Replicant

h1. Disabling the Modem

h2. Samsung-RIL devices

h3. Airplane Mode

On Replicant, samsung-RIL currently asks the modem to actually turn off its transmitters by going into a low power mode.

This means that the modem firmware is most probably not off and that its firmware is still running. The modem might even still be able to receive information, as it would enable it to connect back to the network way faster than if it was really off.

The [[ModemIsolationResearch#Powering-off-the-modem|Modem isolation research page]] has more technical details on the issue, and pointers on how to potentially implement a modem power off.

h3. Powering off the modem

Since the modem's firmware is loaded by the CPU on boot, the modem will be nonfunctional if the CPU chooses not to load the modem firmware.  This can be used to achieve a more trustworthy off-like state. It should be noted that while this does reduce attack surface, there may still be ways for the modem to be activated (e.g. if the non-free bootloader running on the CPU sends a firmware to the modem).

To disable the modem on Samsung-RIL devices, follow these steps:

h4. Installation

From your PC, clone the user-scripts repository:

<pre>

git clone https://git.replicant.us/replicant/vendor_replicant-scripts -b replicant-6.0

</pre>

For the next steps, [[ADB]] needs to be set up and [[ADB#Accessing-root-shell|running as root]]. Connect the device to your PC. The scripts are in the @networking/modem@ folder. Run the setup script the folder to push the scripts to the device:

<pre>

cd vendor_replicant-scripts

cd networking/modem

./setup.sh

</pre>

Then disconnect the device. Make sure [[UsageNotes#Enabling-root-access|root access for apps]] is enabled.

h4. Usage

Open a [[UsageNotes#Terminal-emulator|terminal emulator]]. If the terminal is not running as root, you can gain root by running:

<pre>

su

</pre> 

To disable the modem, run the following command:

<pre>

disable_modem.sh

</pre>

It will then reboot the device to disable the modem.

To enable back the modem, run the following command:

<pre>

enable_modem.sh

</pre>

It will then reboot the device to re-enable the modem safely.

h2. Supported devices

h3. Replicant 6.0

As of April 2020, Replicant 6.0 only supports devices with libsamsung-ril or without modems.

Starting from Replicant 6.0 0004 RC1, the scripts are now shipped on the devices that have a modem.

h3. Before Replicant 6.0

Earlier Replicant versions supported devices with other modems protocol as well. This script didn't work on such devices.