{ config, pkgs, ... }: with pkgs.lib; let cfg = config.services.openssh; cfgc = config.programs.ssh; nssModulesPath = config.system.nssModules.path; permitRootLoginCheck = v: v == "yes" || v == "without-password" || v == "forced-commands-only" || v == "no"; hostKeyTypeNames = { dsa1024 = "dsa"; rsa1024 = "rsa"; ecdsa521 = "ecdsa"; }; hostKeyTypeBits = { dsa1024 = 1024; rsa1024 = 1024; ecdsa521 = 521; }; hktn = attrByPath [cfg.hostKeyType] (throw "unknown host key type `${cfg.hostKeyType}'") hostKeyTypeNames; hktb = attrByPath [cfg.hostKeyType] (throw "unknown host key type `${cfg.hostKeyType}'") hostKeyTypeBits; knownHosts = map (h: getAttr h cfg.knownHosts) (attrNames cfg.knownHosts); knownHostsFile = pkgs.writeText "ssh_known_hosts" ( flip concatMapStrings knownHosts (h: "${concatStringsSep "," h.hostNames} ${builtins.readFile h.publicKeyFile}" ) ); userOptions = { openssh.authorizedKeys = { preserveExistingKeys = mkOption { type = types.bool; default = true; description = '' If this option is enabled, the keys specified in keys and/or keyFiles will be placed in a special section of the user's authorized_keys file and any existing keys will be preserved. That section will be regenerated each time NixOS is activated. However, if preserveExisting isn't enabled, the complete file will be generated, and any user modifications will be wiped out. ''; }; keys = mkOption { type = types.listOf types.string; default = []; description = '' A list of verbatim OpenSSH public keys that should be inserted into the user's authorized_keys file. You can combine the keys and keyFiles options. ''; }; keyFiles = mkOption { #type = types.listOf types.string; default = []; description = '' A list of files each containing one OpenSSH public keys that should be inserted into the user's authorized_keys file. You can combine the keyFiles and keys options. ''; }; }; }; mkAuthkeyScript = let marker1 = "### NixOS auto-added key. Do not edit!"; marker2 = "### NixOS will regenerate this file. Do not edit!"; users = map (userName: getAttr userName config.users.extraUsers) (attrNames config.users.extraUsers); usersWithKeys = flip filter users (u: length u.openssh.authorizedKeys.keys != 0 || length u.openssh.authorizedKeys.keyFiles != 0 ); userLoop = flip concatMapStrings usersWithKeys (u: let authKeys = concatStringsSep "," u.openssh.authorizedKeys.keys; authKeyFiles = concatStrings (map (x: " ${x}") u.openssh.authorizedKeys.keyFiles); preserveExisting = if u.openssh.authorizedKeys.preserveExistingKeys then "true" else "false"; in '' mkAuthKeysFile "${u.name}" "${authKeys}" "${authKeyFiles}" "${preserveExisting}" '' ); in '' mkAuthKeysFile() { local userName="$1" local authKeys="$2" local authKeyFiles="$3" local preserveExisting="$4" eval homeDir=~$userName if ! [ -d "$homeDir" ]; then echo "User $userName does not exist" return fi if ! [ -d "$homeDir/.ssh" ]; then mkdir -v -m 700 "$homeDir/.ssh" chown "$userName":users "$homeDir/.ssh" fi local authKeysFile="$homeDir/.ssh/authorized_keys" touch "$authKeysFile" if [ "$preserveExisting" == false ]; then rm -f "$authKeysFile" echo "${marker2}" > "$authKeysFile" else sed -i '/${marker1}/ d' "$authKeysFile" fi IFS=, for f in $authKeys; do echo "$f ${marker1}" >> "$authKeysFile" done unset IFS for f in $authKeyFiles; do if [ -f "$f" ]; then echo "$(cat "$f") ${marker1}" >> "$authKeysFile" fi done chown "$userName" "$authKeysFile" } ${userLoop} ''; in { ###### interface options = { services.openssh = { enable = mkOption { default = false; description = '' Whether to enable the OpenSSH secure shell daemon, which allows secure remote logins. ''; }; forwardX11 = mkOption { default = cfgc.setXAuthLocation; description = '' Whether to allow X11 connections to be forwarded. ''; }; allowSFTP = mkOption { default = true; description = '' Whether to enable the SFTP subsystem in the SSH daemon. This enables the use of commands such as sftp and sshfs. ''; }; permitRootLogin = mkOption { default = "without-password"; check = permitRootLoginCheck; description = '' Whether the root user can login using ssh. Valid values are yes, without-password, forced-commands-only or no. ''; }; gatewayPorts = mkOption { default = "no"; description = '' Specifies whether remote hosts are allowed to connect to ports forwarded for the client. See sshd_config 5. ''; }; ports = mkOption { default = [22]; description = '' Specifies on which ports the SSH daemon listens. ''; }; usePAM = mkOption { default = true; description = '' Specifies whether the OpenSSH daemon uses PAM to authenticate login attempts. ''; }; passwordAuthentication = mkOption { default = true; description = '' Specifies whether password authentication is allowed. Note that setting this value to false is most probably not going to have the desired effect unless usePAM is disabled as well. ''; }; challengeResponseAuthentication = mkOption { default = true; description = '' Specifies whether challenge/response authentication is allowed. ''; }; hostKeyType = mkOption { default = "dsa1024"; description = '' Type of host key to generate (dsa1024/rsa1024/ecdsa521), if the file specified by hostKeyPath does not exist when the service starts. ''; }; hostKeyPath = mkOption { default = "/etc/ssh/ssh_host_${hktn}_key"; description = '' Path to the server's private key. If there is no key file on this path, it will be generated when the service is started for the first time. Otherwise, the ssh daemon will use the specified key directly in-place. ''; }; extraConfig = mkOption { default = ""; description = "Verbatim contents of sshd_config."; }; knownHosts = mkOption { default = {}; type = types.loaOf types.optionSet; description = '' The set of system-wide known SSH hosts. ''; example = [ { hostNames = [ "myhost" "myhost.mydomain.com" "10.10.1.4" ]; publicKeyFile = ./pubkeys/myhost_ssh_host_dsa_key.pub; } { hostNames = [ "myhost2" ]; publicKeyFile = ./pubkeys/myhost2_ssh_host_dsa_key.pub; } ]; options = { hostNames = mkOption { type = types.listOf types.string; default = []; description = '' A list of host names and/or IP numbers used for accessing the host's ssh service. ''; }; publicKeyFile = mkOption { description = '' The path to the public key file for the host. The public key file is read at build time and saved in the Nix store. You can fetch a public key file from a running SSH server with the ssh-keyscan command. ''; }; }; }; }; users.extraUsers = mkOption { options = [ userOptions ]; }; }; ###### implementation config = mkIf config.services.openssh.enable { users.extraUsers = singleton { name = "sshd"; uid = config.ids.uids.sshd; description = "SSH privilege separation user"; home = "/var/empty"; }; environment.etc = [ { source = "${pkgs.openssh}/etc/ssh/moduli"; target = "ssh/moduli"; } { source = knownHostsFile; target = "ssh/ssh_known_hosts"; } ]; boot.systemd.services."set-ssh-keys" = { description = "Update authorized SSH keys"; wantedBy = [ "multi-user.target" ]; script = mkAuthkeyScript; serviceConfig.Type = "oneshot"; serviceConfig.RemainAfterExit = true; }; boot.systemd.services.sshd = { description = "SSH Daemon"; wantedBy = [ "multi-user.target" ]; after = [ "set-ssh-keys.service" ]; path = [ pkgs.openssh ]; environment.LD_LIBRARY_PATH = nssModulesPath; environment.LOCALE_ARCHIVE = "/run/current-system/sw/lib/locale/locale-archive"; preStart = '' mkdir -m 0755 -p /etc/ssh if ! test -f ${cfg.hostKeyPath}; then ssh-keygen -t ${hktn} -b ${toString hktb} -f ${cfg.hostKeyPath} -N "" fi ''; serviceConfig = { ExecStart = "${pkgs.openssh}/sbin/sshd -h ${cfg.hostKeyPath} " + "-f ${pkgs.writeText "sshd_config" cfg.extraConfig}"; Restart = "always"; Type = "forking"; KillMode = "process"; PIDFile = "/run/sshd.pid"; }; }; networking.firewall.allowedTCPPorts = cfg.ports; security.pam.services = optional cfg.usePAM { name = "sshd"; startSession = true; }; services.openssh.extraConfig = '' PidFile /run/sshd.pid Protocol 2 UsePAM ${if cfg.usePAM then "yes" else "no"} ${concatMapStrings (port: '' Port ${toString port} '') cfg.ports} ${optionalString cfgc.setXAuthLocation '' XAuthLocation ${pkgs.xorg.xauth}/bin/xauth ''} ${if cfg.forwardX11 then '' X11Forwarding yes '' else '' X11Forwarding no ''} ${optionalString cfg.allowSFTP '' Subsystem sftp ${pkgs.openssh}/libexec/sftp-server ''} PermitRootLogin ${cfg.permitRootLogin} GatewayPorts ${cfg.gatewayPorts} PasswordAuthentication ${if cfg.passwordAuthentication then "yes" else "no"} ChallengeResponseAuthentication ${if cfg.challengeResponseAuthentication then "yes" else "no"} ''; assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true; message = "cannot enable X11 forwarding without setting xauth location";}]; }; }