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xtea: fix CBC mode when src=dst

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In CBC mode, when src=dst and we are decrypting a block different
from the first one, we need to save the current block of ciphertext
(which will constitute the initialization vector for the next block)
before we overwrite it.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Giorgio Vazzana 2012-09-30 16:00:19 +02:00 committed by Michael Niedermayer
parent a0321dadfd
commit 8c3ee93be5
1 changed files with 8 additions and 1 deletions
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7
libavutil/xtea.c
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@ -152,14 +152,21 @@ void av_xtea_crypt(AVXTEA *ctx, uint8_t *dst, const uint8_t *src, int count,
uint8_t *iv, int decrypt) uint8_t *iv, int decrypt)
{ {
int i; int i;
uint8_t iv_tmp[8];
if (decrypt) { if (decrypt) {
while (count--) { while (count--) {
if (src == dst)
memcpy(iv_tmp, src, 8);
xtea_crypt_ecb(ctx, dst, src, decrypt); xtea_crypt_ecb(ctx, dst, src, decrypt);
if (iv) { if (iv) {
for (i = 0; i < 8; i++) for (i = 0; i < 8; i++)
dst[i] = dst[i] ^ iv[i]; dst[i] = dst[i] ^ iv[i];
if (src == dst)
memcpy(iv, iv_tmp, 8);
else
memcpy(iv, src, 8); memcpy(iv, src, 8);
} }