SSH Server
To create an SSH server program in Go, you need to create a few files: main.go for the main logic and optionally, a server.go file for the server functionality. Here is a step-by-step guide:
Step 1: Initialize the Go Module
First, create a new directory for your project and initialize the Go module.
mkdir sshserver
cd sshserver
go mod init github.com/username/sshserver
Step 2: Create the server.go File
Create a server.go file to handle the SSH server functionality.
// server.go
package main
import (
"io"
"log"
"net"
"os"
"golang.org/x/crypto/ssh"
)
// handleConnection handles incoming SSH connections.
func handleConnection(conn net.Conn, config *ssh.ServerConfig) {
sshConn, chans, reqs, err := ssh.NewServerConn(conn, config)
if err != nil {
log.Printf("Failed to handshake: %v", err)
return
}
defer sshConn.Close()
go ssh.DiscardRequests(reqs)
for newChannel := range chans {
if newChannel.ChannelType() != "session" {
newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
continue
}
channel, requests, err := newChannel.Accept()
if err != nil {
log.Printf("Could not accept channel: %v", err)
return
}
go func(in <-chan *ssh.Request) {
for req := range in {
switch req.Type {
case "shell":
if len(req.Payload) == 0 {
req.Reply(true, nil)
}
}
}
}(requests)
go func() {
io.Copy(channel, channel)
channel.Close()
}()
}
}
// StartServer starts the SSH server on the specified port.
func StartServer(port string, config *ssh.ServerConfig) error {
listener, err := net.Listen("tcp", ":"+port)
if err != nil {
return err
}
defer listener.Close()
log.Printf("SSH server started on port %s", port)
for {
conn, err := listener.Accept()
if err != nil {
return err
}
go handleConnection(conn, config)
}
}
Step 3: Create the main.go File
Create a main.go file to use the server functionality.
// main.go
package main
import (
"fmt"
"io/ioutil"
"log"
"os"
"golang.org/x/crypto/ssh"
)
func main() {
if len(os.Args) != 3 {
fmt.Println("Usage: sshserver <port> <private_key_file>")
os.Exit(1)
}
port := os.Args[1]
privateKeyFile := os.Args[2]
privateBytes, err := ioutil.ReadFile(privateKeyFile)
if err != nil {
log.Fatalf("Failed to load private key: %v", err)
}
private, err := ssh.ParsePrivateKey(privateBytes)
if err != nil {
log.Fatalf("Failed to parse private key: %v", err)
}
config := &ssh.ServerConfig{
NoClientAuth: true,
}
config.AddHostKey(private)
fmt.Printf("Starting SSH server on port %s...\n", port)
if err := StartServer(port, config); err != nil {
log.Fatalf("Server failed: %v", err)
}
}
Step 4: Run the Program
Run the program using the go run command.
go run main.go 2222 path/to/private_key
This will start the SSH server on port 2222. You can connect to it using an SSH client.
Last modified: 19 December 2024