Patch CVE-2024-42002

ros2topic/package.xml

@@ -12,6 +12,7 @@
 
   <license>Apache License 2.0</license>
   <license>BSD-3-Clause</license>  <!-- ros2topic/verb/delay.py|hz.py|bw.py are BSD -->
+  <license>MIT License</license> <!-- ros2topic/eval uses MIT License -->
 
   <author email="aditya.pande@openrobotics.org">Aditya Pande</author>
   <author email="dthomas@osrfoundation.org">Dirk Thomas</author>

ros2topic/ros2topic/eval/__init__.py

@@ -0,0 +1,161 @@
+# Copyright 2022 Yaroslav Polyakov
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+
+"""Safe user-supplied python expression evaluation."""
+
+import ast
+import dataclasses
+
+__version__ = '2.0.3'
+
+
+class EvalException(Exception):
+    pass
+
+
+class ValidationException(EvalException):
+    pass
+
+
+class CompilationException(EvalException):
+    exc = None
+
+    def __init__(self, exc):
+        super().__init__(exc)
+        self.exc = exc
+
+
+class ExecutionException(EvalException):
+    exc = None
+
+    def __init__(self, exc):
+        super().__init__(exc)
+        self.exc = exc
+
+
+@dataclasses.dataclass
+class EvalModel:
+    """eval security model."""
+
+    nodes: list = dataclasses.field(default_factory=list)
+    allowed_functions: list = dataclasses.field(default_factory=list)
+    imported_functions: dict = dataclasses.field(default_factory=dict)
+    attributes: list = dataclasses.field(default_factory=list)
+
+    def clone(self):
+        return EvalModel(**dataclasses.asdict(self))
+
+
+class SafeAST(ast.NodeVisitor):
+    """AST-tree walker class."""
+
+    def __init__(self, model: EvalModel):
+        self.model = model
+
+    def generic_visit(self, node):
+        """Check node, raise exception if node is not in whitelist."""
+        if type(node).__name__ in self.model.nodes:
+
+            if isinstance(node, ast.Attribute):
+                print(self.model.attributes)
+                print(node)
+                if node.attr not in self.model.attributes:
+                    raise ValidationException(
+                        'Attribute {aname} is not allowed'.format(
+                            aname=node.attr))
+
+            if isinstance(node, ast.Call):
+                if isinstance(node.func, ast.Name):
+                    if node.func.id not in self.model.allowed_functions and \
+                            node.func.id not in self.model.imported_functions:
+                        raise ValidationException(
+                            'Call to function {fname}() is not allowed'.format(
+                                fname=node.func.id))
+                    else:
+                        # Call to allowed function. good. No exception
+                        pass
+                elif isinstance(node.func, ast.Attribute):
+                    pass
+                    # print("attr:", node.func.attr)
+                else:
+                    raise ValidationException('Indirect function call')
+
+            ast.NodeVisitor.generic_visit(self, node)
+        else:
+            raise ValidationException(
+                'Node type {optype!r} is not allowed. (whitelist it manually)'.format(
+                    optype=type(node).__name__))
+
+
+base_eval_model = EvalModel(
+    nodes=[
+                # 123, 'asdf'
+                'Num', 'Str',
+                # any expression or constant
+                'Expression', 'Constant',
+                # == ...
+                'Compare', 'Eq', 'NotEq', 'Gt', 'GtE', 'Lt', 'LtE',
+                # variable name
+                'Name', 'Load',
+                'BinOp',
+                'Add', 'Sub', 'USub',
+                'Subscript', 'Index',  # person['name']
+                'BoolOp', 'And', 'Or', 'UnaryOp', 'Not',  # True and True
+                'In', 'NotIn',  # "aaa" in i['list']
+                'IfExp',  # for if expressions, like: expr1 if expr2 else expr3
+                'NameConstant',  # for True and False constants
+                'Div', 'Mod'
+            ],
+)
+
+
+mult_eval_model = base_eval_model.clone()
+mult_eval_model.nodes.append('Mul')
+
+
+class Expr():
+
+    def __init__(self, expr, model=None, filename=None):
+
+        self.expr = expr
+        self.model = model or base_eval_model
+
+        try:
+            self.node = ast.parse(self.expr, '<usercode>', 'eval')
+        except SyntaxError as e:
+            raise CompilationException(e)
+
+        v = SafeAST(model=self.model)
+        v.visit(self.node)
+
+        self.code = compile(self.node, filename or '<usercode>', 'eval')
+
+    def safe_eval(self, ctx=None):
+
+        try:
+            result = eval(self.code, self.model.imported_functions, ctx)
+        except Exception as e:
+            raise ExecutionException(e)
+
+        return result
+
+    def __str__(self):
+        return ('Expr(expr={expr!r})'.format(expr=self.expr))

ros2topic/ros2topic/verb/hz.py

@@ -29,8 +29,8 @@
 # This file is originally from:
 # https://github.com/ros/ros_comm/blob/6e5016f4b2266d8a60c9a1e163c4928b8fc7115e/tools/rostopic/src/rostopic/__init__.py
 
