safe_eval.py

# Part of Odoo. See LICENSE file for full copyright and licensing details.
# https://github.com/odoo/odoo/blob/16.0/odoo/tools/safe_eval.py

"""
safe_eval module - methods intended to provide more restricted alternatives to
                   evaluate simple and/or untrusted code.

Methods in this module are typically used as alternatives to eval() to parse
OpenERP domain strings, conditions and expressions, mostly based on locals
condition/math builtins.
"""

# Module partially ripped from/inspired by several different sources:
#  - http://code.activestate.com/recipes/286134/
#  - safe_eval in lp:~xrg/openobject-server/optimize-5.0
#  - safe_eval in tryton http://hg.tryton.org/hgwebdir.cgi/trytond/rev/bbb5f73319ad
import dis
import functools
import logging
import sys
import types
from types import CodeType

import werkzeug
from opcode import opmap, opname
from psycopg2 import OperationalError

import odoo
unsafe_eval = eval

__all__ = ["test_expr", "safe_eval", "const_eval"]

# The time module is usually already provided in the safe_eval environment
# but some code, e.g. datetime.datetime.now() (Windows/Python 2.5.2, bug
# lp:703841), does import time.
_ALLOWED_MODULES = ["_strptime", "math", "time"]

# Mock __import__ function, as called by cpython's import emulator `PyImport_Import` inside
# timemodule.c, _datetimemodule.c and others.
# This function does not actually need to do anything, its expected side-effect is to make the
# imported module available in `sys.modules`. The _ALLOWED_MODULES are imported below to make it so.
def _import(name, globals=None, locals=None, fromlist=None, level=-1):
    if name not in sys.modules:
        raise ImportError(
            f"module {name} should be imported before calling safe_eval()"
        )


for module in _ALLOWED_MODULES:
    __import__(module)


_UNSAFE_ATTRIBUTES = [
    # Frames
    "f_builtins",
    "f_code",
    "f_globals",
    "f_locals",
    # Python 2 functions
    "func_code",
    "func_globals",
    # Code object
    "co_code",
    "_co_code_adaptive",
    # Method resolution order,
    "mro",
    # Tracebacks
    "tb_frame",
    # Generators
    "gi_code",
    "gi_frame",
    "gi_yieldfrom",
    # Coroutines
    "cr_await",
    "cr_code",
    "cr_frame",
    # Coroutine generators
    "ag_await",
    "ag_code",
    "ag_frame",
]


def to_opcodes(opnames, _opmap=opmap):
    for x in opnames:
        if x in _opmap:
            yield _opmap[x]


# opcodes which absolutely positively must not be usable in safe_eval,
# explicitly subtracted from all sets of valid opcodes just in case
_BLACKLIST = set(
    to_opcodes(
        [
            # can't provide access to accessing arbitrary modules
            # 'IMPORT_STAR', 'IMPORT_NAME', 'IMPORT_FROM',
            # could allow replacing or updating core attributes on models & al, setitem
            # can be used to set field values
            "STORE_ATTR",
            "DELETE_ATTR",
            # no reason to allow this
            "STORE_GLOBAL",
            "DELETE_GLOBAL",
        ]
    )
)
# opcodes necessary to build literal values
_CONST_OPCODES = (
    set(
        to_opcodes(
            [
                # stack manipulations
                "POP_TOP",
                "ROT_TWO",
                "ROT_THREE",
                "ROT_FOUR",
                "DUP_TOP",
                "DUP_TOP_TWO",
                "LOAD_CONST",
                "RETURN_VALUE",  # return the result of the literal/expr evaluation
                # literal collections
                "BUILD_LIST",
                "BUILD_MAP",
                "BUILD_TUPLE",
                "BUILD_SET",
                # 3.6: literal map with constant keys https://bugs.python.org/issue27140
                "BUILD_CONST_KEY_MAP",
                "LIST_EXTEND",
                "SET_UPDATE",
                # 3.11 replace DUP_TOP, DUP_TOP_TWO, ROT_TWO, ROT_THREE, ROT_FOUR
                "COPY",
                "SWAP",
                # Added in 3.11 https://docs.python.org/3/whatsnew/3.11.html#new-opcodes
                "RESUME",
                # 3.12 https://docs.python.org/3/whatsnew/3.12.html#cpython-bytecode-changes
                "RETURN_CONST",
                # 3.13
                "TO_BOOL",
            ]
        )
    )
    - _BLACKLIST
)

