1// Copyright 2017 The Go Authors. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5package algorithm
 6
 7import (
 8	"crypto/aes"
 9	"crypto/cipher"
10	"crypto/des"
11
12	"golang.org/x/crypto/cast5"
13)
14
15// Cipher is an official symmetric key cipher algorithm. See RFC 4880,
16// section 9.2.
17type Cipher interface {
18	// Id returns the algorithm ID, as a byte, of the cipher.
19	Id() uint8
20	// KeySize returns the key size, in bytes, of the cipher.
21	KeySize() int
22	// BlockSize returns the block size, in bytes, of the cipher.
23	BlockSize() int
24	// New returns a fresh instance of the given cipher.
25	New(key []byte) cipher.Block
26}
27
28// The following constants mirror the OpenPGP standard (RFC 4880).
29const (
30	TripleDES = CipherFunction(2)
31	CAST5     = CipherFunction(3)
32	AES128    = CipherFunction(7)
33	AES192    = CipherFunction(8)
34	AES256    = CipherFunction(9)
35)
36
37// CipherById represents the different block ciphers specified for OpenPGP. See
38// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-13
39var CipherById = map[uint8]Cipher{
40	TripleDES.Id(): TripleDES,
41	CAST5.Id():     CAST5,
42	AES128.Id():    AES128,
43	AES192.Id():    AES192,
44	AES256.Id():    AES256,
45}
46
47type CipherFunction uint8
48
49// ID returns the algorithm Id, as a byte, of cipher.
50func (sk CipherFunction) Id() uint8 {
51	return uint8(sk)
52}
53
54// KeySize returns the key size, in bytes, of cipher.
55func (cipher CipherFunction) KeySize() int {
56	switch cipher {
57	case CAST5:
58		return cast5.KeySize
59	case AES128:
60		return 16
61	case AES192, TripleDES:
62		return 24
63	case AES256:
64		return 32
65	}
66	return 0
67}
68
69// BlockSize returns the block size, in bytes, of cipher.
70func (cipher CipherFunction) BlockSize() int {
71	switch cipher {
72	case TripleDES:
73		return des.BlockSize
74	case CAST5:
75		return 8
76	case AES128, AES192, AES256:
77		return 16
78	}
79	return 0
80}
81
82// New returns a fresh instance of the given cipher.
83func (cipher CipherFunction) New(key []byte) (block cipher.Block) {
84	var err error
85	switch cipher {
86	case TripleDES:
87		block, err = des.NewTripleDESCipher(key)
88	case CAST5:
89		block, err = cast5.NewCipher(key)
90	case AES128, AES192, AES256:
91		block, err = aes.NewCipher(key)
92	}
93	if err != nil {
94		panic(err.Error())
95	}
96	return
97}