init

go.mod

@@ -0,0 +1,3 @@
+module github.com/fumiama/go-hide-param
+
+go 1.16

unix.go

@@ -0,0 +1,15 @@
+// +build !windows
+
+package gohideparam
+
+import (
+	"os"
+	"unsafe"
+)
+
+func Hide(position uint) {
+	pwdstr := (*[2]uintptr)(unsafe.Pointer(&os.Args[position]))
+	for i := 0; i < len(os.Args[3]); i++ {
+		*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(pwdstr)) + uintptr(i))) = '*'
+	}
+}

win.go

@@ -0,0 +1,98 @@
+// +build windows
+
+package gohideparam
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// Slice is the runtime representation of a slice.
+// It cannot be used safely or portably and its representation may
+// change in a later release.
+//
+// Unlike reflect.SliceHeader, its Data field is sufficient to guarantee the
+// data it references will not be garbage collected.
+type Slice struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+// readNextArg splits command line string cmd into next
+// argument and command line remainder.
+func readNextArg(cmd *[]uint16, is2erase bool) {
+	var inquote bool
+	var nslash int
+	for ; len(*cmd) > 0; (*cmd) = (*cmd)[1:] {
+		switch (*cmd)[0] {
+		case uint16(' '), uint16('\t'):
+			if !inquote {
+				return
+			}
+		case uint16('"'):
+			if nslash%2 == 0 {
+				// use "Prior to 2008" rule from
+				// http://daviddeley.com/autohotkey/parameters/parameters.htm
+				// section 5.2 to deal with double double quotes
+				if inquote && len(*cmd) > 1 && (*cmd)[1] == uint16('"') {
+					*cmd = (*cmd)[1:]
+				}
+				inquote = !inquote
+			}
+			nslash = 0
+			continue
+		case uint16('\\'):
+			nslash++
+			if is2erase {
+				(*cmd)[0] = uint16('*')
+			}
+			continue
+		default:
+			if is2erase {
+				(*cmd)[0] = uint16('*')
+			}
+		}
+		nslash = 0
+	}
+}
+
+func eraseCommandLine(cmd *[]uint16, pos uint) {
+	var p uint
+	for len(*cmd) > 0 && p <= pos {
+		if (*cmd)[0] == uint16(' ') || (*cmd)[0] == uint16('\t') {
+			(*cmd) = (*cmd)[1:]
+			continue
+		}
+		readNextArg(cmd, p == pos)
+		p++
+	}
+}
+
+func utf16PtrToSlice(p *uint16) []uint16 {
+	if p == nil {
+		return nil
+	}
+	// Find NUL terminator.
+	end := unsafe.Pointer(p)
+	n := 0
+	for *(*uint16)(end) != 0 {
+		end = unsafe.Pointer(uintptr(end) + unsafe.Sizeof(*p))
+		n++
+	}
+	// Turn *uint16 into []uint16.
+	var s []uint16
+	hdr := (*Slice)(unsafe.Pointer(&s))
+	hdr.Data = unsafe.Pointer(p)
+	hdr.Cap = n
+	hdr.Len = n
+	return s
+}
+
+func Hide(position uint) {
+	if position < uint(len(os.Args)) {
+		cmd := utf16PtrToSlice(syscall.GetCommandLine())
+		eraseCommandLine(&cmd, position)
+	}
+}