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nixpkgs/nixos/modules/services/torrent/transmission.nix
2021-04-23 07:20:14 +02:00

398 lines
17 KiB
Nix

{ config, lib, pkgs, options, ... }:
with lib;
let
cfg = config.services.transmission;
inherit (config.environment) etc;
apparmor = config.security.apparmor;
rootDir = "/run/transmission";
homeDir = "/var/lib/transmission";
settingsDir = ".config/transmission-daemon";
downloadsDir = "Downloads";
incompleteDir = ".incomplete";
watchDir = "watchdir";
# TODO: switch to configGen.json once RFC0042 is implemented
settingsFile = pkgs.writeText "settings.json" (builtins.toJSON cfg.settings);
in
{
options = {
services.transmission = {
enable = mkEnableOption ''the headless Transmission BitTorrent daemon.
Transmission daemon can be controlled via the RPC interface using
transmission-remote, the WebUI (http://127.0.0.1:9091/ by default),
or other clients like stig or tremc.
Torrents are downloaded to ${homeDir}/${downloadsDir} by default and are
accessible to users in the "transmission" group'';
settings = mkOption rec {
# TODO: switch to types.config.json as prescribed by RFC0042 once it's implemented
type = types.attrs;
apply = recursiveUpdate default;
default =
{
download-dir = "${cfg.home}/${downloadsDir}";
incomplete-dir = "${cfg.home}/${incompleteDir}";
incomplete-dir-enabled = true;
watch-dir = "${cfg.home}/${watchDir}";
watch-dir-enabled = false;
message-level = 1;
peer-port = 51413;
peer-port-random-high = 65535;
peer-port-random-low = 49152;
peer-port-random-on-start = false;
rpc-bind-address = "127.0.0.1";
rpc-port = 9091;
script-torrent-done-enabled = false;
script-torrent-done-filename = "";
umask = 2; # 0o002 in decimal as expected by Transmission
utp-enabled = true;
};
example =
{
download-dir = "/srv/torrents/";
incomplete-dir = "/srv/torrents/.incomplete/";
incomplete-dir-enabled = true;
rpc-whitelist = "127.0.0.1,192.168.*.*";
};
description = ''
Attribute set whose fields overwrites fields in
<literal>.config/transmission-daemon/settings.json</literal>
(each time the service starts). String values must be quoted, integer and
boolean values must not.
See <link xlink:href="https://github.com/transmission/transmission/wiki/Editing-Configuration-Files">Transmission's Wiki</link>
for documentation.
'';
};
downloadDirPermissions = mkOption {
type = types.str;
default = "770";
example = "775";
description = ''
The permissions set by <literal>systemd.activationScripts.transmission-daemon</literal>
on the directories <link linkend="opt-services.transmission.settings">settings.download-dir</link>
and <link linkend="opt-services.transmission.settings">settings.incomplete-dir</link>.
Note that you may also want to change
<link linkend="opt-services.transmission.settings">settings.umask</link>.
'';
};
port = mkOption {
type = types.port;
description = ''
TCP port number to run the RPC/web interface.
If instead you want to change the peer port,
use <link linkend="opt-services.transmission.settings">settings.peer-port</link>
or <link linkend="opt-services.transmission.settings">settings.peer-port-random-on-start</link>.
'';
};
home = mkOption {
type = types.path;
default = homeDir;
description = ''
The directory where Transmission will create <literal>${settingsDir}</literal>.
as well as <literal>${downloadsDir}/</literal> unless <link linkend="opt-services.transmission.settings">settings.download-dir</link> is changed,
and <literal>${incompleteDir}/</literal> unless <link linkend="opt-services.transmission.settings">settings.incomplete-dir</link> is changed.
'';
};
user = mkOption {
type = types.str;
default = "transmission";
description = "User account under which Transmission runs.";
};
group = mkOption {
type = types.str;
default = "transmission";
description = "Group account under which Transmission runs.";
};
credentialsFile = mkOption {
type = types.path;
description = ''
Path to a JSON file to be merged with the settings.
