From 161151d79ff4f7ed35d4ebb0eb7727a517c34ef2 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" <Jason@zx2c4.com> Date: Sun, 6 Dec 2015 02:51:38 +0100 Subject: [PATCH] crypto: chacha20poly1305 - Skip encryption/decryption for 0-len 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 <Jason@zx2c4.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> --- crypto/chacha20poly1305.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/crypto/chacha20poly1305.c b/crypto/chacha20poly1305.c index 99c3cce01290..7b6b935cef23 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); }