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nixpkgs/nixos/modules/config/users-groups.nix
Aneesh Agrawal a709b1a373 nixos/users: Allow mutable shells for declarative users
I want to manage users centrally via declarativeUsers,
but allow users to change their shell as they please,
similar to how they can change passwords at will
if none of the password-related NixOS settings are set for their user.
2019-04-07 15:16:01 -07:00

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{ config, lib, utils, pkgs, ... }:
with lib;
let
ids = config.ids;
cfg = config.users;
passwordDescription = ''
The options <option>hashedPassword</option>,
<option>password</option> and <option>passwordFile</option>
controls what password is set for the user.
<option>hashedPassword</option> overrides both
<option>password</option> and <option>passwordFile</option>.
<option>password</option> overrides <option>passwordFile</option>.
If none of these three options are set, no password is assigned to
the user, and the user will not be able to do password logins.
If the option <option>users.mutableUsers</option> is true, the
password defined in one of the three options will only be set when
the user is created for the first time. After that, you are free to
change the password with the ordinary user management commands. If
<option>users.mutableUsers</option> is false, you cannot change
user passwords, they will always be set according to the password
options.
'';
hashedPasswordDescription = ''
To generate hashed password install <literal>mkpasswd</literal>
package and run <literal>mkpasswd -m sha-512</literal>.
'';
userOpts = { name, config, ... }: {
options = {
name = mkOption {
type = types.str;
apply = x: assert (builtins.stringLength x < 32 || abort "Username '${x}' is longer than 31 characters which is not allowed!"); x;
description = ''
The name of the user account. If undefined, the name of the
attribute set will be used.
'';
};
description = mkOption {
type = types.str;
default = "";
example = "Alice Q. User";
description = ''
A short description of the user account, typically the
user's full name. This is actually the GECOS or comment
field in <filename>/etc/passwd</filename>.
'';
};
uid = mkOption {
type = with types; nullOr int;
default = null;
description = ''
The account UID. If the UID is null, a free UID is picked on
activation.
'';
};
isSystemUser = mkOption {
type = types.bool;
default = false;
description = ''
Indicates if the user is a system user or not. This option
only has an effect if <option>uid</option> is
<option>null</option>, in which case it determines whether
the user's UID is allocated in the range for system users
(below 500) or in the range for normal users (starting at
1000).
'';
};
isNormalUser = mkOption {
type = types.bool;
default = false;
description = ''
Indicates whether this is an account for a real user. This
automatically sets <option>group</option> to
<literal>users</literal>, <option>createHome</option> to
<literal>true</literal>, <option>home</option> to
<filename>/home/<replaceable>username</replaceable></filename>,
<option>useDefaultShell</option> to <literal>true</literal>,
and <option>isSystemUser</option> to
<literal>false</literal>.
'';
};
group = mkOption {
type = types.str;
apply = x: assert (builtins.stringLength x < 32 || abort "Group name '${x}' is longer than 31 characters which is not allowed!"); x;
default = "nogroup";
description = "The user's primary group.";
};
extraGroups = mkOption {
type = types.listOf types.str;
default = [];
description = "The user's auxiliary groups.";
};
home = mkOption {
type = types.path;
default = "/var/empty";
description = "The user's home directory.";
};
cryptHomeLuks = mkOption {
type = with types; nullOr str;
default = null;
description = ''
Path to encrypted luks device that contains
the user's home directory.
'';
};
shell = mkOption {
type = types.nullOr (types.either types.shellPackage types.path);
default = pkgs.shadow;
defaultText = "pkgs.shadow";
example = literalExample "pkgs.bashInteractive";
description = ''
The path to the user's shell. Can use shell derivations,
like <literal>pkgs.bashInteractive</literal>. Dont
forget to enable your shell in
<literal>programs</literal> if necessary,
like <code>programs.zsh.enable = true;</code>.
'';
};
subUidRanges = mkOption {
type = with types; listOf (submodule subordinateUidRange);
default = [];
example = [
{ startUid = 1000; count = 1; }
{ startUid = 100001; count = 65534; }
];
description = ''
Subordinate user ids that user is allowed to use.
They are set into <filename>/etc/subuid</filename> and are used
by <literal>newuidmap</literal> for user namespaces.
'';
};
subGidRanges = mkOption {
type = with types; listOf (submodule subordinateGidRange);
default = [];
example = [
{ startGid = 100; count = 1; }
{ startGid = 1001; count = 999; }
];
description = ''
Subordinate group ids that user is allowed to use.
They are set into <filename>/etc/subgid</filename> and are used
by <literal>newgidmap</literal> for user namespaces.
'';
};
createHome = mkOption {
type = types.bool;
default = false;
description = ''
If true, the home directory will be created automatically. If this
option is true and the home directory already exists but is not
owned by the user, directory owner and group will be changed to
match the user.
'';
};
useDefaultShell = mkOption {
type = types.bool;
default = false;
description = ''
If true, the user's shell will be set to
<option>users.defaultUserShell</option>.
'';
};
hashedPassword = mkOption {
type = with types; uniq (nullOr str);
default = null;
description = ''
Specifies the hashed password for the user.
${passwordDescription}
${hashedPasswordDescription}
'';
};
password = mkOption {
type = with types; uniq (nullOr str);
default = null;
description = ''
Specifies the (clear text) password for the user.
Warning: do not set confidential information here
because it is world-readable in the Nix store. This option
should only be used for public accounts.
${passwordDescription}
'';
};
passwordFile = mkOption {
type = with types; uniq (nullOr string);
default = null;
description = ''
The full path to a file that contains the user's password. The password
file is read on each system activation. The file should contain
exactly one line, which should be the password in an encrypted form
that is suitable for the <literal>chpasswd -e</literal> command.
${passwordDescription}
'';
};
initialHashedPassword = mkOption {
type = with types; uniq (nullOr str);
default = null;
description = ''
Specifies the initial hashed password for the user, i.e. the
hashed password assigned if the user does not already
exist. If <option>users.mutableUsers</option> is true, the
password can be changed subsequently using the
<command>passwd</command> command. Otherwise, it's
equivalent to setting the <option>hashedPassword</option> option.
${hashedPasswordDescription}
'';
};
initialPassword = mkOption {
type = with types; uniq (nullOr str);
default = null;
description = ''
Specifies the initial password for the user, i.e. the
password assigned if the user does not already exist. If
<option>users.mutableUsers</option> is true, the password
can be changed subsequently using the
<command>passwd</command> command. Otherwise, it's
equivalent to setting the <option>password</option>
option. The same caveat applies: the password specified here
is world-readable in the Nix store, so it should only be
used for guest accounts or passwords that will be changed
promptly.
'';
};
packages = mkOption {
type = types.listOf types.package;
default = [];
example = literalExample "[ pkgs.firefox pkgs.thunderbird ]";
description = ''
The set of packages that should be made availabe to the user.
This is in contrast to <option>environment.systemPackages</option>,
which adds packages to all users.
'';
};
};
config = mkMerge
[ { name = mkDefault name;
shell = mkIf config.useDefaultShell (mkDefault cfg.defaultUserShell);
}
(mkIf config.isNormalUser {
group = mkDefault "users";
createHome = mkDefault true;
home = mkDefault "/home/${config.name}";
useDefaultShell = mkDefault true;
isSystemUser = mkDefault false;
})
# If !mutableUsers, setting initialPassword is equivalent to
# setting password (and similarly for hashed passwords).
(mkIf (!cfg.mutableUsers && config.initialPassword != null) {
password = mkDefault config.initialPassword;
})
(mkIf (!cfg.mutableUsers && config.initialHashedPassword != null) {
hashedPassword = mkDefault config.initialHashedPassword;
})
];
};
groupOpts = { name, ... }: {
options = {
name = mkOption {
type = types.str;
description = ''
The name of the group. If undefined, the name of the attribute set
will be used.
'';
};
gid = mkOption {
type = with types; nullOr int;
default = null;
description = ''
The group GID. If the GID is null, a free GID is picked on
activation.
