1 # -*- coding: utf-8 -*-
2 ##############################################################################
3 # Copyright (C) 2004-2012 OpenERP s.a. (<http://www.openerp.com>).
5 # This program is free software: you can redistribute it and/or modify
6 # it under the terms of the GNU Affero General Public License as
7 # published by the Free Software Foundation, either version 3 of the
8 # License, or (at your option) any later version.
10 # This program is distributed in the hope that it will be useful,
11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 # GNU Affero General Public License for more details.
15 # You should have received a copy of the GNU Affero General Public License
16 # along with this program. If not, see <http://www.gnu.org/licenses/>.
18 ##############################################################################
21 safe_eval module - methods intended to provide more restricted alternatives to
22 evaluate simple and/or untrusted code.
24 Methods in this module are typically used as alternatives to eval() to parse
25 OpenERP domain strings, conditions and expressions, mostly based on locals
26 condition/math builtins.
29 # Module partially ripped from/inspired by several different sources:
30 # - http://code.activestate.com/recipes/286134/
31 # - safe_eval in lp:~xrg/openobject-server/optimize-5.0
32 # - safe_eval in tryton http://hg.tryton.org/hgwebdir.cgi/trytond/rev/bbb5f73319ad
34 from opcode import HAVE_ARGUMENT, opmap, opname
35 from types import CodeType
38 __all__ = ['test_expr', 'safe_eval', 'const_eval']
40 # The time module is usually already provided in the safe_eval environment
41 # but some code, e.g. datetime.datetime.now() (Windows/Python 2.5.2, bug
42 # lp:703841), does import time.
43 _ALLOWED_MODULES = ['_strptime', 'time']
45 _CONST_OPCODES = set(opmap[x] for x in [
46 'POP_TOP', 'ROT_TWO', 'ROT_THREE', 'ROT_FOUR', 'DUP_TOP', 'DUP_TOPX',
47 'POP_BLOCK','SETUP_LOOP', 'BUILD_LIST', 'BUILD_MAP', 'BUILD_TUPLE',
48 'LOAD_CONST', 'RETURN_VALUE', 'STORE_SUBSCR', 'STORE_MAP'] if x in opmap)
50 _EXPR_OPCODES = _CONST_OPCODES.union(set(opmap[x] for x in [
51 'UNARY_POSITIVE', 'UNARY_NEGATIVE', 'UNARY_NOT',
52 'UNARY_INVERT', 'BINARY_POWER', 'BINARY_MULTIPLY',
53 'BINARY_DIVIDE', 'BINARY_FLOOR_DIVIDE', 'BINARY_TRUE_DIVIDE',
54 'BINARY_MODULO', 'BINARY_ADD', 'BINARY_SUBTRACT', 'BINARY_SUBSCR',
55 'BINARY_LSHIFT', 'BINARY_RSHIFT', 'BINARY_AND', 'BINARY_XOR',
56 'BINARY_OR', 'INPLACE_ADD', 'INPLACE_SUBTRACT', 'INPLACE_MULTIPLY',
57 'INPLACE_DIVIDE', 'INPLACE_REMAINDER', 'INPLACE_POWER',
58 'INPLACE_LEFTSHIFT', 'INPLACE_RIGHTSHIFT', 'INPLACE_AND',
59 'INPLACE_XOR','INPLACE_OR'
62 _SAFE_OPCODES = _EXPR_OPCODES.union(set(opmap[x] for x in [
63 'LOAD_NAME', 'CALL_FUNCTION', 'COMPARE_OP', 'LOAD_ATTR',
64 'STORE_NAME', 'GET_ITER', 'FOR_ITER', 'LIST_APPEND', 'DELETE_NAME',
65 'JUMP_FORWARD', 'JUMP_IF_TRUE', 'JUMP_IF_FALSE', 'JUMP_ABSOLUTE',
66 'MAKE_FUNCTION', 'SLICE+0', 'SLICE+1', 'SLICE+2', 'SLICE+3',
67 # New in Python 2.7 - http://bugs.python.org/issue4715 :
68 'JUMP_IF_FALSE_OR_POP', 'JUMP_IF_TRUE_OR_POP', 'POP_JUMP_IF_FALSE',
69 'POP_JUMP_IF_TRUE', 'SETUP_EXCEPT', 'END_FINALLY'
72 _logger = logging.getLogger(__name__)
74 def _get_opcodes(codeobj):
75 """_get_opcodes(codeobj) -> [opcodes]
77 Extract the actual opcodes as a list from a code object
79 >>> c = compile("[1 + 2, (1,2)]", "", "eval")
81 [100, 100, 23, 100, 100, 102, 103, 83]
85 byte_codes = codeobj.co_code
86 while i < len(byte_codes):
87 code = ord(byte_codes[i])
89 if code >= HAVE_ARGUMENT:
95 def test_expr(expr, allowed_codes, mode="eval"):