# operations which are both binary and inplace, same order as in doc'
_operations = [
    "POWER",
    "MULTIPLY",  # 'MATRIX_MULTIPLY', # matrix operator (3.5+)
    "FLOOR_DIVIDE",
    "TRUE_DIVIDE",
    "MODULO",
    "ADD",
    "SUBTRACT",
    "LSHIFT",
    "RSHIFT",
    "AND",
    "XOR",
    "OR",
]
# operations on literal values
_EXPR_OPCODES = (
    _CONST_OPCODES.union(
        to_opcodes(
            [
                "UNARY_POSITIVE",
                "UNARY_NEGATIVE",
                "UNARY_NOT",
                "UNARY_INVERT",
                *("BINARY_" + op for op in _operations),
                "BINARY_SUBSCR",
                *("INPLACE_" + op for op in _operations),
                "BUILD_SLICE",
                # comprehensions
                "LIST_APPEND",
                "MAP_ADD",
                "SET_ADD",
                "COMPARE_OP",
                # specialised comparisons
                "IS_OP",
                "CONTAINS_OP",
                "DICT_MERGE",
                "DICT_UPDATE",
                # Basically used in any "generator literal"
                "GEN_START",  # added in 3.10 but already removed from 3.11.
                # Added in 3.11, replacing all BINARY_* and INPLACE_*
                "BINARY_OP",
                "BINARY_SLICE",
            ]
        )
    )
    - _BLACKLIST
)

_SAFE_OPCODES = (
    _EXPR_OPCODES.union(
        to_opcodes(
            [
                # MAGIC
                "IMPORT_STAR",
                "IMPORT_NAME",
                "IMPORT_FROM",
                # It's needed to make a function with *args
                "LIST_TO_TUPLE",
                "POP_BLOCK",
                "POP_EXCEPT",
                # note: removed in 3.8
                "SETUP_LOOP",
                "SETUP_EXCEPT",
                "BREAK_LOOP",
                "CONTINUE_LOOP",
                "EXTENDED_ARG",  # P3.6 for long jump offsets.
                "MAKE_FUNCTION",
                "CALL_FUNCTION",
                "CALL_FUNCTION_KW",
                "CALL_FUNCTION_EX",
                # Added in P3.7 https://bugs.python.org/issue26110
                "CALL_METHOD",
                "LOAD_METHOD",
                "GET_ITER",
                "FOR_ITER",
                "YIELD_VALUE",
                "JUMP_FORWARD",
                "JUMP_ABSOLUTE",
                "JUMP_BACKWARD",
                "JUMP_IF_FALSE_OR_POP",
                "JUMP_IF_TRUE_OR_POP",
                "POP_JUMP_IF_FALSE",
                "POP_JUMP_IF_TRUE",
                "SETUP_FINALLY",
                "END_FINALLY",
                # Added in 3.8 https://bugs.python.org/issue17611
                "BEGIN_FINALLY",
                "CALL_FINALLY",
                "POP_FINALLY",
                "RAISE_VARARGS",
                "LOAD_NAME",
                "STORE_NAME",
                "DELETE_NAME",
                "LOAD_ATTR",
                "LOAD_FAST",
                "STORE_FAST",
                "DELETE_FAST",
                "UNPACK_SEQUENCE",
                "STORE_SUBSCR",
                "LOAD_GLOBAL",
                "RERAISE",
                "JUMP_IF_NOT_EXC_MATCH",
                # Following opcodes were Added in 3.11
                # replacement of opcodes CALL_FUNCTION, CALL_FUNCTION_KW, CALL_METHOD
                "PUSH_NULL",
                "PRECALL",
                "CALL",
                "KW_NAMES",
                # replacement of POP_JUMP_IF_TRUE and POP_JUMP_IF_FALSE
                "POP_JUMP_FORWARD_IF_FALSE",
                "POP_JUMP_FORWARD_IF_TRUE",
                "POP_JUMP_BACKWARD_IF_FALSE",
                "POP_JUMP_BACKWARD_IF_TRUE",
                # special case of the previous for IS NONE / IS NOT NONE
                "POP_JUMP_FORWARD_IF_NONE",
                "POP_JUMP_BACKWARD_IF_NONE",
                "POP_JUMP_FORWARD_IF_NOT_NONE",
                "POP_JUMP_BACKWARD_IF_NOT_NONE",
                # replacement of JUMP_IF_NOT_EXC_MATCH
                "CHECK_EXC_MATCH",
                # new opcodes
                "RETURN_GENERATOR",
                "PUSH_EXC_INFO",
                "NOP",
                "FORMAT_VALUE",
                "BUILD_STRING",
                # 3.12 https://docs.python.org/3/whatsnew/3.12.html#cpython-bytecode-changes
                "END_FOR",
                "LOAD_FAST_AND_CLEAR",
                "LOAD_FAST_CHECK",
                "POP_JUMP_IF_NOT_NONE",
                "POP_JUMP_IF_NONE",
                "CALL_INTRINSIC_1",
                "STORE_SLICE",
                # 3.13
                "CALL_KW",
                "LOAD_FAST_LOAD_FAST",
                "STORE_FAST_STORE_FAST",
                "STORE_FAST_LOAD_FAST",
                "CONVERT_VALUE",
                "FORMAT_SIMPLE",
                "FORMAT_WITH_SPEC",
                "SET_FUNCTION_ATTRIBUTE",
            ]
        )
    )
    - _BLACKLIST
)

