文章目录
- Brute Force（暴力（破解））
- （1）Low等级
- （2）Medium等级
- （3）High等级
- （4）Impossible
Brute Force（暴力（破解））
目的：通过枚举逐个猜测匹配某个预定值
Brute Force主要表现形式：通过设置（如表单） 预配值发送给服务器分析响应
攻击形式：传统暴力破解、字典暴力破解。
（1）Low等级
漏洞原理：直接使用原始的sql语句进行查询，没做代码审计。
代码审计：检查源代码的安全性
Brute Force Source
vulnerabilities/brute/source/low.php
<?php
if( isset( $_GET[ 'Login' ] ) ) {
$user = $_GET[ 'username' ]; // Get username
$pass = $_GET[ 'password' ]; // Get password
$pass = md5( $pass ); //对password做16字节的摘要算法
// Check the database
$query = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
$result = mysqli_query($GLOBALS["___mysqli_ston"], $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
if( $result && mysqli_num_rows( $result ) == 1 ) {
// Get users details
$row = mysqli_fetch_assoc( $result );
$avatar = $row["avatar"];
// Login successful
echo "<p>Welcome to the password protected area {$user}</p>";
echo "<img src=\"{$avatar}\" />";
}
else {
// Login failed
echo "<pre><br />Username and/or password incorrect.</pre>";
}
((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>
漏洞利用：
1）传统破解（利用sql注入漏洞）：
在username输入
admin' or '1' = '1
2）字典破解（burp工具利用）：
抓包 -> ctrl+I将包复制到intruder模块，对需要破解的参数值（如密码）两边设置单$ -> 在Payloads载入字典 -> 后按 Start attack按钮进行破解 -> 得到的响应结果length与其他不一致的，极有可能是该用户密码。
（2）Medium等级
利用了 mysqli_real_escape_string()函数对user中的特殊符号（x00，n，r，，’，”，x1a）进行转义，用md5()加密后，杜绝了password的sql注入可能；
<?php
if( isset( $_GET[ 'Login' ] ) ) {
// Sanitise username input
$user = $_GET[ 'username' ];
$user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
//利用了 mysqli_real_escape_string()函数：转移特殊字符
// Sanitise password input
$pass = $_GET[ 'password' ];
$pass = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
$pass = md5( $pass ); //对password加密
// Check the database
$query = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
$result = mysqli_query($GLOBALS["___mysqli_ston"], $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
if( $result && mysqli_num_rows( $result ) == 1 ) {
// Get users details
$row = mysqli_fetch_assoc( $result );
$avatar = $row["avatar"];
// Login successful
echo "<p>Welcome to the password protected area {$user}</p>";
echo "<img src=\"{$avatar}\" />";
}
else {
// Login failed
sleep( 2 );
echo "<pre><br />Username and/or password incorrect.</pre>";
}
((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>
漏洞利用：（既然对 手动输入的user进行字符转义和password的加密，普通注入难度较大）但仍可通过抓包对password进行枚举爆破
（3）High等级
加了令牌验证身份，对user和password都进行了转义，对pass加密
Brute Force Source
vulnerabilities/brute/source/high.php
<?php
if( isset( $_GET[ 'Login' ] ) ) {
// Check Anti-CSRF token //Token，可以抵御CSRF攻击，同时也增加了爆破的难度
checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
// Sanitise username input
$user = $_GET[ 'username' ];
$user = stripslashes( $user ); //去除字符串中的反斜线字符,如果有两个连续的反斜线,则只去掉一个
$user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
// Sanitise password input
$pass = $_GET[ 'password' ];
$pass = stripslashes( $pass );
$pass = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : "")); //mysql_real_escape_string()函数进行转义
$pass = md5( $pass );
// Check database
$query = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
$result = mysqli_query($GLOBALS["___mysqli_ston"], $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
if( $result && mysqli_num_rows( $result ) == 1 ) {
// Get users details
$row = mysqli_fetch_assoc( $result );
$avatar = $row["avatar"];
// Login successful
echo "<p>Welcome to the password protected area {$user}</p>";
echo "<img src=\"{$avatar}\" />";
}
else {
// Login failed
sleep( rand( 0, 3 ) );
echo "<pre><br />Username and/or password incorrect.</pre>";
}
((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
// Generate Anti-CSRF token //抵御CSRF的攻击，参考下面的token
generateSessionToken();
?>
每次请求行参数 携带user_token，一般token生成会加入时间，所以每次访问的令牌是不同的。（token不仅可以低于CSRF攻击，还可防止爆破）
漏洞利用： 既然每次的token不一样，那就需要知道每次的token
burp利用，
在攻击模块：选择攻击方式为pitchfork,为password和user_token设置负载标志；
设置第一个password负载集导入字段，第二个token设置recursive grep负载类型；
将拦截的请求报文token值复制到，Payload setting[recursive grep]的初始请求初始化负载中
找到Grep-Extract模块，add, fetch-response（提取响应报文）按钮搜索 token，分别填写搜索到的token的值的 前后标签和符号如（value='）（'/></form>）点击OK
找到Redirections模块，选择always重定向
开始，点击不一样的，然后就可以在响应看到渲染render显示
（4）Impossible
防御原理：token, 转义，加密，限制登录次数/时间
PDO（PHP Data Object）防御sql注入，同时 采用，登录次数过多，会锁定用户:
Brute Force Source
vulnerabilities/brute/source/impossible.php
<?php
if( isset( $_POST[ 'Login' ] ) && isset ($_POST['username']) && isset ($_POST['password']) ) {
// Check Anti-CSRF token
checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
// Sanitise username input
$user = $_POST[ 'username' ];
$user = stripslashes( $user );
$user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : "")); //mysqli_real_escape_string（）函数
// Sanitise password input
$pass = $_POST[ 'password' ];
$pass = stripslashes( $pass ); // 去掉反斜线字符
$pass = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : "")); //mysqli_real_escape_string（）函数
$pass = md5( $pass );
// Default values
$total_failed_login = 3;
$lockout_time = 15;
$account_locked = false;
// Check the database (Check user information)
$data = $db->prepare( 'SELECT failed_login, last_login FROM users WHERE user = (:user) LIMIT 1;' );
$data->bindParam( ':user', $user, PDO::PARAM_STR );
$data->execute();
$row = $data->fetch();
// Check to see if the user has been locked out.
if( ( $data->rowCount() == 1 ) && ( $row[ 'failed_login' ] >= $total_failed_login ) ) { //失败3次，
// User locked out. Note, using this method would allow for user enumeration!
//echo "<pre><br />This account has been locked due to too many incorrect logins.</pre>";
// Calculate when the user would be allowed to login again 计算再登录时间
$last_login = strtotime( $row[ 'last_login' ] );
$timeout = $last_login + ($lockout_time * 60);
$timenow = time();
/*
print "The last login was: " . date ("h:i:s", $last_login) . "<br />";
print "The timenow is: " . date ("h:i:s", $timenow) . "<br />";
print "The timeout is: " . date ("h:i:s", $timeout) . "<br />";
*/
// Check to see if enough time has passed, if it hasn't locked the account
if( $timenow < $timeout ) {
$account_locked = true;
// print "The account is locked<br />";
}
}
// Check the database (if username matches the password)
$data = $db->prepare( 'SELECT * FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' );
$data->bindParam( ':user', $user, PDO::PARAM_STR);
$data->bindParam( ':password', $pass, PDO::PARAM_STR );
$data->execute();
$row = $data->fetch();
// If its a valid login...
if( ( $data->rowCount() == 1 ) && ( $account_locked == false ) ) {
// Get users details
$avatar = $row[ 'avatar' ];
$failed_login = $row[ 'failed_login' ];
$last_login = $row[ 'last_login' ];
// Login successful
echo "<p>Welcome to the password protected area <em>{$user}</em></p>";
echo "<img src=\"{$avatar}\" />";
// Had the account been locked out since last login?
if( $failed_login >= $total_failed_login ) {
echo "<p><em>Warning</em>: Someone might of been brute forcing your account.</p>";
echo "<p>Number of login attempts: <em>{$failed_login}</em>.<br />Last login attempt was at: <em>{$last_login}</em>.</p>";
}
// Reset bad login count
$data = $db->prepare( 'UPDATE users SET failed_login = "0" WHERE user = (:user) LIMIT 1;' );
$data->bindParam( ':user', $user, PDO::PARAM_STR );
$data->execute();
} else {
// Login failed
sleep( rand( 2, 4 ) );
// Give the user some feedback
echo "<pre><br />Username and/or password incorrect.<br /><br/>Alternative, the account has been locked because of too many failed logins.<br />If this is the case, <em>please try again in {$lockout_time} minutes</em>.</pre>";
// Update bad login count
$data = $db->prepare( 'UPDATE users SET failed_login = (failed_login + 1) WHERE user = (:user) LIMIT 1;' );
$data->bindParam( ':user', $user, PDO::PARAM_STR );
$data->execute();
}
// Set the last login time
$data = $db->prepare( 'UPDATE users SET last_login = now() WHERE user = (:user) LIMIT 1;' );
$data->bindParam( ':user', $user, PDO::PARAM_STR );
$data->execute();
}
// Generate Anti-CSRF token
generateSessionToken();
?>
除了通过以上最高级别的代码防御，还可通过工具；
检验服务器是否处于被暴力破解的工具：
WFuzz, OWASP DirBuster and vulnerability scanners such as Nessus, Nikto, Acunetix
