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restic/vendor/github.com/pkg/sftp/server.go
2018-09-08 21:17:22 +02:00

680 lines
15 KiB
Go

package sftp
// sftp server counterpart
import (
"encoding"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"sync"
"syscall"
"time"
"github.com/pkg/errors"
)
const (
SftpServerWorkerCount = 8
)
// Server is an SSH File Transfer Protocol (sftp) server.
// This is intended to provide the sftp subsystem to an ssh server daemon.
// This implementation currently supports most of sftp server protocol version 3,
// as specified at http://tools.ietf.org/html/draft-ietf-secsh-filexfer-02
type Server struct {
*serverConn
debugStream io.Writer
readOnly bool
pktMgr *packetManager
openFiles map[string]*os.File
openFilesLock sync.RWMutex
handleCount int
maxTxPacket uint32
}
func (svr *Server) nextHandle(f *os.File) string {
svr.openFilesLock.Lock()
defer svr.openFilesLock.Unlock()
svr.handleCount++
handle := strconv.Itoa(svr.handleCount)
svr.openFiles[handle] = f
return handle
}
func (svr *Server) closeHandle(handle string) error {
svr.openFilesLock.Lock()
defer svr.openFilesLock.Unlock()
if f, ok := svr.openFiles[handle]; ok {
delete(svr.openFiles, handle)
return f.Close()
}
return syscall.EBADF
}
func (svr *Server) getHandle(handle string) (*os.File, bool) {
svr.openFilesLock.RLock()
defer svr.openFilesLock.RUnlock()
f, ok := svr.openFiles[handle]
return f, ok
}
type serverRespondablePacket interface {
encoding.BinaryUnmarshaler
id() uint32
respond(svr *Server) responsePacket
}
// NewServer creates a new Server instance around the provided streams, serving
// content from the root of the filesystem. Optionally, ServerOption
// functions may be specified to further configure the Server.
//
// A subsequent call to Serve() is required to begin serving files over SFTP.
func NewServer(rwc io.ReadWriteCloser, options ...ServerOption) (*Server, error) {
svrConn := &serverConn{
conn: conn{
Reader: rwc,
WriteCloser: rwc,
},
}
s := &Server{
serverConn: svrConn,
debugStream: ioutil.Discard,
pktMgr: newPktMgr(svrConn),
openFiles: make(map[string]*os.File),
maxTxPacket: 1 << 15,
}
for _, o := range options {
if err := o(s); err != nil {
return nil, err
}
}
return s, nil
}
// A ServerOption is a function which applies configuration to a Server.
type ServerOption func(*Server) error
// WithDebug enables Server debugging output to the supplied io.Writer.
func WithDebug(w io.Writer) ServerOption {
return func(s *Server) error {
s.debugStream = w
return nil
}
}
// ReadOnly configures a Server to serve files in read-only mode.
func ReadOnly() ServerOption {
return func(s *Server) error {
s.readOnly = true
return nil
}
}
type rxPacket struct {
pktType fxp
pktBytes []byte
}
// Up to N parallel servers
func (svr *Server) sftpServerWorker(pktChan chan orderedRequest) error {
for pkt := range pktChan {
// readonly checks
readonly := true
switch pkt := pkt.requestPacket.(type) {
case notReadOnly:
readonly = false
case *sshFxpOpenPacket:
readonly = pkt.readonly()
case *sshFxpExtendedPacket:
readonly = pkt.readonly()
}
// If server is operating read-only and a write operation is requested,
// return permission denied
if !readonly && svr.readOnly {
svr.sendPacket(orderedResponse{
responsePacket: statusFromError(pkt, syscall.EPERM),
orderid: pkt.orderId()})
continue
}
if err := handlePacket(svr, pkt); err != nil {
return err
}
}
return nil
}
func handlePacket(s *Server, p orderedRequest) error {
var rpkt responsePacket
switch p := p.requestPacket.(type) {
case *sshFxInitPacket:
rpkt = sshFxVersionPacket{Version: sftpProtocolVersion}
case *sshFxpStatPacket:
// stat the requested file
info, err := os.Stat(p.Path)
rpkt = sshFxpStatResponse{
ID: p.ID,
info: info,
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpLstatPacket:
// stat the requested file
info, err := os.Lstat(p.Path)
rpkt = sshFxpStatResponse{
ID: p.ID,
info: info,
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpFstatPacket:
f, ok := s.getHandle(p.Handle)
var err error = syscall.EBADF
var info os.FileInfo
if ok {
info, err = f.Stat()
rpkt = sshFxpStatResponse{
ID: p.ID,
info: info,
}
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpMkdirPacket:
// TODO FIXME: ignore flags field
