aboutsummaryrefslogtreecommitdiffstats
path: root/lib/ssh/doc/src/using_ssh.xml
blob: 5873e03f232033f62cd187938fe8aa78e4711539 (plain) (blame)
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
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">

<chapter>
  <header>
    <copyright>
      <year>2012</year>
      <year>2013</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.

      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.

    </legalnotice>

    <title>Getting Started</title>
    <prepared></prepared>
    <docno></docno>
    <approved></approved>
    <date></date>
    <rev></rev>
    <file>using_ssh.xml</file>
  </header>

  <section>
    <title>General Information</title>
    <p>The following examples use the utility function
    <seealso marker="ssh#start-0"> ssh:start/0</seealso> to start
    all needed applications (<c>crypto</c>, <c>public_key</c>, and <c>ssh</c>).
    All examples are run in an Erlang shell, or in a bash shell, using <em>openssh</em>
    to illustrate how the <c>ssh</c> application can be used. The
    examples are run as the user <c>otptest</c> on a local network where the
    user is authorized to log in over <c>ssh</c> to the host <em>tarlop</em>.
    </p>
    <p>If nothing else is stated, it is presumed that the <c>otptest</c> user
    has an entry in the <em>authorized_keys</em> file of <em>tarlop</em>
    (allowed to log in over <c>ssh</c> without entering a password).
    Also, <em>tarlop</em> is a known host in the <c>known_hosts</c>
    file of the user <c>otptest</c>. This means that host-verification
    can be done without user-interaction.
    </p>
  </section>

  <section>
    <title>Using the Erlang ssh Terminal Client</title>

    <p>The user <c>otptest</c>, which has bash as default shell, uses the
    <c>ssh:shell/1</c> client to connect to the <em>openssh</em> daemon running on a
    host called <em>tarlop</em>:</p>

    <code type="erl" >
      1>  ssh:start().
      ok
      2> {ok, S} = ssh:shell("tarlop").
      >pwd
      /home/otptest
      >exit
      logout
      3>
    </code>
    <p>Notice that this is a simple client that is not expected to be as
    fancy as the <em>openssh</em> client.</p>
  </section>

  <section>
    <marker id="Running an Erlang ssh Daemon"></marker>
    <title>Running an Erlang ssh Daemon</title>

    <p>The <c>system_dir</c> option must be a directory containing a host
    key file and it defaults to <c>/etc/ssh</c>. For details, see Section
    Configuration Files in <seealso
    marker="SSH_app">ssh(6)</seealso>.
    </p>

    <note><p>Normally, the <c>/etc/ssh</c> directory is only readable by root.</p>
    </note>

    <p>The option <c>user_dir</c> defaults to directory <c>users ~/.ssh</c>.</p>

    <p><em>Step 1.</em> To run the example without root privileges,
    generate new keys and host keys:</p>

    <code>
      $bash> ssh-keygen -t rsa -f /tmp/ssh_daemon/ssh_host_rsa_key
      [...]
      $bash> ssh-keygen -t rsa -f /tmp/otptest_user/.ssh/id_rsa
      [...]
    </code>

    <p><em>Step 2.</em> Create the file <c>/tmp/otptest_user/.ssh/authorized_keys</c>
    and add the content of <c>/tmp/otptest_user/.ssh/id_rsa.pub</c>.</p>

    <p><em>Step 3.</em> Start the Erlang <c>ssh</c> daemon:</p>

    <code type="erl">
      1> ssh:start().
      ok
      2> {ok, Sshd} = ssh:daemon(8989,  [{system_dir, "/tmp/ssh_daemon"},
      {user_dir, "/tmp/otptest_user/.ssh"}]).
      {ok,&lt;0.54.0>}
      3>
    </code>

    <p><em>Step 4.</em> Use the <em>openssh</em> client from a shell to connect
    to the Erlang <c>ssh</c> daemon:</p>

