DVWA csrf代码分析

LOW级别

源码如下：

<?php

if( isset( $_GET[ 'Change' ] ) ) {
    
    $pass_new  = $_GET[ 'password_new' ];    // 获取用户输入的新密码
    $pass_conf = $_GET[ 'password_conf' ];    //获取用户输入的确认密码

    // Do the passwords match?
    if( $pass_new == $pass_conf ) {        //判断输入的两个密码是否一致
        // They do!
        $pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
        $pass_new = md5( $pass_new );

        //更新数据
        $insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "';";
        $result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );

        // 输出密码修改成功
        echo "<pre>Password Changed.</pre>";
    }
    else {
        // 输入的两个密码不一致
        echo "<pre>Passwords did not match.</pre>";
    }

    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}

?> 

代码中的函数解释：

$GLOBALS["___mysqli_ston"]

PHP中的全局变量；___mysqli_ston 代表和数据库链接的对象mysqli；包含数据库连接需要的所有信息；用户名、密码、host等信息；是实现数据库查询更新的基础

$mysqli = new mysqli("localhost", "username", "password", "database");

$result = $mysqli->query("SELECT * FROM table");

while ($row = $result->fetch_assoc()) {
  echo $row["name"];
}

isset()函数：返回值为bool值

该函数用于检测变量是否已经设置/变量是否存在；如果已设置则返回true；否则返回false

源码中isset($GLOBALS["___mysqli_ston"])是判断是否设置了和数据库连接的对象；

is_object()函数：返回值为bool值

该函数用于检测变量是否是一个对象；是的话返回true；否则返回false

mysqli_real_escape_string()函数：防止sql注入

对字符串中的特殊字符进行转义：单引号、双引号、反斜杠(\)、NULL字符

两个参数：mysql连接、要转义的字符串

源码中mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_new )是转义输入的新密码字符串；防止查询时sql注入

trigger_error()函数：返回值为bool类型

用于触发一个错误；并将错误记录到PHP的日志中；也可以发到屏幕上；成功触发则返回true，失败则返回false（这里失败是指的是错误类型设置错误）

两个参数：错误消息、错误类型

错误类型如下：

E_ERROR：致命错误

E_WARNING：警告

E_NOTICE：通知

E_USER_ERROR：用户错误

E_USER_WARNING：用户警告

E_USER_NOTICE：用户通知

源码中的意思是触发一个用户错误；信息为使用了已失效的转义函数，返回值都为空

mysqli_query()函数

执行一个sql语句，并返回一个mysqli_result对象；包含查询的结果

两个参数：mysql连接、查询的语句

mysqli_error()函数

返回最近一次mysql操作错误信息

一个参数：mysql连接

mysqli_connect_error()函数

返回最近一次操作错误信息

一个参数：mysql连接

**$___mysqli_res ：**用于接收mysql_close的返回值

**mysqli_close()函数：**返回值为bool类型

关闭一个mysql连接并释放相关的资源

一个参数：mysql连接

成功关闭mysql连接则返回true；否则返回false

is_null()函数：返回值为bool类型

判断是否为空；是则返回true；否则返回false

源码中((is_null(___mysqli_res = mysqli_close(GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);用于确认mysql连接被正常的关闭了；如果关闭了则返回true；没有关闭则会返回false

Medium级别

源码如下：

<?php

if( isset( $_GET[ 'Change' ] ) ) {
    // 检查referer字段的内容
    if( stripos( $_SERVER[ 'HTTP_REFERER' ] ,$_SERVER[ 'SERVER_NAME' ]) !== false ) {
        // Get input
        $pass_new  = $_GET[ 'password_new' ];
        $pass_conf = $_GET[ 'password_conf' ];

        // Do the passwords match?
        if( $pass_new == $pass_conf ) {
            // They do!
            $pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
            $pass_new = md5( $pass_new );

            // Update the database
            $insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "';";
            $result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );

            // Feedback for the user
            echo "<pre>Password Changed.</pre>";
        }
        else {
            // Issue with passwords matching
            echo "<pre>Passwords did not match.</pre>";
        }
    }
    else {
        // Didn't come from a trusted source
        echo "<pre>That request didn't look correct.</pre>";
    }

    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}

?> 

其中函数解释

相比LOW级别而言，里面多了一个检查referer字段的验证

stripos()函数

在一个字符串中查找另一个字符串是否存在；如果存在则返回位置；如果不存在则返回false

两个参数：用于搜索的字符串、用于查找的字符串

$_SERVER[]：获取当前运行脚本的信息

$_SERVER[ 'HTTP_REFERER' ]

获取http中referer字段的信息

$_SERVER[ 'SERVER_NAME' ]

获取当前访问的域名信息

High级别

源代码如下：

<?php

$change = false;
$request_type = "html";
$return_message = "Request Failed";

