net: lookup_windows.go uses APIs that are no longer in Nano Server

[thecloudtaylor]

The fall release of Nano Server removed a number of APIs with the effort of reducing the size of Nano Server. One of the DLLs removed was NetApi32.dll. Currently there are a few places that lookup_windows.go calls APIs in NetApi32.dll - specifically isDomainJoined(..); lookupFullNameDomain(..) which is in turn called by newUser(..).

It may be possible to refactor a bit to remove this dependency - I will think about it but I wanted to get this logged.

Examples:

go/src/os/user/lookup_windows.go

Lines 18 to 27 in 3098cf0

	func isDomainJoined() (bool, error) {
	var domain *uint16
	var status uint32
	err := syscall.NetGetJoinInformation(nil, &domain, &status)
	if err != nil {
	return false, err
	}
	syscall.NetApiBufferFree((*byte)(unsafe.Pointer(domain)))
	return status == syscall.NetSetupDomainName, nil
	}

go/src/syscall/zsyscall_windows.go

Lines 179 to 181 in 3098cf0

	procGetUserNameExW = modsecur32.NewProc("GetUserNameExW")
	procNetUserGetInfo = modnetapi32.NewProc("NetUserGetInfo")
	procNetGetJoinInformation = modnetapi32.NewProc("NetGetJoinInformation")

EDITED by @odeke-em to use permalinks and format the target examples

[odeke-em]

/cc @mikioh @dsnet @ianlancetaylor

[dsnet]

\cc @alexbrainman. I have almost zero knowledge of Windows.

[alexbrainman]

@taylorb-microsoft

It may be possible to refactor a bit to remove this dependency - I will think about it

SGTM.

We have couple of functions in syscall with name that starts with Load (for example syscall.LoadCancelIoEx). These were created because some versions of Windows did not have those functions - so we used syscall.Load... functions in standard library to program around that limitation. You can do something similar.

If you cannot replace the functionality netapi.dll provides, it is OK to just return error / skip tests. I suspect Nano Server users do not expect that functionality anyway.

Alex

[StefanScherer]

This can be reproduced in a microsoft/nanoserver-insider image with this example code:

package main

import (
	"fmt"
	"os/user"
)

func main() {
	fmt.Println("Hello")
	currentuser, err := user.Current()
	if err == nil {
		fmt.Println("Current user", currentuser)
	} else {
		fmt.Println("Error", err)
	}
}

Running the binary crashes

C:\gopath>currentuser.exe
Hello
panic: Failed to load netapi32.dll: The specified module could not be found.

goroutine 1 [running]:
syscall.(*LazyProc).mustFind(0xc04203b8c0)
	C:/go/src/syscall/dll_windows.go:280 +0x5f
syscall.(*LazyProc).Addr(0xc04203b8c0, 0x1)
	C:/go/src/syscall/dll_windows.go:287 +0x32
syscall.NetGetJoinInformation(0x0, 0xc04205fca8, 0xc04205fca4, 0x0, 0x0)
	C:/go/src/syscall/zsyscall_windows.go:1784 +0x38
os/user.isDomainJoined(0x4623e4, 0x29f8600, 0x0)
	C:/go/src/os/user/lookup_windows.go:21 +0x5a
os/user.lookupFullName(0xc0420440f0, 0xc, 0xc0420440e0, 0xd, 0xc0420421c0, 0x1a, 0xd, 0xc0420421c0, 0x1a, 0x0)
	C:/go/src/os/user/lookup_windows.go:58 +0x2d
os/user.newUser(0xc042068050, 0xc0420440c0, 0xc, 0xc042042180, 0x16, 0x53f1f0, 0x0, 0x0)
	C:/go/src/os/user/lookup_windows.go:88 +0x178
os/user.current(0x0, 0x0, 0x0)
	C:/go/src/os/user/lookup_windows.go:124 +0x18c
os/user.Current.func1()
	C:/go/src/os/user/lookup.go:11 +0x2d
sync.(*Once).Do(0x544660, 0x4d36e8)
	C:/go/src/sync/once.go:44 +0xc5
os/user.Current(0xc04205ff20, 0x1, 0x1)
	C:/go/src/os/user/lookup.go:11 +0x44
main.main()
	C:/gopath/currentuser.go:10 +0x85

[alexbrainman]

This can be reproduced in a microsoft/nanoserver-insider image with this example code:

Thank you @StefanScherer

Alex