Merge pull request #191974 from tu-maurice/btrbk-doas

btrbk: Use sudo or doas based on configuration

nixos/modules/services/backup/btrbk.nix

@@ -47,7 +47,12 @@ let
     then [ "${name} ${value}" ]
     else concatLists (mapAttrsToList (genSection name) value);
 
-  addDefaults = settings: { backend = "btrfs-progs-sudo"; } // settings;
+  sudo_doas =
+    if config.security.sudo.enable then "sudo"
+    else if config.security.doas.enable then "doas"
+    else throw "The btrbk nixos module needs either sudo or doas enabled in the configuration";
+
+  addDefaults = settings: { backend = "btrfs-progs-${sudo_doas}"; } // settings;
 
   mkConfigFile = name: settings: pkgs.writeTextFile {
     name = "btrbk-${name}.conf";
@@ -152,20 +157,41 @@ in
   };
   config = mkIf (sshEnabled || serviceEnabled) {
     environment.systemPackages = [ pkgs.btrbk ] ++ cfg.extraPackages;
-    security.sudo.extraRules = [
+    security.sudo = mkIf (sudo_doas == "sudo") {
-      {
+      extraRules = [
-        users = [ "btrbk" ];
+        {
-        commands = [
+            users = [ "btrbk" ];
-          { command = "${pkgs.btrfs-progs}/bin/btrfs"; options = [ "NOPASSWD" ]; }
+            commands = [
-          { command = "${pkgs.coreutils}/bin/mkdir"; options = [ "NOPASSWD" ]; }
+            { command = "${pkgs.btrfs-progs}/bin/btrfs"; options = [ "NOPASSWD" ]; }
-          { command = "${pkgs.coreutils}/bin/readlink"; options = [ "NOPASSWD" ]; }
+            { command = "${pkgs.coreutils}/bin/mkdir"; options = [ "NOPASSWD" ]; }
-          # for ssh, they are not the same than the one hard coded in ${pkgs.btrbk}
+            { command = "${pkgs.coreutils}/bin/readlink"; options = [ "NOPASSWD" ]; }
-          { command = "/run/current-system/bin/btrfs"; options = [ "NOPASSWD" ]; }
+            # for ssh, they are not the same than the one hard coded in ${pkgs.btrbk}
-          { command = "/run/current-system/sw/bin/mkdir"; options = [ "NOPASSWD" ]; }
+            { command = "/run/current-system/bin/btrfs"; options = [ "NOPASSWD" ]; }
-          { command = "/run/current-system/sw/bin/readlink"; options = [ "NOPASSWD" ]; }
+            { command = "/run/current-system/sw/bin/mkdir"; options = [ "NOPASSWD" ]; }
+            { command = "/run/current-system/sw/bin/readlink"; options = [ "NOPASSWD" ]; }
+            ];
+        }
+      ];
+    };
+    security.doas = mkIf (sudo_doas == "doas") {
+      extraRules = let
+        doasCmdNoPass = cmd: { users = [ "btrbk" ]; cmd = cmd; noPass = true; };
+      in
+        [
+            (doasCmdNoPass "${pkgs.btrfs-progs}/bin/btrfs")
+            (doasCmdNoPass "${pkgs.coreutils}/bin/mkdir")
+            (doasCmdNoPass "${pkgs.coreutils}/bin/readlink")
+            # for ssh, they are not the same than the one hard coded in ${pkgs.btrbk}
+            (doasCmdNoPass "/run/current-system/bin/btrfs")
+            (doasCmdNoPass "/run/current-system/sw/bin/mkdir")
+            (doasCmdNoPass "/run/current-system/sw/bin/readlink")
+
+            # doas matches command, not binary
+            (doasCmdNoPass "btrfs")
+            (doasCmdNoPass "mkdir")
+            (doasCmdNoPass "readlink")
         ];
-      }
+    };
-    ];
     users.users.btrbk = {
       isSystemUser = true;
       # ssh needs a home directory
@@ -183,8 +209,9 @@ in
               "best-effort" = 2;
               "realtime" = 1;
             }.${cfg.ioSchedulingClass};
+            sudo_doas_flag = "--${sudo_doas}";
           in
-          ''command="${pkgs.util-linux}/bin/ionice -t -c ${toString ioniceClass} ${optionalString (cfg.niceness >= 1) "${pkgs.coreutils}/bin/nice -n ${toString cfg.niceness}"} ${pkgs.btrbk}/share/btrbk/scripts/ssh_filter_btrbk.sh --sudo ${options}" ${v.key}''
+          ''command="${pkgs.util-linux}/bin/ionice -t -c ${toString ioniceClass} ${optionalString (cfg.niceness >= 1) "${pkgs.coreutils}/bin/nice -n ${toString cfg.niceness}"} ${pkgs.btrbk}/share/btrbk/scripts/ssh_filter_btrbk.sh ${sudo_doas_flag} ${options}" ${v.key}''
         )
         cfg.sshAccess;
     };

