nixpkgs/modules/services/networking/ssh/sshd.nix

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{ 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
<literal>keys</literal> and/or <literal>keyFiles</literal> 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
<literal>preserveExisting</literal> 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 <literal>keys</literal> and
<literal>keyFiles</literal> 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 <literal>keyFiles</literal> and
<literal>keys</literal> 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 <command>sftp</command> and
<command>sshfs</command>.
'';
};
permitRootLogin = mkOption {
default = "without-password";
check = permitRootLoginCheck;
description = ''
Whether the root user can login using ssh. Valid values are
<literal>yes</literal>, <literal>without-password</literal>,
<literal>forced-commands-only</literal> or
<literal>no</literal>.
'';
};
gatewayPorts = mkOption {
default = "no";
description = ''
Specifies whether remote hosts are allowed to connect to
ports forwarded for the client. See
<citerefentry><refentrytitle>sshd_config</refentrytitle>
<manvolnum>5</manvolnum></citerefentry>.
'';
};
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 <literal>false</literal> is most
probably not going to have the desired effect unless
<literal>usePAM</literal> 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 <literal>hostKeyPath</literal> 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 <filename>sshd_config</filename>.";
};
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 <literal>ssh-keyscan</literal> 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 =
2012-07-19 23:33:22 +02:00
{ 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; showMotd = true; };
services.openssh.extraConfig =
''
PidFile /run/sshd.pid
Protocol 2
UsePAM ${if cfg.usePAM then "yes" else "no"}
AddressFamily ${if config.networking.enableIPv6 then "any" else "inet"}
${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"}
PrintMotd no # handled by pam_motd
'';
assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true;
message = "cannot enable X11 forwarding without setting xauth location";}];
};
}