-
Notifications
You must be signed in to change notification settings - Fork 0
/
proxy.go
336 lines (308 loc) · 9.03 KB
/
proxy.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
/*
Copyright 2016 Gravitational, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package srv
import (
"bytes"
"encoding/json"
"fmt"
"io"
"net"
"strings"
"sync"
"github.com/gravitational/teleport/lib/defaults"
"github.com/gravitational/teleport/lib/reversetunnel"
"github.com/gravitational/teleport/lib/services"
"github.com/gravitational/teleport/lib/sshutils"
"github.com/gravitational/teleport/lib/utils"
log "github.com/Sirupsen/logrus"
"github.com/gravitational/trace"
"golang.org/x/crypto/ssh"
)
// proxySubsys implements an SSH subsystem for proxying listening sockets from
// remote hosts to a proxy client (AKA port mapping)
type proxySubsys struct {
srv *Server
host string
port string
namespace string
siteName string
closeC chan struct{}
error error
closeOnce sync.Once
}
// parseProxySubsys looks at the requested subsystem name and returns a fully configured
// proxy subsystem
//
// proxy subsystem name can take the following forms:
// "proxy:host:22" - standard SSH request to connect to host:22 on the 1st cluster
// "proxy:@clustername" - Teleport request to connect to an auth server for cluster with name 'clustername'
// "proxy:host:22@clustername" - Teleport request to connect to host:22 on cluster 'clustername'
// "proxy:host:22@namespace@clustername"
func parseProxySubsys(name string, srv *Server) (*proxySubsys, error) {
log.Debugf("parse_proxy_subsys(%s)", name)
var (
siteName string
host string
port string
paramError = trace.BadParameter("invalid format for proxy request: '%v', expected 'proxy:host:port@site'", name)
)
const prefix = "proxy:"
// get rid of 'proxy:' prefix:
if strings.Index(name, prefix) != 0 {
return nil, trace.Wrap(paramError)
}
name = strings.TrimPrefix(name, prefix)
namespace := defaults.Namespace
// find the site name in the argument:
parts := strings.Split(name, "@")
switch len(parts) {
case 2:
siteName = strings.Join(parts[1:], "@")
name = parts[0]
case 3:
siteName = strings.Join(parts[2:], "@")
namespace = parts[1]
name = parts[0]
}
// find host & port in the arguments:
host, port, err := net.SplitHostPort(name)
if siteName == "" && err != nil {
return nil, trace.Wrap(paramError)
}
// validate siteName
if siteName != "" && srv.proxyTun != nil {
_, err := srv.proxyTun.GetSite(siteName)
if err != nil {
return nil, trace.BadParameter("unknown site '%s'", siteName)
}
}
return &proxySubsys{
namespace: namespace,
srv: srv,
host: host,
port: port,
siteName: siteName,
closeC: make(chan struct{}),
}, nil
}
func (t *proxySubsys) String() string {
return fmt.Sprintf("proxySubsys(site=%s/%s, host=%s, port=%s)",
t.namespace, t.siteName, t.host, t.port)
}
// start is called by Golang's ssh when it needs to engage this sybsystem (typically to establish
// a mapping connection between a client & remote node we're proxying to)
func (t *proxySubsys) start(sconn *ssh.ServerConn, ch ssh.Channel, req *ssh.Request, ctx *ctx) error {
log.Debugf("[PROXY] subsystem(from: %v, to: %v)", sconn.RemoteAddr(), sconn.LocalAddr())
var (
site reversetunnel.RemoteSite
err error
tunnel = t.srv.proxyTun
clientAddr = sconn.RemoteAddr()
)
// get the site by name:
if t.siteName != "" {
site, err = tunnel.GetSite(t.siteName)
if err != nil {
log.Warn(err)
return trace.Wrap(err)
}
}
// connecting to a specific host:
if t.host != "" {
// no site given? use the 1st one:
if site == nil {
sites := tunnel.GetSites()
if len(sites) == 0 {
log.Errorf("[PROXY] not connected to any remote clusters")
return trace.Errorf("no connected sites")
}
site = sites[0]
log.Debugf("[PROXY] subsystem: cluster not specified. connecting to default='%s'", site.GetName())
}
return t.proxyToHost(site, clientAddr, ch)
}
// connect to a site's auth server:
return t.proxyToSite(site, clientAddr, ch)
}
// proxyToSite establishes a proxy connection from the connected SSH client to the
// auth server of the requested remote site
func (t *proxySubsys) proxyToSite(
site reversetunnel.RemoteSite, remoteAddr net.Addr, ch ssh.Channel) error {
var (
err error
conn net.Conn
)
