/*

 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>

 *

 * 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.

 */

#include "inner.h"

static inline size_t

block_size(const br_hash_class *dig)

{

  unsigned ls;

  ls = (unsigned)(dig->desc >> BR_HASHDESC_LBLEN_OFF)

    & BR_HASHDESC_LBLEN_MASK;

  return (size_t)1 << ls;

}

static void

process_key(const br_hash_class **hc, void *ks,

  const void *key, size_t key_len, unsigned bb)

{

  unsigned char tmp[256];

  size_t blen, u;

  blen = block_size(*hc);

  memcpy(tmp, key, key_len);

  for (u = 0; u < key_len; u ++) {

    tmp[u] ^= (unsigned char)bb;

  }

  memset(tmp + key_len, bb, blen - key_len);

  (*hc)->init(hc);

  (*hc)->update(hc, tmp, blen);

  (*hc)->state(hc, ks);

}

/* see bearssl.h */

void

br_hmac_key_init(br_hmac_key_context *kc,

  const br_hash_class *dig, const void *key, size_t key_len)

{

  br_hash_compat_context hc;

  unsigned char kbuf[64];

  kc->dig_vtable = dig;

  hc.vtable = dig;

  if (key_len > block_size(dig)) {

    dig->init(&hc.vtable);

    dig->update(&hc.vtable, key, key_len);

    dig->out(&hc.vtable, kbuf);

    key = kbuf;

    key_len = br_digest_size(dig);

  }

  process_key(&hc.vtable, kc->ksi, key, key_len, 0x36);

  process_key(&hc.vtable, kc->kso, key, key_len, 0x5C);

}

/* see bearssl.h */

void

br_hmac_init(br_hmac_context *ctx,

  const br_hmac_key_context *kc, size_t out_len)

{

  const br_hash_class *dig;

  size_t blen, hlen;

  dig = kc->dig_vtable;

  blen = block_size(dig);

  dig->init(&ctx->dig.vtable);

  dig->set_state(&ctx->dig.vtable, kc->ksi, (uint64_t)blen);

  memcpy(ctx->kso, kc->kso, sizeof kc->kso);

  hlen = br_digest_size(dig);

  if (out_len > 0 && out_len < hlen) {

    hlen = out_len;

  }

  ctx->out_len = hlen;

}

/* see bearssl.h */

void

br_hmac_update(br_hmac_context *ctx, const void *data, size_t len)

{

  ctx->dig.vtable->update(&ctx->dig.vtable, data, len);

}

/* see bearssl.h */

size_t

br_hmac_out(const br_hmac_context *ctx, void *out)

{

  const br_hash_class *dig;

  br_hash_compat_context hc;

  unsigned char tmp[64];

  size_t blen, hlen;

  dig = ctx->dig.vtable;

  dig->out(&ctx->dig.vtable, tmp);

  blen = block_size(dig);

  dig->init(&hc.vtable);

  dig->set_state(&hc.vtable, ctx->kso, (uint64_t)blen);

  hlen = br_digest_size(dig);

  dig->update(&hc.vtable, tmp, hlen);

  dig->out(&hc.vtable, tmp);

  memcpy(out, tmp, ctx->out_len);

  return ctx->out_len;

}