android: add run-time patch to make pycryptodomex work
What the developer wrote
Authored by SomberNight
android: add run-time patch to make pycryptodomex work
to work around https://github.com/kivy/python-for-android/issues/1866 :
> PyCryptodome >=3.6.0 crashes at runtime (since commit https://github.com/Legrandin/pycryptodome/commit/f5aa2c1618e97b6d773172fdd07794a0a6f05905). So actually the currently pinned version in the recipe does not work:
> https://github.com/kivy/python-for-android/blob/80e4f059c1ee0da48a7c85167087dfe5928ac395/pythonforandroid/recipes/pycryptodome/__init__.py#L5
>
> The issue at runtime is with ctypes.
>
>
> Say I have a main script that just does the following (https://github.com/Legrandin/pycryptodome/blob/95ccce7ae82d3a36f1a8652dd2c645222d0128dd/lib/Crypto/Util/_raw_api.py#L200):
> ```
> import ctypes
> ctypes.pythonapi.PyObject_GetBuffer
> ```
>
> This works with cpython on my laptop, but with the p4a-compiled python on Android it fails:
>
> ```
> 06-14 19:06:27.053 15246 15274 I python : Android kivy bootstrap done. __name__ is __main__
> 06-14 19:06:27.053 15246 15274 I python : AND: Ran string
> 06-14 19:06:27.053 15246 15274 I python : Run user program, change dir and execute entrypoint
> 06-14 19:06:27.092 15246 15274 I python : Traceback (most recent call last):
> 06-14 19:06:27.092 15246 15274 I python : File "/home/user/wspace/electrum/.buildozer/android/app/main.py", line 84, in <module>
> 06-14 19:06:27.093 15246 15274 I python : File "/home/user/wspace/electrum/.buildozer/android/platform/build/build/other_builds/python3-libffi-openssl-sqlite3/armeabi-v7a__ndk_target_21/python3/Lib/ctypes/__init__.py", line 369, in __getattr__
> 06-14 19:06:27.093 15246 15274 I python : File "/home/user/wspace/electrum/.buildozer/android/platform/build/build/other_builds/python3-libffi-openssl-sqlite3/armeabi-v7a__ndk_target_21/python3/Lib/ctypes/__init__.py", line 374, in __getitem__
> 06-14 19:06:27.094 15246 15274 I python : AttributeError: undefined symbol: PyObject_GetBuffer
> ```
>
> I have also tried to access some other attributes of `ctypes.pythonapi`, such as `Py_IncRef`, which raises the same exception.
---
Unclear if the issue still affects newer p4a: upstream seems to think it's fixed, but there multiple comments in the thread saying otherwise. Anyway, rebasing p4a has other blockers atm.
What changed, and why it matters
This commit adds a small Android-only workaround so that a cryptography library (pycryptodomex) can load correctly inside the Electrum mobile app. It replaces the way Python finds its own C API with an explicit path to the Python shared library. There is no direct security vulnerability here; it is a compatibility patch for a packaging/toolchain issue. However, it is a 'hack' that touches low-level Python internals, so it could in theory affect app stability or future updates.
Treat as a maintenance/compatibility patch rather than a security fix. Reviewers should verify that `libpython%d.%d.so` exists and is loadable on all supported Android ABIs and Python versions, and that the workaround does not interfere with other ctypes users. Consider removing the hack once python-for-android upstream definitively resolves issue #1866 and Electrum rebases to that p4a version.
Security signals we found
Low-level ctypes/pythonapi manipulation
Workaround for missing/undefined CPython symbols in Android build
Dependency on external shared library path derived from sys.version_info
No input validation or sanititation involved (not applicable to this patch)
Evidence from the diff
On Android builds created with python-for-android, ctypes.pythonapi defaults to ctypes.PyDLL(None), which fails to resolve symbols such as PyObject_GetBuffer because the Python shared library is not loaded with global symbol visibility. The patch explicitly sets ctypes.pythonapi = ctypes.PyDLL('libpythonX.Y.so') before pycryptodomex is imported, allowing PyCryptodome’s ctypes-based raw API to find the needed CPython buffer protocol symbols. The change is gated behind if is_android and is sourced from an upstream p4a issue comment.
Changed components
run_electrum startup scriptAndroid build of Electrumpycryptodomex / PyCryptodome initialization pathctypes/pythonapi on AndroidInspect captured patch +7 / −0
diff --git a/run_electrum b/run_electrum
index e9b3ab8..3d75478 100755
--- a/run_electrum
+++ b/run_electrum
@@ -100,6 +100,13 @@ if not is_android:
check_imports()
+if is_android:
+ # hack to make pycryptodomex work on Android
+ # from https://github.com/kivy/python-for-android/issues/1866#issuecomment-927157780
+ import ctypes
+ ctypes.pythonapi = ctypes.PyDLL("libpython%d.%d.so" % sys.version_info[:2]) # replaces ctypes.PyDLL(None)
+
+
sys._ELECTRUM_RUNNING_VIA_RUNELECTRUM = True # used by logging.py
from electrum.logging import get_logger, configure_logging # import logging submodule first
Why this scored 16/100
Community notes
Notes can correct, qualify, or add evidence to the AI analysis. Every note shown here has been validated by a human moderator.
The AI analysis stands alone for now. Submit a note if you can add evidence or important context.