTARGET: "t3",
qpol.QPOL_CEXPR_SYM_L1L2: "l1",
qpol.QPOL_CEXPR_SYM_L1H2: "l1",
qpol.QPOL_CEXPR_SYM_H1L2: "h1",
qpol.QPOL_CEXPR_SYM_H1H2: "h1",
qpol.QPOL_CEXPR_SYM_L1H1: "l1",
qpol.QPOL_CEXPR_SYM_L2H2: "l2",
qpol.QPOL_CEXPR_SYM_L1L2 + qpol.QPOL_CEXPR_SYM_TARGET: "l2",
qpol.QPOL_CEXPR_SYM_L1H2 + qpol.QPOL_CEXPR_SYM_TARGET: "h2",
qpol.QPOL_CEXPR_SYM_H1L2 + qpol.QPOL_CEXPR_SYM_TARGET: "l2",
qpol.QPOL_CEXPR_SYM_H1H2 + qpol.QPOL_CEXPR_SYM_TARGET: "h2",
qpol.QPOL_CEXPR_SYM_L1H1 + qpol.QPOL_CEXPR_SYM_TARGET: "h1",
qpol.QPOL_CEXPR_SYM_L2H2 + qpol.QPOL_CEXPR_SYM_TARGET: "h2"}
expression = []
for expr_node in self.qpol_symbol.expr_iter(self.policy):
op = expr_node.op(self.policy)
sym_type = expr_node.sym_type(self.policy)
expr_type = expr_node.expr_type(self.policy)
if expr_type == qpol.QPOL_CEXPR_TYPE_ATTR:
# logical operator with symbols (e.g. u1 == u2)
operand1 = _sym_to_text[sym_type]
operand2 = _sym_to_text[sym_type + qpol.QPOL_CEXPR_SYM_TARGET]
operator = _expr_op_to_text[op]
expression.extend([operand1, operand2, operator])
elif expr_type == qpol.QPOL_CEXPR_TYPE_NAMES:
# logical operator with type or attribute list (e.g. t1 == { spam_t eggs_t })
operand1 = _sym_to_text[sym_type]
operator = _expr_op_to_text[op]
names = list(expr_node.names_iter(self.policy))
if sym_type in self._role_syms:
operand2 = frozenset(role_factory(self.policy, n) for n in names)
elif sym_type in self._type_syms:
operand2 = frozenset(type_or_attr_factory(self.policy, n) for n in names)
else:
operand2 = frozenset(user_factory(self.policy, n) for n in names)
expression.extend([operand1, operand2, operator])
else:
# individual operators (and/or/not)
expression.append(_expr_type_to_text[expr_type])
return expression
#
# Internal functions
#
def _flatten_expression(self, expr):
"""Flatten the expression into a flat list."""
ret = []
for i in expr:
if isinstance(i, list):
ret.extend(self._flatten_expression(i))
else:
ret.append(i)
return ret
def _get_symbols(self, syms, factory):
"""
Internal generator for getting users/roles/types in a constraint
expression. Symbols will be yielded multiple times if they appear
in the expression multiple times.
Parameters:
syms List of qpol symbol types.
factory The factory function related to these symbols.
"""
for expr_node in self.qpol_symbol.expr_iter(self.policy):
sym_type = expr_node.sym_type(self.policy)
expr_type = expr_node.expr_type(self.policy)
if expr_type == qpol.QPOL_CEXPR_TYPE_NAMES and sym_type in syms:
for s in expr_node.names_iter(self.policy):
yield factory(self.policy, s)
@staticmethod
def _expression_str(expr):
"""Generate the string representation of the expression."""
ret = []
for item in expr:
if isinstance(item, frozenset):
if len(item) > 1:
ret.append("{{ {0} }} ".format(" ".join(str(j) for j in item)))
else:
ret.append("{0}".format(" ".join(str(j) for j in item)))
else:
ret.append(item)
return " ".join(ret)
class Constraint(BaseConstraint):
"""A constraint rule (constrain/mlsconstrain)."""
def __str__(self):
rule_string = "{0.ruletype} {0.tclass} ".format(self)
perms = self.perms
if len(perms) > 1:
rule_string += "{{ {0} }} (".format(' '.join(perms))
else:
# convert to list since sets cannot be indexed
rule_string += "{0} (".format(list(perms)[0])
rule_string += "{0});".format(self._expression_str(self.expression()))
return rule_string
@property
def perms(self):
"""The constraint's permission set."""
return set(self.qpol_symbol.perm_iter(self.policy))
class Validatetrans(BaseConstraint):
"""A validatetrans rule (validatetrans/mlsvalidatetrans)."""
def __str__(self):
return "{0.ruletype} {0.tclass} ({1});".format(self,
self._expression_str(self.expression()))
@property
def perms(self):
raise ConstraintUseError("{0} rules do not have permissions.".format(self.ruletype))
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