x/crypto/ssh/terminal: ensure windows MakeRaw returns previous state

The MakeRaw method should be returning the original state so that
it can be restored.  However, the current implementation is returning
the new, "raw" state.

Fixes golang/go#15155

Change-Id: I8e0b87229b7577544e1118fa4b95664d3a9cf5da
Reviewed-on: https://go-review.googlesource.com/21612
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

terminal_test.go

@@ -6,6 +6,7 @@ package terminal
 
 import (
 	"io"
+	"os"
 	"testing"
 )
 
@@ -267,3 +268,24 @@ func TestTerminalSetSize(t *testing.T) {
 		}
 	}
 }
+
+func TestMakeRawState(t *testing.T) {
+	fd := int(os.Stdout.Fd())
+	if !IsTerminal(fd) {
+		t.Skip("stdout is not a terminal; skipping test")
+	}
+
+	st, err := GetState(fd)
+	if err != nil {
+		t.Fatalf("failed to get terminal state from GetState: %s", err)
+	}
+	defer Restore(fd, st)
+	raw, err := MakeRaw(fd)
+	if err != nil {
+		t.Fatalf("failed to get terminal state from MakeRaw: %s", err)
+	}
+
+	if *st != *raw {
+		t.Errorf("states do not match; was %v, expected %v", raw, st)
+	}
+}

util_windows.go

@@ -87,8 +87,8 @@ func MakeRaw(fd int) (*State, error) {
 	if e != 0 {
 		return nil, error(e)
 	}
-	st &^= (enableEchoInput | enableProcessedInput | enableLineInput | enableProcessedOutput)
-	_, _, e = syscall.Syscall(procSetConsoleMode.Addr(), 2, uintptr(fd), uintptr(st), 0)
+	raw := st &^ (enableEchoInput | enableProcessedInput | enableLineInput | enableProcessedOutput)
+	_, _, e = syscall.Syscall(procSetConsoleMode.Addr(), 2, uintptr(fd), uintptr(raw), 0)
 	if e != 0 {
 		return nil, error(e)
 	}