add prompt

Signed-off-by: Jess Frazelle <jess@mesosphere.com>

rootfs_ops.go

@@ -1,16 +1,30 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"encoding/base64"
+	"fmt"
+	"io"
 	"os"
 
 	"github.com/docker/docker/pkg/archive"
+	"github.com/docker/docker/pkg/term"
 	"github.com/jfrazelle/binctr/cryptar"
 	"github.com/opencontainers/runtime-spec/specs-go"
 )
 
-func unpackRootfs(spec *specs.Spec, keyin string) error {
+func unpackRootfs(spec *specs.Spec, keyin string) (err error) {
+	fmt.Fprintf(os.Stdout, "Hello.\n")
+	fmt.Fprintf(os.Stdout, "Let's play Global Thermonuclear War.\n")
+
+	if keyin == "" {
+		keyin, err = promptPasskey()
+		if err != nil {
+			return err
+		}
+	}
+
 	key, err := base64.StdEncoding.DecodeString(keyin)
 	if err != nil {
 		return err
@@ -32,3 +46,30 @@ func unpackRootfs(spec *specs.Spec, keyin string) error {
 
 	return nil
 }
+
+// prompt for passkey
+func promptPasskey() (string, error) {
+	inFd, _ := term.GetFdInfo(os.Stdin)
+	oldState, err := term.SaveState(inFd)
+	if err != nil {
+		return "", err
+	}
+	fmt.Fprintf(os.Stdout, "Key: ")
+	term.DisableEcho(inFd, oldState)
+
+	keyin := readInput(os.Stdin, os.Stdout)
+	fmt.Fprint(os.Stdout, "\n")
+
+	term.RestoreTerminal(inFd, oldState)
+	return keyin, nil
+}
+
+func readInput(in io.Reader, out io.Writer) string {
+	reader := bufio.NewReader(in)
+	line, _, err := reader.ReadLine()
+	if err != nil {
+		fmt.Fprintln(out, err.Error())
+		os.Exit(1)
+	}
+	return string(line)
+}