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>

ssh/terminal/terminal_test.go

diff --git a/ssh/terminal/terminal_test.go b/ssh/terminal/terminal_test.go
index a663fe4..6bdefb4 100644
--- a/ssh/terminal/terminal_test.go
+++ b/ssh/terminal/terminal_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"io"
+	"os"
 	"testing"
 )
 
@@ -267,3 +268,24 @@
 		}
 	}
 }
+
+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)
+	}
+}

ssh/terminal/util_windows.go

diff --git a/ssh/terminal/util_windows.go b/ssh/terminal/util_windows.go
index 2dd6c3d..ae9fa9e 100644
--- a/ssh/terminal/util_windows.go
+++ b/ssh/terminal/util_windows.go
@@ -87,8 +87,8 @@
 	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)
 	}