'';
};
members = mkOption {
type = with types; listOf string;
default = [];
description = ''
The user names of the group members, added to the
<literal>/etc/group</literal> file.
'';
};
};
config = {
name = mkDefault name;
};
};
subordinateUidRange = {
options = {
startUid = mkOption {
type = types.int;
description = ''
Start of the range of subordinate user ids that user is
allowed to use.
'';
};
count = mkOption {
type = types.int;
default = 1;
description = ''Count of subordinate user ids'';
};
};
};
subordinateGidRange = {
options = {
startGid = mkOption {
type = types.int;
description = ''
Start of the range of subordinate group ids that user is
allowed to use.
'';
};
count = mkOption {
type = types.int;
default = 1;
description = ''Count of subordinate group ids'';
};
};
};
mkSubuidEntry = user: concatStrings (
map (range: "${user.name}:${toString range.startUid}:${toString range.count}\n")
user.subUidRanges);
subuidFile = concatStrings (map mkSubuidEntry (attrValues cfg.users));
mkSubgidEntry = user: concatStrings (
map (range: "${user.name}:${toString range.startGid}:${toString range.count}\n")
user.subGidRanges);
subgidFile = concatStrings (map mkSubgidEntry (attrValues cfg.users));
idsAreUnique = set: idAttr: !(fold (name: args@{ dup, acc }:
let
id = builtins.toString (builtins.getAttr idAttr (builtins.getAttr name set));
exists = builtins.hasAttr id acc;
newAcc = acc // (builtins.listToAttrs [ { name = id; value = true; } ]);
in if dup then args else if exists
then builtins.trace "Duplicate ${idAttr} ${id}" { dup = true; acc = null; }
else { dup = false; acc = newAcc; }
) { dup = false; acc = {}; } (builtins.attrNames set)).dup;
uidsAreUnique = idsAreUnique (filterAttrs (n: u: u.uid != null) cfg.users) "uid";
gidsAreUnique = idsAreUnique (filterAttrs (n: g: g.gid != null) cfg.groups) "gid";
spec = pkgs.writeText "users-groups.json" (builtins.toJSON {
inherit (cfg) mutableUsers;
users = mapAttrsToList (_: u:
{ inherit (u)
name uid group description home createHome isSystemUser
password passwordFile hashedPassword
initialPassword initialHashedPassword;
shell = utils.toShellPath u.shell;
}) cfg.users;
groups = mapAttrsToList (n: g:
{ inherit (g) name gid;
members = g.members ++ (mapAttrsToList (n: u: u.name) (
filterAttrs (n: u: elem g.name u.extraGroups) cfg.users
));
}) cfg.groups;
});
systemShells =
let
shells = mapAttrsToList (_: u: u.shell) cfg.users;
in
filter types.shellPackage.check shells;
in {
###### interface
options = {
users.mutableUsers = mkOption {
type = types.bool;
default = true;
description = ''
If set to <literal>true</literal>, you are free to add new users and groups to the system
with the ordinary <literal>useradd</literal> and
<literal>groupadd</literal> commands. On system activation, the
existing contents of the <literal>/etc/passwd</literal> and
<literal>/etc/group</literal> files will be merged with the
contents generated from the <literal>users.users</literal> and
<literal>users.groups</literal> options.
The initial password for a user will be set
according to <literal>users.users</literal>, but existing passwords
will not be changed.
<warning><para>
If set to <literal>false</literal>, the contents of the user and
group files will simply be replaced on system activation. This also
holds for the user passwords; all changed
passwords will be reset according to the
<literal>users.users</literal> configuration on activation.
</para></warning>
'';
};
users.enforceIdUniqueness = mkOption {
type = types.bool;
default = true;
description = ''
Whether to require that no two users/groups share the same uid/gid.
'';
};
users.users = mkOption {
default = {};
type = with types; loaOf (submodule userOpts);
example = {
alice = {
uid = 1234;
description = "Alice Q. User";
home = "/home/alice";
createHome = true;
group = "users";
extraGroups = ["wheel"];
shell = "/bin/sh";
};
};
description = ''
Additional user accounts to be created automatically by the system.
