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121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
/*
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* A 32-bit implementation of the TEA algorithm
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* Copyright (c) 2015 Vesselin Bontchev
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*
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* Loosely based on the implementation of David Wheeler and Roger Needham,
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* https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm#Reference_code
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avutil.h"
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#include "common.h"
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#include "intreadwrite.h"
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#include "tea.h"
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typedef struct AVTEA {
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uint32_t key[16];
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int rounds;
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} AVTEA;
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struct AVTEA *av_tea_alloc(void)
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{
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return av_mallocz(sizeof(struct AVTEA));
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}
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const int av_tea_size = sizeof(AVTEA);
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void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
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{
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int i;
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for (i = 0; i < 4; i++)
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ctx->key[i] = AV_RB32(key + (i << 2));
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ctx->rounds = rounds;
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}
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static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
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int decrypt, uint8_t *iv)
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{
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uint32_t v0, v1;
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int rounds = ctx->rounds;
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uint32_t k0, k1, k2, k3;
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k0 = ctx->key[0];
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k1 = ctx->key[1];
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k2 = ctx->key[2];
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k3 = ctx->key[3];
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v0 = AV_RB32(src);
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v1 = AV_RB32(src + 4);
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if (decrypt) {
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int i;
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uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2);
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for (i = 0; i < rounds / 2; i++) {
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v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
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v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
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sum -= delta;
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}
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if (iv) {
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v0 ^= AV_RB32(iv);
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v1 ^= AV_RB32(iv + 4);
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memcpy(iv, src, 8);
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}
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} else {
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int i;
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uint32_t sum = 0, delta = 0x9E3779B9U;
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for (i = 0; i < rounds / 2; i++) {
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sum += delta;
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v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
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v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
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}
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}
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AV_WB32(dst, v0);
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AV_WB32(dst + 4, v1);
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}
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void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
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uint8_t *iv, int decrypt)
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{
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int i;
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if (decrypt) {
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while (count--) {
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tea_crypt_ecb(ctx, dst, src, decrypt, iv);
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src += 8;
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dst += 8;
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}
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} else {
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while (count--) {
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if (iv) {
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for (i = 0; i < 8; i++)
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dst[i] = src[i] ^ iv[i];
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tea_crypt_ecb(ctx, dst, dst, decrypt, NULL);
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memcpy(iv, dst, 8);
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} else {
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tea_crypt_ecb(ctx, dst, src, decrypt, NULL);
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}
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src += 8;
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dst += 8;
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}
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}
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}
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