The server requested authentication method unknown to the client ошибка

Oops! MySQL just showed the error ‘The server requested authentication method unknown to the client‘.

Usually, the error shows up when a user tries to connect to the database.

The reason for this error is improper authentication plugin settings in MySQL.

At Bobcares, we often get requests to fix MySQL errors, as a part of our Server Management Services.

Today, let’s see how our Support Engineers fix this error.

How does the MySQL server authenticate a client?

A PHP application connects to the MySQL server using the username provided by the server/hosting provider.

The server validates the user and returns the connection status. MySQL uses caching_sha2_password and auth_socket plugins for validation.

The caching_sha2_password plugin uses an SHA-2 algorithm with 256-bit password encryption. MySQL 8 prefers this auth method.

Whereas the auth_socket plugin checks if the socket username matches with the MySQL username. If the names don’t match, it checks for the socket username of the mysql.user. If a match is found, the plugin permits the connection.

But to serve the pre 8.0 clients and avoid compatibility errors, it is preferred to revert back the auth method. Older versions of MySQL use mysql_native_password plugin for validation.

Why does MySQL show the authentication method unknown to the client?

Recently one of our customers approached us with a MySQL auth error. The error showed up in MySQL 8. But the user had a PHP version 7.0. The default authentication plugin used by the MySQL is auth_socket.

Here MySQL client like PHPMyAdmin authenticates the user to login to the database by a password. Hence when a user tries to access the database using PHPMyAdmin ends up in the auth error. But the actual reason was compatibility error.

The error message is ‘The server requested authentication method unknown to the client‘. In PHPMyAdmin, the error appears as,

Now let’s see how our Support Engineers fix this error.

How we fix the error authentication method unknown to the client?

To fix this error we changed the default authentication plugin used by MySQL. For this, we logged in to MySQL as the root user. Then we run the command,

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';

Here we replaced the ‘password‘ with the password of the root user. If the database user is not root user, replace the username and password respectively.

Finally, this fixed the error. And the user was able to log in to PHPMyAdmin successfully.

But this is a temporary fix as the MySQL 8 uses PHP 7.0. The preferred auth plugin for this version is caching_sha2_password. 

Hence we also recommend the users to upgrade the pre 8.0 clients to avoid further errors.

[Still, having trouble in fixing MySQL errors? – We can help you.]

Conclusion

In short, MySQL error the server requested authentication method unknown to the client occurs due to the default authentication plugin used. Today, we saw how our Support Engineers changes this to fix the error.

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If you’ve recently upgraded from php 5.3 to a newer version (5.5, 5.6, 7.0) you may have encountered a nasty bug on your WordPress or Magento website:

SQLSTATE[HY000][2054]
The server requested authentication method unknown to the client [mysql_old_password]

Your application is no longer able to connect to the database! So, what’s going on here? In version 4.1 MySQL started introducing a new internal storage mechanism for passwords. When you connect to mysql in newer versions, it assumes your password hash will be 41 bytes long. The old versions assume they are 16 bytes long.

When you upgrade MySQL, it maintains a compatibility mode called old_passwords allowing you to continue using the 16 byte passwords. However, new versions of php do not allow you to continue using the 16 byte passwords. See this link.

To fix the problem, you need to force MySQL to use the new password format and update any old passwords which were stored using the incorrect format. If you’re on shared hosting, you will need to contact your hosting company as this change may require root access to both the server and mysql

Disable MySQL old_passwords

The first thing you want to do is update /etc/mysql/my.cnf. (This file may also be stored at /etc/my.cnf).
You should see some text like the below, which you will need to change:

## Change the below:

old_passwords=1;

## Change to:

old_passwords=0;

Once you’ve made this configuration change, you need to restart mysql:

sudo service mysql restart

Now you have instructed MySQL to process passwords in the new format.

Update Existing User Passwords

Now comes the harder part — you will need to re-hash existing user passwords to use the new format. Note that you must have the non-hashed (plaintext) password in order to update it. Otherwise you will need to simply reset the password to something new.

First, run the below command to get a list of current users and their password hashes:

SELECT host,user,password from mysql.user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | 5ea2f2a3436125ss9                         |
| localhost | alan | *11ADAA0470F690CC585086B716E32F4222294A59 |
| 127.0.0.1 | root | 5ea2f2a3436125ss9                         |
+-----------+------+-------------------------------------------+

Notice the output of the above command. Do you see anything different between alan and root? Alan’s password is clearly in the new format (longer text) and root’s is in the old format (shorter text). So, we know that we need to update the root user to use the new password format. Also, due to the way mysql stores users, we need to update 2 entries for the hosts “localhost” and “127.0.0.1” (yes they’re considered to be different).

Run the below commands to update:

UPDATE mysql.user SET Password = PASSWORD('plaintext_password_here') WHERE User = 'root';
Flush Privileges

Those two commands will change the root user’s password to whatever plaintext_password_here is, and will ensure it’s in the new format. We then flush the privileges to ensure the update takes effect.

Once you’ve completed both of the above steps, you should see php be able to connect to mysql again over mysql, mysqli, or pdo!