_logger = logging.getLogger(__name__)


def assert_no_dunder_name(code_obj, expr):
    """assert_no_dunder_name(code_obj, expr) -> None

    Asserts that the code object does not refer to any "dunder name"
    (__$name__), so that safe_eval prevents access to any internal-ish Python
    attribute or method (both are loaded via LOAD_ATTR which uses a name, not a
    const or a var).

    Checks that no such name exists in the provided code object (co_names).

    :param code_obj: code object to name-validate
    :type code_obj: CodeType
    :param str expr: expression corresponding to the code object, for debugging
                     purposes
    :raises NameError: in case a forbidden name (containing two underscores)
                       is found in ``code_obj``

    .. note:: actually forbids every name containing 2 underscores
    """
    for name in code_obj.co_names:
        if "__" in name or name in _UNSAFE_ATTRIBUTES:
            raise NameError("Access to forbidden name %r (%r)" % (name, expr))


def assert_valid_codeobj(allowed_codes, code_obj, expr):
    """Asserts that the provided code object validates against the bytecode
    and name constraints.

    Recursively validates the code objects stored in its co_consts in case
    lambdas are being created/used (lambdas generate their own separated code
    objects and don't live in the root one)

    :param allowed_codes: list of permissible bytecode instructions
    :type allowed_codes: set(int)
    :param code_obj: code object to name-validate
    :type code_obj: CodeType
    :param str expr: expression corresponding to the code object, for debugging
                     purposes
    :raises ValueError: in case of forbidden bytecode in ``code_obj``
    :raises NameError: in case a forbidden name (containing two underscores)
                       is found in ``code_obj``
    """
    assert_no_dunder_name(code_obj, expr)

    # set operations are almost twice as fast as a manual iteration + condition
    # when loading /web according to line_profiler
    code_codes = {i.opcode for i in dis.get_instructions(code_obj)}
    if not allowed_codes >= code_codes:
        raise ValueError(
            "forbidden opcode(s) in %r (%s): %s"
            % (
                expr,
                code_obj,
                ", ".join(opname[x] for x in (code_codes - allowed_codes)),
            )
        )

    for const in code_obj.co_consts:
        if isinstance(const, CodeType):
            assert_valid_codeobj(allowed_codes, const, "lambda")


def test_expr(expr, allowed_codes, mode="eval", filename=None):
    """test_expr(expression, allowed_codes[, mode[, filename]]) -> code_object

    Test that the expression contains only the allowed opcodes.
    If the expression is valid and contains only allowed codes,
    return the compiled code object.
    Otherwise raise a ValueError, a Syntax Error or TypeError accordingly.

