fix: Remote Code Execution

Signed-off-by: degenaro <lou.degenaro@gmail.com>

Author: degenaro

tests/trestle/core/commands/author/jinja_cmd_test.py

@@ -16,6 +16,7 @@
 import os
 import pathlib
 import shutil
+from types import SimpleNamespace
 
 import pytest
 
@@ -24,7 +25,7 @@
 from tests.test_utils import execute_command_and_assert, setup_for_ssp
 
 from trestle.common.err import TrestleError
-from trestle.core.commands.author.jinja import _number_captions
+from trestle.core.commands.author.jinja import JinjaCmd, _number_captions
 from trestle.core.commands.author.ssp import SSPGenerate
 from trestle.core.markdown.docs_markdown_node import DocsMarkdownNode
 
@@ -364,3 +365,43 @@ def test_jinja_docs_profile_path_traversal_protection(tmp_trestle_dir: pathlib.P
     # Test 4: Valid relative path should succeed
     output_file = tmp_trestle_dir / 'controls_output/ac/ac-1.md'
     PathSecurityValidator.validate_local_path(output_file, tmp_trestle_dir)  # Should not raise
+
+
+def test_render_template_does_not_recursively_evaluate_untrusted_data(tmp_path: pathlib.Path) -> None:
+    """Test that rendered attacker-controlled data is not re-evaluated as Jinja."""
+    template_path = tmp_path / 'template.j2'
+    template_path.write_text('Title: {{ ssp.metadata.title }}', encoding='utf-8')
+
+    jinja_env = JinjaCmd._create_jinja_environment(tmp_path)
+    template = jinja_env.get_template(template_path.name)
+
+    lut = {
+        'ssp': SimpleNamespace(
+            metadata=SimpleNamespace(title="{{ namespace.__init__.__globals__.os.system('touch poc.txt') }}")
+        )
+    }
+
+    output = JinjaCmd.render_template(template, lut, tmp_path)
+
+    assert output.startswith('Title: {{ namespace.__init__.__globals__.os.system(')
+    assert 'touch poc.txt' in output
+    assert '{{' in output
+    assert '}}' in output
+    assert '&' in output
+    assert not (tmp_path / 'poc.txt').exists()
+
+
+def test_render_template_supports_trusted_include(tmp_path: pathlib.Path) -> None:
+    """Test that trusted template includes continue to work."""
+    include_path = tmp_path / 'partial.j2'
+    include_path.write_text('World', encoding='utf-8')
+
+    template_path = tmp_path / 'template.j2'
+    template_path.write_text("Hello {% include 'partial.j2' %}", encoding='utf-8')
+
+    jinja_env = JinjaCmd._create_jinja_environment(tmp_path)
+    template = jinja_env.get_template(template_path.name)
+
+    output = JinjaCmd.render_template(template, {}, tmp_path)
+
+    assert output == 'Hello World'

trestle/core/commands/author/jinja.py

@@ -20,10 +20,9 @@
 import operator
 import pathlib
 import re
-import uuid
 from typing import Any, Dict, Optional
 
-from jinja2 import ChoiceLoader, DictLoader, Environment, FileSystemLoader, Template
+from jinja2 import Environment, FileSystemLoader, Template
 
 from ruamel.yaml import YAML
 
@@ -49,8 +48,6 @@
 class JinjaCmd(CommandPlusDocs):
     """Transform an input template to an output document using jinja templating."""
 
-    max_recursion_depth = 2
-
     name = 'jinja'
 
     def _init_arguments(self) -> None:
@@ -192,9 +189,7 @@ def jinja_ify(
     ) -> int:
         """Run jinja over an input file with additional booleans."""
         template_folder = pathlib.Path.cwd()
-        jinja_env = Environment(
-            loader=FileSystemLoader(template_folder), extensions=extensions(), trim_blocks=True, autoescape=True
-        )
+        jinja_env = JinjaCmd._create_jinja_environment(template_folder)
         template = jinja_env.get_template(str(r_input_file))
         # create boolean dict
         if operator.xor(bool(ssp), bool(profile)):
@@ -286,9 +281,7 @@ def jinja_multiple_md(
 
                 control_writer = DocsControlWriter()
 
-                jinja_env = Environment(
-                    loader=FileSystemLoader(template_folder), extensions=extensions(), trim_blocks=True, autoescape=True
-                )
+                jinja_env = JinjaCmd._create_jinja_environment(template_folder)
                 template = jinja_env.get_template(str(r_input_file))
                 lut['catalog_interface'] = catalog_interface
                 lut['control_interface'] = ControlInterface()
@@ -308,27 +301,16 @@ def jinja_multiple_md(
         return CmdReturnCodes.SUCCESS.value
 
     @staticmethod
-    def render_template(template: Template, lut: Dict[str, Any], template_folder: pathlib.Path) -> str:
-        """Render template."""
-        new_output = template.render(**lut)
-        output = ''
-        # This recursion allows nesting within expressions (e.g. an expression can contain jinja templates).
-        error_countdown = JinjaCmd.max_recursion_depth
-        while new_output != output and error_countdown > 0:
-            error_countdown = error_countdown - 1
-            output = new_output
-            random_name = uuid.uuid4()  # Should be random and not used.
-            dict_loader = DictLoader({str(random_name): new_output})
-            jinja_env = Environment(
-                loader=ChoiceLoader([dict_loader, FileSystemLoader(template_folder)]),
-                extensions=extensions(),
-                autoescape=True,
-                trim_blocks=True,
-            )
-            template = jinja_env.get_template(str(random_name))
-            new_output = template.render(**lut)
+    def _create_jinja_environment(template_folder: pathlib.Path) -> Environment:
+        """Create the trusted Jinja environment used for loading template files."""
+        return Environment(
+            loader=FileSystemLoader(template_folder), extensions=extensions(), trim_blocks=True, autoescape=True
+        )
 
-        return output
+    @staticmethod
+    def render_template(template: Template, lut: Dict[str, Any], template_folder: pathlib.Path) -> str:
+        """Render a trusted template exactly once to avoid recursive SSTI of untrusted data."""
+        return template.render(**lut)
 
 
 def _number_captions(md_body: str) -> str: