Change login flow to better verify all relevant fields.

django_etesync/serializers.py

@@ -244,18 +244,20 @@ class AuthenticationLoginChallengeSerializer(serializers.Serializer):
         raise NotImplementedError()
 
 
-class AuthenticationLoginSerializer(AuthenticationLoginChallengeSerializer):
-    challenge = BinaryBase64Field()
-    host = serializers.CharField()
+class AuthenticationLoginSerializer(serializers.Serializer):
+    response = BinaryBase64Field()
     signature = BinaryBase64Field()
 
-    def validate(self, data):
-        host = self.context.get('host', None)
-        if data['host'] != host:
-            raise serializers.ValidationError(
-                'Found wrong host name. Got: "{}" expected: "{}"'.format(data['host'], host))
+    def create(self, validated_data):
+        raise NotImplementedError()
 
-        return super().validate(data)
+    def update(self, instance, validated_data):
+        raise NotImplementedError()
+
+
+class AuthenticationLoginInnerSerializer(AuthenticationLoginChallengeSerializer):
+    challenge = BinaryBase64Field()
+    host = serializers.CharField()
 
     def create(self, validated_data):
         raise NotImplementedError()

django_etesync/views.py

@@ -40,6 +40,7 @@ from .serializers import (
         AuthenticationSignupSerializer,
         AuthenticationLoginChallengeSerializer,
         AuthenticationLoginSerializer,
+        AuthenticationLoginInnerSerializer,
         CollectionSerializer,
         CollectionItemSerializer,
         CollectionItemRevisionSerializer,
@@ -368,12 +369,17 @@ class AuthenticationViewSet(viewsets.ViewSet):
     def login(self, request):
         from datetime import datetime
 
-        serializer = AuthenticationLoginSerializer(
-            data=request.data, context={'host': request.get_host()})
+        outer_serializer = AuthenticationLoginSerializer(data=request.data)
+        if outer_serializer.is_valid():
+            response_raw = outer_serializer.validated_data['response']
+            response = json.loads(response_raw.decode())
+            signature = outer_serializer.validated_data['signature']
+
+            serializer = AuthenticationLoginInnerSerializer(data=response, context={'host': request.get_host()})
             if serializer.is_valid():
                 user = self.get_login_user(serializer)
+                host = serializer.validated_data['host']
                 challenge = serializer.validated_data['challenge']
-            signature = serializer.validated_data['signature']
 
                 salt = user.userinfo.salt
                 enc_key = self.get_encryption_key(salt)
@@ -387,11 +393,13 @@ class AuthenticationViewSet(viewsets.ViewSet):
                 elif challenge_data['userId'] != user.id:
                     content = {'code': 'wrong_user', 'detail': 'This challenge is for the wrong user'}
                     return Response(content, status=status.HTTP_400_BAD_REQUEST)
+                elif host != request.get_host():
+                    detail = 'Found wrong host name. Got: "{}" expected: "{}"'.format(host, request.get_host())
+                    content = {'code': 'wrong_host', 'detail': detail}
+                    return Response(content, status=status.HTTP_400_BAD_REQUEST)
 
-            host_hash = nacl.hash.blake2b(
-                serializer.validated_data['host'].encode(), encoder=nacl.encoding.RawEncoder)
                 verify_key = nacl.signing.VerifyKey(user.userinfo.pubkey, encoder=nacl.encoding.RawEncoder)
-            verify_key.verify(challenge + host_hash, signature)
+                verify_key.verify(response_raw, signature)
 
                 data = {
                     'token': Token.objects.get_or_create(user=user)[0].key,