Aircrack-ng Unable To Put Multiple Interfaces Into Monitor Mode On NixOS

by James Vasile 73 views

Hey everyone! Today, we're diving deep into a tricky issue I encountered while working with Aircrack-ng on NixOS. Specifically, I ran into a bug where I couldn't put more than one wireless interface into monitor mode. This is a major roadblock when you're trying to perform network testing or security audits, especially when you need to monitor multiple channels simultaneously.

In this article, we'll break down the problem, explore the steps I took to reproduce it, and discuss potential solutions. Whether you're a cybersecurity enthusiast, a network admin, or just someone curious about NixOS, this deep dive will provide you with valuable insights and practical advice. So, let's jump right in!

Understanding the Aircrack-ng Monitor Mode Issue

When working with wireless network analysis and security, the ability to put multiple interfaces into monitor mode is crucial. This mode allows your network card to capture all wireless traffic in the vicinity, regardless of the network it's associated with. Tools like Aircrack-ng rely on this functionality to perform tasks such as packet sniffing, network analysis, and penetration testing. However, on NixOS, I discovered a perplexing issue: I could only enable monitor mode on one interface at a time.

The Problem in Detail

The core of the problem lies in the interaction between Aircrack-ng, the network drivers, and the way NixOS manages network interfaces. The sequence of events goes something like this:

  1. I would start by setting one interface (let's say wlan1) to monitor mode using the command sudo aircrack-ng start wlan1.
  2. The command would execute successfully, and wlan1 would enter monitor mode, allowing me to capture wireless packets.
  3. However, when I attempted to set another interface (e.g., wlan0) to monitor mode using the same command (sudo aircrack-ng start wlan0), it would fail. No error messages were displayed, but the interface simply wouldn't switch to monitor mode.
  4. Rebooting the system seemed to offer a temporary workaround. After a reboot, I could set a different interface to monitor mode, but the previously configured interface would then be unable to enter monitor mode.

This behavior was incredibly frustrating, especially when I needed to monitor multiple wireless channels simultaneously for tasks like evil twin attacks or comprehensive network analysis. I needed a reliable solution to ensure that all my wireless interfaces could operate in monitor mode concurrently.

Why This Matters

The inability to use multiple interfaces in monitor mode severely limits the scope and effectiveness of wireless network analysis. Imagine trying to monitor a busy wireless environment where networks operate on different channels. With only one interface in monitor mode, you're essentially blind to the traffic on other channels. This is akin to trying to listen to a conversation while only hearing every other word – you miss crucial context and details.

For cybersecurity professionals, this limitation can be a deal-breaker. Tasks such as identifying rogue access points, detecting man-in-the-middle attacks, and performing comprehensive network audits require the ability to monitor multiple channels simultaneously. Without this capability, you're only getting a partial view of the wireless landscape, leaving potential vulnerabilities and threats undetected.

Steps to Reproduce the Bug

To ensure that others could replicate the issue and to better understand the underlying cause, I meticulously documented the steps to reproduce the bug. Here’s the breakdown:

  1. Boot into NixOS: Start with a clean boot of your NixOS system. This ensures that there are no lingering configurations or states affecting the outcome.
  2. Identify Wireless Interfaces: Use the iw dev command to list all available wireless interfaces. Note their names (e.g., wlan0, wlan1). This command provides detailed information about each interface, including its current mode, channel, and other parameters.
  3. Stop NetworkManager: Before using Aircrack-ng, it’s often necessary to stop the NetworkManager service, as it can interfere with the process. Execute the command sudo systemctl stop NetworkManager. This prevents NetworkManager from automatically configuring or managing the wireless interfaces, giving Aircrack-ng more control.
  4. Set the First Interface to Monitor Mode: Use the command sudo aircrack-ng start <interface_name>, replacing <interface_name> with the name of one of your wireless interfaces (e.g., wlan0). This command attempts to put the specified interface into monitor mode.
  5. Verify Monitor Mode: Use iw dev again to confirm that the first interface is indeed in monitor mode. Look for the type monitor entry in the output for the interface.
  6. Attempt to Set a Second Interface to Monitor Mode: Now, try to set another interface to monitor mode using the same command, but with the name of the second interface (e.g., sudo aircrack-ng start wlan1).
  7. Observe the Failure: Check the output and use iw dev to verify the status of the second interface. You'll likely find that it has not switched to monitor mode.

By following these steps, I consistently reproduced the bug, confirming that it wasn't an isolated incident. This systematic approach was crucial for understanding the problem and communicating it effectively to others.

