exp/ssh: fix three shift bugs related to packet lengths

Thanks for Ke Lan for the initial report and investigation.

R=agl, gustav.paul, tg8866, rsc
CC=golang-dev
https://golang.org/cl/5443044

src/pkg/exp/ssh/channel.go

@@ -244,13 +244,13 @@ func (c *channel) Write(data []byte) (n int, err error) {
 
 		packet := make([]byte, 1+4+4+len(todo))
 		packet[0] = msgChannelData
-		packet[1] = byte(c.theirId) >> 24
-		packet[2] = byte(c.theirId) >> 16
-		packet[3] = byte(c.theirId) >> 8
+		packet[1] = byte(c.theirId >> 24)
+		packet[2] = byte(c.theirId >> 16)
+		packet[3] = byte(c.theirId >> 8)
 		packet[4] = byte(c.theirId)
-		packet[5] = byte(len(todo)) >> 24
-		packet[6] = byte(len(todo)) >> 16
-		packet[7] = byte(len(todo)) >> 8
+		packet[5] = byte(len(todo) >> 24)
+		packet[6] = byte(len(todo) >> 16)
+		packet[7] = byte(len(todo) >> 8)
 		packet[8] = byte(len(todo))
 		copy(packet[9:], todo)
 

src/pkg/exp/ssh/client.go

@@ -403,8 +403,8 @@ func (w *chanWriter) Write(data []byte) (n int, err error) {
 		n = len(data)
 		packet := make([]byte, 0, 9+n)
 		packet = append(packet, msgChannelData,
-			byte(w.peersId)>>24, byte(w.peersId)>>16, byte(w.peersId)>>8, byte(w.peersId),
-			byte(n)>>24, byte(n)>>16, byte(n)>>8, byte(n))
+			byte(w.peersId>>24), byte(w.peersId>>16), byte(w.peersId>>8), byte(w.peersId),
+			byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
 		err = w.writePacket(append(packet, data...))
 		w.rwin -= n
 		return