MAXREFDES143#: DeepCover Embedded Security in IoT Authenticated Sensing & Notification

Dependencies:   MaximInterface mbed

The MAXREFDES143# is an Internet of Things (IoT) embedded security reference design, built to protect an industrial sensing node by means of authentication and notification to a web server. The hardware includes a peripheral module representing a protected sensor node monitoring operating temperature and remaining life of a filter (simulated through ambient light sensing) and an mbed shield representing a controller node responsible for monitoring one or more sensor nodes. The design is hierarchical with each controller node communicating data from connected sensor nodes to a web server that maintains a centralized log and dispatches notifications as necessary. The mbed shield contains a Wi-Fi module, a DS2465 coprocessor with 1-Wire® master function, an LCD, LEDs, and pushbuttons. The protected sensor node contains a DS28E15 authenticator, a DS7505 temperature sensor, and a MAX44009 light sensor. The mbed shield communicates to a web server by the onboard Wi-Fi module and to the protected sensor node with I2C and 1-Wire. The MAXREFDES143# is equipped with a standard shield connector for immediate testing using an mbed board such as the MAX32600MBED#. The simplicity of this design enables rapid integration into any star-topology IoT network requiring the heightened security with low overhead provided by the SHA-256 symmetric-key algorithm.

More information about the MAXREFDES143# is available on the Maxim Integrated website.

ESP8266.cpp

Committer:
IanBenzMaxim
Date:
19 months ago
Revision:
35:3d414ba9ab6c
Parent:
32:0a09505a656d

File content as of revision 35:3d414ba9ab6c:

/*******************************************************************************
* Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* Except as contained in this notice, the name of Maxim Integrated
* Products, Inc. shall not be used except as stated in the Maxim Integrated
* Products, Inc. Branding Policy.
*
* The mere transfer of this software does not imply any licenses
* of trade secrets, proprietary technology, copyrights, patents,
* trademarks, maskwork rights, or any other form of intellectual
* property whatsoever. Maxim Integrated Products, Inc. retains all
* ownership rights.
*******************************************************************************/

#include <cstdlib>
#include <Timer.h>
#include <wait_api.h>
#include "ESP8266.hpp"

static inline void disableRecvData() { __disable_irq(); }

static inline void enableRecvData() { __enable_irq(); }

ESP8266::ESP8266(const PinName tx, const PinName rx, const PinName rst,
                 const PinName CH_PD, const int baud,
                 mbed::Serial * debugMsgIntf)
    : AT_intf(tx, rx), resetPin(rst), powerDownPin(CH_PD),
      debugMsg(debugMsgIntf), parseRecvReset(false) {
  AT_intf.baud(baud);
  AT_intf.attach(this, &ESP8266::recv_AT_data_cb);

  // Ensure that device is not held in reset
  if (resetPin.is_connected())
    resetPin = 1;
  // Power down device at startup due to high current demand
  setPowered(false);
}

void ESP8266::reset() {
  if (resetPin.is_connected()) {
    resetPin = 0;
    wait_ms(100);
    resetPin = 1;
    wait_ms(1000);
  }
}

bool ESP8266::powered() const {
  bool isPowered;
  if (powerDownPin.is_connected()) {
    isPowered = powerDownPin.read();
  } else {
    isPowered = false;
  }
  return isPowered;
}

void ESP8266::setPowered(bool powered) {
  if (powerDownPin.is_connected())
    powerDownPin = powered;
}

ESP8266::CmdResult ESP8266::performSelfTest() {
  return sendCommand(CmdBuilder(""));
}

ESP8266::CmdResult ESP8266::setCurrentWifiMode(const ESP8266::WifiMode mode) {
  CmdBuilder builder("CWMODE_CUR");
  builder.addRawArgument(mode);
  return sendCommand(builder);
}

