Revert "fix(general): using asteval instead of using eval (#7116)"

This reverts commit 5ddad08.

Author: thentenaar

Pipfile

@@ -84,7 +84,6 @@ spdx-tools = ">=0.8.0,<0.9.0"
 license-expression = ">=30.1.0,<31.0.0"
 rustworkx = ">=0.13.0,<1.0.0"
 pydantic = ">=2.0.0,<3.0.0"
-asteval = "==1.0.5"
 
 [requires]
 python_version = "3.8"

Pipfile.lock

@@ -20,7 +20,6 @@
 # exclude "']" one the right side of the compare via (?!']), this can happen with a base64 encoded string
 COMPARE_REGEX = re.compile(r"^(?P<a>.+?)\s*(?P<operator>==|!=|>=|>|<=|<|&&|\|\|)\s*(?P<b>(?!']).+)$")
 COMPARE_OPERATORS = (" == ", " != ", " < ", " <= ", " > ", " >= ", " && ", " || ")
-REMOVE_TRAILING_COMMAS = re.compile(r',(\s*[}\]])')
 
 CHECKOV_RENDER_MAX_LEN = force_int(os.getenv("CHECKOV_RENDER_MAX_LEN", "10000"))
 
@@ -85,10 +84,7 @@ def _eval_merge_as_list(eval_value: Any) -> Any:
 
 def _try_evaluate(input_str: Union[str, bool]) -> Any:
     try:
-        result = evaluate(input_str)  # type:ignore[arg-type]
-        if result is None:
-            raise Exception(f"Can't evaluate {input_str}")
-        return result
+        return evaluate(input_str)  # type:ignore[arg-type]
     except Exception:
         try:
             return evaluate(f'"{input_str}"')
@@ -101,12 +97,7 @@ def _try_evaluate(input_str: Union[str, bool]) -> Any:
                     return json.loads(input_str)
                 return input_str
             except Exception:
-                try:
-                    # Remove trailing commas before } or ]
-                    input_str_no_trailing = REMOVE_TRAILING_COMMAS.sub(r'\1', input_str)  # type:ignore[arg-type]
-                    return json.loads(input_str_no_trailing)
-                except Exception:
-                    return input_str
+                return input_str
 
 
 def replace_string_value(original_str: Any, str_to_replace: str, replaced_value: str, keep_origin: bool = True) -> Any:

checkov/terraform/graph_builder/variable_rendering/evaluate_terraform.py

@@ -8,7 +8,6 @@
 from functools import reduce
 from math import ceil, floor, log
 from typing import Union, Any, Dict, Callable, List, Optional
-from asteval import Interpreter
 
 from checkov.terraform.parser_functions import tonumber, FUNCTION_FAILED, create_map, tobool, tostring
 
@@ -357,21 +356,13 @@ def terraform_try(*args: Any) -> Any:
 SAFE_EVAL_DICT["formatdate"] = formatdate
 
 
-def get_asteval() -> Interpreter:
-    # asteval provides a safer environment for evaluating expressions by restricting the operations to a secure subset, significantly reducing the risk of executing malicious code.
-    return Interpreter(
-        symtable=SAFE_EVAL_DICT,
-        use_numpy=False,
-        minimal=True
-    )
-
-
 def evaluate(input_str: str) -> Any:
-    """
-    Safely evaluate a Terraform-like function expression using a predefined function map.
-    Falls back gracefully if evaluation fails.
-    """
-    if not input_str or input_str == "...":
+    count_underscores = input_str.count("__")
+    # We are operating under the assumption that the function name will start and end with "__", ensuring that we have at least two of them
+    if count_underscores >= 2:
+        logging.debug(f"got a substring with double underscore, which is not allowed. origin string: {input_str}")
+        return input_str
+    if input_str == "...":
         # don't create an Ellipsis object
         return input_str
     if input_str.startswith("try"):
@@ -380,19 +371,11 @@ def evaluate(input_str: str) -> Any:
 
         # Don't use str.replace to make sure we replace just the first occurrence
         input_str = f"{TRY_STR_REPLACEMENT}{input_str[3:]}"
-    asteval = get_asteval()
-    log_level = os.getenv("LOG_LEVEL")
-    should_log_asteval_errors = log_level == "DEBUG"
     if RANGE_PATTERN.match(input_str):
-        temp_eval = asteval(input_str, show_errors=should_log_asteval_errors)
+        temp_eval = eval(input_str, {"__builtins__": None}, SAFE_EVAL_DICT)  # nosec
         evaluated = input_str if temp_eval < 0 else temp_eval
     else:
-        evaluated = asteval(input_str, show_errors=should_log_asteval_errors)
-
-    if asteval.error:
-        error_messages = [err.get_error() for err in asteval.error]
-        raise ValueError(f"Safe evaluation error: {error_messages}")
-
+        evaluated = eval(input_str, {"__builtins__": None}, SAFE_EVAL_DICT)  # nosec
     return evaluated if not isinstance(evaluated, str) else remove_unicode_null(evaluated)
 
