passgen.go

package main

import (
	"bufio"
	"code.google.com/p/go.crypto/pbkdf2"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"github.com/atotto/clipboard"
	"github.com/howeyc/gopass"
	"os"
)

const (
	pbkdf2Rounds int = 100000
	outputBytes  int = 15
)

func main() {
	masterHash := getMasterHash()

	for {
		id := getId()
		if len(id) == 0 {
			break
		}

		password := generatePassword(masterHash, id)

		clipboard.WriteAll(base64.StdEncoding.EncodeToString(password))
		fmt.Printf("Password copied to clipboard.\n")

		clear(password)
	}

	clear(masterHash)
}

func getMasterHash() []byte {
	hasher := sha256.New()

	fmt.Printf("Master password: ")
	hasher.Write(gopass.GetPasswd())
	masterHash := hasher.Sum(nil)

	fmt.Printf("Checksum: -> " + base64.StdEncoding.EncodeToString(masterHash[:3]) + " <-\n")

	return masterHash
}

func getId() []byte {
	bio := bufio.NewReader(os.Stdin)

	fmt.Printf("Get password for ID (empty to quit): ")
	id, err := bio.ReadBytes('\n')
	check(err)

	return id[:len(id)-1] // remove '\n' from the end
}

func generatePassword(masterHash, id []byte) []byte {
	hasher := sha256.New()
	hasher.Write(id)
	idHash := hasher.Sum(nil)

	return pbkdf2.Key(masterHash, idHash, pbkdf2Rounds, outputBytes, sha256.New)
}

func check(e error) {
	if e != nil {
		panic(e)
	}
}

func clear(b []byte) {
	for i := 0; i < len(b); i++ {
		b[i] = 0
	}
}