    :param filename: optional pseudo-filename for the compiled expression,
                 displayed for example in traceback frames
    :type filename: string
    """
    try:
        if mode == "eval":
            # eval() does not like leading/trailing whitespace
            expr = expr.strip()
        code_obj = compile(expr, filename or "", mode)
    except (SyntaxError, TypeError, ValueError):
        raise
    except Exception as e:
        raise ValueError('"%s" while compiling\n%r' % (ustr(e), expr))
    assert_valid_codeobj(allowed_codes, code_obj, expr)
    return code_obj


def const_eval(expr):
    """const_eval(expression) -> value

    Safe Python constant evaluation

    Evaluates a string that contains an expression describing
    a Python constant. Strings that are not valid Python expressions
    or that contain other code besides the constant raise ValueError.

    >>> const_eval("10")
    10
    >>> const_eval("[1,2, (3,4), {'foo':'bar'}]")
    [1, 2, (3, 4), {'foo': 'bar'}]
    >>> const_eval("1+2")
    Traceback (most recent call last):
    ...
    ValueError: opcode BINARY_ADD not allowed
    """
    c = test_expr(expr, _CONST_OPCODES)
    return unsafe_eval(c)


def expr_eval(expr):
    """expr_eval(expression) -> value

    Restricted Python expression evaluation

    Evaluates a string that contains an expression that only
    uses Python constants. This can be used to e.g. evaluate
    a numerical expression from an untrusted source.

    >>> expr_eval("1+2")
    3
    >>> expr_eval("[1,2]*2")
    [1, 2, 1, 2]
    >>> expr_eval("__import__('sys').modules")
    Traceback (most recent call last):
    ...
    ValueError: opcode LOAD_NAME not allowed
    """
    c = test_expr(expr, _EXPR_OPCODES)
    return unsafe_eval(c)


_BUILTINS = {
    #'__import__': _import,
    "__import__": __import__,
    "True": True,
    "False": False,
    "None": None,
    "bytes": bytes,
    "str": str,
    "unicode": str,
    "bool": bool,
    "int": int,
    "float": float,
    "enumerate": enumerate,
    "dict": dict,
    "list": list,
    "tuple": tuple,
    "map": map,
    "abs": abs,
    "min": min,
    "max": max,
    "sum": sum,
    "reduce": functools.reduce,
    "filter": filter,
    "sorted": sorted,
    "round": round,
    "len": len,
    "repr": repr,
    "set": set,
    "all": all,
    "any": any,
    "ord": ord,
    "chr": chr,
    "divmod": divmod,
    "isinstance": isinstance,
    "range": range,
    "xrange": range,
    "zip": zip,
    "Exception": Exception,
}


def safe_eval__MAGIC(
    expr,
    globals_dict=None,
    locals_dict=None,
    mode="eval",
    nocopy=False,
    locals_builtins=False,
    filename=None,
):
    """safe_eval(expression[, globals[, locals[, mode[, nocopy]]]]) -> result

    System-restricted Python expression evaluation

    Evaluates a string that contains an expression that mostly
    uses Python constants, arithmetic expressions and the
    objects directly provided in context.

    This can be used to e.g. evaluate
    an OpenERP domain expression from an untrusted source.

    :param filename: optional pseudo-filename for the compiled expression,
                     displayed for example in traceback frames
    :type filename: string
    :throws TypeError: If the expression provided is a code object
    :throws SyntaxError: If the expression provided is not valid Python
    :throws NameError: If the expression provided accesses forbidden names
    :throws ValueError: If the expression provided uses forbidden bytecode
    """
    if type(expr) is CodeType:
        raise TypeError("safe_eval does not allow direct evaluation of code objects.")

