voider

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Direct IP Calls - IP agnostic.

• SRTP is natively supported by the phones.
• The private phone number on the phone itself is always: 172.16.19.85/30
• The gateway is always: 172.16.19.86/30.

Note: Agnostic in the sense that on the good old phones, you did not know who was calling you, because old phones don't have a display. So it's I got to hear it to believe it. You will see the call incoming from a specific fake IP address, but you may or may not map that to the caller's IP address. So perhaps "anonymous phone calls" is a better term. There is a "do not disturb" feature which you can use; the phone stays quiet, and the caller gets a "busy" signal. :)

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Disclaimer

• You need to already be using a Linux machine to set this up.
• You need to know how to SSH into a Linux machine to set this up.

After all is done, this Raspberry Pi will be a device to be thought of like the good old phones, as seen in the picture. This Raspberry Pi will be a dedicated machine only for the phone. This software is based on the assumption that source ports are not filtered/changed outwards, which is the case for most retail routers.

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How to Install

1. Flash Alpine Linux:

   dd if=alpine-rpi-3.20.3-aarch64.img of=/dev/sdX bs=4M

2. Run setup-alpine.

3. Setup another user other than root; DHCP on eth0 is fine.

4. Choose UTC as the timezone and chrony. This is crucial so that all devices are synced on the same timeline.

5. Use the same micro SD card for the OS (type mmcblk0).

   • Make sure to have an SSH cert to log in to your Raspberry Pi before continuing.
   • Log in with that cert into the Raspberry Pi a couple of times, or else you might get locked out once setup is done.

6. Clone the repository:

   git clone https://github.com/slave-blocker/voider.git

7. Navigate to the directory:

   cd voider/voider

8. As user:

   doas ./install.sh

9. As root:

   • (Let it be WireGuard, let Quad9, no to IPv6, and at the end, don't reboot; the script will do that for you.)

   ./install_as_root.sh

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How to Setup

1. Navigate to the configuration directory:

   ~/$ cd .config/voider

2. Choose interfaces:

   doas ./main.sh

   • (This will set up /etc/network/interfaces and then reboot.)
   • (The phone needs to be connected already with the Raspberry Pi.)

3. After this reboot:

   ~/$ cd .config/voider

4. Run the main script again:

   doas ./main.sh

   This will set up the SFTP connections over Tor. Once executing doas ./main.sh returns the available options, you should be good to go.

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How to Use

1. Buy a Grandstream IP phone that has a Direct IP call feature (tested with GXP1610).

2. Install voider on a Raspberry Pi or any Linux machine.

3. Connect a Grandstream phone to the USB dongle of your machine.

4. Run:

   doas ./main.sh

   to create new clients or to connect to servers.

5. Once connections exist to servers or clients, go to the phone and DIRECT IP CALL:

   • Clients:

     • 10.1.2.1 ---> 1st client
     • 10.1.3.1 ---> 2nd client
     • 10.1.4.1 ---> 3rd client
     • etc.

   • Servers:

     • 10.2.1.1 ---> 1st server
     • 10.3.1.1 ---> 2nd server
     • 10.4.1.1 ---> 3rd server
     • etc.

Out of the box, Grandstream phones should use RTP. To enable SRTP, access your phone's web interface and go to Account -> Audio Settings and set SRTP to Enabled and Forced.

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Important Note

A server passes its certificate for the SFTP over Tor, allowing its clients to connect with torsocks. A client with that certificate can only enter the Raspberry Pi via SFTP.

• The only login shell available for this user, called "self," is: /bin/false.
• Once logged into the SFTP chroot directory /var/sftp/self/, the user can only write to the files they see with ls, and only up to 2KB.
• The number of processes available for "self" on the server is 8 (should be 2 per SFTP connection), meaning only 4 SFTP connections can happen at the same time.

This is not a problem since Torify SFTP for read and write operations typically only takes a few seconds.

Making voider mobile means you can just unplug it and turn it on in another house behind a different router with no configuration on your part. This feature is coming soon™.

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Contact

Please do contact me for critiques, suggestions, questions, kudos, and even mobbing attempts are welcome.

Remember, if your hardware is backdoored anyway, backdoored you are...

@ IRC: monero-pt

Special thanks to Andreas Hein!

A donation is the best nation!

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MONERO