From 3c5e296178a09a28bad5f66556f3d39b3fe14727 Mon Sep 17 00:00:00 2001
From: Lucas Gabriel Vuotto <lucas@lgv5.net>
Date: Wed, 19 Jun 2024 13:18:25 +0000
Subject: [PATCH] Use a single zero buffer

---
 aead_chacha20_poly1305.c | 18 ++++++++----------
 internal.h               |  8 ++++++++
 kdf_hkdf.c               |  5 +----
 util.c                   |  3 +++
 4 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/aead_chacha20_poly1305.c b/aead_chacha20_poly1305.c
index 886fe46..6ce4f68 100644
--- a/aead_chacha20_poly1305.c
+++ b/aead_chacha20_poly1305.c
@@ -23,8 +23,6 @@
  * according to draft-irtf-cfrg-xchacha-03.
  */
 
-static const uint8_t	zeropad[16];
-
 static int
 chacha20_xchacha20_keysetup(struct lc_cipher_ctx *cctx,
     uint8_t akey[LC_POLY1305_KEYLEN], void *initparams)
@@ -94,7 +92,7 @@ chacha20_poly1305_seal(uint8_t *out, size_t *outlen, void *initparams,
 	    !lc_auth_update(actx, aad, aadlen))
 		goto cleanup;
 	if (aadlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (aadlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (aadlen % 16)))
 			goto cleanup;
 
 	cparams.counter = 1;
@@ -111,7 +109,7 @@ chacha20_poly1305_seal(uint8_t *out, size_t *outlen, void *initparams,
 	if (!lc_auth_update(actx, out, inlen))
 		goto cleanup;
 	if (inlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (inlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (inlen % 16)))
 			goto cleanup;
 
 	store64le(&buf[0], aadlen);
@@ -183,7 +181,7 @@ xchacha20_poly1305_seal(uint8_t *out, size_t *outlen, void *initparams,
 	    !lc_auth_update(actx, aad, aadlen))
 		goto cleanup;
 	if (aadlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (aadlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (aadlen % 16)))
 			goto cleanup;
 
 	cparams.counter = 1;
@@ -200,7 +198,7 @@ xchacha20_poly1305_seal(uint8_t *out, size_t *outlen, void *initparams,
 	if (!lc_auth_update(actx, out, inlen))
 		goto cleanup;
 	if (inlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (inlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (inlen % 16)))
 			goto cleanup;
 
 	store64le(&buf[0], aadlen);
@@ -274,14 +272,14 @@ chacha20_poly1305_open(uint8_t *out, size_t *outlen, void *initparams,
 	    !lc_auth_update(actx, aad, aadlen))
 		goto cleanup;
 	if (aadlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (aadlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (aadlen % 16)))
 			goto cleanup;
 
 	ctlen = inlen - LC_POLY1305_TAGLEN;
 	if (!lc_auth_update(actx, in, ctlen))
 		goto cleanup;
 	if (ctlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (ctlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (ctlen % 16)))
 			goto cleanup;
 
 	store64le(&buf[0], aadlen);
@@ -369,14 +367,14 @@ xchacha20_poly1305_open(uint8_t *out, size_t *outlen, void *initparams,
 	    !lc_auth_update(actx, aad, aadlen))
 		goto cleanup;
 	if (aadlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (aadlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (aadlen % 16)))
 			goto cleanup;
 
 	ctlen = inlen - LC_POLY1305_TAGLEN;
 	if (!lc_auth_update(actx, in, ctlen))
 		goto cleanup;
 	if (ctlen % 16 != 0)
-		if (!lc_auth_update(actx, zeropad, 16 - (ctlen % 16)))
+		if (!lc_auth_update(actx, zerobuf, 16 - (ctlen % 16)))
 			goto cleanup;
 
 	store64le(&buf[0], aadlen);
diff --git a/internal.h b/internal.h
index 4895723..c05d4b5 100644
--- a/internal.h
+++ b/internal.h
@@ -208,4 +208,12 @@ void	sha256_block(struct sha256_state *);
 
 void	sha512_block(struct sha512_state *);
 
+
+/*
+ * VARIABLES
+ */
+
+extern uint8_t	zerobuf[128];
+
+
 #endif /* LC_INTERNAL_H */
diff --git a/kdf_hkdf.c b/kdf_hkdf.c
index 54d6736..d967743 100644
--- a/kdf_hkdf.c
+++ b/kdf_hkdf.c
@@ -19,9 +19,6 @@
 #include "internal.h"
 
 
-static uint8_t	zeros[HMAC_HASHLEN_MAX];
-
-
 static int
 hkdf_kdf(uint8_t *out, size_t *outlen, void *initparams, size_t len)
 {
@@ -51,7 +48,7 @@ hkdf_kdf(uint8_t *out, size_t *outlen, void *initparams, size_t len)
 
 	hmacparams.hash = params->hash;
 	if (params->saltlen == 0) {
-		hmacparams.key = zeros;
+		hmacparams.key = zerobuf;
 		hmacparams.keylen = hashlen;
 	} else {
 		hmacparams.key = params->salt;
diff --git a/util.c b/util.c
index 4f7eff2..c19a823 100644
--- a/util.c
+++ b/util.c
@@ -23,6 +23,9 @@
 #define HEXDUMP_BUFSZ	128
 
 
+uint8_t	zerobuf[128] = { 0 };
+
+
 static size_t
 hexdump_line(char *buf, const uint8_t *blob, size_t len, size_t off, int pad)
 {