Merge pull request #98455 from ju1m/syncoid-split

nixos/syncoid: split in multiple systemd services and harden them
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Elis Hirwing 2021-07-24 22:08:42 +02:00 committed by GitHub
commit 6984e68c51
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2 changed files with 127 additions and 47 deletions

View file

@ -5,14 +5,15 @@ with lib;
let
cfg = config.services.syncoid;
# Extract pool names of local datasets (ones that don't contain "@") that
# have the specified type (either "source" or "target")
getPools = type: unique (map (d: head (builtins.match "([^/]+).*" d)) (
# Filter local datasets
filter (d: !hasInfix "@" d)
# Get datasets of the specified type
(catAttrs type (attrValues cfg.commands))
));
# Extract the pool name of a local dataset (any dataset not containing "@")
localPoolName = d: optionals (d != null) (
let m = builtins.match "([^/@]+)[^@]*" d; in
optionals (m != null) m);
# Escape as required by: https://www.freedesktop.org/software/systemd/man/systemd.unit.html
escapeUnitName = name:
lib.concatMapStrings (s: if lib.isList s then "-" else s)
(builtins.split "[^a-zA-Z0-9_.\\-]+" name);
in {
# Interface
@ -77,6 +78,14 @@ in {
'';
};
service = mkOption {
type = types.attrs;
default = {};
description = ''
Systemd configuration common to all syncoid services.
'';
};
commands = mkOption {
type = types.attrsOf (types.submodule ({ name, ... }: {
options = {
@ -99,13 +108,7 @@ in {
'';
};
recursive = mkOption {
type = types.bool;
default = false;
description = ''
Whether to also transfer child datasets.
'';
};
recursive = mkEnableOption ''the transfer of child datasets'';
sshKey = mkOption {
type = types.nullOr types.path;
@ -145,6 +148,14 @@ in {
'';
};
service = mkOption {
type = types.attrs;
default = {};
description = ''
Systemd configuration specific to this syncoid service.
'';
};
extraArgs = mkOption {
type = types.listOf types.str;
default = [];
@ -170,11 +181,15 @@ in {
# Implementation
config = mkIf cfg.enable {
users = {
users = {
users = mkIf (cfg.user == "syncoid") {
syncoid = {
group = cfg.group;
isSystemUser = true;
# For syncoid to be able to create /var/lib/syncoid/.ssh/
# and to use custom ssh_config or known_hosts.
home = "/var/lib/syncoid";
createHome = false;
};
};
groups = mkIf (cfg.group == "syncoid") {
@ -182,35 +197,99 @@ in {
};
};
systemd.services.syncoid = {
description = "Syncoid ZFS synchronization service";
script = concatMapStringsSep "\n" (c: lib.escapeShellArgs
([ "${pkgs.sanoid}/bin/syncoid" ]
++ (optionals c.useCommonArgs cfg.commonArgs)
++ (optional c.recursive "-r")
++ (optionals (c.sshKey != null) [ "--sshkey" c.sshKey ])
++ c.extraArgs
++ [ "--sendoptions" c.sendOptions
"--recvoptions" c.recvOptions
"--no-privilege-elevation"
c.source c.target
])) (attrValues cfg.commands);
after = [ "zfs.target" ];
serviceConfig = {
ExecStartPre = let
allowCmd = permissions: pool: lib.escapeShellArgs [
"+/run/booted-system/sw/bin/zfs" "allow"
cfg.user (concatStringsSep "," permissions) pool
];
in
(map (allowCmd [ "hold" "send" "snapshot" "destroy" ]) (getPools "source")) ++
(map (allowCmd [ "create" "mount" "receive" "rollback" ]) (getPools "target"));
User = cfg.user;
Group = cfg.group;
};
startAt = cfg.interval;
};
systemd.services = mapAttrs' (name: c:
nameValuePair "syncoid-${escapeUnitName name}" (mkMerge [
{ description = "Syncoid ZFS synchronization from ${c.source} to ${c.target}";
after = [ "zfs.target" ];
startAt = cfg.interval;
# syncoid may need zpool to get feature@extensible_dataset
path = [ "/run/booted-system/sw/bin/" ];
serviceConfig = {
ExecStartPre =
map (pool: lib.escapeShellArgs [
"+/run/booted-system/sw/bin/zfs" "allow"
