billing: Add function to sign strings.

zilencer/lib/stripe.py

@@ -2,17 +2,19 @@ import datetime
 from functools import wraps
 import logging
 import os
-from typing import Any, Callable, Optional, TypeVar
+from typing import Any, Callable, Optional, TypeVar, Tuple
 import ujson
 
 from django.conf import settings
 from django.db import transaction
 from django.utils.translation import ugettext as _
+from django.core.signing import Signer
 import stripe
 
 from zerver.lib.exceptions import JsonableError
 from zerver.lib.logging_util import log_to_file
 from zerver.lib.timestamp import datetime_to_timestamp, timestamp_to_datetime
+from zerver.lib.utils import generate_random_token
 from zerver.models import Realm, UserProfile, RealmAuditLog
 from zilencer.models import Customer, Plan
 from zproject.settings import get_secret
@@ -52,6 +54,15 @@ CallableT = TypeVar('CallableT', bound=Callable[..., Any])
 def get_seat_count(realm: Realm) -> int:
     return UserProfile.objects.filter(realm=realm, is_active=True, is_bot=False).count()
 
+def sign_string(string: str) -> Tuple[str, str]:
+    salt = generate_random_token(64)
+    signer = Signer(salt=salt)
+    return signer.sign(string), salt
+
+def unsign_string(signed_string: str, salt: str) -> str:
+    signer = Signer(salt=salt)
+    return signer.unsign(signed_string)
+
 class StripeError(JsonableError):
     pass