nixpkgs/nixos/modules/security/doas.nix
pennae 16102dce2f nixos/*: replace <code> in option docs with <literal>
markdown can't represent the difference without another extension and
both the html manual and the manpage render them the same, so keeping the
distinction is not very useful on its own. with the distinction removed
we can automatically convert many options that use <code> tags to markdown.

the manpage remains unchanged, html manual does not render
differently (but class names on code tags do change from "code" to "literal").
2022-08-03 21:03:23 +02:00

289 lines
9.3 KiB
Nix

{ 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 = lib.mdDoc ''
Whether to enable the {command}`doas` command, which allows
non-root users to execute commands as root.
'';
};
wheelNeedsPassword = mkOption {
type = with types; bool;
default = true;
description = ''
Whether users of the <literal>wheel</literal> 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 <literal>mkBefore</literal> and/or <literal>mkAfter</literal> 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 <literal>true</literal>, the user is not required to enter a
password.
'';
};
noLog = mkOption {
type = with types; bool;
default = false;
description = ''
If <literal>true</literal>, 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 <literal>true</literal>, 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 <literal>true</literal>, 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
<literal>variable=value</literal>. If the first character of
<literal>value</literal> 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 <literal>setenv { SSH_AUTH_SOCK }</literal> by
default. To prevent <literal>SSH_AUTH_SOCK</literal> from being
inherited, add <literal>"-SSH_AUTH_SOCK"</literal> anywhere in this
list.
'';
};
users = mkOption {
type = with types; listOf (either str int);
default = [];
description = lib.mdDoc "The usernames / UIDs this rule should apply for.";
};
groups = mkOption {
type = with types; listOf (either str int);
default = [];
description = lib.mdDoc "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 <literal>null</literal> (the default), all users are
allowed.
A user can be specified using just the username:
<literal>"foo"</literal>. It is also possible to only allow running as
a specific group with <literal>":bar"</literal>.
'';
};
cmd = mkOption {
type = with types; nullOr str;
default = null;
description = ''
The command the user is allowed to run. When set to
<literal>null</literal> (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
<literal>[]</literal>, the command must be run without any arguments.
'';
};
};
}
);
};
extraConfig = mkOption {
type = with types; lines;
default = "";
description = lib.mdDoc ''
Extra configuration text appended to {file}`doas.conf`.
'';
};
};
###### 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 ];
}