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// Package ssh implements the SSH transport protocol.
package ssh
import (
"fmt"
"reflect"
"gopkg.in/src-d/go-git.v4/plumbing/transport"
"gopkg.in/src-d/go-git.v4/plumbing/transport/internal/common"
"golang.org/x/crypto/ssh"
)
// DefaultClient is the default SSH client.
var DefaultClient = NewClient(nil)
// NewClient creates a new SSH client with an optional *ssh.ClientConfig.
func NewClient(config *ssh.ClientConfig) transport.Transport {
return common.NewClient(&runner{config: config})
}
// DefaultAuthBuilder is the function used to create a default AuthMethod, when
// the user doesn't provide any.
var DefaultAuthBuilder = func(user string) (AuthMethod, error) {
return NewSSHAgentAuth(user)
}
const DefaultPort = 22
type runner struct {
config *ssh.ClientConfig
}
func (r *runner) Command(cmd string, ep transport.Endpoint, auth transport.AuthMethod) (common.Command, error) {
c := &command{command: cmd, endpoint: ep, config: r.config}
if auth != nil {
c.setAuth(auth)
}
if err := c.connect(); err != nil {
return nil, err
}
return c, nil
}
type command struct {
*ssh.Session
connected bool
command string
endpoint transport.Endpoint
client *ssh.Client
auth AuthMethod
config *ssh.ClientConfig
}
func (c *command) setAuth(auth transport.AuthMethod) error {
a, ok := auth.(AuthMethod)
if !ok {
return transport.ErrInvalidAuthMethod
}
c.auth = a
return nil
}
func (c *command) Start() error {
return c.Session.Start(endpointToCommand(c.command, c.endpoint))
}
// Close closes the SSH session and connection.
func (c *command) Close() error {
if !c.connected {
return nil
}
c.connected = false
//XXX: If did read the full packfile, then the session might be already
// closed.
_ = c.Session.Close()
return c.client.Close()
}
// connect connects to the SSH server, unless a AuthMethod was set with
// SetAuth method, by default uses an auth method based on PublicKeysCallback,
// it connects to a SSH agent, using the address stored in the SSH_AUTH_SOCK
// environment var.
func (c *command) connect() error {
if c.connected {
return transport.ErrAlreadyConnected
}
if c.auth == nil {
if err := c.setAuthFromEndpoint(); err != nil {
return err
}
}
var err error
config := c.auth.clientConfig()
config.HostKeyCallback, err = c.auth.hostKeyCallback()
if err != nil {
return err
}
overrideConfig(c.config, config)
c.client, err = ssh.Dial("tcp", c.getHostWithPort(), config)
if err != nil {
return err
}
c.Session, err = c.client.NewSession()
if err != nil {
_ = c.client.Close()
return err
}
c.connected = true
return nil
}
func (c *command) getHostWithPort() string {
host := c.endpoint.Host()
port := c.endpoint.Port()
if port <= 0 {
port = DefaultPort
}
return fmt.Sprintf("%s:%d", host, port)
}
func (c *command) setAuthFromEndpoint() error {
var err error
c.auth, err = DefaultAuthBuilder(c.endpoint.User())
return err
}
func endpointToCommand(cmd string, ep transport.Endpoint) string {
return fmt.Sprintf("%s '%s'", cmd, ep.Path())
}
func overrideConfig(overrides *ssh.ClientConfig, c *ssh.ClientConfig) {
if overrides == nil {
return
}
vo := reflect.ValueOf(*overrides)
vc := reflect.ValueOf(*c)
for i := 0; i < vc.Type().NumField(); i++ {
vcf := vc.Field(i)
vof := vo.Field(i)
if isZeroValue(vcf) {
vcf.Set(vof)
}
}
*c = vc.Interface().(ssh.ClientConfig)
}
func isZeroValue(v reflect.Value) bool {
return reflect.DeepEqual(v.Interface(), reflect.Zero(v.Type()).Interface())
}
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