net/http: DetectContentType does not detect application/x-tar

[coreydaley]

What version of Go are you using (go version)?

$ go version
go version go1.12.5 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
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/cdaley/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/cdaley/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/golang"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/golang/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/cdaley/Projects/github.com/offlinedocs/offlinedocs/go.mod"
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-build110412641=/tmp/go-build -gno-record-gcc-switches"GOARCH="amd64"
GOBIN=""
GOCACHE="/home/cdaley/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/cdaley/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/golang"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/golang/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/cdaley/Projects/github.com/offlinedocs/offlinedocs/go.mod"
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-build110412641=/tmp/go-build -gno-record-gcc-switches"

What did you do?

extracted the first 512 bytes of a tar file and ran net/http.DetectContentType on it
https://play.golang.org/p/6K9ve_L54ua

What did you expect to see?

application/x-tar

What did you see instead?

application/octet-stream

[gopherbot]

Change https://golang.org/cl/181419 mentions this issue: net/http: add application/x-tar detection to DetectContentType

[odeke-em]

Just like in #32508 (comment), we get the signatures from https://mimesniff.spec.whatwg.org/ so perhaps let's first file an issue on the Github issues https://github.com/whatwg/mimesniff and once that's agreed upon we'll review your CL @coreydaley.

[coreydaley]

@odeke-em thanks, created whatwg/mimesniff#105

[odeke-em]

I am going to move this to the unreleased milestone since we are depending on browsers and the MIME working group to approve the signatures.