1 files changed, 204 insertions, 0 deletions
diff --git a/modules/services/matrix-bridge/_mautrix-signal-module.nix b/modules/services/matrix-bridge/_mautrix-signal-module.nix
new file mode 100644
index 0000000..983d635
--- /dev/null
+++ b/modules/services/matrix-bridge/_mautrix-signal-module.nix
@@ -0,0 +1,204 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  dataDir = "/var/lib/mautrix-signal";
+  registrationFile = "${dataDir}/signal-registration.yaml";
+  cfg = config.services.mautrix-signal;
+  settingsFormat = pkgs.formats.json { };
+  settingsFile = "${dataDir}/config.json";
+  settingsFileUnsubstituted =
+    settingsFormat.generate "mautrix-signal-config.json" cfg.settings;
+
+in
+{
+  # NOTE(2024-01-11): Upstream has been moved to a Go version.
+  # Environment-based credential setting might not work.
+  options = {
+    services.mautrix-signal = {
+      enable = mkEnableOption (lib.mdDoc "Mautrix-Signal, a Matrix-Signal puppeting bridge.");
+
+      package = mkOption { type = types.package; default = pkgs.mautrix-signal; };
+
+      settings = mkOption rec {
+        apply = recursiveUpdate default;
+        inherit (settingsFormat) type;
+        default = {
+          homeserver = {
+            software = "standard";
+          };
+
+          appservice = rec {
+            database = "sqlite:///${dataDir}/mautrix-signal.db";
+            database_opts = { };
+            hostname = "localhost";
+            port = 8080;
+            address = "http://localhost:${toString port}";
+          };
+
+          signal.socket_path = config.services.signald.socketPath;
+
+          bridge = {
+            permissions."*" = "relay";
+            relay.whitelist = [ ];
+            double_puppet_server_map = { };
+            login_shared_secret_map = { };
+          };
+
+          logging = {
+            min_level = "debug";
+            writers = [
+              {
+                type = "stdout";
+                format = "pretty-colored";
+              }
+            ];
+          };
+        };
+        example = literalExpression ''
+          {
+            homeserver = {
+              address = "http://localhost:8008";
+              domain = "public-domain.tld";
+            };
+
+            appservice.public = {
+              prefix = "/public";
+              external = "https://public-appservice-address/public";
+            };
+
+            bridge.permissions = {
+              "example.com" = "full";
+              "@admin:example.com" = "admin";
+            };
+          }
+        '';
+        description = lib.mdDoc ''
+          {file}`config.yaml` configuration as a Nix attribute set.
+          Configuration options should match those described in
+          [example-config.yaml](https://github.com/mautrix/signal/blob/master/signal/example-config.yaml).
+
+          Secret tokens should be specified using {option}`environmentFile`
+          instead of this world-readable attribute set.
+        '';
+      };
+
+      environmentFile = mkOption {
+        type = types.nullOr types.path;
+        default = null;
+        description = lib.mdDoc ''
+          File containing environment variables to be passed to the mautrix-signal service,
+          in which secret tokens can be specified securely by defining values for e.g.
+          `MAUTRIX_SIGNAL_APPSERVICE_AS_TOKEN`,
+          `MAUTRIX_SIGNAL_APPSERVICE_HS_TOKEN`,
+
+          These environment variables can also be used to set other options by
+          replacing hierarchy levels by `.`, converting the name to uppercase
+          and prepending `MAUTRIX_SIGNAL_`.
+          For example, the first value above maps to
+          {option}`settings.appservice.as_token`.
+
+          The environment variable values can be prefixed with `json::` to have
+          them be parsed as JSON. For example, `login_shared_secret_map` can be
+          set as follows:
+          `MAUTRIX_SIGNAL_BRIDGE_LOGIN_SHARED_SECRET_MAP=json::{"example.com":"secret"}`.
+        '';
+      };
+
+      serviceDependencies = mkOption {
+        type = with types; listOf str;
+        default = optional config.services.matrix-synapse.enable "matrix-synapse.service";
+        defaultText = literalExpression ''
+          optional config.services.matrix-synapse.enable "matrix-synapse.service"
+        '';
+        description = lib.mdDoc ''
+          List of Systemd services to require and wait for when starting the application service.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.signald.enable = true;
+
+    systemd.services.mautrix-signal = {
+      description = "Mautrix-Signal, a Matrix-Signal puppeting bridge.";
+
+      wantedBy = [ "multi-user.target" ];
+      wants = [ "network-online.target" ] ++ cfg.serviceDependencies;
+      after = [ "network-online.target" ] ++ cfg.serviceDependencies;
+      path = [ pkgs.lottieconverter pkgs.ffmpeg-full ];
+
+      # TODO(2023-01-11): Still relevant in Go version?
+      # mautrix-signal tries to generate a dotfile in the home directory of
+      # the running user if using a postgresql database:
+      #
+      #  File "python3.10/site-packages/asyncpg/connect_utils.py", line 257, in _dot_postgre>
+      #    return (pathlib.Path.home() / '.postgresql' / filename).resolve()
+      #  File "python3.10/pathlib.py", line 1000, in home
+      #    return cls("~").expanduser()
+      #  File "python3.10/pathlib.py", line 1440, in expanduser
+      #    raise RuntimeError("Could not determine home directory.")
+      # RuntimeError: Could not determine home directory.
+      environment.HOME = dataDir;
+
+      preStart = ''
+        # substitute the settings file by environment variables
+        # in this case read from EnvironmentFile
+        test -f '${settingsFile}' && rm -f '${settingsFile}'
+        old_umask=$(umask)
+        umask 0177
+        ${pkgs.envsubst}/bin/envsubst \
+          -o '${settingsFile}' \
+          -i '${settingsFileUnsubstituted}' \
+        umask $old_umask
+
+        # generate the appservice's registration file if absent
+        if [ ! -f '${registrationFile}' ]; then
+          ${cfg.package}/bin/mautrix-signal \
+            --generate-registration \
+            --config='${settingsFile}' \
+            --registration='${registrationFile}'
+        fi
+        chmod 640 ${registrationFile}
+
+        umask 0177
+        ${pkgs.yq}/bin/yq -s '.[0].appservice.as_token = .[1].as_token
+          | .[0].appservice.hs_token = .[1].hs_token
+          | .[0]' '${settingsFile}' '${registrationFile}' \
+          > '${settingsFile}.tmp'
+        mv '${settingsFile}.tmp' '${settingsFile}'
+        umask $old_umask
+      '';
+
+      serviceConfig = {
+        Type = "simple";
+        Restart = "always";
+
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        ProtectKernelTunables = true;
+        ProtectKernelModules = true;
+        ProtectControlGroups = true;
+
+        DynamicUser = true;
+        SupplementaryGroups = [ "signald" ];
+        PrivateTmp = true;
+        WorkingDirectory = cfg.package; # necessary for the database migration scripts to be found
+        StateDirectory = baseNameOf dataDir;
+        UMask = "0027";
+        EnvironmentFile = cfg.environmentFile;
+
+        ExecStart = ''
+          ${cfg.package}/bin/mautrix-signal \
+            --config='${settingsFile}'
+        '';
+
+      restartTriggers = [settingsFileUnsubstituted];
+      };
+    };
+  };
+
+  # meta.maintainers = with maintainers; [ boppyt ];
+}