[Silabs]Add a static assert to ensure there is no out of bound write (p…

…roject-chip#31268)

* Add a static assert to ensure there is no out of bound write

* address comments

src/platform/silabs/BLEManagerImpl.h

@@ -143,7 +143,6 @@ class BLEManagerImpl final : public BLEManager, private BleLayer, private BlePla
     static BLEManagerImpl sInstance;
 
     // ===== Private members reserved for use by this class only.
-
     enum class Flags : uint16_t
     {
         kAdvertisingEnabled     = 0x0001,
@@ -161,6 +160,10 @@ class BLEManagerImpl final : public BLEManager, private BleLayer, private BlePla
         kUnusedIndex         = 0xFF,
     };
 
+    static constexpr uint8_t kFlagTlvSize       = 3; // 1 byte for length, 1b for type and 1b for the Flag value
+    static constexpr uint8_t kUUIDTlvSize       = 4; // 1 byte for length, 1b for type and 2b for the UUID value
+    static constexpr uint8_t kDeviceNameTlvSize = (2 + kMaxDeviceNameLength); // 1 byte for length, 1b for type and + device name
+
     struct CHIPoBLEConState
     {
 #if !(SLI_SI91X_ENABLE_BLE || RSI_BLE_ENABLE)

src/platform/silabs/efr32/BLEManagerImpl.cpp

@@ -444,6 +444,7 @@ CHIP_ERROR BLEManagerImpl::ConfigureAdvertisingData(void)
 
     mDeviceNameLength = strlen(mDeviceName); // Device Name length + length field
     VerifyOrExit(mDeviceNameLength < kMaxDeviceNameLength, err = CHIP_ERROR_INVALID_ARGUMENT);
+    static_assert((kUUIDTlvSize + kDeviceNameTlvSize) <= MAX_RESPONSE_DATA_LEN, "Scan Response buffer is too small");
 
     mDeviceIdInfoLength = sizeof(mDeviceIdInfo); // Servicedatalen + length+ UUID (Short)
     static_assert(sizeof(mDeviceIdInfo) + CHIP_ADV_SHORT_UUID_LEN + 1 <= UINT8_MAX, "Our length won't fit in a uint8_t");

src/platform/silabs/rs911x/BLEManagerImpl.cpp

@@ -563,6 +563,7 @@ CHIP_ERROR BLEManagerImpl::ConfigureAdvertisingData(void)
 
     mDeviceNameLength = strlen(mDeviceName); // Device Name length + length field
     VerifyOrExit(mDeviceNameLength < kMaxDeviceNameLength, err = CHIP_ERROR_INVALID_ARGUMENT);
+    static_assert((kFlagTlvSize + kUUIDTlvSize + kDeviceNameTlvSize) <= MAX_RESPONSE_DATA_LEN, "Scan Response buffer is too small");
 
     mDeviceIdInfoLength = sizeof(mDeviceIdInfo); // Servicedatalen + length+ UUID (Short)
     static_assert(sizeof(mDeviceIdInfo) + CHIP_ADV_SHORT_UUID_LEN + 1 <= UINT8_MAX, "Our length won't fit in a uint8_t");