142 lines
4.5 KiB
Python
142 lines
4.5 KiB
Python
# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>
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#
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# This file is part of Ansible
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#
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# Ansible is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# Ansible is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Ansible. If not, see <http://www.gnu.org/licenses/>.
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from __future__ import (absolute_import, division, print_function)
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__metaclass__ = type
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import ast
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import sys
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from ansible.compat.six import string_types
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from ansible.compat.six.moves import builtins
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from ansible import constants as C
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from ansible.plugins import filter_loader, test_loader
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def safe_eval(expr, locals={}, include_exceptions=False):
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'''
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This is intended for allowing things like:
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with_items: a_list_variable
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Where Jinja2 would return a string but we do not want to allow it to
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call functions (outside of Jinja2, where the env is constrained). If
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the input data to this function came from an untrusted (remote) source,
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it should first be run through _clean_data_struct() to ensure the data
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is further sanitized prior to evaluation.
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Based on:
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http://stackoverflow.com/questions/12523516/using-ast-and-whitelists-to-make-pythons-eval-safe
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'''
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# define certain JSON types
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# eg. JSON booleans are unknown to python eval()
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JSON_TYPES = {
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'false': False,
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'null': None,
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'true': True,
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}
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# this is the whitelist of AST nodes we are going to
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# allow in the evaluation. Any node type other than
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# those listed here will raise an exception in our custom
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# visitor class defined below.
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SAFE_NODES = set(
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(
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ast.Add,
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ast.BinOp,
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ast.Call,
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ast.Compare,
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ast.Dict,
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ast.Div,
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ast.Expression,
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ast.List,
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ast.Load,
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ast.Mult,
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ast.Num,
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ast.Name,
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ast.Str,
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ast.Sub,
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ast.Tuple,
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ast.UnaryOp,
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)
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)
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# AST node types were expanded after 2.6
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if sys.version_info[:2] >= (2, 7):
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SAFE_NODES.update(
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set(
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(ast.Set,)
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)
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)
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# And in Python 3.4 too
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if sys.version_info[:2] >= (3, 4):
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SAFE_NODES.update(
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set(
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(ast.NameConstant,)
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)
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)
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filter_list = []
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for filter in filter_loader.all():
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filter_list.extend(filter.filters().keys())
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test_list = []
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for test in test_loader.all():
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test_list.extend(test.tests().keys())
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CALL_WHITELIST = C.DEFAULT_CALLABLE_WHITELIST + filter_list + test_list
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class CleansingNodeVisitor(ast.NodeVisitor):
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def generic_visit(self, node, inside_call=False):
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if type(node) not in SAFE_NODES:
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raise Exception("invalid expression (%s)" % expr)
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elif isinstance(node, ast.Call):
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inside_call = True
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elif isinstance(node, ast.Name) and inside_call:
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if hasattr(builtins, node.id) and node.id not in CALL_WHITELIST:
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raise Exception("invalid function: %s" % node.id)
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# iterate over all child nodes
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for child_node in ast.iter_child_nodes(node):
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self.generic_visit(child_node, inside_call)
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if not isinstance(expr, string_types):
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# already templated to a datastructure, perhaps?
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if include_exceptions:
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return (expr, None)
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return expr
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cnv = CleansingNodeVisitor()
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try:
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parsed_tree = ast.parse(expr, mode='eval')
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cnv.visit(parsed_tree)
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compiled = compile(parsed_tree, expr, 'eval')
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result = eval(compiled, JSON_TYPES, dict(locals))
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if include_exceptions:
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return (result, None)
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else:
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return result
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except SyntaxError as e:
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# special handling for syntax errors, we just return
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# the expression string back as-is to support late evaluation
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if include_exceptions:
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return (expr, None)
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return expr
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except Exception as e:
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if include_exceptions:
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return (expr, e)
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return expr
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