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// 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 crypt provides interface for password crypt functions and collects
// common constants.
package crypt
import (
"errors"
"strings"
"github.com/tredoe/osutil/user/crypt/common"
)
var ErrKeyMismatch = errors.New("hashed value is not the hash of the given password")
// Crypter is the common interface implemented by all crypt functions.
type Crypter interface {
// Generate performs the hashing algorithm, returning a full hash suitable
// for storage and later password verification.
//
// If the salt is empty, a randomly-generated salt will be generated with a
// length of SaltLenMax and number RoundsDefault of rounds.
//
// Any error only can be got when the salt argument is not empty.
Generate(key, salt []byte) (string, error)
// Verify compares a hashed key with its possible key equivalent.
// Returns nil on success, or an error on failure; if the hashed key is
// diffrent, the error is "ErrKeyMismatch".
Verify(hashedKey string, key []byte) error
// Cost returns the hashing cost (in rounds) used to create the given hashed
// key.
//
// When, in the future, the hashing cost of a key needs to be increased in
// order to adjust for greater computational power, this function allows one
// to establish which keys need to be updated.
//
// The algorithms based in MD5-crypt use a fixed value of rounds.
Cost(hashedKey string) (int, error)
// SetSalt sets a different salt. It is used to easily create derivated
// algorithms, i.e. "apr1_crypt" from "md5_crypt".
SetSalt(salt common.Salt)
}
// Crypt identifies a crypt function that is implemented in another package.
type Crypt uint
const (
APR1 Crypt = iota + 1 // import "github.com/tredoe/osutil/user/crypt/apr1_crypt"
MD5 // import "github.com/tredoe/osutil/user/crypt/md5_crypt"
SHA256 // import "github.com/tredoe/osutil/user/crypt/sha256_crypt"
SHA512 // import "github.com/tredoe/osutil/user/crypt/sha512_crypt"
maxCrypt
)
var cryptPrefixes = make([]string, maxCrypt)
var crypts = make([]func() Crypter, maxCrypt)
// RegisterCrypt registers a function that returns a new instance of the given
// crypt function. This is intended to be called from the init function in
// packages that implement crypt functions.
func RegisterCrypt(c Crypt, f func() Crypter, prefix string) {
if c >= maxCrypt {
panic("crypt: RegisterHash of unknown crypt function")
}
crypts[c] = f
cryptPrefixes[c] = prefix
}
// New returns a new crypter.
func New(c Crypt) Crypter {
f := crypts[c]
if f != nil {
return f()
}
panic("crypt: requested crypt function is unavailable")
}
// NewFromHash returns a new Crypter using the prefix in the given hashed key.
func NewFromHash(hashedKey string) Crypter {
var f func() Crypter
if strings.HasPrefix(hashedKey, cryptPrefixes[SHA512]) {
f = crypts[SHA512]
} else if strings.HasPrefix(hashedKey, cryptPrefixes[SHA256]) {
f = crypts[SHA256]
} else if strings.HasPrefix(hashedKey, cryptPrefixes[MD5]) {
f = crypts[MD5]
} else if strings.HasPrefix(hashedKey, cryptPrefixes[APR1]) {
f = crypts[APR1]
} else {
toks := strings.SplitN(hashedKey, "$", 3)
prefix := "$" + toks[1] + "$"
panic("crypt: unknown cryp function from prefix: " + prefix)
}
if f != nil {
return f()
}
panic("crypt: requested cryp function is unavailable")
}
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