DVWA靶场-SQL InjectionSQL注入

作者：从前慢现在也慢 | 2024-03-19 09:54:17

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SQL Injection（SQL注入）概念

就是通过把SQL命令插入到Web表单提交或输入域名或页面请求的查询字符串，最终达到欺骗服务器执行恶意的SQL命令。具体来说，它是利用现有应用程序，将（恶意）的SQL命令注入到后台数据库引擎执行的能力，它可以通过在Web表单中输入（恶意）SQL语句得到一个存在安全漏洞的网站上的数据库，而不是按照设计者意图去执行SQL语句。

手工注入常规思路

1.判断是否存在注入，注入是字符型还是数字型

2.猜解SQL查询语句中的字段数

3.确定回显位置

4.获取当前数据库

5.获取数据库中的表

6.获取表中的字段名

7.得到数据

low等级


<?php
 
if( isset( $_REQUEST[ 'Submit' ] ) ) {
	// Get input
	$id = $_REQUEST[ 'id' ];
 
	switch ($_DVWA['SQLI_DB']) {
		case MYSQL:
			// 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
				$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
			}
 
			mysqli_close($GLOBALS["___mysqli_ston"]);
			break;
		case SQLITE:
			global $sqlite_db_connection;
 
			#$sqlite_db_connection = new SQLite3($_DVWA['SQLITE_DB']);
			#$sqlite_db_connection->enableExceptions(true);
 
			$query  = "SELECT first_name, last_name FROM users WHERE user_id = '$id';";
			#print $query;
			try {
				$results = $sqlite_db_connection->query($query);
			} catch (Exception $e) {
				echo 'Caught exception: ' . $e->getMessage();
				exit();
			}
 
			if ($results) {
				while ($row = $results->fetchArray()) {
					// Get values
					$first = $row["first_name"];
					$last  = $row["last_name"];
 
					// Feedback for end user
					$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
				}
			} else {
				echo "Error in fetch ".$sqlite_db->lastErrorMsg();
			}
			break;
	} 
}
 
?>

没有对用户输入进行任何过滤或转义，直接注入即可

medium等级


<?php
 
if( isset( $_POST[ 'Submit' ] ) ) {
	// Get input
	$id = $_POST[ 'id' ];
 
	$id = mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $id);
 
	switch ($_DVWA['SQLI_DB']) {
		case MYSQL:
			$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
				$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
			}
			break;
		case SQLITE:
			global $sqlite_db_connection;
 
			$query  = "SELECT first_name, last_name FROM users WHERE user_id = $id;";
			#print $query;
			try {
				$results = $sqlite_db_connection->query($query);
			} catch (Exception $e) {
				echo 'Caught exception: ' . $e->getMessage();
				exit();
			}
 
			if ($results) {
				while ($row = $results->fetchArray()) {
					// Get values
					$first = $row["first_name"];
					$last  = $row["last_name"];
 
					// Feedback for end user
					$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
				}
			} else {
				echo "Error in fetch ".$sqlite_db->lastErrorMsg();
			}
			break;
	}
}
 
// 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"]);
?>

mysqli_real_escape_string()

mysqli_real_escape_string()函数用于对用户输入的id进行转义，以防止恶意SQL代码被插入到SQL查询语句中。通过使用这个函数，特殊字符（如单引号）将被转义，从而使输入的数据变得安全，并且不会破坏SQL查询语句的结构。

涉及的字符是 NUL（ASCII 0）、\n、\r、\、'、" 和 Control-Z

high等级


<?php
 
if( isset( $_SESSION [ 'id' ] ) ) {
	// Get input
	$id = $_SESSION[ 'id' ];
 
	switch ($_DVWA['SQLI_DB']) {
		case MYSQL:
			// 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
				$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
			}
 
			((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);		
			break;
		case SQLITE:
			global $sqlite_db_connection;
 
			$query  = "SELECT first_name, last_name FROM users WHERE user_id = '$id' LIMIT 1;";
			#print $query;
			try {
				$results = $sqlite_db_connection->query($query);
			} catch (Exception $e) {
				echo 'Caught exception: ' . $e->getMessage();
				exit();
			}
 
			if ($results) {
				while ($row = $results->fetchArray()) {
					// Get values
					$first = $row["first_name"];
					$last  = $row["last_name"];
 
					// Feedback for end user
					$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
				}
			} else {
				echo "Error in fetch ".$sqlite_db->lastErrorMsg();
			}
			break;
	}
}
 
?>

在上面的代码中，虽然没有直接调用mysqli_real_escape_string()函数对$_SESSION['id']进行转义处理，但是通过将$_SESSION['id']直接插入到SQL查询语句中，可以利用PHP会自动转义会话变量的特性来防止SQL注入。

SELECT first_name, last_name FROM users WHERE user_id = '$id' LIMIT 1;

这个LIMIT 1;会在sql注入中被注释符号注释掉，相当于没用

impossible等级


<?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 )) {
		$id = intval ($id);
		switch ($_DVWA['SQLI_DB']) {
			case MYSQL:
				// 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
					$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
				}
				break;
			case SQLITE:
				global $sqlite_db_connection;
 
				$stmt = $sqlite_db_connection->prepare('SELECT first_name, last_name FROM users WHERE user_id = :id LIMIT 1;' );
				$stmt->bindValue(':id',$id,SQLITE3_INTEGER);
				$result = $stmt->execute();
				$result->finalize();
				if ($result !== false) {
					// There is no way to get the number of rows returned
					// This checks the number of columns (not rows) just
					// as a precaution, but it won't stop someone dumping
					// multiple rows and viewing them one at a time.
 
					$num_columns = $result->numColumns();
					if ($num_columns == 2) {
						$row = $result->fetchArray();
 
						// Get values
						$first = $row[ 'first_name' ];
						$last  = $row[ 'last_name' ];
 
						// Feedback for end user
						$html .= "<pre>ID: {$id}<br />First name: {$first}<br />Surname: {$last}</pre>";
					}
				}
 
				break;
		}
	}
}
 
// Generate Anti-CSRF token
generateSessionToken();
 
?>

加了token检查

代码使用is_numeric()函数来检查id是否为数字类型。

使用intval()函数将id转换为整数类型，以确保输入的id是一个有效的整数值。

代码使用了PDO（PHP Data Objects）扩展来执行预处理语句，通过绑定参数和执行查询来防止SQL注入。

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