-from collections import defaultdict
 
+from collections import defaultdict, OrderedDict
 import functools
 import math
 import threading
@@ -48,7 +48,9 @@
 from ros2topic.api import get_msg_class
 from ros2topic.api import positive_int
 from ros2topic.api import TopicNameCompleter
+from ros2topic.eval import base_eval_model, Expr
 from ros2topic.verb import VerbExtension
+from rosidl_runtime_py.convert import message_to_ordereddict
 
 DEFAULT_WINDOW_SIZE = 10000
 
@@ -91,18 +93,75 @@ def main(self, *, args):
         return main(args)
 
 
+def _setup_base_safe_eval():
+    safe_eval_model = base_eval_model.clone()
+
+    # extend base_eval_model
+    safe_eval_model.nodes.extend(['Call', 'Attribute', 'List', 'Tuple', 'Dict', 'Set',
+                                  'ListComp', 'DictComp', 'SetComp', 'comprehension',
+                                  'Mult', 'Pow', 'boolop', 'mod', 'Invert',
+                                  'Is', 'IsNot', 'FloorDiv', 'If', 'For'])
+
+    # allow-list safe Python built-in functions
+    safe_builtins = [
+        'abs', 'all', 'any', 'bin', 'bool', 'chr', 'cmp', 'divmod', 'enumerate',
+        'float', 'format', 'hex', 'id', 'int', 'isinstance', 'issubclass',
+        'len', 'list', 'long', 'max', 'min', 'ord', 'pow', 'range', 'reversed',
+        'round', 'slice', 'sorted', 'str', 'sum', 'tuple', 'type', 'unichr',
+        'unicode', 'xrange', 'zip', 'filter', 'dict', 'set', 'next'
+    ]
+
+    safe_eval_model.allowed_functions.extend(safe_builtins)
+    return safe_eval_model
+
+
+def _get_nested_messages(msg_ordereddict):
+    """List all message field names recursively."""
+    all_attributes = []
+    for (k, v) in msg_ordereddict.items():
+        all_attributes.append(k)
+        if type(v) is OrderedDict:
+            nested_attrs = _get_nested_messages(v)
+            all_attributes.extend(nested_attrs)
+    return all_attributes
+
+
+def _setup_safe_eval(safe_eval_model, msg_class, topic):
+    # allow-list topic builtins, msg attributes
+    topic_builtins = [i for i in dir(topic) if not i.startswith('_')]
+    safe_eval_model.attributes.extend(topic_builtins)
+
+    # recursively get all nested message attributes
+    # msg_class in this case is a prototype that needs to be instantiated to get
+    # an ordered dictionary of message fields
+    msg_ordereddict = message_to_ordereddict(msg_class())
+    msg_attributes = _get_nested_messages(msg_ordereddict)
+    safe_eval_model.attributes.extend(msg_attributes)
+    return safe_eval_model
+
+
 def main(args):
-    topics = args.topic_name
-    if args.filter_expr:
-        def expr_eval(expr):
-            def eval_fn(m):
-                return eval(expr)
-            return eval_fn
-        filter_expr = expr_eval(args.filter_expr)
-    else:
+    with DirectNode(args) as node:
+        topics = args.topic_name
         filter_expr = None
+        # set up custom safe eval model for filter expression
+        if args.filter_expr:
+            safe_eval_model = _setup_base_safe_eval()
+            for topic in topics:
+                msg_class = get_msg_class(
+                    node, topic, blocking=True, include_hidden_topics=True)
+                if msg_class is None:
+                    continue
+
+                safe_eval_model = _setup_safe_eval(safe_eval_model, msg_class, topic)
+
+            def expr_eval(expr):
+                def eval_fn(m):
+                    safe_expression = Expr(expr, model=safe_eval_model)
+                    return eval(safe_expression.code)
+                return eval_fn
+            filter_expr = expr_eval(args.filter_expr)
 
-    with DirectNode(args) as node:
         _rostopic_hz(node.node, topics, qos_args=args, window_size=args.window_size,
                      filter_expr=filter_expr, use_wtime=args.use_wtime)
 

ros2topic/test/test_cli.py

@@ -938,6 +938,19 @@ def test_filtered_topic_hz(self):
         average_rate = float(average_rate_line_pattern.match(head_line).group(1))
         assert math.isclose(average_rate, 0.5, rel_tol=1e-2)
 
+        # check that use of eval() on hz verb cannot be exploited
+        try:
+            self.launch_topic_command(
+                arguments=[
+                    'hz',
+                    '--filter',
+                    '__import__("os").system("cat /etc/passwd")',
+                    '/chatter'
+                ]
+            )
+        except ValueError as e:
+            self.assertIn('Attribute system is not allowed', str(e))
+
     @launch_testing.markers.retry_on_failure(times=5, delay=1)
     def test_topic_bw(self):
         with self.launch_topic_command(arguments=['bw', '/defaults']) as topic_command: