Sharing a collection of vulnerabilities in PHP functions

This article mainly shares with you a collection of vulnerabilities in PHP functions, hoping to help everyone.

1. Weak type comparison

##2.MD5 compare vulnerability

Common payloads include

0x01 md5(str)
    QNKCDZO
    240610708
    s878926199a
    s155964671a
    s214587387a
    s214587387a
0x02 sha1(str)
    sha1('aaroZmOk')  
    sha1('aaK1STfY')
    sha1('aaO8zKZF')
    sha1('aa3OFF9m')

if(@md5($_GET['a']) == @md5($_GET['b']))
{
    echo "yes";
}
//http://127.0.0.1/1.php?a[]=1&b[]=2

3.ereg function vulnerability: 00 truncation

ereg ("^[a-zA-Z0-9]+$", $_GET['password']) === FALSE

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Here if $_GET['password'] is an array, the return value is NULL
If it is 123 || asd || 12as || 123%00&&&* *, the return value is true
The rest is false

4.What is $key?

<?php
    print_r(@$_GET); 
    foreach ($_GET AS $key => $value)
    {        print $key."\n";
    }?>

5. Variable coverage

<?php  
    $auth = &#39;0&#39;;  
    // 这里可以覆盖$auth的变量值
    print_r($_GET);    echo "</br>";
    extract($_GET); 
    if($auth == 1){  
        echo "private!";  
    } else{  
        echo "public!";  
    }  
?>

<?php  
    $a=&#39;hi&#39;;    foreach($_GET as $key => $value) {        echo $key."</br>".$value;        $$key = $value;
    }    print "</br>".$a;?>

http://127.0.0.1:8080/test.php?a=12 can achieve the purpose.

6.strcmp

如果 str1 小于 str2 返回 < 0； 如果 str1 大于 str2 返回 > 0；如果两者相等，返回 0。 
先将两个参数先转换成string类型。 
当比较数组和字符串的时候，返回是0。 
如果参数不是string类型，直接return

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<?php
    $password=$_GET[&#39;password&#39;];    if (strcmp(&#39;xd&#39;,$password)) {     echo &#39;NO!&#39;;
    } else{        echo &#39;YES!&#39;;
    }?>

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http://127.0.0.1:8080/test.php?password[]=

7.is_numeric

<?phpecho is_numeric(233333);       # 1echo is_numeric(&#39;233333&#39;);    # 1echo is_numeric(0x233333);    # 1echo is_numeric(&#39;0x233333&#39;);   # 1echo is_numeric(&#39;233333abc&#39;);  # 0?>

8.preg_match

If in progress When matching regular expressions, if there are no restrictions on the beginning and end of the string (^ and $), there may be bypass problems

<?php$ip = &#39;asd 1.1.1.1 abcd&#39;; // 可以绕过if(!preg_match("/(\d+)\.(\d+)\.(\d+)\.(\d+)/",$ip)) {  die(&#39;error&#39;);
} else {   echo(&#39;key...&#39;);
}?>

9.parse_str

A type of time variable coverage

<?php
    $var=&#39;init&#39;;  
    print $var."</br>";
    parse_str($_SERVER[&#39;QUERY_STRING&#39;]);  
    echo $_SERVER[&#39;QUERY_STRING&#39;]."</br>";    print $var;?>

10. String comparison

<?php  
    echo 0 == &#39;a&#39; ;// a 转换为数字为 0    重点注意
    // 0x 开头会被当成16进制54975581388的16进制为 0xccccccccc
    // 十六进制与整数，被转换为同一进制比较
    &#39;0xccccccccc&#39; == &#39;54975581388&#39; ;    // 字符串在与数字比较前会自动转换为数字，如果不能转换为数字会变成0
    1 == &#39;1&#39;;    1 == &#39;01&#39;;    10 == &#39;1e1&#39;;    &#39;100&#39; == &#39;1e2&#39; ;    

