Merge pull request #131118 from etu/sanoid-syncoid-improvements

nixos/{syncoid,sanoid}: Improve ZFS permission delegation

5 files changed, 353 insertions, 291 deletions

diff --git a/nixos/doc/manual/from_md/release-notes/rl-2111.section.xml b/nixos/doc/manual/from_md/release-notes/rl-2111.section.xml
index f573f7313652a..9dd98a5262f80 100644
--- a/nixos/doc/manual/from_md/release-notes/rl-2111.section.xml
+++ b/nixos/doc/manual/from_md/release-notes/rl-2111.section.xml
@@ -702,6 +702,19 @@
           option.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          The
+          <link xlink:href="options.html#opt-services.syncoid.enable">services.syncoid.enable</link>
+          module now properly drops ZFS permissions after usage. Before
+          it delegated permissions to whole pools instead of datasets
+          and didn’t clean up after execution. You can manually look
+          this up for your pools by running
+          <literal>zfs allow your-pool-name</literal> and use
+          <literal>zfs unallow syncoid your-pool-name</literal> to clean
+          this up.
+        </para>
+      </listitem>
     </itemizedlist>
   </section>
 </section>
diff --git a/nixos/doc/manual/release-notes/rl-2111.section.md b/nixos/doc/manual/release-notes/rl-2111.section.md
index 5e379ad6fd1f1..12e1a93843314 100644
--- a/nixos/doc/manual/release-notes/rl-2111.section.md
+++ b/nixos/doc/manual/release-notes/rl-2111.section.md
@@ -183,3 +183,5 @@ pt-services.clipcat.enable).
   - NSS modules which should come after `dns` should use mkAfter.
 
 - The [networking.wireless.iwd](options.html#opt-networking.wireless.iwd.enable) module has a new [networking.wireless.iwd.settings](options.html#opt-networking.wireless.iwd.settings) option.
+
+- The [services.syncoid.enable](options.html#opt-services.syncoid.enable) module now properly drops ZFS permissions after usage. Before it delegated permissions to whole pools instead of datasets and didn't clean up after execution. You can manually look this up for your pools by running `zfs allow your-pool-name` and use `zfs unallow syncoid your-pool-name` to clean this up.
diff --git a/nixos/modules/services/backup/sanoid.nix b/nixos/modules/services/backup/sanoid.nix
index abc4def1c61f5..41d0e2e1df686 100644
--- a/nixos/modules/services/backup/sanoid.nix
+++ b/nixos/modules/services/backup/sanoid.nix
@@ -52,7 +52,7 @@ let
     use_template = mkOption {
       description = "Names of the templates to use for this dataset.";
       type = types.listOf (types.enum (attrNames cfg.templates));
-      default = [];
+      default = [ ];
     };
     useTemplate = use_template;
 
@@ -70,116 +70,127 @@ let
     processChildrenOnly = process_children_only;
   };
 
