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cbc翻转

Word count: 943 / Reading time: 5 min
2018/05/08 Share

CBC翻转攻击

参考链接:

  1. https://blog.csdn.net/csu_vc/article/details/79619309
  2. http://wooyun.jozxing.cc/static/drops/tips-7828.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">;
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Login Form</title>
<link href="static/css/style.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="static/js/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$(".username").focus(function() {
$(".user-icon").css("left","-48px");
});
$(".username").blur(function() {
$(".user-icon").css("left","0px");
});
$(".password").focus(function() {
$(".pass-icon").css("left","-48px");
});
$(".password").blur(function() {
$(".pass-icon").css("left","0px");
});
});
</script>
</head>
<?php
define("SECRET_KEY", file_get_contents('/root/key'));
define("METHOD", "aes-128-cbc");
session_start();
function get_random_iv(){
$random_iv='';
for($i=0;$i<16;$i++){
$random_iv.=chr(rand(1,255));
}
return $random_iv;
}
function login($info){
$iv = get_random_iv();
$plain = serialize($info);
$cipher = openssl_encrypt($plain, METHOD, SECRET_KEY, OPENSSL_RAW_DATA, $iv);
$_SESSION['username'] = $info['username'];
setcookie("iv", base64_encode($iv));
setcookie("cipher", base64_encode($cipher));
}
function check_login(){
if(isset($_COOKIE['cipher']) && isset($_COOKIE['iv'])){
$cipher = base64_decode($_COOKIE['cipher']);
$iv = base64_decode($_COOKIE["iv"]);
if($plain = openssl_decrypt($cipher, METHOD, SECRET_KEY, OPENSSL_RAW_DATA, $iv)){
$info = unserialize($plain) or die("<p>base64_decode('".base64_encode($plain)."') can't unserialize</p>");
$_SESSION['username'] = $info['username'];
}else{
die("ERROR!");
}
}
}
function show_homepage(){
if ($_SESSION["username"]==='admin'){
echo '<p>Hello admin</p>';
echo '<p>Flag is $flag</p>';
}else{
echo '<p>hello '.$_SESSION['username'].'</p>';
echo '<p>Only admin can see flag</p>';
}
echo '<p><a href="loginout.php">Log out</a></p>';
}
if(isset($_POST['username']) && isset($_POST['password'])){
$username = (string)$_POST['username'];
$password = (string)$_POST['password'];
if($username === 'admin'){
exit('<p>admin are not allowed to login</p>');
}else{
$info = array('username'=>$username,'password'=>$password);
login($info);
show_homepage();
}
}else{
if(isset($_SESSION["username"])){
check_login();
show_homepage();
}else{
echo '<body class="login-body">
<div id="wrapper">
<div class="user-icon"></div>
<div class="pass-icon"></div>
<form name="login-form" class="login-form" action="" method="post">
<div class="header">
<h1>Login Form</h1>
<span>Fill out the form below to login to my super awesome imaginary control panel.</span>
</div>
<div class="content">
<input name="username" type="text" class="input username" value="Username" onfocus="this.value=\'\'" />
<input name="password" type="password" class="input password" value="Password" onfocus="this.value=\'\'" />
</div>
<div class="footer">
<input type="submit" name="submit" value="Login" class="button" />
</div>
</form>
</div>
</body>';
}
}
?>
</html>

首先确定解密后的字符串:

a:2:{s:8:”username”;s:5:”zdmin”;s:8:”password”;s:5:”12345”}

第一步: 替换cookie中的cipher为反转后的cipher.

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Date : 2018-03-15 11:45:57
# @Author : Mr.zhang(s4ad0w.protonmail.com)
# @Link : http://blog.csdn.net/csu_vc
# username='zdmin'
import base64
import requests
import urllib
iv_raw='DbVDXiIkUNkqwCARqqpYew%3D%3D' #这里填写第一次返回的iv值
cipher_raw='27cekPxVgR5hbiu6ay%2BUfSmepzwYYL%2FTdbN1K3kmrH2EJ%2FqvBtAdKGGqGytHgJXJzNB26ZRX5dwupd885R%2Bwng%3D%3D' #这里填写第一次返回的cipher值
print "[*]原始iv和cipher"
print "iv_raw: " + iv_raw
print "cipher_raw: " + cipher_raw
print "[*]对cipher解码,进行反转"
cipher = base64.b64decode(urllib.unquote(cipher_raw))
#a:2:{s:8:"username";s:5:"zdmin";s:8:"password";s:5:"12345"}
#s:2:{s:8:"userna
#me";s:5:"zdmin";
#s:8:"password";s
#:3:"12345";}
xor_cipher = cipher[0:9] + chr(ord(cipher[9]) ^ ord('z') ^ ord('a')) + cipher[10:] #请根据你的输入自行更改,原理看上面的介绍
xor_cipher=urllib.quote(base64.b64encode(xor_cipher))
print "反转后的cipher:" + xor_cipher

第二步: 第一步执行完,得到一个base64之后的字符串,代入下边的脚本,然后替换cookie中的iv为以下脚本输出的新的iv值。

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Date : 2018-03-15 11:56:20
# @Author : csu_vc(s4ad0w.protonmail.com)
# @Link : http://blog.csdn.net/csu_vc
import base64
import urllib
cipher = 't8hxonGnYZs19dVMEzqeZm1lIjtzOjU6ImFkbWluIjtzOjg6InBhc3N3b3JkIjtzOjU6IjEyMzQ1Ijt9'#填写提交后所得的无法反序列化密文
iv = 'DbVDXiIkUNkqwCARqqpYew%3D%3D'#一开始提交的iv
cipher = urllib.unquote(cipher)
cipher = base64.b64decode(cipher)
iv = base64.b64decode(urllib.unquote(iv))
newIv = ''
right = 'a:2:{s:8:"userna'#被损坏前正确的明文
for i in range(16):
newIv += chr(ord(right[i])^ord(iv[i])^ord(cipher[i])) #这一步相当于把原来iv中不匹配的部分修改过来
print urllib.quote(base64.b64encode(newIv))
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  1. 1. CBC翻转攻击