如何验证xlrd与xlsxwriter模块无外网请求以通过安全审核？

Great question! Since your security team is strict about unauthorized outbound traffic, here are several reliable ways to verify that xlrd and xlsxwriter don't make external network calls:

1. Offline Environment Testing #

This is the most straightforward method—remove all network access and see if the modules work as expected:

• First, download the modules locally on a machine with internet access using:

  pip download xlrd xlsxwriter
  

  This will save the module wheels to your current directory.
• Transfer these files to a machine/VM with no network connectivity (or disable all network adapters).
• Install the modules without accessing PyPI:

  pip install --no-index --find-links=. xlrd xlsxwriter
  

• Create a simple test script to exercise core functionality:

  # Test xlrd: Read a local Excel file
  import xlrd
  workbook = xlrd.open_workbook("test_input.xlsx")
  sheet = workbook.sheet_by_index(0)
  print(f"Read cell value: {sheet.cell_value(0, 0)}")
  
  # Test xlsxwriter: Write to a new Excel file
  import xlsxwriter
  workbook = xlsxwriter.Workbook("test_output.xlsx")
  worksheet = workbook.add_worksheet()
  worksheet.write('A1', 'Hello World')
  workbook.close()
  print("Wrote test Excel file successfully")
  

• Run the script. If it completes without network-related errors (like "connection refused" or "cannot reach PyPI"), the modules don't require external network access.

2. Network Traffic Monitoring #

Use packet capture tools to watch for any outbound requests while using the modules:

• On Linux/macOS, use tcpdump to filter non-local traffic:

  tcpdump -i any dst not 127.0.0.1 and dst not 192.168.0.0/16  # Adjust subnet to match your internal network
  

• On Windows, use Wireshark with a filter like not ip.addr == 127.0.0.1 and not ip.addr matches 192.168.*
• Run your test script while the capture is active. If no outbound packets show up, the modules aren't making external calls.

3. Static Code Analysis #

Dig into the module source code to confirm no network-related libraries are used:

• Locate the installed module directories (use pip show xlrd and pip show xlsxwriter to get the paths).
• Search for network-related keywords in the codebase:

  grep -r "socket\|requests\|urllib\|http\|https" /path/to/xlrd /path/to/xlsxwriter
  

• xlrd and xlsxwriter are designed for local Excel processing—you won't find any references to network calls here. Their code focuses entirely on parsing/generating Excel file formats locally.

4. Isolated Sandbox Testing #

Use a restricted environment to block all outbound traffic:

• Create a Docker container with no network access:

  docker run --network none -v $(pwd):/app -w /app python:3.11 bash
  

• Inside the container, install the local module wheels (copy them into the volume first) and run your test script.
• Alternatively, use iptables to block all outbound traffic on a test machine:

  iptables -P OUTPUT DROP
  

  Run the script—if it works without issues, the modules don't need external network access.

Bonus Context #

Just to reassure you: xlrd is a pure-parsing library that reads Excel files directly from disk, and xlsxwriter generates Excel files locally without any external dependencies. Neither module has a reason to initiate network calls, but these tests will give your security team concrete proof.

内容的提问来源于stack exchange，提问作者arcee123