-  # Extract pool names from configured datasets
-  pools = unique (map (d: head (builtins.match "([^/]+).*" d)) (attrNames cfg.datasets));
-
-  configFile = let
-    mkValueString = v:
-      if builtins.isList v then concatStringsSep "," v
-      else generators.mkValueStringDefault {} v;
-
-    mkKeyValue = k: v: if v == null then ""
-      else if k == "processChildrenOnly" then ""
-      else if k == "useTemplate" then ""
-      else generators.mkKeyValueDefault { inherit mkValueString; } "=" k v;
-  in generators.toINI { inherit mkKeyValue; } cfg.settings;
-
-in {
-
-    # Interface
-
-    options.services.sanoid = {
-      enable = mkEnableOption "Sanoid ZFS snapshotting service";
-
-      interval = mkOption {
-        type = types.str;
-        default = "hourly";
-        example = "daily";
-        description = ''
-          Run sanoid at this interval. The default is to run hourly.
-
-          The format is described in
-          <citerefentry><refentrytitle>systemd.time</refentrytitle>
-          <manvolnum>7</manvolnum></citerefentry>.
-        '';
-      };
+  # Extract unique dataset names
+  datasets = unique (attrNames cfg.datasets);
+
+  # Function to build "zfs allow" and "zfs unallow" commands for the
+  # filesystems we've delegated permissions to.
+  buildAllowCommand = zfsAction: permissions: dataset: lib.escapeShellArgs [
+    # Here we explicitly use the booted system to guarantee the stable API needed by ZFS
+    "-+/run/booted-system/sw/bin/zfs"
+    zfsAction
+    "sanoid"
+    (concatStringsSep "," permissions)
+    dataset
+  ];
+
+  configFile =
+    let
+      mkValueString = v:
+        if builtins.isList v then concatStringsSep "," v
+        else generators.mkValueStringDefault { } v;
+
+      mkKeyValue = k: v:
+        if v == null then ""
+        else if k == "processChildrenOnly" then ""
+        else if k == "useTemplate" then ""
+        else generators.mkKeyValueDefault { inherit mkValueString; } "=" k v;
+    in
+    generators.toINI { inherit mkKeyValue; } cfg.settings;
+
+in
+{
+
+  # Interface
+
+  options.services.sanoid = {
+    enable = mkEnableOption "Sanoid ZFS snapshotting service";
+
+    interval = mkOption {
+      type = types.str;
+      default = "hourly";
+      example = "daily";
+      description = ''
+        Run sanoid at this interval. The default is to run hourly.
+
+        The format is described in
+        <citerefentry><refentrytitle>systemd.time</refentrytitle>
+        <manvolnum>7</manvolnum></citerefentry>.
+      '';
+    };
 
-      datasets = mkOption {
-        type = types.attrsOf (types.submodule ({config, options, ...}: {
-          freeformType = datasetSettingsType;
-          options = commonOptions // datasetOptions;
-          config.use_template = mkAliasDefinitions (mkDefault options.useTemplate or {});
-          config.process_children_only = mkAliasDefinitions (mkDefault options.processChildrenOnly or {});
-        }));
-        default = {};
-        description = "Datasets to snapshot.";
-      };
+    datasets = mkOption {
+      type = types.attrsOf (types.submodule ({ config, options, ... }: {
+        freeformType = datasetSettingsType;
+        options = commonOptions // datasetOptions;
+        config.use_template = mkAliasDefinitions (mkDefault options.useTemplate or { });
+        config.process_children_only = mkAliasDefinitions (mkDefault options.processChildrenOnly or { });
+      }));
+      default = { };
+      description = "Datasets to snapshot.";
+    };
 
-      templates = mkOption {
-        type = types.attrsOf (types.submodule {
-          freeformType = datasetSettingsType;
-          options = commonOptions;
-        });
-        default = {};
-        description = "Templates for datasets.";
-      };
+    templates = mkOption {
+      type = types.attrsOf (types.submodule {
+        freeformType = datasetSettingsType;
+        options = commonOptions;
+      });
+      default = { };
+      description = "Templates for datasets.";
+    };
 
-      settings = mkOption {
-        type = types.attrsOf datasetSettingsType;
-        description = ''
-          Free-form settings written directly to the config file. See
-          <link xlink:href="https://github.com/jimsalterjrs/sanoid/blob/master/sanoid.defaults.conf"/>
-          for allowed values.
-        '';
-      };
+    settings = mkOption {
+      type = types.attrsOf datasetSettingsType;
+      description = ''
+        Free-form settings written directly to the config file. See
+        <link xlink:href="https://github.com/jimsalterjrs/sanoid/blob/master/sanoid.defaults.conf"/>
+        for allowed values.
+      '';
+    };
 