err := os.Mkdir(p.Path, 0755)
rpkt = statusFromError(p, err)
case *sshFxpRmdirPacket:
err := os.Remove(p.Path)
rpkt = statusFromError(p, err)
case *sshFxpRemovePacket:
err := os.Remove(p.Filename)
rpkt = statusFromError(p, err)
case *sshFxpRenamePacket:
err := os.Rename(p.Oldpath, p.Newpath)
rpkt = statusFromError(p, err)
case *sshFxpSymlinkPacket:
err := os.Symlink(p.Targetpath, p.Linkpath)
rpkt = statusFromError(p, err)
case *sshFxpClosePacket:
rpkt = statusFromError(p, s.closeHandle(p.Handle))
case *sshFxpReadlinkPacket:
f, err := os.Readlink(p.Path)
rpkt = sshFxpNamePacket{
ID: p.ID,
NameAttrs: []sshFxpNameAttr{{
Name: f,
LongName: f,
Attrs: emptyFileStat,
}},
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpRealpathPacket:
f, err := filepath.Abs(p.Path)
f = cleanPath(f)
rpkt = sshFxpNamePacket{
ID: p.ID,
NameAttrs: []sshFxpNameAttr{{
Name: f,
LongName: f,
Attrs: emptyFileStat,
}},
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpOpendirPacket:
if stat, err := os.Stat(p.Path); err != nil {
rpkt = statusFromError(p, err)
} else if !stat.IsDir() {
rpkt = statusFromError(p, &os.PathError{
Path: p.Path, Err: syscall.ENOTDIR})
} else {
rpkt = sshFxpOpenPacket{
ID: p.ID,
Path: p.Path,
Pflags: ssh_FXF_READ,
}.respond(s)
}
case *sshFxpReadPacket:
var err error = syscall.EBADF
f, ok := s.getHandle(p.Handle)
if ok {
err = nil
data := make([]byte, clamp(p.Len, s.maxTxPacket))
n, _err := f.ReadAt(data, int64(p.Offset))
if _err != nil && (_err != io.EOF || n == 0) {
err = _err
}
rpkt = sshFxpDataPacket{
ID: p.ID,
Length: uint32(n),
Data: data[:n],
}
}
if err != nil {
rpkt = statusFromError(p, err)
}
case *sshFxpWritePacket:
f, ok := s.getHandle(p.Handle)
var err error = syscall.EBADF
if ok {
_, err = f.WriteAt(p.Data, int64(p.Offset))
}
rpkt = statusFromError(p, err)
case serverRespondablePacket:
rpkt = p.respond(s)
default:
return errors.Errorf("unexpected packet type %T", p)
}
s.pktMgr.readyPacket(s.pktMgr.newOrderedResponse(rpkt, p.orderId()))
return nil
}
// Serve serves SFTP connections until the streams stop or the SFTP subsystem
// is stopped.
func (svr *Server) Serve() error {
var wg sync.WaitGroup
runWorker := func(ch chan orderedRequest) {
wg.Add(1)
go func() {
defer wg.Done()
if err := svr.sftpServerWorker(ch); err != nil {
svr.conn.Close() // shuts down recvPacket
}
}()
}
pktChan := svr.pktMgr.workerChan(runWorker)
var err error
var pkt requestPacket
var pktType uint8
var pktBytes []byte
for {
pktType, pktBytes, err = svr.recvPacket()
if err != nil {
break
}
pkt, err = makePacket(rxPacket{fxp(pktType), pktBytes})
if err != nil {
switch errors.Cause(err) {
case errUnknownExtendedPacket:
if err := svr.serverConn.sendError(pkt, ErrSshFxOpUnsupported); err != nil {
debug("failed to send err packet: %v", err)
svr.conn.Close() // shuts down recvPacket
break
}
default:
debug("makePacket err: %v", err)
svr.conn.Close() // shuts down recvPacket
break
}
}
pktChan <- svr.pktMgr.newOrderedRequest(pkt)
}
close(pktChan) // shuts down sftpServerWorkers
wg.Wait() // wait for all workers to exit
// close any still-open files
for handle, file := range svr.openFiles {
fmt.Fprintf(svr.debugStream, "sftp server file with handle %q left open: %v\n", handle, file.Name())
file.Close()
}
return err // error from recvPacket
}
type ider interface {
id() uint32
}
// The init packet has no ID, so we just return a zero-value ID
func (p sshFxInitPacket) id() uint32 { return 0 }
type sshFxpStatResponse struct {
ID uint32
info os.FileInfo
}
func (p sshFxpStatResponse) MarshalBinary() ([]byte, error) {
b := []byte{ssh_FXP_ATTRS}
b = marshalUint32(b, p.ID)
b = marshalFileInfo(b, p.info)
return b, nil
}
var emptyFileStat = []interface{}{uint32(0)}
func (p sshFxpOpenPacket) readonly() bool {
return !p.hasPflags(ssh_FXF_WRITE)
}
func (p sshFxpOpenPacket) hasPflags(flags ...uint32) bool {
for _, f := range flags {
if p.Pflags&f == 0 {
return false
}
}
return true
}
func (p sshFxpOpenPacket) respond(svr *Server) responsePacket {
var osFlags int
if p.hasPflags(ssh_FXF_READ, ssh_FXF_WRITE) {
osFlags |= os.O_RDWR
} else if p.hasPflags(ssh_FXF_WRITE) {
osFlags |= os.O_WRONLY
} else if p.hasPflags(ssh_FXF_READ) {
osFlags |= os.O_RDONLY
} else {
// how are they opening?
