[git commit] tls: in AES-GCM decoding, avoid memmove

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=941440cf166ef77ad82c4ead9eae3a8a2552a418
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

function                                             old     new   delta
xorbuf3                                                -      36     +36
xorbuf                                                24      12     -12
tls_xread_record                                     656     634     -22
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/2 up/down: 36/-34)              Total: 2 bytes

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 networking/tls.c        | 20 ++++++++++++++++----
 networking/tls.h        |  1 +
 networking/tls_aesgcm.c |  9 ---------
 networking/tls_aesgcm.h |  2 --
 4 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/networking/tls.c b/networking/tls.c
index 1e0e0991c..1f8c21f8b 100644
--- a/networking/tls.c
+++ b/networking/tls.c
@@ -343,6 +343,20 @@ void FAST_FUNC tls_get_random(void *buf, unsigned len)
 		xfunc_die();
 }
 
+static void xorbuf3(void *dst, const void *src1, const void *src2, unsigned count)
+{
+	uint8_t *d = dst;
+	const uint8_t *s1 = src1;
+	const uint8_t* s2 = src2;
+	while (count--)
+		*d++ = *s1++ ^ *s2++;
+}
+
+void FAST_FUNC xorbuf(void *dst, const void *src, unsigned count)
+{
+	xorbuf3(dst, dst, src, count);
+}
+
 /* Nondestructively see the current hash value */
 static unsigned sha_peek(md5sha_ctx_t *ctx, void *buffer)
 {
@@ -941,7 +955,6 @@ static void tls_aesgcm_decrypt(tls_state_t *tls, uint8_t *buf, int size)
 
 	memcpy(nonce,     tls->server_write_IV, 4);
 	memcpy(nonce + 4, buf, 8);
-	buf += 8;
 
 	cnt = 1;
 	remaining = size;
@@ -952,12 +965,12 @@ static void tls_aesgcm_decrypt(tls_state_t *tls, uint8_t *buf, int size)
 		COUNTER(nonce) = htonl(cnt); /* yes, first cnt here is 2 (!) */
 		aes_encrypt_one_block(&tls->aes_decrypt, nonce, scratch);
 		n = remaining > AES_BLOCK_SIZE ? AES_BLOCK_SIZE : remaining;
-		xorbuf(buf, scratch, n);
+		xorbuf3(buf, scratch, buf + 8, n);
 		buf += n;
 		remaining -= n;
 	}
 
-	//aesgcm_GHASH(tls->H, aad, tls->outbuf + OUTBUF_PFX, size, authtag);
+	//aesgcm_GHASH(tls->H, aad, tls->inbuf + RECHDR_LEN, size, authtag);
 	//COUNTER(nonce) = htonl(1);
 	//aes_encrypt_one_block(&tls->aes_encrypt, nonce, scratch);
 	//xorbuf(authtag, scratch, sizeof(authtag));
@@ -1046,7 +1059,6 @@ static int tls_xread_record(tls_state_t *tls, const char *expected)
 
 			sz -= 8 + AES_BLOCK_SIZE; /* we will overwrite nonce, drop hash */
 			tls_aesgcm_decrypt(tls, p, sz);
-			memmove(p, p + 8, sz);
 			dbg("encrypted size:%u\n", sz);
 		} else
 		if (tls->min_encrypted_len_on_read > tls->MAC_size) {
diff --git a/networking/tls.h b/networking/tls.h
index f2ef67aac..4b0dc7459 100644
--- a/networking/tls.h
+++ b/networking/tls.h
@@ -81,6 +81,7 @@ typedef  int16_t  int16;
 #define AES_BLOCK_SIZE  16
 
 void tls_get_random(void *buf, unsigned len) FAST_FUNC;
+void xorbuf(void* buf, const void* mask, unsigned count) FAST_FUNC;
 
 #define matrixCryptoGetPrngData(buf, len, userPtr) (tls_get_random(buf, len), PS_SUCCESS)
 
diff --git a/networking/tls_aesgcm.c b/networking/tls_aesgcm.c
index b9a6a9b0a..db720e5f6 100644
--- a/networking/tls_aesgcm.c
+++ b/networking/tls_aesgcm.c
@@ -11,15 +11,6 @@ typedef uint32_t word32;
 #define XMEMSET memset
 #define XMEMCPY memcpy
 
-void FAST_FUNC xorbuf(void* buf, const void* mask, unsigned count)
-{
-    word32 i;
-    byte*       b = (byte*)buf;
-    const byte* m = (const byte*)mask;
-    for (i = 0; i < count; i++)
-        b[i] ^= m[i];
-}
-
 /* from wolfssl-3.15.3/wolfcrypt/src/aes.c */
 
 static ALWAYS_INLINE void FlattenSzInBits(byte* buf, word32 sz)
diff --git a/networking/tls_aesgcm.h b/networking/tls_aesgcm.h
index 75694f3fa..d7e672e6e 100644
--- a/networking/tls_aesgcm.h
+++ b/networking/tls_aesgcm.h
@@ -4,8 +4,6 @@
  * Licensed under GPLv2, see file LICENSE in this source tree.
  */
 
-void xorbuf(void* buf, const void* mask, unsigned count) FAST_FUNC;
-
 void aesgcm_GHASH(uint8_t* h,
 	const uint8_t* a, //unsigned aSz,
 	const uint8_t* c, unsigned cSz,