Admins eHow SysAdmin Tips & Tricks

August 20, 2014

Force public key authentication on SSH daemon (disable password authentication)

Filed under: Debian,linux,Security — Tags: , , , , , , — admin @ 2:18 pm

It is a very good security practice to completely disable password authentication on your Linux server and use public key authentication method.
In order to do that you need to create your own public/private key pair and put the public key in ~/.ssh/authorized_keys

mkdir -p ~/.ssh
echo 'ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDHV80zPWjPAwKo8Be0k1ypBRMdYDC0H2eQchu3MFsEp8av2F/18GNuHsbyMWp0p1uovP5LGZ/oPZ1ISJxLxxOBiqv0fOyb8uTDYWUUITgGvq9Fppj3BNYTjnLCUAVMKdP3VJ7IPk69ygYR1nhAXiv3dSfeG74f2eo3ZYhrylsVS2G84DUh47FuEFOsfn5s2wXVjwAgqdKBhiVQZWrptf6TEK3fZTVg4rCiRJ+YiIwTZr/CfFHbdqOiwDlGR5fWo0PHHq31lrQXzkASfi3C+ahQFnHsy4+8LdCq+TjzC3J6PbuXP1wpLdm1iP35f61hU1wX2hwhyxdvE+SBXT/PpSVB' >> ~/.ssh/authorized_keys

DISCLAIMER : The above key is my public key, if you put it on your server, I will be able to login into your server 😀
Now add/change the following config to /etc/ssh/sshd_config

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no
PubkeyAuthentication yes

and restart ssh service :

service ssh restart

Note : Before closing your current SSH session, I highly recommend you to test that actually you can login into your server by new method. otherwise you may be locked out of your server.

August 14, 2009

How to auth ssh users by radius in debian

Filed under: Debian,General — Tags: , , , — admin @ 11:57 am

install libpam-radius-auth

apt-get install libpam-radius-auth

open /etc/pam_radius_auth.conf

nano /etc/pam_radius_auth.conf

and add the following lines into it. Your_IP and PORT are the IP address and Port of Radius sever. SecretKey is the Secret of radius server. 3 is the timeout in seconds.

# server[:port] shared_secret      timeout (s)
YOUR_IP:PORT SecretKey 3

Change the permissions :

chown root /etc/pam_radius_auth.conf
chmod go-rwx /etc/pam_radius_auth.conf

open /etc/pam.d/common-auth :

nano /etc/pam.d/common-auth

and add the following lines :

auth sufficient pam_radius_auth.so

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