text: /* sha256.c - TinyCrypt SHA-256 crypto hash algorithm implementation */
  
  /*
   *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions are met:
   *
   *    - Redistributions of source code must retain the above copyright notice,
   *     this list of conditions and the following disclaimer.
   *
   *    - Redistributions in binary form 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.
   *
   *    - Neither the name of Intel Corporation nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 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 "../include/tinycrypt/sha256.h"
  #include "../include/tinycrypt/constants.h"
  #include "../include/tinycrypt/utils.h"
  
  static void compress(unsigned int *iv, const uint8_t *data);
  
  int tc_sha256_init(TCSha256State_t s)
  {
  	/* input sanity check: */
  	if (s == (TCSha256State_t) 0) {
  		return TC_CRYPTO_FAIL;
  	}
  
  	/*
  	 * Setting the initial state values.
  	 * These values correspond to the first 32 bits of the fractional parts
  	 * of the square roots of the first 8 primes: 2, 3, 5, 7, 11, 13, 17
  	 * and 19.
  	 */
  	_set((uint8_t *) s, 0x00, sizeof(*s));
  	s->iv[0] = 0x6a09e667;
  	s->iv[1] = 0xbb67ae85;
  	s->iv[2] = 0x3c6ef372;
  	s->iv[3] = 0xa54ff53a;
  	s->iv[4] = 0x510e527f;
  	s->iv[5] = 0x9b05688c;
  	s->iv[6] = 0x1f83d9ab;
  	s->iv[7] = 0x5be0cd19;
  
  	return TC_CRYPTO_SUCCESS;
  }
  
  int tc_sha256_update(TCSha256State_t s, const uint8_t *data, size_t datalen)
  {
  	/* input sanity check: */
  	if (s == (TCSha256State_t) 0 ||
  	    data == (void *) 0) {
  		return TC_CRYPTO_FAIL;
  	} else if (datalen == 0) {
  		return TC_CRYPTO_SUCCESS;
  	}
  
  	while (datalen-- > 0) {
  		s->leftover[s->leftover_offset++] = *(data++);
  		if (s->leftover_offset >= TC_SHA256_BLOCK_SIZE) {
  			compress(s->iv, s->leftover);
  			s->leftover_offset = 0;
  			s->bits_hashed += (TC_SHA256_BLOCK_SIZE << 3);
  		}
  	}
  
  	return TC_CRYPTO_SUCCESS;
  }
  
  int tc_sha256_final(uint8_t *digest, TCSha256State_t s)
  {
  	unsigned int i;
  
  	/* input sanity check: */
  	if (digest == (uint8_t *) 0 ||
  	    s == (TCSha256State_t) 0) {
  		return TC_CRYPTO_FAIL;
  	}
  
  	s->bits_hashed += (s->leftover_offset << 3);
  
  	s->leftover[s->leftover_offset++] = 0x80; /* always room for one byte */
  	if (s->leftover_offset > (sizeof(s->leftover) - 8)) {
  		/* there is not room for all the padding in this block */
  		_set(s->leftover + s->leftover_offset, 0x00,
  		     sizeof(s->leftover) - s->leftover_offset);
  		compress(s->iv, s->leftover);
  		s->leftover_offset = 0;
  	}
  
  	/* add the padding and the length in big-Endian format */
  	_set(s->leftover + s->leftover_offset, 0x00,
  	     sizeof(s->leftover) - 8 - s->leftover_offset);
  	s->leftover[sizeof(s->leftover) - 1] = (uint8_t)(s->bits_hashed);
  	s->leftover[sizeof(s->leftover) - 2] = (uint8_t)(s->bits_hashed >> 8);
  	s->leftover[sizeof(s->leftover) - 3] = (uint8_t)(s->bits_hashed >> 16);
  	s->leftover[sizeof(s->leftover) - 4] = (uint8_t)(s->bits_hashed >> 24);
  	s->leftover[sizeof(s->leftover) - 5] = (uint8_t)(s->bits_hashed >> 32);
  	s->leftover[sizeof(s->leftover) - 6] = (uint8_t)(s->bits_hashed >> 40);
  	s->leftover[sizeof(s->leftover) - 7] = (uint8_t)(s->bits_hashed >> 48);
  	s->leftover[sizeof(s->leftover) - 8] = (uint8_t)(s->bits_hashed >> 56);
  
