privilege: fix auth_socket bug, should only allow os user name to login

[lcwangchao]

What problem does this PR solve?

Issue Number: close #54031

Problem Summary:

What changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

1. my os user is wangchao

$ whoami
wangchao

2. create users:

> CREATE USER 'u1'@'localhost' IDENTIFIED WITH auth_socket;
Query OK, 0 rows affected
Time: 0.017s
> CREATE USER 'u2'@'localhost' IDENTIFIED WITH auth_socket AS "wangchao";
Query OK, 0 rows affected
Time: 0.012s
> CREATE USER 'wangchao'@'localhost' IDENTIFIED WITH auth_socket;
Query OK, 0 rows affected
Time: 0.025s
TiDB root@127.0.0.1:test> select host,user,authentication_string,plugin from mysql.user;
+-----------+----------+-----------------------+-----------------------+
| host      | user     | authentication_string | plugin                |
+-----------+----------+-----------------------+-----------------------+
| %         | root     |                       | mysql_native_password |
| localhost | u1       |                       | auth_socket           |
| localhost | u2       | wangchao              | auth_socket           |
| localhost | wangchao |                       | auth_socket           |
+-----------+----------+-----------------------+-----------------------+
4 rows in set
Time: 0.011s

3. Try log in:

u1 is rejected because it is not same with os user:

$ mysql --comments -uu1 -S/tmp/tidb-4001.sock
ERROR 1045 (28000): Access denied for user 'u1'@'localhost' (using password: YES)

u2 is allowed because its authenticate string is same with os user:

$ mysql --comments -uu2 -S/tmp/tidb-4001.sock
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2097182
Server version: 8.0.11-TiDB-None TiDB Server (Apache License 2.0) Community Edition, MySQL 8.0 compatible
...

wangchao is allowed because its the os user name:

> mysql --comments -uwangchao -S/tmp/tidb-4001.sock
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2097184
Server version: 8.0.11-TiDB-None TiDB Server (Apache License 2.0) Community Edition, MySQL 8.0 compatible
...

• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

fix `auth_socket` bug, should only allow os user name to login

[tiprow]

Hi @lcwangchao. Thanks for your PR.

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[dveeden]

Is it possible to add tests to ensure this doesn't break again later on?

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-14 09:44:33.48296416 +0000 UTC m=+717027.536276083: ☑️ agreed by CbcWestwolf.
• 2024-06-14 10:00:06.156874583 +0000 UTC m=+717960.210186770: ☑️ agreed by dveeden.

[codecov]

Codecov Report

Attention: Patch coverage is 10.00000% with 18 lines in your changes missing coverage. Please review.

Project coverage is 55.0191%. Comparing base (21089fd) to head (78ef649).
Report is 4 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #54032         +/-   ##
=================================================
- Coverage   72.5699%   55.0191%   -17.5509%     
=================================================
  Files          1515       1634        +119     
  Lines        434546     605962     +171416     
=================================================
+ Hits         315350     333395      +18045     
- Misses        99722     250261     +150539     
- Partials      19474      22306       +2832     

Flag	Coverage Δ
integration	35.2783% <0.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9656% <ø> (ø)
parser	∅ <ø> (∅)
br	42.2162% <ø> (-0.0025%)	⬇️

[tiprow]

@lcwangchao: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
tidb_parser_test	ea41978	link	true	/test tidb_parser_test

Full PR test history. Your PR dashboard.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CbcWestwolf, dveeden

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #54049.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #54050.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #54051.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #54052.