text: /*
   * 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;
  }
  