[email protected] (Niels Möller) writes:
> I would guess that means that we got 209 bytes, including the 16-byte
> poly1305 authentication tag. Message size is then 209 - 16 = 193 bytes.
> If the first byte is a TLS packet type, the "length: 192" in the next to
> last line makes sense if the packet type byte is excluded. Right?
I've found one problem, although I don't see that it would cause
precisely the reported problem. It would result in incorrect
encrypt/decrypt of the data immediately after a call to chacha_crypt or
chacha_crypt32 with 129 <= (length % 256) <= 192. In code used only on
ppc64 with the new altivec chacha code enabled.
Tentative patch below, but I need to extend the tests to get proper test
coverage of this case.
Regards,
/Niels
diff --git a/chacha-crypt.c b/chacha-crypt.c
index 081ebcf4..9db13183 100644
--- a/chacha-crypt.c
+++ b/chacha-crypt.c
@@ -80,13 +80,16 @@ _nettle_chacha_crypt_4core(struct chacha_ctx *ctx,
while (length > 2*CHACHA_BLOCK_SIZE)
{
_nettle_chacha_4core (x, ctx->state, CHACHA_ROUNDS);
- ctx->state[12] += 4;
- ctx->state[13] += (ctx->state[12] < 4);
if (length <= 4*CHACHA_BLOCK_SIZE)
{
+ uint32_t blocks = 3 + (length > 3*CHACHA_BLOCK_SIZE);
+ ctx->state[12] += blocks;
+ ctx->state[13] += (ctx->state[12] < blocks);
memxor3 (dst, src, x, length);
return;
}
+ ctx->state[12] += 4;
+ ctx->state[13] += (ctx->state[12] < 4);
memxor3 (dst, src, x, 4*CHACHA_BLOCK_SIZE);
length -= 4*CHACHA_BLOCK_SIZE;
@@ -200,12 +203,13 @@ _nettle_chacha_crypt32_4core(struct chacha_ctx *ctx,
while (length > 2*CHACHA_BLOCK_SIZE)
{
_nettle_chacha_4core32 (x, ctx->state, CHACHA_ROUNDS);
- ctx->state[12] += 4;
if (length <= 4*CHACHA_BLOCK_SIZE)
{
+ ctx->state[12] += 3 + (length > 3*CHACHA_BLOCK_SIZE);
memxor3 (dst, src, x, length);
return;
}
+ ctx->state[12] += 4;
memxor3 (dst, src, x, 4*CHACHA_BLOCK_SIZE);
length -= 4*CHACHA_BLOCK_SIZE;
--
Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677.
Internet email is subject to wholesale government surveillance.
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