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mirror of https://github.com/rclone/rclone synced 2024-12-05 15:55:18 +01:00
rclone/cmd/serve/sftp/connection.go
Nick Craig-Wood 71e172a139 serve/sftp: support empty "md5sum" and "sha1sum" commands
This is to enable the new command detection to work with the sftp
backend.
2019-08-14 20:54:08 +01:00

266 lines
6.7 KiB
Go

// +build !plan9
package sftp
import (
"context"
"fmt"
"io"
"net"
"regexp"
"strings"
"github.com/pkg/errors"
"github.com/pkg/sftp"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/hash"
"github.com/rclone/rclone/vfs"
"golang.org/x/crypto/ssh"
)
func describeConn(c interface {
RemoteAddr() net.Addr
LocalAddr() net.Addr
}) string {
return fmt.Sprintf("serve sftp %s->%s", c.RemoteAddr(), c.LocalAddr())
}
// Return the exit status of the command
type exitStatus struct {
RC uint32
}
// The incoming exec command
type execCommand struct {
Command string
}
var shellUnEscapeRegex = regexp.MustCompile(`\\(.)`)
// Unescape a string that was escaped by rclone
func shellUnEscape(str string) string {
str = strings.Replace(str, "'\n'", "\n", -1)
str = shellUnEscapeRegex.ReplaceAllString(str, `$1`)
return str
}
// Info about the current connection
type conn struct {
vfs *vfs.VFS
handlers sftp.Handlers
what string
}
// execCommand implements an extrememly limited number of commands to
// interoperate with the rclone sftp backend
func (c *conn) execCommand(ctx context.Context, out io.Writer, command string) (err error) {
binary, args := command, ""
space := strings.Index(command, " ")
if space >= 0 {
binary = command[:space]
args = strings.TrimLeft(command[space+1:], " ")
}
args = shellUnEscape(args)
fs.Debugf(c.what, "exec command: binary = %q, args = %q", binary, args)
switch binary {
case "df":
about := c.vfs.Fs().Features().About
if about == nil {
return errors.New("df not supported")
}
usage, err := about(ctx)
if err != nil {
return errors.Wrap(err, "About failed")
}
total, used, free := int64(-1), int64(-1), int64(-1)
if usage.Total != nil {
total = *usage.Total / 1024
}
if usage.Used != nil {
used = *usage.Used / 1024
}
if usage.Free != nil {
free = *usage.Free / 1024
}
perc := int64(0)
if total > 0 && used >= 0 {
perc = (100 * used) / total
}
_, err = fmt.Fprintf(out, ` Filesystem 1K-blocks Used Available Use%% Mounted on
/dev/root %d %d %d %d%% /
`, total, used, free, perc)
if err != nil {
return errors.Wrap(err, "send output failed")
}
case "md5sum", "sha1sum":
ht := hash.MD5
if binary == "sha1sum" {
ht = hash.SHA1
}
var hashSum string
if args == "" {
// empty hash for no input
if ht == hash.MD5 {
hashSum = "d41d8cd98f00b204e9800998ecf8427e"
} else {
hashSum = "da39a3ee5e6b4b0d3255bfef95601890afd80709"
}
args = "-"
} else {
node, err := c.vfs.Stat(args)
if err != nil {
return errors.Wrapf(err, "hash failed finding file %q", args)
}
if node.IsDir() {
return errors.New("can't hash directory")
}
o, ok := node.DirEntry().(fs.ObjectInfo)
if !ok {
return errors.New("unexpected non file")
}
hashSum, err = o.Hash(ctx, ht)
if err != nil {
return errors.Wrap(err, "hash failed")
}
}
_, err = fmt.Fprintf(out, "%s %s\n", hashSum, args)
if err != nil {
return errors.Wrap(err, "send output failed")
}
case "echo":
// special cases for rclone command detection
switch args {
case "'abc' | md5sum":
if c.vfs.Fs().Hashes().Contains(hash.MD5) {
