[key-manager] add a common GenerateNonce used by both MAC and MLE (#4086)

src/core/mac/mac.cpp

@@ -768,27 +768,6 @@ void Mac::FinishOperation(void)
     mOperation = kOperationIdle;
 }
 
-void Mac::GenerateNonce(const ExtAddress &aAddress, uint32_t aFrameCounter, uint8_t aSecurityLevel, uint8_t *aNonce)
-{
-    // source address
-    for (int i = 0; i < 8; i++)
-    {
-        aNonce[i] = aAddress.m8[i];
-    }
-
-    aNonce += 8;
-
-    // frame counter
-    aNonce[0] = (aFrameCounter >> 24) & 0xff;
-    aNonce[1] = (aFrameCounter >> 16) & 0xff;
-    aNonce[2] = (aFrameCounter >> 8) & 0xff;
-    aNonce[3] = (aFrameCounter >> 0) & 0xff;
-    aNonce += 4;
-
-    // security level
-    aNonce[0] = aSecurityLevel;
-}
-
 otError Mac::PrepareDataRequest(TxFrame &aFrame)
 {
     otError  error = OT_ERROR_NONE;
@@ -913,7 +892,7 @@ void Mac::ProcessTransmitAesCcm(TxFrame &aFrame, const ExtAddress *aExtAddress)
 {
     uint32_t       frameCounter = 0;
     uint8_t        securityLevel;
-    uint8_t        nonce[kNonceSize];
+    uint8_t        nonce[KeyManager::kNonceSize];
     uint8_t        tagLength;
     Crypto::AesCcm aesCcm;
     otError        error;
@@ -921,7 +900,7 @@ void Mac::ProcessTransmitAesCcm(TxFrame &aFrame, const ExtAddress *aExtAddress)
     aFrame.GetSecurityLevel(securityLevel);
     aFrame.GetFrameCounter(frameCounter);
 
-    GenerateNonce(*aExtAddress, frameCounter, securityLevel, nonce);
+    KeyManager::GenerateNonce(*aExtAddress, frameCounter, securityLevel, nonce);
 
     aesCcm.SetKey(aFrame.GetAesKey(), 16);
     tagLength = aFrame.GetFooterLength() - Frame::kFcsSize;
@@ -1380,7 +1359,7 @@ otError Mac::ProcessReceiveSecurity(RxFrame &aFrame, const Address &aSrcAddr, Ne
     uint8_t           securityLevel;
     uint8_t           keyIdMode;
     uint32_t          frameCounter;
-    uint8_t           nonce[kNonceSize];
+    uint8_t           nonce[KeyManager::kNonceSize];
     uint8_t           tag[Frame::kMaxMicSize];
     uint8_t           tagLength;
     uint8_t           keyid;
@@ -1472,7 +1451,7 @@ otError Mac::ProcessReceiveSecurity(RxFrame &aFrame, const Address &aSrcAddr, Ne
         break;
     }
 
-    GenerateNonce(*extAddress, frameCounter, securityLevel, nonce);
+    KeyManager::GenerateNonce(*extAddress, frameCounter, securityLevel, nonce);
     tagLength = aFrame.GetFooterLength() - Frame::kFcsSize;
 
     aesCcm.SetKey(macKey, 16);

src/core/mac/mac.hpp

@@ -73,7 +73,6 @@ enum
 {
     kDataPollTimeout = 100, ///< Timeout for receiving Data Frame (milliseconds).
     kSleepDelay      = 300, ///< Max sleep delay when frame is pending (milliseconds).
-    kNonceSize       = 13,  ///< Size of IEEE 802.15.4 Nonce (bytes).
 
     kScanDurationDefault = 300, ///< Default interval between channels (milliseconds).
 
@@ -645,11 +644,6 @@ private:
      */
     void ProcessTransmitSecurity(TxFrame &aFrame, bool aProcessAesCcm);
 
-    static void GenerateNonce(const ExtAddress &aAddress,
-                              uint32_t          aFrameCounter,
-                              uint8_t           aSecurityLevel,
-                              uint8_t *         aNonce);
-
     otError ProcessReceiveSecurity(RxFrame &aFrame, const Address &aSrcAddr, Neighbor *aNeighbor);
     void    UpdateIdleMode(void);
     void    StartOperation(Operation aOperation);

src/core/thread/key_manager.cpp

@@ -292,4 +292,18 @@ void KeyManager::HandleKeyRotationTimer(void)
     }
 }
 
+void KeyManager::GenerateNonce(const Mac::ExtAddress &aAddress,
+                               uint32_t               aFrameCounter,
+                               uint8_t                aSecurityLevel,
+                               uint8_t *              aNonce)
+{
+    memcpy(aNonce, aAddress.m8, sizeof(Mac::ExtAddress));
+    aNonce += sizeof(Mac::ExtAddress);
+
+    Encoding::BigEndian::WriteUint32(aFrameCounter, aNonce);
+    aNonce += sizeof(uint32_t);
+
+    aNonce[0] = aSecurityLevel;
+}
+
 } // namespace ot

src/core/thread/key_manager.hpp

@@ -43,6 +43,7 @@
 #include "common/locator.hpp"
 #include "common/timer.hpp"
 #include "crypto/hmac_sha256.hpp"
+#include "mac/mac_frame.hpp"
 
 namespace ot {
 
@@ -61,6 +62,7 @@ public:
     enum
     {
         kMaxKeyLength = 16,
+        kNonceSize    = 13, ///< Size of IEEE 802.15.4 Nonce (bytes).
     };
 
