/
main.go
190 lines (164 loc) · 4.31 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
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
package main
import (
"context"
"errors"
"fmt"
"io"
"log"
"net"
"os"
"os/signal"
"os/user"
"path/filepath"
"strings"
"syscall"
flag "github.com/spf13/pflag"
"golang.org/x/crypto/ssh"
)
func parseSSHArg(arg string) (user string, host string, port string, err error) {
parts := strings.SplitN(arg, "@", 2)
if len(parts) != 2 {
err = errors.New("invalid ssh arg")
return
}
user = parts[0]
if user == "" {
err = errors.New("empty username")
return
}
addr := parts[1]
host, port, err = net.SplitHostPort(addr)
if err != nil {
if strings.Contains(err.Error(), "missing port in address") {
host = addr
err = nil
}
}
return
}
func createSSHConfig(user, keyFilePath string) (*ssh.ClientConfig, error) {
key, err := os.ReadFile(keyFilePath)
if err != nil {
return nil, err
}
// create signer for this private key
signer, err := ssh.ParsePrivateKey(key)
if err != nil {
return nil, err
}
return &ssh.ClientConfig{
User: user,
Auth: []ssh.AuthMethod{
ssh.PublicKeys(signer),
},
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}, nil
}
func main() {
// get home dir
currUser, err := user.Current()
if err != nil {
log.Fatal("Error on get current user: ", err)
}
homeDir := currUser.HomeDir
// args + defaults where necessary
sshArg := ""
var localPort uint16 = 0
var remotePort uint16
var keyFilePath string = filepath.Join(homeDir, ".ssh", "id_ed25519")
// get cli args
flag.StringVarP(&sshArg, "ssh", "s", "", "the ssh endpoint (user and address) with the format user@host:port. Defaults is 22")
flag.StringVarP(&keyFilePath, "identity_file", "i", keyFilePath, "key file")
flag.Uint16VarP(&localPort, "local_port", "l", localPort, "local port. Defaults to 0 ie random port is picked")
flag.Uint16VarP(&remotePort, "remote_port", "r", 0, "remote port")
flag.Parse()
// check args
user, host, port, err := parseSSHArg(sshArg)
if err != nil {
log.Fatal("Error on parse SSH arg: ", err)
}
if port == "" {
port = "22"
}
if remotePort == 0 {
log.Fatal("Error. Remote port arg missing.")
}
// [localhost:<localPort>] <-> [<user>@<host>:<port>'] <-> [:<remotePort>]
// get ssh config
config, err := createSSHConfig(user, keyFilePath)
if err != nil {
log.Fatal("Error on create SSH config: ", err)
}
// create ssh sshClient
sshAddr := host + ":" + port
sshClient, err := ssh.Dial("tcp", sshAddr, config)
if err != nil {
log.Fatal("Error on dial to SSH endpoint: ", err)
}
defer sshClient.Close()
log.Printf("Connected to SSH: %s@%s\n", user, sshAddr)
// create session. Each client conn can support multiple interactive
// sessions
session, err := sshClient.NewSession()
if err != nil {
log.Fatal("Error on create session: ", err)
}
defer session.Close()
log.Println("Created SSH session")
// listen on local port
localAddr := fmt.Sprintf("localhost:%d", localPort)
listener, err := net.Listen("tcp", localAddr)
if err != nil {
log.Fatalf("Error on create listener at '%d': %v", localPort, err)
}
defer listener.Close()
log.Printf("Listening for local connections at: %s\n", localAddr)
// ctx
ctx, cancel := context.WithCancel(context.Background())
// handle close signal
sigs := make(chan os.Signal, 1)
signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
go func() {
sig := <-sigs
log.Printf("received signal: %s\n", sig.String())
cancel()
listener.Close()
}()
remoteAddr := fmt.Sprintf("localhost:%d", remotePort)
id := 0
loop:
for {
localConn, err := listener.Accept()
if err != nil {
if strings.Contains(err.Error(), "use of closed network connection") {
// listener closed
break loop
}
log.Fatal("Error on accept: ", err)
}
remoteConn, err := sshClient.Dial("tcp", remoteAddr)
if err != nil {
log.Fatalf("Error on conn to remote address (%s) via tunnel: %v", remoteAddr, err)
}
id++
log.Printf("Tunnel [%d] established: local [%s] <-> remote [%s]\n",
id, localConn.RemoteAddr(), remoteAddr)
go createTunnel(ctx, id, localConn, remoteConn)
}
log.Println("Exiting")
}
func createTunnel(ctx context.Context, id int, local net.Conn, remote net.Conn) {
ctx, cancel := context.WithCancel(ctx)
go func() {
io.Copy(local, remote)
cancel()
}()
go func() {
io.Copy(remote, local)
cancel()
}()
<-ctx.Done()
remote.Close()
local.Close()
log.Printf("Tunnel [%d] closed for: %s\n", id, local.RemoteAddr())
}