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
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
// Copyright © 2022 siddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package challenge
import (
"bufio"
"fmt"
"net"
"os"
"ricketyspace.net/cryptopals/lib"
)
// Usage:
//
func C36(args []string) {
if len(args) < 2 {
fmt.Println("Usage: cryptopals -c 36 [ client | server ] PORT")
return
}
entity := args[0]
port, err := lib.StrToNum(args[1])
if err != nil {
fmt.Println("port invalid")
return
}
if port < 12000 {
fmt.Println("port number must be >= 12000")
return
}
// Register user on the server.
serverRegisterUser := func(server *lib.SRPServer, info []string) error {
if len(info) != 5 {
return fmt.Errorf("regiser user: info valid")
}
n := info[0]
g := info[1]
k := info[2]
ident := info[3]
pass := info[4]
user, err := lib.NewSRPUser(n, g, k, ident, pass)
if err != nil {
return fmt.Errorf("register user: %v", err)
}
if err = server.RegisterUser(user); err != nil {
return fmt.Errorf("register user: %v", err)
}
return nil
}
// Handle connection from a client.
serverHandleConn := func(server *lib.SRPServer, conn net.Conn) {
defer conn.Close()
fmt.Printf("Got connection from %v\n", conn.RemoteAddr())
// Read packet from client.
packet, err := bufio.NewReader(conn).ReadString('\n')
if err != nil {
fmt.Printf("Unable to read from client %v\n",
conn.RemoteAddr())
return
}
// Remove newline character from packet.
packet = packet[:len(packet)-1]
parts := lib.StrSplitAt('+', packet)
if len(parts) < 2 {
fmt.Fprintf(conn, "invalid request\n")
return
}
switch {
case parts[0] == "register":
err = serverRegisterUser(server, parts[1:])
if err != nil {
fmt.Fprintf(conn, "%v\n", err)
return
} else {
fmt.Fprintf(conn, "OK\n")
}
return
default:
fmt.Fprintf(conn, "invalid action")
return
}
}
// Start SRP server.
serverSpawn := func() {
server := new(lib.SRPServer)
p := fmt.Sprintf(":%d", port)
ln, err := net.Listen("tcp", p)
if err != nil {
fmt.Printf("server listen error: %v\n", err)
return
}
for {
fmt.Println("Waiting for connection...")
conn, err := ln.Accept()
if err != nil {
fmt.Printf("server accept error: %v\n", err)
}
go serverHandleConn(server, conn)
}
}
// Register user with server.
clientRegisterUser := func(client *lib.SRPClient, ident string) error {
n := lib.StripSpaceChars(
`ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024
e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd
3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec
6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f
24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361
c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552
bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff
fffffffffffff`)
g := "2"
k := "3"
// Prompt for password.
fmt.Printf("password> ")
pass, err := bufio.NewReader(os.Stdin).ReadString('\n')
if err != nil {
return fmt.Errorf("unable to read password: %v", err)
}
// Create session for user.
client.Session, err = lib.NewSRPClientSession(n, g, k, ident)
if err != nil {
return fmt.Errorf("unable to create session: %v", err)
}
// Make SRP registration packet.
packet := fmt.Sprintf("%s+%s+%s+%s+%s+%s", "register",
n, g, k, ident, pass)
// Try to connect to server.
conn, err := net.Dial("tcp", fmt.Sprintf(":%d", port))
if err != nil {
return fmt.Errorf("unable connect to server: %v", err)
}
defer conn.Close()
// Send packet to server.
_, err = fmt.Fprintf(conn, "%s", packet)
if err != nil {
return fmt.Errorf("unable communicate with server: %v", err)
}
// Wait and try to get registration ACK from server.
spacket, err := bufio.NewReader(conn).ReadString('\n')
if err != nil {
return fmt.Errorf("server did not respond: %v", err)
}
// Remove newline character.
spacket = spacket[:len(spacket)-1]
if spacket != "OK" {
return fmt.Errorf("server registration failed: %s", spacket)
}
return nil
}
// Start SRP client.
clientSpawn := func() {
client := new(lib.SRPClient)
// Enter repl.
for {
// Read message from stdin.
fmt.Printf("> ")
msg, err := bufio.NewReader(os.Stdin).ReadString('\n')
if err != nil {
fmt.Printf("read error: %v\n", err)
return
}
// Remove newline character.
msg = msg[:len(msg)-1]
msg_parts := lib.StrSplitAt(' ', msg)
switch {
case msg_parts[0] == "register" && len(msg_parts) == 2:
err := clientRegisterUser(client, msg_parts[1])
if err != nil {
fmt.Printf("Registration failed: %v\n", err)
} else {
fmt.Printf("Registered!\n")
}
}
}
}
// Take action based on entity.
switch {
case entity == "server":
serverSpawn()
case entity == "client":
clientSpawn()
default:
fmt.Println("uknown entity")
}
}
|
