Add fs.ResolvePath to resolve symbolic links

internal/fs/doc.go

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+// This package contains Win32 filesystem functionality.
+package fs

internal/fs/fs.go

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+//go:build windows
+
+package fs
+
+import (
+	"golang.org/x/sys/windows"
+
+	"github.com/Microsoft/go-winio/internal/stringbuffer"
+)
+
+//go:generate go run github.com/Microsoft/go-winio/tools/mkwinsyscall -output zsyscall_windows.go fs.go
+
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
+//sys CreateFile(name string, access AccessMask, mode FileShareMode, sa *syscall.SecurityAttributes, createmode FileCreationDisposition, attrs FileFlagOrAttribute, templatefile windows.Handle) (handle windows.Handle, err error) [failretval==windows.InvalidHandle] = CreateFileW
+
+const NullHandle windows.Handle = 0
+
+// AccessMask defines standard, specific, and generic rights.
+//
+//	Bitmask:
+//	 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
+//	 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+//	+---------------+---------------+-------------------------------+
+//	|G|G|G|G|Resvd|A| StandardRights|         SpecificRights        |
+//	|R|W|E|A|     |S|               |                               |
+//	+-+-------------+---------------+-------------------------------+
+//
+//	GR     Generic Read
+//	GW     Generic Write
+//	GE     Generic Exectue
+//	GA     Generic All
+//	Resvd  Reserved
+//	AS     Access Security System
+//
+// https://learn.microsoft.com/en-us/windows/win32/secauthz/access-mask
+//
+// https://learn.microsoft.com/en-us/windows/win32/secauthz/generic-access-rights
+//
+// https://learn.microsoft.com/en-us/windows/win32/fileio/file-access-rights-constants
+type AccessMask = windows.ACCESS_MASK
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	// Not actually any.
+	//
+	// For CreateFile: "query certain metadata such as file, directory, or device attributes without accessing that file or device"
+	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew#parameters
+	FILE_ANY_ACCESS AccessMask = 0
+
+	// Specific Object Access
+	// from ntioapi.h
+
+	FILE_READ_DATA      AccessMask = (0x0001) // file & pipe
+	FILE_LIST_DIRECTORY AccessMask = (0x0001) // directory
+
+	FILE_WRITE_DATA AccessMask = (0x0002) // file & pipe
+	FILE_ADD_FILE   AccessMask = (0x0002) // directory
+
+	FILE_APPEND_DATA          AccessMask = (0x0004) // file
+	FILE_ADD_SUBDIRECTORY     AccessMask = (0x0004) // directory
+	FILE_CREATE_PIPE_INSTANCE AccessMask = (0x0004) // named pipe
+
+	FILE_READ_EA         AccessMask = (0x0008) // file & directory
+	FILE_READ_PROPERTIES AccessMask = FILE_READ_EA
+
+	FILE_WRITE_EA         AccessMask = (0x0010) // file & directory
+	FILE_WRITE_PROPERTIES AccessMask = FILE_WRITE_EA
+
+	FILE_EXECUTE  AccessMask = (0x0020) // file
+	FILE_TRAVERSE AccessMask = (0x0020) // directory
+
+	FILE_DELETE_CHILD AccessMask = (0x0040) // directory
+
+	FILE_READ_ATTRIBUTES AccessMask = (0x0080) // all
+
+	FILE_WRITE_ATTRIBUTES AccessMask = (0x0100) // all
+
+	FILE_ALL_ACCESS      AccessMask = (STANDARD_RIGHTS_REQUIRED | SYNCHRONIZE | 0x1FF)
+	FILE_GENERIC_READ    AccessMask = (STANDARD_RIGHTS_READ | FILE_READ_DATA | FILE_READ_ATTRIBUTES | FILE_READ_EA | SYNCHRONIZE)
+	FILE_GENERIC_WRITE   AccessMask = (STANDARD_RIGHTS_WRITE | FILE_WRITE_DATA | FILE_WRITE_ATTRIBUTES | FILE_WRITE_EA | FILE_APPEND_DATA | SYNCHRONIZE)
+	FILE_GENERIC_EXECUTE AccessMask = (STANDARD_RIGHTS_EXECUTE | FILE_READ_ATTRIBUTES | FILE_EXECUTE | SYNCHRONIZE)
+
+	SPECIFIC_RIGHTS_ALL AccessMask = 0x0000FFFF
+
+	// Standard Access
+	// from ntseapi.h
+
+	DELETE       AccessMask = 0x0001_0000
+	READ_CONTROL AccessMask = 0x0002_0000
+	WRITE_DAC    AccessMask = 0x0004_0000
+	WRITE_OWNER  AccessMask = 0x0008_0000
+	SYNCHRONIZE  AccessMask = 0x0010_0000
+
+	STANDARD_RIGHTS_REQUIRED AccessMask = 0x000F_0000
+
