[spinel] use local variables to export mac key before sending over SP…

…INEL (openthread#9536)

In RadioSpinel::SetMacKey we try to reuse the otMacKey passed to
export the literal key from PSA to be sent over SPINEL to RCP. But as
the passed param is const, we cant really use this. Better option is
to extract it into a local buffer and use that to pass the keys to
RCP.

src/lib/spinel/radio_spinel.cpp

@@ -884,35 +884,43 @@ otError RadioSpinel::SetMacKey(uint8_t                 aKeyIdMode,
                                const otMacKeyMaterial *aCurrKey,
                                const otMacKeyMaterial *aNextKey)
 {
-    otError error;
-    size_t  aKeySize;
+    otError  error;
+    size_t   aKeySize;
+    otMacKey prevKey;
+    otMacKey currKey;
+    otMacKey nextKey;
 
     VerifyOrExit((aPrevKey != nullptr) && (aCurrKey != nullptr) && (aNextKey != nullptr), error = kErrorInvalidArgs);
 
 #if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
-    SuccessOrExit(error = otPlatCryptoExportKey(aPrevKey->mKeyMaterial.mKeyRef, aPrevKey->mKeyMaterial.mKey.m8,
-                                                sizeof(aPrevKey->mKeyMaterial.mKey.m8), &aKeySize));
-    SuccessOrExit(error = otPlatCryptoExportKey(aCurrKey->mKeyMaterial.mKeyRef, aCurrKey->mKeyMaterial.mKey.m8,
-                                                sizeof(aCurrKey->mKeyMaterial.mKey.m8), &aKeySize));
-    SuccessOrExit(error = otPlatCryptoExportKey(aNextKey->mKeyMaterial.mKeyRef, aNextKey->mKeyMaterial.mKey.m8,
-                                                sizeof(aNextKey->mKeyMaterial.mKey.m8), &aKeySize));
+    SuccessOrExit(error =
+                      otPlatCryptoExportKey(aPrevKey->mKeyMaterial.mKeyRef, prevKey.m8, OT_MAC_KEY_SIZE, &aKeySize));
+    SuccessOrExit(error =
+                      otPlatCryptoExportKey(aCurrKey->mKeyMaterial.mKeyRef, currKey.m8, OT_MAC_KEY_SIZE, &aKeySize));
+    SuccessOrExit(error =
+                      otPlatCryptoExportKey(aNextKey->mKeyMaterial.mKeyRef, nextKey.m8, OT_MAC_KEY_SIZE, &aKeySize));
 #else
     OT_UNUSED_VARIABLE(aKeySize);
+
+    prevKey = aPrevKey->mKeyMaterial.mKey;
+    currKey = aCurrKey->mKeyMaterial.mKey;
+    nextKey = aNextKey->mKeyMaterial.mKey;
 #endif
 
     SuccessOrExit(error = Set(SPINEL_PROP_RCP_MAC_KEY,
                               SPINEL_DATATYPE_UINT8_S SPINEL_DATATYPE_UINT8_S SPINEL_DATATYPE_DATA_WLEN_S
                                   SPINEL_DATATYPE_DATA_WLEN_S SPINEL_DATATYPE_DATA_WLEN_S,
-                              aKeyIdMode, aKeyId, aPrevKey->mKeyMaterial.mKey.m8, sizeof(otMacKey),
-                              aCurrKey->mKeyMaterial.mKey.m8, sizeof(otMacKey), aNextKey->mKeyMaterial.mKey.m8,
-                              sizeof(otMacKey)));
+                              aKeyIdMode, aKeyId, prevKey.m8, OT_MAC_KEY_SIZE, currKey.m8, OT_MAC_KEY_SIZE, nextKey.m8,
+                              OT_MAC_KEY_SIZE));
 
 #if OPENTHREAD_SPINEL_CONFIG_RCP_RESTORATION_MAX_COUNT > 0
     mKeyIdMode = aKeyIdMode;
     mKeyId     = aKeyId;
-    memcpy(mPrevKey.m8, aPrevKey->mKeyMaterial.mKey.m8, OT_MAC_KEY_SIZE);
-    memcpy(mCurrKey.m8, aCurrKey->mKeyMaterial.mKey.m8, OT_MAC_KEY_SIZE);
-    memcpy(mNextKey.m8, aNextKey->mKeyMaterial.mKey.m8, OT_MAC_KEY_SIZE);
+
+    mPrevKey = prevKey;
+    mCurrKey = currKey;
+    mNextKey = nextKey;
+
     mMacKeySet = true;
 #endif