//采用post请求发送数据，指定文本类型

if ($_SERVER['REQUEST_METHOD'] == "POST" && array_key_exists ("CONTENT_TYPE", $_SERVER) && $_SERVER['CONTENT_TYPE'] == "application/json") {
    $data = json_decode(file_get_contents('php://input'), true);
    $request_type = "json";
    if (array_key_exists("HTTP_USER_TOKEN", $_SERVER) &&
        array_key_exists("password_new", $data) &&
        array_key_exists("password_conf", $data) &&
        array_key_exists("Change", $data)) {
        $token = $_SERVER['HTTP_USER_TOKEN'];
        $pass_new = $data["password_new"];
        $pass_conf = $data["password_conf"];
        $change = true;
    }
} else {
    if (array_key_exists("user_token", $_REQUEST) &&
        array_key_exists("password_new", $_REQUEST) &&
        array_key_exists("password_conf", $_REQUEST) &&
        array_key_exists("Change", $_REQUEST)) {
        $token = $_REQUEST["user_token"];
        $pass_new = $_REQUEST["password_new"];
        $pass_conf = $_REQUEST["password_conf"];
        $change = true;
    }
}

//通过token进行检测

if ($change) {
    // Check Anti-CSRF token
    checkToken( $token, $_SESSION[ 'session_token' ], 'index.php' );

    // Do the passwords match?
    if( $pass_new == $pass_conf ) {
        // They do!
        $pass_new = mysqli_real_escape_string ($GLOBALS["___mysqli_ston"], $pass_new);
        $pass_new = md5( $pass_new );

        // Update the database
        $insert = "UPDATE `users` SET password = '" . $pass_new . "' WHERE user = '" . dvwaCurrentUser() . "';";
        $result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert );

        // Feedback for the user
        $return_message = "Password Changed.";
    }
    else {
        // Issue with passwords matching
        $return_message = "Passwords did not match.";
    }

    mysqli_close($GLOBALS["___mysqli_ston"]);

    if ($request_type == "json") {
        generateSessionToken();
        header ("Content-Type: application/json");
        print json_encode (array("Message" =>$return_message));
        exit;
    } else {
        echo "<pre>" . $return_message . "</pre>";
    }
}

// Generate Anti-CSRF token
generateSessionToken();

?> 

代码函数解析：

checkToken( $token, $_SESSION[ 'session_token' ], 'index.php' );

检查http中的token和session中的token是否一致；如果一致则返回true；如果不一致则重定向到index.php界面

generateSessionToken();

重新获取token

该源码只接收POST请求的数据，然后检查token来验证身份

Impossible级别

源代码如下：

<?php

if( isset( $_GET[ 'Change' ] ) ) {
    // Check Anti-CSRF token
    checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

    // Get input
    $pass_curr = $_GET[ 'password_current' ];
    $pass_new  = $_GET[ 'password_new' ];
    $pass_conf = $_GET[ 'password_conf' ];

    // Sanitise current password input
    $pass_curr = stripslashes( $pass_curr );
    $pass_curr = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_curr ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
    $pass_curr = md5( $pass_curr );

    // Check that the current password is correct
    $data = $db->prepare( 'SELECT password FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' );
    $data->bindParam( ':user', dvwaCurrentUser(), PDO::PARAM_STR );
    $data->bindParam( ':password', $pass_curr, PDO::PARAM_STR );
    $data->execute();

    // Do both new passwords match and does the current password match the user?
    if( ( $pass_new == $pass_conf ) && ( $data->rowCount() == 1 ) ) {
        // It does!
        $pass_new = stripslashes( $pass_new );
        $pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
        $pass_new = md5( $pass_new );

        // Update database with new password
        $data = $db->prepare( 'UPDATE users SET password = (:password) WHERE user = (:user);' );
        $data->bindParam( ':password', $pass_new, PDO::PARAM_STR );
        $data->bindParam( ':user', dvwaCurrentUser(), PDO::PARAM_STR );
        $data->execute();

        // Feedback for the user
        echo "<pre>Password Changed.</pre>";
    }
    else {
        // Issue with passwords matching
        echo "<pre>Passwords did not match or current password incorrect.</pre>";
    }
}

// Generate Anti-CSRF token
generateSessionToken();

?> 

代码中函数解析：

stripslashes()函数

去除字符串中的反斜杠转义字符(\)

**$data = $db->prepare( 'SELECT password FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' ); //**准备一条语句并放到服务器端进行编译；固定语句的格式；方便使用

data-\>bindParam( ':user', dvwaCurrentUser(), PDO::PARAM_STR ); //** 绑定用户名 **data->bindParam( ':password', pass_curr, PDO::PARAM_STR ); //** 绑定密码 **data->execute(); //执行mysql语句

rowCount()：返回上一次mysql语句执行变化的行数

该源码通过token+原密码验证确保了csdf无法渗透

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