Useful to merge a file which is better kept out of the Nix store
because it contains sensible data like <link linkend="opt-services.transmission.settings">settings.rpc-password</link>.
'';
default = "/dev/null";
example = "/var/lib/secrets/transmission/settings.json";
};
openFirewall = mkEnableOption "opening of the peer port(s) in the firewall";
performanceNetParameters = mkEnableOption ''tweaking of kernel parameters
to open many more connections at the same time.
Note that you may also want to increase
<link linkend="opt-services.transmission.settings">settings.peer-limit-global</link>.
And be aware that these settings are quite aggressive
and might not suite your regular desktop use.
For instance, SSH sessions may time out more easily'';
};
};
config = mkIf cfg.enable {
# Note that using systemd.tmpfiles would not work here
# because it would fail when creating a directory
# with a different owner than its parent directory, by saying:
# Detected unsafe path transition /home/foo → /home/foo/Downloads during canonicalization of /home/foo/Downloads
# when /home/foo is not owned by cfg.user.
# Note also that using an ExecStartPre= wouldn't work either
# because BindPaths= needs these directories before.
system.activationScripts.transmission-daemon = ''
install -d -m 700 '${cfg.home}/${settingsDir}'
chown -R '${cfg.user}:${cfg.group}' ${cfg.home}/${settingsDir}
install -d -m '${cfg.downloadDirPermissions}' -o '${cfg.user}' -g '${cfg.group}' '${cfg.settings.download-dir}'
'' + optionalString cfg.settings.incomplete-dir-enabled ''
install -d -m '${cfg.downloadDirPermissions}' -o '${cfg.user}' -g '${cfg.group}' '${cfg.settings.incomplete-dir}'
'';
assertions = [
{ assertion = builtins.match "^/.*" cfg.home != null;
message = "`services.transmission.home' must be an absolute path.";
}
{ assertion = types.path.check cfg.settings.download-dir;
message = "`services.transmission.settings.download-dir' must be an absolute path.";
}
{ assertion = types.path.check cfg.settings.incomplete-dir;
message = "`services.transmission.settings.incomplete-dir' must be an absolute path.";
}
{ assertion = types.path.check cfg.settings.watch-dir;
message = "`services.transmission.settings.watch-dir' must be an absolute path.";
}
{ assertion = cfg.settings.script-torrent-done-filename == "" || types.path.check cfg.settings.script-torrent-done-filename;
message = "`services.transmission.settings.script-torrent-done-filename' must be an absolute path.";
}
{ assertion = types.port.check cfg.settings.rpc-port;
message = "${toString cfg.settings.rpc-port} is not a valid port number for `services.transmission.settings.rpc-port`.";
}
# In case both port and settings.rpc-port are explicitely defined: they must be the same.
{ assertion = !options.services.transmission.port.isDefined || cfg.port == cfg.settings.rpc-port;
message = "`services.transmission.port' is not equal to `services.transmission.settings.rpc-port'";
}
];
services.transmission.settings =
optionalAttrs options.services.transmission.port.isDefined { rpc-port = cfg.port; };
systemd.services.transmission = {
description = "Transmission BitTorrent Service";
after = [ "network.target" ] ++ optional apparmor.enable "apparmor.service";
requires = optional apparmor.enable "apparmor.service";
wantedBy = [ "multi-user.target" ];
environment.CURL_CA_BUNDLE = etc."ssl/certs/ca-certificates.crt".source;
serviceConfig = {
# Use "+" because credentialsFile may not be accessible to User= or Group=.
ExecStartPre = [("+" + pkgs.writeShellScript "transmission-prestart" ''
set -eu${lib.optionalString (cfg.settings.message-level >= 3) "x"}
${pkgs.jq}/bin/jq --slurp add ${settingsFile} '${cfg.credentialsFile}' |
install -D -m 600 -o '${cfg.user}' -g '${cfg.group}' /dev/stdin \
'${cfg.home}/${settingsDir}/settings.json'
'')];
ExecStart="${pkgs.transmission}/bin/transmission-daemon -f -g ${cfg.home}/${settingsDir}";
ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
User = cfg.user;
Group = cfg.group;
