first draft of atheme migration code

vendor/github.com/GehirnInc/crypt/crypt.go

@@ -0,0 +1,121 @@
+// (C) 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/GehirnInc/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 = 1 + iota // import github.com/GehirnInc/crypt/apr1_crypt
+	MD5                     // import github.com/GehirnInc/crypt/md5_crypt
+	SHA256                  // import github.com/GehirnInc/crypt/sha256_crypt
+	SHA512                  // import github.com/GehirnInc/crypt/sha512_crypt
+	maxCrypt
+)
+
+var crypts = make([]func() Crypter, maxCrypt)
+
+// New returns new Crypter making the Crypt c.
+// New panics if the Crypt c is unavailable.
+func (c Crypt) New() Crypter {
+	if c > 0 && c < maxCrypt {
+		f := crypts[c]
+		if f != nil {
+			return f()
+		}
+	}
+	panic("crypt: requested crypt function is unavailable")
+}
+
+// Available reports whether the Crypt c is available.
+func (c Crypt) Available() bool {
+	return c > 0 && c < maxCrypt && crypts[c] != nil
+}
+
+var cryptPrefixes = make([]string, 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 {
+	return c.New()
+}
+
+// IsHashSupported returns true if hashedKey has a supported prefix.
+// NewFromHash will not panic for this hashedKey
+func IsHashSupported(hashedKey string) bool {
+	for i := range cryptPrefixes {
+		prefix := cryptPrefixes[i]
+		if crypts[i] != nil && strings.HasPrefix(hashedKey, prefix) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// NewFromHash returns a new Crypter using the prefix in the given hashed key.
+func NewFromHash(hashedKey string) Crypter {
+	for i := range cryptPrefixes {
+		prefix := cryptPrefixes[i]
+		if crypts[i] != nil && strings.HasPrefix(hashedKey, prefix) {
+			crypt := Crypt(uint(i))
+			return crypt.New()
+		}
+	}
+
+	panic("crypt: unknown crypt function")
+}