How can i execute text as code from server to client on shell script (netcat)

Question

I have two files, client.sh and server.sh, all the necessary data is on the server, which is sent to the client using netcat, the client just get these data and display it to the end user, the problem is when the server send some multiline code, the client just receive it as text and display on screen

client.sh

ip=127.0.0.1
client_port=5678
server_port=8765

while :
do
        # Request the menu from the server
        echo menu > /dev/tcp/"$ip"/"$server_port"
        # Waits the server response
        nc -l $porta_cliente
done

server.sh

ip=127.0.0.1
porta_cliente=5678
porta_servidor=8765

while :
do
        nc -vv -l $porta_servidor > logservidor
        echo "Texto recebido: "`cat logservidor` # LOG
        case `cat logservidor` in
        "splash")
                echo "dialog --stdout --msgbox 'SPLASH' 0 0" > /dev/tcp/"$ip"/"$porta_c$
        ;;
        "menu_inicial")
                nc $ip $porta_cliente <<-EOF
                        dialog --stdout --backtitle 'Bem vindo ao SEPA 0.1' --title 'Me$
                        Cadastrar 'Criar um novo usuário' \
                        Entrar 'Fazer login com sua conta' \
                        Sair 'Encerrar o SEPA'

                        # Caso o usuário selecione Cancelar, a execução do script será $
                        if [ $? -eq 0 ]; then
                                echo SUCESSO
                        else
                                rm resposta_servidor dados_digitados 2> /dev/null
                                clear
                                exit
                        fi
                EOF
        ;;
        "menu_principal")
                echo "dialog --msgbox 'MENU_PRINCIPAL' 0 0" > /dev/tcp/"$ip"/"$porta_cl$
        ;;
        *)
                dialog --msgbox 'WTF?!' 0 0 > /dev/tcp/"$ip"/"$porta_cliente"
        ;;
        esac
done

Answer 1

You can pipe the output of netcat into the shell

nc -l $porta_cliente | sh

however, on a socket with no authentication whatsoever, be extremely careful as this could allow anyone to execute arbitrary code on the client machine.

This method is extremely bad practice and you should consider different approaches.

Answer 2

You can also redirect your text from the netcat connection to a file, and then execute it as a command, using source

Example:

nc -l 8765 > command
source command