Sshbastion

ref

• https://aws.amazon.com/blogs/security/how-to-record-ssh-sessions-established-through-a-bastion-host/
  • if using this script use
  • chattr +a /var/log/bastion/

sshd basic

• make sure ssh root is cert only or disabled
• PermitRootLogin prohibit-password
• AllowTcpForwarding no
• X11Forwarding no
• Only allow certain group to ssh
• AllowGroups sshusers

proc

Make sure users can't see other users processes:

• proc /proc proc defaults,hidepid=2 0 0

firewall to restrict outgoing traffic from bastion

#!/bin/bash
iptables --flush OUTPUT
iptables --append OUTPUT -d security.debian.org -j ACCEPT
iptables --append OUTPUT -d ftp.dk.debian.org -j ACCEPT
iptables --append OUTPUT -d 192.168.12.1 -p tcp --dport 22 -j DROP
iptables --append OUTPUT -m state --state NEW -p tcp --dport 22 -j ACCEPT
iptables --append OUTPUT -m state -d 192.168.12.1 -p udp --dport 53 -j ACCEPT
iptables --append OUTPUT -m state -d 192.168.12.1 -p tcp --dport 53 -j ACCEPT
iptables --append OUTPUT -m -d 192.168.12.1 -p udp --dport 67:68 -j ACCEPT
iptables --append OUTOUT -p icmp -j ACCEPT
iptables --append OUTPUT -m state --state NEW -j REJECT

PAM

Secure bastionhost harden passwords

• apt install libpam-pwquality
• add password requisite pam_pwquality.so minlen=12 retry=3
• to /etc/pam.d/common-passwd

• apt install geoip-database-extra libpam-geoip
• see https://github.com/vetinari/pam_geoip/blob/master/geoip.conf and modify /etc/security/geoip.conf
• add account required pam_geoip.so to /etc/pam.d/common-account