utils.go

// Copyright 2017 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// go-ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"strings"

	"github.com/ethereum/go-ethereum/cmd/utils"
	"github.com/ethereum/go-ethereum/console"
	"github.com/ethereum/go-ethereum/crypto"
	"gopkg.in/urfave/cli.v1"
)

// promptPassphrase prompts the user for a passphrase.  Set confirmation to true
// to require the user to confirm the passphrase.
func promptPassphrase(confirmation bool) string {
	passphrase, err := console.Stdin.PromptPassword("Password: ")
	if err != nil {
		utils.Fatalf("Failed to read password: %v", err)
	}

	if confirmation {
		confirm, err := console.Stdin.PromptPassword("Repeat password: ")
		if err != nil {
			utils.Fatalf("Failed to read password confirmation: %v", err)
		}
		if passphrase != confirm {
			utils.Fatalf("Passwords do not match")
		}
	}

	return passphrase
}

// getPassphrase obtains a passphrase given by the user.  It first checks the
// --passfile command line flag and ultimately prompts the user for a
// passphrase.
func getPassphrase(ctx *cli.Context) string {
	// Look for the --passwordfile flag.
	passphraseFile := ctx.String(passphraseFlag.Name)
	if passphraseFile != "" {
		content, err := ioutil.ReadFile(passphraseFile)
		if err != nil {
			utils.Fatalf("Failed to read password file '%s': %v",
				passphraseFile, err)
		}
		return strings.TrimRight(string(content), "\r\n")
	}

	// Otherwise prompt the user for the passphrase.
	return promptPassphrase(false)
}

// signHash is a helper function that calculates a hash for the given message
// that can be safely used to calculate a signature from.
//
// The hash is calulcated as
//   keccak256("\x19Ethereum Signed Message:\n"${message length}${message}).
//
// This gives context to the signed message and prevents signing of transactions.
func signHash(data []byte) []byte {
	msg := fmt.Sprintf("\x19Ethereum Signed Message:\n%d%s", len(data), data)
	return crypto.Keccak256([]byte(msg))
}

// mustPrintJSON prints the JSON encoding of the given object and
// exits the program with an error message when the marshaling fails.
func mustPrintJSON(jsonObject interface{}) {
	str, err := json.MarshalIndent(jsonObject, "", "  ")
	if err != nil {
		utils.Fatalf("Failed to marshal JSON object: %v", err)
	}
	fmt.Println(string(str))
}