TOTP动态令牌

一、TOTP原理

转载：

动态令牌离线生成机制探究（2FA & TOTP）_摸鱼Script的博客-CSDN博客   著作权归作者所有，转载请注明出处。

图解TOTP:

 

 

代码实现如下：代码来源Github

地址：https://github.com/Netthaw/TOTP-MCU 著作权归作者所有，转载请注明出处。

#include "totp/totp.h"
#include "totp/sha1.h"
#include <stdio.h>
#include <string.h>
#include "base32.h"
#include "hardware/datetime.h"

uint8_t* _hmacKey;
uint32_t _timeStep;

// Init the library with the private key, its length and the timeStep duration
void TOTP(uint8_t* hmacKey, uint32_t timeStep) 
{   
    _hmacKey = hmacKey;//这个指针要指向一个不会释放的变量，否则数据每次都会丢失
    _timeStep = timeStep;
}
// Generate a code, using the timestamp provided//使用提供的时间戳生成代码
uint32_t getCodeFromTimestamp(void) 
{
    long nowTime = strTounixtime(getNowDateTime());    //获取当前时间戳
    uint32_t steps = nowTime / _timeStep;//时间戳/时间间隔
    return getCodeFromSteps(steps);//传入时间戳生成的步数，处理后返回最终6位验证码
}

// Generate a code, using the number of steps provided//使用提供的步骤数生成代码
uint32_t getCodeFromSteps(uint32_t steps) {
    // STEP 0, map the number of steps in a 8-bytes array (counter value)
    uint8_t _byteArray[8];

    _byteArray[0] = 0x00;
    _byteArray[1] = 0x00;
    _byteArray[2] = 0x00;
    _byteArray[3] = 0x00;
    _byteArray[4] = (uint8_t)((steps >> 24) & 0xFF);
    _byteArray[5] = (uint8_t)((steps >> 16) & 0xFF);
    _byteArray[6] = (uint8_t)((steps >> 8) & 0XFF);
    _byteArray[7] = (uint8_t)((steps & 0XFF));

    // STEP 1, get the HMAC-SHA1 hash from counter and key
    initHmac(_hmacKey, strlen(_hmacKey));
    writeArray(_byteArray, 8);
    uint8_t* _hash = resultHmac();

    // STEP 2, apply dynamic truncation to obtain a 4-bytes string
    uint32_t _truncatedHash = 0;
    uint8_t _offset = _hash[20 - 1] & 0xF;
    uint8_t j;
    for (j = 0; j < 4; ++j) {
        _truncatedHash <<= 8;
        _truncatedHash  |= _hash[_offset + j];
    }

    // STEP 3, compute the OTP value
    _truncatedHash &= 0x7FFFFFFF;    //Disabled
    _truncatedHash %= 1000000;
    return _truncatedHash;
}

void totpInit(void)
{
    static char hmacKey[] = "CERBERUS1";    
    TOTP(hmacKey,60);    
    // Secret key, Key length, Timestep (7200s - 2hours)
}

#ifndef TOTP_H
#define TOTP_H
#include <stdint.h>

uint32_t getCodeFromTimestamp(void);
uint32_t getCodeFromSteps(uint32_t steps);
void totpInit(void);

#endif

#include <stdio.h>
#include <string.h>
#include "totp/sha1.h"

#define SHA1_K0 0x5a827999
#define SHA1_K20 0x6ed9eba1
#define SHA1_K40 0x8f1bbcdc
#define SHA1_K60 0xca62c1d6

union _buffer {
  uint8_t b[BLOCK_LENGTH];
  uint32_t w[BLOCK_LENGTH/4];
} buffer;

union _state {
  uint8_t b[HASH_LENGTH];
  uint32_t w[HASH_LENGTH/4];
} state;

uint8_t bufferOffset;
uint32_t byteCount;
unsigned char keyBuffer[BLOCK_LENGTH];
unsigned char innerHash[HASH_LENGTH];

uint8_t sha1InitState[] = {
  0x01,0x23,0x45,0x67, // H0
  0x89,0xab,0xcd,0xef, // H1
  0xfe,0xdc,0xba,0x98, // H2
  0x76,0x54,0x32,0x10, // H3
  0xf0,0xe1,0xd2,0xc3  // H4
};

void init(void) {
  memcpy(state.b,sha1InitState,HASH_LENGTH);
  byteCount = 0;
  bufferOffset = 0;
}

uint32_t rol32(uint32_t number, uint8_t bits) {
  return ((number << bits) | (uint32_t)(number >> (32-bits)));
}

void hashBlock() {
  uint8_t i;
  uint32_t a,b,c,d,e,t;

