server.sh

#!/bin/bash

# Function to generate RSA key pair
# ARGS: 1->Private key file name 2->Public key file name
function gen_key()
{
	if ! [ -d "._key" ]
	then
		mkdir ._key
	fi
	openssl genpkey -algorithm RSA -out ._key/"$1" >& /dev/null
	openssl pkey -pubout -in ._key/"$1" -out ._key/"$2"
}

# Function to encrypt a message using RSA public key
# ARGS: 1->message 2->public key
function crypt()
{
	echo -n "$1" | openssl pkeyutl -encrypt -pubin -inkey ._key/"$2" | base64 -w 0
}

# Function to decrypt a message using RSA private key
# ARGS: 1->message 2->private key
function decrypt()
{
  echo -n "$1" | base64 -d | openssl pkeyutl -decrypt -inkey ._key/"$2"
}

# Function to send an encrypted message using the recipient's public key
# ARGS: 1->Public key file name 2->Message
function send()
{
	echo "$(crypt "$2" "$1")"
}

# Function to send the public key to the recipient
# ARGS: 1->Key to send
function send_key()
{
	echo "$(printf '%q' "$(cat ._key/"$1")")"
}

# Function to get the encrypted password
function get_crypt_passwd()
{
	echo -n "$(cat ./._key/passwd.crypt)"
}

# Function to set the encrypted password
# ARGS: 1->New encrypted password 2->public key to encrypt
function set_crypt_passwd()
{
	crypt "$1" "$2" > ._key/passwd.crypt
}

# Function to test the entered password
# ARGS: 1->Password to test
function is_passwd()
{
	if [[ "$(decrypt "$(get_crypt_passwd)" server.pem)" == "$1" ]]
	then
		echo ":§:0"
		return 0
	else
		echo ":§:1"
		return 1
	fi
}

# Function to change the password
function set_passwd()
{
	echo -n "Please enter the password : "
	read -r -s newpasswd
	echo
	echo -n "Please retype the password : "
	read -r -s retype
	echo
	if [ "$newpasswd" = "$retype" ]
	then
		set_crypt_passwd "$newpasswd" server.pub
		echo ">>>Password changed"
		return 0
	else
		echo -e "Passwords do not match\n>>>Password unchanged"
		return 1
	fi
}

# Function to parse the input and execute commands
# ARGS: 1->Input to parse
function parser()
{
	local input="$1"
  if echo "$input" | grep -q -E "BEGIN PUBLIC KEY" &> /dev/null
  then
    input=${input#"$'"} && input=${input%"'"}
    echo -e "$input" > ._key/client.pub
    send_key server.pub
  else
    if [ -n "$input" ]
    then
      input=$(decrypt "$input" server.pem)
      if [[ ${input:0:3} == ":§:" ]]
      then
        input=${input#":§:"}
        echo -e "\e[31m@server\e[0m:\e[34m$(date)\e[0m! $input" >&2
      else
        if ! $(cat ._key/connect)
        then
          command=$(eval "$input")
        else
          command=$({ cd "$(cat "$userPath")" && eval "$input && pwd > \"$userPath\"" 3>&2 2>&1 1>&3 | cut -f3- -d':' | sed 's/^.//'| sed 's/^/\x1b[31m>>>Error\x1b[0m: /';} 2>&1)
        fi
        send client.pub "$command"
      fi
    fi
  fi
}

# Function to handle server operations
function server()
{
	while IFS=  read -r line;
	do
		parser "$line"
	done
}

# Check if the FIFO file exists and remove it if it does
if test -e "./.fifo"
then
	rm ./.fifo
fi

# Create a FIFO file
mkfifo ./.fifo

echo ">>>Initialization"

# Parse arguments
ip=localhost
port=8080

while [[ $# -gt 0 ]]; do
    case "$1" in
      -n)	#Set a new password for the server
        gen_key server.pem server.pub
        until set_passwd
        do
          true
        done
        ;;
      -i)	#Set a specific ip for the server
        shift
        ip="$1"
        ;;
      -p)	#Set a specific port for the server
        shift
        port="$1"
        ;;
    esac
    shift
done

# Check if there is existing keys and password
if ! [ -d "._key/" ]
then
	gen_key server.pem server.pub
	until set_passwd
	do
		true
	done
fi

echo ">>>Server initialized"

# Temp file to store the user actual path
userPath=$(mktemp)

# Continuously listen for incoming connections and process them
while true
do
	  nc -l "$ip" "$port" < ./.fifo | server > ./.fifo
done