nixos/tang: create module for tang server (#247037)

This commit adds a module for the tang server and the related nixos test.

nixos/modules/module-list.nix

@@ -1164,6 +1164,7 @@
   ./services/security/sshguard.nix
   ./services/security/sslmate-agent.nix
   ./services/security/step-ca.nix
+  ./services/security/tang.nix
   ./services/security/tor.nix
   ./services/security/torify.nix
   ./services/security/torsocks.nix

nixos/modules/services/security/tang.nix

@@ -0,0 +1,95 @@
+{ config, lib, pkgs, ... }:
+with lib;
+let
+  cfg = config.services.tang;
+in
+{
+  options.services.tang = {
+    enable = mkEnableOption "tang";
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.tang;
+      defaultText = literalExpression "pkgs.tang";
+      description = mdDoc "The tang package to use.";
+    };
+
+    listenStream = mkOption {
+      type = with types; listOf str;
+      default = [ "7654" ];
+      example = [ "198.168.100.1:7654" "[2001:db8::1]:7654" "7654" ];
+      description = mdDoc ''
+        Addresses and/or ports on which tang should listen.
+        For detailed syntax see ListenStream in {manpage}`systemd.socket(5)`.
+      '';
+    };
+
+    ipAddressAllow = mkOption {
+      example = [ "192.168.1.0/24" ];
+      type = types.listOf types.str;
+      description = ''
+        Whitelist a list of address prefixes.
+        Preferably, internal addresses should be used.
+      '';
+    };
+
+  };
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ cfg.package ];
+
+    systemd.services."tangd@" = {
+      description = "Tang server";
+      path = [ cfg.package ];
+      serviceConfig = {
+        StandardInput = "socket";
+        StandardOutput = "socket";
+        StandardError = "journal";
+        DynamicUser = true;
+        StateDirectory = "tang";
+        RuntimeDirectory = "tang";
+        StateDirectoryMode = "700";
+        UMask = "0077";
+        CapabilityBoundingSet = [ "" ];
+        ExecStart = "${cfg.package}/libexec/tangd %S/tang";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
+        DeviceAllow = [ "/dev/stdin" ];
+        RestrictAddressFamilies = [ "AF_UNIX" ];
+        DevicePolicy = "strict";
+        PrivateDevices = true;
+        PrivateTmp = true;
+        PrivateUsers = true;
+        ProcSubset = "pid";
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectProc = "invisible";
+        ProtectSystem = "strict";
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        SystemCallFilter = [ "@system-service" "~@privileged" "~@resources" ];
+        IPAddressDeny = "any";
+        IPAddressAllow = cfg.ipAddressAllow;
+      };
+    };
+
+    systemd.sockets.tangd = {
+      description = "Tang server";
+      wantedBy = [ "sockets.target" ];
+      socketConfig = {
+        ListenStream = cfg.listenStream;
+        Accept = "yes";
+        IPAddressDeny = "any";
+        IPAddressAllow = cfg.ipAddressAllow;
+      };
+    };
+  };
+  meta.maintainers = with lib.maintainers; [ jfroche julienmalka ];
+}

nixos/tests/all-tests.nix

@@ -807,6 +807,7 @@ in {
   systemd-userdbd = handleTest ./systemd-userdbd.nix {};
   systemd-homed = handleTest ./systemd-homed.nix {};
   tandoor-recipes = handleTest ./tandoor-recipes.nix {};
+  tang = handleTest ./tang.nix {};
   taskserver = handleTest ./taskserver.nix {};
   tayga = handleTest ./tayga.nix {};
   teeworlds = handleTest ./teeworlds.nix {};

