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
|
package remote
import (
"context"
"fmt"
"io"
"strconv"
"strings"
"time"
"github.com/mimecast/dtail/internal/clients/handlers"
"github.com/mimecast/dtail/internal/config"
"github.com/mimecast/dtail/internal/io/logger"
"github.com/mimecast/dtail/internal/ssh/client"
"golang.org/x/crypto/ssh"
)
// Connection represents a client connection connection to a single server.
type Connection struct {
// The remote server's hostname connected to.
Server string
// The remote server's port connected to.
port int
// The SSH client configuration used.
config *ssh.ClientConfig
// The SSH client handler to use.
Handler handlers.Handler
// DTail commands sent from client to server. When client loses
// connection to the server it re-connects automatically and sends the
// same commands again.
Commands []string
// Is it a persistent connection or a one-off?
isOneOff bool
// To deal with SSH server host keys
hostKeyCallback client.HostKeyCallback
// To determine if connection throttling has finished or not
throttlingDone bool
}
// NewConnection returns a new connection.
func NewConnection(server string, userName string, authMethods []ssh.AuthMethod, hostKeyCallback client.HostKeyCallback) *Connection {
logger.Debug(server, "Creating new connection")
c := Connection{
hostKeyCallback: hostKeyCallback,
config: &ssh.ClientConfig{
User: userName,
Auth: authMethods,
HostKeyCallback: hostKeyCallback.Wrap(),
Timeout: time.Second * 3,
},
}
c.initServerPort(server)
return &c
}
// NewOneOffConnection creates new one-off connection (only for sending a series of commands and then quit).
func NewOneOffConnection(server string, userName string, authMethods []ssh.AuthMethod) *Connection {
c := Connection{
config: &ssh.ClientConfig{
User: userName,
Auth: authMethods,
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
},
isOneOff: true,
}
c.initServerPort(server)
return &c
}
// Attempt to parse the server port address from the provided server FQDN.
func (c *Connection) initServerPort(server string) {
c.Server = server
c.port = config.Common.SSHPort
parts := strings.Split(server, ":")
if len(parts) == 2 {
logger.Debug("Parsing port from hostname", parts)
port, err := strconv.Atoi(parts[1])
if err != nil {
logger.FatalExit("Unable to parse client port", server, parts, err)
}
c.Server = parts[0]
c.port = port
}
}
// Start the server connection. Build up SSH session and send some DTail commands.
func (c *Connection) Start(ctx context.Context, cancel context.CancelFunc, throttleCh, statsCh chan struct{}) {
// Throttle how many connections can be established concurrently (based on ch length)
logger.Debug(c.Server, "Throttling connection", len(throttleCh), cap(throttleCh))
select {
case throttleCh <- struct{}{}:
case <-ctx.Done():
logger.Debug(c.Server, "Not establishing connection as context is done", len(throttleCh), cap(throttleCh))
return
}
logger.Debug(c.Server, "Throttling says that the connection can be established", len(throttleCh), cap(throttleCh))
go func() {
defer func() {
if !c.throttlingDone {
logger.Debug(c.Server, "Unthrottling connection (1)", len(throttleCh), cap(throttleCh))
c.throttlingDone = true
<-throttleCh
}
cancel()
}()
if err := c.dial(ctx, cancel, throttleCh, statsCh); err != nil {
logger.Warn(c.Server, c.port, err)
if c.hostKeyCallback.Untrusted(fmt.Sprintf("%s:%d", c.Server, c.port)) {
logger.Debug(c.Server, "Not trusting host")
}
}
}()
<-ctx.Done()
}
// Dail into a new SSH connection. Close connection in case of an error.
func (c *Connection) dial(ctx context.Context, cancel context.CancelFunc, throttleCh, statsCh chan struct{}) error {
logger.Debug(c.Server, "Incrementing connection stats")
statsCh <- struct{}{}
defer func() {
logger.Debug(c.Server, "Decrementing connection stats")
<-statsCh
}()
logger.Debug(c.Server, "Dialing into the connection")
address := fmt.Sprintf("%s:%d", c.Server, c.port)
client, err := ssh.Dial("tcp", address, c.config)
if err != nil {
return err
}
defer client.Close()
return c.session(ctx, cancel, client, throttleCh)
}
// Create the SSH session. Close the session in case of an error.
func (c *Connection) session(ctx context.Context, cancel context.CancelFunc, client *ssh.Client, throttleCh chan struct{}) error {
logger.Debug(c.Server, "session")
session, err := client.NewSession()
if err != nil {
return err
}
defer session.Close()
return c.handle(ctx, cancel, session, throttleCh)
}
func (c *Connection) handle(ctx context.Context, cancel context.CancelFunc, session *ssh.Session, throttleCh chan struct{}) error {
logger.Debug(c.Server, "handle")
stdinPipe, err := session.StdinPipe()
if err != nil {
return err
}
stdoutPipe, err := session.StdoutPipe()
if err != nil {
return err
}
if err := session.Shell(); err != nil {
return err
}
go func() {
io.Copy(stdinPipe, c.Handler)
cancel()
}()
go func() {
io.Copy(c.Handler, stdoutPipe)
cancel()
}()
go func() {
select {
case <-c.Handler.Done():
case <-ctx.Done():
}
cancel()
}()
// Send all commands to client.
for _, command := range c.Commands {
logger.Debug(command)
c.Handler.SendMessage(command)
}
if !c.throttlingDone {
logger.Debug(c.Server, "Unthrottling connection (2)", len(throttleCh), cap(throttleCh))
c.throttlingDone = true
<-throttleCh
}
<-ctx.Done()
c.Handler.Shutdown()
return nil
}
|
