{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.security.duosec;
boolToStr = b: if b then "yes" else "no";
configFile = ''
[duo]
ikey=${cfg.ikey}
skey=${cfg.skey}
host=${cfg.host}
${optionalString (cfg.group != "") ("group="+cfg.group)}
failmode=${cfg.failmode}
pushinfo=${boolToStr cfg.pushinfo}
autopush=${boolToStr cfg.autopush}
motd=${boolToStr cfg.motd}
prompts=${toString cfg.prompts}
accept_env_factor=${boolToStr cfg.acceptEnvFactor}
fallback_local_ip=${boolToStr cfg.fallbackLocalIP}
'';
loginCfgFile = optional cfg.ssh.enable
{ source = pkgs.writeText "login_duo.conf" configFile;
mode = "0600";
uid = config.ids.uids.sshd;
target = "duo/login_duo.conf";
};
pamCfgFile = optional cfg.pam.enable
{ source = pkgs.writeText "pam_duo.conf" configFile;
mode = "0600";
uid = config.ids.uids.sshd;
target = "duo/pam_duo.conf";
};
in
{
options = {
security.duosec = {
ssh.enable = mkOption {
type = types.bool;
default = false;
description = "If enabled, protect SSH logins with Duo Security.";
};
pam.enable = mkOption {
type = types.bool;
default = false;
description = "If enabled, protect logins with Duo Security using PAM support.";
};
ikey = mkOption {
type = types.str;
description = "Integration key.";
};
skey = mkOption {
type = types.str;
description = "Secret key.";
};
host = mkOption {
type = types.str;
description = "Duo API hostname.";
};
group = mkOption {
type = types.str;
default = "";
description = "Use Duo authentication for users only in this group.";
};
failmode = mkOption {
type = types.str;
default = "safe";
description = ''
On service or configuration errors that prevent Duo
authentication, fail "safe" (allow access) or "secure" (deny
access). The default is "safe".
'';
};
pushinfo = mkOption {
type = types.bool;
default = false;
description = ''
Include information such as the command to be executed in
the Duo Push message.
'';
};
autopush = mkOption {
type = types.bool;
default = false;
description = ''
If <literal>true</literal>, Duo Unix will automatically send
a push login request to the user’s phone, falling back on a
phone call if push is unavailable. If
<literal>false</literal>, the user will be prompted to
choose an authentication method. When configured with
<literal>autopush = yes</literal>, we recommend setting
<literal>prompts = 1</literal>.
'';
};
motd = mkOption {
type = types.bool;
default = false;
description = ''
Print the contents of <literal>/etc/motd</literal> to screen
after a successful login.
'';
};
prompts = mkOption {
type = types.int;
default = 3;
description = ''
If a user fails to authenticate with a second factor, Duo
Unix will prompt the user to authenticate again. This option
sets the maximum number of prompts that Duo Unix will
display before denying access. Must be 1, 2, or 3. Default
is 3.
For example, when <literal>prompts = 1</literal>, the user
will have to successfully authenticate on the first prompt,
whereas if <literal>prompts = 2</literal>, if the user
enters incorrect information at the initial prompt, he/she
will be prompted to authenticate again.
When configured with <literal>autopush = true</literal>, we
recommend setting <literal>prompts = 1</literal>.
'';
};
acceptEnvFactor = mkOption {
type = types.bool;
default = false;
description = ''
Look for factor selection or passcode in the
<literal>$DUO_PASSCODE</literal> environment variable before
prompting the user for input.
When $DUO_PASSCODE is non-empty, it will override
autopush. The SSH client will need SendEnv DUO_PASSCODE in
its configuration, and the SSH server will similarly need
AcceptEnv DUO_PASSCODE.
'';
};
fallbackLocalIP = mkOption {
type = types.bool;
default = false;
description = ''
Duo Unix reports the IP address of the authorizing user, for
the purposes of authorization and whitelisting. If Duo Unix
cannot detect the IP address of the client, setting
<literal>fallbackLocalIP = yes</literal> will cause Duo Unix
to send the IP address of the server it is running on.
If you are using IP whitelisting, enabling this option could
cause unauthorized logins if the local IP is listed in the
whitelist.
'';
};
allowTcpForwarding = mkOption {
type = types.bool;
default = false;
description = ''
By default, when SSH forwarding, enabling Duo Security will
disable TCP forwarding. By enabling this, you potentially
undermine some of the SSH based login security. Note this is
not needed if you use PAM.
'';
};
};
};
config = mkIf (cfg.ssh.enable || cfg.pam.enable) {
assertions =
[ { assertion = cfg.failmode == "safe" || cfg.failmode == "secure";
message = "Invalid value for failmode (must be safe or secure).";
}
{ assertion = cfg.prompts == 1 || cfg.prompts == 2 || cfg.prompts == 3;
message = "Invalid value for prompts (must be 1, 2, or 3).";
}
{ assertion = !cfg.pam.enable;
message = "PAM support is currently not implemented.";
}
];
environment.systemPackages = [ pkgs.duo-unix ];
security.setuidPrograms = [ "login_duo" ];
environment.etc = loginCfgFile ++ pamCfgFile;
/* If PAM *and* SSH are enabled, then don't do anything special.
If PAM isn't used, set the default SSH-only options. */
services.openssh.extraConfig = mkIf (cfg.ssh.enable || cfg.pam.enable) (
if cfg.pam.enable then "UseDNS no" else ''
# Duo Security configuration
ForceCommand ${config.security.wrapperDir}/login_duo
PermitTunnel no
${optionalString (!cfg.allowTcpForwarding) ''
AllowTcpForwarding no
''}
'');
};
}