Merge branch 'module_safe_eval' into fix_lineinfile_newlines

lib/ansible/module_utils/basic.py

@@ -101,6 +101,44 @@ except ImportError:
     import syslog
     has_journal = False
 
+try:
+    from ast import literal_eval as _literal_eval
+except ImportError:
+    # a replacement for literal_eval that works with python 2.4. from: 
+    # https://mail.python.org/pipermail/python-list/2009-September/551880.html
+    # which is essentially a cut/past from an earlier (2.6) version of python's
+    # ast.py
+    from compiler import parse
+    from compiler.ast import *
+    def _literal_eval(node_or_string):
+        """
+        Safely evaluate an expression node or a string containing a Python
+        expression.  The string or node provided may only consist of the  following
+        Python literal structures: strings, numbers, tuples, lists, dicts,  booleans,
+        and None.
+        """
+        _safe_names = {'None': None, 'True': True, 'False': False}
+        if isinstance(node_or_string, basestring):
+            node_or_string = parse(node_or_string, mode='eval')
+        if isinstance(node_or_string, Expression):
+            node_or_string = node_or_string.node
+        def _convert(node):
+            if isinstance(node, Const) and isinstance(node.value, (basestring, int, float, long, complex)):
+                 return node.value
+            elif isinstance(node, Tuple):
+                return tuple(map(_convert, node.nodes))
+            elif isinstance(node, List):
+                return list(map(_convert, node.nodes))
+            elif isinstance(node, Dict):
+                return dict((_convert(k), _convert(v)) for k, v in node.items)
+            elif isinstance(node, Name):
+                if node.name in _safe_names:
+                    return _safe_names[node.name]
+            elif isinstance(node, UnarySub):
+                return -_convert(node.expr)
+            raise ValueError('malformed string')
+        return _convert(node_or_string)
+
 FILE_COMMON_ARGUMENTS=dict(
     src = dict(),
     mode = dict(),
@@ -700,6 +738,38 @@ class AnsibleModule(object):
             else:
                 self.fail_json(msg="internal error: do not know how to interpret argument_spec")
 
+    def safe_eval(self, str, locals=None, include_exceptions=False):
+
+        # do not allow method calls to modules
+        if not isinstance(str, basestring):
+            # already templated to a datastructure, perhaps?
+            if include_exceptions:
+                return (str, None)
+            return str
+        if re.search(r'\w\.\w+\(', str):
+            if include_exceptions:
+                return (str, None)
+            return str
+        # do not allow imports
+        if re.search(r'import \w+', str):
+            if include_exceptions:
+                return (str, None)
+            return str
+        try:
+            result = None
+            if not locals:
+                result = _literal_eval(str)
+            else:
+                result = _literal_eval(str, None, locals)
+            if include_exceptions:
+                return (result, None)
+            else:
+                return result
+        except Exception, e:
+            if include_exceptions:
+                return (str, e)
+            return str
+
     def _check_argument_types(self):
         ''' ensure all arguments have the requested type '''
         for (k, v) in self.argument_spec.iteritems():