proto_commands.cpp

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/// @file proto_commands.cpp
/// @brief Command builders for the IO-Homecontrol protocol.
 
#include "proto_commands.h"
 
#include "proto_crypto.h"
 
#include <cstring>
 
namespace esphome {
namespace home_io_control {
 
namespace {
 
// === Command payload templates ===
 
/// The protocol uses 0-100 for percentage-style position inputs before encoding them on wire.
constexpr uint8_t POSITION_PERCENT_MAX = 100;
/// Byte 0 in execute-family payloads identifies a user-originated remote action.
constexpr uint8_t EXECUTE_USER_ORIGINATOR = 0x01;
/// ACEI/profile byte observed on normal execute commands.
constexpr uint8_t EXECUTE_POSITION_ACEI = 0x67;
/// Standard payload length for full execute-family commands.
constexpr size_t EXECUTE_PAYLOAD_SIZE = 8;
/// Bit flag that marks the standard position payload layout after the encoded position byte.
constexpr uint8_t EXECUTE_POSITION_LAYOUT_FLAG = 0x80;
/// Controller-capture matched helper byte used in normal execute payloads.
constexpr uint8_t EXECUTE_POSITION_PROFILE = 0x06;
/// ACEI/profile byte observed on tilt execute commands.
constexpr uint8_t EXECUTE_TILT_ACEI = 0xE7;
/// Short payload length for special execute commands such as stop/favorite.
constexpr size_t EXECUTE_SPECIAL_PAYLOAD_SIZE = 6;
/// Private sub-command for position status requests.
constexpr uint8_t PRIVATE_GET_POSITION_STATUS = 0x03;
/// Status-update acknowledgement payload matched from controller traffic.
constexpr uint8_t STATUS_UPDATE_ACK_PAYLOAD[] = {0x05, 0x00};
/// Set-config payload that enables automatic status updates from the device.
constexpr uint8_t SET_CONFIG1_STATUS_BROADCAST_PAYLOAD[] = {0xE0, 0x10, 0x0A, 0x08, 0x00};
 
}  // namespace
 
/// Build an execute command (0x00) to control a device.
/// For real positions (0-100), the value is doubled in the frame (0x00=0%, 0xC8=100%).
/// For special commands (stop/favorite), a shorter 6-byte payload is used.
bool create_execute(IoFrame &f, const uint8_t *own, const uint8_t *dst, bool low_power, uint8_t position) {
  init_frame(f, true, true, false, low_power);
  set_dst(f, dst);
  set_src(f, own);
  if (position <= POSITION_PERCENT_MAX) {
    // Real position: doubled value (0-200 maps to 0-100%).
    const uint8_t payload[EXECUTE_PAYLOAD_SIZE] = {
        EXECUTE_USER_ORIGINATOR,      EXECUTE_POSITION_ACEI, static_cast<uint8_t>(2 * position), 0x00,
        EXECUTE_POSITION_LAYOUT_FLAG, POS_FAVORITE,          EXECUTE_POSITION_PROFILE,           0x00};
    return set_cmd(f, CMD_EXECUTE, payload, sizeof(payload));
  }
 
  // Special command (stop=0xD2, favorite=0xD8).
  const uint8_t payload[EXECUTE_SPECIAL_PAYLOAD_SIZE] = {
      EXECUTE_USER_ORIGINATOR, EXECUTE_POSITION_ACEI, position, 0x00, 0x00, 0x00};
  return set_cmd(f, CMD_EXECUTE, payload, sizeof(payload));
}
 
/// Build a get-status request (0x03). The device responds with its current position.
bool create_get_status(IoFrame &f, const uint8_t *own, const uint8_t *dst) {
  // low_power=true for solar devices.
  init_frame(f, true, true, false, true);
  set_dst(f, dst);
  set_src(f, own);
  // Private sub-command = get position status.
  uint8_t d[3] = {PRIVATE_GET_POSITION_STATUS, 0x00, 0x00};
  return set_cmd(f, CMD_PRIVATE, d, sizeof(d));
}
 
/// Build a tilt execute command (0x00) for devices that support slat angle control.
bool create_execute_tilt(IoFrame &f, const uint8_t *own, const uint8_t *dst, bool low_power, uint8_t tilt_percent) {
  init_frame(f, true, true, false, low_power);
  set_dst(f, dst);
  set_src(f, own);
 
  auto const tilt_value =
      static_cast<uint16_t>((POSITION_PERCENT_MAX - tilt_percent) * STATUS_POS_MAX / POSITION_PERCENT_MAX);
  uint8_t d[EXECUTE_PAYLOAD_SIZE] = {EXECUTE_USER_ORIGINATOR,
                                     EXECUTE_TILT_ACEI,
                                     POS_UNKNOWN,
                                     0x00,
                                     STATUS_TILT_SELECTOR,
                                     static_cast<uint8_t>(tilt_value >> BITS_PER_BYTE),
                                     static_cast<uint8_t>(tilt_value),
                                     0x00};
  return set_cmd(f, CMD_EXECUTE, d, sizeof(d));
}
 