# Create rootDir in the host's mount namespace.
RuntimeDirectory = [(baseNameOf rootDir)];
RuntimeDirectoryMode = "755";
# Avoid mounting rootDir in the own rootDir of ExecStart='s mount namespace.
InaccessiblePaths = ["-+${rootDir}"];
# This is for BindPaths= and BindReadOnlyPaths=
# to allow traversal of directories they create in RootDirectory=.
UMask = "0066";
# Using RootDirectory= makes it possible
# to use the same paths download-dir/incomplete-dir
# (which appear in user's interfaces) without requiring cfg.user
# to have access to their parent directories,
# by using BindPaths=/BindReadOnlyPaths=.
# Note that TemporaryFileSystem= could have been used instead
# but not without adding some BindPaths=/BindReadOnlyPaths=
# that would only be needed for ExecStartPre=,
# because RootDirectoryStartOnly=true would not help.
RootDirectory = rootDir;
RootDirectoryStartOnly = true;
MountAPIVFS = true;
BindPaths =
[ "${cfg.home}/${settingsDir}"
cfg.settings.download-dir
] ++
optional cfg.settings.incomplete-dir-enabled
cfg.settings.incomplete-dir
++
optional cfg.settings.watch-dir-enabled
cfg.settings.watch-dir
;
BindReadOnlyPaths = [
# No confinement done of /nix/store here like in systemd-confinement.nix,
# an AppArmor profile is provided to get a confinement based upon paths and rights.
builtins.storeDir
"/etc"
"/run"
] ++
optional (cfg.settings.script-torrent-done-enabled &&
cfg.settings.script-torrent-done-filename != "")
cfg.settings.script-torrent-done-filename;
# The following options are only for optimizing:
# systemd-analyze security transmission
AmbientCapabilities = "";
CapabilityBoundingSet = "";
# ProtectClock= adds DeviceAllow=char-rtc r
DeviceAllow = "";
LockPersonality = true;
MemoryDenyWriteExecute = true;
NoNewPrivileges = true;
PrivateDevices = true;
PrivateMounts = true;
PrivateNetwork = mkDefault false;
PrivateTmp = true;
PrivateUsers = true;
ProtectClock = true;
ProtectControlGroups = true;
# ProtectHome=true would not allow BindPaths= to work accross /home,
# and ProtectHome=tmpfs would break statfs(),
# preventing transmission-daemon to report the available free space.
# However, RootDirectory= is used, so this is not a security concern
# since there would be nothing in /home but any BindPaths= wanted by the user.
ProtectHome = "read-only";
ProtectHostname = true;
ProtectKernelLogs = true;
ProtectKernelModules = true;
ProtectKernelTunables = true;
ProtectSystem = "strict";
RemoveIPC = true;
# AF_UNIX may become usable one day:
# https://github.com/transmission/transmission/issues/441
RestrictAddressFamilies = [ "AF_UNIX" "AF_INET" "AF_INET6" ];
RestrictNamespaces = true;
RestrictRealtime = true;
RestrictSUIDSGID = true;
SystemCallFilter = [
"@system-service"
# Groups in @system-service which do not contain a syscall
# listed by perf stat -e 'syscalls:sys_enter_*' transmission-daemon -f
# in tests, and seem likely not necessary for transmission-daemon.
"~@aio" "~@chown" "~@keyring" "~@memlock" "~@resources" "~@setuid" "~@timer"
