Managing SSH

Configuring Key-based Authentication

• generate key
• ssh-keygen -t dsa
• copy key to another server
• ssh-copy-id server2
• ssh without typing the key passphrase
• ssh-agent /bin/bash
• ssh-add

[root@server6 ~]# ssh-agent /bin/bash

[root@server6 ~]# ssh-add

Enter passphrase for /root/.ssh/id_dsa:

Identity added: /root/.ssh/id_dsa (/root/.ssh/id_dsa)

[root@server6 ~]# ssh server7

Last login: Wed Apr 27 17:20:44 2016 from 192.168.23.148

Changing ssh port

• vim /etc/ssh/sshd_config
• Port 2022
• semanage port -a -t ssh_port_t -p tcp 2022
• semanage port -l|grep ssh
• ssh_port_t                     tcp      2022, 22
• firewall-cmd --permanent --add-port=2022/tcp
• firewall-cmd --reload

Creating SSH Tunnels

• on server1
• ssh -fNL 4444:server8.example.com:80 root@server7.example.com -p 2022
• elinks http://localhost:4444

[root@server6 ~]# netstat -tulpen|grep -i ssh

tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      0          22725      1694/sshd

tcp        0      0 127.0.0.1:4444          0.0.0.0:*               LISTEN      0          174870     15288/ssh

tcp6       0      0 :::22                   :::*                    LISTEN      0          22734      1694/sshd

tcp6       0      0 ::1:4444                :::*                    LISTEN      0          174869     15288/ssh

• ssh -fNL 2020:www.sandervanvugt.nl:80 root@server8.example.com
• elinks http://www.sandervanvugt.nl:2020