/// Build a tilt-aware get-status request (0x03) that returns the extended 16-byte tilt payload.
bool create_get_status_tilt(IoFrame &f, const uint8_t *own, const uint8_t *dst) {
  init_frame(f, true, true, false, true);
  set_dst(f, dst);
  set_src(f, own);
  // The selector byte switches the private status response to the extended tilt layout.
  uint8_t d[4] = {PRIVATE_GET_POSITION_STATUS, STATUS_TILT_SELECTOR, 0x01, 0x00};
  return set_cmd(f, CMD_PRIVATE, d, sizeof(d));
}
 
/// Build a discovery broadcast (0x28). Sent to the broadcast address 0x00003B.
/// Only devices in pairing mode (PROG button pressed) will respond.
bool create_discover(IoFrame &f, const uint8_t *own) {
  // start+end: single broadcast frame.
  init_frame(f, true, true, true, false);
  set_dst(f, BROADCAST_DISCOVER);
  set_src(f, own);
  return set_cmd(f, CMD_DISCOVER_REQ);
}
 
/// Build a key-init request (0x31) to start the pairing key exchange with a discovered device.
bool create_key_init(IoFrame &f, const uint8_t *own, const uint8_t *dst) {
  init_frame(f, true, true, false, true);
  set_dst(f, dst);
  set_src(f, own);
  return set_cmd(f, CMD_KEY_INIT);
}
 
/// Build a key-transfer frame (0x32) containing the system key encrypted with the transfer key.
bool create_key_transfer(IoFrame &f, IoFrame &old_frame, const uint8_t *dst, const uint8_t *src,
                         const uint8_t key[AES_KEY_SIZE], const uint8_t challenge[HMAC_SIZE]) {
  init_frame(f, true, false, false, false);
  set_dst(f, dst);
  set_src(f, src);
  // The pairing capture we matched derives the IV from the previous command byte only. Treating
  // the key-init frame that narrowly keeps our key transfer aligned with real controllers.
  uint8_t enc_key[AES_KEY_SIZE];
  if (!crypto::crypt_key(&old_frame.cmd, 1, challenge, key, enc_key))
    return false;
  return set_cmd(f, CMD_KEY_TRANSFER, enc_key, AES_KEY_SIZE);
}
 
/// Build a challenge request (0x3C) containing 6 random bytes.
/// Used when WE need to authenticate an incoming request from a device.
bool create_challenge_req(IoFrame &f, const uint8_t *dst, const uint8_t *src) {
  init_frame(f, true, true, false, false);  // start=true, end=false
  set_dst(f, dst);
  set_src(f, src);
  uint8_t challenge[HMAC_SIZE];
  crypto::generate_challenge(challenge);
  return set_cmd(f, CMD_CHALLENGE_REQ, challenge, HMAC_SIZE);
}
 
/// Build a challenge response (0x3D) proving we know the system key.
/// The HMAC is computed over [original_command_id + original_data] using the challenge.
bool create_challenge_resp(IoFrame &f, const uint8_t *dst, const uint8_t *src, const uint8_t challenge[HMAC_SIZE],
                           const IoFrame &origin, const uint8_t *key) {
  init_frame(f);
  set_dst(f, dst);
  set_src(f, src);
  // The authenticated transcript covers the original request, not the 0x3D wrapper. Using the
  // origin command byte and payload here was one of the key interoperability findings.
  uint8_t frame_data[FRAME_MAX_SIZE];
  frame_data[0] = origin.cmd;
  memcpy(frame_data + 1, origin.data, origin.data_len);
  uint8_t hmac[HMAC_SIZE];
  if (!crypto::create_hmac(frame_data, origin.data_len + 1, challenge, key, hmac))
    return false;
  return set_cmd(f, CMD_CHALLENGE_RESP, hmac, HMAC_SIZE);
}
 
/// Build a status-update acknowledgment (0x72). Sent after authenticating a device's status update.
/// The response is sent on all 3 channels to ensure the device receives it.
bool create_status_update_resp(IoFrame &f, const uint8_t *own, const uint8_t *dst) {
  // end=true: final frame.
  init_frame(f, true, false, true, false);
  set_dst(f, dst);
  set_src(f, own);
  // Status update acknowledgment payload matched from working controller captures.
  return set_cmd(f, CMD_STATUS_UPDATE_RESP, STATUS_UPDATE_ACK_PAYLOAD, sizeof(STATUS_UPDATE_ACK_PAYLOAD));
}
 
/// Build a set-config command (0x6F) to tell the device to automatically send status updates
/// when controlled by any remote (not just us). Not all devices support this.
bool create_set_config1(IoFrame &f, const uint8_t *own, const uint8_t *dst) {
  init_frame(f, true, true, false, false);
  set_dst(f, dst);
  set_src(f, own);
  // Set-config payload matched from working controller captures.
  return set_cmd(f, CMD_SET_CONFIG1, SET_CONFIG1_STATUS_BROADCAST_PAYLOAD,
                 sizeof(SET_CONFIG1_STATUS_BROADCAST_PAYLOAD));
}
 
}  // namespace home_io_control
}  // namespace esphome