forked from shell909090/otpknock
/
main.go
162 lines (139 loc) · 2.97 KB
/
main.go
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
package main
import (
"bytes"
"encoding/json"
"flag"
"fmt"
"html/template"
"net"
"os"
"os/exec"
"strings"
"time"
otp "github.com/hgfischer/go-otp"
)
// CAUTION: DO NOT PROTECT SYSTEM FROM BLIND GUESS.
// attacker could use that as DOS attack.
// they can spoof their source IP address.
type Config struct {
Secret string
Emergency []string
Addr string
OpenCmd string
CloseCmd string
Interval uint16
}
var cfg *Config = nil
func LoadConfig() (cfg Config, err error) {
var configfile string
flag.StringVar(&configfile, "config", "/etc/otpknock.json", "config file")
flag.Parse()
file, err := os.Open(configfile)
if err != nil {
return
}
defer file.Close()
dec := json.NewDecoder(file)
err = dec.Decode(&cfg)
if err != nil {
return
}
if cfg.Addr == "" {
cfg.Addr = ":37798"
}
return
}
func RenderTemplate(t string, raddr *net.UDPAddr) (s string, err error) {
tmpl, err := template.New("t").Parse(t)
if err != nil {
return
}
buf := bytes.NewBufferString("")
err = tmpl.Execute(buf, raddr)
return buf.String(), nil
}
func RunCmd(s string) (err error) {
fmt.Printf("run: %s.\n", s)
cmd := exec.Command("/bin/sh", "-c", s)
return cmd.Run()
}
func OpenDoor(raddr *net.UDPAddr) {
OpenCmd, err := RenderTemplate(cfg.OpenCmd, raddr)
if err != nil {
fmt.Printf("open template Error: %s.\n", err.Error())
return
}
CloseCmd, err := RenderTemplate(cfg.CloseCmd, raddr)
if err != nil {
fmt.Printf("close template Error: %s.\n", err.Error())
return
}
fmt.Printf("open door for %s.\n", raddr.String())
err = RunCmd(OpenCmd)
if err != nil {
fmt.Printf("open exec Error: %s.\n", err.Error())
return
}
go func() {
time.Sleep(time.Duration(cfg.Interval) * time.Second)
fmt.Printf("close door for %s.\n", raddr.String())
err := RunCmd(CloseCmd)
if err != nil {
fmt.Printf("close exec Error: %s.\n", err.Error())
return
}
}()
}
func Verify(buf []byte, totp *otp.TOTP) bool {
token := string(buf)
token = strings.Trim(token, "\r\n")
fmt.Printf("begin verify: %s.\n", token)
if totp.Verify(token) {
fmt.Println("verified by totp.")
return true
}
for _, emerg := range cfg.Emergency {
if token == emerg {
fmt.Println("verified by emergency, remember to change it.")
return true
}
}
fmt.Println("verify failed.")
return false
}
func Work() {
laddr, err := net.ResolveUDPAddr("udp", cfg.Addr)
if err != nil {
fmt.Println(err.Error())
return
}
sock, err := net.ListenUDP("udp", laddr)
if err != nil {
fmt.Println(err.Error())
return
}
defer sock.Close()
totp := &otp.TOTP{Secret: cfg.Secret, IsBase32Secret: true}
buf := make([]byte, 65536)
fmt.Println("started.")
for {
n, raddr, err := sock.ReadFromUDP(buf)
fmt.Printf("got data from %s.\n", raddr.String())
if err != nil {
fmt.Println(err.Error())
continue
}
if Verify(buf[:n], totp) {
OpenDoor(raddr)
}
}
}
func main() {
config, err := LoadConfig()
if err != nil {
fmt.Println(err.Error())
return
}
cfg = &config
Work()
}