-      extraArgs = mkOption {
-        type = types.listOf types.str;
-        default = [];
-        example = [ "--verbose" "--readonly" "--debug" ];
-        description = ''
-          Extra arguments to pass to sanoid. See
-          <link xlink:href="https://github.com/jimsalterjrs/sanoid/#sanoid-command-line-options"/>
-          for allowed options.
-        '';
-      };
+    extraArgs = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = [ "--verbose" "--readonly" "--debug" ];
+      description = ''
+        Extra arguments to pass to sanoid. See
+        <link xlink:href="https://github.com/jimsalterjrs/sanoid/#sanoid-command-line-options"/>
+        for allowed options.
+      '';
     };
+  };
 
-    # Implementation
-
-    config = mkIf cfg.enable {
-      services.sanoid.settings = mkMerge [
-        (mapAttrs' (d: v: nameValuePair ("template_" + d) v) cfg.templates)
-        (mapAttrs (d: v: v) cfg.datasets)
-      ];
-
-      systemd.services.sanoid = {
-        description = "Sanoid snapshot service";
-        serviceConfig = {
-          ExecStartPre = map (pool: lib.escapeShellArgs [
-            "+/run/booted-system/sw/bin/zfs" "allow"
-            "sanoid" "snapshot,mount,destroy" pool
-          ]) pools;
-          ExecStart = lib.escapeShellArgs ([
-            "${pkgs.sanoid}/bin/sanoid"
-            "--cron"
-            "--configdir" (pkgs.writeTextDir "sanoid.conf" configFile)
-          ] ++ cfg.extraArgs);
-          ExecStopPost = map (pool: lib.escapeShellArgs [
-            "+/run/booted-system/sw/bin/zfs" "unallow" "sanoid" pool
-          ]) pools;
-          User = "sanoid";
-          Group = "sanoid";
-          DynamicUser = true;
-          RuntimeDirectory = "sanoid";
-          CacheDirectory = "sanoid";
-        };
-        # Prevents missing snapshots during DST changes
-        environment.TZ = "UTC";
-        after = [ "zfs.target" ];
-        startAt = cfg.interval;
+  # Implementation
+
+  config = mkIf cfg.enable {
+    services.sanoid.settings = mkMerge [
+      (mapAttrs' (d: v: nameValuePair ("template_" + d) v) cfg.templates)
+      (mapAttrs (d: v: v) cfg.datasets)
+    ];
+
+    systemd.services.sanoid = {
+      description = "Sanoid snapshot service";
+      serviceConfig = {
+        ExecStartPre = (map (buildAllowCommand "allow" [ "snapshot" "mount" "destroy" ]) datasets);
+        ExecStopPost = (map (buildAllowCommand "unallow" [ "snapshot" "mount" "destroy" ]) datasets);
+        ExecStart = lib.escapeShellArgs ([
+          "${pkgs.sanoid}/bin/sanoid"
+          "--cron"
+          "--configdir"
+          (pkgs.writeTextDir "sanoid.conf" configFile)
+        ] ++ cfg.extraArgs);
+        User = "sanoid";
+        Group = "sanoid";
+        DynamicUser = true;
+        RuntimeDirectory = "sanoid";
+        CacheDirectory = "sanoid";
       };
+      # Prevents missing snapshots during DST changes
+      environment.TZ = "UTC";
+      after = [ "zfs.target" ];
+      startAt = cfg.interval;
     };
+  };
 
-    meta.maintainers = with maintainers; [ lopsided98 ];
-  }
+  meta.maintainers = with maintainers; [ lopsided98 ];
+}
diff --git a/nixos/modules/services/backup/syncoid.nix b/nixos/modules/services/backup/syncoid.nix
index 888ef20f642e5..73b01d4b53faa 100644
--- a/nixos/modules/services/backup/syncoid.nix
+++ b/nixos/modules/services/backup/syncoid.nix
@@ -5,226 +5,243 @@ with lib;
 let
   cfg = config.services.syncoid;
 
