[PATCH 2/2] chacha20poly1305: Skip encryption/decryption for 0-len
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: 2015-12-06 01:52:08
Also in:
linux-crypto, lkml, stable
Subsystem:
crypto api, the rest · Maintainers:
Herbert Xu, "David S. Miller", Linus Torvalds
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> Cc: <redacted> --- 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