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connect.go
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// Copyright (c) 2021 Blacknon. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
package sshlib
import (
"context"
"io"
"log"
"net"
"os"
"os/signal"
"sync"
"syscall"
"time"
"golang.org/x/crypto/ssh"
"golang.org/x/net/proxy"
terminal "golang.org/x/term"
)
// Connect structure to store contents about ssh connection.
type Connect struct {
// Client *ssh.Client
Client *ssh.Client
// Session
Session *ssh.Session
// Session Stdin, Stdout, Stderr...
Stdin io.Reader
Stdout io.Writer
Stderr io.Writer
// ProxyDialer
ProxyDialer proxy.ContextDialer
// Connect timeout second.
ConnectTimeout int
// SendKeepAliveMax and SendKeepAliveInterval
SendKeepAliveMax int
SendKeepAliveInterval int
// Session use tty flag.
// Set it before CraeteClient.
TTY bool
// Forward ssh agent flag.
// Set it before CraeteClient.
ForwardAgent bool
// Set the TTY to be used as the input and output for the Session/Cmd.
PtyRelayTty *os.File
// StdoutMutex is a mutex for use Stdout.
StdoutMutex *sync.Mutex
// CheckKnownHosts if true, check knownhosts.
// Ignored if HostKeyCallback is set.
// Set it before CraeteClient.
CheckKnownHosts bool
// HostKeyCallback is ssh.HostKeyCallback.
// This item takes precedence over `CheckKnownHosts`.
// Set it before CraeteClient.
HostKeyCallback ssh.HostKeyCallback
// OverwriteKnownHosts if true, if the knownhost is different, check whether to overwrite.
OverwriteKnownHosts bool
// KnownHostsFiles is list of knownhosts files path.
KnownHostsFiles []string
// TextAskWriteKnownHosts defines a confirmation message when writing a knownhost.
// We are using Go's template engine and have the following variables available.
// - Address ... ssh server hostname
// - RemoteAddr ... ssh server address
// - Fingerprint ... ssh PublicKey fingerprint
TextAskWriteKnownHosts string
// TextAskOverwriteKnownHosts defines a confirmation message when over-writing a knownhost.
// We are using Go's template engine and have the following variables available.
// - Address ... ssh server hostname
// - RemoteAddr ... ssh server address
// - OldKeyText ... old ssh PublicKey text.
// ex: /home/user/.ssh/known_hosts:17: ecdsa-sha2-nistp256 AAAAE2VjZHN...bJklasnFtkFSDyOjTFSv2g=
// - NewFingerprint ... new ssh PublicKey fingerprint
TextAskOverwriteKnownHosts string
// ssh-agent interface.
// agent.Agent or agent.ExtendedAgent
// Set it before CraeteClient.
Agent AgentInterface
// Forward x11 flag.
// Set it before CraeteClient.
ForwardX11 bool
// Forward X11 trusted flag.
// This flag is ssh -Y option like flag.
// Set it before CraeteClient.
ForwardX11Trusted bool
// Dynamic forward related logger
DynamicForwardLogger *log.Logger
// shell terminal log flag
logging bool
// terminal log add timestamp flag
logTimestamp bool
// terminal log path
logFile string
// remove ansi code on terminal log.
logRemoveAnsiCode bool
}
// CreateClient set c.Client.
func (c *Connect) CreateClient(host, port, user string, authMethods []ssh.AuthMethod) (err error) {
uri := net.JoinHostPort(host, port)
timeout := 20
if c.ConnectTimeout == 0 {
c.ConnectTimeout = timeout
}
// Create new ssh.ClientConfig{}
config := &ssh.ClientConfig{
User: user,
Auth: authMethods,
Timeout: time.Duration(c.ConnectTimeout) * time.Second,
}
if c.HostKeyCallback != nil {
config.HostKeyCallback = c.HostKeyCallback
} else {
if c.CheckKnownHosts {
if len(c.KnownHostsFiles) == 0 {
// append default files
c.KnownHostsFiles = append(c.KnownHostsFiles, "~/.ssh/known_hosts")
}
config.HostKeyCallback = c.VerifyAndAppendNew
} else {
config.HostKeyCallback = ssh.InsecureIgnoreHostKey()
}
}
// check Dialer
if c.ProxyDialer == nil {
c.ProxyDialer = proxy.Direct
}
ctx, cancel := context.WithTimeout(context.Background(), time.Duration(c.ConnectTimeout)*time.Second)
defer cancel()
// Dial to host:port
netConn, cerr := c.ProxyDialer.DialContext(ctx, "tcp", uri)
if cerr != nil {
return cerr
}
// Set deadline
netConn.SetDeadline(time.Now().Add(time.Duration(c.ConnectTimeout) * time.Second))
// Create new ssh connect
sshCon, channel, req, cerr := ssh.NewClientConn(netConn, uri, config)
if cerr != nil {
return cerr
}
// Reet deadline
netConn.SetDeadline(time.Time{})
// Create *ssh.Client
c.Client = ssh.NewClient(sshCon, channel, req)
return
}
// CreateSession retrun ssh.Session
func (c *Connect) CreateSession() (session *ssh.Session, err error) {
// Create session
session, err = c.Client.NewSession()
return
}
// SendKeepAlive send packet to session.
// TODO(blacknon): Interval及びMaxを設定できるようにする(v0.1.1)
func (c *Connect) SendKeepAlive(session *ssh.Session) {
// keep alive interval (default 30 sec)
interval := 1
if c.SendKeepAliveInterval > 0 {
interval = c.SendKeepAliveInterval
}
max := 3
if c.SendKeepAliveMax > 0 {
max = c.SendKeepAliveMax
}
t := time.NewTicker(time.Duration(c.ConnectTimeout) * time.Second)
defer t.Stop()
count := 0
for {
select {
case <-t.C:
if _, err := session.SendRequest("keepalive@openssh.com", true, nil); err != nil {
log.Println("Failed to send keepalive packet:", err)
count += 1
} else {
// err is nil.
time.Sleep(time.Duration(interval) * time.Second)
}
}
if count > max {
return
}
}
}
// CheckClientAlive check alive ssh.Client.
func (c *Connect) CheckClientAlive() error {
_, _, err := c.Client.SendRequest("keepalive", true, nil)
if err == nil {
return nil
}
return err
}
// RequestTty requests the association of a pty with the session on the remote
// host. Terminal size is obtained from the currently connected terminal
func RequestTty(session *ssh.Session) (err error) {
modes := ssh.TerminalModes{
ssh.ECHO: 1,
ssh.TTY_OP_ISPEED: 14400,
ssh.TTY_OP_OSPEED: 14400,
}
// Get terminal window size
fd := int(os.Stdout.Fd())
width, hight, err := terminal.GetSize(fd)
if err != nil {
return
}
// Get env `TERM`
term := os.Getenv("TERM")
if len(term) == 0 {
term = "xterm"
}
if err = session.RequestPty(term, hight, width, modes); err != nil {
session.Close()
return
}
// Terminal resize goroutine.
winch := syscall.Signal(0x1c)
signalchan := make(chan os.Signal, 1)
signal.Notify(signalchan, winch)
go func() {
for {
s := <-signalchan
switch s {
case winch:
fd := int(os.Stdout.Fd())
width, hight, _ = terminal.GetSize(fd)
session.WindowChange(hight, width)
}
}
}()
return
}