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// Package ssh implements a ssh client for go-git.
package ssh
import (
"bufio"
"bytes"
"fmt"
"io"
"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp"
"gopkg.in/src-d/go-git.v4/plumbing/transport"
"gopkg.in/src-d/go-git.v4/utils/ioutil"
"golang.org/x/crypto/ssh"
)
type fetchPackSession struct {
*session
cmdRun bool
advRefsRun bool
done chan error
}
func newFetchPackSession(ep transport.Endpoint) (*fetchPackSession, error) {
s := &fetchPackSession{
session: &session{
endpoint: ep,
},
}
if err := s.connect(); err != nil {
return nil, err
}
return s, nil
}
func (s *fetchPackSession) AdvertisedReferences() (*transport.UploadPackInfo, error) {
if s.advRefsRun {
return nil, transport.ErrAdvertistedReferencesAlreadyCalled
}
defer func() { s.advRefsRun = true }()
if err := s.ensureRunCommand(); err != nil {
return nil, err
}
i := transport.NewUploadPackInfo()
if err := i.Decode(s.stdout); err != nil {
if err != packp.ErrEmpty {
return nil, err
}
_ = s.stdin.Close()
scan := bufio.NewScanner(s.stderr)
if !scan.Scan() {
return nil, transport.ErrEmptyRemoteRepository
}
if isRepoNotFoundError(string(scan.Bytes())) {
return nil, transport.ErrRepositoryNotFound
}
return nil, err
}
return i, nil
}
// FetchPack returns a packfile for a given upload request.
// Closing the returned reader will close the SSH session.
func (s *fetchPackSession) FetchPack(req *transport.UploadPackRequest) (
io.ReadCloser, error) {
if req.IsEmpty() {
return nil, transport.ErrEmptyUploadPackRequest
}
if !s.advRefsRun {
if _, err := s.AdvertisedReferences(); err != nil {
return nil, err
}
}
if err := fetchPack(s.stdin, s.stdout, req); err != nil {
return nil, err
}
fs := &fetchSession{
Reader: s.stdout,
session: s.session.session,
done: s.done,
}
r, err := ioutil.NonEmptyReader(fs)
if err == ioutil.ErrEmptyReader {
_ = fs.Close()
return nil, transport.ErrEmptyUploadPackRequest
}
return ioutil.NewReadCloser(r, fs), nil
}
func (s *fetchPackSession) ensureRunCommand() error {
if s.cmdRun {
return nil
}
s.cmdRun = true
s.done = s.runCommand(s.getCommand())
return nil
}
type fetchSession struct {
io.Reader
session *ssh.Session
done <-chan error
}
// Close closes the session and collects the output state of the remote
// SSH command.
//
// If both the remote command and the closing of the session completes
// susccessfully it returns nil.
//
// If the remote command completes unsuccessfully or is interrupted by a
// signal, it returns the corresponding *ExitError.
//
// Otherwise, if clossing the SSH session fails it returns the close
// error. Closing the session when the other has already close it is
// not cosidered an error.
func (f *fetchSession) Close() (err error) {
if err := <-f.done; err != nil {
return err
}
if err := f.session.Close(); err != nil && err != io.EOF {
return err
}
return nil
}
func (s *fetchPackSession) getCommand() string {
directory := s.endpoint.Path
directory = directory[1:]
return fmt.Sprintf("git-upload-pack '%s'", directory)
}
var (
nak = []byte("NAK")
eol = []byte("\n")
)
// FetchPack implements the git-fetch-pack protocol.
//
// TODO support multi_ack mode
// TODO support multi_ack_detailed mode
// TODO support acks for common objects
// TODO build a proper state machine for all these processing options
func fetchPack(w io.WriteCloser, r io.Reader,
req *transport.UploadPackRequest) error {
if err := sendUlReq(w, req); err != nil {
return fmt.Errorf("sending upload-req message: %s", err)
}
if err := sendHaves(w, req); err != nil {
return fmt.Errorf("sending haves message: %s", err)
}
if err := sendDone(w); err != nil {
return fmt.Errorf("sending done message: %s", err)
}
if err := w.Close(); err != nil {
return fmt.Errorf("closing input: %s", err)
}
if err := readNAK(r); err != nil {
return fmt.Errorf("reading NAK: %s", err)
}
return nil
}
func sendUlReq(w io.Writer, req *transport.UploadPackRequest) error {
ur := packp.NewUlReq()
ur.Wants = req.Wants
ur.Depth = packp.DepthCommits(req.Depth)
e := packp.NewUlReqEncoder(w)
return e.Encode(ur)
}
func sendHaves(w io.Writer, req *transport.UploadPackRequest) error {
e := pktline.NewEncoder(w)
for _, have := range req.Haves {
if err := e.Encodef("have %s\n", have); err != nil {
return fmt.Errorf("sending haves for %q: %s", have, err)
}
}
if len(req.Haves) != 0 {
if err := e.Flush(); err != nil {
return fmt.Errorf("sending flush-pkt after haves: %s", err)
}
}
return nil
}
func sendDone(w io.Writer) error {
e := pktline.NewEncoder(w)
return e.Encodef("done\n")
}
func readNAK(r io.Reader) error {
s := pktline.NewScanner(r)
if !s.Scan() {
return s.Err()
}
b := s.Bytes()
b = bytes.TrimSuffix(b, eol)
if !bytes.Equal(b, nak) {
return fmt.Errorf("expecting NAK, found %q instead", string(b))
}
return nil
}
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