Revert "fix(decrypt): 修复 SQLCipher 密钥兼容性回归"

This reverts commit 22399f4110.

src/wechat_decrypt_tool/wechat_decrypt.py

@@ -43,29 +43,6 @@ def _derive_mac_key(raw_key: bytes, salt: bytes) -> bytes:
     return hashlib.pbkdf2_hmac("sha512", raw_key, mac_salt, 2, dklen=KEY_SIZE)
 
 
-def _derive_sqlcipher_enc_key(key_material: bytes, salt: bytes) -> bytes:
-    return hashlib.pbkdf2_hmac("sha512", key_material, salt, 256000, dklen=KEY_SIZE)
-
-
-def _resolve_page1_key_material(key_material: bytes, page1: bytes) -> tuple[bytes, bytes, str] | None:
-    salt = page1[:SALT_SIZE]
-    stored_page1_hmac = page1[PAGE_SIZE - HMAC_SIZE : PAGE_SIZE]
-
-    candidates = [
-        ("raw_enc_key", key_material, _derive_mac_key(key_material, salt)),
-    ]
-
-    derived_key = _derive_sqlcipher_enc_key(key_material, salt)
-    candidates.append(("sqlcipher_passphrase", derived_key, _derive_mac_key(derived_key, salt)))
-
-    for mode, enc_key, mac_key in candidates:
-        expected_page1_hmac = _compute_page_hmac(mac_key, page1, 1)
-        if stored_page1_hmac == expected_page1_hmac:
-            return enc_key, mac_key, mode
-
-    return None
-
-
 def _compute_page_hmac(mac_key: bytes, page: bytes, page_num: int) -> bytes:
     offset = SALT_SIZE if page_num == 1 else 0
     data_end = PAGE_SIZE - RESERVE_SIZE + IV_SIZE
@@ -346,9 +323,8 @@ class WeChatDatabaseDecryptor:
     def decrypt_database(self, db_path: str, output_path: str) -> bool:
         """解密微信4.x版本数据库
 
-        兼容两种输入形态：
-        - raw enc_key（部分内存扫描/工具直接返回）
-        - SQLCipher 口令/基础 key（需先用数据库 salt 做一轮 PBKDF2）
+        这里传入的 key 已经是从微信进程内存提取出的 raw enc_key，
+        不是 SQLCipher 的口令，因此不能再做一轮 PBKDF2。
         """
         from .logging_config import get_logger
         logger = get_logger(__name__)
@@ -394,14 +370,15 @@ class WeChatDatabaseDecryptor:
                 tmp_output_path = ""
                 return True
 
-            resolved_key_material = _resolve_page1_key_material(self.key_bytes, page1)
-            if resolved_key_material is None:
+            salt = page1[:SALT_SIZE]
+            mac_key = _derive_mac_key(self.key_bytes, salt)
+            expected_page1_hmac = _compute_page_hmac(mac_key, page1, 1)
+            stored_page1_hmac = page1[PAGE_SIZE - HMAC_SIZE : PAGE_SIZE]
+            if stored_page1_hmac != expected_page1_hmac:
                 message = f"当前数据库密钥不正确，或该密钥不属于当前账号/当前设备: {db_path}"
                 self._set_last_error("key_mismatch", message)
                 logger.error(f"页面 1 HMAC验证失败，密钥与数据库不匹配: {db_path}")
                 return False
-            enc_key, mac_key, key_mode = resolved_key_material
-            logger.info(f"页面 1 HMAC验证通过: mode={key_mode} path={db_path}")
 
             total_pages = (file_size + PAGE_SIZE - 1) // PAGE_SIZE
             successful_pages = 0
@@ -429,7 +406,7 @@ class WeChatDatabaseDecryptor:
                         logger.error(f"页面 {page_num} HMAC验证失败，终止解密: {db_path}")
                         return False
 
-                    target.write(_decrypt_page(enc_key, page, page_num))
+                    target.write(_decrypt_page(self.key_bytes, page, page_num))
                     successful_pages += 1
 
             logger.info(f"解密完成: 成功 {successful_pages} 页, 失败 0 页")