-  # 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);
+  # Extract local dasaset names (so no datasets containing "@")
+  localDatasetName = 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 {
+      (builtins.split "[^a-zA-Z0-9_.\\-]+" name);
 
-    # Interface
+  # Function to build "zfs allow" and "zfs unallow" commands for the
+  # filesystems we've delegated permissions to.
+  buildAllowCommand = zfsAction: permissions: dataset: lib.escapeShellArgs [
+    # Here we explicitly use the booted system to guarantee the stable API needed by ZFS
+    "-+/run/booted-system/sw/bin/zfs"
+    zfsAction
+    cfg.user
+    (concatStringsSep "," permissions)
+    dataset
+  ];
+in
+{
 
-    options.services.syncoid = {
-      enable = mkEnableOption "Syncoid ZFS synchronization service";
+  # Interface
 
-      interval = mkOption {
-        type = types.str;
-        default = "hourly";
-        example = "*-*-* *:15:00";
-        description = ''
-          Run syncoid at this interval. The default is to run hourly.
+  options.services.syncoid = {
+    enable = mkEnableOption "Syncoid ZFS synchronization service";
 
-          The format is described in
-          <citerefentry><refentrytitle>systemd.time</refentrytitle>
-          <manvolnum>7</manvolnum></citerefentry>.
-        '';
-      };
+    interval = mkOption {
+      type = types.str;
+      default = "hourly";
+      example = "*-*-* *:15:00";
+      description = ''
+        Run syncoid at this interval. The default is to run hourly.
 
-      user = mkOption {
-        type = types.str;
-        default = "syncoid";
-        example = "backup";
-        description = ''
-          The user for the service. ZFS privilege delegation will be
-          automatically configured for any local pools used by syncoid if this
-          option is set to a user other than root. The user will be given the
-          "hold" and "send" privileges on any pool that has datasets being sent
-          and the "create", "mount", "receive", and "rollback" privileges on
-          any pool that has datasets being received.
-        '';
-      };
+        The format is described in
+        <citerefentry><refentrytitle>systemd.time</refentrytitle>
+        <manvolnum>7</manvolnum></citerefentry>.
+      '';
+    };
 
-      group = mkOption {
-        type = types.str;
-        default = "syncoid";
-        example = "backup";
-        description = "The group for the service.";
-      };
+    user = mkOption {
+      type = types.str;
+      default = "syncoid";
+      example = "backup";
+      description = ''
+        The user for the service. ZFS privilege delegation will be
+        automatically configured for any local pools used by syncoid if this
+        option is set to a user other than root. The user will be given the
+        "hold" and "send" privileges on any pool that has datasets being sent
+        and the "create", "mount", "receive", and "rollback" privileges on
+        any pool that has datasets being received.
+      '';
+    };
 
-      sshKey = mkOption {
-        type = types.nullOr types.path;
-        # Prevent key from being copied to store
-        apply = mapNullable toString;
-        default = null;
-        description = ''
-          SSH private key file to use to login to the remote system. Can be
-          overridden in individual commands.
-        '';
-      };
+    group = mkOption {
+      type = types.str;
+      default = "syncoid";
+      example = "backup";
+      description = "The group for the service.";
+    };
 
-      commonArgs = mkOption {
-        type = types.listOf types.str;
-        default = [];
-        example = [ "--no-sync-snap" ];
-        description = ''
-          Arguments to add to every syncoid command, unless disabled for that
-          command. See
-          <link xlink:href="https://github.com/jimsalterjrs/sanoid/#syncoid-command-line-options"/>
-          for available options.
-        '';
-      };
+    sshKey = mkOption {
+      type = types.nullOr types.path;
+      # Prevent key from being copied to store
+      apply = mapNullable toString;
+      default = null;
+      description = ''
+        SSH private key file to use to login to the remote system. Can be
+        overridden in individual commands.
+      '';
+    };
 
