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295 lines
7.8 KiB
Go
295 lines
7.8 KiB
Go
// Copyright 2011 The Go Authors. 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 implements Provos and Mazières's bcrypt adaptive hashing
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// algorithm. See http://www.usenix.org/event/usenix99/provos/provos.pdf
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package bcrypt // import "golang.org/x/crypto/bcrypt"
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// The code is a port of Provos and Mazières's C implementation.
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import (
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"crypto/rand"
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"crypto/subtle"
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"errors"
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"fmt"
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"io"
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"strconv"
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"golang.org/x/crypto/blowfish"
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)
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const (
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MinCost int = 4 // the minimum allowable cost as passed in to GenerateFromPassword
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MaxCost int = 31 // the maximum allowable cost as passed in to GenerateFromPassword
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DefaultCost int = 10 // the cost that will actually be set if a cost below MinCost is passed into GenerateFromPassword
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)
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// The error returned from CompareHashAndPassword when a password and hash do
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// not match.
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var ErrMismatchedHashAndPassword = errors.New("crypto/bcrypt: hashedPassword is not the hash of the given password")
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// The error returned from CompareHashAndPassword when a hash is too short to
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// be a bcrypt hash.
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var ErrHashTooShort = errors.New("crypto/bcrypt: hashedSecret too short to be a bcrypted password")
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// The error returned from CompareHashAndPassword when a hash was created with
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// a bcrypt algorithm newer than this implementation.
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type HashVersionTooNewError byte
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func (hv HashVersionTooNewError) Error() string {
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return fmt.Sprintf("crypto/bcrypt: bcrypt algorithm version '%c' requested is newer than current version '%c'", byte(hv), majorVersion)
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}
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// The error returned from CompareHashAndPassword when a hash starts with something other than '$'
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type InvalidHashPrefixError byte
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func (ih InvalidHashPrefixError) Error() string {
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return fmt.Sprintf("crypto/bcrypt: bcrypt hashes must start with '$', but hashedSecret started with '%c'", byte(ih))
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}
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type InvalidCostError int
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func (ic InvalidCostError) Error() string {
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return fmt.Sprintf("crypto/bcrypt: cost %d is outside allowed range (%d,%d)", int(ic), int(MinCost), int(MaxCost))
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}
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const (
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majorVersion = '2'
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minorVersion = 'a'
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maxSaltSize = 16
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maxCryptedHashSize = 23
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encodedSaltSize = 22
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encodedHashSize = 31
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minHashSize = 59
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)
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// magicCipherData is an IV for the 64 Blowfish encryption calls in
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// bcrypt(). It's the string "OrpheanBeholderScryDoubt" in big-endian bytes.
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var magicCipherData = []byte{
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0x4f, 0x72, 0x70, 0x68,
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0x65, 0x61, 0x6e, 0x42,
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0x65, 0x68, 0x6f, 0x6c,
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0x64, 0x65, 0x72, 0x53,
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0x63, 0x72, 0x79, 0x44,
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0x6f, 0x75, 0x62, 0x74,
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}
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type hashed struct {
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hash []byte
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salt []byte
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cost int // allowed range is MinCost to MaxCost
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major byte
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minor byte
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}
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// GenerateFromPassword returns the bcrypt hash of the password at the given
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// cost. If the cost given is less than MinCost, the cost will be set to
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// DefaultCost, instead. Use CompareHashAndPassword, as defined in this package,
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// to compare the returned hashed password with its cleartext version.
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func GenerateFromPassword(password []byte, cost int) ([]byte, error) {
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p, err := newFromPassword(password, cost)
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if err != nil {
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return nil, err
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}
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return p.Hash(), nil
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}
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// CompareHashAndPassword compares a bcrypt hashed password with its possible
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// plaintext equivalent. Returns nil on success, or an error on failure.
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func CompareHashAndPassword(hashedPassword, password []byte) error {
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p, err := newFromHash(hashedPassword)
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if err != nil {
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return err
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}
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otherHash, err := bcrypt(password, p.cost, p.salt)
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if err != nil {
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return err
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}
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otherP := &hashed{otherHash, p.salt, p.cost, p.major, p.minor}
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if subtle.ConstantTimeCompare(p.Hash(), otherP.Hash()) == 1 {
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return nil
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}
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return ErrMismatchedHashAndPassword
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}
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// Cost returns the hashing cost used to create the given hashed
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// password. When, in the future, the hashing cost of a password system needs
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// to be increased in order to adjust for greater computational power, this
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// function allows one to establish which passwords need to be updated.
