shamirs-cli.go

package main

import (
	"fmt"
	"flag"
	"bufio"
	"os"
	"encoding/hex"

	log "github.com/sirupsen/logrus"
	"github.com/hashicorp/vault/shamir"
)

func main() {
	var split bool
	var combine bool
	var str string
	var n int
	var m int

	flag.BoolVar(&split, "split", false, "shard a string")
	flag.BoolVar(&combine, "combine", false, "combine shards to reproduce a string")
	flag.StringVar(&str, "string", "", "string to shard")
	flag.IntVar(&n, "n", 0, "number of shards required to rebuild secret")
	flag.IntVar(&m, "m", 0, "total number of shards to generate")
	flag.Parse()

	if split && combine {
		log.Fatal("cannot split and combine at the same time, doesn't make sense")
	}
	if !split && !combine {
		log.Fatal("please choose to either split or combine")
	}

	if split {
		if str == "" {
			log.Fatal("can't split an empty string, please provide a string argument")
		}
		shards, err := shamir.Split([]byte(str), m, n)
		if err != nil {
			log.Fatal("error creating shards: " + err.Error())
		}
		for _, shard := range shards {
			shardStr := hex.EncodeToString(shard)
			fmt.Println(shardStr)
		}
	} else if combine {
		parts := make([][]byte, 0)
		scanner := bufio.NewScanner(os.Stdin)
		recovered := false
		fmt.Println("Provide shards one at a time:")
		for !recovered {
			fmt.Print("> ")
			scanner.Scan() 
			bytes, err := hex.DecodeString(scanner.Text())
			if err != nil {
				log.Error("error decoding string: " + err.Error())
				log.Error("skipping")
			} else {
				parts = append(parts, bytes)
				str, err := shamir.Combine(parts)
				if err != nil {
					continue
				} else {
					fmt.Println(string(str))
					recovered = true
				}
			}
		}
	}
}