pyrox.dev
1# Configuration for the pwdutils suite of tools: passwd, useradd, etc.
2{
3 config,
4 lib,
5 utils,
6 pkgs,
7 ...
8}:
9let
10 cfg = config.security.loginDefs;
11in
12{
13 options = {
14
15 security.shadow.enable = lib.mkEnableOption "" // {
16 default = true;
17 description = ''
18 Enable the shadow authentication suite, which provides critical programs such as su, login, passwd.
19
20 Note: This is currently experimental. Only disable this if you're
21 confident that you can recover your system if it breaks.
22 '';
23 };
24
25 security.loginDefs = {
26 package = lib.mkPackageOption pkgs "shadow" { };
27
28 chfnRestrict = lib.mkOption {
29 description = ''
30 Use chfn SUID to allow non-root users to change their account GECOS information.
31 '';
32 type = lib.types.nullOr lib.types.str;
33 default = null;
34 };
35
36 settings = lib.mkOption {
37 description = ''
38 Config options for the /etc/login.defs file, that defines
39 the site-specific configuration for the shadow password suite.
40 See {manpage}`login.defs(5)` man page for available options.
41 '';
42 type = lib.types.submodule {
43 freeformType = (pkgs.formats.keyValue { }).type;
44 /*
45 There are three different sources for user/group id ranges, each of which gets
46 used by different programs:
47 - The login.defs file, used by the useradd, groupadd and newusers commands
48 - The update-users-groups.pl file, used by NixOS in the activation phase to
49 decide on which ids to use for declaratively defined users without a static
50 id
51 - Systemd compile time options -Dsystem-uid-max= and -Dsystem-gid-max=, used
52 by systemd for features like ConditionUser=@system and systemd-sysusers
53 */
54 options = {
55 DEFAULT_HOME = lib.mkOption {
56 description = "Indicate if login is allowed if we can't cd to the home directory.";
57 default = "yes";
58 type = lib.types.enum [
59 "yes"
60 "no"
61 ];
62 };
63
64 ENCRYPT_METHOD = lib.mkOption {
65 description = "This defines the system default encryption algorithm for encrypting passwords.";
66 # The default crypt() method, keep in sync with the PAM default
67 default = "YESCRYPT";
68 type = lib.types.enum [
69 "YESCRYPT"
70 "SHA512"
71 "SHA256"
72 "MD5"
73 "DES"
74 ];
75 };
76
77 SYS_UID_MIN = lib.mkOption {
78 description = "Range of user IDs used for the creation of system users by useradd or newusers.";
79 default = 400;
80 type = lib.types.int;
81 };
82
83 SYS_UID_MAX = lib.mkOption {
84 description = "Range of user IDs used for the creation of system users by useradd or newusers.";
85 default = 999;
86 type = lib.types.int;
87 };
88
89 UID_MIN = lib.mkOption {
90 description = "Range of user IDs used for the creation of regular users by useradd or newusers.";
91 default = 1000;
92 type = lib.types.int;
93 };
94
95 UID_MAX = lib.mkOption {
96 description = "Range of user IDs used for the creation of regular users by useradd or newusers.";
97 default = 29999;
98 type = lib.types.int;
99 };
100
101 SYS_GID_MIN = lib.mkOption {
102 description = "Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers";
103 default = 400;
104 type = lib.types.int;
105 };
106
107 SYS_GID_MAX = lib.mkOption {
108 description = "Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers";
109 default = 999;
110 type = lib.types.int;
111 };
112
113 GID_MIN = lib.mkOption {
114 description = "Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.";
115 default = 1000;
116 type = lib.types.int;
117 };
118
119 GID_MAX = lib.mkOption {
120 description = "Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.";
121 default = 29999;
122 type = lib.types.int;
123 };
124
125 TTYGROUP = lib.mkOption {
126 description = ''
127 The terminal permissions: the login tty will be owned by the TTYGROUP group,
128 and the permissions will be set to TTYPERM'';
129 default = "tty";
130 type = lib.types.str;
131 };
132
133 TTYPERM = lib.mkOption {
134 description = ''
135 The terminal permissions: the login tty will be owned by the TTYGROUP group,
136 and the permissions will be set to TTYPERM'';
137 default = "0620";
138 type = lib.types.str;
139 };
140
141 # Ensure privacy for newly created home directories.
142 UMASK = lib.mkOption {
143 description = "The file mode creation mask is initialized to this value.";
144 default = "077";
145 type = lib.types.str;
146 };
147 };
148 };
149 default = { };
150 };
151 };
152
153 users.defaultUserShell = lib.mkOption {
154 description = ''
155 This option defines the default shell assigned to user
156 accounts. This can be either a full system path or a shell package.
