fix converting authorization key to hex string

[ubruhin]

Hi,

In the AuthKey raw-to-hex conversion loop, the loop variable was incremented by 2 (i += 2) which skipped every second byte in auth_key_factory. In addition, the snprintf(auth_key_hex + 2 * i, ...) wrote to index 4 in the second loop execution, while the first loop execution wrote a \0 to index 2, thus the variable auth_key_hex always contained only 2 characters (plus zero-termination). So in the end, only the first byte of auth_key_factory was stored, the rest was completely lost.

I found this because the authentication didn't work for me. Changing i += 2 to i++ fixed the problem. The same problem existed in setAuthKey(). Note that there was already a place where the conversion was correct:

MicroOcppMongoose/src/MicroOcppMongooseClient.cpp

Lines 202 to 211 in 95f4748

	#if MO_DBG_LEVEL >= MO_DL_DEBUG
	{
	char auth_key_hex [2 * MO_AUTHKEY_LEN_MAX + 1];
	auth_key_hex[0] = '\0';
	for (size_t i = 0; i < auth_key_len; i++) {
	snprintf(auth_key_hex + 2 * i, 3, "%02X", auth_key[i]);
	}
	MO_DBG_DEBUG("auth Token=%s:%s (key will be converted to non-hex)", cb_id.c_str(), auth_key_hex);
	}
	#endif //MO_DBG_LEVEL >= MO_DL_DEBUG

Just let me know if I need to adjust anything.

[matth-x]

Hi @ubruhin, thank you very much for this contribution and the great explanation!