SetRulesDir crashes when Rules directory is read-only

[joanmarie]

When Rules are installed to a read-only directory (e.g. /usr/share/), SetRulesDir panics because zip_extract_shim tries to extract the .zip files inside each language/braille subdirectory in-place.

Reproduced with the prebuilt libmathcat_py-64-3.13-linux binary and Rules.zip from the 0.7.5 release on Linux.

Steps to reproduce:

Save and run this python script:

import os
import shutil
import sys
import tempfile
import urllib.request
import zipfile

base_url = "https://github.com/daisy/MathCATForPython/releases/download/0.7.5"

# Fetch the prebuilt Linux binary and Rules
work_dir = tempfile.mkdtemp()
for name in ["libmathcat_py-64-3.13-linux.zip", "Rules.zip"]:
    dest = os.path.join(work_dir, name)
    print(f"Downloading {name}...")
    urllib.request.urlretrieve(f"{base_url}/{name}", dest)
    with zipfile.ZipFile(dest) as zf:
        zf.extractall(work_dir)

# Make Rules read-only (like /usr/share on Linux)
for root, dirs, _files in os.walk(os.path.join(work_dir, "Rules")):
    for d in dirs:
        os.chmod(os.path.join(root, d), 0o555)

# Import the .so from the work dir
sys.path.insert(0, work_dir)
import libmathcat_py

# This crashes with PermissionDenied
print("Calling SetRulesDir on read-only directory...")
libmathcat_py.SetRulesDir(os.path.join(work_dir, "Rules"))

When I run this locally, I get the following:

$ python mathcat-crash.py
Downloading libmathcat_py-64-3.13-linux.zip...
Downloading Rules.zip...
Calling SetRulesDir on read-only directory...

thread '<unnamed>' (3596307) panicked at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/mathcat-0.7.5/src/shim_filesystem.rs:371:46:
Zip extraction failed: Io(Os { code: 13, kind: PermissionDenied, message: "Permission denied" })
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Traceback (most recent call last):
  File "/home/jd/mathcat-crash.py", line 30, in <module>
    libmathcat_py.SetRulesDir(os.path.join(work_dir, "Rules"))
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pyo3_runtime.PanicException: Zip extraction failed: Io(Os { code: 13, kind: PermissionDenied, message: "Permission denied" })

[NSoiffer]

You can't make the directory read-only, at least not in the form you have. Inside the zipped Rules dir are more zipped files, one per language/braille code. When MathCAT looks to use a language or braille code, it looks to see if there is an unzipped rule file (I think maybe *_Rules.yaml, but I might wrong which file). If there isn't such a file, it will unzip the xx.zip file (e.g, es.zip). The idea is that typically only one language and a maybe one braille file will be used by an individual user. At least 1mb is saved this way, and I suspect that will grow to 2mb of savings are more languages are used.

I see two solutions:

1. Unzip all the sub-dirs (Rules/Languages/xx/xx.zip, Rules/Braille/xx/xx.zip) and store those as read only. The new NVDA which builds in MathCAT does this. These days, 2mb is a drop in the bucket, if that, for most installations.
2. Copy them over to user space and make the directory writable. This is what happens for NVDA's add-ons, but that works because the add-ons go into the user space to start with, so the rules live there already.

I suspect the first option is the one that makes sense for Orca.

Please close the issue if that solves the problem. Otherwise, let me know what new problem shows up.

[joanmarie]

Thanks Neil. I'm already doing solution 1 locally, but it's a bit messy. Maybe (definitely) I need better meson + subprojects chops. Anyway, I will close the issue and figure something out. Thanks again!