Change API protocol to fix json normalization

A dictionnary's order is not deterministic (eg. when switching python
versions), thus the previous protocol would often fail to authenticate a
legitimate request.

api/client/apiclient.py

@@ -33,7 +33,8 @@ def sendReq(url):
         mac = hmac.new(key.encode('utf-8'),
                        msg=str(int(time)).encode('utf-8'),
                        digestmod=hashlib.sha256)
-        mac.update(json.dumps(payload).encode('utf-8'))
+        payload_enc = json.dumps(payload)
+        mac.update(payload_enc.encode('utf-8'))
 
         auth = {
             'keyId': keyId,
@@ -43,7 +44,7 @@ def sendReq(url):
 
         return {
             'auth': auth,
-            'req': payload,
+            'req': payload_enc,
         }
 
     def decorator(fct):

api/views.py

@@ -20,8 +20,7 @@ def authentify(data, payload):
     except models.ApiKey.DoesNotExist:
         return response.HttpResponseForbidden('Bad authentication')
 
-    normPayload = json.dumps(payload)
-    if not key.isCorrect(data['timestamp'], data['hmac'], normPayload):
+    if not key.isCorrect(data['timestamp'], data['hmac'], payload):
         return response.HttpResponseForbidden('Bad authentication')
 
 
@@ -30,22 +29,31 @@ def apiView(required=[]):
         @csrf_exempt
         def wrap(request, *args, **kwargs):
             try:
-                data = json.loads(request.body)
-            except json.decoder.JSONDecoreError:
+                data = json.loads(request.body.decode('utf-8'))
+            except TypeError:
+                return response.HttpResponseBadRequest("Bad packet format")
+            except json.decoder.JSONDecodeError:
                 return response.HttpResponseBadRequest("Bad json")
 
             try:
                 authData = data['auth']
-                reqData = data['req']
+                reqDataOrig = data['req']
             except KeyError:
                 return response.HttpResponseBadRequest("Bad request format")
 
+            try:
+                reqData = json.loads(reqDataOrig)
+            except TypeError:
+                return response.HttpResponseBadRequest("Bad packet format")
+            except json.decoder.JSONDecodeError:
+                return response.HttpResponseBadRequest("Bad inner json")
+
             for field in required:
                 if field not in reqData:
                     return response.HttpResponseBadRequest(
                         "Missing field {}".format(field))
 
-            authVal = authentify(authData, reqData)
+            authVal = authentify(authData, reqDataOrig)
             if authVal is not None:
                 return authVal