appservice: Add {as,hs}_token_path config options

changelog.d/18071.feature

@@ -0,0 +1 @@
+Add appservice config options `as_token_path` and `hs_token_path`.

synapse/config/appservice.py

@@ -30,10 +30,20 @@
 from synapse.appservice import ApplicationService
 from synapse.types import JsonDict, UserID
 
-from ._base import Config, ConfigError
+from ._base import Config, ConfigError, read_file
 
 logger = logging.getLogger(__name__)
 
+CONFLICTING_AS_TOKEN_OPTS_ERROR = """\
+You have configured both `as_token` and `as_token_path`.
+These are mutually incompatible.
+"""
+
+CONFLICTING_HS_TOKEN_OPTS_ERROR = """\
+You have configured both `hs_token` and `hs_token_path`.
+These are mutually incompatible.
+"""
+
 
 class AppServiceConfig(Config):
     section = "appservice"
@@ -105,13 +115,37 @@ def load_appservices(
 def _load_appservice(
     hostname: str, as_info: JsonDict, config_filename: str
 ) -> ApplicationService:
-    required_string_fields = ["id", "as_token", "hs_token", "sender_localpart"]
-    for field in required_string_fields:
-        if not isinstance(as_info.get(field), str):
+    required_fields = ["id", "sender_localpart"]
+    for field in required_fields:
+        if field not in as_info:
+            raise KeyError("Required field: '%s' (%s)" % (field, config_filename))
+    string_fields = [
+        "id",
+        "sender_localpart",
+        "as_token",
+        "as_token_path",
+        "hs_token",
+        "hs_token_path",
+    ]
+    for field in string_fields:
+        if not isinstance(as_info.get(field, ""), (str, type(None))):
             raise KeyError(
-                "Required string field: '%s' (%s)" % (field, config_filename)
+                "Field must be a string: '%s' (%s)" % (field, config_filename)
             )
 
+    if token_path := as_info.get("as_token_path"):
+        if as_info.get("as_token"):
+            raise ConfigError(CONFLICTING_AS_TOKEN_OPTS_ERROR)
+        token = read_file(token_path, ("as_token_path",)).strip()
+    else:
+        token = as_info["as_token"]
+
+    hs_token = as_info.get("hs_token")
+    if hs_token_path := as_info.get("hs_token_path"):
+        if "hs_token" in as_info:
+            raise ConfigError(CONFLICTING_HS_TOKEN_OPTS_ERROR)
+        hs_token = read_file(hs_token_path, ("hs_token_path",)).strip()
+
     # 'url' must either be a string or explicitly null, not missing
     # to avoid accidentally turning off push for ASes.
     if not isinstance(as_info.get("url"), str) and as_info.get("url", "") is not None:
@@ -196,10 +230,10 @@ def _load_appservice(
         )
 
     return ApplicationService(
-        token=as_info["as_token"],
+        token=token,
         url=as_info["url"],
         namespaces=as_info["namespaces"],
-        hs_token=as_info["hs_token"],
+        hs_token=hs_token,
         sender=user_id,
         id=as_info["id"],
         protocols=protocols,

tests/config/test_load.py

@@ -27,6 +27,7 @@
 
 from synapse.config import ConfigError
 from synapse.config._base import RootConfig
+from synapse.config.appservice import _load_appservice
 from synapse.config.homeserver import HomeServerConfig
 
 from tests.config.utils import ConfigFileTestCase
@@ -179,3 +180,39 @@ def test_secret_files_existing(
             config = HomeServerConfig.load_config("", ["-c", self.config_file])
 
             self.assertEqual(get_secret(config), b"53C237")
+
+    def test_secret_files_appservice(self) -> None:
+        with tempfile.NamedTemporaryFile(buffering=0) as token_file:
+            token_file.write(b"53C237")
+
+            as_info = {
+                "id": "fake-as-id",
+                "url": "example.org",
+                "as_token_path": token_file.name,
+                "hs_token_path": token_file.name,
+                "sender_localpart": "not-real-part",
+                "namespaces": {},
+            }
+
+            appservice = _load_appservice(
+                hostname="example.org",
+                as_info=as_info,
+                config_filename="mock-config-file.name",
+            )
+
+            self.assertEqual(appservice.token, "53C237")
+            self.assertEqual(appservice.hs_token, "53C237")
+
+            with self.assertRaises(ConfigError):
+                _load_appservice(
+                    hostname="example.org",
+                    as_info={**as_info, "as_token_path": "/does/not/exist"},
+                    config_filename="mock-config-file.name",
+                )
+
+            with self.assertRaises(ConfigError):
+                _load_appservice(
+                    hostname="example.org",
+                    as_info={**as_info, "hs_token_path": "/does/not/exist"},
+                    config_filename="mock-config-file.name",
+                )