libavformat/rtmpdigest.c

   1 /*
   2  * RTMP network protocol
   3  * Copyright (c) 2009 Konstantin Shishkov
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * RTMP protocol digest
  25  */
  26
  27 #include <stdint.h>
  28
  29 #include "libavutil/error.h"
  30 #include "libavutil/hmac.h"
  31
  32 #include "rtmp.h"
  33
  34 int ff_rtmp_calc_digest(const uint8_t *src, int len, int gap,
  35                         const uint8_t *key, int keylen, uint8_t *dst)
  36 {
  37     AVHMAC *hmac;
  38
  39     hmac = av_hmac_alloc(AV_HMAC_SHA256);
  40     if (!hmac)
  41         return AVERROR(ENOMEM);
  42
  43     av_hmac_init(hmac, key, keylen);
  44     if (gap <= 0) {
  45         av_hmac_update(hmac, src, len);
  46     } else { //skip 32 bytes used for storing digest
  47         av_hmac_update(hmac, src, gap);
  48         av_hmac_update(hmac, src + gap + 32, len - gap - 32);
  49     }
  50     av_hmac_final(hmac, dst, 32);
  51
  52     av_hmac_free(hmac);
  53
  54     return 0;
  55 }
  56
  57 int ff_rtmp_calc_digest_pos(const uint8_t *buf, int off, int mod_val,
  58                             int add_val)
  59 {
  60     int i, digest_pos = 0;
  61
  62     for (i = 0; i < 4; i++)
  63         digest_pos += buf[i + off];
  64     digest_pos = digest_pos % mod_val + add_val;
  65
  66     return digest_pos;
  67 }