MySQL Proxyで認証をフックしようと悪戦苦闘（ユーザー名だけ書き換えはOK）

• ユーザー名に"+"が含まれていた場合、"+"とそれ以降の文字列を握りつぶす。
• mysql -uroot+yoku0825 -p だったら、rootに変換してやる。
• パスワードやその他のオプションは入力されたものを素通し。
• クライアントはmysqlコマンドラインクライアントとは限らない。

$ cat ./proxy.lua
local password= assert(require("mysql.password"))
local proto= assert(require("mysql.proto"))

function read_auth()
  local c = proxy.connection.client
  local s = proxy.connection.server

  local proxy_user= c.username
  local mysql_user= string.match(c.username, "^(%w+)+")
  if not mysql_user then mysql_user= proxy_user end

  proxy.queries:append(1, proto.to_response_packet(
  {
    server_capabilities= 33280,
    username= mysql_user,
    response= c.scrambled_password
  }))

  return proxy.PROXY_SEND_QUERY
end

$ /usr/mysql/proxy/bin/mysql-proxy --proxy-address=127.0.0.55:3306 --proxy-backend-addresses=127.0.0.1:64055 --proxy-lua-script=/usr/mysql/proxy/proxy.lua --log-level=debug

$ mysql -h 127.0.0.55 -P 3306 -u root+yoku0825 -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15
Server version: 5.5.32-log Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> status
--------------
mysql  Ver 14.14 Distrib 5.6.12, for Linux (x86_64) using  EditLine wrapper

Connection id:          15
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.5.32-log Source distribution
Protocol version:       10
Connection:             127.0.0.55 via TCP/IP
Server characterset:    utf8
Db     characterset:    utf8
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:               3306
Uptime:                 2 days 19 hours 27 min 2 sec

Threads: 3  Questions: 77  Slow queries: 2  Opens: 36  Flush tables: 1  Open tables: 29  Queries per second avg: 0.000
--------------

mysql> SELECT current_user();
+----------------+
| current_user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)