dynamicdns: Don't log password during backup

Closes: #2587.

Tests:

- When adding a users to a group as admin, the log messages don't show
authorization password in clear text. Instead the value is masked as '****'.
This works even when add_user_to_group privileged call uses keyword arguments
instead of positional arguments.

- When taking a backup for dynamicdns app, log message for the dump_settings()
does not show account passwords. Instead the value is masked as '****'.

- When a privileged method contains an annotation 'password: str' an exception
is raised during startup saying that it should be a secret. When the annotation
is 'password: secret_str' it works. When the annotation is 'password:
Annotated[str, Secret]' it works.

Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

freedombox/actions.py

@@ -23,6 +23,11 @@ socket_path = '/run/freedombox/privileged.socket'
 thread_storage = threading.local()
 
 
+class Secret:
+    """Annotate a arg as containing a secret that should not be logged."""
+    pass
+
+
 # An alias for 'str' to mark some strings as sensitive. Sensitive strings are
 # not logged. Use 'type secret_str = str' when Python 3.11 support is no longer
 # needed.
@@ -251,6 +256,15 @@ class ProcessBufferedReader(io.BufferedReader):
             logger.exception('Closing process failed after raw output')
 
 
+def _is_secret(annotation):
+    """Return whether an argument annotation is a secret."""
+    if annotation in [secret_str, secret_str | None]:
+        return True
+
+    metadata = getattr(annotation, '__metadata__', ())
+    return any(datum == Secret for datum in metadata)
+
+
 def _format_args(func, args, kwargs):
     """Return a loggable representation of arguments."""
     argspec = inspect.getfullargspec(func)
@@ -260,7 +274,7 @@ def _format_args(func, args, kwargs):
     args_str_list = []
     for arg_index, arg_value in enumerate(args):
         arg_name = argspec.args[arg_index]
-        if argspec.annotations[arg_name] in [secret_str, secret_str | None]:
+        if _is_secret(argspec.annotations[arg_name]):
             value = '****'
         else:
             value = json.dumps(arg_value)
@@ -269,7 +283,7 @@ def _format_args(func, args, kwargs):
 
     kwargs_str_list = []
     for arg_name, arg_value in kwargs.items():
-        if argspec.annotations[arg_name] in [secret_str, secret_str | None]:
+        if _is_secret(argspec.annotations[arg_name]):
             value = "****"
         else:
             value = json.dumps(arg_value)
@@ -324,9 +338,10 @@ def _check_privileged_action_arguments(func):
     for arg_name, arg_value in argspec.annotations.items():
         for keyword in ('password', 'passphrase', 'secret'):
             if keyword in arg_name:
-                if arg_value not in [secret_str, secret_str | None]:
+                if not _is_secret(arg_value):
                     raise SyntaxError(
-                        f'Argument {arg_name} should likely be a "secret_str"')
+                        f'Argument {arg_name} should likely be a "secret_str" '
+                        'or "Annotated[str, Secret]"')
 
 
 def _get_privileged_action_module_name(func):
@@ -576,6 +591,10 @@ def _privileged_assert_valid_type(arg_name, value, annotation):
 
         return
 
+    if typing.get_origin(annotation) == typing.Annotated:
+        _privileged_assert_valid_type(arg_name, value, annotation.__origin__)
+        return
+
     # secret_str should be a regular string
     if annotation == secret_str:
         if not isinstance(value, str):
@@ -606,7 +625,7 @@ def _privileged_assert_valid_type(arg_name, value, annotation):
 
         return
 
-    # 'list[dict]' or 'typing.List[dict]'
+    # 'dict[int, str]' or 'typing.Dict[int, str]'
     if getattr(annotation, '__origin__', None) == dict:
         if not isinstance(value, dict):
             raise TypeError(f'Expected type dict for {arg_name}')

freedombox/modules/backups/privileged.py

@@ -9,13 +9,14 @@ import re
 import shutil
 import subprocess
 import tarfile
+from typing import Annotated
 
 from django.utils.translation import gettext_lazy as _
 
 from freedombox import action_utils, actions
 from freedombox import app as app_module
 from freedombox import module_loader
-from freedombox.actions import privileged, secret_str
+from freedombox.actions import Secret, privileged, secret_str
 from freedombox.utils import Version
 
 from . import errors
@@ -472,7 +473,9 @@ def _assert_app_id(app_id):
 
 @reraise_known_errors
 @privileged
-def dump_settings(app_id: str, settings: dict[str, int | float | bool | str]):
+def dump_settings(app_id: str,
+                  settings: Annotated[dict[str, int | float | bool | str],
+                                      Secret]):
     """Dump an app's settings to a JSON file."""
     _assert_app_id(app_id)
     settings_path = BACKUPS_DATA_PATH / f'{app_id}-settings.json'