How to connect remote ssh server with socks proxy? - go

Question

package main
import (
"errors"
"fmt"
"net"
"golang.org/x/crypto/ssh"
)
var (
socks string = "127.0.0.1:8000"
server string = "192.168.1.1:2222"
cmd string = ""
login string = "root"
password string = ""
)
func main() {
c, err := netConn(socks)
if err != nil {
fmt.Println(err)
}
conf := &ssh.ClientConfig{
User: login,
Auth: []ssh.AuthMethod{
ssh.Password(password),
},
}
client, err := Dialer(conf, c, server)
if err != nil {
fmt.Println(err)
}
session, err := client.NewSession()
defer session.Close()
if err != nil {
fmt.Println(err)
}
session.Run(cmd)
}
func netConn(addr string) (net.Conn, error) {
conn, err := net.Dial("tcp", addr)
if err != nil {
return nil, errors.New(fmt.Sprintf("Unable to connect to %v", err))
}
return conn, nil
}
func Dialer(conf *ssh.ClientConfig, c net.Conn, host string) (*ssh.Client, error) {
conn, chans, reqs, err := ssh.NewClientConn(c, host, conf)
if err != nil {
return nil, err
}
return ssh.NewClient(conn, chans, reqs), nil
}
Client panic
ssh: handshake failed: EOF
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x80f3e2d]
goroutine 1 [running]:
panic(0x8201b60, 0x18522030)
/usr/lib/go/src/runtime/panic.go:464 +0x326
golang.org/x/crypto/ssh.(*Client).NewSession(0x0, 0x1, 0x0, 0x0)
/home/user/go/src/golang.org/x/crypto/ssh/client.go:129 +0xcd
main.main()
/home/user/go/src/ss/i.go:34 +0x276
And socks server in log
[ERR] socks: Unsupported SOCKS version: [83]
How i can make it posible? Thanks.

Answer 1

You can use the x/net/proxy package as follows:
package main
import (
"log"
"golang.org/x/crypto/ssh"
"golang.org/x/net/proxy"
)
func main() {
sshConfig := &ssh.ClientConfig{
User: "user",
// Auth: .... fill out with keys etc as normal
}
client, err := proxiedSSHClient("127.0.0.1:8000", "127.0.0.1:22", sshConfig)
if err != nil {
log.Fatal(err)
}
// get a session etc...
}
func proxiedSSHClient(proxyAddress, sshServerAddress string, sshConfig *ssh.ClientConfig) (*ssh.Client, error) {
dialer, err := proxy.SOCKS5("tcp", proxyAddress, nil, proxy.Direct)
if err != nil {
return nil, err
}
conn, err := dialer.Dial("tcp", sshServerAddress)
if err != nil {
return nil, err
}
c, chans, reqs, err := ssh.NewClientConn(conn, sshServerAddress, sshConfig)
if err != nil {
return nil, err
}
return ssh.NewClient(c, chans, reqs), nil
}

Answer 2

As you can see from the ssh package API, the function
func Dial(network, addr string, config *ClientConfig) (*Client, error)
directly returns an object of type ssh.Client.
Therefore you can shorten a lot your code with:
func main() {
conf := &ssh.ClientConfig{
User: login,
Auth: []ssh.AuthMethod{
ssh.Password(password),
},
}
client, err := ssh.Dial("tcp", server, conf)
if err != nil {
fmt.Println(err)
}
defer client.Close()
session, err := client.NewSession()
defer session.Close()
if err != nil {
fmt.Println(err)
}
session.Run(cmd)
}
Hope this helps !