157
158 This must not be a store path, since the path is
159 used outside the store (in particular in /etc/passwd).
160 '';
161 example = lib.literalExpression "pkgs.zsh";
162 type = lib.types.either lib.types.path lib.types.shellPackage;
163 };
164 };
165
166 ###### implementation
167
168 config = lib.mkMerge [
169 {
170 assertions = [
171 {
172 assertion = config.security.shadow.enable || config.services.greetd.enable;
173 message = "You must enable at least one VT login method, either security.shadow.enable or services.greetd.enable";
174 }
175 ];
176 }
177 (lib.mkIf config.security.shadow.enable {
178 assertions = [
179 {
180 assertion = cfg.settings.SYS_UID_MIN <= cfg.settings.SYS_UID_MAX;
181 message = "SYS_UID_MIN must be less than or equal to SYS_UID_MAX";
182 }
183 {
184 assertion = cfg.settings.UID_MIN <= cfg.settings.UID_MAX;
185 message = "UID_MIN must be less than or equal to UID_MAX";
186 }
187 {
188 assertion = cfg.settings.SYS_GID_MIN <= cfg.settings.SYS_GID_MAX;
189 message = "SYS_GID_MIN must be less than or equal to SYS_GID_MAX";
190 }
191 {
192 assertion = cfg.settings.GID_MIN <= cfg.settings.GID_MAX;
193 message = "GID_MIN must be less than or equal to GID_MAX";
194 }
195 ];
196
197 security.loginDefs.settings.CHFN_RESTRICT = lib.mkIf (cfg.chfnRestrict != null) cfg.chfnRestrict;
198
199 environment.systemPackages =
200 lib.optional config.users.mutableUsers cfg.package
201 ++ lib.optional (lib.types.shellPackage.check config.users.defaultUserShell) config.users.defaultUserShell
202 ++ lib.optional (cfg.chfnRestrict != null) pkgs.util-linux;
203
204 environment.etc =
205 # Create custom toKeyValue generator
206 # see https://man7.org/linux/man-pages/man5/login.defs.5.html for config specification
207 let
208 toKeyValue = lib.generators.toKeyValue {
209 mkKeyValue = lib.generators.mkKeyValueDefault { } " ";
210 };
211 in
212 {
213 # /etc/login.defs: global configuration for pwdutils.
214 # You cannot login without it!
215 "login.defs".source = pkgs.writeText "login.defs" (toKeyValue cfg.settings);
216
217 # /etc/default/useradd: configuration for useradd.
218 "default/useradd".source = pkgs.writeText "useradd" ''
219 GROUP=100
220 HOME=/home
221 SHELL=${utils.toShellPath config.users.defaultUserShell}
222 '';
223 };
224
225 security.pam.services = {
226 chsh.rootOK = true;
227 chfn.rootOK = true;
228 su = {
229 rootOK = true;
230 forwardXAuth = true;
231 logFailures = true;
232 };
233 passwd = { };
234 # Note: useradd, groupadd etc. aren't setuid root, so it
235 # doesn't really matter what the PAM config says as long as it
236 # lets root in.
237 useradd.rootOK = true;
238 usermod.rootOK = true;
239 userdel.rootOK = true;
240 groupadd.rootOK = true;
241 groupmod.rootOK = true;
242 groupmems.rootOK = true;
243 groupdel.rootOK = true;
244 login = {
245 startSession = true;
246 allowNullPassword = true;
247 showMotd = true;
248 updateWtmp = true;
249 };
250 chpasswd.rootOK = true;
251 };
252
253 security.wrappers =
254 let
255 mkSetuidRoot = source: {
256 setuid = true;
257 owner = "root";
258 group = "root";
259 inherit source;
260 };
261 in
262 {
263 su = mkSetuidRoot "${cfg.package.su}/bin/su";
264 sg = mkSetuidRoot "${cfg.package.out}/bin/sg";
265 newgrp = mkSetuidRoot "${cfg.package.out}/bin/newgrp";
266 newuidmap = mkSetuidRoot "${cfg.package.out}/bin/newuidmap";
267 newgidmap = mkSetuidRoot "${cfg.package.out}/bin/newgidmap";
268 }
269 // lib.optionalAttrs config.users.mutableUsers {
270 chsh = mkSetuidRoot "${cfg.package.out}/bin/chsh";
271 passwd = mkSetuidRoot "${cfg.package.out}/bin/passwd";
272 };
273 })
274 ];
275}