With #36556, a check was introduced to make sure the user and group
names do not exceed their respective maximum length. This is in part
because systemd also enforces that length, but only at runtime.
So in general it's a good idea to catch as much as we can during
evaluation time, however the maximum length of the group name was set to
16 characters according groupadd(8).
The maximum length of the group names however is a compile-time option
and even systemd allows more than 16 characters. In the mentioned pull
request (#36556) there was already a report that this has broken
evaluation for people out there.
I have also checked what other distributions are doing and they set the
length to either 31 characters or 32 characters, the latter being more
common.
Unfortunately there is a difference between the maximum length enforced
by the shadow package and systemd, both for user name lengths and group
name lengths. However, systemd enforces both length to have a maximum of
31 characters and I'm not sure if this is intended or just a off-by-one
error in systemd.
Nevertheless, I choose 32 characters simply to bring it in par with the
maximum user name length.
For the NixOS assertion however, I use a maximum length of 31 to make
sure that nobody accidentally creates services that contain group names
that systemd considers invalid because of a length of 32 characters.
Signed-off-by: aszlig <aszlig@nix.build>
Closes: #38548
Cc: @vcunat, @fpletz, @qknight
This GID was used to exempt users from Grsecurity's
`/proc` restrictions; we now prefer to rely on
`security.hideProcessInformation`, which uses the `proc` group
for this purpose. That leaves no use for the grsecurity GID.
More generally, having only a single GID to, presumably, serve as the
default for all of grsecurity's GID based exemption/resriction schemes
would be problematic in any event, so if we decide to enable those
grsecurity features in the future, more specific GIDs should be added.
Option aliases/deprecations can now be declared in any NixOS module,
not just in nixos/modules/rename.nix. This is more modular (since it
allows for example grub-related aliases to be declared in the grub
module), and allows aliases outside of NixOS (e.g. in NixOps modules).
The syntax is a bit funky. Ideally we'd have something like:
options = {
foo.bar.newOption = mkOption { ... };
foo.bar.oldOption = mkAliasOption [ "foo" "bar" "newOption" ];
};
but that's not possible because options cannot define values in
*other* options - you need to have a "config" for that. So instead we
have functions that return a *module*: mkRemovedOptionModule,
mkRenamedOptionModule and mkAliasOptionModule. These can be used via
"imports", e.g.
imports = [
(mkAliasOptionModule [ "foo" "bar" "oldOption" ] [ "foo" "bar" "newOption" ]);
];
As an added bonus, deprecation warnings now show the file name of the
offending module.
Fixes#10385.
In this case, they're equivalent to setting ‘password’ and
‘hashedPassword’ (since there is no distinction between an initial and
non-initial user account state).
This hopefully fixes a regression introduced by 08b214a.
In bf129a2, it was already fixed for normal uid/gid values and it got
reintroduced by sub-uid/gid-handling again, so I've refactored it a bit
into a filterNull function which takes care of also the filtering
introduced by bf129a2.
I have not tested this extensively, but master is already broken for
systems with `mutableUsers = true` and no uid values set.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
With mutableUsers = true, we now ensure that all users and groups that
were created declaratively, are updated or removed
appropriately. Thus, adding a user to users.extraUsers and then
removing it now causes the acoount to be removed from
/etc/passwd. Thus user/group management is fully congruent except that
users and groups that were created imperatively (via useradd/groupadd)
are not touched. We distinguish between declarative and imperative
users/groups by tracking the former in
/var/lib/nixos/declarative-{groups,users}.
With mutableUsers = false, you are now no longer required to specify
UIDs/GIDs for all users. The handling of mutableUsers = true/false is
the same code path; the only difference is that the "false" mode
ignores the existing contents of /etc/{passwd,group}.
The attribute ‘createUser’ is gone. It doesn't really make sense to
specify users that shouldn't be created.
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
This module implements a significant refactoring in grsecurity
configuration for NixOS, making it far more usable by default and much
easier to configure.
- New security.grsecurity NixOS attributes.
- All grsec kernels supported
- Allows default 'auto' grsec configuration, or custom config
- Supports custom kernel options through kernelExtraConfig
- Defaults to high-security - user must choose kernel, server/desktop
mode, and any virtualisation software. That's all.