Analyzing the Log Output

The log output provided some clues, but it wasn't immediately clear what was causing the issue. Let's break down the relevant parts:

>>>>>>Hi Masrkai! ~/Programs/airgeddon
21:14:40[masrkai_NixOS]$ sudo systemctl stop NetworkManager
[sudo] password for masrkai: 
>>>>>>Hi Masrkai! ~/Programs/airgeddon
21:14:51[masrkai_NixOS]$ iw dev
phy#1
        Interface wlan1
                ifindex 4
                wdev 0x100000001
                addr d0:37:45:82:f5:fa
                type monitor
                channel 1 (2412 MHz), width: 20 MHz (no HT), center1: 2412 MHz
                txpower 20.00 dBm
                multicast TXQ:
                        qsz-byt qsz-pkt flows   drops   marks   overlmt hashcol tx-bytes        tx-packets
                        0       0       0       0       0       0       0       0               0
phy#0
        Interface wlan0
                ifindex 3
                wdev 0x1
                addr 3c:0a:f3:12:e3:41
                type managed
                txpower 20.00 dBm
                multicast TXQ:
                        qsz-byt qsz-pkt flows   drops   marks   overlmt hashcol tx-bytes        tx-packets
                        0       0       0       0       0       0       0       0               0
>>>>>>Hi Masrkai! ~/Programs/airgeddon
21:16:04[masrkai_NixOS]$ sudo airmon-ng start wlan0

Found 1 processes that could cause trouble.
Kill them using 'airmon-ng check kill' before putting
the card in monitor mode, they will interfere by changing channels
and sometimes putting the interface back in managed mode

    PID Name
   1478 wpa_supplicant

PHY     Interface       Driver          Chipset

null
                ??????          non-mac80211 device? (report this!)
null    wlan0
                ??????          non-mac80211 device? (report this!)
phy1    wlan1           rtl8xxxu        TP-Link TL-WN722N v2/v3 [Realtek RTL8188EUS]

>>>>>>Hi Masrkai! ~/Programs/airgeddon
21:16:16[masrkai_NixOS]$ sudo airmon-ng check kill

Killing these processes:

    PID Name
   1478 wpa_supplicant

>>>>>>Hi Masrkai! ~/Programs/airgeddon
21:16:25[masrkai_NixOS]$ sudo airmon-ng start wlan0


PHY     Interface       Driver          Chipset

null
                ??????          non-mac80211 device? (report this!)
null    wlan0
                ??????          non-mac80211 device? (report this!)
phy1    wlan1           rtl8xxxu        TP-Link TL-WN722N v2/v3 [Realtek RTL8188EUS]

Key Observations

  1. Stopping NetworkManager: The first step was to stop NetworkManager to prevent it from interfering with the interface configuration. This is a common practice when using Aircrack-ng.
  2. Interface Status: The iw dev command showed that wlan1 was already in monitor mode. This confirmed that the initial attempt to set one interface to monitor mode was successful.
  3. Airmon-ng Output: When trying to set wlan0 to monitor mode, airmon-ng displayed some concerning messages:
    • Found 1 processes that could cause trouble. This is normal, and the script correctly identified wpa_supplicant as a potential conflict.
    • ?????? non-mac80211 device? (report this!) This message is more worrying. It suggests that airmon-ng might be having trouble identifying the driver or chipset for wlan0. This could be a crucial clue.
  4. No Error Message: Despite the warning, airmon-ng didn't throw a specific error message, which made debugging more challenging.

Potential Causes

Based on the log output, here are some potential causes for the issue:

  • Driver Compatibility: The non-mac80211 device? message suggests that there might be a problem with the driver for wlan0. It’s possible that the driver doesn't fully support monitor mode or that airmon-ng isn't correctly recognizing it.
  • Conflicting Processes: Although wpa_supplicant was killed, there might be other processes or services interfering with the interface configuration.
  • NixOS Configuration: There could be specific NixOS configurations or settings that are preventing multiple interfaces from entering monitor mode simultaneously.

Troubleshooting and Potential Solutions

Now that we've identified the problem and analyzed the log output, let's explore some troubleshooting steps and potential solutions.

1. Driver Issues

  • Check Driver Support: The first step is to verify that the driver for your wireless interface (wlan0 in this case) fully supports monitor mode. You can consult the driver documentation or online resources to confirm this.
  • Update Drivers: If the driver is outdated, try updating it to the latest version. In NixOS, this typically involves updating your Nixpkgs channel and rebuilding your system configuration. This ensures that you're using the most recent and potentially bug-fixed version of the driver.
  • Try a Different Driver: If updating doesn't help, consider trying a different driver, if one is available. Sometimes, an alternative driver might offer better compatibility or performance.