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func Cost(hashedPassword []byte) (int, error) {
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p, err := newFromHash(hashedPassword)
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if err != nil {
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return 0, err
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}
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return p.cost, nil
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}
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func newFromPassword(password []byte, cost int) (*hashed, error) {
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if cost < MinCost {
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cost = DefaultCost
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}
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p := new(hashed)
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p.major = majorVersion
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p.minor = minorVersion
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err := checkCost(cost)
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if err != nil {
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return nil, err
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}
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p.cost = cost
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unencodedSalt := make([]byte, maxSaltSize)
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_, err = io.ReadFull(rand.Reader, unencodedSalt)
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if err != nil {
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return nil, err
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}
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p.salt = base64Encode(unencodedSalt)
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hash, err := bcrypt(password, p.cost, p.salt)
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if err != nil {
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return nil, err
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}
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p.hash = hash
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return p, err
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}
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func newFromHash(hashedSecret []byte) (*hashed, error) {
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if len(hashedSecret) < minHashSize {
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return nil, ErrHashTooShort
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}
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p := new(hashed)
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n, err := p.decodeVersion(hashedSecret)
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if err != nil {
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return nil, err
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}
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hashedSecret = hashedSecret[n:]
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n, err = p.decodeCost(hashedSecret)
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if err != nil {
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return nil, err
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}
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hashedSecret = hashedSecret[n:]
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// The "+2" is here because we'll have to append at most 2 '=' to the salt
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// when base64 decoding it in expensiveBlowfishSetup().
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p.salt = make([]byte, encodedSaltSize, encodedSaltSize+2)
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copy(p.salt, hashedSecret[:encodedSaltSize])
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hashedSecret = hashedSecret[encodedSaltSize:]
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p.hash = make([]byte, len(hashedSecret))
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copy(p.hash, hashedSecret)
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return p, nil
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}
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func bcrypt(password []byte, cost int, salt []byte) ([]byte, error) {
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cipherData := make([]byte, len(magicCipherData))
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copy(cipherData, magicCipherData)
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c, err := expensiveBlowfishSetup(password, uint32(cost), salt)
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if err != nil {
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return nil, err
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}
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for i := 0; i < 24; i += 8 {
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for j := 0; j < 64; j++ {
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c.Encrypt(cipherData[i:i+8], cipherData[i:i+8])
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}
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}
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// Bug compatibility with C bcrypt implementations. We only encode 23 of
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// the 24 bytes encrypted.
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hsh := base64Encode(cipherData[:maxCryptedHashSize])
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return hsh, nil
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}
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func expensiveBlowfishSetup(key []byte, cost uint32, salt []byte) (*blowfish.Cipher, error) {
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csalt, err := base64Decode(salt)
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if err != nil {
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return nil, err
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}
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// Bug compatibility with C bcrypt implementations. They use the trailing
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// NULL in the key string during expansion.
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// We copy the key to prevent changing the underlying array.
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ckey := append(key[:len(key):len(key)], 0)
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c, err := blowfish.NewSaltedCipher(ckey, csalt)
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if err != nil {
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return nil, err
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}
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var i, rounds uint64
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rounds = 1 << cost
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for i = 0; i < rounds; i++ {
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blowfish.ExpandKey(ckey, c)
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blowfish.ExpandKey(csalt, c)
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}
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return c, nil
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}
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func (p *hashed) Hash() []byte {
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arr := make([]byte, 60)
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arr[0] = '$'
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arr[1] = p.major
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n := 2
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if p.minor != 0 {
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arr[2] = p.minor
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n = 3
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}
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arr[n] = '$'
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n++
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copy(arr[n:], []byte(fmt.Sprintf("%02d", p.cost)))
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n += 2
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arr[n] = '$'
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n++
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copy(arr[n:], p.salt)
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n += encodedSaltSize
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copy(arr[n:], p.hash)
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n += encodedHashSize
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return arr[:n]
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}
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func (p *hashed) decodeVersion(sbytes []byte) (int, error) {
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if sbytes[0] != '$' {
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return -1, InvalidHashPrefixError(sbytes[0])
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}
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if sbytes[1] > majorVersion {
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return -1, HashVersionTooNewError(sbytes[1])
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}
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p.major = sbytes[1]
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n := 3
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if sbytes[2] != '$' {
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p.minor = sbytes[2]
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n++
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}
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return n, nil
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}
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// sbytes should begin where decodeVersion left off.
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func (p *hashed) decodeCost(sbytes []byte) (int, error) {
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cost, err := strconv.Atoi(string(sbytes[0:2]))
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if err != nil {
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return -1, err
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}
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err = checkCost(cost)
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if err != nil {
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return -1, err
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}
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p.cost = cost
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return 3, nil
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}
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func (p *hashed) String() string {
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return fmt.Sprintf("&{hash: %#v, salt: %#v, cost: %d, major: %c, minor: %c}", string(p.hash), p.salt, p.cost, p.major, p.minor)
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}
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func checkCost(cost int) error {
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if cost < MinCost || cost > MaxCost {
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return InvalidCostError(cost)
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}
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return nil
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}
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