mbytes.sh

 #!/usr/bin/env bash

# ==============================
# MBYTES 2.0
# Author: Irving SA (Comandre-ex)
# Description: File Magic Number Analyzer & Modifier
# ==============================

VERSION="2.0"

# ===== Colors =====
greenColour="\e[0;32m\033[1m"
endColour="\033[0m\e[0m"
redColour="\e[0;31m\033[1m"
blueColour="\e[0;34m\033[1m"
yellowColour="\e[0;33m\033[1m"
grayColour="\e[0;37m\033[1m"

# ===== Magic Numbers =====
declare -A magic_numbers_list=(
    ["JPEG"]="FFD8FF"
    ["PNG"]="89504E470D0A1A0A"
    ["GIF"]="47494638"
    ["PDF"]="25504446"
    ["ZIP"]="504B0304"
    ["RAR"]="526172211A0700"
    ["MP3"]="FFFB"
    ["WAV"]="52494646"
    ["EXE"]="4D5A"
    ["TAR"]="7573746172"
)

trap ctrl_c INT
tput civis

function ctrl_c() {
    echo -e "\n${grayColour}Exiting...${endColour}"
    tput cnorm
    exit 0
}

# ===== Backup =====
function backup_file() {
    cp "$file" "$file.bak"
    echo -e "${blueColour}[+] Backup creado: $file.bak${endColour}"
}

# ===== Detect =====
function detect_magic() {

    if [[ ! -f "$file" ]]; then
        echo -e "${redColour}[-] Archivo no encontrado${endColour}"
        exit 1
    fi

    header=$(xxd -p -l 8 "$file" | tr '[:lower:]' '[:upper:]')

    for type in "${!magic_numbers_list[@]}"; do
        if [[ $header == ${magic_numbers_list[$type]}* ]]; then
            echo -e "${greenColour}[+] Tipo detectado: $type${endColour}"
            return
        fi
    done

    echo -e "${yellowColour}[!] Tipo desconocido${endColour}"
}

# ===== Modify =====
function modify_magic() {

    if [[ -n "$custom_magic" ]]; then
        hex_string=$custom_magic
    else
        hex_string=${magic_numbers_list[$type]}
    fi

    if [[ -z "$hex_string" ]]; then
        echo -e "${redColour}[-] Tipo no soportado${endColour}"
        exit 1
    fi

    formatted_hex=""
    for (( i=0; i<${#hex_string}; i+=2 )); do
        formatted_hex+="\x${hex_string:i:2}"
    done

    backup_file

    echo -ne "$formatted_hex" | dd of="$file" bs=1 count=$((${#hex_string}/2)) conv=notrunc 2>/dev/null

    echo -e "${greenColour}[+] Magic number modificado correctamente${endColour}"
}

# ===== Scan Directory =====
function scan_directory() {

    echo -e "${yellowColour}[+] Escaneando directorio...${endColour}"

    for f in *; do
        [[ -f "$f" ]] || continue

        header=$(xxd -p -l 4 "$f" 2>/dev/null | tr '[:lower:]' '[:upper:]')
        extension="${f##*.}"

        case $extension in
            jpg|jpeg) expected="FFD8FF" ;;
            png) expected="89504E47" ;;
            pdf) expected="25504446" ;;
            zip) expected="504B0304" ;;
            *) continue ;;
        esac

        if [[ $header != $expected* ]]; then
            echo -e "${redColour}[!] Posible archivo camuflado: $f${endColour}"
        fi
    done
}

# ===== Help =====
function helpPanel() {
    echo -e "\n${blueColour}MagicBytes v${VERSION}${endColour} — Magic Number Analyzer & Modifier\n"
    echo -e "${grayColour}Uso:${endColour} $0 [opciones]\n"
    echo -e "  ${yellowColour}-f${endColour} <archivo>    Archivo objetivo"
    echo -e "  ${yellowColour}-t${endColour} <tipo>       Tipo de magic number a inyectar (ej: JPEG, PNG, PDF)"
    echo -e "  ${yellowColour}-m${endColour} <hex>        Magic number hexadecimal personalizado (ej: FFD8FF)"
    echo -e "  ${yellowColour}-d${endColour}              Detectar el tipo real del archivo"
    echo -e "  ${yellowColour}-s${endColour}              Escanear directorio actual (extension vs magic number)"
    echo -e "  ${yellowColour}-h${endColour}              Mostrar este panel de ayuda\n"
    echo -e "${grayColour}Tipos soportados:${endColour} JPEG PNG GIF PDF ZIP RAR MP3 WAV EXE TAR\n"
    echo -e "${grayColour}Ejemplos:${endColour}"
    echo -e "  $0 -d -f archivo.jpg"
    echo -e "  $0 -f shell.php -t JPEG"
    echo -e "  $0 -f archivo.bin -m FFD8FFE0"
    echo -e "  $0 -s\n"
}

# ===== Arguments =====
while getopts ":f:t:m:dsh" arg; do
    case $arg in
        f) file=$OPTARG ;;
        t) type=$OPTARG ;;
        m) custom_magic=$OPTARG ;;
        d) detect=1 ;;
        s) scan=1 ;;
        h) helpPanel; exit 0 ;;
    esac
done

if [[ $scan == 1 ]]; then
    scan_directory
elif [[ $detect == 1 ]]; then
    if [[ -z "$file" ]]; then
        echo -e "${redColour}[-] Debes especificar un archivo con -f${endColour}"
        exit 1
    fi
    detect_magic
elif [[ -n "$file" && (-n "$type" || -n "$custom_magic") ]]; then
    modify_magic
else
    helpPanel
fi

tput cnorm