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// Copyright 2012, Jeramey Crawford <jeramey@antihe.ro>
// Copyright 2013, Jonas mg
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file.
// Package md5_crypt implements the standard Unix MD5-crypt algorithm created by
// Poul-Henning Kamp for FreeBSD.
package md5_crypt
import (
"bytes"
"crypto/md5"
"github.com/tredoe/osutil/user/crypt"
"github.com/tredoe/osutil/user/crypt/common"
)
func init() {
crypt.RegisterCrypt(crypt.MD5, New, MagicPrefix)
}
// NOTE: Cisco IOS only allows salts of length 4.
const (
MagicPrefix = "$1$"
SaltLenMin = 1 // Real minimum is 0, but that isn't useful.
SaltLenMax = 8
RoundsDefault = 1000
)
type crypter struct{ Salt common.Salt }
// New returns a new crypt.Crypter computing the MD5-crypt password hashing.
func New() crypt.Crypter {
return &crypter{GetSalt()}
}
func (c *crypter) Generate(key, salt []byte) (string, error) {
if len(salt) == 0 {
salt = c.Salt.Generate(SaltLenMax)
}
if !bytes.HasPrefix(salt, c.Salt.MagicPrefix) {
return "", common.ErrSaltPrefix
}
saltToks := bytes.Split(salt, []byte{'$'})
if len(saltToks) < 3 {
return "", common.ErrSaltFormat
} else {
salt = saltToks[2]
}
if len(salt) > 8 {
salt = salt[0:8]
}
// Compute alternate MD5 sum with input KEY, SALT, and KEY.
Alternate := md5.New()
Alternate.Write(key)
Alternate.Write(salt)
Alternate.Write(key)
AlternateSum := Alternate.Sum(nil) // 16 bytes
A := md5.New()
A.Write(key)
A.Write(c.Salt.MagicPrefix)
A.Write(salt)
// Add for any character in the key one byte of the alternate sum.
i := len(key)
for ; i > 16; i -= 16 {
A.Write(AlternateSum)
}
A.Write(AlternateSum[0:i])
// The original implementation now does something weird:
// For every 1 bit in the key, the first 0 is added to the buffer
// For every 0 bit, the first character of the key
// This does not seem to be what was intended but we have to follow this to
// be compatible.
for i = len(key); i > 0; i >>= 1 {
if (i & 1) == 0 {
A.Write(key[0:1])
} else {
A.Write([]byte{0})
}
}
Csum := A.Sum(nil)
// In fear of password crackers here comes a quite long loop which just
// processes the output of the previous round again.
// We cannot ignore this here.
for i = 0; i < RoundsDefault; i++ {
C := md5.New()
// Add key or last result.
if (i & 1) != 0 {
C.Write(key)
} else {
C.Write(Csum)
}
// Add salt for numbers not divisible by 3.
if (i % 3) != 0 {
C.Write(salt)
}
// Add key for numbers not divisible by 7.
if (i % 7) != 0 {
C.Write(key)
}
// Add key or last result.
if (i & 1) == 0 {
C.Write(key)
} else {
C.Write(Csum)
}
Csum = C.Sum(nil)
}
out := make([]byte, 0, 23+len(c.Salt.MagicPrefix)+len(salt))
out = append(out, c.Salt.MagicPrefix...)
out = append(out, salt...)
out = append(out, '$')
out = append(out, common.Base64_24Bit([]byte{
Csum[12], Csum[6], Csum[0],
Csum[13], Csum[7], Csum[1],
Csum[14], Csum[8], Csum[2],
Csum[15], Csum[9], Csum[3],
Csum[5], Csum[10], Csum[4],
Csum[11],
})...)
// Clean sensitive data.
A.Reset()
Alternate.Reset()
for i = 0; i < len(AlternateSum); i++ {
AlternateSum[i] = 0
}
return string(out), nil
}
func (c *crypter) Verify(hashedKey string, key []byte) error {
newHash, err := c.Generate(key, []byte(hashedKey))
if err != nil {
return err
}
if newHash != hashedKey {
return crypt.ErrKeyMismatch
}
return nil
}
func (c *crypter) Cost(hashedKey string) (int, error) { return RoundsDefault, nil }
func (c *crypter) SetSalt(salt common.Salt) { c.Salt = salt }
func GetSalt() common.Salt {
return common.Salt{
MagicPrefix: []byte(MagicPrefix),
SaltLenMin: SaltLenMin,
SaltLenMax: SaltLenMax,
RoundsDefault: RoundsDefault,
}
}
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