1package crypto
2
3import (
4	"crypto/des"
5	"crypto/hmac"
6	"crypto/sha1"
7	"errors"
8	"hash"
9
10	"github.com/jcmturner/gokrb5/v8/crypto/common"
11	"github.com/jcmturner/gokrb5/v8/crypto/rfc3961"
12	"github.com/jcmturner/gokrb5/v8/iana/chksumtype"
13	"github.com/jcmturner/gokrb5/v8/iana/etypeID"
14)
15
16//RFC: 3961 Section 6.3
17
18/*
19                 des3-cbc-hmac-sha1-kd, hmac-sha1-des3-kd
20              ------------------------------------------------
21              protocol key format     24 bytes, parity in low
22                                      bit of each
23
24              key-generation seed     21 bytes
25              length
26
27              hash function           SHA-1
28
29              HMAC output size        160 bits
30
31              message block size      8 bytes
32
33              default string-to-key   empty string
34              params
35
36              encryption and          triple-DES encrypt and
37              decryption functions    decrypt, in outer-CBC
38                                      mode (cipher block size
39                                      8 octets)
40
41              key generation functions:
42
43              random-to-key           DES3random-to-key (see
44                                      below)
45
46              string-to-key           DES3string-to-key (see
47                                      below)
48
49   The des3-cbc-hmac-sha1-kd encryption type is assigned the value
50   sixteen (16).  The hmac-sha1-des3-kd checksum algorithm is assigned a
51   checksum type number of twelve (12)*/
52
53// Des3CbcSha1Kd implements Kerberos encryption type des3-cbc-hmac-sha1-kd
54type Des3CbcSha1Kd struct {
55}
56
57// GetETypeID returns the EType ID number.
58func (e Des3CbcSha1Kd) GetETypeID() int32 {
59	return etypeID.DES3_CBC_SHA1_KD
60}
61
62// GetHashID returns the checksum type ID number.
63func (e Des3CbcSha1Kd) GetHashID() int32 {
64	return chksumtype.HMAC_SHA1_DES3_KD
65}
66
67// GetKeyByteSize returns the number of bytes for key of this etype.
68func (e Des3CbcSha1Kd) GetKeyByteSize() int {
69	return 24
70}
71
72// GetKeySeedBitLength returns the number of bits for the seed for key generation.
73func (e Des3CbcSha1Kd) GetKeySeedBitLength() int {
74	return 21 * 8
75}
76
77// GetHashFunc returns the hash function for this etype.
78func (e Des3CbcSha1Kd) GetHashFunc() func() hash.Hash {
79	return sha1.New
80}
81
82// GetMessageBlockByteSize returns the block size for the etype's messages.
83func (e Des3CbcSha1Kd) GetMessageBlockByteSize() int {
84	//For traditional CBC mode with padding, it would be the underlying cipher's block size
85	return des.BlockSize
86}
87
88// GetDefaultStringToKeyParams returns the default key derivation parameters in string form.
89func (e Des3CbcSha1Kd) GetDefaultStringToKeyParams() string {
90	var s string
91	return s
92}
93
94// GetConfounderByteSize returns the byte count for confounder to be used during cryptographic operations.
95func (e Des3CbcSha1Kd) GetConfounderByteSize() int {
96	return des.BlockSize
97}
98
99// GetHMACBitLength returns the bit count size of the integrity hash.
100func (e Des3CbcSha1Kd) GetHMACBitLength() int {
101	return e.GetHashFunc()().Size() * 8
102}
103
104// GetCypherBlockBitLength returns the bit count size of the cypher block.
105func (e Des3CbcSha1Kd) GetCypherBlockBitLength() int {
106	return des.BlockSize * 8
107}
108
109// StringToKey returns a key derived from the string provided.
110func (e Des3CbcSha1Kd) StringToKey(secret string, salt string, s2kparams string) ([]byte, error) {
111	if s2kparams != "" {
112		return []byte{}, errors.New("s2kparams must be an empty string")
113	}
114	return rfc3961.DES3StringToKey(secret, salt, e)
115}
116
117// RandomToKey returns a key from the bytes provided.
118func (e Des3CbcSha1Kd) RandomToKey(b []byte) []byte {
119	return rfc3961.DES3RandomToKey(b)
120}
121
122// DeriveRandom generates data needed for key generation.
123func (e Des3CbcSha1Kd) DeriveRandom(protocolKey, usage []byte) ([]byte, error) {
124	r, err := rfc3961.DeriveRandom(protocolKey, usage, e)
125	return r, err
126}
127
128// DeriveKey derives a key from the protocol key based on the usage value.
129func (e Des3CbcSha1Kd) DeriveKey(protocolKey, usage []byte) ([]byte, error) {
130	r, err := e.DeriveRandom(protocolKey, usage)
131	if err != nil {
132		return nil, err
133	}
134	return e.RandomToKey(r), nil
135}
136
137// EncryptData encrypts the data provided.
138func (e Des3CbcSha1Kd) EncryptData(key, data []byte) ([]byte, []byte, error) {
139	return rfc3961.DES3EncryptData(key, data, e)
140}
141
142// EncryptMessage encrypts the message provided and concatenates it with the integrity hash to create an encrypted message.
143func (e Des3CbcSha1Kd) EncryptMessage(key, message []byte, usage uint32) ([]byte, []byte, error) {
144	return rfc3961.DES3EncryptMessage(key, message, usage, e)
145}
146
147// DecryptData decrypts the data provided.
148func (e Des3CbcSha1Kd) DecryptData(key, data []byte) ([]byte, error) {
149	return rfc3961.DES3DecryptData(key, data, e)
150}
151
152// DecryptMessage decrypts the message provided and verifies the integrity of the message.
153func (e Des3CbcSha1Kd) DecryptMessage(key, ciphertext []byte, usage uint32) ([]byte, error) {
154	return rfc3961.DES3DecryptMessage(key, ciphertext, usage, e)
155}
156
157// VerifyIntegrity checks the integrity of the plaintext message.
158func (e Des3CbcSha1Kd) VerifyIntegrity(protocolKey, ct, pt []byte, usage uint32) bool {
159	return rfc3961.VerifyIntegrity(protocolKey, ct, pt, usage, e)
160}
161
162// GetChecksumHash returns a keyed checksum hash of the bytes provided.
163func (e Des3CbcSha1Kd) GetChecksumHash(protocolKey, data []byte, usage uint32) ([]byte, error) {
164	return common.GetHash(data, protocolKey, common.GetUsageKc(usage), e)
165}
166
167// VerifyChecksum compares the checksum of the message bytes is the same as the checksum provided.
168func (e Des3CbcSha1Kd) VerifyChecksum(protocolKey, data, chksum []byte, usage uint32) bool {
169	c, err := e.GetChecksumHash(protocolKey, data, usage)
170	if err != nil {
171		return false
172	}
173	return hmac.Equal(chksum, c)
174}
175