96 """test_expr(expression, allowed_codes[, mode]) -> code_object
98 Test that the expression contains only the allowed opcodes.
99 If the expression is valid and contains only allowed codes,
100 return the compiled code object.
101 Otherwise raise a ValueError, a Syntax Error or TypeError accordingly.
105 # eval() does not like leading/trailing whitespace
107 code_obj = compile(expr, "", mode)
108 except (SyntaxError, TypeError):
109 _logger.debug('Invalid eval expression', exc_info=True)
112 _logger.debug('Disallowed or invalid eval expression', exc_info=True)
113 raise ValueError("%s is not a valid expression" % expr)
114 for code in _get_opcodes(code_obj):
115 if code not in allowed_codes:
116 raise ValueError("opcode %s not allowed (%r)" % (opname[code], expr))
120 def const_eval(expr):
121 """const_eval(expression) -> value
123 Safe Python constant evaluation
125 Evaluates a string that contains an expression describing
126 a Python constant. Strings that are not valid Python expressions
127 or that contain other code besides the constant raise ValueError.
131 >>> const_eval("[1,2, (3,4), {'foo':'bar'}]")
132 [1, 2, (3, 4), {'foo': 'bar'}]
133 >>> const_eval("1+2")
134 Traceback (most recent call last):
136 ValueError: opcode BINARY_ADD not allowed
138 c = test_expr(expr, _CONST_OPCODES)
142 """expr_eval(expression) -> value
144 Restricted Python expression evaluation
146 Evaluates a string that contains an expression that only
147 uses Python constants. This can be used to e.g. evaluate
148 a numerical expression from an untrusted source.
152 >>> expr_eval("[1,2]*2")
154 >>> expr_eval("__import__('sys').modules")
155 Traceback (most recent call last):
157 ValueError: opcode LOAD_NAME not allowed
159 c = test_expr(expr, _EXPR_OPCODES)
162 def _import(name, globals=None, locals=None, fromlist=None, level=-1):
169 if name in _ALLOWED_MODULES:
170 return __import__(name, globals, locals, level)
171 raise ImportError(name)
173 def safe_eval(expr, globals_dict=None, locals_dict=None, mode="eval", nocopy=False):
174 """safe_eval(expression[, globals[, locals[, mode[, nocopy]]]]) -> result
176 System-restricted Python expression evaluation
178 Evaluates a string that contains an expression that mostly
179 uses Python constants, arithmetic expressions and the
180 objects directly provided in context.
182 This can be used to e.g. evaluate
183 an OpenERP domain expression from an untrusted source.
185 Throws TypeError, SyntaxError or ValueError (not allowed) accordingly.
187 >>> safe_eval("__import__('sys').modules")
188 Traceback (most recent call last):
190 ValueError: opcode LOAD_NAME not allowed
193 if isinstance(expr, CodeType):
194 raise ValueError("safe_eval does not allow direct evaluation of code objects.")
196 if '__subclasses__' in expr:
197 raise ValueError('expression not allowed (__subclasses__)')
199 if globals_dict is None:
202 # prevent altering the globals/locals from within the sandbox
205 # isinstance() does not work below, we want *exactly* the dict class
206 if (globals_dict is not None and type(globals_dict) is not dict) \
207 or (locals_dict is not None and type(locals_dict) is not dict):
209 "Looks like you are trying to pass a dynamic environment, "
210 "you should probably pass nocopy=True to safe_eval().")
212 globals_dict = dict(globals_dict)
213 if locals_dict is not None:
214 locals_dict = dict(locals_dict)
218 '__import__': _import,
241 return eval(test_expr(expr, _SAFE_OPCODES, mode=mode), globals_dict, locals_dict)
243 _logger.exception('Cannot eval %r', expr)
246 # vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4: