98 lines
2.7 KiB
Go
98 lines
2.7 KiB
Go
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// Copyright 2014 Dmitry Chestnykh. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package bcrypt_pbkdf implements password-based key derivation function based
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// on bcrypt compatible with bcrypt_pbkdf(3) from OpenBSD.
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package bcrypt_pbkdf
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import (
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"crypto/sha512"
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"errors"
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// NOTE! Requires blowfish package version from Aug 1, 2014 or later.
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// Will produce incorrect results if the package is older.
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// See commit message for details: http://goo.gl/wx6g8O
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"golang.org/x/crypto/blowfish"
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)
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// Key derives a key from the password, salt and rounds count, returning a
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// []byte of length keyLen that can be used as cryptographic key.
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//
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// Remember to get a good random salt of at least 16 bytes. Using a higher
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// rounds count will increase the cost of an exhaustive search but will also
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// make derivation proportionally slower.
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func Key(password, salt []byte, rounds, keyLen int) ([]byte, error) {
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if rounds < 1 {
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return nil, errors.New("bcrypt_pbkdf: number of rounds is too small")
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}
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if len(password) == 0 {
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return nil, errors.New("bcrypt_pbkdf: empty password")
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}
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if len(salt) == 0 || len(salt) > 1<<20 {
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return nil, errors.New("bcrypt_pbkdf: bad salt length")
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}
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if keyLen > 1024 {
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return nil, errors.New("bcrypt_pbkdf: keyLen is too large")
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}
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var shapass, shasalt [sha512.Size]byte
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var out, tmp [32]byte
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var cnt [4]byte
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numBlocks := (keyLen + len(out) - 1) / len(out)
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key := make([]byte, numBlocks*len(out))
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h := sha512.New()
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h.Write(password)
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h.Sum(shapass[:0])
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for block := 1; block <= numBlocks; block++ {
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h.Reset()
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h.Write(salt)
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cnt[0] = byte(block >> 24)
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cnt[1] = byte(block >> 16)
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cnt[2] = byte(block >> 8)
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cnt[3] = byte(block)
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h.Write(cnt[:])
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bcryptHash(tmp[:], shapass[:], h.Sum(shasalt[:0]))
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copy(out[:], tmp[:])
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for i := 2; i <= rounds; i++ {
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h.Reset()
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h.Write(tmp[:])
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bcryptHash(tmp[:], shapass[:], h.Sum(shasalt[:0]))
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for j := 0; j < len(out); j++ {
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out[j] ^= tmp[j]
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}
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}
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for i, v := range out {
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key[i*numBlocks+(block-1)] = v
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}
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}
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return key[:keyLen], nil
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}
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var magic = []byte("OxychromaticBlowfishSwatDynamite")
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func bcryptHash(out, shapass, shasalt []byte) {
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c, err := blowfish.NewSaltedCipher(shapass, shasalt)
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if err != nil {
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panic(err)
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}
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for i := 0; i < 64; i++ {
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blowfish.ExpandKey(shasalt, c)
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blowfish.ExpandKey(shapass, c)
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}
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copy(out[:], magic)
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for i := 0; i < 32; i += 8 {
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for j := 0; j < 64; j++ {
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c.Encrypt(out[i:i+8], out[i:i+8])
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}
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}
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// Swap bytes due to different endianness.
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for i := 0; i < 32; i += 4 {
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out[i+3], out[i+2], out[i+1], out[i] = out[i], out[i+1], out[i+2], out[i+3]
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}
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}
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