-      service = mkOption {
-        type = types.attrs;
-        default = {};
-        description = ''
-          Systemd configuration common to all syncoid services.
-        '';
-      };
+    commonArgs = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = [ "--no-sync-snap" ];
+      description = ''
+        Arguments to add to every syncoid command, unless disabled for that
+        command. See
+        <link xlink:href="https://github.com/jimsalterjrs/sanoid/#syncoid-command-line-options"/>
+        for available options.
+      '';
+    };
 
-      commands = mkOption {
-        type = types.attrsOf (types.submodule ({ name, ... }: {
-          options = {
-            source = mkOption {
-              type = types.str;
-              example = "pool/dataset";
-              description = ''
-                Source ZFS dataset. Can be either local or remote. Defaults to
-                the attribute name.
-              '';
-            };
+    service = mkOption {
+      type = types.attrs;
+      default = { };
+      description = ''
+        Systemd configuration common to all syncoid services.
+      '';
+    };
 
-            target = mkOption {
-              type = types.str;
-              example = "user@server:pool/dataset";
-              description = ''
-                Target ZFS dataset. Can be either local
-                (<replaceable>pool/dataset</replaceable>) or remote
-                (<replaceable>user@server:pool/dataset</replaceable>).
-              '';
-            };
+    commands = mkOption {
+      type = types.attrsOf (types.submodule ({ name, ... }: {
+        options = {
+          source = mkOption {
+            type = types.str;
+            example = "pool/dataset";
+            description = ''
+              Source ZFS dataset. Can be either local or remote. Defaults to
+              the attribute name.
+            '';
+          };
 
-            recursive = mkEnableOption ''the transfer of child datasets'';
+          target = mkOption {
+            type = types.str;
+            example = "user@server:pool/dataset";
+            description = ''
+              Target ZFS dataset. Can be either local
+              (<replaceable>pool/dataset</replaceable>) or remote
+              (<replaceable>user@server:pool/dataset</replaceable>).
+            '';
+          };
 
-            sshKey = mkOption {
-              type = types.nullOr types.path;
-              # Prevent key from being copied to store
-              apply = mapNullable toString;
-              description = ''
-                SSH private key file to use to login to the remote system.
-                Defaults to <option>services.syncoid.sshKey</option> option.
-              '';
-            };
+          recursive = mkEnableOption ''the transfer of child datasets'';
 
-            sendOptions = mkOption {
-              type = types.separatedString " ";
-              default = "";
-              example = "Lc e";
-              description = ''
-                Advanced options to pass to zfs send. Options are specified
-                without their leading dashes and separated by spaces.
-              '';
-            };
+          sshKey = mkOption {
+            type = types.nullOr types.path;
+            # Prevent key from being copied to store
+            apply = mapNullable toString;
+            description = ''
+              SSH private key file to use to login to the remote system.
+              Defaults to <option>services.syncoid.sshKey</option> option.
+            '';
+          };
 
-            recvOptions = mkOption {
-              type = types.separatedString " ";
-              default = "";
-              example = "ux recordsize o compression=lz4";
-              description = ''
-                Advanced options to pass to zfs recv. Options are specified
-                without their leading dashes and separated by spaces.
-              '';
-            };
+          sendOptions = mkOption {
+            type = types.separatedString " ";
+            default = "";
+            example = "Lc e";
+            description = ''
+              Advanced options to pass to zfs send. Options are specified
+              without their leading dashes and separated by spaces.
+            '';
+          };
 
-            useCommonArgs = mkOption {
-              type = types.bool;
-              default = true;
-              description = ''
-                Whether to add the configured common arguments to this command.
-              '';
-            };
+          recvOptions = mkOption {
+            type = types.separatedString " ";
+            default = "";
+            example = "ux recordsize o compression=lz4";
+            description = ''
+              Advanced options to pass to zfs recv. Options are specified
+              without their leading dashes and separated by spaces.
+            '';
+          };
 
