UTF-8 encode basic auth username and password

Also accept bytes to allow user control over encoding.

Closes twisted#268.

changelog.d/268.feature.rst

@@ -0,0 +1 @@
+The *auth* parameter now accepts arbitrary text and `bytes` for usernames and passwords. Text is encoded as UTF-8, per :rfc:`7617`. Previously only ASCII was allowed.

src/treq/auth.py

@@ -2,7 +2,8 @@
 # See LICENSE for details.
 from __future__ import absolute_import, division, print_function
 
-import base64
+import binascii
+from typing import Union
 
 from twisted.web.http_headers import Headers
 from twisted.web.iweb import IAgent
@@ -46,6 +47,7 @@ def request(self, method, uri, headers=None, bodyProducer=None):
 
 
 def add_basic_auth(agent, username, password):
+    # type: (IAgent, Union[str, bytes], Union[str, bytes]) -> IAgent
     """
     Wrap an agent to add HTTP basic authentication
 
@@ -59,16 +61,21 @@ def add_basic_auth(agent, username, password):
     of the *Authorization* header is server-defined.
 
     :param agent: Agent to wrap.
-    :param username: Username as an ASCII string.
-    :param password: Password as an ASCII string.
+    :param username: The username.
+    :param password: The password.
 
     :returns: :class:`~twisted.web.iweb.IAgent`
     """
-    creds = base64.b64encode(
-        '{0}:{1}'.format(username, password).encode('ascii'))
+    if not isinstance(username, bytes):
+        username = username.encode('utf-8')
+    if not isinstance(password, bytes):
+        password = password.encode('utf-8')
+
+    creds = binascii.b2a_base64(b'%s:%s' % (username, password)).rstrip(b'\n')
     return _RequestHeaderSettingAgent(
         agent,
-        Headers({b'Authorization': [b'Basic ' + creds]}))
+        Headers({b'Authorization': [b'Basic ' + creds]}),
+    )
 
 
 def add_auth(agent, auth_config):

src/treq/test/test_auth.py

@@ -93,6 +93,39 @@ def test_add_basic_auth_huge(self):
             Headers({b'authorization': [auth]}),
         )
 
+    def test_add_basic_auth_utf8(self):
+        """
+        Basic auth username and passwords given as `str` are encoded as UTF-8.
+
+        https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication#Character_encoding_of_HTTP_authentication
+        """
+        agent, requests = recorder()
+        auth = (u'\u16d7', u'\u16b9')
+        authAgent = add_auth(agent, auth)
+
+        authAgent.request(b'method', b'uri')
+
+        self.assertEqual(
+            requests[0].headers,
+            Headers({b'Authorization': [b'Basic 4ZuXOuGauQ==']}),
+        )
+
+    def test_add_basic_auth_bytes(self):
+        """
+        Basic auth can be passed as `bytes`, allowing the user full control
+        over the encoding.
+        """
+        agent, requests = recorder()
+        auth = (b'\x01\x0f\xff', b'\xff\xf0\x01')
+        authAgent = add_auth(agent, auth)
+
+        authAgent.request(b'method', b'uri')
+
+        self.assertEqual(
+            requests[0].headers,
+            Headers({b'Authorization': [b'Basic AQ//Ov/wAQ==']}),
+        )
+
     def test_add_unknown_auth(self):
         """
         add_auth() raises UnknownAuthConfig when given anything other than