     /**
@@ -338,6 +340,20 @@ public:
      */
     void SetSecurityPolicyFlags(uint8_t aSecurityPolicyFlags);
 
+    /**
+     * This static method generates IEEE 802.15.4 nonce byte sequence.
+     *
+     * @param[in]  aAddress        An extended address.
+     * @param[in]  aFrameCounter   A frame counter.
+     * @param[in]  aSecurityLevel  A security level.
+     * @param[out] aNonce          A buffer (with `kNonceSize` bytes) to place the generated nonce.
+     *
+     */
+    static void GenerateNonce(const Mac::ExtAddress &aAddress,
+                              uint32_t               aFrameCounter,
+                              uint8_t                aSecurityLevel,
+                              uint8_t *              aNonce);
+
 private:
     enum
     {

src/core/thread/mle.cpp

@@ -1083,26 +1083,6 @@ exit:
     return error;
 }
 
-void Mle::GenerateNonce(const Mac::ExtAddress &aMacAddr,
-                        uint32_t               aFrameCounter,
-                        uint8_t                aSecurityLevel,
-                        uint8_t *              aNonce)
-{
-    // source address
-    memcpy(aNonce, aMacAddr.m8, sizeof(aMacAddr));
-    aNonce += sizeof(aMacAddr);
-
-    // frame counter
-    aNonce[0] = (aFrameCounter >> 24) & 0xff;
-    aNonce[1] = (aFrameCounter >> 16) & 0xff;
-    aNonce[2] = (aFrameCounter >> 8) & 0xff;
-    aNonce[3] = aFrameCounter & 0xff;
-    aNonce += 4;
-
-    // security level
-    aNonce[0] = aSecurityLevel;
-}
-
 Message *Mle::NewMleMessage(void)
 {
     Message *         message;
@@ -2513,7 +2493,7 @@ otError Mle::SendMessage(Message &aMessage, const Ip6::Address &aDestination)
     otError          error = OT_ERROR_NONE;
     Header           header;
     uint32_t         keySequence;
-    uint8_t          nonce[13];
+    uint8_t          nonce[KeyManager::kNonceSize];
     uint8_t          tag[4];
     uint8_t          tagLength;
     Crypto::AesCcm   aesCcm;
@@ -2532,8 +2512,8 @@ otError Mle::SendMessage(Message &aMessage, const Ip6::Address &aDestination)
 
         aMessage.Write(0, header.GetLength(), &header);
 
-        GenerateNonce(Get<Mac::Mac>().GetExtAddress(), Get<KeyManager>().GetMleFrameCounter(), Mac::Frame::kSecEncMic32,
+        KeyManager::GenerateNonce(Get<Mac::Mac>().GetExtAddress(), Get<KeyManager>().GetMleFrameCounter(),
-                      nonce);
+                                  Mac::Frame::kSecEncMic32, nonce);
 
         aesCcm.SetKey(Get<KeyManager>().GetCurrentMleKey(), 16);
         error = aesCcm.Init(16 + 16 + header.GetHeaderLength(), aMessage.GetLength() - (header.GetLength() - 1),
@@ -2616,7 +2596,7 @@ void Mle::HandleUdpReceive(Message &aMessage, const Ip6::MessageInfo &aMessageIn
     const uint8_t * mleKey;
     uint32_t        frameCounter;
     uint8_t         messageTag[4];
-    uint8_t         nonce[13];
+    uint8_t         nonce[KeyManager::kNonceSize];
     Mac::ExtAddress macAddr;
     Crypto::AesCcm  aesCcm;
     uint16_t        mleOffset;
@@ -2675,7 +2655,7 @@ void Mle::HandleUdpReceive(Message &aMessage, const Ip6::MessageInfo &aMessageIn
 
     aMessageInfo.GetPeerAddr().ToExtAddress(macAddr);
     frameCounter = header.GetFrameCounter();
-    GenerateNonce(macAddr, frameCounter, Mac::Frame::kSecEncMic32, nonce);
+    KeyManager::GenerateNonce(macAddr, frameCounter, Mac::Frame::kSecEncMic32, nonce);
 
     aesCcm.SetKey(mleKey, 16);
     SuccessOrExit(

src/core/thread/mle.hpp

@@ -1688,11 +1688,6 @@ private:
         kDataRequestActive, ///< Data Request has been sent, Data Response is expected.
     };
 
-    void GenerateNonce(const Mac::ExtAddress &aMacAddr,
-                       uint32_t               aFrameCounter,
-                       uint8_t                aSecurityLevel,
-                       uint8_t *              aNonce);
-
     static void HandleStateChanged(Notifier::Callback &aCallback, otChangedFlags aFlags);
     void        HandleStateChanged(otChangedFlags aFlags);
     static void HandleAttachTimer(Timer &aTimer);