  a=state.w[0];
  b=state.w[1];
  c=state.w[2];
  d=state.w[3];
  e=state.w[4];
  for (i=0; i<80; i++) {
    if (i>=16) {
      t = buffer.w[(i+13)&15] ^ buffer.w[(i+8)&15] ^ buffer.w[(i+2)&15] ^ buffer.w[i&15];
      buffer.w[i&15] = rol32(t,1);
    }

    if (i<20) {
      t = (d ^ (b & (c ^ d))) + SHA1_K0;
    } else if (i<40) {
      t = (b ^ c ^ d) + SHA1_K20;
    } else if (i<60) {
      t = ((b & c) | (d & (b | c))) + SHA1_K40;
    } else {
      t = (b ^ c ^ d) + SHA1_K60;
    }
    t+=rol32(a,5) + e + buffer.w[i&15];
    e=d;
    d=c;
    c=rol32(b,30);
    b=a;
    a=t;
  }
  state.w[0] += a;
  state.w[1] += b;
  state.w[2] += c;
  state.w[3] += d;
  state.w[4] += e;
}

void addUncounted(uint8_t data) {
  buffer.b[bufferOffset ^ 3] = data;
  bufferOffset++;
  if (bufferOffset == BLOCK_LENGTH) {
    hashBlock();
    bufferOffset = 0;
  }
}

static void write(uint8_t data) {
  ++byteCount;
  addUncounted(data);
  return;
}

void writeArray(uint8_t *buffer, uint8_t size){
    while (size--) {
        write(*buffer++);
    }
}

void pad() {
  // Implement SHA-1 padding (fips180-2 �˜5.1.1)
  // Pad with 0x80 followed by 0x00 until the end of the block
  addUncounted(0x80);
  while (bufferOffset != 56) addUncounted(0x00);

  // Append length in the last 8 bytes
  addUncounted(0); // We're only using 32 bit lengths
  addUncounted(0); // But SHA-1 supports 64 bit lengths
  addUncounted(0); // So zero pad the top bits
  addUncounted(byteCount >> 29); // Shifting to multiply by 8
  addUncounted(byteCount >> 21); // as SHA-1 supports bitstreams as well as
  addUncounted(byteCount >> 13); // byte.
  addUncounted(byteCount >> 5);
  addUncounted(byteCount << 3);
}

uint8_t* result(void) {
  // Pad to complete the last block
  pad();
  // Swap byte order back
  uint8_t i;
  for (i=0; i<5; i++) {
    uint32_t a,b;
    a=state.w[i];
    b=a<<24;
    b|=(a<<8) & 0x00ff0000;
    b|=(a>>8) & 0x0000ff00;
    b|=a>>24;
    state.w[i]=b;
  }
  // Return pointer to hash (20 characters)
  return state.b;
}

#define HMAC_IPAD 0x36
#define HMAC_OPAD 0x5c

void initHmac(const uint8_t* key, uint8_t keyLength) 
{
  uint8_t i;
  memset(keyBuffer,0,BLOCK_LENGTH);
  if (keyLength > BLOCK_LENGTH) {
    // Hash long keys
    init();
    for (;keyLength--;) write(*key++);
    memcpy(keyBuffer,result(),HASH_LENGTH);
  } else {
    // Block length keys are used as is
    memcpy(keyBuffer,key,keyLength);
  }
  // Start inner hash
  init();
  for (i=0; i<BLOCK_LENGTH; i++) {
    write(keyBuffer[i] ^ HMAC_IPAD);
  }
}

uint8_t* resultHmac(void) {
  uint8_t i;
  // Complete inner hash
  memcpy(innerHash,result(),HASH_LENGTH);
  // Calculate outer hash
  init();
  for (i=0; i<BLOCK_LENGTH; i++) write(keyBuffer[i] ^ HMAC_OPAD);
  for (i=0; i<HASH_LENGTH; i++) write(innerHash[i]);
  return result();
}

#ifndef SHA1_H
#define SHA1_H
#include <stdint.h>

#define HASH_LENGTH 20
#define BLOCK_LENGTH 64

void initHmac(const uint8_t* secret, uint8_t secretLength);
uint8_t* resultHmac(void);
void writeArray(uint8_t *buffer, uint8_t size);

#endif

#include "totp.h"

void main void
{
    totpInit();
    while(1)
    {
         uint32_t newCode = getCodeFromTimestamp();//4~6位数据       
         printf("222******************************newCode:%d\n",newCode);
    }        
}

TOTP动态令牌一般是设备端和服务端步骤保持一致。所以如果要想获取相同的验证码，必须保证传入哈希算法的共享密钥相同，如果有加解密，加解密方式需保持一致。时间戳同步。

博客园文件里有一个服务端代码生成的TOTP可执行文件可以验证上述代码，可以下载到电脑本地执行，该代码的密钥和上面是一致的，时间获取的是本地电脑的时间。