_, err = fmt.Fprintf(out, "0bee89b07a248e27c83fc3d5951213c1 -\n")
if err != nil {
return errors.Wrap(err, "send output failed")
}
} else {
return errors.New("md5 hash not supported")
}
case "'abc' | sha1sum":
if c.vfs.Fs().Hashes().Contains(hash.SHA1) {
_, err = fmt.Fprintf(out, "03cfd743661f07975fa2f1220c5194cbaff48451 -\n")
if err != nil {
return errors.Wrap(err, "send output failed")
}
} else {
return errors.New("sha1 hash not supported")
}
default:
_, err = fmt.Fprintf(out, "%s\n", args)
if err != nil {
return errors.Wrap(err, "send output failed")
}
}
default:
return errors.Errorf("%q not implemented\n", command)
}
return nil
}
// handle a new incoming channel request
func (c *conn) handleChannel(newChannel ssh.NewChannel) {
fs.Debugf(c.what, "Incoming channel: %s\n", newChannel.ChannelType())
if newChannel.ChannelType() != "session" {
err := newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
fs.Debugf(c.what, "Unknown channel type: %s\n", newChannel.ChannelType())
if err != nil {
fs.Errorf(c.what, "Failed to reject unknown channel: %v", err)
}
return
}
channel, requests, err := newChannel.Accept()
if err != nil {
fs.Errorf(c.what, "could not accept channel: %v", err)
return
}
defer func() {
err := channel.Close()
if err != nil && err != io.EOF {
fs.Debugf(c.what, "Failed to close channel: %v", err)
}
}()
fs.Debugf(c.what, "Channel accepted\n")
isSFTP := make(chan bool, 1)
var command execCommand
// Handle out-of-band requests
go func(in <-chan *ssh.Request) {
for req := range in {
fs.Debugf(c.what, "Request: %v\n", req.Type)
ok := false
var subSystemIsSFTP bool
var reply []byte
switch req.Type {
case "subsystem":
fs.Debugf(c.what, "Subsystem: %s\n", req.Payload[4:])
if string(req.Payload[4:]) == "sftp" {
ok = true
subSystemIsSFTP = true
}
case "exec":
err := ssh.Unmarshal(req.Payload, &command)
if err != nil {
fs.Errorf(c.what, "ignoring bad exec command: %v", err)
} else {
ok = true
subSystemIsSFTP = false
}
}
fs.Debugf(c.what, " - accepted: %v\n", ok)
err = req.Reply(ok, reply)
if err != nil {
fs.Errorf(c.what, "Failed to Reply to request: %v", err)
return
}
if ok {
// Wake up main routine after we have responded
isSFTP <- subSystemIsSFTP
}
}
}(requests)
// Wait for either subsystem "sftp" or "exec" request
if <-isSFTP {
fs.Debugf(c.what, "Starting SFTP server")
server := sftp.NewRequestServer(channel, c.handlers)
defer func() {
err := server.Close()
if err != nil && err != io.EOF {
fs.Debugf(c.what, "Failed to close server: %v", err)
}
}()
err = server.Serve()
if err == io.EOF || err == nil {
fs.Debugf(c.what, "exited session")
} else {
fs.Errorf(c.what, "completed with error: %v", err)
}
} else {
var rc = uint32(0)
err := c.execCommand(context.TODO(), channel, command.Command)
if err != nil {
rc = 1
_, errPrint := fmt.Fprintf(channel.Stderr(), "%v\n", err)
if errPrint != nil {
fs.Errorf(c.what, "Failed to write to stderr: %v", errPrint)
}
fs.Debugf(c.what, "command %q failed with error: %v", command.Command, err)
}
_, err = channel.SendRequest("exit-status", false, ssh.Marshal(exitStatus{RC: rc}))
if err != nil {
fs.Errorf(c.what, "Failed to send exit status: %v", err)
}
}
}
// Service the incoming Channel channel in go routine
func (c *conn) handleChannels(chans <-chan ssh.NewChannel) {
for newChannel := range chans {
go c.handleChannel(newChannel)
}
}