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crypto: Small optimizations of BCrypt #271

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crypto: Small optimizations of BCrypt #271

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98 changes: 51 additions & 47 deletions bcrypt/bcrypt.go
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Original file line number Diff line number Diff line change
Expand Up @@ -63,17 +63,6 @@ const (
minHashSize = 59
)

// magicCipherData is an IV for the 64 Blowfish encryption calls in
// bcrypt(). It's the string "OrpheanBeholderScryDoubt" in big-endian bytes.
var magicCipherData = []byte{
0x4f, 0x72, 0x70, 0x68,
0x65, 0x61, 0x6e, 0x42,
0x65, 0x68, 0x6f, 0x6c,
0x64, 0x65, 0x72, 0x53,
0x63, 0x72, 0x79, 0x44,
0x6f, 0x75, 0x62, 0x74,
}

type hashed struct {
hash []byte
salt []byte
Expand Down Expand Up @@ -111,6 +100,13 @@ func CompareHashAndPassword(hashedPassword, password []byte) error {
return err
}

// This is simply put here instead of in newfromhash only to avoid failed test
// Altough failed test can be easily altered
p.salt, err = base64Decode(p.salt)
if err != nil {
return err
}

otherHash, err := bcrypt(password, p.cost, p.salt)
if err != nil {
return err
Expand Down Expand Up @@ -156,12 +152,14 @@ func newFromPassword(password []byte, cost int) (*hashed, error) {
return nil, err
}

p.salt = base64Encode(unencodedSalt)
hash, err := bcrypt(password, p.cost, p.salt)
hash, err := bcrypt(password, p.cost, unencodedSalt)
if err != nil {
return nil, err
}

p.salt = base64Encode(unencodedSalt)
p.hash = hash

return p, err
}

Expand All @@ -170,32 +168,38 @@ func newFromHash(hashedSecret []byte) (*hashed, error) {
return nil, ErrHashTooShort
}
p := new(hashed)
n, err := p.decodeVersion(hashedSecret)
err := p.decodeVersion(&hashedSecret)
if err != nil {
return nil, err
}
hashedSecret = hashedSecret[n:]
n, err = p.decodeCost(hashedSecret)

err = p.decodeCost(&hashedSecret)
if err != nil {
return nil, err
}
hashedSecret = hashedSecret[n:]

// The "+2" is here because we'll have to append at most 2 '=' to the salt
// when base64 decoding it in expensiveBlowfishSetup().
p.salt = make([]byte, encodedSaltSize, encodedSaltSize+2)
copy(p.salt, hashedSecret[:encodedSaltSize])

hashedSecret = hashedSecret[encodedSaltSize:]
p.hash = make([]byte, len(hashedSecret))
copy(p.hash, hashedSecret)
p.hash = make([]byte, encodedHashSize)
copy(p.hash, hashedSecret[encodedSaltSize:])

return p, nil
}

func bcrypt(password []byte, cost int, salt []byte) ([]byte, error) {
cipherData := make([]byte, len(magicCipherData))
copy(cipherData, magicCipherData)
// magicCipherData is an IV for the 64 Blowfish encryption calls in
// bcrypt(). It's the string "OrpheanBeholderScryDoubt" in big-endian bytes.
var magicCipherData = []byte{
0x4f, 0x72, 0x70, 0x68,
0x65, 0x61, 0x6e, 0x42,
0x65, 0x68, 0x6f, 0x6c,
0x64, 0x65, 0x72, 0x53,
0x63, 0x72, 0x79, 0x44,
0x6f, 0x75, 0x62, 0x74,
}

c, err := expensiveBlowfishSetup(password, uint32(cost), salt)
if err != nil {
Expand All @@ -204,28 +208,23 @@ func bcrypt(password []byte, cost int, salt []byte) ([]byte, error) {

for i := 0; i < 24; i += 8 {
for j := 0; j < 64; j++ {
c.Encrypt(cipherData[i:i+8], cipherData[i:i+8])
c.Encrypt(magicCipherData[i:i+8], magicCipherData[i:i+8])
}
}

// Bug compatibility with C bcrypt implementations. We only encode 23 of
// the 24 bytes encrypted.
hsh := base64Encode(cipherData[:maxCryptedHashSize])
hsh := base64Encode(magicCipherData[:maxCryptedHashSize])
return hsh, nil
}

func expensiveBlowfishSetup(key []byte, cost uint32, salt []byte) (*blowfish.Cipher, error) {
csalt, err := base64Decode(salt)
if err != nil {
return nil, err
}

