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{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.security.doas;
inherit (pkgs) doas;
mkUsrString = user: toString user;
mkGrpString = group: ":${toString group}";
mkOpts = rule: concatStringsSep " " [
(optionalString rule.noPass "nopass")
(optionalString rule.noLog "nolog")
(optionalString rule.persist "persist")
(optionalString rule.keepEnv "keepenv")
"setenv { SSH_AUTH_SOCK TERMINFO TERMINFO_DIRS ${concatStringsSep " " rule.setEnv} }"
];
mkArgs = rule:
if (isNull rule.args) then ""
else if (length rule.args == 0) then "args"
else "args ${concatStringsSep " " rule.args}";
mkRule = rule:
let
opts = mkOpts rule;
as = optionalString (!isNull rule.runAs) "as ${rule.runAs}";
cmd = optionalString (!isNull rule.cmd) "cmd ${rule.cmd}";
args = mkArgs rule;
in
optionals (length cfg.extraRules > 0) [
(
optionalString (length rule.users > 0)
(map (usr: "permit ${opts} ${mkUsrString usr} ${as} ${cmd} ${args}") rule.users)
)
(
optionalString (length rule.groups > 0)
(map (grp: "permit ${opts} ${mkGrpString grp} ${as} ${cmd} ${args}") rule.groups)
)
];
in
{
###### interface
options.security.doas = {
enable = mkOption {
type = with types; bool;
default = false;
description = ''
Whether to enable the <command>doas</command> command, which allows
non-root users to execute commands as root.
'';
};
wheelNeedsPassword = mkOption {
type = with types; bool;
default = true;
description = ''
Whether users of the <code>wheel</code> group must provide a password to
run commands as super user via <command>doas</command>.
'';
};
extraRules = mkOption {
default = [];
description = ''
Define specific rules to be set in the
<filename>/etc/doas.conf</filename> file. More specific rules should
come after more general ones in order to yield the expected behavior.
You can use <code>mkBefore</code> and/or <code>mkAfter</code> to ensure
this is the case when configuration options are merged.
'';
example = literalExpression ''
[
# Allow execution of any command by any user in group doas, requiring
# a password and keeping any previously-defined environment variables.
{ groups = [ "doas" ]; noPass = false; keepEnv = true; }
# Allow execution of "/home/root/secret.sh" by user `backup` OR user
# `database` OR any member of the group with GID `1006`, without a
# password.
{ users = [ "backup" "database" ]; groups = [ 1006 ];
cmd = "/home/root/secret.sh"; noPass = true; }
# Allow any member of group `bar` to run `/home/baz/cmd1.sh` as user
# `foo` with argument `hello-doas`.
{ groups = [ "bar" ]; runAs = "foo";
cmd = "/home/baz/cmd1.sh"; args = [ "hello-doas" ]; }
# Allow any member of group `bar` to run `/home/baz/cmd2.sh` as user
# `foo` with no arguments.
{ groups = [ "bar" ]; runAs = "foo";
cmd = "/home/baz/cmd2.sh"; args = [ ]; }
# Allow user `abusers` to execute "nano" and unset the value of
# SSH_AUTH_SOCK, override the value of ALPHA to 1, and inherit the
# value of BETA from the current environment.
{ users = [ "abusers" ]; cmd = "nano";
setEnv = [ "-SSH_AUTH_SOCK" "ALPHA=1" "BETA" ]; }
]
'';
type = with types; listOf (
submodule {
options = {
noPass = mkOption {
type = with types; bool;
default = false;
description = ''
If <code>true</code>, the user is not required to enter a
password.
'';
};
noLog = mkOption {
type = with types; bool;
default = false;
description = ''
If <code>true</code>, successful executions will not be logged
to
<citerefentry><refentrytitle>syslogd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
'';
};
persist = mkOption {
type = with types; bool;
default = false;
description = ''
If <code>true</code>, do not ask for a password again for some
time after the user successfully authenticates.
'';
};
keepEnv = mkOption {
type = with types; bool;
default = false;
description = ''
If <code>true</code>, environment variables other than those
listed in
<citerefentry><refentrytitle>doas</refentrytitle><manvolnum>1</manvolnum></citerefentry>
are kept when creating the environment for the new process.
'';
};
setEnv = mkOption {
type = with types; listOf str;
default = [];
description = ''
Keep or set the specified variables. Variables may also be
removed with a leading '-' or set using
<code>variable=value</code>. If the first character of
<code>value</code> is a '$', the value to be set is taken from
the existing environment variable of the indicated name. This
option is processed after the default environment has been
created.
NOTE: All rules have <code>setenv { SSH_AUTH_SOCK }</code> by
default. To prevent <code>SSH_AUTH_SOCK</code> from being
inherited, add <code>"-SSH_AUTH_SOCK"</code> anywhere in this
list.
'';
};
users = mkOption {
type = with types; listOf (either str int);
default = [];
description = "The usernames / UIDs this rule should apply for.";
};
groups = mkOption {
type = with types; listOf (either str int);
default = [];
description = "The groups / GIDs this rule should apply for.";
};
runAs = mkOption {
type = with types; nullOr str;
default = null;
description = ''
Which user or group the specified command is allowed to run as.
When set to <code>null</code> (the default), all users are
allowed.
A user can be specified using just the username:
<code>"foo"</code>. It is also possible to only allow running as
a specific group with <code>":bar"</code>.
'';
};
cmd = mkOption {
type = with types; nullOr str;
default = null;
description = ''
The command the user is allowed to run. When set to
<code>null</code> (the default), all commands are allowed.
NOTE: It is best practice to specify absolute paths. If a
relative path is specified, only a restricted PATH will be
searched.
'';
};
args = mkOption {
type = with types; nullOr (listOf str);
default = null;
description = ''
Arguments that must be provided to the command. When set to
<code>[]</code>, the command must be run without any arguments.
'';
};
};
}
);
};
extraConfig = mkOption {
type = with types; lines;
default = "";
description = ''
Extra configuration text appended to <filename>doas.conf</filename>.
'';
};
};
###### implementation
config = mkIf cfg.enable {
security.doas.extraRules = mkOrder 600 [
{
groups = [ "wheel" ];
noPass = !cfg.wheelNeedsPassword;
}
];
security.wrappers.doas =
{ setuid = true;
owner = "root";
group = "root";
source = "${doas}/bin/doas";
};
environment.systemPackages = [
doas
];
security.pam.services.doas = {
allowNullPassword = true;
sshAgentAuth = true;
};
environment.etc."doas.conf" = {
source = pkgs.runCommand "doas-conf"
{
src = pkgs.writeText "doas-conf-in" ''
# To modify this file, set the NixOS options
# `security.doas.extraRules` or `security.doas.extraConfig`. To
# completely replace the contents of this file, use
# `environment.etc."doas.conf"`.
# "root" is allowed to do anything.
permit nopass keepenv root
# extraRules
${concatStringsSep "\n" (lists.flatten (map mkRule cfg.extraRules))}
# extraConfig
${cfg.extraConfig}
'';
preferLocalBuild = true;
}
# Make sure that the doas.conf file is syntactically valid.
"${pkgs.buildPackages.doas}/bin/doas -C $src && cp $src $out";
mode = "0440";
};
};
meta.maintainers = with maintainers; [ cole-h ];
}
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