Filter TMF messages for security (#1653)

* filter CoAP messages for security

* add description for CoAP interceptor possible errors

src/core/coap/coap_server.cpp

@@ -50,6 +50,7 @@ Server::Server(Ip6::Netif &aNetif, uint16_t aPort, SenderFunction aSender, Recei
 {
     mPort = aPort;
     mResources = NULL;
+    mInterceptor = NULL;
 }
 
 ThreadError Server::Start(void)
@@ -144,6 +145,11 @@ void Server::ProcessReceivedMessage(Message &aMessage, const Ip6::MessageInfo &a
     const Header::Option *coapOption;
     Message *response;
 
+    if (mInterceptor != NULL)
+    {
+        SuccessOrExit(mInterceptor(aMessage, aMessageInfo));
+    }
+
     SuccessOrExit(header.FromMessage(aMessage, 0));
     aMessage.MoveOffset(header.GetLength());
 

src/core/coap/coap_server.hpp

@@ -287,6 +287,20 @@ private:
 class Server : public CoapBase
 {
 public:
+    /**
+     * This function pointer is called before CoAP server processing a CoAP packets.
+     *
+     * @param[in]   aMessage        A reference to the message.
+     @ @param[in]   aMessageInfo    A reference to the message info associated with @p aMessage.
+     *
+     * @retval  kThreadError_None       Server should continue processing this message, other
+     *                                  return values indicates the server should stop processing
+     *                                  this message.
+     * @retval  kThreadError_Security   The message does not comply with security rules.
+     *
+     */
+    typedef ThreadError(* Interceptor)(const Message &aMessage, const Ip6::MessageInfo &aMessageInfo);
+
     /**
      * This constructor initializes the object.
      *
@@ -371,6 +385,16 @@ public:
 
     const MessageQueue &GetCachedResponses(void) const { return mResponsesQueue.GetResponses(); }
 
+    /**
+     * This method sets interceptor to be called before processing a CoAP packet.
+     *
+     * @param[in]   aInterceptor    A pointer to the interceptor.
+     *
+     */
+    void SetInterceptor(Interceptor aInterpreter) {
+        mInterceptor = aInterpreter;
+    }
+
 protected:
     void ProcessReceivedMessage(Message &aMessage, const Ip6::MessageInfo &aMessageInfo);
 
@@ -386,6 +410,7 @@ private:
     uint16_t mPort;
     Resource *mResources;
 
+    Interceptor    mInterceptor;
     ResponsesQueue mResponsesQueue;
 };
 

src/core/thread/thread_netif.cpp

@@ -111,6 +111,7 @@ ThreadNetif::ThreadNetif(Ip6::Ip6 &aIp6):
 
 {
     mKeyManager.SetMasterKey(kThreadMasterKey, sizeof(kThreadMasterKey));
+    mCoapServer.SetInterceptor(&ThreadNetif::TmfFilter);
 }
 
 ThreadError ThreadNetif::Up(void)
@@ -182,6 +183,27 @@ exit:
     return error;
 }
 
+ThreadError ThreadNetif::TmfFilter(const Message &aMessage, const Ip6::MessageInfo &aMessageInfo)
+{
+    ThreadError error = kThreadError_None;
+
+    // A TMF message must comply one of the following rules:
+    // 1. Source address is RLOC or ALOC, and destination address is RLOC, ALOC or realm-local multicast.
+    // 2. Both source and destination addresses are link-local.(for Joiner Entrust)
+    VerifyOrExit(((aMessageInfo.GetPeerAddr().IsRoutingLocator() ||
+                   aMessageInfo.GetPeerAddr().IsAnycastRoutingLocator()) &&
+                  (aMessageInfo.GetSockAddr().IsRoutingLocator() ||
+                   aMessageInfo.GetSockAddr().IsAnycastRoutingLocator() ||
+                   aMessageInfo.GetSockAddr().IsRealmLocalMulticast())) ||
+                 (aMessageInfo.GetPeerAddr().IsLinkLocal() &&
+                  aMessageInfo.GetSockAddr().IsLinkLocal()),
+                 error = kThreadError_Security);
+
+exit:
+    (void)aMessage;
+    return error;
+}
+
 otInstance *ThreadNetif::GetInstance(void)
 {
     return otInstanceFromThreadNetif(this);

src/core/thread/thread_netif.hpp

@@ -338,6 +338,8 @@ public:
     otInstance *GetInstance(void);
 
 private:
+    static ThreadError TmfFilter(const Message &aMessage, const Ip6::MessageInfo &aMessageInfo);
+
     Coap::Server mCoapServer;
     Coap::Client mCoapClient;
     AddressResolver mAddressResolver;