// Bug compatibility with C bcrypt implementations. They use the trailing
// NULL in the key string during expansion.
// We copy the key to prevent changing the underlying array.
ckey := append(key[:len(key):len(key)], 0)

c, err := blowfish.NewSaltedCipher(ckey, csalt)
c, err := blowfish.NewSaltedCipher(ckey, salt)
if err != nil {
return nil, err
}
Expand All @@ -234,7 +233,7 @@ func expensiveBlowfishSetup(key []byte, cost uint32, salt []byte) (*blowfish.Cip
rounds = 1 << cost
for i = 0; i < rounds; i++ {
blowfish.ExpandKey(ckey, c)
blowfish.ExpandKey(csalt, c)
blowfish.ExpandKey(salt, c)
}

return c, nil
Expand Down Expand Up @@ -262,34 +261,39 @@ func (p *hashed) Hash() []byte {
return arr[:n]
}

func (p *hashed) decodeVersion(sbytes []byte) (int, error) {
if sbytes[0] != '$' {
return -1, InvalidHashPrefixError(sbytes[0])
func (p *hashed) decodeVersion(sbytes *[]byte) error {
if (*sbytes)[0] != '$' {
return InvalidHashPrefixError((*sbytes)[0])
}
if sbytes[1] > majorVersion {
return -1, HashVersionTooNewError(sbytes[1])
if (*sbytes)[1] > majorVersion {
return HashVersionTooNewError((*sbytes)[1])
}
p.major = sbytes[1]
p.major = (*sbytes)[1]
n := 3
if sbytes[2] != '$' {
p.minor = sbytes[2]
if (*sbytes)[2] != '$' {
p.minor = (*sbytes)[2]
n++
}
return n, nil

(*sbytes) = (*sbytes)[n:]

return nil
}

// sbytes should begin where decodeVersion left off.
func (p *hashed) decodeCost(sbytes []byte) (int, error) {
cost, err := strconv.Atoi(string(sbytes[0:2]))
func (p *hashed) decodeCost(sbytes *[]byte) (err error) {
p.cost, err = strconv.Atoi(string((*sbytes)[0:2]))
if err != nil {
return -1, err
return
}
err = checkCost(cost)

err = checkCost(p.cost)
if err != nil {
return -1, err
return
}
p.cost = cost
return 3, nil

(*sbytes) = (*sbytes)[3:]
return
}

func (p *hashed) String() string {
Expand Down
6 changes: 3 additions & 3 deletions bcrypt/bcrypt_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ func TestBcryptingIsEasy(t *testing.T) {

func TestBcryptingIsCorrect(t *testing.T) {
pass := []byte("allmine")
salt := []byte("XajjQvNhvvRt5GSeFk1xFe")
salt := []byte{101, 201, 101, 75, 19, 227, 199, 20, 239, 236, 133, 32, 30, 109, 243, 30}
expectedHash := []byte("$2a$10$XajjQvNhvvRt5GSeFk1xFeyqRrsxkhBkUiQeg0dt.wU1qD4aFDcga")

hash, err := bcrypt(pass, 10, salt)
Expand All @@ -55,15 +55,15 @@ func TestBcryptingIsCorrect(t *testing.T) {

func TestVeryShortPasswords(t *testing.T) {
key := []byte("k")
salt := []byte("XajjQvNhvvRt5GSeFk1xFe")
salt := []byte{101, 201, 101, 75, 19, 227, 199, 20, 239, 236, 133, 32, 30, 109, 243, 30}
_, err := bcrypt(key, 10, salt)
if err != nil {
t.Errorf("One byte key resulted in error: %s", err)
}
}

func TestTooLongPasswordsWork(t *testing.T) {
salt := []byte("XajjQvNhvvRt5GSeFk1xFe")
salt := []byte{101, 201, 101, 75, 19, 227, 199, 20, 239, 236, 133, 32, 30, 109, 243, 30}
// One byte over the usual 56 byte limit that blowfish has
tooLongPass := []byte("012345678901234567890123456789012345678901234567890123456")
tooLongExpected := []byte("$2a$10$XajjQvNhvvRt5GSeFk1xFe5l47dONXg781AmZtd869sO8zfsHuw7C")
Expand Down