+	STANDARD_RIGHTS_READ    AccessMask = READ_CONTROL
+	STANDARD_RIGHTS_WRITE   AccessMask = READ_CONTROL
+	STANDARD_RIGHTS_EXECUTE AccessMask = READ_CONTROL
+
+	STANDARD_RIGHTS_ALL AccessMask = 0x001F_0000
+)
+
+type FileShareMode uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	FILE_SHARE_NONE        FileShareMode = 0x00
+	FILE_SHARE_READ        FileShareMode = 0x01
+	FILE_SHARE_WRITE       FileShareMode = 0x02
+	FILE_SHARE_DELETE      FileShareMode = 0x04
+	FILE_SHARE_VALID_FLAGS FileShareMode = 0x07
+)
+
+type FileCreationDisposition uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	// from winbase.h
+
+	CREATE_NEW        FileCreationDisposition = 0x01
+	CREATE_ALWAYS     FileCreationDisposition = 0x02
+	OPEN_EXISTING     FileCreationDisposition = 0x03
+	OPEN_ALWAYS       FileCreationDisposition = 0x04
+	TRUNCATE_EXISTING FileCreationDisposition = 0x05
+)
+
+// CreateFile and co. take flags or attributes together as one parameter.
+// Define alias until we can use generics to allow both
+
+// https://learn.microsoft.com/en-us/windows/win32/fileio/file-attribute-constants
+type FileFlagOrAttribute uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const ( // from winnt.h
+	FILE_FLAG_WRITE_THROUGH       FileFlagOrAttribute = 0x8000_0000
+	FILE_FLAG_OVERLAPPED          FileFlagOrAttribute = 0x4000_0000
+	FILE_FLAG_NO_BUFFERING        FileFlagOrAttribute = 0x2000_0000
+	FILE_FLAG_RANDOM_ACCESS       FileFlagOrAttribute = 0x1000_0000
+	FILE_FLAG_SEQUENTIAL_SCAN     FileFlagOrAttribute = 0x0800_0000
+	FILE_FLAG_DELETE_ON_CLOSE     FileFlagOrAttribute = 0x0400_0000
+	FILE_FLAG_BACKUP_SEMANTICS    FileFlagOrAttribute = 0x0200_0000
+	FILE_FLAG_POSIX_SEMANTICS     FileFlagOrAttribute = 0x0100_0000
+	FILE_FLAG_OPEN_REPARSE_POINT  FileFlagOrAttribute = 0x0020_0000
+	FILE_FLAG_OPEN_NO_RECALL      FileFlagOrAttribute = 0x0010_0000
+	FILE_FLAG_FIRST_PIPE_INSTANCE FileFlagOrAttribute = 0x0008_0000
+)
+
+type FileSQSFlag = FileFlagOrAttribute
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const ( // from winbase.h
+	SECURITY_ANONYMOUS      FileSQSFlag = FileSQSFlag(SecurityAnonymous << 16)
+	SECURITY_IDENTIFICATION FileSQSFlag = FileSQSFlag(SecurityIdentification << 16)
+	SECURITY_IMPERSONATION  FileSQSFlag = FileSQSFlag(SecurityImpersonation << 16)
+	SECURITY_DELEGATION     FileSQSFlag = FileSQSFlag(SecurityDelegation << 16)
+
+	SECURITY_SQOS_PRESENT     FileSQSFlag = 0x00100000
+	SECURITY_VALID_SQOS_FLAGS FileSQSFlag = 0x001F0000
+)
+
+// GetFinalPathNameByHandle flags
+//
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew#parameters
+type GetFinalPathFlag uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	GetFinalPathDefaultFlag GetFinalPathFlag = 0x0
+
+	FILE_NAME_NORMALIZED GetFinalPathFlag = 0x0
+	FILE_NAME_OPENED     GetFinalPathFlag = 0x8
+
+	VOLUME_NAME_DOS  GetFinalPathFlag = 0x0
+	VOLUME_NAME_GUID GetFinalPathFlag = 0x1
+	VOLUME_NAME_NT   GetFinalPathFlag = 0x2
+	VOLUME_NAME_NONE GetFinalPathFlag = 0x4
+)
+
+// getFinalPathNameByHandle facilitates calling the Windows API GetFinalPathNameByHandle
+// with the given handle and flags. It transparently takes care of creating a buffer of the
+// correct size for the call.
+//
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew
+func GetFinalPathNameByHandle(h windows.Handle, flags GetFinalPathFlag) (string, error) {
+	b := stringbuffer.NewWString()
+	//TODO: can loop infinitely if Win32 keeps returning the same (or a larger) n?
+	for {
+		n, err := windows.GetFinalPathNameByHandle(h, b.Pointer(), b.Cap(), uint32(flags))
+		if err != nil {
+			return "", err
+		}
+		// If the buffer wasn't large enough, n will be the total size needed (including null terminator).
+		// Resize and try again.
+		if n > b.Cap() {
+			b.ResizeTo(n)
+			continue
+		}
+		// If the buffer is large enough, n will be the size not including the null terminator.
+		// Convert to a Go string and return.
+		return b.String(), nil
+	}
+}

