image/png: invalid format: chunk out of order #54142
Description
What version of Go are you using (go version)?
$ go version go version go1.17.6 linux/amd64
Does this issue reproduce with the latest release?
yes
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="off" GOARCH="amd64" GOBIN="" GOCACHE="/home/deck/.cache/go-build" GOENV="/home/deck/.config/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/deck/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/deck/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/usr/lib/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64" GOVCS="" GOVERSION="go1.17.6" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3730379239=/tmp/go-build -gno-record-gcc-switches"
What did you do?
Try to decode e.g. this file with png.Decode().
What did you expect to see?
No error and decoded image.
What did you see instead?
invalid format: chunk out of order
What I think is the cause
It looks like the problem is here.
This code expects that PLTE chunk is present only for Color type = 3 (Paletted). If it is present for other types, the mentioned error is thrown.
According to PNG specification, PLTE chunk may appear also for types 2 or 6. The PNG file linked above is type 2 and contains PLTE chunk, so it is compliant with PNG specs.