[radio-spinel] simplify SetMacKey() (#9539)

This commit simplifies the `RadioSpinel::SetMacKey()` method.
A common `private` overload of `SetMacKey()` is added that uses
`const otMacKey &` as its input key type.

When `KEY_REFERENCES_ENABLE` is not enable the `SetMacKey()` simply
passes the key from the `otMacKeyMaterial` directly. This avoids the
unnecessary copying of the key into a local variable.

When `KEY_REFERENCES_ENABLE` is enabled, the keys are read from
secure storage. A new `ReadMacKey()` helper method is added which
also validates that the read key size is correct.

src/lib/spinel/radio_spinel.cpp

@@ -878,6 +878,20 @@ exit:
     return error;
 }
 
+#if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
+
+otError RadioSpinel::ReadMacKey(const otMacKeyMaterial &aKeyMaterial, otMacKey &aKey)
+{
+    size_t  keySize;
+    otError error = otPlatCryptoExportKey(aKeyMaterial.mKeyMaterial.mKeyRef, aKey.m8, sizeof(aKey), &keySize);
+
+    SuccessOrExit(error);
+    VerifyOrExit(keySize == sizeof(otMacKey), error = OT_ERROR_FAILED);
+
+exit:
+    return error;
+}
+
 otError RadioSpinel::SetMacKey(uint8_t                 aKeyIdMode,
                                uint8_t                 aKeyId,
                                const otMacKeyMaterial *aPrevKey,
@@ -885,41 +899,54 @@ otError RadioSpinel::SetMacKey(uint8_t                 aKeyIdMode,
                                const otMacKeyMaterial *aNextKey)
 {
     otError  error;
-    size_t   aKeySize;
     otMacKey prevKey;
     otMacKey currKey;
     otMacKey nextKey;
 
-    VerifyOrExit((aPrevKey != nullptr) && (aCurrKey != nullptr) && (aNextKey != nullptr), error = kErrorInvalidArgs);
+    SuccessOrExit(error = ReadMacKey(*aPrevKey, prevKey));
+    SuccessOrExit(error = ReadMacKey(*aCurrKey, currKey));
+    SuccessOrExit(error = ReadMacKey(*aNextKey, nextKey));
+    error = SetMacKey(aKeyIdMode, aKeyId, prevKey, currKey, nextKey);
+
+exit:
+    return error;
+}
 
-#if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
-    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
+otError RadioSpinel::SetMacKey(uint8_t                 aKeyIdMode,
+                               uint8_t                 aKeyId,
+                               const otMacKeyMaterial *aPrevKey,
+                               const otMacKeyMaterial *aCurrKey,
+                               const otMacKeyMaterial *aNextKey)
+{
+    return SetMacKey(aKeyIdMode, aKeyId, aPrevKey->mKeyMaterial.mKey, aCurrKey->mKeyMaterial.mKey,
+                     aNextKey->mKeyMaterial.mKey);
+}
+
+#endif // OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
+
+otError RadioSpinel::SetMacKey(uint8_t         aKeyIdMode,
+                               uint8_t         aKeyId,
+                               const otMacKey &aPrevKey,
+                               const otMacKey &aCurrKey,
+                               const otMacKey &aNextKey)
+{
+    otError error;
 
     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, prevKey.m8, OT_MAC_KEY_SIZE, currKey.m8, OT_MAC_KEY_SIZE, nextKey.m8,
-                              OT_MAC_KEY_SIZE));
+                              aKeyIdMode, aKeyId, aPrevKey.m8, sizeof(aPrevKey), aCurrKey.m8, sizeof(aCurrKey),
+                              aNextKey.m8, sizeof(aNextKey)));
 
 #if OPENTHREAD_SPINEL_CONFIG_RCP_RESTORATION_MAX_COUNT > 0
     mKeyIdMode = aKeyIdMode;
     mKeyId     = aKeyId;
 
-    mPrevKey = prevKey;
-    mCurrKey = currKey;
-    mNextKey = nextKey;
+    mPrevKey = aPrevKey;
+    mCurrKey = aCurrKey;
+    mNextKey = aNextKey;
 
     mMacKeySet = true;
 #endif

src/lib/spinel/radio_spinel.hpp

@@ -1011,6 +1011,15 @@ private:
         mRadioSpinelMetrics.mSpinelParseErrorCount += (aError == OT_ERROR_PARSE) ? 1 : 0;
     }
 
+    otError SetMacKey(uint8_t         aKeyIdMode,
+                      uint8_t         aKeyId,
+                      const otMacKey &aPrevKey,
+                      const otMacKey &aCurrKey,
+                      const otMacKey &NextKey);
+#if OPENTHREAD_CONFIG_PLATFORM_KEY_REFERENCES_ENABLE
+    static otError ReadMacKey(const otMacKeyMaterial &aKeyMaterial, otMacKey &aKey);
+#endif
+
     static void LogIfFail(const char *aText, otError aError);
 
     static void LogCrit(const char *aFormat, ...) OT_TOOL_PRINTF_STYLE_FORMAT_ARG_CHECK(1, 2);