go: os/exec: environForSysProcAttr is never called as sysattr.Env is never nil

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

$ go version
go version go1.13.4 darwin/amd64

Note: Even though I am developing on darwin, the code is targeted to windows/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN="/Users/liam/git/go_path/bin"
GOCACHE="/Users/liam/Library/Caches/go-build"
GOENV="/Users/liam/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/liam/git/go_path"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.13.4/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.13.4/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/jt/myl07nr11fb6_27x6k61xlzm0000gn/T/go-build237806154=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Launched a process with SysProcAttr set that include a Token for the current active user.

What did you expect to see?

The process should have access to environment variables appropriate to the user it was launched for.

What did you see instead?

The launched process had environment variables originating from the service that started it, rather than those for the user it is running as.

Other comments:

When launching a process on Windows with a SysProcAttr that includes a token, Go doesn’t load the environment variables for that token, instead it uses the environment variables for the current process.

I can see in os/exec_posix.go (on line 40) it does a check to see if the Env is nil, if it is it will call environForSysProcAttr which would load the appropriate environment variables if a token is supplied in the process attributes.

But in the calling method (os/exec/exec.go:416) the Env variable it set by addCriticalEnv(dedupEnv(c.envv())), of which c.envv() will always return a value based on it’s logic:

func (c *Cmd) envv() []string {
	if c.Env != nil {
		return c.Env
	}
	return os.Environ()
}

Ideally, this can probably be removed as environForSysProcAttr for windows and other platforms always fallback to os.Environ() if there is nothing to be done based on the process attributes.