/
server.go
163 lines (135 loc) · 3.23 KB
/
server.go
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package ssh
import (
"fmt"
"net"
"time"
"golang.org/x/crypto/ssh"
tomb "gopkg.in/tomb.v2"
)
const (
SignInIdLength = 4
SignInSecretLength = 16
SessionIdLength = 8
SessionSecretLength = 40
CsrfTokenLength = 40
)
func NewSSHServer(cfg *Config) (server SSHServer, err error) {
// Create ssh config for server
sshConfig, e := cfg.SSHConfig()
if e != nil {
err = e
return
}
cfg.sshConfig = sshConfig
// Validate the ssh bind addr
if cfg.Bind == "" {
err = fmt.Errorf("ssh server: Empty SSH bind address")
return
}
// Open SSH socket
sshAddr, e := net.ResolveTCPAddr("tcp", cfg.Bind)
if e != nil {
err = fmt.Errorf("ssh server: Invalid tcp address")
return
}
// Create listener
listener, e := net.ListenTCP("tcp", sshAddr)
if e != nil {
err = e
return
}
server.listener = listener
return
}
type SSHServer struct {
config *Config
listener *net.TCPListener
t tomb.Tomb
}
func (s *SSHServer) Start() {
s.config.Logger.Info("Starting SSH server", "addr", s.config.Bind)
s.t.Go(s.listen)
}
func (s *SSHServer) Stop() error {
s.t.Kill(nil)
s.config.Logger.Info("Shutting down SSH server...")
return s.t.Wait()
}
func (s *SSHServer) listen() error {
defer s.listener.Close()
// Create tomb for connection goroutines
var t tomb.Tomb
for {
// Accepts will only block for 1s
s.listener.SetDeadline(time.Now().Add(s.config.Deadline))
select {
// Stop server on channel receive
case <-s.t.Dying():
t.Kill(nil)
t.Wait()
return nil
default:
// Accept new connection
tcpConn, err := s.listener.Accept()
if err != nil {
if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
s.config.Logger.Trace("Connection timeout...")
} else {
s.config.Logger.Warn("Connection failed", "error", err)
}
continue
}
// Handle connection
s.config.Logger.Debug("Successful TCP connection: %s", tcpConn.RemoteAddr())
t.Go(func() error {
return s.handleTCPConnection(t, tcpConn)
})
}
}
return nil
}
func (s *SSHServer) handleTCPConnection(parentTomb tomb.Tomb, conn net.Conn) error {
// Convert to SSH connection
sshConn, channels, requests, err := ssh.NewServerConn(conn, s.config.sshConfig)
if err != nil {
s.config.Logger.Warn("SSH handshake failed: %s", conn.RemoteAddr())
return err
}
// Close connection on exit
s.config.Logger.Debug("Handshake successful")
defer sshConn.Conn.Close()
// Discard requests
go ssh.DiscardRequests(requests)
// Create new tomb stone
var t tomb.Tomb
for {
select {
case ch := <-channels:
chType := ch.ChannelType()
// Determine if channel is acceptable (has a registered handler)
handler, ok := s.config.Handler(chType)
if !ok {
s.config.Logger.Info("UnknownChannelType", "type", chType)
ch.Reject(ssh.UnknownChannelType, chType)
break
}
// Accept channel
channel, requests, err := ch.Accept()
if err != nil {
s.config.Logger.Warn("Error creating channel")
continue
}
t.Go(func() error {
return handler.Handle(t, sshConn, channel, requests)
})
case <-parentTomb.Dying():
t.Kill(nil)
if err := t.Wait(); err != nil {
s.config.Logger.Warn("ssh handler error: %s", err)
}
sshConn.Close()
return sshConn.Wait()
}
}
return nil
}