  	/* hash the padding and length */
  	compress(s->iv, s->leftover);
  
  	/* copy the iv out to digest */
  	for (i = 0; i < TC_SHA256_STATE_BLOCKS; ++i) {
  		unsigned int t = *((unsigned int *) &s->iv[i]);
  		*digest++ = (uint8_t)(t >> 24);
  		*digest++ = (uint8_t)(t >> 16);
  		*digest++ = (uint8_t)(t >> 8);
  		*digest++ = (uint8_t)(t);
  	}
  
  	/* destroy the current state */
  	_set(s, 0, sizeof(*s));
  
  	return TC_CRYPTO_SUCCESS;
  }
  
  /*
   * Initializing SHA-256 Hash constant words K.
   * These values correspond to the first 32 bits of the fractional parts of the
   * cube roots of the first 64 primes between 2 and 311.
   */
  static const unsigned int k256[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
  };
  
  static inline unsigned int ROTR(unsigned int a, unsigned int n)
  {
  	return (((a) >> n) | ((a) << (32 - n)));
  }
  
  #define Sigma0(a)(ROTR((a), 2) ^ ROTR((a), 13) ^ ROTR((a), 22))
  #define Sigma1(a)(ROTR((a), 6) ^ ROTR((a), 11) ^ ROTR((a), 25))
  #define sigma0(a)(ROTR((a), 7) ^ ROTR((a), 18) ^ ((a) >> 3))
  #define sigma1(a)(ROTR((a), 17) ^ ROTR((a), 19) ^ ((a) >> 10))
  
  #define Ch(a, b, c)(((a) & (b)) ^ ((~(a)) & (c)))
  #define Maj(a, b, c)(((a) & (b)) ^ ((a) & (c)) ^ ((b) & (c)))
  
  static inline unsigned int BigEndian(const uint8_t **c)
  {
  	unsigned int n = 0;
  
  	n = (((unsigned int)(*((*c)++))) << 24);
  	n |= ((unsigned int)(*((*c)++)) << 16);
  	n |= ((unsigned int)(*((*c)++)) << 8);
  	n |= ((unsigned int)(*((*c)++)));
  	return n;
  }
  
  static void compress(unsigned int *iv, const uint8_t *data)
  {
  	unsigned int a, b, c, d, e, f, g, h;
  	unsigned int s0, s1;
  	unsigned int t1, t2;
  	unsigned int work_space[16];
  	unsigned int n;
  	unsigned int i;
  
  	a = iv[0]; b = iv[1]; c = iv[2]; d = iv[3];
  	e = iv[4]; f = iv[5]; g = iv[6]; h = iv[7];
  
  	for (i = 0; i < 16; ++i) {
  		n = BigEndian(&data);
  		t1 = work_space[i] = n;
  		t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
  		t2 = Sigma0(a) + Maj(a, b, c);
  		h = g; g = f; f = e; e = d + t1;
  		d = c; c = b; b = a; a = t1 + t2;
  	}
  
  	for ( ; i < 64; ++i) {
  		s0 = work_space[(i+1)&0x0f];
  		s0 = sigma0(s0);
  		s1 = work_space[(i+14)&0x0f];
  		s1 = sigma1(s1);
  
  		t1 = work_space[i&0xf] += s0 + s1 + work_space[(i+9)&0xf];
  		t1 += h + Sigma1(e) + Ch(e, f, g) + k256[i];
  		t2 = Sigma0(a) + Maj(a, b, c);
  		h = g; g = f; f = e; e = d + t1;
  		d = c; c = b; b = a; a = t1 + t2;
  	}
  
  	iv[0] += a; iv[1] += b; iv[2] += c; iv[3] += d;
  	iv[4] += e; iv[5] += f; iv[6] += g; iv[7] += h;
  }
  