cfg.user "bookmark,hold,send,snapshot,destroy" pool
# Permissions snapshot and destroy are in case --no-sync-snap is not used
]) (localPoolName c.source) ++
map (pool: lib.escapeShellArgs [
"+/run/booted-system/sw/bin/zfs" "allow"
cfg.user "create,mount,receive,rollback" pool
]) (localPoolName c.target);
ExecStart = lib.escapeShellArgs ([ "${pkgs.sanoid}/bin/syncoid" ]
++ optionals c.useCommonArgs cfg.commonArgs
++ optional c.recursive "-r"
++ optionals (c.sshKey != null) [ "--sshkey" c.sshKey ]
++ c.extraArgs
++ [ "--sendoptions" c.sendOptions
"--recvoptions" c.recvOptions
"--no-privilege-elevation"
c.source c.target
]);
User = cfg.user;
Group = cfg.group;
StateDirectory = [ "syncoid" ];
StateDirectoryMode = "700";
# Prevent SSH control sockets of different syncoid services from interfering
PrivateTmp = true;
# Permissive access to /proc because syncoid
# calls ps(1) to detect ongoing `zfs receive`.
ProcSubset = "all";
ProtectProc = "default";
# The following options are only for optimizing:
# systemd-analyze security | grep syncoid-'*'
AmbientCapabilities = "";
CapabilityBoundingSet = "";
DeviceAllow = ["/dev/zfs"];
LockPersonality = true;
MemoryDenyWriteExecute = true;
NoNewPrivileges = true;
PrivateDevices = true;
PrivateMounts = true;
PrivateNetwork = mkDefault false;
PrivateUsers = true;
ProtectClock = true;
ProtectControlGroups = true;
ProtectHome = true;
ProtectHostname = true;
ProtectKernelLogs = true;
ProtectKernelModules = true;
ProtectKernelTunables = true;
ProtectSystem = "strict";
RemoveIPC = true;
RestrictAddressFamilies = [ "AF_UNIX" "AF_INET" "AF_INET6" ];
RestrictNamespaces = true;
RestrictRealtime = true;
RestrictSUIDSGID = true;
RootDirectory = "/run/syncoid/${escapeUnitName name}";
RootDirectoryStartOnly = true;
BindPaths = [ "/dev/zfs" ];
BindReadOnlyPaths = [ builtins.storeDir "/etc" "/run" "/bin/sh" ];
# Avoid useless mounting of RootDirectory= in the own RootDirectory= of ExecStart='s mount namespace.
InaccessiblePaths = ["-+/run/syncoid/${escapeUnitName name}"];
MountAPIVFS = true;
# Create RootDirectory= in the host's mount namespace.
RuntimeDirectory = [ "syncoid/${escapeUnitName name}" ];
RuntimeDirectoryMode = "700";
SystemCallFilter = [
"@system-service"
# Groups in @system-service which do not contain a syscall listed by:
# perf stat -x, 2>perf.log -e 'syscalls:sys_enter_*' syncoid …
# awk >perf.syscalls -F "," '$1 > 0 {sub("syscalls:sys_enter_","",$3); print $3}' perf.log
# systemd-analyze syscall-filter | grep -v -e '#' | sed -e ':loop; /^[^ ]/N; s/\n //; t loop' | grep $(printf ' -e \\<%s\\>' $(cat perf.syscalls)) | cut -f 1 -d ' '
"~@aio" "~@chown" "~@keyring" "~@memlock" "~@privileged"
"~@resources" "~@setuid" "~@sync" "~@timer"
];
SystemCallArchitectures = "native";
# This is for BindPaths= and BindReadOnlyPaths=
# to allow traversal of directories they create in RootDirectory=.
UMask = "0066";
};
}
cfg.service
c.service
])) cfg.commands;
};
meta.maintainers = with maintainers; [ lopsided98 ];
meta.maintainers = with maintainers; [ julm lopsided98 ];
}

View file

@ -44,7 +44,7 @@ in {
# Sync snapshot taken by sanoid
"pool/sanoid" = {
target = "root@target:pool/sanoid";
extraArgs = [ "--no-sync-snap" ];
extraArgs = [ "--no-sync-snap" "--create-bookmark" ];
};
# Take snapshot and sync
"pool/syncoid".target = "root@target:pool/syncoid";
@ -92,8 +92,9 @@ in {
# Sync snapshots
target.wait_for_open_port(22)
source.succeed("touch /mnt/pool/syncoid/test.txt")
source.systemctl("start --wait syncoid.service")
source.systemctl("start --wait syncoid-pool-sanoid.service")
target.succeed("cat /mnt/pool/sanoid/test.txt")
source.systemctl("start --wait syncoid-pool-syncoid.service")
target.succeed("cat /mnt/pool/syncoid/test.txt")
'';
})