nixos/tests/all-tests.nix

@@ -108,6 +108,7 @@ in {
   breitbandmessung = handleTest ./breitbandmessung.nix {};
   brscan5 = handleTest ./brscan5.nix {};
   btrbk = handleTest ./btrbk.nix {};
+  btrbk-doas = handleTest ./btrbk-doas.nix {};
   btrbk-no-timer = handleTest ./btrbk-no-timer.nix {};
   btrbk-section-order = handleTest ./btrbk-section-order.nix {};
   buildbot = handleTest ./buildbot.nix {};

nixos/tests/btrbk-doas.nix

@@ -0,0 +1,114 @@
+import ./make-test-python.nix ({ pkgs, ... }:
+
+  let
+    privateKey = ''
+      -----BEGIN OPENSSH PRIVATE KEY-----
+      b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+      QyNTUxOQAAACBx8UB04Q6Q/fwDFjakHq904PYFzG9pU2TJ9KXpaPMcrwAAAJB+cF5HfnBe
+      RwAAAAtzc2gtZWQyNTUxOQAAACBx8UB04Q6Q/fwDFjakHq904PYFzG9pU2TJ9KXpaPMcrw
+      AAAEBN75NsJZSpt63faCuaD75Unko0JjlSDxMhYHAPJk2/xXHxQHThDpD9/AMWNqQer3Tg
+      9gXMb2lTZMn0pelo8xyvAAAADXJzY2h1ZXR6QGt1cnQ=
+      -----END OPENSSH PRIVATE KEY-----
+    '';
+    publicKey = ''
+      ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHHxQHThDpD9/AMWNqQer3Tg9gXMb2lTZMn0pelo8xyv
+    '';
+  in
+  {
+    name = "btrbk-doas";
+    meta = with pkgs.lib; {
+      maintainers = with maintainers; [ symphorien tu-maurice ];
+    };
+
+    nodes = {
+      archive = { ... }: {
+        security.sudo.enable = false;
+        security.doas.enable = true;
+        environment.systemPackages = with pkgs; [ btrfs-progs ];
+        # note: this makes the privateKey world readable.
+        # don't do it with real ssh keys.
+        environment.etc."btrbk_key".text = privateKey;
+        services.btrbk = {
+          extraPackages = [ pkgs.lz4 ];
+          instances = {
+            remote = {
+              onCalendar = "minutely";
+              settings = {
+                ssh_identity = "/etc/btrbk_key";
+                ssh_user = "btrbk";
+                stream_compress = "lz4";
+                volume = {
+                  "ssh://main/mnt" = {
+                    target = "/mnt";
+                    snapshot_dir = "btrbk/remote";
+                    subvolume = "to_backup";
+                  };
+                };
+              };
+            };
+          };
+        };
+      };
+
+      main = { ... }: {
+        security.sudo.enable = false;
+        security.doas.enable = true;
+        environment.systemPackages = with pkgs; [ btrfs-progs ];
+        services.openssh = {
+          enable = true;
+          passwordAuthentication = false;
+          kbdInteractiveAuthentication = false;
+        };
+        services.btrbk = {
+          extraPackages = [ pkgs.lz4 ];
+          sshAccess = [
+            {
+              key = publicKey;
+              roles = [ "source" "send" "info" "delete" ];
+            }
+          ];
+          instances = {
+            local = {
+              onCalendar = "minutely";
+              settings = {
+                volume = {
+                  "/mnt" = {
+                    snapshot_dir = "btrbk/local";
+                    subvolume = "to_backup";
+                  };
+                };
+              };
+            };
+          };
+        };
+      };
+    };
+
+    testScript = ''
+      start_all()
+
+      # create btrfs partition at /mnt
+      for machine in (archive, main):
+        machine.succeed("dd if=/dev/zero of=/data_fs bs=120M count=1")
+        machine.succeed("mkfs.btrfs /data_fs")
+        machine.succeed("mkdir /mnt")
+        machine.succeed("mount /data_fs /mnt")
+
+      # what to backup and where
+      main.succeed("btrfs subvolume create /mnt/to_backup")
+      main.succeed("mkdir -p /mnt/btrbk/{local,remote}")
+
+      # check that local snapshots work
+      with subtest("local"):
+          main.succeed("echo foo > /mnt/to_backup/bar")
+          main.wait_until_succeeds("cat /mnt/btrbk/local/*/bar | grep foo")
+          main.succeed("echo bar > /mnt/to_backup/bar")
+          main.succeed("cat /mnt/btrbk/local/*/bar | grep foo")
+
+      # check that btrfs send/receive works and ssh access works
+      with subtest("remote"):
+          archive.wait_until_succeeds("cat /mnt/*/bar | grep bar")
+          main.succeed("echo baz > /mnt/to_backup/bar")
+          archive.succeed("cat /mnt/*/bar | grep bar")
+    '';
+  })

pkgs/tools/backup/btrbk/default.nix

@@ -54,7 +54,7 @@ stdenv.mkDerivation rec {
   '';
 
   passthru.tests = {
-    inherit (nixosTests) btrbk btrbk-no-timer btrbk-section-order;
+    inherit (nixosTests) btrbk btrbk-no-timer btrbk-section-order btrbk-doas;
   };
 
   passthru.updateScript = genericUpdater {