ESP8266::CmdResult ESP8266::joinCurrentAccessPoint(const std::string & ssid,
                                                   const std::string & pwd,
                                                   const std::string & bssid) {
  CmdBuilder builder("CWJAP_CUR");
  builder.addStringArgument(ssid);
  builder.addStringArgument(pwd);
  if (bssid != "")
    builder.addStringArgument(bssid);
  return sendCommand(builder);
}

ESP8266::CmdResult ESP8266::quitAccessPoint() {
  return sendCommand(CmdBuilder("CWQAP"));
}

ESP8266::CmdResult ESP8266::setMaxRFTXPower(const float power_dBm) {
  int power_arg = (int)(power_dBm * 4);
  if (power_arg > 82)
    power_arg = 82;
  else if (power_arg < 0)
    power_arg = 0;

  CmdBuilder builder("RFPOWER");
  builder.addRawArgument(power_arg);
  return sendCommand(builder);
}

ESP8266::CmdResult ESP8266::ping(const std::string & IP) {
  CmdBuilder builder("PING");
  builder.addStringArgument(IP);
  return sendCommand(builder);
}

ESP8266::CmdResult ESP8266::openConnection(const ESP8266::ConnType type,
                                           const std::string & remoteIP,
                                           const unsigned int remotePort) {
  CmdBuilder builder("CIPSTART");
  builder.addStringArgument((type == TCP) ? "TCP" : "UDP");
  builder.addStringArgument(remoteIP);
  builder.addRawArgument(remotePort);
  return sendCommand(builder);
}

ESP8266::CmdResult ESP8266::closeConnection() {
  return sendCommand(CmdBuilder("CIPCLOSE"));
}

ESP8266::CmdResult ESP8266::sendData(const std::string & data) {
  CmdBuilder builder("CIPSEND");
  builder.addRawArgument(data.length());
  ESP8266::CmdResult result = sendCommand(builder);
  if (result == ESP8266::AT_OK)
    result = send_AT_data(data, false);
  return result;
}

ESP8266::CmdResult ESP8266::sendCommand(const CmdBuilder & cmd) {
  return send_AT_data(cmd.str(), true);
}

bool ESP8266::recvIpDataReadable() {
  bool result;

  disableRecvData(); // Lock queue access

  result = !recvIpDataBuffer.empty();

  enableRecvData(); // Unlock queue access

  return result;
}

char ESP8266::getcRecvIpData() {
  char received;

  disableRecvData(); // Lock queue access

  // Pop next char or set to NTC if not data in buffer
  if (!recvIpDataBuffer.pop(received))
    received = '\0';

  enableRecvData(); // Unlock queue access

  return received;
}

void ESP8266::clearRecvData() {
  disableRecvData(); // Lock queue access

  recvIpDataBuffer.reset();
  parseRecvReset = true;

  enableRecvData(); // Unlock queue access
}

ESP8266::CmdResult ESP8266::send_AT_data(const std::string & cmdString,
                                         const bool expectEcho) {
  const int timeout_ms = 10000;

  mbed::Timer timer;
  ESP8266::CmdResult result = ESP8266::HardwareError;
  std::string response;

  disableRecvData(); // Lock for manual data handling in this procedure

  // Flush receive buffer
  while (AT_intf.readable())
    AT_intf.getc();

  // Begin counting for timeout
  timer.start();

  for (size_t i = 0; i < cmdString.length(); i++) {
    // Write next character
    while (!AT_intf.writeable()) {
      if (timer.read_ms() > timeout_ms) {
        result = TimeoutError;
        goto exit;
      }
    }
    AT_intf.putc(cmdString[i]);
    // Wait for echo
    if (expectEcho && (cmdString[i] != '\r') && (cmdString[i] != '\n')) {
      while (!AT_intf.readable()) {
        if (timer.read_ms() > timeout_ms) {
          result = TimeoutError;
          goto exit;
        }
      }
      // Compare to written character
      if (AT_intf.getc() != cmdString[i]) {
        // Handle error
        result = ESP8266::HardwareError;
        goto exit;
      }
    }
  }

  while (result == ESP8266::HardwareError) {
    // Wait to receive something
    response.clear();
    while (!read_line(response))
      ;

