psiphon-tunnel-core/psiphon/utils.go

/*
 * Copyright (c) 2014, Psiphon Inc.
 * All rights reserved.
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package psiphon

import (
	"crypto/rand"
	"errors"
	"math/big"
)

// Contains is a helper function that returns true
// if the target string is in the list.
func Contains(list []string, target string) bool {
	for _, listItem := range list {
		if listItem == target {
			return true
		}
	}
	return false
}

// MakeSecureRandomInt is a helper function that wraps
// crypto/rand.Int.
func MakeSecureRandomInt(max int) (int, error) {
	randomInt, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
	if err != nil {
		return 0, err
	}
	return int(randomInt.Uint64()), nil
}

// MakeSecureRandomBytes is a helper function that wraps
// crypto/rand.Read.
func MakeSecureRandomBytes(length int) ([]byte, error) {
	randomBytes := make([]byte, length)
	n, err := rand.Read(randomBytes)
	if err != nil {
		return nil, err
	}
	if n != length {
		return nil, errors.New("insufficient random bytes")
	}
	return randomBytes, nil
}