    <code>
      $bash> ssh tarlop -p 8989  -i /tmp/otptest_user/.ssh/id_rsa\
             -o UserKnownHostsFile=/tmp/otptest_user/.ssh/known_hosts
      The authenticity of host 'tarlop' can't be established.
      RSA key fingerprint is 14:81:80:50:b1:1f:57:dd:93:a8:2d:2f:dd:90:ae:a8.
      Are you sure you want to continue connecting (yes/no)? yes
      Warning: Permanently added 'tarlop' (RSA) to the list of known hosts.
      Eshell V5.10  (abort with ^G)
      1>
    </code>

    <p>There are two ways of shutting down an <c>ssh</c> daemon,
    see <em>Step 5a</em> and <em>Step 5b</em>.</p>

    <p><em>Step 5a.</em> Shut down the Erlang <c>ssh</c> daemon so that it
    stops the listener but leaves existing connections, started by the listener,
    operational:</p>

    <code type="erl">
      3> ssh:stop_listener(Sshd).
      ok
      4>
    </code>

    <p><em>Step 5b.</em> Shut down the Erlang <c>ssh</c> daemon so that it
    stops the listener and all connections started by the listener:</p>

    <code type="erl">
      3> ssh:stop_daemon(Sshd)
      ok
      4>
    </code>

  </section>

  <section>
    <title>One-Time Execution</title>

    <p>In the following example, the Erlang shell is the client process
    that receives the channel replies.</p>

    <note><p>The number of received messages in this example depends on which OS
    and which shell that is used on the machine running the <c>ssh</c> daemon.
    See also <seealso marker="ssh_connection#exec-4">ssh_connection:exec/4</seealso>
    </p>.</note>

    <p>Do a one-time execution of a remote command over <c>ssh</c>:</p>

    <code type="erl" >
      1>  ssh:start().
      ok
      2> {ok, ConnectionRef} = ssh:connect("tarlop", 22, []).
      {ok,&lt;0.57.0>}
      3>{ok, ChannelId} =  ssh_connection:session_channel(ConnectionRef, infinity).
      {ok,0}
      4> success = ssh_connection:exec(ConnectionRef, ChannelId, "pwd", infinity).
      5>  flush().
      Shell got {ssh_cm,&lt;0.57.0>,{data,0,0,&lt;&lt;"/home/otptest\n">>}}
      Shell got {ssh_cm,&lt;0.57.0>,{eof,0}}
      Shell got {ssh_cm,&lt;0.57.0>,{exit_status,0,0}}
      Shell got {ssh_cm,&lt;0.57.0>,{closed,0}}
      ok
      6>
    </code>

    <p>Notice that only the channel is closed. The connection is still up and can
    handle other channels:</p>

    <code type="erl" >
      6> {ok, NewChannelId} =  ssh_connection:session_channel(ConnectionRef, infinity).
        {ok,1}
	...
    </code>
  </section>

  <section>
    <title>SFTP Server</title>

    <p>Start the Erlang <c>ssh</c> daemon with the SFTP subsystem:</p>

    <code type="erl" >
      1> ssh:start().
      ok
      2> ssh:daemon(8989,  [{system_dir, "/tmp/ssh_daemon"},
         {user_dir, "/tmp/otptest_user/.ssh"},
         {subsystems, [ssh_sftpd:subsystem_spec([{cwd, "/tmp/sftp/example"}])]}]).
      {ok,&lt;0.54.0>}
      3>
    </code>

    <p>Run the OpenSSH SFTP client:</p>

    <code type="erl">
      $bash> sftp -oPort=8989 -o IdentityFile=/tmp/otptest_user/.ssh/id_rsa\
             -o UserKnownHostsFile=/tmp/otptest_user/.ssh/known_hosts tarlop
      Connecting to tarlop...
      sftp> pwd
      Remote working directory: /tmp/sftp/example
      sftp>
    </code>
  </section>

  <section>
    <title>SFTP Client</title>

    <p>Fetch a file with the Erlang SFTP client:</p>

    <code type="erl" >
      1> ssh:start().
      ok
      2> {ok, ChannelPid, Connection} = ssh_sftp:start_channel("tarlop", []).
      {ok,&lt;0.57.0>,&lt;0.51.0>}
      3>  ssh_sftp:read_file(ChannelPid, "/home/otptest/test.txt").
      {ok,&lt;&lt;"This is a test file\n">>}
    </code>
  </section>

