This guide explains how to disable SSH password authentication for specific user or group in Linux and Unix operating systems.
Please note that we are not going to entirely disable SSH access to users or a group. Instead, we will only disable the SSH password authentication.
The users can still access the systems via SSH using other authentication methods, for example SSH key-based authentication.
Disable SSH password authentication for specific user or group
We can allow or deny SSH access for users and/or a whole group using "/etc/ssh/sshd_config" file in Linux. The sshd_config file has a parameter named "Match" which will help you to disable SSH password authentication for users or groups.
Let us first see how to disable password authentication for a specific user.
Edit "/etc/ssh/sshd_config" file using your favorite editor as root or sudo user:
$ sudo nano /etc/ssh/sshd_config
First, remove the default authentication method by comment out the following line:
Next, add the following lines at the end:
[...] Match User senthil PasswordAuthentication no
Please note that Match is effective "until either another Match line or the end of the file." If a keyword appears in multiple Match blocks that are satisfied, only the first instance of the keyword is applied.
As per the above example, we have disabled the SSH password authentication for the user called "senthil". Replace "senthil" with your own username. Save and close the file. Restart ssh service to take effect the changes:
$ sudo systemctl restart ssh
Now try to login as user "senthil" via SSH:
$ ssh [email protected]
You will see the following error message:
[email protected]: Permission denied (publickey).
Disable SSH password authentication for a group
To disable SSH password authentication for a specific Group, just replace the user name with the group name in the sshd_config file.
Match Group mygroup PasswordAuthentication no
Replace "mygroup" in the above configuration with your own group name.
Don't forget to restart the ssh service to apply the changes.
Disable SSH password authentication for multiple users
You can deny SSH password authentication for multiple users by mentioning the user names with comma-separated like below:
Match User senthil,kumar PasswordAuthentication no
The above example configuration will prevent SSH password authentication for users "senthil" and "kumar".
Disable SSH password authentication for all users except root user
In some Linux systems, you might want to allow SSH password authentication for "root" user only and disable it for all other users. If so, add the following line in sshd_config file at the end:
Match User !root PasswordAuthentication no
Restrict SSH password authentication by host or IP address
Not just user or group, we can deny SSH password authentication by host or IP address as well.
For example, the following example will prevent SSH access from a host that contains the IP address:
Match Address 192.168.225.37 PasswordAuthentication no
To limit SSH password authentication for a specific range of IP addresses, add this:
Match Address 192.168.225.* PasswordAuthentication no
And this example will deny SSH access using password from a host that contains the hostname:
Match Address hostname PasswordAuthentication no
For more details, refer man pages.
$ man sshd_config
In this guide, we discussed how to disable SSH password authentication for specific user or group in Linux. We further looked at how to disable SSH password access for multiple users, how to restrict SSH password access to all user but for root user. Finally, we learned how to restrict SSH password authentication by host or IP address.
Other SSH Related guides:
- How To Configure SSH Key-based Authentication In Linux
- Allow Or Deny SSH Access To A Particular User Or Group In Linux
- Limit The Number Of SSH Logins Per User/Group/System
- Restrict Access To Linux Servers Using TCP Wrappers
- Execute Commands On Remote Linux Systems Via SSH
- How To Create SSH Alias In Linux
- How To SSH Into A Particular Directory On Linux
- SSLH – Share A Same Port For HTTPS And SSH
- ScanSSH – Fast SSH Server And Open Proxy Scanner
- How To Resume Partially Transferred Files Over SSH Using Rsync
- How To Run Single Command On Multiple Remote Systems At Once
- DSH – Run A Linux Command On Multiple Hosts At A Time
- How To Stop SSH Session From Disconnecting In Linux
- How To Enable SSH On FreeBSD
Hope this helps.