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
|
package sshd
import (
"net"
"time"
"github.com/shazow/rateio"
"golang.org/x/crypto/ssh"
)
// SSHListener is the container for the connection and ssh-related configuration
type SSHListener struct {
net.Listener
config *ssh.ServerConfig
RateLimit func() rateio.Limiter
HandlerFunc func(term *Terminal)
}
// ListenSSH makes an SSH listener socket
func ListenSSH(laddr string, config *ssh.ServerConfig) (*SSHListener, error) {
socket, err := net.Listen("tcp", laddr)
if err != nil {
return nil, err
}
l := SSHListener{Listener: socket, config: config}
return &l, nil
}
func (l *SSHListener) handleConn(conn net.Conn) (*Terminal, error) {
if l.RateLimit != nil {
// TODO: Configurable Limiter?
conn = ReadLimitConn(conn, l.RateLimit())
}
// If the connection doesn't write anything back for too long before we get
// a valid session, it should be dropped.
var handleTimeout = 20 * time.Second
conn.SetReadDeadline(time.Now().Add(handleTimeout))
defer conn.SetReadDeadline(time.Time{})
// Upgrade TCP connection to SSH connection
sshConn, channels, requests, err := ssh.NewServerConn(conn, l.config)
if err != nil {
return nil, err
}
// FIXME: Disconnect if too many faulty requests? (Avoid DoS.)
go ssh.DiscardRequests(requests)
return NewSession(sshConn, channels)
}
// Serve Accepts incoming connections as terminal requests and yield them
func (l *SSHListener) Serve() {
defer l.Close()
for {
conn, err := l.Accept()
if err != nil {
logger.Printf("Failed to accept connection: %s", err)
break
}
// Goroutineify to resume accepting sockets early
go func() {
term, err := l.handleConn(conn)
if err != nil {
logger.Printf("[%s] Failed to handshake: %s", conn.RemoteAddr(), err)
conn.Close() // Must be closed to avoid a leak
return
}
l.HandlerFunc(term)
}()
}
}
|
