/
request-server.go
186 lines (166 loc) · 4.26 KB
/
request-server.go
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package sftp
import (
"io"
"os"
"path/filepath"
"strconv"
"sync"
"syscall"
"github.com/pkg/errors"
)
var maxTxPacket uint32 = 1 << 15
type handleHandler func(string) string
// Handlers contains the 4 SFTP server request handlers.
type Handlers struct {
FileGet FileReader
FilePut FileWriter
FileCmd FileCmder
FileInfo FileInfoer
}
// RequestServer abstracts the sftp protocol with an http request-like protocol
type RequestServer struct {
serverConn
Handlers Handlers
pktChan chan packet
openRequests map[string]Request
openRequestLock sync.RWMutex
handleCount int
}
// NewRequestServer creates/allocates/returns new RequestServer.
// Normally there there will be one server per user-session.
func NewRequestServer(rwc io.ReadWriteCloser, h Handlers) *RequestServer {
return &RequestServer{
serverConn: serverConn{
conn: conn{
Reader: rwc,
WriteCloser: rwc,
},
},
Handlers: h,
pktChan: make(chan packet, sftpServerWorkerCount),
openRequests: make(map[string]Request),
}
}
func (rs *RequestServer) nextRequest(r Request) string {
rs.openRequestLock.Lock()
defer rs.openRequestLock.Unlock()
rs.handleCount++
handle := strconv.Itoa(rs.handleCount)
rs.openRequests[handle] = r
return handle
}
func (rs *RequestServer) getRequest(handle string) (Request, bool) {
rs.openRequestLock.RLock()
defer rs.openRequestLock.RUnlock()
r, ok := rs.openRequests[handle]
return r, ok
}
func (rs *RequestServer) closeRequest(handle string) {
rs.openRequestLock.Lock()
defer rs.openRequestLock.Unlock()
if r, ok := rs.openRequests[handle]; ok {
r.close()
delete(rs.openRequests, handle)
}
}
// Close the read/write/closer to trigger exiting the main server loop
func (rs *RequestServer) Close() error { return rs.conn.Close() }
// Serve requests for user session
func (rs *RequestServer) Serve() error {
var wg sync.WaitGroup
wg.Add(sftpServerWorkerCount)
for i := 0; i < sftpServerWorkerCount; i++ {
go func() {
defer wg.Done()
if err := rs.packetWorker(); err != nil {
rs.conn.Close() // shuts down recvPacket
}
}()
}
var err error
var pktType uint8
var pktBytes []byte
for {
pktType, pktBytes, err = rs.recvPacket()
if err != nil {
break
}
pkt, err := makePacket(rxPacket{fxp(pktType), pktBytes})
if err != nil {
break
}
rs.pktChan <- pkt
}
close(rs.pktChan) // shuts down sftpServerWorkers
wg.Wait() // wait for all workers to exit
return err
}
func (rs *RequestServer) packetWorker() error {
for pkt := range rs.pktChan {
var rpkt responsePacket
switch pkt := pkt.(type) {
case *sshFxInitPacket:
rpkt = sshFxVersionPacket{sftpProtocolVersion, nil}
case *sshFxpClosePacket:
handle := pkt.getHandle()
rs.closeRequest(handle)
rpkt = statusFromError(pkt, nil)
case *sshFxpRealpathPacket:
rpkt = cleanPath(pkt)
case isOpener:
handle := rs.nextRequest(requestFromPacket(pkt))
rpkt = sshFxpHandlePacket{pkt.id(), handle}
case hasHandle:
handle := pkt.getHandle()
request, ok := rs.getRequest(handle)
request.update(pkt)
if !ok {
rpkt = statusFromError(pkt, syscall.EBADF)
} else {
rpkt = rs.handle(request, pkt)
}
case hasPath:
request := requestFromPacket(pkt)
rpkt = rs.handle(request, pkt)
default:
return errors.Errorf("unexpected packet type %T", pkt)
}
err := rs.sendPacket(rpkt)
if err != nil {
return err
}
}
return nil
}
func cleanPath(pkt *sshFxpRealpathPacket) responsePacket {
path := pkt.getPath()
if !filepath.IsAbs(path) {
path = "/" + path
} // all paths are absolute
cleaned_path := filepath.Clean(path)
return &sshFxpNamePacket{
ID: pkt.id(),
NameAttrs: []sshFxpNameAttr{{
Name: cleaned_path,
LongName: cleaned_path,
Attrs: emptyFileStat,
}},
}
}
func (rs *RequestServer) handle(request Request, pkt packet) responsePacket {
// fmt.Println("Request Method: ", request.Method)
rpkt, err := request.handle(rs.Handlers)
if err != nil {
err = errorAdapter(err)
rpkt = statusFromError(pkt, err)
}
return rpkt
}
// os.ErrNotExist should convert to ssh_FX_NO_SUCH_FILE, but is not recognized
// by statusFromError. So we convert to syscall.ENOENT which it does.
func errorAdapter(err error) error {
if err == os.ErrNotExist {
return syscall.ENOENT
}
return err
}