/*
   * Copyright (C) 2016 Oliver Hahm <oliver.hahm@inria.fr>
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /* This code is public-domain - it is based on libcrypt
   * placed in the public domain by Wei Dai and other contributors.
   */
  
  /**
   * @defgroup    sys_hashes_sha1 SHA-1
   * @ingroup     sys_hashes
   * @brief       Implementation of the SHA-1 hashing function
  
   * @{
   *
   * @file
   * @brief       SHA-1 interface definition
   *
   * @author      Wei Dai and others
   * @author      Oliver Hahm <oliver.hahm@inria.fr>
   */
  
  #include <stdint.h>
  #include <string.h>
  
  #include "hashes/sha1.h"
  
  #define SHA1_K0  0x5a827999
  #define SHA1_K20 0x6ed9eba1
  #define SHA1_K40 0x8f1bbcdc
  #define SHA1_K60 0xca62c1d6
  
  void sha1_init(sha1_context *ctx)
  {
      ctx->state[0] = 0x67452301;
      ctx->state[1] = 0xefcdab89;
      ctx->state[2] = 0x98badcfe;
      ctx->state[3] = 0x10325476;
      ctx->state[4] = 0xc3d2e1f0;
      ctx->byte_count = 0;
      ctx->buffer_offset = 0;
  }
  
  static uint32_t sha1_rol32(uint32_t number, uint8_t bits)
  {
      return ((number << bits) | (number >> (32 - bits)));
  }
  
  static void sha1_hash_block(sha1_context *s)
  {
      uint8_t i;
      uint32_t a, b, c, d, e, t;
  
      a = s->state[0];
      b = s->state[1];
      c = s->state[2];
      d = s->state[3];
      e = s->state[4];
      for (i = 0; i < 80; i++) {
          if (i >= 16) {
              t = s->buffer[(i + 13) & 15] ^ s->buffer[(i + 8) & 15] ^
                  s->buffer[(i + 2) & 15] ^ s->buffer[i & 15];
              s->buffer[i & 15] = sha1_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 += sha1_rol32(a, 5) + e + s->buffer[i & 15];
          e = d;
          d = c;
          c = sha1_rol32(b, 30);
          b = a;
          a = t;
      }
      s->state[0] += a;
      s->state[1] += b;
      s->state[2] += c;
      s->state[3] += d;
      s->state[4] += e;
  }
  
  static void sha1_add_uncounted(sha1_context *s, uint8_t data)
  {
      uint8_t *const b = (uint8_t *) s->buffer;
  
  #ifdef __BIG_ENDIAN__
      b[s->buffer_offset] = data;
  #else
      b[s->buffer_offset ^ 3] = data;
  #endif
      s->buffer_offset++;
      if (s->buffer_offset == SHA1_BLOCK_LENGTH) {
          sha1_hash_block(s);
          s->buffer_offset = 0;
      }
  }
  
  static void sha1_update_byte(sha1_context *ctx, uint8_t data)
  {
      ++ctx->byte_count;
      sha1_add_uncounted(ctx, data);
  }
  
  void sha1_update(sha1_context *ctx, const void *data, size_t len)
  {
      const uint8_t *d = data;
      while (len--) {
          sha1_update_byte(ctx, *(d++));
      }
  }
  
  static void sha1_pad(sha1_context *s)
  {
      /* Implement SHA-1 padding (fips180-2 §5.1.1) */
  
      /* Pad with 0x80 followed by 0x00 until the end of the block */
      sha1_add_uncounted(s, 0x80);
      while (s->buffer_offset != 56) {
          sha1_add_uncounted(s, 0x00);
      }
  
      /* Append length in the last 8 bytes */
      sha1_add_uncounted(s, 0);                   /* We're only using 32 bit lengths */
      sha1_add_uncounted(s, 0);                   /* But SHA-1 supports 64 bit lengths */
      sha1_add_uncounted(s, 0);                   /* So zero pad the top bits */
      sha1_add_uncounted(s, s->byte_count >> 29); /* Shifting to multiply by 8 */
      sha1_add_uncounted(s, s->byte_count >> 21); /* as SHA-1 supports bitstreams as well as */
      sha1_add_uncounted(s, s->byte_count >> 13); /* byte. */
      sha1_add_uncounted(s, s->byte_count >> 5);
      sha1_add_uncounted(s, s->byte_count << 3);
  }
  
  void sha1_final(sha1_context *ctx, void *digest)
  {
      /* Pad to complete the last block */
      sha1_pad(ctx);
  
      /* Swap byte order back */
      for (int i = 0; i < 5; i++) {
          ctx->state[i] =
              (((ctx->state[i]) << 24) & 0xff000000)
              | (((ctx->state[i]) << 8) & 0x00ff0000)
              | (((ctx->state[i]) >> 8) & 0x0000ff00)
              | (((ctx->state[i]) >> 24) & 0x000000ff);
      }
  
      /* Copy the content of the hash (20 characters) */
      memcpy(digest, ctx->state, 20);
  }
  
  void sha1(void *digest, const void *data, size_t len)
  {
      sha1_context ctx;
  
      sha1_init(&ctx);
      sha1_update(&ctx, (unsigned char *) data, len);
      sha1_final(&ctx, digest);
  }
  
  #define HMAC_IPAD 0x36
  #define HMAC_OPAD 0x5c
  
  void sha1_init_hmac(sha1_context *ctx, const void *key, size_t key_length)
  {
      uint8_t i;
      const uint8_t *k = key;
  
      memset(ctx->key_buffer, 0, SHA1_BLOCK_LENGTH);
      if (key_length > SHA1_BLOCK_LENGTH) {
          /* Hash long keys */
          sha1_init(ctx);
          while (key_length--) {
              sha1_update_byte(ctx, *k++);
          }
          sha1_final(ctx, ctx->key_buffer);
      }
      else {
          /* Block length keys are used as is */
          memcpy(ctx->key_buffer, key, key_length);
      }
      /* Start inner hash */
      sha1_init(ctx);
      for (i = 0; i < SHA1_BLOCK_LENGTH; i++) {
          sha1_update_byte(ctx, ctx->key_buffer[i] ^ HMAC_IPAD);
      }
  }
  
  void sha1_final_hmac(sha1_context *ctx, void *digest)
  {
      uint8_t i;
  
      /* Complete inner hash */
      sha1_final(ctx, ctx->inner_hash);
      /* Calculate outer hash */
      sha1_init(ctx);
      for (i = 0; i < SHA1_BLOCK_LENGTH; i++) {
          sha1_update_byte(ctx, ctx->key_buffer[i] ^ HMAC_OPAD);
      }
      for (i = 0; i < SHA1_DIGEST_LENGTH; i++) {
          sha1_update_byte(ctx, ctx->inner_hash[i]);
      }
  
      sha1_final(ctx, digest);
  }