ssh

Key Generation

ssh-keygen -f id_rsa
# private key: id_rsa
# public key: id_rsa.pub

Key Insertion for root user

1. Generate key

2. copy id_rsa.pub to /root/.ssh/authorized_keys

Perms Error

1. For private key file:

   1. chmod 600 id_rsa

2. For authorized_keys file:

   1. chmod 700 /root/.ssh

   2. chmod 700 /root/.ssh/authorized_keys

flags for common errors

# flag for algorithm
-okexAlgorithms=+diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1

# flag for public key
-oPubkeyAcceptedKeyTypes=+ssh-dss

# flag for cipher
-c aes128-cbc

Kali ssh server (for incoming connection)

apt install openssh-server

# backup default keys; generate new pair
mkdir /etc/ssh/default_keys; mv /etc/ssh/ssh_host_* /etc/ssh/default_keys/
dpkg-reconfigure openssh-server

# change /etc/ssh/sshd_config
PubkeyAuthentication yes
PasswordAuthentication no
PermitRootLogin no

# start / stop / status service
systemctl [enable|disable] ssh.service
systemctl [start|status|stop] ssh.service

References

• lmgsecurity.com/enable-start-ssh-kali-linux/