nixos/tests/tang.nix

@@ -0,0 +1,81 @@
+import ./make-test-python.nix ({ pkgs, ... }: {
+  name = "tang";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ jfroche ];
+  };
+
+  nodes.server =
+    { config
+    , pkgs
+    , modulesPath
+    , ...
+    }: {
+      imports = [
+        "${modulesPath}/../tests/common/auto-format-root-device.nix"
+      ];
+      virtualisation = {
+        emptyDiskImages = [ 512 ];
+        useBootLoader = true;
+        useEFIBoot = true;
+        # This requires to have access
+        # to a host Nix store as
+        # the new root device is /dev/vdb
+        # an empty 512MiB drive, containing no Nix store.
+        mountHostNixStore = true;
+      };
+
+      boot.loader.systemd-boot.enable = true;
+
+      networking.interfaces.eth1.ipv4.addresses = [
+        { address = "192.168.0.1"; prefixLength = 24; }
+      ];
+
+      environment.systemPackages = with pkgs; [ clevis tang cryptsetup ];
+      services.tang = {
+        enable = true;
+        ipAddressAllow = [ "127.0.0.1/32" ];
+      };
+    };
+  testScript = ''
+    start_all()
+    machine.wait_for_unit("sockets.target")
+
+    with subtest("Check keys are generated"):
+      machine.wait_until_succeeds("curl -v http://127.0.0.1:7654/adv")
+      key = machine.wait_until_succeeds("tang-show-keys 7654")
+
+    with subtest("Check systemd access list"):
+      machine.succeed("ping -c 3 192.168.0.1")
+      machine.fail("curl -v --connect-timeout 3 http://192.168.0.1:7654/adv")
+
+    with subtest("Check basic encrypt and decrypt message"):
+      machine.wait_until_succeeds(f"""echo 'Hello World' | clevis encrypt tang '{{ "url": "http://127.0.0.1:7654", "thp":"{key}"}}' > /tmp/encrypted""")
+      decrypted = machine.wait_until_succeeds("clevis decrypt < /tmp/encrypted")
+      assert decrypted.strip() == "Hello World"
+      machine.wait_until_succeeds("tang-show-keys 7654")
+
+    with subtest("Check encrypt and decrypt disk"):
+      machine.succeed("cryptsetup luksFormat --force-password --batch-mode /dev/vdb <<<'password'")
+      machine.succeed(f"""clevis luks bind -s1 -y -f -d /dev/vdb tang '{{ "url": "http://127.0.0.1:7654", "thp":"{key}" }}' <<< 'password' """)
+      clevis_luks = machine.succeed("clevis luks list -d /dev/vdb")
+      assert clevis_luks.strip() == """1: tang '{"url":"http://127.0.0.1:7654"}'"""
+      machine.succeed("clevis luks unlock -d /dev/vdb")
+      machine.succeed("find /dev/mapper -name 'luks*' -exec cryptsetup close {} +")
+      machine.succeed("clevis luks unlock -d /dev/vdb")
+      machine.succeed("find /dev/mapper -name 'luks*' -exec cryptsetup close {} +")
+      # without tang available, unlock should fail
+      machine.succeed("systemctl stop tangd.socket")
+      machine.fail("clevis luks unlock -d /dev/vdb")
+      machine.succeed("systemctl start tangd.socket")
+
+    with subtest("Rotate server keys"):
+      machine.succeed("${pkgs.tang}/libexec/tangd-rotate-keys -d /var/lib/tang")
+      machine.succeed("clevis luks unlock -d /dev/vdb")
+      machine.succeed("find /dev/mapper -name 'luks*' -exec cryptsetup close {} +")
+
+    with subtest("Test systemd service security"):
+        output = machine.succeed("systemd-analyze security tangd@.service")
+        machine.log(output)
+        assert output[-9:-1] == "SAFE :-}"
+  '';
+})

pkgs/servers/tang/default.nix

@@ -13,6 +13,7 @@
 , testers
 , tang
 , gitUpdater
+, nixosTests
 }:
 
 stdenv.mkDerivation rec {
@@ -53,10 +54,13 @@ stdenv.mkDerivation rec {
   '';
 
   passthru = {
-    tests.version = testers.testVersion {
-      package = tang;
-      command = "${tang}/libexec/tangd --version";
-      version = "tangd ${version}";
+    tests = {
+      inherit (nixosTests) tang;
+      version = testers.testVersion {
+        package = tang;
+        command = "${tang}/libexec/tangd --version";
+        version = "tangd ${version}";
+      };
     };
     updateScript = gitUpdater { };
   };
@@ -67,5 +71,6 @@ stdenv.mkDerivation rec {
     changelog = "https://github.com/latchset/tang/releases/tag/v${version}";
     maintainers = with lib.maintainers; [ fpletz ];
     license = lib.licenses.gpl3Plus;
+    mainProgram = "tangd";
   };
 }