Non root backend

[Sharif-bot-cmd]

Pull Request: Non-Root Fallback Backend for Scapy

Overview

This PR introduces a non-root fallback backend for Scapy, allowing basic send and sniff functionality on systems without root privileges.

Currently, Scapy requires raw sockets for full L3 access, which fails on non-root environments. This PR provides:

• NonRootL3Socket: a UDP-based emulation of L3 send/receive.
• sniff_nonroot(): non-root compatible packet capture.
• Automatic backend hook: Scapy falls back to non-root mode if root is unavailable.
• Optional sudo usage: full functionality works if root privileges are present.

This enables Scapy to work in restricted environments, such as:

• Standard user accounts on Linux with or without sudo.
• Docker containers with limited capabilities.
• Educational environments or CI systems where root access is not allowed.

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Implementation Details

• File Added: scapy/arch/linux/nonroot_backend.py
• Hooked in: scapy/all.py
• Tests: tests/test_nonroot.py

Key Features:

1. NonRootL3Socket

   • Uses UDP sockets to emulate L3 packet sending/receiving.
   • Provides .send(pkt) and .recv(timeout) methods compatible with Scapy.
   • Threaded listener for asynchronous packet capture.

2. Non-root Sniffer

   • sniff_nonroot() provides a drop-in alternative for sniff() in non-root mode.
   • Supports count, timeout, and debug logging.

3. Automatic Hook

   • enable_nonroot_backend() automatically sets Scapy’s conf.L3socket to NonRootL3Socket if root is not detected.
   • Uses os.geteuid() when available to detect root privileges.

4. Graceful Fallback

   • If raw sockets fail, no crash occurs.
   • Logs a clear message when running in non-root mode.

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Usage Example

from scapy.all import *

# Root is optional; if not root, non-root backend is used automatically
pkt = IP(dst="127.0.0.1") / UDP(dport=55555) / Raw(load="Hello NonRoot")
s = conf.L3socket(port=55555)
s.send(pkt)

pkts = sniff(count=1, timeout=2)
for p in pkts:
    print(p.summary())

Expected Output (non-root mode):

[*] Non-root fallback active
[IP / UDP 127.0.0.1:55555 > 127.0.0.1:55555 / Raw Hello NonRoot]

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Testing Instructions

1. Clone your fork and checkout the nonroot-backend branch.
2. Run the included test script:

python3 tests/test_nonroot.py

3. Verify that packets are sent and received correctly on 127.0.0.1.
4. Optionally, test with root (sudo) to confirm full Scapy functionality.

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Benefits

• Expands Scapy’s usability to non-root environments.
• Maintains backward compatibility with root-based L3 sockets.
• Provides a safe, predictable fallback for CI/CD pipelines, educational setups, and restricted containers.

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Notes for Reviewers

• UDP-based emulation does not provide full raw L3 capabilities; intended as a compatibility fallback.
• All methods (send, recv, sniff) mimic standard Scapy behavior wherever possible.
• Additional testing on different Linux distros and Python versions is recommended.