text: /**
   * Copyright (c) 2015 - 2017, Nordic Semiconductor ASA
   * 
   * All rights reserved.
   * 
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   * 
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   * 
   * 2. Redistributions in binary form, except as embedded into a Nordic
   *    Semiconductor ASA integrated circuit in a product or a software update for
   *    such product, must reproduce the above copyright notice, this list of
   *    conditions and the following disclaimer in the documentation and/or other
   *    materials provided with the distribution.
   * 
   * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
   *    contributors may be used to endorse or promote products derived from this
   *    software without specific prior written permission.
   * 
   * 4. This software, with or without modification, must only be used with a
   *    Nordic Semiconductor ASA integrated circuit.
   * 
   * 5. Any software provided in binary form under this license must not be reverse
   *    engineered, decompiled, modified and/or disassembled.
   * 
   * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
   * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
   * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   * 
   */
  #include <stdlib.h>
  #include "sha256.h"
  #include "sdk_errors.h"
  #include "sdk_common.h"
  
  
  #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
  #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32 - (b))))
  
  #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
  #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
  #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
  #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
  #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
  #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))
  
  
  static const uint32_t k[64] = {
      0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
      0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
      0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
      0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
      0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
      0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
      0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
      0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
  };
  
  
  /**@brief Function for calculating the hash of a 64-byte section of data.
   *
   * @param[in,out] ctx   Hash instance.
   * @param[in]     data  Aray with data to be hashed. Assumed to be 64 bytes long.
   */
  void sha256_transform(sha256_context_t *ctx, const uint8_t * data)
  {
      uint32_t a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
  
      for (i = 0, j = 0; i < 16; ++i, j += 4)
          m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
      for ( ; i < 64; ++i)
          m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
  
      a = ctx->state[0];
      b = ctx->state[1];
      c = ctx->state[2];
      d = ctx->state[3];
      e = ctx->state[4];
      f = ctx->state[5];
      g = ctx->state[6];
      h = ctx->state[7];
  
      for (i = 0; i < 64; ++i) {
          t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
          t2 = EP0(a) + MAJ(a,b,c);
          h = g;
          g = f;
          f = e;
          e = d + t1;
          d = c;
          c = b;
          b = a;
          a = t1 + t2;
      }
  
      ctx->state[0] += a;
      ctx->state[1] += b;
      ctx->state[2] += c;
      ctx->state[3] += d;
      ctx->state[4] += e;
      ctx->state[5] += f;
      ctx->state[6] += g;
      ctx->state[7] += h;
  }
  
  
  ret_code_t sha256_init(sha256_context_t *ctx)
  {
      VERIFY_PARAM_NOT_NULL(ctx);
  
      ctx->datalen = 0;
      ctx->bitlen = 0;
      ctx->state[0] = 0x6a09e667;
      ctx->state[1] = 0xbb67ae85;
      ctx->state[2] = 0x3c6ef372;
      ctx->state[3] = 0xa54ff53a;
      ctx->state[4] = 0x510e527f;
      ctx->state[5] = 0x9b05688c;
      ctx->state[6] = 0x1f83d9ab;
      ctx->state[7] = 0x5be0cd19;
  
      return NRF_SUCCESS;
  }
  
  
  ret_code_t sha256_update(sha256_context_t *ctx, const uint8_t * data, size_t len)
  {
      VERIFY_PARAM_NOT_NULL(ctx);
      if (((len > 0) && (data == NULL)))
      {
          return NRF_ERROR_NULL;
      }
  
      uint32_t i;
  
      for (i = 0; i < len; ++i) {
          ctx->data[ctx->datalen] = data[i];
          ctx->datalen++;
          if (ctx->datalen == 64) {
              sha256_transform(ctx, ctx->data);
              ctx->bitlen += 512;
              ctx->datalen = 0;
          }
      }
  
      return NRF_SUCCESS;
  }
  
  
  ret_code_t sha256_final(sha256_context_t *ctx, uint8_t * hash, uint8_t le)
  {
      uint32_t i;
  
      VERIFY_PARAM_NOT_NULL(ctx);
      VERIFY_PARAM_NOT_NULL(hash);
  
      i = ctx->datalen;
  
      // Pad whatever data is left in the buffer.
      if (ctx->datalen < 56) {
          ctx->data[i++] = 0x80;
          while (i < 56)
              ctx->data[i++] = 0x00;
      }
      else {
          ctx->data[i++] = 0x80;
          while (i < 64)
              ctx->data[i++] = 0x00;
          sha256_transform(ctx, ctx->data);
          memset(ctx->data, 0, 56);
      }
  
      // Append to the padding the total message's length in bits and transform.
      ctx->bitlen += (uint64_t)ctx->datalen * 8;
      ctx->data[63] = ctx->bitlen;
      ctx->data[62] = ctx->bitlen >> 8;
      ctx->data[61] = ctx->bitlen >> 16;
      ctx->data[60] = ctx->bitlen >> 24;
      ctx->data[59] = ctx->bitlen >> 32;
      ctx->data[58] = ctx->bitlen >> 40;
      ctx->data[57] = ctx->bitlen >> 48;
      ctx->data[56] = ctx->bitlen >> 56;
      sha256_transform(ctx, ctx->data);
  
      if(le)
      {
          for (i = 0; i < 4; ++i) {
              hash[i]      = (ctx->state[7] >> (i * 8)) & 0x000000ff;
              hash[i + 4]  = (ctx->state[6] >> (i * 8)) & 0x000000ff;
              hash[i + 8]  = (ctx->state[5] >> (i * 8)) & 0x000000ff;
              hash[i + 12] = (ctx->state[4] >> (i * 8)) & 0x000000ff;
              hash[i + 16] = (ctx->state[3] >> (i * 8)) & 0x000000ff;
              hash[i + 20] = (ctx->state[2] >> (i * 8)) & 0x000000ff;
              hash[i + 24] = (ctx->state[1] >> (i * 8)) & 0x000000ff;
              hash[i + 28] = (ctx->state[0] >> (i * 8)) & 0x000000ff;
          }
      }
      else
      {
  
          // Since this implementation uses little endian uint8_t ordering and SHA uses big endian,
          // reverse all the uint8_ts when copying the final state to the output hash.
          for (i = 0; i < 4; ++i) {
              hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
              hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
          }
      }
  
      return NRF_SUCCESS;
  }
  