add the function to check cache data for tampering.

mdrsclient/cache.py

@@ -1,5 +1,6 @@
 import dataclasses
 import fcntl
+import hashlib
 import json
 import os
 
@@ -7,6 +8,7 @@ from pydantic import ValidationError
 from pydantic.dataclasses import dataclass
 from pydantic.tools import parse_obj_as
 
+from mdrsclient.exceptions import UnexpectedException
 from mdrsclient.models import Laboratories, Token, User
 from mdrsclient.settings import CONFIG_DIR_PATH
 
@@ -16,6 +18,18 @@ class CacheData:
     user: User | None
     token: Token | None
     laboratories: Laboratories
+    digest: str | None
+
+    def calc_digest(self) -> str:
+        return hashlib.sha256(
+            json.dumps(
+                [
+                    None if self.user is None else dataclasses.asdict(self.user),
+                    None if self.token is None else dataclasses.asdict(self.token),
+                    dataclasses.asdict(self.laboratories),
+                ]
+            ).encode("utf-8")
+        ).hexdigest()
 
 
 class CacheFile:
@@ -28,7 +42,7 @@ class CacheFile:
         self.serial = -1
         self.cache_dir = os.path.join(CONFIG_DIR_PATH, "cache")
         self.cache_file = os.path.join(self.cache_dir, remote + ".json")
-        self.data = CacheData(user=None, token=None, laboratories=Laboratories([]))
+        self.data = CacheData(user=None, token=None, laboratories=Laboratories([]), digest=None)
 
     def dump(self) -> CacheData | None:
         self.__load()
@@ -88,21 +102,28 @@ class CacheFile:
             if self.serial != serial:
                 try:
                     with open(self.cache_file) as f:
-                        self.data = parse_obj_as(CacheData, json.load(f))
-                except ValidationError:
+                        data = parse_obj_as(CacheData, json.load(f))
+                        print(f"{data.digest} : {data.calc_digest()}")
+                        if data.digest != data.calc_digest():
+                            raise UnexpectedException("Cache data has been broken.")
+                        self.data = data
+                except (ValidationError, UnexpectedException):
                     self.__clear()
                     self.__save()
                 else:
                     self.serial = serial
         else:
-            self.data.token = None
+            self.__clear()
             self.serial = -1
 
     def __save(self) -> None:
         self.__ensure_cache_dir()
         with open(self.cache_file, "w") as f:
             fcntl.flock(f, fcntl.LOCK_EX)
+            self.data.digest = self.data.calc_digest()
             f.write(json.dumps(dataclasses.asdict(self.data)))
+        stat = os.stat(self.cache_file)
+        self.serial = hash((stat.st_uid, stat.st_gid, stat.st_mode, stat.st_size, stat.st_mtime))
         # ensure file is secure.
         os.chmod(self.cache_file, 0o600)