fix rate limiting per engine

searx/shared/shared_abstract.py

@@ -1,8 +1,11 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # pyright: strict
+import hmac
 from abc import ABC, abstractmethod
 from typing import Optional
 
+from searx import get_setting
+
 
 class SharedDict(ABC):
     @abstractmethod
@@ -20,3 +23,23 @@ class SharedDict(ABC):
     @abstractmethod
     def set_str(self, key: str, value: str, expire: Optional[int] = None):
         pass
+
+    def incr_counter(self, name: str, limit: int = 0, expire: int = 0) -> int:
+        # generate dict key from name
+        m = hmac.new(bytes(name, encoding='utf-8'), digestmod='sha256')
+        m.update(bytes(get_setting('server.secret_key'), encoding='utf-8'))
+        key = 'SearXNG_counter_' + m.hexdigest()
+
+        # check requests count
+        count = self.get_int(key)
+        if count is None:
+            # initialize counter with expiration time
+            self.set_int(key, 1, expire)
+            return 1
+        elif limit >= count or not limit:
+            # update counter
+            new_count = count + 1
+            self.set_int(key, new_count, expire)
+            return new_count
+        else:
+            return count