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go.crypto/ssh: assorted close related fixes

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Fixes golang/go#3810.

Fixes chanWriter Write after close behaviour bug.

Fixes serverChan writePacket after close bug.

Addresses final comments by agl on 6405064, plus various cleanups.

R=agl, kardianos, gustav.paul, fullung
CC=golang-dev
https://golang.org/cl/6479056
This commit is contained in:
Dave Cheney
2012-09-05 09:47:02 +10:00
parent 06790d30c2
commit 552202b8e3
5 changed files with 51 additions and 60 deletions
Download Patch File Download Diff File Expand all files Collapse all files
ssh/channel.go
+45 -41
View File
@@ -82,7 +82,7 @@ type channel struct {
localId, remoteId uint32
remoteWin window
maxPacket uint32
isclosed uint32 // atomic bool, non zero if true
isClosed uint32 // atomic bool, non zero if true
}
func (c *channel) sendWindowAdj(n int) error {
@@ -93,13 +93,20 @@ func (c *channel) sendWindowAdj(n int) error {
return c.writePacket(marshal(msgChannelWindowAdjust, msg))
}
// sendEOF sends EOF to the server. RFC 4254 Section 5.3
// sendEOF sends EOF to the remote side. RFC 4254 Section 5.3
func (c *channel) sendEOF() error {
return c.writePacket(marshal(msgChannelEOF, channelEOFMsg{
PeersId: c.remoteId,
}))
}
// sendClose informs the remote side of our intent to close the channel.
func (c *channel) sendClose() error {
return c.conn.writePacket(marshal(msgChannelClose, channelCloseMsg{
PeersId: c.remoteId,
}))
}
func (c *channel) sendChannelOpenFailure(reason RejectionReason, message string) error {
reject := channelOpenFailureMsg{
PeersId: c.remoteId,
@@ -121,11 +128,11 @@ func (c *channel) writePacket(b []byte) error {
}
func (c *channel) closed() bool {
return atomic.LoadUint32(&c.isclosed) > 0
return atomic.LoadUint32(&c.isClosed) > 0
}
func (c *channel) setClosed() bool {
return atomic.CompareAndSwapUint32(&c.isclosed, 0, 1)
return atomic.CompareAndSwapUint32(&c.isClosed, 0, 1)
}
type serverChan struct {
@@ -136,10 +143,9 @@ type serverChan struct {
serverConn *ServerConn
myWindow uint32
weClosed bool // incidates the close msg has been sent from our side
theyClosed bool // indicates the close msg has been received from the remote side
theySentEOF bool
dead bool
isDead uint32
err error
pendingRequests []ChannelRequest
@@ -247,7 +253,7 @@ func (edc extendedDataChannel) Write(data []byte) (n int, err error) {
const headerLength = 13 // 1 byte message type, 4 bytes remoteId, 4 bytes extended message type, 4 bytes data length
c := edc.c
for len(data) > 0 {
space := uint32(min(int(c.maxPacket-headerLength), len(data)))
space := min(c.maxPacket-headerLength, len(data))
if space, err = c.getWindowSpace(space); err != nil {
return 0, err
}
@@ -297,7 +303,7 @@ func (c *serverChan) read(data []byte) (n int, err error, windowAdjustment uint3
}
for {
if c.theySentEOF || c.theyClosed || c.dead {
if c.theySentEOF || c.theyClosed || c.dead() {
return 0, io.EOF, 0
}
@@ -315,7 +321,7 @@ func (c *serverChan) read(data []byte) (n int, err error, windowAdjustment uint3
}
if c.length > 0 {
tail := min(c.head+c.length, len(c.pendingData))
tail := min(uint32(c.head+c.length), len(c.pendingData))
n = copy(data, c.pendingData[c.head:tail])
c.head += n
c.length -= n
@@ -341,24 +347,24 @@ func (c *serverChan) read(data []byte) (n int, err error, windowAdjustment uint3
// getWindowSpace takes, at most, max bytes of space from the peer's window. It
// returns the number of bytes actually reserved.
func (c *serverChan) getWindowSpace(max uint32) (uint32, error) {
var err error
// TODO(dfc) This lock and check of c.weClosed is necessary because unlike
// clientChan, c.weClosed is observed by more than one goroutine.
c.cond.L.Lock()
if c.dead || c.weClosed {
err = io.EOF
}
c.cond.L.Unlock()
if err != nil {
return 0, err
if c.dead() || c.closed() {
return 0, io.EOF
}
return c.remoteWin.reserve(max), nil
}
func (c *serverChan) dead() bool {
return atomic.LoadUint32(&c.isDead) > 0
}
func (c *serverChan) setDead() {
atomic.StoreUint32(&c.isDead, 1)
}
func (c *serverChan) Write(data []byte) (n int, err error) {
const headerLength = 9 // 1 byte message type, 4 bytes remoteId, 4 bytes data length
for len(data) > 0 {
space := uint32(min(int(c.maxPacket-headerLength), len(data)))
space := min(c.maxPacket-headerLength, len(data))
if space, err = c.getWindowSpace(space); err != nil {
return 0, err
}
@@ -384,6 +390,7 @@ func (c *serverChan) Write(data []byte) (n int, err error) {
return
}
// Close signals the intent to close the channel.
