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---
title: Consoles
---
# Serial
## Disable serial console
The serial console should be disabled to prevent an attacker from accessing this
powerful interface.
<!-- section-config -->
Domain | `Config` name | `Value`
------------------------ | ---------------------------- | -------
Kernel-Consoles-Serial-1 | `CONFIG_SERIAL_8250` | `n`
Kernel-Consoles-Serial-2 | `CONFIG_SERIAL_8250_CONSOLE` | `n`
Kernel-Consoles-Serial-3 | `CONFIG_SERIAL_CORE` | `n`
Kernel-Consoles-Serial-4 | `CONFIG_SERIAL_CORE_CONSOLE` | `n`
<!-- end-section-config -->
--------------------------------------------------------------------------------
## Bake-in the kernel command-line
The kernel command-line is used to control many aspects of the booting kernel,
and is prone to tampering as they are passed in RAM with little to no reverse
validation on these parameters. To prevent this type of attack, the kernel shall
be configured to ignore commands line arguments, and use pre-configured (compile
time) options instead.
Set the kernel command line in the `CONFIG_CMDLINE KConfig` item and then pass
no arguments from the bootloader.
<!-- section-config -->
Domain | `Config` name | `Value`
----------------------------- | ------------------------- | -----------------------------------
Kernel-Consoles-CommandLine-1 | `CONFIG_CMDLINE_BOOL` | `y`
Kernel-Consoles-CommandLine-2 | `CONFIG_CMDLINE` | `"insert kernel command line here"`
Kernel-Consoles-CommandLine-3 | `CONFIG_CMDLINE_OVERRIDE` | `y`
<!-- end-section-config -->
It is recommended that any per-device settings (e.g: MAC addresses, serial
numbers, etc.) be stored and accessed from read-only memory (or files), and that
any such parameters be verified (signature checking) prior to their use.
--------------------------------------------------------------------------------
## Disable KGDB
The Linux kernel supports KGDB over USB and console ports. These mechanisms are
controlled by the `kgdbdbgp` and `kgdboc` kernel command-line parameters. It is
important to ensure that no shipping product contains a kernel with KGDB
compiled-in.
<!-- section-config -->
Domain | `Config` name | `Value`
---------------------- | ------------- | -------
Kernel-Consoles-KDBG-1 | `CONFIG_KGDB` | `n`
<!-- end-section-config -->
--------------------------------------------------------------------------------
## Disable magic sysrq support
On a few architectures, you can access a powerful debugger interface from the
keyboard. The same powerful interface can be present on the serial console
(responding to serial break) of Linux on other architectures. Disable to avoid
potentially exposing this powerful backdoor.
<!-- section-config -->
Domain | `Config` name | `Value`
----------------------- | -------------------- | -------
Kernel-Consoles-SysRQ-1 | `CONFIG_MAGIC_SYSRQ` | `n`
<!-- end-section-config -->
--------------------------------------------------------------------------------
## Disable support for binary formats other than ELF
This will make possible to plug wrapper-driven binary formats into the kernel.
It enables support for binary formats other than ELF. Providing the ability to
use alternate interpreters would assist an attacker in discovering attack
vectors.
<!-- section-config -->
Domain | `Config` name | `Value`
------------------------------ | -------------------- | -------
Kernel-Consoles-BinaryFormat-1 | `CONFIG_BINFMT_MISC` | `n`
<!-- end-section-config -->
|
