/*-
   * Copyright 2005 Colin Percival
   * Copyright 2013 Christian Mehlis & René Kijewski
   * Copyright 2016 Martin Landsmann <martin.landsmann@haw-hamburg.de>
   * 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 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
   *
   * $FreeBSD: src/lib/libmd/sha256c.c,v 1.2 2006/01/17 15:35:56 phk Exp $
   */
  
  /**
   * @ingroup     sys_hashes
   * @{
   *
   * @file
   * @brief       SHA256 hash function implementation
   *
   * @author      Colin Percival
   * @author      Christian Mehlis
   * @author      Rene Kijewski
   * @author      Martin Landsmann
   *
   * @}
   */
  
  #include <string.h>
  #include <assert.h>
  
  #include "hashes/sha256.h"
  #include "board.h"
  
  #ifdef __BIG_ENDIAN__
  /* Copy a vector of big-endian uint32_t into a vector of bytes */
  #define be32enc_vect memcpy
  
  /* Copy a vector of bytes into a vector of big-endian uint32_t */
  #define be32dec_vect memcpy
  
  #else /* !__BIG_ENDIAN__ */
  
  /*
   * Encode a length len/4 vector of (uint32_t) into a length len vector of
   * (unsigned char) in big-endian form.  Assumes len is a multiple of 4.
   */
  static void be32enc_vect(void *dst_, const void *src_, size_t len)
  {
      if ((uintptr_t)dst_ % sizeof(uint32_t) == 0 &&
          (uintptr_t)src_ % sizeof(uint32_t) == 0) {
          uint32_t *dst = dst_;
          const uint32_t *src = src_;
          for (size_t i = 0; i < len / 4; i++) {
              dst[i] = __builtin_bswap32(src[i]);
          }
      }
      else {
          uint8_t *dst = dst_;
          const uint8_t *src = src_;
          for (size_t i = 0; i < len; i += 4) {
              dst[i] = src[i + 3];
              dst[i + 1] = src[i + 2];
              dst[i + 2] = src[i + 1];
              dst[i + 3] = src[i];
          }
      }
  }
  
  /*
   * Decode a big-endian length len vector of (unsigned char) into a length
   * len/4 vector of (uint32_t).  Assumes len is a multiple of 4.
   */
  #define be32dec_vect be32enc_vect
  
  #endif /* __BYTE_ORDER__ != __ORDER_BIG_ENDIAN__ */
  
  /* Elementary functions used by SHA256 */
  #define Ch(x, y, z) ((x & (y ^ z)) ^ z)
  #define Maj(x, y, z)    ((x & (y | z)) | (y & z))
  #define SHR(x, n)   (x >> n)
  #define ROTR(x, n)  ((x >> n) | (x << (32 - n)))
  #define S0(x)       (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
  #define S1(x)       (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
  #define s0(x)       (ROTR(x, 7) ^ ROTR(x, 18) ^ SHR(x, 3))
  #define s1(x)       (ROTR(x, 17) ^ ROTR(x, 19) ^ SHR(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,
  };
  
  /*
   * SHA256 block compression function.  The 256-bit state is transformed via
   * the 512-bit input block to produce a new state.
   */
  static void sha256_transform(uint32_t *state, const unsigned char block[64])
  {
      uint32_t W[64];
      uint32_t S[8];
  
      /* 1. Prepare message schedule W. */
      be32dec_vect(W, block, 64);
      for (int i = 16; i < 64; i++) {
          W[i] = s1(W[i - 2]) + W[i - 7] + s0(W[i - 15]) + W[i - 16];
      }
  
      /* 2. Initialize working variables. */
      memcpy(S, state, 32);
  
      /* 3. Mix. */
      for (int i = 0; i < 64; ++i) {
          uint32_t e = S[(68 - i) % 8], f = S[(69 - i) % 8];
          uint32_t g = S[(70 - i) % 8], h = S[(71 - i) % 8];
          uint32_t t0 = h + S1(e) + Ch(e, f, g) + W[i] + K[i];
  
          uint32_t a = S[(64 - i) % 8], b = S[(65 - i) % 8];
          uint32_t c = S[(66 - i) % 8], d = S[(67 - i) % 8];
          uint32_t t1 = S0(a) + Maj(a, b, c);
  
          S[(67 - i) % 8] = d + t0;
          S[(71 - i) % 8] = t0 + t1;
      }
  
      /* 4. Mix local working variables into global state */
      for (int i = 0; i < 8; i++) {
          state[i] += S[i];
      }
  }
  
  static unsigned char PAD[64] = {
      0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  };
  
  /* Add padding and terminating bit-count. */
  static void sha256_pad(sha256_context_t *ctx)
  {
      /*
       * Convert length to a vector of bytes -- we do this now rather
       * than later because the length will change after we pad.
       */
      unsigned char len[8];
  
      be32enc_vect(len, ctx->count, 8);
  
