Can't connect to mysql server 8.0 when password is larger than 19 characters

[erfanium]

Affected version: 1.8.0
Latest working version: 1.7.0

Reproduction Steps

1- mysql server with complex password and caching_sha2_password as default

services:
  mysql_test:
    image: mysql:8.0.33
    environment:
      MYSQL_ROOT_PASSWORD: "*pl3$#&XiC4Tn*AP13l#OKUY"
      MYSQL_DATABASE: default
      MYSQL_USER: base-user
      MYSQL_PASSWORD: "*pl3$#&XiC4Tn*AP13l#OKUY"
    ports:
      - "3306:3306"
    command: --default-authentication-plugin=caching_sha2_password

2-

package main

import "github.com/go-mysql-org/go-mysql/client"

func main() {
	conn, err := client.Connect("127.0.0.1:3306", "root", "*pl3$#&XiC4Tn*AP13l#OKUY", "default")
	if err != nil {
		panic(err)
	}
	defer conn.Close()

	_, err = conn.Execute(`select 1;`)

	if err != nil {
		panic(err)
	}

	println("connected")
}

then you will see this error:

panic: handleAuthResult: ERROR 1045 (28000): Access denied for user 'root'@'172.23.0.1' (using password: YES)

[lance6716]

Thank for reporting, I'll take a look next week

[erfanium]

@lance6716
Thanks! I'm new to golang, but I can contribute on this if you need.

[lance6716]

@erfanium Thank you, currently I only tried to reproduce this problem, but I have not started to locate the root cause. This is my testing steps:

docker run --rm --name mysql-3306 -p 3306:3306 -e MYSQL_ROOT_PASSWORD='*pl3$#&XiC4Tn*AP13l#OKUY' mysql:8.0.33 --log-bin=mysql-bin --port=3306 --bind-address=0.0.0.0 --binlog-format=ROW --server-id=1 --gtid_mode=ON --enforce-gtid-consistency=true --default-authentication-plugin=caching_sha2_password

then add this unit test in client package

func TestComplexPassword(t *testing.T) {
	conn, err := Connect("127.0.0.1:3306", "root", "*pl3$#&XiC4Tn*AP13l#OKUY", "default")
	require.NoError(t, err)
	defer conn.Close()

	_, err = conn.Execute(`select 1;`)
	require.NoError(t, err)
}

I think you can help me in many aspects, like fixing the code, adding unit tests in our CI, using git bisect to find the commit that caused the problem. I'll start to do rest work after you choose some.

[erfanium]

So far I have figured out that it's not about spacial characters. any password larger than 19 characters is not working! So it's kinda a critical bug.

sample not working password: abcdefghijklmnopqrsu

[erfanium]

I'll start to do rest work after you choose some

I have spent many hours working on this issue, but it requires a good knowledge of mysql auth mechanism. so I might not be able to fix it very soon.

[lance6716]

Thanks, that's very helpful. I'll take a look soon

[lance6716]

136935a is the first bad commit