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ssh.go
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ssh.go
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package ssh
import (
"bufio"
"errors"
"net"
"os"
"time"
gossh "github.com/coreos/fleet/third_party/code.google.com/p/gosshnew/ssh"
gosshagent "github.com/coreos/fleet/third_party/code.google.com/p/gosshnew/ssh/agent"
"github.com/coreos/fleet/third_party/code.google.com/p/gosshnew/ssh/terminal"
)
type SSHForwardingClient struct {
agentForwarding bool
*gossh.Client
}
func (s *SSHForwardingClient) ForwardAgentAuthentication(session *gossh.Session) error {
if s.agentForwarding {
return gosshagent.RequestAgentForwarding(session)
}
return nil
}
func newSSHForwardingClient(client *gossh.Client, agentForwarding bool) (*SSHForwardingClient, error) {
a, err := SSHAgentClient()
if err != nil {
return nil, err
}
err = gosshagent.ForwardToAgent(client, a)
if err != nil {
return nil, err
}
return &SSHForwardingClient{agentForwarding, client}, nil
}
type Channel struct {
Stdout *bufio.Reader
Stderr *bufio.Reader
Exit chan error
}
func Execute(client *SSHForwardingClient, cmd string) (*Channel, error) {
session, err := client.NewSession()
if err != nil {
return nil, err
}
if err = client.ForwardAgentAuthentication(session); err != nil {
return nil, err
}
stdout, _ := session.StdoutPipe()
stderr, _ := session.StderrPipe()
channel := &Channel{
bufio.NewReader(stdout),
bufio.NewReader(stderr),
make(chan error),
}
session.Start(cmd)
go func() {
err := session.Wait()
channel.Exit <- err
session.Close()
}()
return channel, nil
}
func Shell(client *SSHForwardingClient) error {
session, err := client.NewSession()
if err != nil {
return err
}
defer session.Close()
if err = client.ForwardAgentAuthentication(session); err != nil {
return err
}
modes := gossh.TerminalModes{
gossh.ECHO: 1, // enable echoing
gossh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
gossh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
}
fd := int(os.Stdin.Fd())
oldState, err := terminal.MakeRaw(fd)
defer terminal.Restore(fd, oldState)
termWidth, termHeight, err := terminal.GetSize(fd)
if err != nil {
return err
}
session.Stdout = os.Stdout
session.Stderr = os.Stderr
session.Stdin = os.Stdin
if err := session.RequestPty("xterm-256color", termHeight, termWidth, modes); err != nil {
return err
}
if err = session.Shell(); err != nil {
return err
}
session.Wait()
return nil
}
func SSHAgentClient() (gosshagent.Agent, error) {
sock := os.Getenv("SSH_AUTH_SOCK")
if sock == "" {
return nil, errors.New("SSH_AUTH_SOCK environment variable is not set. Verify ssh-agent is running. See https://github.com/coreos/fleet/blob/master/Documentation/remote-access.md for help.")
}
agent, err := net.Dial("unix", sock)
if err != nil {
return nil, err
}
return gosshagent.NewClient(agent), nil
}
func sshClientConfig(user string, checker *HostKeyChecker) (*gossh.ClientConfig, error) {
agentClient, err := SSHAgentClient()
if err != nil {
return nil, err
}
signers, err := agentClient.Signers()
if err != nil {
return nil, err
}
cfg := gossh.ClientConfig{
User: user,
Auth: []gossh.AuthMethod{
gossh.PublicKeys(signers...),
},
}
if checker != nil {
cfg.HostKeyCallback = checker.Check
}
return &cfg, nil
}
func NewSSHClient(user, addr string, checker *HostKeyChecker, agentForwarding bool) (*SSHForwardingClient, error) {
clientConfig, err := sshClientConfig(user, checker)
if err != nil {
return nil, err
}
var client *gossh.Client
dialFunc := func(echan chan error) {
var err error
client, err = gossh.Dial("tcp", addr, clientConfig)
echan <- err
}
err = timeoutSSHDial(dialFunc)
if err != nil {
return nil, err
}
return newSSHForwardingClient(client, agentForwarding)
}
func NewTunnelledSSHClient(user, tunaddr, tgtaddr string, checker *HostKeyChecker, agentForwarding bool) (*SSHForwardingClient, error) {
clientConfig, err := sshClientConfig(user, checker)
if err != nil {
return nil, err
}
var tunnelClient *gossh.Client
dialFunc := func(echan chan error) {
var err error
tunnelClient, err = gossh.Dial("tcp", tunaddr, clientConfig)
echan <- err
}
err = timeoutSSHDial(dialFunc)
if err != nil {
return nil, err
}
var targetConn net.Conn
dialFunc = func(echan chan error) {
tgtTCPAddr, err := net.ResolveTCPAddr("tcp", tgtaddr)
if err != nil {
echan <- err
return
}
targetConn, err = tunnelClient.DialTCP("tcp", nil, tgtTCPAddr)
echan <- err
}
err = timeoutSSHDial(dialFunc)
if err != nil {
return nil, err
}
c, chans, reqs, err := gossh.NewClientConn(targetConn, tgtaddr, clientConfig)
if err != nil {
return nil, err
}
return newSSHForwardingClient(gossh.NewClient(c, chans, reqs), agentForwarding)
}
func timeoutSSHDial(dial func(chan error)) error {
var err error
echan := make(chan error)
go dial(echan)
select {
case <-time.After(time.Duration(time.Second * 10)):
return errors.New("Timed out while initiating SSH connection")
case err = <-echan:
return err
}
}