From 2445ff3f71f174d7cb1a774280d26d6c69211618 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=E7=AB=99=E8=B4=B4=E5=90=A7=E8=9C=A1=E6=B2=B9?=
 <la_you@qq.com>
Date: Sun, 10 Mar 2024 00:11:06 +0800
Subject: [PATCH] Fix CFB8 non-overlapping decrypt (#275)

* Fix CFB8 non-overlapping decrypt

* Fix CFB8 edge case of empty src
---
 net/CFB8/cfb8.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/CFB8/cfb8.go b/net/CFB8/cfb8.go
index 26e0cbf..8229468 100644
--- a/net/CFB8/cfb8.go
+++ b/net/CFB8/cfb8.go
@@ -35,6 +35,9 @@ func newCFB8(c cipher.Block, iv []byte, de bool) *CFB8 {
 }
 
 func (cf *CFB8) XORKeyStream(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
 	if len(dst) < len(src) {
 		panic("cfb8: output smaller than input")
 	}
@@ -65,7 +68,9 @@ func (cf *CFB8) XORKeyStream(dst, src []byte) {
 			val byte
 		)
 		dst = dst[:len(src)]
-		if cf.de {
+		if cf.de && // and requires to be non-overlapping at all
+			uintptr(unsafe.Pointer(&dst[0])) <= uintptr(unsafe.Pointer(&src[len(src)-1])) &&
+			uintptr(unsafe.Pointer(&src[0])) <= uintptr(unsafe.Pointer(&dst[len(dst)-1])) {
 			for i = 0; i < len(src)-cf.blockSize; i += 1 {
 				cf.c.Encrypt(dst[i:], ciphertext[i:])
 			}