internal/fs/fs_test.go

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+//go:build windows
+
+package fs
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+func Test_GetFinalPathNameByHandle(t *testing.T) {
+	d := t.TempDir()
+	// open f via a relative path
+	name := t.Name() + ".txt"
+	fullPath := filepath.Join(d, name)
+
+	w, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("could not get working directory: %v", err)
+	}
+	if err := os.Chdir(d); err != nil {
+		t.Fatalf("could not chdir to %s: %v", d, err)
+	}
+	defer os.Chdir(w) //nolint:errcheck
+
+	f, err := os.Create(name)
+	if err != nil {
+		t.Fatalf("could not open %s: %v", fullPath, err)
+	}
+	defer f.Close()
+
+	path, err := GetFinalPathNameByHandle(windows.Handle(f.Fd()), GetFinalPathDefaultFlag)
+	if err != nil {
+		t.Fatalf("could not get final path for %s: %v", fullPath, err)
+	}
+	if strings.EqualFold(fullPath, path) {
+		t.Fatalf("expected %s, got %s", fullPath, path)
+	}
+}

internal/fs/security.go

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+package fs
+
+// https://learn.microsoft.com/en-us/windows/win32/api/winnt/ne-winnt-security_impersonation_level
+type SecurityImpersonationLevel int32 // C default enums underlying type is `int`, which is Go `int32`
+
+// Impersonation levels
+const (
+	SecurityAnonymous      SecurityImpersonationLevel = 0
+	SecurityIdentification SecurityImpersonationLevel = 1
+	SecurityImpersonation  SecurityImpersonationLevel = 2
+	SecurityDelegation     SecurityImpersonationLevel = 3
+)