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users: launch entire systemd --user namespace with cap_net_admin, cap_net_raw

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this should make sandboxing wireshark *much* easier, and same with things which require net namespaces, in the future
This commit is contained in:
Colin 2024-01-25 15:05:35 +00:00
parent 7f002b8718
commit 563a75e9b2
2 changed files with 67 additions and 1 deletions
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59
hosts/common/users/colin.nix
View File

@ -53,6 +53,64 @@
security.pam.mount.enable = true;
# in the future, may add this to sshd/login/sudo
# security.pam.services.systemd-user.rules = {
# auth.pam_cap = {
# order = 11500;
# # order = 12500; # before pam_unix but after all the others
# control = "required"; # ?
# modulePath = "${pkgs.libcap.pam}/lib/security/pam_cap.so";
# };
# };
# security.pam.services.greetd.rules = {
# auth.pam_cap = {
# order = 12500; # before pam_unix but after all the others
# control = "required"; # ?
# modulePath = "${pkgs.libcap.pam}/lib/security/pam_cap.so";
# };
# };
# environment.etc."/security/capability.conf".text = ''
# # The pam_cap.so module accepts the following arguments:
# #
# # debug - be more verbose logging things (unused by pam_cap for now)
# # config=<file> - override the default config for the module with file
# # keepcaps - workaround for applications that setuid without this
# # autoauth - if you want pam_cap.so to always succeed for the auth phase
# # default=<iab> - provide a fallback IAB value if there is no '*' rule
# #
# # format:
# # <CAP>[,<CAP>...] USER|@GROUP|*
# #
# # the part of each line before the delimiter (" \t\n") is parsed with `cap_iab_from_text`.
# # so each CAP can be prefixed to indicate which set it applies to:
# # [!][^][%]<CAP>
# # where ! adds to the NB set
# # ^ for AI
# # % (or empty) for I
# ^cap_net_admin,^cap_new_raw colin
# # include this `none *` line otherwise non-matching users get maximum inheritable capabilities
# none *
# '';
# grant myself extra capabilities so that i can e.g.:
# - run wireshark without root/setuid
# - (incidentally) create new network devices/routes without root/setuid, which ought to be useful for sandboxing if i deploy that right.
# default systemd includes cap_wake_alarm unless we specify our own capabilityAmbientSet; might be helpful for things like rtcwake?
#
# userName and uid have to be explicitly set here, to pass systemd's sanity checks.
# other values like `home`, `shell` can be omitted and systemd will grab those from other sources (/etc/passwd)
environment.etc."userdb/colin.user".text = ''
{
"userName" : "colin",
"uid": ${builtins.toString config.users.users.colin.uid},
"capabilityAmbientSet": [
"cap_net_admin",
"cap_net_raw"
]
}
'';
sane.users.colin = {
default = true;
@ -72,6 +130,7 @@
# these are persisted simply to save on RAM.
# ~/.cache/nix can become several GB.
# fontconfig and mesa_shader_cache are < 10 MB.
# TODO: integrate with sane.programs.sandbox?
".cache/fontconfig"
".cache/mesa_shader_cache"
".cache/nix"

9
hosts/modules/gui/sway/default.nix
View File

@ -222,7 +222,14 @@ in
sway.gtkgreet = {
enable = true;
session.name = "sway-on-gtkgreet";
session.command = "${cfg.package}/bin/sway";
# session.command = "${cfg.package}/bin/sway"; #< works, simplest way to run sway
# instead, want to run sway as a systemd user service.
# this seems silly, but it allows the launched sway to access any linux capabilities which the systemd --user manager is granted.
# notably, that means CAP_NET_ADMIN, CAP_NET_RAW; necessary for wireshark.
# these capabilities are granted to systemd --user by pam. see the user definition in hosts/common/users/colin.nix for more.
# session.command = "${pkgs.systemd}/bin/systemd-run --user --wait --collect --service-type=exec ${cfg.package}/bin/sway"; #< works, but can't launch terminals, etc ("exec: no such file" (sh))
session.command = ''${pkgs.systemd}/bin/systemd-run --user --wait --collect --service-type=exec -E "PATH=$PATH" -p AmbientCapabilities="cap_net_admin cap_net_raw" ${cfg.package}/bin/sway'';
};
};