blob: b138f8bea1a3e925480a0f705c0ef5522a29743a
| 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 | struct AVTEA *av_tea_alloc(void) |
| 36 | { |
| 37 | return av_mallocz(sizeof(struct AVTEA)); |
| 38 | } |
| 39 | |
| 40 | const int av_tea_size = sizeof(AVTEA); |
| 41 | |
| 42 | void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds) |
| 43 | { |
| 44 | int i; |
| 45 | |
| 46 | for (i = 0; i < 4; i++) |
| 47 | ctx->key[i] = AV_RB32(key + (i << 2)); |
| 48 | |
| 49 | ctx->rounds = rounds; |
| 50 | } |
| 51 | |
| 52 | 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 | int rounds = ctx->rounds; |
| 57 | uint32_t k0, k1, k2, k3; |
| 58 | k0 = ctx->key[0]; |
| 59 | k1 = ctx->key[1]; |
| 60 | k2 = ctx->key[2]; |
| 61 | k3 = ctx->key[3]; |
| 62 | |
| 63 | v0 = AV_RB32(src); |
| 64 | v1 = AV_RB32(src + 4); |
| 65 | |
| 66 | if (decrypt) { |
| 67 | int i; |
| 68 | uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2); |
| 69 | |
| 70 | for (i = 0; i < rounds / 2; i++) { |
| 71 | v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3); |
| 72 | v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1); |
| 73 | sum -= delta; |
| 74 | } |
| 75 | if (iv) { |
| 76 | v0 ^= AV_RB32(iv); |
| 77 | v1 ^= AV_RB32(iv + 4); |
| 78 | memcpy(iv, src, 8); |
| 79 | } |
| 80 | } else { |
| 81 | int i; |
| 82 | uint32_t sum = 0, delta = 0x9E3779B9U; |
| 83 | |
| 84 | for (i = 0; i < rounds / 2; i++) { |
| 85 | sum += delta; |
| 86 | v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1); |
| 87 | v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3); |
| 88 | } |
| 89 | } |
| 90 | |
| 91 | AV_WB32(dst, v0); |
| 92 | AV_WB32(dst + 4, v1); |
| 93 | } |
| 94 | |
| 95 | 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 | if (decrypt) { |
| 101 | while (count--) { |
| 102 | tea_crypt_ecb(ctx, dst, src, decrypt, iv); |
| 103 | |
| 104 | src += 8; |
| 105 | dst += 8; |
| 106 | } |
| 107 | } else { |
| 108 | while (count--) { |
| 109 | if (iv) { |
| 110 | for (i = 0; i < 8; i++) |
| 111 | dst[i] = src[i] ^ iv[i]; |
| 112 | tea_crypt_ecb(ctx, dst, dst, decrypt, NULL); |
| 113 | memcpy(iv, dst, 8); |
| 114 | } else { |
| 115 | tea_crypt_ecb(ctx, dst, src, decrypt, NULL); |
| 116 | } |
| 117 | src += 8; |
| 118 | dst += 8; |
| 119 | } |
| 120 | } |
| 121 | } |
| 122 |