- kptr_restrict is fixed under grsecurity (it's unwriteable)
- grsecurity patch creation is now significantly abstracted
- only need revision, version, and SHA1
- kernel version requirements are asserted for sanity
- built kernels can have the uname specify the exact grsec version
for development or bug reports. Off by default (requires
`security.grsecurity.config.verboseVersion = true;`)
- grsecurity sysctl support
- By default, disabled.
- For people who enable it, NixOS deploys a 'grsec-lock' systemd
service which runs at startup. You are expected to configure sysctl
through NixOS like you regularly would, which will occur before the
service is started. As a result, changing sysctl settings requires
a reboot.
- New default group: 'grsecurity'
- Root is a member by default
- GRKERNSEC_PROC_GID is implicitly set to the 'grsecurity' GID,
making it possible to easily add users to this group for /proc
access
- AppArmor is now automatically enabled where it wasn't before, despite
implying features.apparmor = true
The most trivial example of enabling grsecurity in your kernel is by
specifying:
security.grsecurity.enable = true;
security.grsecurity.testing = true; # testing 3.13 kernel
security.grsecurity.config.system = "desktop"; # or "server"
This specifies absolutely no virtualisation support. In general, you
probably at least want KVM host support, which is a little more work.
So:
security.grsecurity.enable = true;
security.grsecurity.stable = true; # enable stable 3.2 kernel
security.grsecurity.config = {
system = "server";
priority = "security";
virtualisationConfig = "host";
virtualisationSoftware = "kvm";
hardwareVirtualisation = true;
}
This module has primarily been tested on Hetzner EX40 & VQ7 servers
using NixOps.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
The mutableUsers feature uses `chpasswd` to set users passwords.
Passwords and their hashes were being piped into the program using
double quotes ("") to escape. This causes any `$` characters to be
expanded as shell variables. This is a serious problem because all the
password hash methods besides DES use multiple `$` in the hashes. Single
quotes ('') should be used instead to prevent shell variable expansion.
This is a rather large commit that switches user/group creation from using
useradd/groupadd on activation to just generating the contents of /etc/passwd
and /etc/group, and then on activation merging the generated files with the
files that exist in the system. This makes the user activation process much
cleaner, in my opinion.
The users.extraUsers.<user>.uid and users.extraGroups.<group>.gid must all be
properly defined (if <user>.createUser is true, which it is by default). My
pull request adds a lot of uids/gids to config.ids to solve this problem for
existing nixos services, but there might be configurations that break because
this change. However, this will be discovered during the build.
Option changes introduced by this commit:
* Remove the options <user>.isSystemUser and <user>.isAlias since
they don't make sense when generating /etc/passwd statically.
* Add <group>.members as a complement to <user>.extraGroups.
* Add <user>.passwordFile for setting a user's password from an encrypted
(shadow-style) file.
* Add users.mutableUsers which is true by default. This means you can keep
managing your users as previously, by using useradd/groupadd manually. This is
accomplished by merging the generated passwd/group file with the existing files
in /etc on system activation. The merging of the files is simplistic. It just
looks at the user/group names. If a user/group exists both on the system and
in the generated files, the system entry will be kept un-changed and the
generated entries will be ignored. The merging itself is performed with the
help of vipw/vigr to properly lock the account files during edit.
If mutableUsers is set to false, the generated passwd and group files will not
be merged with the system files on activation. Instead they will simply replace
the system files, and overwrite any changes done on the running system. The
same logic holds for user password, if the <user>.password or
<user>.passwordFile options are used. If mutableUsers is false, password will
simply be replaced on activation. If true, the initial user passwords will be
set according to the configuration, but existing passwords will not be touched.
I have tested this on a couple of different systems and it seems to work fine
so far. If you think this is a good idea, please test it. This way of adding
local users has been discussed in issue #103 (and this commit solves that
issue).
A null password allows logging into local PAM services such as "login"
(agetty) and KDM. That's not actually a security problem for EC2
machines, since they do not have "local" logins; for VirtualBox
machines, if you local access, you can do anything anyway. But it's
better to be on the safe side and disable password-based logins for
root.