# In the @privileged group, but reached when querying infos through RPC (eg. with stig).
"quotactl"
];
SystemCallArchitectures = "native";
SystemCallErrorNumber = "EPERM";
};
};
# It's useful to have transmission in path, e.g. for remote control
environment.systemPackages = [ pkgs.transmission ];
users.users = optionalAttrs (cfg.user == "transmission") ({
transmission = {
group = cfg.group;
uid = config.ids.uids.transmission;
description = "Transmission BitTorrent user";
home = cfg.home;
};
});
users.groups = optionalAttrs (cfg.group == "transmission") ({
transmission = {
gid = config.ids.gids.transmission;
};
});
networking.firewall = mkIf cfg.openFirewall (
if cfg.settings.peer-port-random-on-start
then
{ allowedTCPPortRanges =
[ { from = cfg.settings.peer-port-random-low;
to = cfg.settings.peer-port-random-high;
}
];
allowedUDPPortRanges =
[ { from = cfg.settings.peer-port-random-low;
to = cfg.settings.peer-port-random-high;
}
];
}
else
{ allowedTCPPorts = [ cfg.settings.peer-port ];
allowedUDPPorts = [ cfg.settings.peer-port ];
}
);
boot.kernel.sysctl = mkMerge [
# Transmission uses a single UDP socket in order to implement multiple uTP sockets,
# and thus expects large kernel buffers for the UDP socket,
# https://trac.transmissionbt.com/browser/trunk/libtransmission/tr-udp.c?rev=11956.
# at least up to the values hardcoded here:
(mkIf cfg.settings.utp-enabled {
"net.core.rmem_max" = mkDefault "4194304"; # 4MB
"net.core.wmem_max" = mkDefault "1048576"; # 1MB
})
(mkIf cfg.performanceNetParameters {
# Increase the number of available source (local) TCP and UDP ports to 49151.
# Usual default is 32768 60999, ie. 28231 ports.
# Find out your current usage with: ss -s
"net.ipv4.ip_local_port_range" = "16384 65535";
# Timeout faster generic TCP states.
# Usual default is 600.
# Find out your current usage with: watch -n 1 netstat -nptuo
"net.netfilter.nf_conntrack_generic_timeout" = 60;
# Timeout faster established but inactive connections.
# Usual default is 432000.
"net.netfilter.nf_conntrack_tcp_timeout_established" = 600;
# Clear immediately TCP states after timeout.
# Usual default is 120.
"net.netfilter.nf_conntrack_tcp_timeout_time_wait" = 1;
# Increase the number of trackable connections.
# Usual default is 262144.
# Find out your current usage with: conntrack -C
"net.netfilter.nf_conntrack_max" = 1048576;
})
];
security.apparmor.policies."bin.transmission-daemon".profile = ''
include "${pkgs.transmission.apparmor}/bin.transmission-daemon"
'';
security.apparmor.includes."local/bin.transmission-daemon" = ''
r ${config.systemd.services.transmission.environment.CURL_CA_BUNDLE},
owner rw ${cfg.home}/${settingsDir}/**,
rw ${cfg.settings.download-dir}/**,
${optionalString cfg.settings.incomplete-dir-enabled ''
rw ${cfg.settings.incomplete-dir}/**,
''}
${optionalString cfg.settings.watch-dir-enabled ''
rw ${cfg.settings.watch-dir}/**,
''}
profile dirs {
rw ${cfg.settings.download-dir}/**,
${optionalString cfg.settings.incomplete-dir-enabled ''
rw ${cfg.settings.incomplete-dir}/**,
''}
${optionalString cfg.settings.watch-dir-enabled ''
rw ${cfg.settings.watch-dir}/**,
''}
}
${optionalString (cfg.settings.script-torrent-done-enabled &&
cfg.settings.script-torrent-done-filename != "") ''
# Stack transmission_directories profile on top of
# any existing profile for script-torrent-done-filename
# FIXME: to be tested as I'm not sure it works well with NoNewPrivileges=
# https://gitlab.com/apparmor/apparmor/-/wikis/AppArmorStacking#seccomp-and-no_new_privs
px ${cfg.settings.script-torrent-done-filename} -> &@{dirs},
''}
'';
};
meta.maintainers = with lib.maintainers; [ julm ];
}