Fix: plug security issue partition system files via include (#3908)

#### Summary

A recent security review showed that it was possible to partition
arbitrary local files in cases where the filetype supports an "include"
functionality that brings in the content of files external to the
partitioned file. This affects `rst` and `org` files.

#### Fix

This PR fixes the above issue by passing the parameter `sandbox=True` in
all cases where `pypandoc.convert_file` is called.

Note I also added the parameter to a call to this method in the ODT
code. I haven't investigated whether there was a security issue with ODT
files, but it seems better to use pandoc in sandbox mode given the
security issues we know about.

#### Testing

To verify that the tests that are added with this PR find the relevant
issue:
- Remove the `sandbox=True` text from
`unstructured/file_utils/file_conversion.py` line 17.
- Run the tests
`test_unstructured.partition.test_rst.test_rst_wont_include_external_files`
and
`test_unstructured.partition.test_org.test_org_wont_include_external_files`.
Both should fail due to the partitioning containing the word "wombat",
which only appears in a file external to the partitioned file.
- Add the parameter back in, and the tests pass.

CHANGELOG.md

@@ -1,3 +1,12 @@
+## 0.16.20
+
+### Enhancements
+
+### Features
+
+### Fixes
+- **Fix a security issue where rst and org files could read files in the local filesystem**. Certain filetypes could 'include' or 'import' local files into their content, allowing partitioning of arbitrary files from the local filesystem. Partitioning of these files is now sandboxed.
+
 ## 0.16.19
 
 ### Enhancements

example-docs/README-w-include.org

@@ -0,0 +1,29 @@
+#+INCLUDE: "file_we_dont_want_imported"
+
+* Example Docs
+
+The sample docs directory contains the following files:
+
+-  ~example-10k.html~ - A 10-K SEC filing in HTML format
+-  ~layout-parser-paper.pdf~ - A PDF copy of the layout parser paper
+-  ~factbook.xml~ / ~factbook.xsl~ - Example XML/XLS files that you
+   can use to test stylesheets
+
+These documents can be used to test out the parsers in the library. In
+addition, here are instructions for pulling in some sample docs that are
+too big to store in the repo.
+
+** XBRL 10-K
+
+You can get an example 10-K in inline XBRL format using the following
+~curl~. Note, you need to have the user agent set in the header or the
+SEC site will reject your request.
+
+#+BEGIN_SRC bash
+
+   curl -O \
+     -A '${organization} ${email}'
+     https://www.sec.gov/Archives/edgar/data/311094/000117184321001344/0001171843-21-001344.txt
+#+END_SRC
+
+You can parse this document using the HTML parser.

example-docs/README-w-include.rst

@@ -0,0 +1,30 @@
+.. include:: file_we_dont_want_imported
+
+Example Docs
+------------
+
+The sample docs directory contains the following files:
+
+-  ``example-10k.html`` - A 10-K SEC filing in HTML format
+-  ``layout-parser-paper.pdf`` - A PDF copy of the layout parser paper
+-  ``factbook.xml``/``factbook.xsl`` - Example XML/XLS files that you
+   can use to test stylesheets
+
+These documents can be used to test out the parsers in the library. In
+addition, here are instructions for pulling in some sample docs that are
+too big to store in the repo.
+
+XBRL 10-K
+^^^^^^^^^
+
+You can get an example 10-K in inline XBRL format using the following
+``curl``. Note, you need to have the user agent set in the header or the
+SEC site will reject your request.
+
+.. code:: bash
+
+   curl -O \
+     -A '${organization} ${email}'
+     https://www.sec.gov/Archives/edgar/data/311094/000117184321001344/0001171843-21-001344.txt
+
+You can parse this document using the HTML parser.