return statusFromError(p, syscall.EINVAL)
}
if p.hasPflags(ssh_FXF_APPEND) {
osFlags |= os.O_APPEND
}
if p.hasPflags(ssh_FXF_CREAT) {
osFlags |= os.O_CREATE
}
if p.hasPflags(ssh_FXF_TRUNC) {
osFlags |= os.O_TRUNC
}
if p.hasPflags(ssh_FXF_EXCL) {
osFlags |= os.O_EXCL
}
f, err := os.OpenFile(p.Path, osFlags, 0644)
if err != nil {
return statusFromError(p, err)
}
handle := svr.nextHandle(f)
return sshFxpHandlePacket{ID: p.id(), Handle: handle}
}
func (p sshFxpReaddirPacket) respond(svr *Server) responsePacket {
f, ok := svr.getHandle(p.Handle)
if !ok {
return statusFromError(p, syscall.EBADF)
}
dirname := f.Name()
dirents, err := f.Readdir(128)
if err != nil {
return statusFromError(p, err)
}
ret := sshFxpNamePacket{ID: p.ID}
for _, dirent := range dirents {
ret.NameAttrs = append(ret.NameAttrs, sshFxpNameAttr{
Name: dirent.Name(),
LongName: runLs(dirname, dirent),
Attrs: []interface{}{dirent},
})
}
return ret
}
func (p sshFxpSetstatPacket) respond(svr *Server) responsePacket {
// additional unmarshalling is required for each possibility here
b := p.Attrs.([]byte)
var err error
debug("setstat name \"%s\"", p.Path)
if (p.Flags & ssh_FILEXFER_ATTR_SIZE) != 0 {
var size uint64
if size, b, err = unmarshalUint64Safe(b); err == nil {
err = os.Truncate(p.Path, int64(size))
}
}
if (p.Flags & ssh_FILEXFER_ATTR_PERMISSIONS) != 0 {
var mode uint32
if mode, b, err = unmarshalUint32Safe(b); err == nil {
err = os.Chmod(p.Path, os.FileMode(mode))
}
}
if (p.Flags & ssh_FILEXFER_ATTR_ACMODTIME) != 0 {
var atime uint32
var mtime uint32
if atime, b, err = unmarshalUint32Safe(b); err != nil {
} else if mtime, b, err = unmarshalUint32Safe(b); err != nil {
} else {
atimeT := time.Unix(int64(atime), 0)
mtimeT := time.Unix(int64(mtime), 0)
err = os.Chtimes(p.Path, atimeT, mtimeT)
}
}
if (p.Flags & ssh_FILEXFER_ATTR_UIDGID) != 0 {
var uid uint32
var gid uint32
if uid, b, err = unmarshalUint32Safe(b); err != nil {
} else if gid, _, err = unmarshalUint32Safe(b); err != nil {
} else {
err = os.Chown(p.Path, int(uid), int(gid))
}
}
return statusFromError(p, err)
}
func (p sshFxpFsetstatPacket) respond(svr *Server) responsePacket {
f, ok := svr.getHandle(p.Handle)
if !ok {
return statusFromError(p, syscall.EBADF)
}
// additional unmarshalling is required for each possibility here
b := p.Attrs.([]byte)
var err error
debug("fsetstat name \"%s\"", f.Name())
if (p.Flags & ssh_FILEXFER_ATTR_SIZE) != 0 {
var size uint64
if size, b, err = unmarshalUint64Safe(b); err == nil {
err = f.Truncate(int64(size))
}
}
if (p.Flags & ssh_FILEXFER_ATTR_PERMISSIONS) != 0 {
var mode uint32
if mode, b, err = unmarshalUint32Safe(b); err == nil {
err = f.Chmod(os.FileMode(mode))
}
}
if (p.Flags & ssh_FILEXFER_ATTR_ACMODTIME) != 0 {
var atime uint32
var mtime uint32
if atime, b, err = unmarshalUint32Safe(b); err != nil {
} else if mtime, b, err = unmarshalUint32Safe(b); err != nil {
} else {
atimeT := time.Unix(int64(atime), 0)
mtimeT := time.Unix(int64(mtime), 0)
err = os.Chtimes(f.Name(), atimeT, mtimeT)
}
}
if (p.Flags & ssh_FILEXFER_ATTR_UIDGID) != 0 {
var uid uint32
var gid uint32
if uid, b, err = unmarshalUint32Safe(b); err != nil {
} else if gid, _, err = unmarshalUint32Safe(b); err != nil {
} else {
err = f.Chown(int(uid), int(gid))
}
}
return statusFromError(p, err)
}
// translateErrno translates a syscall error number to a SFTP error code.