      /* Add 1--64 bytes so that the resulting length is 56 mod 64 */
      uint32_t r = (ctx->count[1] >> 3) & 0x3f;
      uint32_t plen = (r < 56) ? (56 - r) : (120 - r);
      sha256_update(ctx, PAD, (size_t) plen);
  
      /* Add the terminating bit-count */
      sha256_update(ctx, len, 8);
  }
  
  /* SHA-256 initialization.  Begins a SHA-256 operation. */
  void sha256_init(sha256_context_t *ctx)
  {
      /* Zero bits processed so far */
      ctx->count[0] = ctx->count[1] = 0;
  
      /* Magic initialization constants */
      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;
  }
  
  /* Add bytes into the hash */
  void sha256_update(sha256_context_t *ctx, const void *data, size_t len)
  {
      /* Number of bytes left in the buffer from previous updates */
      uint32_t r = (ctx->count[1] >> 3) & 0x3f;
  
      /* Convert the length into a number of bits */
      uint32_t bitlen1 = ((uint32_t) len) << 3;
      uint32_t bitlen0 = ((uint32_t) len) >> 29;
  
      /* Update number of bits */
      if ((ctx->count[1] += bitlen1) < bitlen1) {
          ctx->count[0]++;
      }
  
      ctx->count[0] += bitlen0;
  
      /* Handle the case where we don't need to perform any transforms */
      if (len < 64 - r) {
          memcpy(&ctx->buf[r], data, len);
          return;
      }
  
      /* Finish the current block */
      const unsigned char *src = data;
  
      memcpy(&ctx->buf[r], src, 64 - r);
      sha256_transform(ctx->state, ctx->buf);
      src += 64 - r;
      len -= 64 - r;
  
      /* Perform complete blocks */
      while (len >= 64) {
          sha256_transform(ctx->state, src);
          src += 64;
          len -= 64;
      }
  
      /* Copy left over data into buffer */
      memcpy(ctx->buf, src, len);
  }
  
  /*
   * SHA-256 finalization.  Pads the input data, exports the hash value,
   * and clears the context state.
   */
  void sha256_final(sha256_context_t *ctx, void *dst)
  {
      /* Add padding */
      sha256_pad(ctx);
  
      /* Write the hash */
      be32enc_vect(dst, ctx->state, 32);
  
      /* Clear the context state */
      memset((void *) ctx, 0, sizeof(*ctx));
  }
  
  void *sha256(const void *data, size_t len, void *digest)
  {
      sha256_context_t c;
      static unsigned char m[SHA256_DIGEST_LENGTH];
  
      if (digest == NULL) {
          digest = m;
      }
  
      sha256_init(&c);
      sha256_update(&c, data, len);
      sha256_final(&c, digest);
  
      return digest;
  }
  
  const void *hmac_sha256(const void *key, size_t key_length,
                          const void *data, size_t len, void *digest)
  {
      unsigned char k[SHA256_INTERNAL_BLOCK_SIZE];
  
      memset((void *)k, 0x00, SHA256_INTERNAL_BLOCK_SIZE);
  
      if (key_length > SHA256_INTERNAL_BLOCK_SIZE) {
          sha256(key, key_length, k);
      }
      else {
          memcpy((void *)k, key, key_length);
      }
  
      /*
       * create the inner and outer keypads
       * rising hamming distance enforcing i_* and o_* are distinct
       * in at least one bit
       */
      unsigned char o_key_pad[SHA256_INTERNAL_BLOCK_SIZE];
      unsigned char i_key_pad[SHA256_INTERNAL_BLOCK_SIZE];
  
      for (size_t i = 0; i < SHA256_INTERNAL_BLOCK_SIZE; ++i) {
          o_key_pad[i] = 0x5c ^ k[i];
          i_key_pad[i] = 0x36 ^ k[i];
      }
  
      /*
       * Create the inner hash
       * tmp = hash(i_key_pad CONCAT message)
       */
      sha256_context_t c;
      unsigned char tmp[SHA256_DIGEST_LENGTH];
  
      sha256_init(&c);
      sha256_update(&c, i_key_pad, SHA256_INTERNAL_BLOCK_SIZE);
      sha256_update(&c, data, len);
      sha256_final(&c, tmp);
  
      static unsigned char m[SHA256_DIGEST_LENGTH];
  
      if (digest == NULL) {
          digest = m;
      }
  
      /*
       * Create the outer hash
       * result = hash(o_key_pad CONCAT tmp)
       */
      sha256_init(&c);
      sha256_update(&c, o_key_pad, SHA256_INTERNAL_BLOCK_SIZE);
      sha256_update(&c, tmp, SHA256_DIGEST_LENGTH);
      sha256_final(&c, digest);
  