    // Check if valid response
    if (response == "OK")
      result = ESP8266::AT_OK;
    else if (response == "FAIL")
      result = ESP8266::AT_FAIL;
    else if (response == "ERROR")
      result = ESP8266::AT_ERROR;
    else if (response == "SEND OK") // Used by AT+CIPSEND
      result = ESP8266::AT_OK;
    else if (response == "ALREADY CONNECT") // Used by AT+CIPSTART
      result = ESP8266::AT_OK;

    if (timer.read_ms() > timeout_ms) {
      result = TimeoutError;
      break;
    }
  }

exit:
  enableRecvData(); // Enable interrupt processing
  return result;
}

bool ESP8266::read_line(std::string & line) {
  char received;

  while (AT_intf.readable()) {
    received = AT_intf.getc();
    if (received == '\n') {
      return true;
    } else if (received != '\r') {
      line.push_back(received);
    }
  }
  return false;
}

void ESP8266::recv_AT_data_cb() {
  while (AT_intf.readable()) {
    char received = AT_intf.getc();
    parseRecvIpData(received);
    parseRecvConnClosedMsg(received);
    parseRecvReset = false;
  }
}

void ESP8266::parseRecvIpData(const char received) {
  enum DataRecvState { Header, Length, Data, Reset };

  static const char findChars[] = "+IPD,";
  static const size_t maxSizeDigits = 4;

  static size_t dataFinishedSize = 0;
  static size_t index = 0;
  static char sizeDigits[] = {'\0', '\0', '\0', '\0', '\0'};
  static DataRecvState state = Header;

  if (parseRecvReset)
    state = Reset;

  switch (state) {
  case Reset:
  default:
    index = 0;
    dataFinishedSize = 0;
    state = Header;
    // Continue processing switch

  case Header:
    if (received == findChars[index]) {
      if (findChars[++index] == '\0') {
        index = 0;
        state = Length;
      }
    } else {
      state = Reset;
    }
    break;

  case Length:
    if ((received <= '9') && (received >= '0')) {
      if (index < maxSizeDigits) {
        sizeDigits[index++] = received;
      } else {
        state = Reset;
      }
    } else if (received == ':') {
      dataFinishedSize = std::atoi(sizeDigits);
      if (dataFinishedSize == 0) {
        state = Reset;
      } else {
        index = 0;
        state = Data;
      }
    } else {
      state = Reset;
    }
    break;

  case Data:
    if (index < dataFinishedSize) {
      recvIpDataBuffer.push(received);
      index++;
    } else {
      state = Reset;
    }
    break;
  };
}

void ESP8266::parseRecvConnClosedMsg(const char received) {
  static const char findChars[] = "CLOSED";

  static int index = 0;

  bool shouldReset = parseRecvReset;

  if (received == findChars[index]) {
    if (findChars[++index] == '\0') {
      printDbgMsg(findChars);
      shouldReset = true;
    }
  } else {
    shouldReset = true;
  }

  if (shouldReset) {
    index = 0;
  }
}

void ESP8266::printDbgMsg(const char * message) {
  if (debugMsg != NULL)
    debugMsg->printf("%s", message);
}

ESP8266::CmdBuilder::CmdBuilder(const std::string & cmd) { clear(cmd); }

void ESP8266::CmdBuilder::clear(const std::string & cmd) {
  numArgs = 0;
  cmdStream.str("");

  cmdStream << "AT";
  if (cmd != "")
    cmdStream << "+" << cmd;
}

void ESP8266::CmdBuilder::addStringArgument(const std::string & arg) {
  std::ostringstream argStream;
  argStream << "\"" << arg << "\"";
  addRawArgument<std::string>(argStream.str());
}

std::string ESP8266::CmdBuilder::str() const {
  std::string cmdString = cmdStream.str();
  cmdString.append("\r\n");
  return cmdString;
}