Re: [PATCH 2/2] chacha20poly1305: Skip encryption/decryption for 0-len

[Herbert Xu]

On Sun, Dec 06, 2015 at 02:51:38AM +0100, Jason A. Donenfeld wrote:
> If the length of the plaintext is zero, there's no need to waste cycles
> on encryption and decryption. Using the chacha20poly1305 construction
> for zero-length plaintexts is a common way of using a shared encryption
> key for AAD authentication.
> 
> Signed-off-by: Jason A. Donenfeld 

Patch applied.  Thanks.
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Email: Herbert Xu 
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[PATCH 2/2] chacha20poly1305: Skip encryption/decryption for 0-len

[Jason A. Donenfeld]

If the length of the plaintext is zero, there's no need to waste cycles
on encryption and decryption. Using the chacha20poly1305 construction
for zero-length plaintexts is a common way of using a shared encryption
key for AAD authentication.

Signed-off-by: Jason A. Donenfeld 
Cc: 
---
 crypto/chacha20poly1305.c | 8 
 1 file changed, 8 insertions(+)

diff --git a/crypto/chacha20poly1305.c b/crypto/chacha20poly1305.c
index 99c3cce..7b6b935 100644
--- a/crypto/chacha20poly1305.c
+++ b/crypto/chacha20poly1305.c
@@ -130,6 +130,9 @@ static int chacha_decrypt(struct aead_request *req)
struct scatterlist *src, *dst;
int err;
 
+   if (rctx->cryptlen == 0)
+   goto skip;
+
chacha_iv(creq->iv, req, 1);
 
sg_init_table(rctx->src, 2);
@@ -150,6 +153,7 @@ static int chacha_decrypt(struct aead_request *req)
if (err)
return err;
 
+skip:
return poly_verify_tag(req);
 }
 
@@ -415,6 +419,9 @@ static int chacha_encrypt(struct aead_request *req)
struct scatterlist *src, *dst;
int err;
 
+   if (req->cryptlen == 0)
+   goto skip;
+
chacha_iv(creq->iv, req, 1);
 
sg_init_table(rctx->src, 2);
@@ -435,6 +442,7 @@ static int chacha_encrypt(struct aead_request *req)
if (err)
return err;
 
+skip:
return poly_genkey(req);
 }
 
-- 
2.6.3

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