      return digest;
  }
  
  /**
   * @brief helper to compute sha256 inplace for the given buffer
   *
   * @param[in, out] element the buffer to compute a sha256 and store it back to it
   *
   */
  static inline void sha256_inplace(unsigned char element[SHA256_DIGEST_LENGTH])
  {
      sha256_context_t ctx;
  
      sha256_init(&ctx);
      sha256_update(&ctx, element, SHA256_DIGEST_LENGTH);
      sha256_final(&ctx, element);
  }
  
  void *sha256_chain(const void *seed, size_t seed_length,
                     size_t elements, void *tail_element)
  {
      unsigned char tmp_element[SHA256_DIGEST_LENGTH];
  
      /* assert if no sha256-chain can be created */
      assert(elements >= 2);
  
      /* 1st iteration */
      sha256(seed, seed_length, tmp_element);
  
      /* perform consecutive iterations minus the first one */
      for (size_t i = 0; i < (elements - 1); ++i) {
          sha256_inplace(tmp_element);
      }
  
      /* store the result */
      memcpy(tail_element, tmp_element, SHA256_DIGEST_LENGTH);
  
      return tail_element;
  }
  
  void *sha256_chain_with_waypoints(const void *seed,
                                    size_t seed_length,
                                    size_t elements,
                                    void *tail_element,
                                    sha256_chain_idx_elm_t *waypoints,
                                    size_t *waypoints_length)
  {
      /* assert if no sha256-chain can be created */
      assert(elements >= 2);
  
      /* assert to prevent division by 0 */
      assert(*waypoints_length > 0);
  
      /* assert if no waypoints can be created */
      assert(*waypoints_length > 1);
  
      /* if we have enough space we store the whole chain */
      if (*waypoints_length >= elements) {
          /* 1st iteration */
          sha256(seed, seed_length, waypoints[0].element);
          waypoints[0].index = 0;
  
          /* perform consecutive iterations starting at index 1*/
          for (size_t i = 1; i < elements; ++i) {
              sha256_context_t ctx;
              sha256_init(&ctx);
              sha256_update(&ctx, waypoints[(i - 1)].element, SHA256_DIGEST_LENGTH);
              sha256_final(&ctx, waypoints[i].element);
              waypoints[i].index = i;
          }
  
          /* store the result */
          memcpy(tail_element, waypoints[(elements - 1)].element, SHA256_DIGEST_LENGTH);
          *waypoints_length = (elements - 1);
  
          return tail_element;
      }
      else {
          unsigned char tmp_element[SHA256_DIGEST_LENGTH];
          size_t waypoint_streak = (elements / *waypoints_length);
  
          /* 1st waypoint iteration */
          sha256(seed, seed_length, tmp_element);
          for (size_t i = 1; i < waypoint_streak; ++i) {
              sha256_inplace(tmp_element);
          }
          memcpy(waypoints[0].element, tmp_element, SHA256_DIGEST_LENGTH);
          waypoints[0].index = (waypoint_streak - 1);
  
          /* index of the current computed element in the chain */
          size_t index = (waypoint_streak - 1);
  
          /* consecutive waypoint iterations */
          size_t j = 1;
          for (; j < *waypoints_length; ++j) {
              for (size_t i = 0; i < waypoint_streak; ++i) {
                  sha256_inplace(tmp_element);
                  index++;
              }
              memcpy(waypoints[j].element, tmp_element, SHA256_DIGEST_LENGTH);
              waypoints[j].index = index;
          }
  
          /* store/pass the last used index in the waypoint array */
          *waypoints_length = (j - 1);
  
          /* remaining iterations down to elements */
          for (size_t i = index; i < (elements - 1); ++i) {
              sha256_inplace(tmp_element);
          }
  
          /* store the result */
          memcpy(tail_element, tmp_element, SHA256_DIGEST_LENGTH);
  
          return tail_element;
      }
  }
  
  int sha256_chain_verify_element(void *element,
                                  size_t element_index,
                                  void *tail_element,
                                  size_t chain_length)
  {
      unsigned char tmp_element[SHA256_DIGEST_LENGTH];
  
      int delta_count = (chain_length - element_index);
  
      /* assert if we have an index mismatch */
      assert(delta_count >= 1);
  
      memcpy((void *)tmp_element, element, SHA256_DIGEST_LENGTH);
  
      /* perform all consecutive iterations down to tail_element */
      for (int i = 0; i < (delta_count - 1); ++i) {
          sha256_inplace(tmp_element);
      }
  
      /* return if the computed element equals the tail_element */
      return (memcmp(tmp_element, tail_element, SHA256_DIGEST_LENGTH) != 0);
  }