lib/crypto/hmacsha256.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Interface header:    HMAC SHA-256 code
   5
   6    Copyright (C) Andrew Tridgell 2008
   7
   8    based in hmacsha1.c which is:
   9      Copyright (C) Stefan Metzmacher
  10
  11    This program is free software; you can redistribute it and/or modify
  12    it under the terms of the GNU General Public License as published by
  13    the Free Software Foundation; either version 3 of the License, or
  14    (at your option) any later version.
  15
  16    This program is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19    GNU General Public License for more details.
  20
  21    You should have received a copy of the GNU General Public License
  22    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  23 */
  24
  25 /*
  26  taken direct from rfc2202 implementation and modified for suitable use
  27  */
  28
  29 #include "includes.h"
  30 #include "../lib/crypto/crypto.h"
  31
  32 /***********************************************************************
  33  the rfc 2104/2202 version of hmac_sha256 initialisation.
  34 ***********************************************************************/
  35 _PUBLIC_ void hmac_sha256_init(const uint8_t *key, size_t key_len, struct HMACSHA256Context *ctx)
  36 {
  37         int i;
  38         uint8_t tk[SHA256_DIGEST_LENGTH];
  39
  40         /* if key is longer than 64 bytes reset it to key=HASH(key) */
  41         if (key_len > 64)
  42         {
  43                 SHA256_CTX tctx;
  44
  45                 SHA256_Init(&tctx);
  46                 SHA256_Update(&tctx, key, key_len);
  47                 SHA256_Final(tk, &tctx);
  48
  49                 key = tk;
  50                 key_len = SHA256_DIGEST_LENGTH;
  51         }
  52
  53         /* start out by storing key in pads */
  54         ZERO_STRUCT(ctx->k_ipad);
  55         ZERO_STRUCT(ctx->k_opad);
  56         memcpy( ctx->k_ipad, key, key_len);
  57         memcpy( ctx->k_opad, key, key_len);
  58
  59         /* XOR key with ipad and opad values */
  60         for (i=0; i<64; i++)
  61         {
  62                 ctx->k_ipad[i] ^= 0x36;
  63                 ctx->k_opad[i] ^= 0x5c;
  64         }
  65
  66         SHA256_Init(&ctx->ctx);
  67         SHA256_Update(&ctx->ctx, ctx->k_ipad, 64);
  68 }
  69
  70 /***********************************************************************
  71  update hmac_sha256 "inner" buffer
  72 ***********************************************************************/
  73 _PUBLIC_ void hmac_sha256_update(const uint8_t *data, size_t data_len, struct HMACSHA256Context *ctx)
  74 {
  75         SHA256_Update(&ctx->ctx, data, data_len); /* then text of datagram */
  76 }
  77
  78 /***********************************************************************
  79  finish off hmac_sha256 "inner" buffer and generate outer one.
  80 ***********************************************************************/
  81 _PUBLIC_ void hmac_sha256_final(uint8_t digest[SHA256_DIGEST_LENGTH], struct HMACSHA256Context *ctx)
  82 {
  83         SHA256_CTX ctx_o;
  84
  85         SHA256_Final(digest, &ctx->ctx);
  86
  87         SHA256_Init(&ctx_o);
  88         SHA256_Update(&ctx_o, ctx->k_opad, 64);
  89         SHA256_Update(&ctx_o, digest, SHA256_DIGEST_LENGTH);
  90         SHA256_Final(digest, &ctx_o);
  91 }