From: Giorgio Vazzana <mywin...@gmail.com>
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.
---
libavutil/xtea.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/libavutil/xtea.c b/libavutil/xtea.c
index bf5db11..41aed2b 100644
--- a/libavutil/xtea.c
+++ b/libavutil/xtea.c
@@ -70,15 +70,22 @@ void av_xtea_crypt(AVXTEA *ctx, uint8_t *dst, const uint8_t
*src, int count,
uint8_t *iv, int decrypt)
{
int i;
+ uint8_t iv_tmp[8];
if (decrypt) {
while (count--) {
+ if (src == dst)
+ memcpy(iv_tmp, src, 8);
+
xtea_crypt_ecb(ctx, dst, src, decrypt);
if (iv) {
for (i = 0; i < 8; i++)
dst[i] = dst[i] ^ iv[i];
- memcpy(iv, src, 8);
+ if (src == dst)
+ memcpy(iv, iv_tmp, 8);
+ else
+ memcpy(iv, src, 8);
}
src += 8;
--
1.7.9.4
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