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request-server.go
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request-server.go
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package sftp
import (
"context"
"errors"
"io"
"path"
"path/filepath"
"strconv"
"sync"
)
var maxTxPacket uint32 = 1 << 15
// Handlers contains the 4 SFTP server request handlers.
type Handlers struct {
FileGet FileReader
FilePut FileWriter
FileCmd FileCmder
FileList FileLister
}
// RequestServer abstracts the sftp protocol with an http request-like protocol
type RequestServer struct {
Handlers Handlers
*serverConn
pktMgr *packetManager
startDirectory string
mu sync.RWMutex
handleCount int
openRequests map[string]*Request
}
// A RequestServerOption is a function which applies configuration to a RequestServer.
type RequestServerOption func(*RequestServer)
// WithRSAllocator enable the allocator.
// After processing a packet we keep in memory the allocated slices
// and we reuse them for new packets.
// The allocator is experimental
func WithRSAllocator() RequestServerOption {
return func(rs *RequestServer) {
alloc := newAllocator()
rs.pktMgr.alloc = alloc
rs.conn.alloc = alloc
}
}
// WithStartDirectory sets a start directory to use as base for relative paths.
// If unset the default is "/"
func WithStartDirectory(startDirectory string) RequestServerOption {
return func(rs *RequestServer) {
rs.startDirectory = cleanPath(startDirectory)
}
}
// NewRequestServer creates/allocates/returns new RequestServer.
// Normally there will be one server per user-session.
func NewRequestServer(rwc io.ReadWriteCloser, h Handlers, options ...RequestServerOption) *RequestServer {
svrConn := &serverConn{
conn: conn{
Reader: rwc,
WriteCloser: rwc,
},
}
rs := &RequestServer{
Handlers: h,
serverConn: svrConn,
pktMgr: newPktMgr(svrConn),
startDirectory: "/",
openRequests: make(map[string]*Request),
}
for _, o := range options {
o(rs)
}
return rs
}
// New Open packet/Request
func (rs *RequestServer) nextRequest(r *Request) string {
rs.mu.Lock()
defer rs.mu.Unlock()
rs.handleCount++
r.handle = strconv.Itoa(rs.handleCount)
rs.openRequests[r.handle] = r
return r.handle
}
// Returns Request from openRequests, bool is false if it is missing.
//
// The Requests in openRequests work essentially as open file descriptors that
// you can do different things with. What you are doing with it are denoted by
// the first packet of that type (read/write/etc).
func (rs *RequestServer) getRequest(handle string) (*Request, bool) {
rs.mu.RLock()
defer rs.mu.RUnlock()
r, ok := rs.openRequests[handle]
return r, ok
}
// Close the Request and clear from openRequests map
func (rs *RequestServer) closeRequest(handle string) error {
rs.mu.Lock()
defer rs.mu.Unlock()
if r, ok := rs.openRequests[handle]; ok {
delete(rs.openRequests, handle)
return r.close()
}
return EBADF
}
// Close the read/write/closer to trigger exiting the main server loop
func (rs *RequestServer) Close() error { return rs.conn.Close() }
func (rs *RequestServer) serveLoop(pktChan chan<- orderedRequest) error {
defer close(pktChan) // shuts down sftpServerWorkers
var err error
var pkt requestPacket
var pktType uint8
var pktBytes []byte
for {
pktType, pktBytes, err = rs.serverConn.recvPacket(rs.pktMgr.getNextOrderID())
if err != nil {
// we don't care about releasing allocated pages here, the server will quit and the allocator freed
return err
}
pkt, err = makePacket(rxPacket{fxp(pktType), pktBytes})
if err != nil {
switch {
case errors.Is(err, errUnknownExtendedPacket):
// do nothing
default:
debug("makePacket err: %v", err)
rs.conn.Close() // shuts down recvPacket
return err
}
}
pktChan <- rs.pktMgr.newOrderedRequest(pkt)
}
}
// Serve requests for user session
func (rs *RequestServer) Serve() error {
defer func() {
if rs.pktMgr.alloc != nil {
rs.pktMgr.alloc.Free()
}
}()
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
var wg sync.WaitGroup
runWorker := func(ch chan orderedRequest) {
wg.Add(1)
go func() {
defer wg.Done()
if err := rs.packetWorker(ctx, ch); err != nil {
rs.conn.Close() // shuts down recvPacket
}
}()
}
pktChan := rs.pktMgr.workerChan(runWorker)
err := rs.serveLoop(pktChan)
wg.Wait() // wait for all workers to exit
rs.mu.Lock()
defer rs.mu.Unlock()
// make sure all open requests are properly closed
// (eg. possible on dropped connections, client crashes, etc.)
