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/*
* A 32-bit implementation of the TEA algorithm
* Copyright (c) 2015 Vesselin Bontchev
*
* Loosely based on the implementation of David Wheeler and Roger Needham,
* https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm#Reference_code
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "avutil.h"
#include "common.h"
#include "intreadwrite.h"
#include "tea.h"
typedef struct AVTEA {
uint32_t key[16];
int rounds;
} AVTEA;
struct AVTEA *av_tea_alloc(void)
{
return av_mallocz(sizeof(struct AVTEA));
}
const int av_tea_size = sizeof(AVTEA);
void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
{
int i;
for (i = 0; i < 4; i++)
ctx->key[i] = AV_RB32(key + (i << 2));
ctx->rounds = rounds;
}
static void tea_crypt_ecb(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
int decrypt, uint8_t *iv)
{
uint32_t v0, v1;
int rounds = ctx->rounds;
uint32_t k0, k1, k2, k3;
k0 = ctx->key[0];
k1 = ctx->key[1];
k2 = ctx->key[2];
k3 = ctx->key[3];
v0 = AV_RB32(src);
v1 = AV_RB32(src + 4);
if (decrypt) {
int i;
uint32_t delta = 0x9E3779B9U, sum = delta * (rounds / 2);
for (i = 0; i < rounds / 2; i++) {
v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
sum -= delta;
}
if (iv) {
v0 ^= AV_RB32(iv);
v1 ^= AV_RB32(iv + 4);
memcpy(iv, src, 8);
}
} else {
int i;
uint32_t sum = 0, delta = 0x9E3779B9U;
for (i = 0; i < rounds / 2; i++) {
sum += delta;
v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
}
}
AV_WB32(dst, v0);
AV_WB32(dst + 4, v1);
}
void av_tea_crypt(AVTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
uint8_t *iv, int decrypt)
{
int i;
if (decrypt) {
while (count--) {
tea_crypt_ecb(ctx, dst, src, decrypt, iv);
src += 8;
dst += 8;
}
} else {
while (count--) {
if (iv) {
for (i = 0; i < 8; i++)
dst[i] = src[i] ^ iv[i];
tea_crypt_ecb(ctx, dst, dst, decrypt, NULL);
memcpy(iv, dst, 8);
} else {
tea_crypt_ecb(ctx, dst, src, decrypt, NULL);
}
src += 8;
dst += 8;
}
}
}
#ifdef TEST
#include <stdio.h>
#define TEA_NUM_TESTS 4
// https://github.com/logandrews/TeaCrypt/blob/master/tea/tea_test.go
static const uint8_t tea_test_key[TEA_NUM_TESTS][16] = {
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
},
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
},
{ 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
},
{ 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
}
};
static const uint8_t tea_test_pt[TEA_NUM_TESTS][8] = {
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
{ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 },
{ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 },
{ 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF }
};
static const uint8_t tea_test_ct[TEA_NUM_TESTS][8] = {
{ 0x41, 0xEA, 0x3A, 0x0A, 0x94, 0xBA, 0xA9, 0x40 },
{ 0x6A, 0x2F, 0x9C, 0xF3, 0xFC, 0xCF, 0x3C, 0x55 },
{ 0xDE, 0xB1, 0xC0, 0xA2, 0x7E, 0x74, 0x5D, 0xB3 },
{ 0x12, 0x6C, 0x6B, 0x92, 0xC0, 0x65, 0x3A, 0x3E }
};
static void test_tea(AVTEA *ctx, uint8_t *dst, const uint8_t *src,
const uint8_t *ref, int len, uint8_t *iv, int dir,
const char *test)
{
av_tea_crypt(ctx, dst, src, len, iv, dir);
if (memcmp(dst, ref, 8*len)) {
int i;
printf("%s failed\ngot ", test);
for (i = 0; i < 8*len; i++)
printf("%02x ", dst[i]);
printf("\nexpected ");
for (i = 0; i < 8*len; i++)
printf("%02x ", ref[i]);
printf("\n");
exit(1);
}
}
int main(void)
{
AVTEA *ctx;
uint8_t buf[8], iv[8];
int i;
static const uint8_t src[32] = "HelloWorldHelloWorldHelloWorld";
uint8_t ct[32];
uint8_t pl[32];
ctx = av_tea_alloc();
if (!ctx)
return 1;
for (i = 0; i < TEA_NUM_TESTS; i++) {
av_tea_init(ctx, tea_test_key[i], 64);
test_tea(ctx, buf, tea_test_pt[i], tea_test_ct[i], 1, NULL, 0, "encryption");
test_tea(ctx, buf, tea_test_ct[i], tea_test_pt[i], 1, NULL, 1, "decryption");
/* encrypt */
memcpy(iv, "HALLO123", 8);
av_tea_crypt(ctx, ct, src, 4, iv, 0);
/* decrypt into pl */
memcpy(iv, "HALLO123", 8);
test_tea(ctx, pl, ct, src, 4, iv, 1, "CBC decryption");
memcpy(iv, "HALLO123", 8);
test_tea(ctx, ct, ct, src, 4, iv, 1, "CBC inplace decryption");
}
printf("Test encryption/decryption success.\n");
av_free(ctx);
return 0;
}
#endif
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