Not possible to send 255 bytes of data by loraWAN

[Maddocrus]

Describe the bug

The data is not fully AES encrypted.

https://github.com/mcci-catena/arduino-lmic/blob/master/src/aes/lmic.c

Line: 248

u4_t os_aes (u1_t mode, xref2u1_t buf, u2_t len) {

        aesroundkeys();

        if( mode & AES_MICNOAUX ) {
            AESAUX[0] = AESAUX[1] = AESAUX[2] = AESAUX[3] = 0;
        } else {
            AESAUX[0] = swapmsbf(AESAUX[0]);
            AESAUX[1] = swapmsbf(AESAUX[1]);
            AESAUX[2] = swapmsbf(AESAUX[2]);
            AESAUX[3] = swapmsbf(AESAUX[3]);
        }

        while( (signed char)len > 0 ) {  <------- Problem is here
...

It turns out of range "len" is larger "(signed char)" then we get a value with a minus sign and encryption is ignored.
If i set len = 250 it turns to -6 and i have no encryption.

Environment

• Version of LMIC being used - 5.+
• Version of Arduino IDE being used - 2+
• Network provider - ChirpStack
• Region - EU868
• Board - Heltec
• CPU - ESP32
• Radio - SX1262

To Reproduce

Send a data packet larger than 127 bytes.

Expected behavior

It is expected that the 255 byte will be encrypted.

Screenshots

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Additional context

Add any other context about the problem here.

[Maddocrus]

I tried to fix it like this

u4_t os_aes (u1_t mode, xref2u1_t buf, u2_t data_len) {
int32_t len = data_len; // This works up to 241 bytes.

but I started getting an error here
https://github.com/mcci-catena/arduino-lmic/blob/master/src/lmic/radio_sx126x.c
Line: 803

// Chapter 14.2: Circuit configuration for basic tx operation
static void txlora(void) {
    // Send configuration commands to radio
    radio_config();
    setPacketType(PACKET_TYPE_LORA);
    setRfFrequency();
    setTxParams();

    writeBuffer(0x00, LMIC.frame, LMIC.dataLen); ---> next code block

https://github.com/mcci-catena/arduino-lmic/blob/master/src/lmic/radio_sx126x.c
Line: 277

// Write `len` bytes from `buf` to the FIFO buffer starting at buffer address `addr`
static void writeBuffer(u1_t addr, xref2u1_t buf, u1_t len) {
    // Set the TX buffer base address. Leave RX base address as 0
    u1_t baseAddr[SX126X_BUFF_BASE_ADDR_LEN] = {addr, 0};
    lmic_hal_spi_write(SetBufferBaseAddress, &addr, SX126X_BUFF_BASE_ADDR_LEN);

    // Prepend the offset byte to the data being written to the buffer
    u1_t new_buf[len + 1];
    new_buf[0] = SX126X_FIFO_OFFSET;
    for (u1_t i = 1; i < (len + 1); i++) { <--- problem here, the condition is impossible if "len == 255", infinity loop
        new_buf[i] = buf[i - 1];
    }

    lmic_hal_spi_write(WriteBuffer, new_buf, len + 1);
}