nixos/pgbackrest: add SFTP support

nixos/modules/services/backup/pgbackrest.nix

@@ -100,6 +100,7 @@ in
                 if name == "localhost" then
                   null
                 # "posix" is the default repo type, which uses the -host option.
+                # Other types use prefixed options, for example -sftp-host.
                 else if config.type or "posix" != type then
                   null
                 else
@@ -114,6 +115,26 @@ in
                 defaultText = lib.literalExpression "name";
                 description = "Repository host when operating remotely";
               };
+
+              options.sftp-host = lib.mkOption {
+                type = nullOr str;
+                default = setHostForType "sftp";
+                defaultText = lib.literalExpression "name";
+                description = "SFTP repository host";
+              };
+
+              options.sftp-private-key-file = lib.mkOption {
+                type = nullOr (pathWith {
+                  inStore = false;
+                  absolute = true;
+                });
+                default = null;
+                description = ''
+                  SFTP private key file.
+
+                  The file must be accessible by both the pgbackrest and the postgres users.
+                '';
+              };
             }
           )
         );

nixos/tests/pgbackrest/default.nix

@@ -1,4 +1,5 @@
 { runTest }:
 {
   posix = runTest ./posix.nix;
+  sftp = runTest ./sftp.nix;
 }

nixos/tests/pgbackrest/sftp.nix

@@ -0,0 +1,95 @@
+{ lib, pkgs, ... }:
+let
+  inherit (import ../ssh-keys.nix pkgs) snakeOilPrivateKey snakeOilPublicKey;
+  backupPath = "/home/backup";
+in
+{
+  name = "pgbackrest-sftp";
+
+  meta = {
+    maintainers = with lib.maintainers; [ wolfgangwalther ];
+  };
+
+  nodes.primary =
+    {
+      pkgs,
+      ...
+    }:
+    {
+      services.postgresql = {
+        enable = true;
+        initialScript = pkgs.writeText "init.sql" ''
+          CREATE TABLE t(c text);
+          INSERT INTO t VALUES ('hello world');
+        '';
+      };
+
+      services.pgbackrest = {
+        enable = true;
+        repos.backup = {
+          type = "sftp";
+          path = "/home/backup";
+          sftp-host-key-check-type = "none";
+          sftp-host-key-hash-type = "sha256";
+          sftp-host-user = "backup";
+          sftp-private-key-file = "/var/lib/pgbackrest/sftp_key";
+        };
+
+        stanzas.default.jobs.future = {
+          schedule = "3000-01-01";
+          type = "diff";
+        };
+      };
+    };
+
+  nodes.backup =
+    {
+      nodes,
+      ...
+    }:
+    {
+      services.openssh.enable = true;
+      users.users.backup = {
+        name = "backup";
+        group = "backup";
+        isNormalUser = true;
+        createHome = true;
+        openssh.authorizedKeys.keys = [
+          snakeOilPublicKey
+        ];
+      };
+      users.groups.backup = { };
+    };
+
+  testScript =
+    { nodes, ... }:
+    ''
+      start_all()
+
+      primary.wait_for_unit("multi-user.target")
+      backup.wait_for_unit("multi-user.target")
+
+      primary.log(primary.succeed("""
+        HOME="/var/lib/pgbackrest"
+        cat ${snakeOilPrivateKey} > ~/sftp_key
+        chown -R pgbackrest:pgbackrest ~/sftp_key
+        chmod 770 ~
+      """))
+
+      with subtest("backup/restore works with local instance/remote repo (SFTP)"):
+        primary.succeed("sudo -u pgbackrest pgbackrest --stanza=default stanza-create", timeout=10)
+        primary.succeed("sudo -u pgbackrest pgbackrest --stanza=default check")
+
+        primary.systemctl("start pgbackrest-default-future")
+
+        # corrupt cluster
+        primary.systemctl("stop postgresql")
+        primary.execute("rm ${nodes.primary.services.postgresql.dataDir}/global/pg_control")
+
+        primary.succeed("sudo -u postgres pgbackrest --stanza=default restore --delta")
+
+        primary.systemctl("start postgresql")
+        primary.wait_for_unit("postgresql.service")
+        assert "hello world" in primary.succeed("sudo -u postgres psql -c 'TABLE t;'")
+    '';
+}