This can also be used to set options for root.
'';
};
users.groups = mkOption {
default = {};
example =
{ students.gid = 1001;
hackers = { };
};
type = with types; loaOf (submodule groupOpts);
description = ''
Additional groups to be created automatically by the system.
'';
};
# FIXME: obsolete - will remove.
security.initialRootPassword = mkOption {
type = types.str;
default = "!";
example = "";
visible = false;
};
};
###### implementation
config = {
users.users = {
root = {
uid = ids.uids.root;
description = "System administrator";
home = "/root";
shell = mkDefault cfg.defaultUserShell;
group = "root";
initialHashedPassword = mkDefault config.security.initialRootPassword;
};
nobody = {
uid = ids.uids.nobody;
description = "Unprivileged account (don't use!)";
group = "nogroup";
};
};
users.groups = {
root.gid = ids.gids.root;
wheel.gid = ids.gids.wheel;
disk.gid = ids.gids.disk;
kmem.gid = ids.gids.kmem;
tty.gid = ids.gids.tty;
floppy.gid = ids.gids.floppy;
uucp.gid = ids.gids.uucp;
lp.gid = ids.gids.lp;
cdrom.gid = ids.gids.cdrom;
tape.gid = ids.gids.tape;
audio.gid = ids.gids.audio;
video.gid = ids.gids.video;
dialout.gid = ids.gids.dialout;
nogroup.gid = ids.gids.nogroup;
users.gid = ids.gids.users;
nixbld.gid = ids.gids.nixbld;
utmp.gid = ids.gids.utmp;
adm.gid = ids.gids.adm;
input.gid = ids.gids.input;
kvm.gid = ids.gids.kvm;
render.gid = ids.gids.render;
};
system.activationScripts.users = stringAfter [ "stdio" ]
''
install -m 0700 -d /root
install -m 0755 -d /home
${pkgs.perl}/bin/perl -w \
-I${pkgs.perlPackages.FileSlurp}/${pkgs.perl.libPrefix} \
-I${pkgs.perlPackages.JSON}/${pkgs.perl.libPrefix} \
${./update-users-groups.pl} ${spec}
'';
# for backwards compatibility
system.activationScripts.groups = stringAfter [ "users" ] "";
# Install all the user shells
environment.systemPackages = systemShells;
environment.etc = {
"subuid" = {
text = subuidFile;
mode = "0644";
};
"subgid" = {
text = subgidFile;
mode = "0644";
};
} // (mapAttrs' (name: { packages, ... }: {
name = "profiles/per-user/${name}";
value.source = pkgs.buildEnv {
name = "user-environment";
paths = packages;
inherit (config.environment) pathsToLink extraOutputsToInstall;
inherit (config.system.path) ignoreCollisions postBuild;
};
}) (filterAttrs (_: u: u.packages != []) cfg.users));
environment.profiles = [ "/etc/profiles/per-user/$USER" ];
assertions = [
{ assertion = !cfg.enforceIdUniqueness || (uidsAreUnique && gidsAreUnique);
message = "UIDs and GIDs must be unique!";
}
{ # If mutableUsers is false, to prevent users creating a
# configuration that locks them out of the system, ensure that
# there is at least one "privileged" account that has a
# password or an SSH authorized key. Privileged accounts are
# root and users in the wheel group.
assertion = !cfg.mutableUsers ->
any id (mapAttrsToList (name: cfg:
(name == "root"
|| cfg.group == "wheel"
|| elem "wheel" cfg.extraGroups)
&&
((cfg.hashedPassword != null && cfg.hashedPassword != "!")
|| cfg.password != null
|| cfg.passwordFile != null
|| cfg.openssh.authorizedKeys.keys != []
|| cfg.openssh.authorizedKeys.keyFiles != [])
) cfg.users);
message = ''
Neither the root account nor any wheel user has a password or SSH authorized key.
You must set one to prevent being locked out of your system.'';
}
];
};
}