From acc81a28c526d31ad553663f068664bfa0f9e99e Mon Sep 17 00:00:00 2001
From: Klaus Post <klauspost@gmail.com>
Date: Thu, 10 Mar 2022 11:42:26 +0100
Subject: [PATCH] zstd: Revert "Disallow 0 sized compressed blocks"

Fixes #526

Bonus, use `ignorecrc` for disabling crc checks in while fuzzing.
---
 zstd/blockdec.go       |   6 +++---
 zstd/fuzz.go           |   4 ++--
 zstd/fuzz_none.go      |   4 ++--
 zstd/testdata/bad.zip  | Bin 9418 -> 9243 bytes
 zstd/testdata/good.zip | Bin 2848 -> 3023 bytes
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/zstd/blockdec.go b/zstd/blockdec.go
index 50abf56569..7d567a54a0 100644
--- a/zstd/blockdec.go
+++ b/zstd/blockdec.go
@@ -167,9 +167,9 @@ func (b *blockDec) reset(br byteBuffer, windowSize uint64) error {
 			}
 			return ErrCompressedSizeTooBig
 		}
-		// Empty compressed blocks not valid in practice,
-		// see https://github.com/facebook/zstd/issues/3090
-		if cSize < 3 {
+		// Empty compressed blocks must at least be 2 bytes
+		// for Literals_Block_Type and one for Sequences_Section_Header.
+		if cSize < 2 {
 			return ErrBlockTooSmall
 		}
 	case blockTypeRaw:
diff --git a/zstd/fuzz.go b/zstd/fuzz.go
index fda8a74228..7f2210e053 100644
--- a/zstd/fuzz.go
+++ b/zstd/fuzz.go
@@ -1,5 +1,5 @@
-//go:build gofuzz
-// +build gofuzz
+//go:build ignorecrc
+// +build ignorecrc
 
 // Copyright 2019+ Klaus Post. All rights reserved.
 // License information can be found in the LICENSE file.
diff --git a/zstd/fuzz_none.go b/zstd/fuzz_none.go
index 0515b201cc..6811c68a89 100644
--- a/zstd/fuzz_none.go
+++ b/zstd/fuzz_none.go
@@ -1,5 +1,5 @@
-//go:build !gofuzz
-// +build !gofuzz
+//go:build !ignorecrc
+// +build !ignorecrc
 
 // Copyright 2019+ Klaus Post. All rights reserved.
 // License information can be found in the LICENSE file.
diff --git a/zstd/testdata/bad.zip b/zstd/testdata/bad.zip
index 15be3cd510a159ed6d4ca9618c9c43fd837bf744..28f061286759aa4f08da1e947fd8d1b990ea1d3d 100644
GIT binary patch
delta 41
ucmX@*Ioo4{p7`W66_L%;#Y=gB3^_)X$*n5pd^!v|4D~z=3~k~JKmY(34hmoZ

delta 205
zcmbR3amsUpp18kfUS^0_o)a540|NsH>j1Hlk-15Vv0<t~im91pTB>ELv0+kbO0r3s
zWm-x~ie<88nxUadvQe5|RdLDX8>{|bZ*ZK#$iWcc&CD`+qq5XyC-G7qFKh+_%?1Jm
pAXX74-kQnFmGzh^#V0$6>xl(;v$BEA&;`PqJPZuCf#xtU003wqF}45z

diff --git a/zstd/testdata/good.zip b/zstd/testdata/good.zip
index f6c230bc5d5b3e9d2d4ff61de33f30f411c2bc1a..e38a0f275c89970328d62780225caccd865a97d5 100644
GIT binary patch
delta 207
zcmZ1=c3ynLI@Vxj77+#}1`Y<#yvz`<JSR481_lNY)&XK8BXg4!W5ZN~6jL+Hv{cJf
zW5cA>lw^}M%e0h~6w74GG($s^WTP~_s^XH%H&*?>-rzWek%M9L8rB5XJVquF2HZvi
dO$P!6AYQ{tnneNLtZX2?;y}0qsFxAU0|3WmE#LqE

delta 33
kcmX>vzCdilI@Zn1Y;mk2tZWQGAO?hStPBimfS7>+0E4^*egFUf