authentication in linux [closed]

Question

I want to allow a particular user to login without any authentication but without using any username, digital signature or key.

I used the Match command in ssh but nothing happened

Answer 1

I'm not sure you can log into a device without at least a username. You dont have to have a password associated with the username but I'm pretty sure Linux requires a username when connecting via SSH.

For example you could have the root username have no password and simply log in using:

ssh root@{hostname/IP address}

This should then dump the user in root's home directory without the need for a password.

So as not to change the root user, a simple approach might be:

Log into the device using a known sudo username and password (e.g. root):

ssh su-user@{hostname/IP address}

Create a new user (if required):

adduser <username>

This will then ask you to enter a password for the new user, which you can leave blank. Acknowledge the warning of the weak password, and a new user should have been created with no password.

You may also need to create the new users home directory (/home/"username") as some configurations (busy box for example) may not automatically create this. The location of the users home directory can also be altered by changing the relevant line in the /etc/passwd file.

The line should look like this:

<username>:x:uuuu:gggg:Description:/path/to/home/dir:/shell/used

Where:

• x = User Password (will just be an x)
• uuuu = User ID (will be integer number)
• gggg = Group ID (will also be integer number)

The final two are the path to the users home directory (change this if desired), and the path to the shell program to be used by this user.

You should now be able to log into the device (as above) with that username and not be prompted for a password.

Consideration should be given to the security risks implicated by the lack of a password, but if its not security critical then this should be fine.