From 02ac9c9420275868472f33b01def01218742b8bb Mon Sep 17 00:00:00 2001
From: Tomas Mraz <tomas@openssl.org>
Date: Mon, 17 Apr 2023 16:51:20 +0200
Subject: [PATCH] aesv8-armx.pl: Avoid buffer overrread in AES-XTS decryption

Original author: Nevine Ebeid (Amazon)
Fixes: CVE-2023-1255

The buffer overread happens on decrypts of 4 mod 5 sizes.
Unless the memory just after the buffer is unmapped this is harmless.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
(Merged from https://github.com/openssl/openssl/pull/20759)

(cherry picked from commit 72dfe46550ee1f1bbfacd49f071419365bc23304)
---
 crypto/aes/asm/aesv8-armx.pl |  4 +++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/crypto/aes/asm/aesv8-armx.pl b/crypto/aes/asm/aesv8-armx.pl
index 6a7bf05d1b..bd583e2c89 100755
--- a/crypto/aes/asm/aesv8-armx.pl
+++ b/crypto/aes/asm/aesv8-armx.pl
@@ -3353,7 +3353,7 @@ $code.=<<___	if ($flavour =~ /64/);
 .align	4
 .Lxts_dec_tail4x:
 	add	$inp,$inp,#16
-	vld1.32	{$dat0},[$inp],#16
+	tst	$tailcnt,#0xf
 	veor	$tmp1,$dat1,$tmp0
 	vst1.8	{$tmp1},[$out],#16
 	veor	$tmp2,$dat2,$tmp2
@@ -3362,6 +3362,8 @@ $code.=<<___	if ($flavour =~ /64/);
 	veor	$tmp4,$dat4,$tmp4
 	vst1.8	{$tmp3-$tmp4},[$out],#32
 
+	b.eq	.Lxts_dec_abort
+	vld1.32	{$dat0},[$inp],#16
 	b	.Lxts_done
 .align	4
 .Lxts_outer_dec_tail:
-- 
2.34.1