# OpenSSH /etc/ssh/sshd_config. I am removing commented lines for this to # be more clear and if they are missed some day, just download # upstream config file or take it from any distribution. # Partially based on https://wiki.mozilla.org/Security/Guidelines/OpenSSH # where some comments are took. Some options look like I don't want to # change them to get updates when defaults change. # No environment variable is accepted for security reasons, e.g. # shellshock worked with remotely accepted environment variables. #AcceptEnv LANG LANGUAGE LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT LC_IDENTIFICATION # IPv4 & IPv6 AddressFamily any # Password based logins are disabled - only public key based logins are # allowed. AuthenticationMethods publickey # The default is to check both .ssh/authorized_keys and # .ssh/authorized_keys2 but this is overridden so installations will only # check .ssh/authorized_keys. AuthorizedKeysFile .ssh/authorized_keys # File to send to client before authentication. Banner /etc/issue.net # Disable s/key passwords. ChallengeResponseAuthentication no # If the client doesn't reply in three "pings", connection is dead. # Defaults to 3 anyway, but I add it here for clearity and # in case it decides to change in the future. ClientAliveCountMax 3 # "ping" the client every minute. ClientAliveInterval 60 # HostKeys for protocol version 2. HostKey /etc/ssh/ssh_host_ed25519_key HostKey /etc/ssh/ssh_host_rsa_key ## IF THE HOST KEYS ARE MISSING, RUN THE FOLLOWING AS ROOT: # ssh-keygen -t ed25519 -N "" -f /etc/ssh/ssh_host_ed25519_key # ssh-keygen -t rsa -N "" -f /etc/ssh/ssh_host_rsa_key # Listen on all IPv4 & IPv6 addresses. ListenAddress 0.0.0.0 ListenAddress :: # VERBOSE logging, logs user's key fingerprint on login. Needed to have a # clear audit track of which key was using to log in. LogLevel VERBOSE # Disable tunneled clear text passwords! PasswordAuthentication no # Auditing reasons, difficult to track which process belongs to which root # user. PermitRootLogin No # Listen on the following TCP ports, default 22. Port 22 # Print /etc/motd (or /etc/profile or equivalent) on login. It's already # done by PAM, so no need for duplicate MOTDs. PrintMotd no # Avoid enabling insecure protocol 1. Protocol 2 ## Enable SFTP. As the subsystem location varies, uncomment the one for the ## OS you use. ## Arch #Subsystem sftp /usr/lib/ssh/sftp-server ## Debian #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 # Use kernel sandbox mechanisms where possible in unprivilegied processes. # Systrace on OpenBSD, Seccomp on Linux, seatbelt on MacOSX/Darwin, # rlimit elsewhere. UsePrivilegeSeparation sandbox