Introduction
This is a small binary that spawns a console on the `/firmadyne/ttyS1`` special character device at system startup. In conjunction with a patched filesystem and instrumented kernel, this allows an analyst to interact with an emulated firmware image through QEMU, since some firmware images do not spawn a terminal on the primary serial console.
Usage
First, create the special character device within the firmware image:
mknod -m 666 /firmadyne/ttyS1 c 4 65
Next, copy this binary into the firmware image:
cp console /firmadyne/console
Then, it will be automatically executed by the instrumented kernel during system
bootup after the 4th execve() call if the firmadyne.execute kernel parameter
is set to 1 (this is the default).
Notes
ARM Serial Devices
QEMU ARM guests do not currently support multiple serial consoles. You can build qemu with this patch or try the PANDA emulator to run ARM guests with multiple serial devices.
Shell Usability
If you start a serial console with -serial stdio, pressing ctrl-C, ctl-Z, or so on will be sent to the emulator itself. If you wish for these commands to be sent to the guest, you can use -nographic (if running with a single serial console), or -serial telnet:localhost:4321,noserver,nowait -serial stdio to expose a root shell on ttyS1 via telnet and the standard guest output on stdio. Then you can connect to the root console via telnet (with telnet localhost 4321) and press ctrl-C, ctrl-Z and have these commands sent directly into the guest.