RecursionError on circular reference between Note and Report

[SYNchroACK]

Description

Please understand that this is a dummy example. In real scenario, a potential circular reference can happen and is not against STIX standard (AFAIK) but pycti cannot handle it.

from datetime import datetime

from stix2 import Note, Report, DomainName, Bundle

...

domain = DomainName(value="test.com")
report = Report(name="my report", object_refs=[domain], published=datetime.now())
note = Note(content="my analysis notes", object_refs=[report])

updated_report = report.new_version(object_refs=report.object_refs + [note])

bundle = Bundle(domain, note, updated_report)

self.helper.send_stix2_bundle(
    bundle=bundle.serialize(),
    work_id=work_id,
    update=self.update_existing_data,
)

Traceback (most recent call last):
  File \"/development/marti-opencti/importers/misp/src/connector/base.py\", line 226, in run
    self._run(work_id)
  File \"/development/marti-opencti/importers/misp/src/connector/base.py\", line 300, in _run
    raise error
  File \"/development/marti-opencti/importers/misp/src/connector/base.py\", line 283, in _run
    self.helper.send_stix2_bundle(
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/connector/opencti_connector_helper.py\", line 974, in send_stix2_bundle
    bundles = stix2_splitter.split_bundle(bundle, True, event_version)
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 90, in split_bundle
    self.enlist_element(item[\"id\"], raw_data)
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 40, in enlist_element
    nb_deps += self.enlist_element(element_ref, raw_data)
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 40, in enlist_element
    nb_deps += self.enlist_element(element_ref, raw_data)
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 40, in enlist_element
    nb_deps += self.enlist_element(element_ref, raw_data)
  [Previous line repeated 980 more times]
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 43, in enlist_element
    elif key.endswith(\"_ref\") and self.is_ref_key_supported(key):
  File \"/home/vscode/.local/lib/python3.10/site-packages/pycti/utils/opencti_stix2_splitter.py\", line 19, in is_ref_key_supported
    def is_ref_key_supported(self, key):
  File \"_pydevd_bundle/pydevd_cython.pyx\", line 1457, in _pydevd_bundle.pydevd_cython.SafeCallWrapper.__call__
RecursionError: maximum recursion depth exceeded while calling a Python object

Environment

1. PyCTI: 5.9.6

[Markus98]

This issue is still present in 5.12.5.

In my case the issue happens when I have a Directory object which has the contains_refs attribute referring to a File object, and that File object has the attribute parent_directory_ref, which points back to the Directory object. This causes a circular reference. As far as I know, this is valid STIX as well but it causes pycti to crash.

Please look into this issue.