LCOV - code coverage report
Current view: top level - libavutil - tea.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 49 49 100.0 %
Date: 2017-12-14 19:11:59 Functions: 4 4 100.0 %

          Line data    Source code
       1             : /*
       2             :  * A 32-bit implementation of the TEA algorithm
       3             :  * Copyright (c) 2015 Vesselin Bontchev
       4             :  *
       5             :  * Loosely based on the implementation of David Wheeler and Roger Needham,
       6             :  * https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm#Reference_code
       7             :  *
       8             :  * This file is part of FFmpeg.
       9             :  *
      10             :  * FFmpeg is free software; you can redistribute it and/or
      11             :  * modify it under the terms of the GNU Lesser General Public
      12             :  * License as published by the Free Software Foundation; either
      13             :  * version 2.1 of the License, or (at your option) any later version.
      14             :  *
      15             :  * FFmpeg is distributed in the hope that it will be useful,
      16             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      17             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      18             :  * Lesser General Public License for more details.
      19             :  *
      20             :  * You should have received a copy of the GNU Lesser General Public
      21             :  * License along with FFmpeg; if not, write to the Free Software
      22             :  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
      23             :  */
      24             : 
      25             : #include "avutil.h"
      26             : #include "common.h"
      27             : #include "intreadwrite.h"
      28             : #include "tea.h"
      29             : 
      30             : typedef struct AVTEA {
      31             :     uint32_t key[16];
      32             :     int rounds;
      33             : } AVTEA;
      34             : 
      35           1 : struct AVTEA *av_tea_alloc(void)
      36             : {
      37           1 :     return av_mallocz(sizeof(struct AVTEA));
      38             : }
      39             : 
      40             : const int av_tea_size = sizeof(AVTEA);
      41             : 
      42           4 : void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
      43             : {
      44             :     int i;
      45             : 
      46          20 :     for (i = 0; i < 4; i++)
      47          16 :         ctx->key[i] = AV_RB32(key + (i << 2));
      48             : 
      49           4 :     ctx->rounds = rounds;
      50           4 : }
      51             : 
      52          56 : static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
      53             :                           int decrypt, uint8_t *iv)
      54             : {
      55             :     uint32_t v0, v1;
      56          56 :     int rounds = ctx->rounds;
      57             :     uint32_t k0, k1, k2, k3;
      58          56 :     k0 = ctx->key[0];
      59          56 :     k1 = ctx->key[1];
      60          56 :     k2 = ctx->key[2];
      61          56 :     k3 = ctx->key[3];
      62             : 
      63          56 :     v0 = AV_RB32(src);
      64          56 :     v1 = AV_RB32(src + 4);
      65             : 
      66          56 :     if (decrypt) {
      67             :         int i;
      68          36 :         uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2);
      69             : 
      70        1188 :         for (i = 0; i < rounds / 2; i++) {
      71        1152 :             v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
      72        1152 :             v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
      73        1152 :             sum -= delta;
      74             :         }
      75          36 :         if (iv) {
      76          32 :             v0 ^= AV_RB32(iv);
      77          32 :             v1 ^= AV_RB32(iv + 4);
      78          32 :             memcpy(iv, src, 8);
      79             :         }
      80             :     } else {
      81             :         int i;
      82          20 :         uint32_t sum = 0, delta = 0x9E3779B9U;
      83             : 
      84         660 :         for (i = 0; i < rounds / 2; i++) {
      85         640 :             sum += delta;
      86         640 :             v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
      87         640 :             v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
      88             :         }
      89             :     }
      90             : 
      91          56 :     AV_WB32(dst, v0);
      92          56 :     AV_WB32(dst + 4, v1);
      93          56 : }
      94             : 
      95          20 : void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
      96             :                   uint8_t *iv, int decrypt)
      97             : {
      98             :     int i;
      99             : 
     100          20 :     if (decrypt) {
     101          60 :         while (count--) {
     102          36 :             tea_crypt_ecb(ctx, dst, src, decrypt, iv);
     103             : 
     104          36 :             src   += 8;
     105          36 :             dst   += 8;
     106             :         }
     107             :     } else {
     108          36 :         while (count--) {
     109          20 :             if (iv) {
     110         144 :                 for (i = 0; i < 8; i++)
     111         128 :                     dst[i] = src[i] ^ iv[i];
     112          16 :                 tea_crypt_ecb(ctx, dst, dst, decrypt, NULL);
     113          16 :                 memcpy(iv, dst, 8);
     114             :             } else {
     115           4 :                 tea_crypt_ecb(ctx, dst, src, decrypt, NULL);
     116             :             }
     117          20 :             src   += 8;
     118          20 :             dst   += 8;
     119             :         }
     120             :     }
     121          20 : }

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