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