for handle, req := range rs.openRequests {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
req.transferError(err)
delete(rs.openRequests, handle)
req.close()
}
return err
}
func (rs *RequestServer) packetWorker(ctx context.Context, pktChan chan orderedRequest) error {
for pkt := range pktChan {
orderID := pkt.orderID()
if epkt, ok := pkt.requestPacket.(*sshFxpExtendedPacket); ok {
if epkt.SpecificPacket != nil {
pkt.requestPacket = epkt.SpecificPacket
}
}
var rpkt responsePacket
switch pkt := pkt.requestPacket.(type) {
case *sshFxInitPacket:
rpkt = &sshFxVersionPacket{Version: sftpProtocolVersion, Extensions: sftpExtensions}
case *sshFxpClosePacket:
handle := pkt.getHandle()
rpkt = statusFromError(pkt.ID, rs.closeRequest(handle))
case *sshFxpRealpathPacket:
var realPath string
if realPather, ok := rs.Handlers.FileList.(RealPathFileLister); ok {
realPath = realPather.RealPath(pkt.getPath())
} else {
realPath = cleanPathWithBase(rs.startDirectory, pkt.getPath())
}
rpkt = cleanPacketPath(pkt, realPath)
case *sshFxpOpendirPacket:
request := requestFromPacket(ctx, pkt, rs.startDirectory)
handle := rs.nextRequest(request)
rpkt = request.opendir(rs.Handlers, pkt)
if _, ok := rpkt.(*sshFxpHandlePacket); !ok {
// if we return an error we have to remove the handle from the active ones
rs.closeRequest(handle)
}
case *sshFxpOpenPacket:
request := requestFromPacket(ctx, pkt, rs.startDirectory)
handle := rs.nextRequest(request)
rpkt = request.open(rs.Handlers, pkt)
if _, ok := rpkt.(*sshFxpHandlePacket); !ok {
// if we return an error we have to remove the handle from the active ones
rs.closeRequest(handle)
}
case *sshFxpFstatPacket:
handle := pkt.getHandle()
request, ok := rs.getRequest(handle)
if !ok {
rpkt = statusFromError(pkt.ID, EBADF)
} else {
request = &Request{
Method: "Stat",
Filepath: cleanPathWithBase(rs.startDirectory, request.Filepath),
}
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
}
case *sshFxpFsetstatPacket:
handle := pkt.getHandle()
request, ok := rs.getRequest(handle)
if !ok {
rpkt = statusFromError(pkt.ID, EBADF)
} else {
request = &Request{
Method: "Setstat",
Filepath: cleanPathWithBase(rs.startDirectory, request.Filepath),
}
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
}
case *sshFxpExtendedPacketPosixRename:
request := &Request{
Method: "PosixRename",
Filepath: cleanPathWithBase(rs.startDirectory, pkt.Oldpath),
Target: cleanPathWithBase(rs.startDirectory, pkt.Newpath),
}
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
case *sshFxpExtendedPacketStatVFS:
request := &Request{
Method: "StatVFS",
Filepath: cleanPathWithBase(rs.startDirectory, pkt.Path),
}
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
case hasHandle:
handle := pkt.getHandle()
request, ok := rs.getRequest(handle)
if !ok {
rpkt = statusFromError(pkt.id(), EBADF)
} else {
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
}
case hasPath:
request := requestFromPacket(ctx, pkt, rs.startDirectory)
rpkt = request.call(rs.Handlers, pkt, rs.pktMgr.alloc, orderID)
request.close()
default:
rpkt = statusFromError(pkt.id(), ErrSSHFxOpUnsupported)
}
rs.pktMgr.readyPacket(
rs.pktMgr.newOrderedResponse(rpkt, orderID))
}
return nil
}
// clean and return name packet for file
func cleanPacketPath(pkt *sshFxpRealpathPacket, realPath string) responsePacket {
return &sshFxpNamePacket{
ID: pkt.id(),
NameAttrs: []*sshFxpNameAttr{
{
Name: realPath,
LongName: realPath,
Attrs: emptyFileStat,
},
},
}
}
// Makes sure we have a clean POSIX (/) absolute path to work with
func cleanPath(p string) string {
return cleanPathWithBase("/", p)
}
func cleanPathWithBase(base, p string) string {
p = filepath.ToSlash(filepath.Clean(p))
if !path.IsAbs(p) {
return path.Join(base, p)
}
return p
}