2. Conflicting Processes

  • Identify Conflicting Processes: Use tools like ps, top, or htop to identify any processes that might be interfering with the wireless interfaces. Look for processes related to networking, such as NetworkManager, wpa_supplicant, or other network management tools.
  • Kill Conflicting Processes: If you find any conflicting processes, try killing them using the kill command. Be cautious when killing processes, as some might be essential for system operation. It’s often best to stop services using systemctl stop <service_name> rather than directly killing processes.

3. NixOS Configuration

  • NetworkManager Configuration: Examine your NetworkManager configuration files to ensure that they aren't interfering with monitor mode. Sometimes, specific settings in NetworkManager can prevent interfaces from entering monitor mode.
  • NixOS Networking Modules: Review your NixOS system configuration to see if any networking modules are causing conflicts. Pay close attention to modules related to wireless configuration, such as wpa_supplicant or iwd.
  • Kernel Modules: Check if the necessary kernel modules for monitor mode are loaded. Use the lsmod command to list loaded modules and ensure that the modules for your wireless drivers and monitor mode are present.

4. Aircrack-ng Configuration

  • Airmon-ng Usage: Double-check that you're using airmon-ng correctly. Refer to the documentation or man pages for the tool to ensure that you're using the correct commands and options.
  • Dependencies: Ensure that all the necessary dependencies for Aircrack-ng are installed. Missing dependencies can sometimes lead to unexpected behavior.

5. Kernel Issues

  • Kernel Version: In rare cases, there might be issues with the kernel itself. Consider trying a different kernel version to see if it resolves the problem. NixOS makes it relatively easy to switch between kernel versions.

Workaround and Temporary Solutions

While investigating the root cause, I also explored some workarounds and temporary solutions to keep my workflow going:

  • Rebooting: As mentioned earlier, rebooting the system allowed me to set one interface to monitor mode, but it was a temporary fix. This is not ideal but can be used in emergency situations.
  • Using One Interface at a Time: Another workaround was to focus on one interface at a time, performing the necessary tasks before switching to another interface. This is time-consuming and limits the scope of analysis but can be a viable option for specific tasks.
  • Virtualization: Using a virtual machine with a dedicated wireless adapter can sometimes bypass the issue. This involves passing the wireless adapter directly to the VM, giving it full control over the hardware.

Submitting a Bug Report

After thoroughly investigating the issue, I submitted a bug report to the Nixpkgs repository. This is crucial for ensuring that the problem is addressed by the NixOS community and that a permanent solution is developed. Here’s why submitting a bug report is important:

  • Community Collaboration: Bug reports allow other users to confirm the issue and provide additional information, helping developers understand the problem better.
  • Fixing the Root Cause: By reporting the bug, you're contributing to the long-term stability and reliability of NixOS and the Aircrack-ng package.
  • Transparency: Bug reports provide a transparent record of issues and their resolutions, benefiting the entire community.

In my bug report, I included the following information:

  • Nixpkgs Version: The specific version of Nixpkgs I was using (Stable 25.05).
  • Description of the Bug: A clear and concise description of the issue, including the steps to reproduce it.
  • Steps to Reproduce: A detailed list of steps that others can follow to replicate the bug.
  • Expected Behavior: What I expected to happen (both interfaces entering monitor mode).
  • Log Output: Relevant log output from the commands I ran.
  • Additional Context: Any other relevant information, such as the system metadata and hardware details.

Conclusion: The Ongoing Quest for a Solution

The issue of being unable to put multiple interfaces into monitor mode with Aircrack-ng on NixOS is a frustrating one, but it's also an opportunity to dive deep into the intricacies of network configuration and driver compatibility. By systematically troubleshooting, analyzing logs, and submitting a detailed bug report, we can work towards a permanent solution.

While temporary workarounds can help in the short term, the ultimate goal is to identify and fix the root cause of the problem. Whether it's a driver issue, conflicting processes, or a NixOS configuration quirk, resolving this bug will benefit not only me but also the entire NixOS community.

So, stay tuned as we continue to explore this issue and hopefully find a definitive fix. And remember, if you encounter similar problems, don't hesitate to dive deep, document your findings, and share your experiences with the community. Together, we can make NixOS an even more robust and versatile platform for network analysis and security.