  <section>
    <title>Creating a Subsystem</title>

    <p>A small <c>ssh</c> subsystem that echoes N bytes can be implemented as shown
    in the following example:</p>

    <code type="erl" >
-module(ssh_echo_server).
-behaviour(ssh_subsystem).
-record(state, {
	  n,
	  id,
	  cm
	 }).
-export([init/1, handle_msg/2, handle_ssh_msg/2, terminate/2]).

init([N]) ->
    {ok, #state{n = N}}.

handle_msg({ssh_channel_up, ChannelId, ConnectionManager}, State) ->
    {ok, State#state{id = ChannelId,
		     cm = ConnectionManager}}.

handle_ssh_msg({ssh_cm, CM, {data, ChannelId, 0, Data}}, #state{n = N} = State) ->
    M = N - size(Data),
    case M > 0 of
	true ->
	   ssh_connection:send(CM, ChannelId, Data),
	   {ok, State#state{n = M}};
	false ->
	   &lt;&lt;SendData:N/binary, _/binary>> = Data,
           ssh_connection:send(CM, ChannelId, SendData),
           ssh_connection:send_eof(CM, ChannelId),
	   {stop, ChannelId, State}
    end;
handle_ssh_msg({ssh_cm, _ConnectionManager,
		{data, _ChannelId, 1, Data}}, State) ->
    error_logger:format(standard_error, " ~p~n", [binary_to_list(Data)]),
    {ok, State};

handle_ssh_msg({ssh_cm, _ConnectionManager, {eof, _ChannelId}}, State) ->
    {ok, State};

handle_ssh_msg({ssh_cm, _, {signal, _, _}}, State) ->
    %% Ignore signals according to RFC 4254 section 6.9.
    {ok, State};

handle_ssh_msg({ssh_cm, _, {exit_signal, ChannelId, _, _Error, _}},
	       State) ->
    {stop, ChannelId,  State};

handle_ssh_msg({ssh_cm, _, {exit_status, ChannelId, _Status}}, State) ->
    {stop, ChannelId, State}.

terminate(_Reason, _State) ->
    ok.
 </code>

 <p>The subsystem can be run on the host <em>tarlop</em> with the generated keys,
 as described in Section <seealso marker="#Running an Erlang ssh Daemon">
 Running an Erlang ssh Daemon</seealso>:</p>

 <code type="erl" >
   1> ssh:start().
   ok
   2>  ssh:daemon(8989, [{system_dir, "/tmp/ssh_daemon"},
   {user_dir, "/tmp/otptest_user/.ssh"}
   {subsystems, [{"echo_n", {ssh_echo_server, [10]}}]}]).
   {ok,&lt;0.54.0>}
   3>
 </code>

 <code type="erl" >
   1> ssh:start().
   ok
   2>{ok, ConnectionRef} = ssh:connect("tarlop", 8989, [{user_dir, "/tmp/otptest_user/.ssh"}]).
    {ok,&lt;0.57.0>}
   3>{ok, ChannelId} = ssh_connection:session_channel(ConnectionRef, infinity).
   4> success = ssh_connection:subsystem(ConnectionRef, ChannelId, "echo_n", infinity).
   5> ok = ssh_connection:send(ConnectionRef, ChannelId, "0123456789", infinity).
   6> flush().
   {ssh_msg, &lt;0.57.0>, {data, 0, 1, "0123456789"}}
   {ssh_msg, &lt;0.57.0>, {eof, 0}}
   {ssh_msg, &lt;0.57.0>, {closed, 0}}
   7> {error, closed} = ssh_connection:send(ConnectionRef, ChannelId, "10", infinity).
 </code>
<p>See also <seealso marker="ssh_channel"> ssh_channel(3)</seealso>.</p>

</section>

</chapter>