First we create root’s keys.
Note: We have to leave the passphrase blank as we will be using the keys to auto-authenticate to the Dropbox Relay when creating our SSH tunnels.
ssh-keygen -t rsa
Override the default /root/.ssh/id_rsa with /root/.ssh/dbox-01.id_rsa or something similar. Just use the same naming convention throughout. Each Dropbox Server you deploy will have a unique key identifier.
The output should look something like the following.
Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): /root/.ssh/dbox-01.id_rsa Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/dbox-01.id_rsa. Your public key has been saved in /root/.ssh/dbox-01.id_rsa.pub. The key fingerprint is: SHA256:ElmBhJko2aCYALXjvuqzf1Qf+up+3hiFOhdeUlQ//Wg root@dbox-01 The key's randomart image is: +---[RSA 2048]----+ |==.. =..o. ... | |*.o.+ .o . . .| |+.o o . o.| | . . o .o .o| | . o S+.o E .| | . . oo.= . | | . . o.+ | | . . . oo+ | |o+=.. o++o . | +----[SHA256]-----+
Now setup the SSH server itself.
First, remove default created keys.
mkdir /etc/ssh/oldkeys mv /etc/ssh/ssh_host* /etc/ssh/oldkeys/
We tweak the SSH configuration file to remove some weak protocols, require key authentication for root, and listen only on localhost.
# Package generated configuration file # See the sshd_config(5) manpage for details # What ports, IPs and protocols we listen for Port 22 # Use these options to restrict which interfaces/protocols sshd will bind to #ListenAddress :: ListenAddress 127.0.0.1 Protocol 2 # HostKeys for protocol version 2 HostKey /etc/ssh/ssh_host_rsa_key #HostKey /etc/ssh/ssh_host_dsa_key #HostKey /etc/ssh/ssh_host_ecdsa_key #HostKey /etc/ssh/ssh_host_ed25519_key #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 #ServerKeyBits 1024 # Logging SyslogFacility AUTH LogLevel INFO # Authentication: LoginGraceTime 120 PermitRootLogin prohibit-password StrictModes yes RSAAuthentication yes PubkeyAuthentication yes #AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication #IgnoreUserKnownHosts yes # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords PasswordAuthentication no # Kerberos options #KerberosAuthentication no #KerberosGetAFSToken no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes # GSSAPI options #GSSAPIAuthentication no #GSSAPICleanupCredentials yes X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes #UseLogin no #MaxStartups 10:30:60 #Banner /etc/issue.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication and # PasswordAuthentication. Depending on your PAM configuration, # PAM authentication via ChallengeResponseAuthentication may bypass # the setting of "PermitRootLogin without-password". # If you just want the PAM account and session checks to run without # PAM authentication, then enable this but set PasswordAuthentication # and ChallengeResponseAuthentication to 'no'. UsePAM yes
Reconfigure the SSH server to generate new keys.
Make sure SSH is configured to autostart
systemctl enable ssh