OpenSSH Server

1.   Introduction
1.1   Installing OpenSSH
1.2   Key based authentication
1.3   Securing OpenSSH

Introduction

OpenSSH is a free version of the SSH connectivity tools that technical users of the Internet rely on and provides secure tunneling capabilities and several authentication methods.

Installing OpenSSH

 aptitude install ssh

Key based authentication

I want to secure OpenSSH, whilst still preserving the capability to connect remotely as root in order to do backups.

• CreatePublicPrivateKeyPair
• CopyPublicKey

Securing OpenSSH

When you are happy that you can log in via all your accounts it is time to better secure OpenSSH by limiting where 'root' can login from and which users have login capability.

 nano /etc/ssh/sshd_config

Uncomment the following line, to specify the file that contains the public keys that can be used for user authentication.

 AuthorizedKeysFile      %h/.ssh/authorized_keys

Add a line similar to the one below to allow 'root' logins from trusted networks only and define which other user have SSH login capability.

 AllowUsers root@127.0.* root@192.168.1.* fred barny svn

References

• http://www.debian-administration.org/articles/87
• http://www.debian-administration.org/articles/152
• http://non-gnu.uvt.nl/pub/uvt-unix-doc/ssh-harden.txt

$Id: OpenSSHServer,v 1.6 2008/04/14 10:18:16 martin Exp $