1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
package scram
import (
"bufio"
"bytes"
"crypto/hmac"
"crypto/sha1"
"crypto/subtle"
"errors"
"fmt"
"strconv"
"strings"
"golang.org/x/crypto/pbkdf2"
"golang.org/x/text/transform"
"github.com/twstrike/coyim/sasl"
)
type state interface {
challenge(sasl.Token, sasl.Properties, sasl.AttributeValuePairs) (state, sasl.Token, error)
}
// RFC 5802, section 5
type firstMessage struct{}
func (c firstMessage) challenge(_ sasl.Token, props sasl.Properties, pairs sasl.AttributeValuePairs) (state, sasl.Token, error) {
user, ok := props[sasl.AuthID]
if !ok {
return c, nil, sasl.PropertyMissingError{sasl.AuthID}
}
clientNonce, ok := props[sasl.ClientNonce]
if !ok {
return c, nil, sasl.PropertyMissingError{sasl.ClientNonce}
}
bare := fmt.Sprintf("n=%s,r=%s", user, clientNonce)
t := sasl.Token("n,," + bare)
return clientFinalMessage{[]byte(bare)}, t, nil
}
type clientFinalMessage struct {
firstMessageBare []byte
}
func (c clientFinalMessage) challenge(serverMessage sasl.Token, props sasl.Properties, pairs sasl.AttributeValuePairs) (state, sasl.Token, error) {
serverNonce, ok := pairs["r"]
if !ok {
return c, nil, sasl.ErrMissingParameter
}
salt, ok := pairs["s"]
if !ok {
return c, nil, sasl.ErrMissingParameter
}
saltToken, err := sasl.DecodeToken([]byte(salt))
if err != nil {
return c, nil, err
}
count, ok := pairs["i"]
if !ok {
return c, nil, sasl.ErrMissingParameter
}
numIterations, err := strconv.Atoi(count)
if err != nil {
return c, nil, err
}
password, ok := props[sasl.Password]
if !ok {
return c, nil, sasl.PropertyMissingError{sasl.Password}
}
clientNonce, ok := props[sasl.ClientNonce]
if !ok {
return c, nil, sasl.PropertyMissingError{sasl.ClientNonce}
}
if !strings.HasPrefix(serverNonce, clientNonce) {
return c, nil, errors.New("nonce mismatch")
}
finalMessageBare := []byte("c=biws,r=" + serverNonce)
normPass, _ := c.normalizedPassword(password)
saltedPassword := pbkdf2.Key([]byte(normPass), saltToken, numIterations, sha1.Size, sha1.New)
return c.compose(saltedPassword, finalMessageBare, serverMessage)
}
func (c clientFinalMessage) compose(saltedPassword, finalMessageBare, serverFirstMessage []byte) (state, sasl.Token, error) {
clientMAC := hmac.New(sha1.New, saltedPassword)
clientMAC.Write([]byte("Client Key"))
clientKey := clientMAC.Sum(nil)
storedKey := sha1.Sum(clientKey)
serverMAC := hmac.New(sha1.New, saltedPassword)
serverMAC.Write([]byte("Server Key"))
serverKey := serverMAC.Sum(nil)
authMessage := bytes.Join([][]byte{
c.firstMessageBare,
serverFirstMessage,
finalMessageBare,
}, []byte(","))
clientSignatureMAC := hmac.New(sha1.New, storedKey[:])
clientSignatureMAC.Write(authMessage)
clientSignature := clientSignatureMAC.Sum(nil)
clientProof := make([]byte, sha1.Size)
for i := range clientProof {
clientProof[i] = clientKey[i] ^ clientSignature[i]
}
serverSignatureMAC := hmac.New(sha1.New, serverKey[:])
serverSignatureMAC.Write(authMessage)
serverSignature := serverSignatureMAC.Sum(nil)
p := []byte(",p=")
encodedProf := sasl.Token(clientProof).Encode()
finalMessage := make([]byte, len(finalMessageBare)+len(p)+len(encodedProf))
n := copy(finalMessage[:len(finalMessageBare)], finalMessageBare)
n = n + copy(finalMessage[n:n+len(p)], p)
copy(finalMessage[n:n+len(encodedProf)], encodedProf)
encodedServerSignature := sasl.Token(serverSignature).Encode()
serverAuthentication := append([]byte("v="), encodedServerSignature...)
return authenticateServer{serverAuthentication}, sasl.Token(finalMessage), nil
}
func (c clientFinalMessage) normalizedPassword(password string) (string, error) {
t := transform.NewReader(
strings.NewReader(password), sasl.Stringprep)
r := bufio.NewReader(t)
normalized, _, err := r.ReadLine()
return string(normalized), err
}
type authenticateServer struct {
serverAuthentication []byte
}
func (c authenticateServer) challenge(t sasl.Token, _ sasl.Properties, _ sasl.AttributeValuePairs) (state, sasl.Token, error) {
if subtle.ConstantTimeCompare(t, c.serverAuthentication) != 1 {
return c, nil, errors.New("server signature mismatch")
}
return finished{}, nil, nil
}
type finished struct{}
func (finished) challenge(sasl.Token, sasl.Properties, sasl.AttributeValuePairs) (state, sasl.Token, error) {
return finished{}, nil, nil
}
|