-            service = mkOption {
-              type = types.attrs;
-              default = {};
-              description = ''
-                Systemd configuration specific to this syncoid service.
-              '';
-            };
+          useCommonArgs = mkOption {
+            type = types.bool;
+            default = true;
+            description = ''
+              Whether to add the configured common arguments to this command.
+            '';
+          };
 
-            extraArgs = mkOption {
-              type = types.listOf types.str;
-              default = [];
-              example = [ "--sshport 2222" ];
-              description = "Extra syncoid arguments for this command.";
-            };
+          service = mkOption {
+            type = types.attrs;
+            default = { };
+            description = ''
+              Systemd configuration specific to this syncoid service.
+            '';
           };
-          config = {
-            source = mkDefault name;
-            sshKey = mkDefault cfg.sshKey;
+
+          extraArgs = mkOption {
+            type = types.listOf types.str;
+            default = [ ];
+            example = [ "--sshport 2222" ];
+            description = "Extra syncoid arguments for this command.";
           };
-        }));
-        default = {};
-        example = literalExample ''
-          {
-            "pool/test".target = "root@target:pool/test";
-          }
-        '';
-        description = "Syncoid commands to run.";
-      };
+        };
+        config = {
+          source = mkDefault name;
+          sshKey = mkDefault cfg.sshKey;
+        };
+      }));
+      default = { };
+      example = literalExample ''
+        {
+          "pool/test".target = "root@target:pool/test";
+        }
+      '';
+      description = "Syncoid commands to run.";
     };
+  };
 
-    # Implementation
+  # Implementation
 
-    config = mkIf cfg.enable {
-      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") {
-          syncoid = {};
+  config = mkIf cfg.enable {
+    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") {
+        syncoid = { };
+      };
+    };
 
-      systemd.services = mapAttrs' (name: c:
+    systemd.services = mapAttrs'
+      (name: c:
         nameValuePair "syncoid-${escapeUnitName name}" (mkMerge [
-          { description = "Syncoid ZFS synchronization from ${c.source} to ${c.target}";
+          {
+            description = "Syncoid ZFS synchronization from ${c.source} to ${c.target}";
             after = [ "zfs.target" ];
             startAt = cfg.interval;
             # syncoid may need zpool to get feature@extensible_dataset
             path = [ "/run/booted-system/sw/bin/" ];
             serviceConfig = {
               ExecStartPre =
-                map (pool: lib.escapeShellArgs [
-                  "+/run/booted-system/sw/bin/zfs" "allow"
-                  cfg.user "bookmark,hold,send,snapshot,destroy" pool
-                  # Permissions snapshot and destroy are in case --no-sync-snap is not used
-                ]) (localPoolName c.source) ++
-                map (pool: lib.escapeShellArgs [
-                  "+/run/booted-system/sw/bin/zfs" "allow"
-                  cfg.user "create,mount,receive,rollback" pool
-                ]) (localPoolName c.target);
+                # Permissions snapshot and destroy are in case --no-sync-snap is not used
+                (map (buildAllowCommand "allow" [ "bookmark" "hold" "send" "snapshot" "destroy" ]) (localDatasetName c.source)) ++
+                (map (buildAllowCommand "allow" [ "create" "mount" "receive" "rollback" ]) (localDatasetName c.target));
+              ExecStopPost =
+                # Permissions snapshot and destroy are in case --no-sync-snap is not used
+                (map (buildAllowCommand "unallow" [ "bookmark" "hold" "send" "snapshot" "destroy" ]) (localDatasetName c.source)) ++
+                (map (buildAllowCommand "unallow" [ "create" "mount" "receive" "rollback" ]) (localDatasetName c.target));
               ExecStart = lib.escapeShellArgs ([ "${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
-                   ]);
+                ++ [
+                "--sendoptions"
+                c.sendOptions
+                "--recvoptions"
+                c.recvOptions
+                "--no-privilege-elevation"
+                c.source
+                c.target
+              ]);
               User = cfg.user;
               Group = cfg.group;
               StateDirectory = [ "syncoid" ];
@@ -240,7 +257,7 @@ in {
               # systemd-analyze security | grep syncoid-'*'
               AmbientCapabilities = "";
               CapabilityBoundingSet = "";
-              DeviceAllow = ["/dev/zfs"];
+              DeviceAllow = [ "/dev/zfs" ];
               LockPersonality = true;
               MemoryDenyWriteExecute = true;
               NoNewPrivileges = true;
@@ -266,7 +283,7 @@ in {
               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/${escapeUnitName name}"];
+              InaccessiblePaths = [ "-+/run/syncoid/${escapeUnitName name}" ];
               MountAPIVFS = true;
               # Create RootDirectory= in the host's mount namespace.
               RuntimeDirectory = [ "syncoid/${escapeUnitName name}" ];
@@ -277,8 +294,14 @@ in {
                 # 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"
+                "~@aio"
+                "~@chown"
+                "~@keyring"
+                "~@memlock"
+                "~@privileged"
+                "~@resources"
+                "~@setuid"
+                "~@timer"
               ];
               SystemCallArchitectures = "native";
               # This is for BindPaths= and BindReadOnlyPaths=
@@ -288,8 +311,9 @@ in {
           }
           cfg.service
           c.service
-        ])) cfg.commands;
-    };
+        ]))
+      cfg.commands;
+  };
 