siteClient, err := site.GetClient()
if err != nil {
return trace.Wrap(err)
}
authServers, err := siteClient.GetAuthServers()
if err != nil {
return trace.Wrap(err)
}
for _, authServer := range authServers {
conn, err = site.Dial(remoteAddr,
&utils.NetAddr{Addr: authServer.GetAddr(), AddrNetwork: "tcp"})
if err != nil {
log.Error(err)
continue
}
log.Infof("[PROXY] connected to auth server: %v", authServer.GetAddr())
go func() {
var err error
defer func() {
t.close(err)
}()
defer ch.Close()
_, err = io.Copy(ch, conn)
}()
go func() {
var err error
defer func() {
t.close(err)
}()
defer conn.Close()
_, err = io.Copy(conn, ch)
}()
return nil
}
return err
}
// proxyToHost establishes a proxy connection from the connected SSH client to the
// requested remote node (t.host:t.port) via the given site
func (t *proxySubsys) proxyToHost(
site reversetunnel.RemoteSite, remoteAddr net.Addr, ch ssh.Channel) error {
//
// first, lets fetch a list of servers at the given site. this allows us to
// match the given "host name" against node configuration (their 'nodename' setting)
//
// but failing to fetch the list of servers is also OK, we'll use standard
// network resolution (by IP or DNS)
//
var (
servers []services.Server
err error
)
localDomain, _ := t.srv.authService.GetDomainName()
// going to "local" CA? lets use the caching 'auth service' directly and avoid
// hitting the reverse tunnel link (it can be offline if the CA is down)
if site.GetName() == localDomain {
servers, err = t.srv.authService.GetNodes(t.namespace)
if err != nil {
log.Warn(err)
}
} else {
// "remote" CA? use a reverse tunnel to talk to it:
siteClient, err := site.GetClient()
if err != nil {
log.Warn(err)
} else {
servers, err = siteClient.GetNodes(t.namespace)
if err != nil {
log.Warn(err)
}
}
}
// enumerate and try to find a server with a matching name
serverAddr := net.JoinHostPort(t.host, t.port)
var server services.Server
for i := range servers {
ip, port, err := net.SplitHostPort(servers[i].GetAddr())
if err != nil {
return trace.Wrap(err)
}
// match either by hostname of ip, based on the match
if (t.host == ip || t.host == servers[i].GetHostname()) && port == t.port {
server = servers[i]
break
}
}
if server != nil {
serverAddr = server.GetAddr()
}
// we must dial by server IP address because hostname
// may not be actually DNS resolvable
conn, err := site.Dial(
remoteAddr,
&utils.NetAddr{Addr: serverAddr, AddrNetwork: "tcp"})
if err != nil {
return trace.ConvertSystemError(err)
}
// this custom SSH handshake allows SSH proxy to relay the client's IP
// address to the SSH erver:
doHandshake(remoteAddr, ch, conn)
go func() {
var err error
defer func() {
t.close(err)
}()
defer ch.Close()
_, err = io.Copy(ch, conn)
}()
go func() {
var err error
defer func() {
t.close(err)
}()
defer conn.Close()
_, err = io.Copy(conn, ch)
}()
return nil
}
func (t *proxySubsys) close(err error) {
t.closeOnce.Do(func() {
t.error = err
close(t.closeC)
})
}
func (t *proxySubsys) wait() error {
<-t.closeC
return t.error
}
// doHandshake allows a proxy server to send additional information (client IP)
// to an SSH server before establishing a bridge
func doHandshake(clientAddr net.Addr, clientConn io.ReadWriter, serverConn io.ReadWriter) {
// on behalf of a client ask the server for it's version:
buff := make([]byte, sshutils.MaxVersionStringBytes)
n, err := serverConn.Read(buff)
if err != nil {
log.Error(err)
return
}
// chop off extra unused bytes at the end of the buffer:
buff = buff[:n]
// is that a Teleport server?
if bytes.HasPrefix(buff, []byte(sshutils.SSHVersionPrefix)) {
// if we're connecting to a Teleport SSH server, send our own "handshake payload"
// message, along with a client's IP:
hp := &sshutils.HandshakePayload{
ClientAddr: clientAddr.String(),
}
payloadJSON, err := json.Marshal(hp)
if err != nil {
log.Error(err)
} else {
// send a JSON payload sandwitched between 'teleport proxy signature' and 0x00:
payload := fmt.Sprintf("%s%s\x00", sshutils.ProxyHelloSignature, payloadJSON)
n, err = serverConn.Write([]byte(payload))
if err != nil {
log.Error(err)
}
}
}
// forwrd server's response to the client:
_, err = clientConn.Write(buff)
if err != nil {
log.Error(err)
}
}