No payload no marker (#1645)

* no payload no marker

* raise coap error with marker but no payload

src/cli/cli_coap.cpp

@@ -266,6 +266,7 @@ ThreadError Coap::ProcessClient(int argc, char *argv[])
     otMessage *message = NULL;
     otMessageInfo messageInfo;
     otCoapHeader header;
+    uint16_t payloadLength = 0;
 
     // Default parameters
     char coapUri[kMaxUriLength] = "test";
@@ -330,15 +331,24 @@ ThreadError Coap::ProcessClient(int argc, char *argv[])
     otCoapHeaderInit(&header, coapType, coapCode);
     otCoapHeaderGenerateToken(&header, Thread::Coap::Header::kDefaultTokenLength);
     SuccessOrExit(error = otCoapHeaderAppendUriPathOptions(&header, coapUri));
-    otCoapHeaderSetPayloadMarker(&header);
+
+    if (argc > 4)
+    {
+        payloadLength = static_cast<uint16_t>(strlen(argv[4]));
+
+        if (payloadLength > 0)
+        {
+            otCoapHeaderSetPayloadMarker(&header);
+        }
+    }
 
     message = otCoapNewMessage(sInstance, &header);
     VerifyOrExit(message != NULL, error = kThreadError_NoBufs);
 
     // Embed content into message if given
-    if (argc > 4)
+    if (payloadLength > 0)
     {
-        SuccessOrExit(error = otMessageAppend(message, argv[4], static_cast<uint16_t>(strlen(argv[4]))));
+        SuccessOrExit(error = otMessageAppend(message, argv[4], payloadLength));
     }
 
     memset(&messageInfo, 0, sizeof(messageInfo));

src/core/coap/coap_header.cpp

@@ -96,6 +96,10 @@ ThreadError Header::FromMessage(const Message &aMessage, uint16_t aMetadataSize)
         if (mHeader.mBytes[mHeaderLength] == 0xff)
         {
             mHeaderLength += sizeof(uint8_t);
+            length -= sizeof(uint8_t);
+            // RFC7252: The presence of a marker followed by a zero-length payload MUST be processed
+            // as a message format error.
+            VerifyOrExit(length > 0, error = kThreadError_Parse);
             ExitNow(error = kThreadError_None);
         }