[fix] secret_key can be bytes instead of a string (#1602)

Fix #1600
In settings.yml, the secret_key can be written as string or as base64 encoded data using !!binary notation.

searx/utils.py

@@ -384,10 +384,17 @@ def load_module(filename, module_dir):
 
 
 def new_hmac(secret_key, url):
+    try:
+        secret_key_bytes = bytes(secret_key, 'utf-8')
+    except TypeError as err:
+        if isinstance(secret_key, bytes):
+            secret_key_bytes = secret_key
+        else:
+            raise err
     if sys.version_info[0] == 2:
         return hmac.new(bytes(secret_key), url, hashlib.sha256).hexdigest()
     else:
-        return hmac.new(bytes(secret_key, 'utf-8'), url, hashlib.sha256).hexdigest()
+        return hmac.new(secret_key_bytes, url, hashlib.sha256).hexdigest()
 
 
 def to_string(obj):

tests/unit/test_utils.py

@@ -128,3 +128,17 @@ class TestUnicodeWriter(SearxTestCase):
         rows = [1, 2, 3]
         self.unicode_writer.writerows(rows)
         self.assertEqual(self.unicode_writer.writerow.call_count, len(rows))
+
+
+class TestNewHmac(SearxTestCase):
+
+    def test_bytes(self):
+        for secret_key in ['secret', b'secret', 1]:
+            if secret_key == 1:
+                with self.assertRaises(TypeError):
+                    utils.new_hmac(secret_key, b'http://example.com')
+                continue
+            res = utils.new_hmac(secret_key, b'http://example.com')
+            self.assertEqual(
+                res,
+                '23e2baa2404012a5cc8e4a18b4aabf0dde4cb9b56f679ddc0fd6d7c24339d819')