tempfork: temporarily fork gliderlabs/ssh and x/crypto/ssh

While we rearrange/upstream things.

gliderlabs/ssh is forked into tempfork from our prior fork
at be8b7add40

x/crypto/ssh OTOH is forked at
https://github.com/tailscale/golang-x-crypto because it was gnarlier
to vendor with various internal packages, etc.
Its git history shows where it starts (2c7772ba30643b7a2026cbea938420dce7c6384d).

Updates #3802

Change-Id: I546e5cdf831cfc030a6c42557c0ad2c58766c65f
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tempfork/gliderlabs/ssh/tcpip_test.go

@@ -0,0 +1,86 @@
+//go:build glidertests
+// +build glidertests
+
+package ssh
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net"
+	"strconv"
+	"strings"
+	"testing"
+
+	gossh "github.com/tailscale/golang-x-crypto/ssh"
+)
+
+var sampleServerResponse = []byte("Hello world")
+
+func sampleSocketServer() net.Listener {
+	l := newLocalListener()
+
+	go func() {
+		conn, err := l.Accept()
+		if err != nil {
+			return
+		}
+		conn.Write(sampleServerResponse)
+		conn.Close()
+	}()
+
+	return l
+}
+
+func newTestSessionWithForwarding(t *testing.T, forwardingEnabled bool) (net.Listener, *gossh.Client, func()) {
+	l := sampleSocketServer()
+
+	_, client, cleanup := newTestSession(t, &Server{
+		Handler: func(s Session) {},
+		LocalPortForwardingCallback: func(ctx Context, destinationHost string, destinationPort uint32) bool {
+			addr := net.JoinHostPort(destinationHost, strconv.FormatInt(int64(destinationPort), 10))
+			if addr != l.Addr().String() {
+				panic("unexpected destinationHost: " + addr)
+			}
+			return forwardingEnabled
+		},
+	}, nil)
+
+	return l, client, func() {
+		cleanup()
+		l.Close()
+	}
+}
+
+func TestLocalPortForwardingWorks(t *testing.T) {
+	t.Parallel()
+
+	l, client, cleanup := newTestSessionWithForwarding(t, true)
+	defer cleanup()
+
+	conn, err := client.Dial("tcp", l.Addr().String())
+	if err != nil {
+		t.Fatalf("Error connecting to %v: %v", l.Addr().String(), err)
+	}
+	result, err := ioutil.ReadAll(conn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(result, sampleServerResponse) {
+		t.Fatalf("result = %#v; want %#v", result, sampleServerResponse)
+	}
+}
+
+func TestLocalPortForwardingRespectsCallback(t *testing.T) {
+	t.Parallel()
+
+	l, client, cleanup := newTestSessionWithForwarding(t, false)
+	defer cleanup()
+
+	_, err := client.Dial("tcp", l.Addr().String())
+	if err == nil {
+		t.Fatalf("Expected error connecting to %v but it succeeded", l.Addr().String())
+	}
+	if !strings.Contains(err.Error(), "port forwarding is disabled") {
+		t.Fatalf("Expected permission error but got %#v", err)
+	}
+}