func (c *serverChan) Close() error {
c.serverConn.lock.Lock()
defer c.serverConn.lock.Unlock()
@@ -392,21 +399,12 @@ func (c *serverChan) Close() error {
return c.serverConn.err
}
if c.weClosed {
if !c.setClosed() {
return errors.New("ssh: channel already closed")
}
c.weClosed = true
return c.sendClose()
}
// sendClose signals the intent to close the channel.
func (c *serverChan) sendClose() error {
return c.writePacket(marshal(msgChannelClose, channelCloseMsg{
PeersId: c.remoteId,
}))
}
func (c *serverChan) AckRequest(ok bool) error {
c.serverConn.lock.Lock()
defer c.serverConn.lock.Unlock()
@@ -491,32 +489,37 @@ func (c *clientChan) waitForChannelOpenResponse() error {
return errors.New("ssh: unexpected packet")
}
// Close signals the intent to close the channel.
func (c *clientChan) Close() error {
if !c.setClosed() {
return errors.New("ssh: channel already closed")
}
c.stdout.eof()
c.stderr.eof()
close(c.msg)
// TODO(dfc) step around channel.writePacket() because closed() is now true
return c.channel.conn.writePacket(marshal(msgChannelClose, channelCloseMsg{
PeersId: c.remoteId,
}))
return c.sendClose()
}
// A chanWriter represents the stdin of a remote process.
type chanWriter struct {
*channel
// indicates the writer has been closed. eof is owned by the
// caller of Write/Close.
eof bool
}
// Write writes data to the remote process's standard input.
func (w *chanWriter) Write(data []byte) (written int, err error) {
const headerLength = 9 // 1 byte message type, 4 bytes remoteId, 4 bytes data length
for len(data) > 0 {
if w.eof || w.closed() {
err = io.EOF
return
}
// never send more data than maxPacket even if
// there is sufficent window.
n := min(int(w.maxPacket-headerLength), len(data))
n = int(w.remoteWin.reserve(uint32(n)))
n := min(w.maxPacket-headerLength, len(data))
r := w.remoteWin.reserve(n)
n = r
remoteId := w.remoteId
packet := []byte{
msgChannelData,
@@ -527,19 +530,20 @@ func (w *chanWriter) Write(data []byte) (written int, err error) {
break
}
data = data[n:]
written += n
written += int(n)
}
return
}
func min(a, b int) int {
if a < b {
func min(a uint32, b int) uint32 {
if a < uint32(b) {
return a
}
return b
return uint32(b)
}
func (w *chanWriter) Close() error {
w.eof = true
return w.sendEOF()
}
ssh/client.go
+4 -3
View File
@@ -249,7 +249,8 @@ func (c *ClientConn) mainLoop() {
ch.stderr.write(packet)
}
default:
switch msg := decode(packet).(type) {
msg := decode(packet)
switch msg := msg.(type) {
case *channelOpenMsg:
c.handleChanOpen(msg)
case *channelOpenConfirmMsg:
@@ -270,8 +271,7 @@ func (c *ClientConn) mainLoop() {
return
}
ch.Close()
// TODO(dfc) may need to optimisically remove the
// channel before closing
close(ch.msg)
c.chanList.remove(msg.PeersId)
case *channelEOFMsg:
ch, ok := c.getChan(msg.PeersId)
@@ -502,5 +502,6 @@ func (c *chanList) closeAll() {
continue
}
ch.Close()
close(ch.msg)
}
}
ssh/server.go
+1 -1
View File
@@ -536,7 +536,7 @@ func (s *ServerConn) Accept() (Channel, error) {
// TODO(dfc) s.lock protects s.channels but isn't being held here.
for _, c := range s.channels {
c.dead = true
c.setDead()
c.handleData(nil)
}
ssh/session_test.go
+1 -9
View File
@@ -47,7 +47,7 @@ func dial(handler serverType, t *testing.T) *ClientConn {
done := make(chan struct{})
for {
ch, err := conn.Accept()
if err == io.EOF {
if err == io.EOF || err == io.ErrUnexpectedEOF {
return
}
// We sometimes get ECONNRESET rather than EOF.
@@ -389,10 +389,6 @@ func TestServerStdoutRespectsMaxPacketSize(t *testing.T) {
}
func TestClientCannotSendAfterEOF(t *testing.T) {
// TODO(dfc) currently writes succeed after Close()
t.Logf("test skipped")
return
conn := dial(exitWithoutSignalOrStatus, t)
defer conn.Close()
session, err := conn.NewSession()
@@ -628,10 +624,6 @@ func discardHandler(ch *serverChan, t *testing.T) {
// grow the window to avoid being fooled by
// the initial 1 << 14 window.
ch.sendWindowAdj(1024 * 1024)
// TODO(dfc) io.Copy can return a non EOF error here
// because closed channel errors can leak here if the
// read from ch causes a window adjustment after the
// remote has signaled close.
io.Copy(ioutil.Discard, ch)
}
ssh/transport.go
-6
View File
@@ -194,12 +194,6 @@ func (w *writer) writePacket(packet []byte) error {
return w.Flush()
}
// Send a message to the remote peer
func (t *transport) sendMessage(typ uint8, msg interface{}) error {
packet := marshal(typ, msg)
return t.writePacket(packet)
}
func newTransport(conn net.Conn, rand io.Reader) *transport {
return &transport{
reader: reader{