scp.go

package scp

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	log "github.com/sirupsen/logrus"
	"golang.org/x/crypto/ssh"
)

const (
	fileMode = "0644"
	buffSize = 1024 * 256
)

//CopyTo copy from local to remote
func CopyTo(sshClient *ssh.Client, local string, remote string) (int64, error) {
	session, err := sshClient.NewSession()
	if err != nil {
		return 0, err
	}
	defer session.Close()
	stderr := &bytes.Buffer{}
	session.Stderr = stderr
	stdout := &bytes.Buffer{}
	session.Stdout = stdout
	writer, err := session.StdinPipe()
	if err != nil {
		return 0, err
	}
	defer writer.Close()
	err = session.Start("scp -t " + filepath.Dir(remote))
	if err != nil {
		return 0, err
	}

	localFile, err := os.Open(local)
	if err != nil {
		return 0, err
	}
	fileInfo, err := localFile.Stat()
	if err != nil {
		return 0, err
	}
	_, err = fmt.Fprintf(writer, "C%s %d %s\n", fileMode, fileInfo.Size(), filepath.Base(remote))
	if err != nil {
		return 0, err
	}
	n, err := copyN(writer, localFile, fileInfo.Size())
	if err != nil {
		return 0, err
	}
	ackErr := ack(writer)

	err = session.Wait()
	log.Debugf("Copied %v bytes out of %v. err: %v stdout:%v. stderr:%v", n, fileInfo.Size(), err, stdout, stderr)
	//NOTE: Process exited with status 1 is not an error, it just how scp work. (waiting for the next control message and we send EOF)

	err = checkForErrors(stdout.String())
	if err != nil {
		return 0, err
	}

	if ackErr != nil {
		return 0, ackErr
	}

	return n, nil
}

//CopyFrom copy from remote to local
func CopyFrom(sshClient *ssh.Client, remote string, local string) (int64, error) {
	session, err := sshClient.NewSession()
	if err != nil {
		return 0, err
	}
	defer session.Close()
	stderr := &bytes.Buffer{}
	session.Stderr = stderr
	writer, err := session.StdinPipe()
	if err != nil {
		return 0, err
	}
	defer writer.Close()
	reader, err := session.StdoutPipe()
	if err != nil {
		return 0, err
	}
	err = session.Start("scp -f " + remote)
	if err != nil {
		return 0, err
	}
	err = ack(writer)
	if err != nil {
		return 0, err
	}
	msg, err := NewMessageFromReader(reader)
	if err != nil {
		return 0, err
	}
	if msg.Type == ErrorMessage || msg.Type == WarnMessage {
		return 0, msg.Error
	}
	log.Debugf("Receiving %v", msg)

	err = ack(writer)
	if err != nil {
		return 0, err
	}
	outFile, err := os.Create(local)
	if err != nil {
		return 0, err
	}
	defer outFile.Close()
	n, err := copyN(outFile, reader, msg.Size)
	if err != nil {
		return 0, err
	}
	err = outFile.Sync()
	if err != nil {
		return 0, err
	}
	err = outFile.Close()
	if err != nil {
		return 0, err
	}
	err = session.Wait()
	log.Debugf("Copied %v bytes out of %v. err: %v stderr:%v", n, msg.Size, err, stderr)
	return n, nil
}

func ack(writer io.Writer) error {
	var msg = []byte{0, 0, 10, 13}
	n, err := writer.Write(msg)
	if err != nil {
		return fmt.Errorf("failed to write ack: %w", err)
	}
	if n < len(msg) {
		return errors.New("failed to write ack buffer fully")
	}
	return nil
}

func copyN(writer io.Writer, src io.Reader, size int64) (int64, error) {
	reader := io.LimitReader(src, size)
	var total int64
	for total < size {
		n, err := io.CopyBuffer(writer, reader, make([]byte, buffSize))
		log.Debugf("Copied chunk %v total: %v out of %v err: %v ", n, total, size, err)
		if err != nil {
			return 0, err
		}
		total += n
	}
	return total, nil
}

func checkForErrors(output string) error {
	if strings.Contains(output, "Permission denied") {
		return fmt.Errorf("permission denied")
	}

	return nil
}