fix(decrypt): 修复 SQLCipher 密钥兼容性回归

- 解密时同时兼容 raw enc_key 与 SQLCipher 派生密钥两种输入形态
- 通过首页 HMAC 自动识别可用密钥模式，避免真实账号密钥被误判为不匹配
- 后续页面解密统一使用识别出的有效密钥，恢复数据库解密流程
- 补充 SQLCipher passphrase 场景回归测试，覆盖此次回归问题

tests/test_wechat_decrypt_raw_key.py

@@ -19,11 +19,22 @@ from wechat_decrypt_tool.wechat_decrypt import (
     SQLITE_HEADER,
     WeChatDatabaseDecryptor,
     _derive_mac_key,
+    _derive_sqlcipher_enc_key,
     decrypt_wechat_databases,
 )
 
 
-def _encrypt_page(raw_key: bytes, plain_page: bytes, page_num: int, salt: bytes, iv: bytes) -> bytes:
+def _encrypt_page(
+    raw_key: bytes,
+    plain_page: bytes,
+    page_num: int,
+    salt: bytes,
+    iv: bytes,
+    *,
+    sqlcipher_passphrase: bool = False,
+) -> bytes:
+    enc_key = _derive_sqlcipher_enc_key(raw_key, salt) if sqlcipher_passphrase else raw_key
+
     if page_num == 1:
         encrypted_input = plain_page[SALT_SIZE : PAGE_SIZE - RESERVE_SIZE]
         prefix = salt
@@ -32,7 +43,7 @@ def _encrypt_page(raw_key: bytes, plain_page: bytes, page_num: int, salt: bytes,
         prefix = b""
 
     cipher = Cipher(
-        algorithms.AES(raw_key),
+        algorithms.AES(enc_key),
         modes.CBC(iv),
         backend=default_backend(),
     )
@@ -40,7 +51,7 @@ def _encrypt_page(raw_key: bytes, plain_page: bytes, page_num: int, salt: bytes,
     encrypted = encryptor.update(encrypted_input) + encryptor.finalize()
 
     page_without_hmac = prefix + encrypted + iv
-    mac = hmac.new(_derive_mac_key(raw_key, salt), digestmod=hashlib.sha512)
+    mac = hmac.new(_derive_mac_key(enc_key, salt), digestmod=hashlib.sha512)
     mac.update(page_without_hmac[SALT_SIZE if page_num == 1 else 0 :])
     mac.update(page_num.to_bytes(4, "little"))
     return page_without_hmac + mac.digest()
@@ -74,6 +85,39 @@ class WeChatDecryptRawKeyTests(unittest.TestCase):
             self.assertTrue(decryptor.decrypt_database(str(src), str(dst)))
             self.assertEqual(dst.read_bytes(), page1 + page2)
 
+    def test_decrypt_database_falls_back_to_sqlcipher_passphrase_mode(self):
+        passphrase_key = bytes.fromhex("9f5dd0d3b6d0477ea5045c9e380ee272e53927993eb548dd98a022e842d5f7bd")
+        salt = bytes.fromhex("50f4090ef6897e146f94109f13743e34")
+        iv1 = bytes.fromhex("0102030405060708090a0b0c0d0e0f10")
+        iv2 = bytes.fromhex("1112131415161718191a1b1c1d1e1f20")
+
+        page1 = _build_plain_page(0x41, first_page=True)
+        page2 = _build_plain_page(0x42, first_page=False)
+        encrypted_db = _encrypt_page(
+            passphrase_key,
+            page1,
+            1,
+            salt,
+            iv1,
+            sqlcipher_passphrase=True,
+        ) + _encrypt_page(
+            passphrase_key,
+            page2,
+            2,
+            salt,
+            iv2,
+            sqlcipher_passphrase=True,
+        )
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            src = Path(tmpdir) / "source.db"
+            dst = Path(tmpdir) / "out.db"
+            src.write_bytes(encrypted_db)
+
+            decryptor = WeChatDatabaseDecryptor(passphrase_key.hex())
+            self.assertTrue(decryptor.decrypt_database(str(src), str(dst)))
+            self.assertEqual(dst.read_bytes(), page1 + page2)
+
     def test_decrypt_database_keeps_existing_output_on_hmac_failure(self):
         good_key = bytes.fromhex("00112233445566778899aabbccddeefffedcba98765432100123456789abcdef")
         bad_key_hex = "ffeeddccbbaa998877665544332211000123456789abcdeffedcba9876543210"