func translateErrno(errno syscall.Errno) uint32 {
switch errno {
case 0:
return ssh_FX_OK
case syscall.ENOENT:
return ssh_FX_NO_SUCH_FILE
case syscall.EPERM:
return ssh_FX_PERMISSION_DENIED
}
return ssh_FX_FAILURE
}
func statusFromError(p ider, err error) sshFxpStatusPacket {
ret := sshFxpStatusPacket{
ID: p.id(),
StatusError: StatusError{
// ssh_FX_OK = 0
// ssh_FX_EOF = 1
// ssh_FX_NO_SUCH_FILE = 2 ENOENT
// ssh_FX_PERMISSION_DENIED = 3
// ssh_FX_FAILURE = 4
// ssh_FX_BAD_MESSAGE = 5
// ssh_FX_NO_CONNECTION = 6
// ssh_FX_CONNECTION_LOST = 7
// ssh_FX_OP_UNSUPPORTED = 8
Code: ssh_FX_OK,
},
}
if err == nil {
return ret
}
debug("statusFromError: error is %T %#v", err, err)
ret.StatusError.Code = ssh_FX_FAILURE
ret.StatusError.msg = err.Error()
switch e := err.(type) {
case syscall.Errno:
ret.StatusError.Code = translateErrno(e)
case *os.PathError:
debug("statusFromError,pathError: error is %T %#v", e.Err, e.Err)
if errno, ok := e.Err.(syscall.Errno); ok {
ret.StatusError.Code = translateErrno(errno)
}
case fxerr:
ret.StatusError.Code = uint32(e)
default:
switch e {
case io.EOF:
ret.StatusError.Code = ssh_FX_EOF
case os.ErrNotExist:
ret.StatusError.Code = ssh_FX_NO_SUCH_FILE
}
}
return ret
}
func clamp(v, max uint32) uint32 {
if v > max {
return max
}
return v
}
func runLsTypeWord(dirent os.FileInfo) string {
// find first character, the type char
// b Block special file.
// c Character special file.
// d Directory.
// l Symbolic link.
// s Socket link.
// p FIFO.
// - Regular file.
tc := '-'
mode := dirent.Mode()
if (mode & os.ModeDir) != 0 {
tc = 'd'
} else if (mode & os.ModeDevice) != 0 {
tc = 'b'
if (mode & os.ModeCharDevice) != 0 {
tc = 'c'
}
} else if (mode & os.ModeSymlink) != 0 {
tc = 'l'
} else if (mode & os.ModeSocket) != 0 {
tc = 's'
} else if (mode & os.ModeNamedPipe) != 0 {
tc = 'p'
}
// owner
orc := '-'
if (mode & 0400) != 0 {
orc = 'r'
}
owc := '-'
if (mode & 0200) != 0 {
owc = 'w'
}
oxc := '-'
ox := (mode & 0100) != 0
setuid := (mode & os.ModeSetuid) != 0
if ox && setuid {
oxc = 's'
} else if setuid {
oxc = 'S'
} else if ox {
oxc = 'x'
}
// group
grc := '-'
if (mode & 040) != 0 {
grc = 'r'
}
gwc := '-'
if (mode & 020) != 0 {
gwc = 'w'
}
gxc := '-'
gx := (mode & 010) != 0
setgid := (mode & os.ModeSetgid) != 0
if gx && setgid {
gxc = 's'
} else if setgid {
gxc = 'S'
} else if gx {
gxc = 'x'
}
// all / others
arc := '-'
if (mode & 04) != 0 {
arc = 'r'
}
awc := '-'
if (mode & 02) != 0 {
awc = 'w'
}
axc := '-'
ax := (mode & 01) != 0
sticky := (mode & os.ModeSticky) != 0
if ax && sticky {
axc = 't'
} else if sticky {
axc = 'T'
} else if ax {
axc = 'x'
}
return fmt.Sprintf("%c%c%c%c%c%c%c%c%c%c", tc, orc, owc, oxc, grc, gwc, gxc, arc, awc, axc)
}