    // 十六进制数与带空格十六进制数，被转换为十六进制整数
    &#39;0xABCdef&#39;  == &#39;     0xABCdef&#39;;    echo &#39;0010e2&#39; == &#39;1e3&#39;;    // 0e 开头会被当成数字，又是等于 0*10^xxx=0
    // 如果 md5 是以 0e 开头，在做比较的时候，可以用这种方法绕过
    &#39;0e509367213418206700842008763514&#39; == &#39;0e481036490867661113260034900752&#39;;    &#39;0e481036490867661113260034900752&#39; == &#39;0&#39; ;

    var_dump(md5(&#39;240610708&#39;) == md5(&#39;QNKCDZO&#39;));
    var_dump(md5(&#39;aabg7XSs&#39;) == md5(&#39;aabC9RqS&#39;));
    var_dump(sha1(&#39;aaroZmOk&#39;) == sha1(&#39;aaK1STfY&#39;));
    var_dump(sha1(&#39;aaO8zKZF&#39;) == sha1(&#39;aa3OFF9m&#39;));?>

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11.unset

<?php  $_CONFIG[&#39;extraSecure&#39;] = true;foreach(array(&#39;_GET&#39;,&#39;_POST&#39;) as $method) {    foreach($$method as $key=>$value) {      // $key == _CONFIG
      // $$key == $_CONFIG
      // 这个函数会把 $_CONFIG 变量销毁
      unset($$key);
    }
}if ($_CONFIG[&#39;extraSecure&#39;] == false) {    echo &#39;flag {****}&#39;;
}?>

12.intval()

$var = 5;  
方式1：$item = (string)$var;  
方式2：$item = strval($var);

var_dump(intval('2')) //2  var_dump(intval('3abcd')) //3  var_dump(intval('abcd')) //0 可以使用字符串-0转换，来自于wechall的方法

By the way, intval can be truncated by %00

if($req['number']!=strval(intval($req['number']))){     $info = "number must be equal to it's integer!! ";  
}

13.switch()

<?php
    $i ="abc";  
    switch ($i) {  
    case 0:  
    case 1:  
    case 2:  
    echo "i is less than 3 but not negative";  
    break;  
    case 3:  
    echo "i is 3";  
    } 
?>

14.in_array()

$array=[0,1,2,'3'];  
var_dump(in_array('abc', $array)); //true  var_dump(in_array('1bc', $array)); //true

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15.serialize and unserialize vulnerabilities

这里我们先简单介绍一下php中的魔术方法（这里如果对于类、对象、方法不熟的先去学学吧），即Magic方法，php类可能会包含一些特殊的函数叫magic函数，magic函数命名是以符号__开头的，比如 __construct， __destruct，__toString，__sleep，__wakeup等等。这些函数都会在某些特殊时候被自动调用。 
例如__construct()方法会在一个对象被创建时自动调用，对应的__destruct则会在一个对象被销毁时调用等等。 
这里有两个比较特别的Magic方法，__sleep 方法会在一个对象被序列化的时候调用。 __wakeup方法会在一个对象被反序列化的时候调用。

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<?phpclass test{
    public $username = &#39;&#39;;    public $password = &#39;&#39;;    public $file = &#39;&#39;;    public function out(){
        echo "username: ".$this->username."<br>"."password: ".$this->password ;
    }     public function __toString() {
        return file_get_contents($this->file);
    }
}$a = new test();$a->file = &#39;C:\Users\YZ\Desktop\plan.txt&#39;;echo serialize($a);?>//tostring方法会在输出实例的时候执行，如果实例路径是隐秘文件就可以读取了

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<?phpclass test{
    public $username = &#39;&#39;;    public $password = &#39;&#39;;    public $file = &#39;&#39;;    public function out(){
        echo "username: ".$this->username."<br>"."password: ".$this->password ;
    }     public function __toString() {
        return file_get_contents($this->file);
    }
}$a = &#39;O:4:"test":3:{s:8:"username";s:0:"";s:8:"password";s:0:"";s:4:"file";s:28:"C:\Users\YZ\Desktop\plan.txt";}&#39;;echo unserialize($a);?>

16.session deserialization vulnerability

ini_set('session.serialize_handler', 'php_serialize');
ini_set('session.serialize_handler' , 'php');
The two handle sessions differently
\Users\YZ\Desktop\plan.txt";}';echo unserialize($a);?>

16.session deserialization vulnerability

ini_set('session.serialize_handler', 'php_serialize');
ini_set(' session.serialize_handler', 'php');
The two methods of handling sessions are different
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