SQL注入之information_schema

在学习SQL注入时, 经常拿出来的例子就是PHP+MySQL这一套经典组合. 其中又经常提到的>=5.0版本的MySQL的内置库: information_schema

简单看一下information_schema库中的内容

其中在注入时关注的两张表: tables 和 columns

mysql> use information_schema
Database changed
mysql> show tables;
+---------------------------------------+
| Tables_in_information_schema          |
+---------------------------------------+
| CHARACTER_SETS                        |
| COLLATIONS                            |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS                               |
| COLUMN_PRIVILEGES                     |
| ENGINES                               |
| EVENTS                                |
| FILES                                 |
| GLOBAL_STATUS                         |
| GLOBAL_VARIABLES                      |
| KEY_COLUMN_USAGE                      |
| PARAMETERS                            |
| PARTITIONS                            |
| PLUGINS                               |
| PROCESSLIST                           |
| PROFILING                             |
| REFERENTIAL_CONSTRAINTS               |
| ROUTINES                              |
| SCHEMATA                              |
| SCHEMA_PRIVILEGES                     |
| SESSION_STATUS                        |
| SESSION_VARIABLES                     |
| STATISTICS                            |
| TABLES                                |
| TABLESPACES                           |
| TABLE_CONSTRAINTS                     |
| TABLE_PRIVILEGES                      |
| TRIGGERS                              |
| USER_PRIVILEGES                       |
| VIEWS                                 |
| INNODB_BUFFER_PAGE                    |
| INNODB_TRX                            |
| INNODB_BUFFER_POOL_STATS              |
| INNODB_LOCK_WAITS                     |
| INNODB_CMPMEM                         |
| INNODB_CMP                            |
| INNODB_LOCKS                          |
| INNODB_CMPMEM_RESET                   |
| INNODB_CMP_RESET                      |
| INNODB_BUFFER_PAGE_LRU                |
+---------------------------------------+
40 rows in set (0.00 sec)

其中tables表中保存的是库和表名的对应信息, 分别是table_schema, table_name.

通过select table_schema, table_name from tables, 可以查询整个MySQL下所有的库名和表名的对应信息. 注意是全部的, 查询指定库的话, 使用where条件指定即可

mysql> select table_schema, table_name from tables where table_schema='security';
+--------------+------------+
| table_schema | table_name |
+--------------+------------+
| security     | emails     |
| security     | referers   |
| security     | uagents    |
| security     | users      |
+--------------+------------+
4 rows in set (0.00 sec)　

另一张表columns, 里面是有三个字段的, table_schema, table_name, column_name

mysql> select table_schema, table_name, column_name from columns where table_schema='security' and table_name='users';
+--------------+------------+-------------+
| table_schema | table_name | column_name |
+--------------+------------+-------------+
| security     | users      | id          |
| security     | users      | username    |
| security     | users      | password    |
+--------------+------------+-------------+
3 rows in set (0.01 sec)

带入到联合查询中的写法

mysql> select id, username, password from users where id = 1 union select table_schema, table_name, column_name from information_schema.columns where table_schema=database() and table_name='users';
+----------+----------+----------+
| id       | username | password |
+----------+----------+----------+
| 1        | Dumb     | Dumb     |
| security | users    | id       |
| security | users    | username |
| security | users    | password |
+----------+----------+----------+
4 rows in set (0.00 sec)