-    meta.maintainers = with maintainers; [ julm lopsided98 ];
-  }
+  meta.maintainers = with maintainers; [ julm lopsided98 ];
+}
diff --git a/nixos/tests/sanoid.nix b/nixos/tests/sanoid.nix
index 7cef51e420100..3bdbe0a8d8dbd 100644
--- a/nixos/tests/sanoid.nix
+++ b/nixos/tests/sanoid.nix
@@ -85,10 +85,18 @@ in {
         "chown -R syncoid:syncoid /var/lib/syncoid/",
     )
 
+    assert len(source.succeed("zfs allow pool")) == 0, "Pool shouldn't have delegated permissions set before snapshotting"
+    assert len(source.succeed("zfs allow pool/sanoid")) == 0, "Sanoid dataset shouldn't have delegated permissions set before snapshotting"
+    assert len(source.succeed("zfs allow pool/syncoid")) == 0, "Syncoid dataset shouldn't have delegated permissions set before snapshotting"
+
     # Take snapshot with sanoid
     source.succeed("touch /mnt/pool/sanoid/test.txt")
     source.systemctl("start --wait sanoid.service")
 
+    assert len(source.succeed("zfs allow pool")) == 0, "Pool shouldn't have delegated permissions set after snapshotting"
+    assert len(source.succeed("zfs allow pool/sanoid")) == 0, "Sanoid dataset shouldn't have delegated permissions set after snapshotting"
+    assert len(source.succeed("zfs allow pool/syncoid")) == 0, "Syncoid dataset shouldn't have delegated permissions set after snapshotting"
+
     # Sync snapshots
     target.wait_for_open_port(22)
     source.succeed("touch /mnt/pool/syncoid/test.txt")
@@ -96,5 +104,9 @@ in {
     target.succeed("cat /mnt/pool/sanoid/test.txt")
     source.systemctl("start --wait syncoid-pool-syncoid.service")
     target.succeed("cat /mnt/pool/syncoid/test.txt")
+
+    assert len(source.succeed("zfs allow pool")) == 0, "Pool shouldn't have delegated permissions set after syncing snapshots"
+    assert len(source.succeed("zfs allow pool/sanoid")) == 0, "Sanoid dataset shouldn't have delegated permissions set after syncing snapshots"
+    assert len(source.succeed("zfs allow pool/syncoid")) == 0, "Syncoid dataset shouldn't have delegated permissions set after syncing snapshots"
   '';
 })