    # prevent altering the globals/locals from within the sandbox
    # by taking a copy.
    if not nocopy:
        # isinstance() does not work below, we want *exactly* the dict class
        if (globals_dict is not None and type(globals_dict) is not dict) or (
            locals_dict is not None and type(locals_dict) is not dict
        ):
            _logger.warning(
                "Looks like you are trying to pass a dynamic environment, "
                "you should probably pass nocopy=True to safe_eval()."
            )
        if globals_dict is not None:
            globals_dict = dict(globals_dict)
        if locals_dict is not None:
            locals_dict = dict(locals_dict)

    check_values(globals_dict)
    check_values(locals_dict)

    if globals_dict is None:
        globals_dict = {}

    globals_dict["__builtins__"] = _BUILTINS
    if locals_builtins:
        if locals_dict is None:
            locals_dict = {}
        locals_dict.update(_BUILTINS)
    c = test_expr(expr, _SAFE_OPCODES, mode=mode, filename=filename)
    try:
        return unsafe_eval(c, globals_dict, locals_dict)
    except odoo.exceptions.UserError:
        raise
    except odoo.exceptions.RedirectWarning:
        raise
    except werkzeug.exceptions.HTTPException:
        raise
    except OperationalError:
        # Do not hide PostgreSQL low-level exceptions, to let the auto-replay
        # of serialized transactions work its magic
        raise
    except ZeroDivisionError:
        raise
    except Exception as e:
        raise ValueError(
            '%s: "%s" while evaluating\n%r' % (ustr(type(e))(e), expr)
        )


def test_python_expr__MAGIC(expr, mode="eval"):
    try:
        test_expr(expr, _SAFE_OPCODES, mode=mode)
    except (SyntaxError, TypeError, ValueError) as err:
        if len(err.args) >= 2 and len(err.args[1]) >= 4:
            error = {
                "message": err.args[0],
                "filename": err.args[1][0],
                "lineno": err.args[1][1],
                "offset": err.args[1][2],
                "error_line": err.args[1][3],
            }
            msg = "%s : %s at line %d\n%s" % (
                type(err).__name__,
                error["message"],
                error["lineno"],
                error["error_line"],
            )
        else:
            msg = err
        return msg
    return False


def check_values(d):
    if not d:
        return d
    for v in d.values():
        if isinstance(v, types.ModuleType):
            raise TypeError(
                f"""Module {v} can not be used in evaluation contexts

Prefer providing only the items necessary for your intended use.

If a "module" is necessary for backwards compatibility, use
`odoo.tools.safe_eval.wrap_module` to generate a wrapper recursively
whitelisting allowed attributes.

Pre-wrapped modules are provided as attributes of `odoo.tools.safe_eval`.
"""
            )
    return d


class wrap_module:
    def __init__(self, module, attributes):
        """Helper for wrapping a package/module to expose selected attributes

        :param module: the actual package/module to wrap, as returned by ``import <module>``
        :param iterable attributes: attributes to expose / whitelist. If a dict,
                                    the keys are the attributes and the values
                                    are used as an ``attributes`` in case the
                                    corresponding item is a submodule
        """
        # builtin modules don't have a __file__ at all
        modfile = getattr(module, "__file__", "(built-in)")
        self._repr = f"<wrapped {module.__name__!r} ({modfile})>"
        for attrib in attributes:
            target = getattr(module, attrib)
            if isinstance(target, types.ModuleType):
                target = wrap_module(target, attributes[attrib])
            setattr(self, attrib, target)

    def __repr__(self):
        return self._repr


# dateutil submodules are lazy so need to import them for them to "exist"
import dateutil

mods = ["parser", "relativedelta", "rrule", "tz"]
for mod in mods:
    __import__("dateutil.%s" % mod)
datetime = wrap_module(
    __import__("datetime"),
    [
        "date",
        "datetime",
        "time",
        "timedelta",
        "timezone",
        "tzinfo",
        "MAXYEAR",
        "MINYEAR",
    ],
)
dateutil = wrap_module(dateutil, {mod: getattr(dateutil, mod).__all__ for mod in mods})
json = wrap_module(__import__("json"), ["loads", "dumps"])
time = wrap_module(__import__("time"), ["time", "strptime", "strftime", "sleep"])
pytz = wrap_module(
    __import__("pytz"),
    [
        "utc",
        "UTC",
        "timezone",
    ],
)