 

checkov/terraform/graph_builder/variable_rendering/safe_eval_functions.py

@@ -19,6 +19,3 @@ ignore_missing_imports = True
 
 [mypy-checkov.*]
 follow_imports = skip
-
-[mypy-asteval.*]
-ignore_missing_imports = True

mypy.ini

@@ -18,7 +18,7 @@
         'repo_name': 'terraform-aws-components',
         'threshold': {
             "Darwin": 19.0,
-            "Linux": 13.0,
+            "Linux": 11.0,
             "Windows": 15.0,
         }
     },
@@ -114,5 +114,6 @@ def run_kubernetes_scan():
         runner_registry = RunnerRegistry(banner, runner_filter, k8_runner())
         reports = runner_registry.run(root_folder=test_files_dir)
         assert len(reports) > 0
+
     benchmark(run_kubernetes_scan)
     assert benchmark.stats.stats.mean <= repo_threshold + (DEVIATION_PERCENT / 100) * repo_threshold

performance_tests/test_checkov_performance.py

@@ -107,7 +107,6 @@ def run(self) -> None:
         "license-expression<31.0.0,>=30.1.0",
         "rustworkx>=0.13.0,<1.0.0",
         "pydantic<3.0.0,>=2.0.0",
-        "asteval==1.0.5"
     ],
     dependency_links=[],  # keep it empty, needed for pipenv-setup
     license="Apache License 2.0",

setup.py

@@ -7,7 +7,7 @@
 from checkov.terraform.graph_builder.variable_rendering.evaluate_terraform import evaluate_terraform, \
     replace_string_value, \
     remove_interpolation, _find_new_value_for_interpolation
-from checkov.terraform.graph_builder.variable_rendering.safe_eval_functions import evaluate, get_asteval
+from checkov.terraform.graph_builder.variable_rendering.safe_eval_functions import evaluate
 
 
 class TestTerraformEvaluation(TestCase):
@@ -518,29 +518,11 @@ def test_try_then_merge_block(self):
         result = evaluate_terraform(input_str)
         self.assertEqual(expected, result)
 
-    def test_empty_string(self):
-        input_str = "   "
-        expected = input_str
-        result = evaluate_terraform(input_str)
-        self.assertEqual(expected, result)
-
-        input_str = ""
-        expected = input_str
-        result = evaluate_terraform(input_str)
-        self.assertEqual(expected, result)
-
-    def test_dict_as_string(self):
-        expected = {'Statement': [
-            {'Action': ['lambda:CreateFunction', 'lambda:CreateEventSourceMapping', 'dynamodb:CreateTable'],
-             'Effect': 'Allow', 'Resource': '*'}], 'Version': '2012-10-17'}
-        input_str = '  {    "Version": "2012-10-17",    "Statement": [      {        "Effect": "Allow",        "Action": [          "lambda:CreateFunction",          "lambda:CreateEventSourceMapping",          "dynamodb:CreateTable",        ],        "Resource": "*"      }    ]  }'
-        result = evaluate_terraform(input_str)
-        assert result == expected
-
 
 @pytest.mark.parametrize(
     "origin_str,str_to_replace,new_value,expected",
     [
+
         ("${lookup({'a': ${local.protocol1}},\"a\",\"https\")}", '${local.protocol1}', 'local.protocol1', "'local.protocol1'"),
         ('${length(keys(var.identity)) > 0 ? [${var.identity}] : []}', '${var.identity}', 'var.identity', 'var.identity'),
     ],
@@ -555,32 +537,8 @@ def test_evaluate_range_pattern() -> None:
 
     # Test range pattern
     assert evaluate("1-10") == "1-10"
-    assert evaluate("5-25")== "5-25"
+    assert evaluate("5-25") == "5-25"
     assert evaluate("10-5") == 5
 
     # Test non-range pattern for comparison
     assert evaluate("1+1") == 2
-
-
-EVAL_DANGEROUS_INPUTS = [
-    ("unicode_characters", "[{}._﹎class_﹎._﹎bases_﹎[0]._﹎subclasses_﹎()]"),
-    ("generators_to_bypass_protections_code", "((gen:=(gen_list[0].gi_frame.f_back.f_back.f_globals for _ in [1,]),v:=gen_list.append(gen), gen_list[0])[2] for gen_list in [[]]).send(None).send(None).get('_'+'_builtins_'+'_')['_'+'_import_'+'_']('os').system('date >> /tmp/gen-example')"),
-    ("system command", "__import__('os').system('rm -rf /')"),
-    ("read passwd", "open('/etc/passwd').read()"),
-    ("access builtins", "__builtins__.__import__('os').listdir('.')"),
-    ("exec call", "exec('print(123)')"),
-    ("create file", "__import__('os').popen('touch /tmp/hacked').read()"),
-    ("subclasses", "().__class__.__bases__[0].__subclasses__()"),
-    ("socket connection", "__import__('socket').socket().connect(('example.com', 80))"),
-    ("lambda trick", "(lambda f: f('ls'))(__import__('os').system)")
-]
-
-
-@pytest.mark.parametrize("description, input_str", EVAL_DANGEROUS_INPUTS)
-def test_evaluate_malicious_code(description: str, input_str: str)-> None:
-    expected = input_str
-    result = evaluate_terraform(input_str)
-    assert result == expected
-    asteval = get_asteval()
-    asteval(input_str)
-    assert asteval.error