/*
MIT License

Copyright (c) 2019 Weravech

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 THE
AUTHORS OR COPYRIGHT HOLDERS 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.

https://github.com/Netthaw/TOTP-MCU
*/
#include "sha1.h"

#include <string.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;
uint8_t keyBuffer[BLOCK_LENGTH];
uint8_t 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;
  }
}

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();
}