example-docs/file_we_dont_want_imported

@@ -0,0 +1 @@
+wombat

test_unstructured/partition/test_org.py

@@ -1,8 +1,14 @@
 from __future__ import annotations
 
+from pathlib import Path
+
 from pytest_mock import MockFixture
 
-from test_unstructured.unit_utils import assert_round_trips_through_JSON, example_doc_path
+from test_unstructured.unit_utils import (
+    assert_round_trips_through_JSON,
+    example_doc_path,
+    find_text_in_elements,
+)
 from unstructured.chunking.title import chunk_by_title
 from unstructured.documents.elements import Title
 from unstructured.partition.org import partition_org
@@ -138,3 +144,15 @@ def test_partition_org_respects_detect_language_per_element():
     )
     langs = [element.metadata.languages for element in elements]
     assert langs == [["eng"], ["spa", "eng"], ["eng"], ["eng"], ["spa"]]
+
+
+def test_org_wont_include_external_files():
+    # Make sure our import file is in place (otherwise the import fails silently and test passes)
+    assert Path(example_doc_path("file_we_dont_want_imported")).exists()
+    elements = partition_org(example_doc_path("README-w-include.org"))
+    # The partition should contain some elements
+    assert elements
+    # We find something we expect to find from file we partitioned directly
+    assert find_text_in_elements("instructions", elements)
+    # But we don't find something from the file included within the file we partitioned directly
+    assert not find_text_in_elements("wombat", elements)

test_unstructured/partition/test_rst.py

@@ -1,8 +1,14 @@
 from __future__ import annotations
 
+from pathlib import Path
+
 from pytest_mock import MockFixture
 
-from test_unstructured.unit_utils import assert_round_trips_through_JSON, example_doc_path
+from test_unstructured.unit_utils import (
+    assert_round_trips_through_JSON,
+    example_doc_path,
+    find_text_in_elements,
+)
 from unstructured.chunking.title import chunk_by_title
 from unstructured.documents.elements import Title
 from unstructured.partition.rst import partition_rst
@@ -120,3 +126,15 @@ def test_partition_rst_respects_detect_language_per_element():
     )
     langs = [element.metadata.languages for element in elements]
     assert langs == [["eng"], ["spa", "eng"], ["eng"], ["eng"], ["spa"]]
+
+
+def test_rst_wont_include_external_files():
+    # Make sure our import file is in place (otherwise the import fails silently and test passes)
+    assert Path(example_doc_path("file_we_dont_want_imported")).exists()
+    elements = partition_rst(example_doc_path("README-w-include.rst"))
+    # The partition should contain some elements
+    assert elements
+    # We find something we expect to find from file we partitioned directly
+    assert find_text_in_elements("instructions", elements)
+    # But we don't find something from the file included within the file we partitioned directly
+    assert not find_text_in_elements("wombat", elements)

test_unstructured/unit_utils.py

@@ -257,3 +257,7 @@ def var_mock(request: FixtureRequest, q_var_name: str, **kwargs: Any) -> Mock:
     _patch = patch(q_var_name, **kwargs)
     request.addfinalizer(_patch.stop)
     return _patch.start()
+
+
+def find_text_in_elements(text: str, elements: List[Element]):
+    return any(el.text.find(text) != -1 for el in elements)

unstructured/__version__.py

@@ -1 +1 @@
-__version__ = "0.16.19"  # pragma: no cover
+__version__ = "0.16.20"  # pragma: no cover

unstructured/file_utils/file_conversion.py

@@ -14,7 +14,7 @@ def convert_file_to_text(filename: str, source_format: str, target_format: str)
     import pypandoc
 
     try:
-        text = pypandoc.convert_file(filename, target_format, format=source_format)
+        text = pypandoc.convert_file(filename, target_format, format=source_format, sandbox=True)
     except FileNotFoundError as err:
         msg = (
             f"Error converting the file to text. Ensure you have the pandoc package installed on"

unstructured/partition/odt.py

@@ -107,10 +107,7 @@ def _convert_odt_to_docx(
     import pypandoc
 
     pypandoc.convert_file(
-        source_file_path,
-        "docx",
-        format="odt",
-        outputfile=target_docx_path,
+        source_file_path, "docx", format="odt", outputfile=target_docx_path, sandbox=True
     )
 
     return target_docx_path