2 files changed, 24 insertions, 0 deletions
diff --git a/rest_framework/authentication.py b/rest_framework/authentication.py
index 30c78ebc..e557abed 100644
--- a/rest_framework/authentication.py
+++ b/rest_framework/authentication.py
@@ -21,6 +21,14 @@ class BaseAuthentication(object):
         """
         raise NotImplementedError(".authenticate() must be overridden.")
 
+    def authenticate_header(self, request):
+        """
+        Return a string to be used as the value of the `WWW-Authenticate`
+        header in a `401 Unauthenticated` response, or `None` if the
+        authentication scheme should return `403 Permission Denied` responses.
+        """
+        pass
+
 
 class BasicAuthentication(BaseAuthentication):
     """
diff --git a/rest_framework/exceptions.py b/rest_framework/exceptions.py
index 89479deb..d635351c 100644
--- a/rest_framework/exceptions.py
+++ b/rest_framework/exceptions.py
@@ -23,6 +23,22 @@ class ParseError(APIException):
         self.detail = detail or self.default_detail
 
 
+class AuthenticationFailed(APIException):
+    status_code = status.HTTP_401_UNAUTHORIZED
+    default_detail = 'Incorrect authentication credentials.'
+
+    def __init__(self, detail=None):
+        self.detail = detail or self.default_detail
+
+
+class NotAuthenticated(APIException):
+    status_code = status.HTTP_401_UNAUTHORIZED
+    default_detail = 'Authentication credentials were not provided.'
+
+    def __init__(self, detail=None):
+        self.detail = detail or self.default_detail
+
+
 class PermissionDenied(APIException):
     status_code = status.HTTP_403_FORBIDDEN
     default_detail = 'You do not have permission to perform this action.'