infoschema: improve the security vunerability of schemata infoschema table

[reafans]

What problem does this PR solve?

improve the security vunerability of schemata infoschema table

related to #209

What is changed and how it works?

before：new user both can get the whole data of information_schema.schemata

mysql -u root -h 127.0.0.1 -P 4000
mysql> use information_schema;
mysql> select * from schemata;
+--------------+--------------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME        | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+--------------------+----------------------------+------------------------+----------+
| def          | INFORMATION_SCHEMA | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | mysql              | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | PERFORMANCE_SCHEMA | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | test               | utf8mb4                    | utf8mb4_bin            | NULL     |
+--------------+--------------------+----------------------------+------------------------+----------+
4 rows in set (0.00 sec)

mysql> create user tester;
mysql -u tester -h 127.0.0.1 -P 4000
mysql> use information_schema;
mysql> select * from schemata;
+--------------+--------------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME        | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+--------------------+----------------------------+------------------------+----------+
| def          | INFORMATION_SCHEMA | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | mysql              | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | PERFORMANCE_SCHEMA | utf8mb4                    | utf8mb4_bin            | NULL     |
| def          | test               | utf8mb4                    | utf8mb4_bin            | NULL     |
+--------------+--------------------+----------------------------+------------------------+----------+
4 rows in set (0.00 sec)

after：the new user can only get an one row set in which SCHEMA_NAME is INFORMATION_SCHEMA.

mysql -u tester -h 127.0.0.1 -P 4000
mysql> use information_schema;
mysql> select * from schemata;
+--------------+--------------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME        | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+--------------------+----------------------------+------------------------+----------+
| def          | INFORMATION_SCHEMA | utf8mb4                    | utf8mb4_bin            | NULL     |
+--------------+--------------------+----------------------------+------------------------+----------+
1 row in set (0.00 sec)

Check List

Tests

• Unit test
• Integration test

Code changes

• Has exported function/method change

Side effects
None

Related changes
None

[codecov]

Codecov Report

Merging #14003 into master will decrease coverage by 0.0717%.
The diff coverage is 100%.

@@               Coverage Diff                @@
##             master     #14003        +/-   ##
================================================
- Coverage   80.2502%   80.1784%   -0.0718%     
================================================
  Files           482        482                
  Lines        121166     120813       -353     
================================================
- Hits          97236      96866       -370     
- Misses        16205      16215        +10     
- Partials       7725       7732         +7

[reafans]

/run-all-tests

[reafans]

/run-all-tests

[AilinKid]

/run-all-tests

[reafans]

/run-all-tests

[wjhuang2016]

lgtm

[djshow832]

Add a test case that querying information_schema by a user whose username is empty, which means the query is an internal SQL.

[reafans]

the case is in 450 line of this file, a new tk and tk.MustQuery() will create a user whose username is empty.

[reafans]

/run-all-tests

[djshow832]

Approve