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cef3726d 1<?xml version="1.0" encoding="us-ascii"?>\r
2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"\r
3 "http://www.w3.org/TR/xhtml1/DTD/strict.dtd">\r
4<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\r
5 <head>\r
6 <title>SSH Proxy Command -- connect.c</title>\r
7 <meta name="generator" content="emacs-wiki.el" />\r
8 <meta http-equiv="Content-Type"\r
9 content="us-ascii" />\r
10 <link rev="made" href="mailto:gotoh@imasy.or.jp" />\r
11 <link rel="home" href="http://www.imasy.ne.jp/~gotoh/" />\r
12 <link rel="index" href="http://www.imasy.ne.jp/~gotoh/SiteIndex.html" />\r
13 <link rel="stylesheet" type="text/css" href="emacs-wiki.css">\r
14 </head>\r
15 <body>\r
16 <h1>SSH Proxy Command -- connect.c</h1>\r
17 <!-- Page published by Emacs Wiki begins here -->\r
18<p>\r
19<strong>connect.c</strong> is the simple relaying command to make network\r
20connection via SOCKS and https proxy. It is mainly intended to\r
21be used as <strong>proxy command</strong> of OpenSSH. You can make SSH session\r
22beyond the firewall with this command,\r
23\r
24</p>\r
25\r
26<p>\r
27Features of <strong>connect.c</strong> are:\r
28\r
29</p>\r
30\r
31<ul>\r
32<li>Supports SOCKS (version 4/4a/5) and https CONNECT method.\r
33</li>\r
34<li>Supports NO-AUTH and USERPASS authentication of SOCKS\r
35</li>\r
36<li>You can input password from tty, ssh-askpass or\r
37 environment variable.\r
38</li>\r
39<li>Run on UNIX or Windows platform.\r
40</li>\r
41<li>You can compile with various C compiler (cc, gcc, Visual C, Borland C. etc.)\r
42</li>\r
43<li>Simple and general program independent from OpenSSH.\r
44</li>\r
45<li>You can also relay local socket stream instead of standard I/O.\r
46</li>\r
47</ul>\r
48\r
49<p>\r
50Download source code from:\r
51<a href="http://www.imasy.or.jp/~gotoh/ssh/connect.c">http://www.imasy.or.jp/~gotoh/ssh/connect.c</a>\r
52<br/>\r
53For windows user, pre-compiled binary is also available:\r
54<a href="http://www.imasy.or.jp/~gotoh/ssh/connect.exe">http://www.imasy.or.jp/~gotoh/ssh/connect.exe</a> (compiled with MSVC)\r
55\r
56</p>\r
57\r
58<hr>\r
59<dl class="contents">\r
60<dt class="contents">\r
61<a href="connect.html#sec1">News</a>\r
62</dt>\r
63<dt class="contents">\r
64<a href="connect.html#sec2">What is 'proxy command'</a>\r
65</dt>\r
66<dt class="contents">\r
67<a href="connect.html#sec3">How to Use</a>\r
68</dt>\r
69<dd>\r
70<dl class="contents">\r
71<dt class="contents">\r
72<a href="connect.html#sec4">Get Source</a>\r
73</dt>\r
74<dt class="contents">\r
75<a href="connect.html#sec5">Compile and Install</a>\r
76</dt>\r
77<dt class="contents">\r
78<a href="connect.html#sec6">Modify your ~/.ssh/config</a>\r
79</dt>\r
80<dt class="contents">\r
81<a href="connect.html#sec7">Use SSH</a>\r
82</dt>\r
83<dt class="contents">\r
84<a href="connect.html#sec8">Have trouble?</a>\r
85</dt>\r
86</dl>\r
87</dd>\r
88<dt class="contents">\r
89<a href="connect.html#sec9">More Detail</a>\r
90</dt>\r
91<dt class="contents">\r
92<a href="connect.html#sec10">Limitations</a>\r
93</dt>\r
94<dd>\r
95<dl class="contents">\r
96<dt class="contents">\r
97<a href="connect.html#sec11">SOCKS5 authentication</a>\r
98</dt>\r
99<dt class="contents">\r
100<a href="connect.html#sec12">HTTP authentication</a>\r
101</dt>\r
102<dt class="contents">\r
103<a href="connect.html#sec13">Switching proxy server</a>\r
104</dt>\r
105</dl>\r
106</dd>\r
107<dt class="contents">\r
108<a href="connect.html#sec14">Tips</a>\r
109</dt>\r
110<dd>\r
111<dl class="contents">\r
112<dt class="contents">\r
113<a href="connect.html#sec15">Proxying socket connection</a>\r
114</dt>\r
115<dt class="contents">\r
116<a href="connect.html#sec16">Use with <code>ssh-askpass</code> command</a>\r
117</dt>\r
118<dt class="contents">\r
119<a href="connect.html#sec17">Use for Network Stream of Emacs</a>\r
120</dt>\r
121<dt class="contents">\r
122<a href="connect.html#sec18">Remote resolver</a>\r
123</dt>\r
124<dt class="contents">\r
125<a href="connect.html#sec19">Hopping Connection via SSH</a>\r
126</dt>\r
127</dl>\r
128</dd>\r
129<dt class="contents">\r
130<a href="connect.html#sec20">F.Y.I.</a>\r
131</dt>\r
132<dd>\r
133<dl class="contents">\r
134<dt class="contents">\r
135<a href="connect.html#sec21">Difference between SOCKS versions.</a>\r
136</dt>\r
137<dt class="contents">\r
138<a href="connect.html#sec22">Configuration to use HTTPS</a>\r
139</dt>\r
140<dt class="contents">\r
141<a href="connect.html#sec23">SOCKS5 Servers</a>\r
142</dt>\r
143<dt class="contents">\r
144<a href="connect.html#sec24">Specifications</a>\r
145</dt>\r
146<dt class="contents">\r
147<a href="connect.html#sec25">Related Links</a>\r
148</dt>\r
149<dt class="contents">\r
150<a href="connect.html#sec26">Similars</a>\r
151</dt>\r
152</dl>\r
153</dd>\r
154</dl>\r
155\r
156<h2><a name="sec1">News</a></h2>\r
157\r
158<dl>\r
159<dt>2003-01-07</dt>\r
160<dd>\r
161Rev. 1.68. Fixed a trouble around timeout support.\r
162</dd>\r
163<dt>2002-11-21</dt>\r
164<dd>\r
165Rev. 1.64 supports reading parameters from file /etc/connectrc or\r
166 ~/.connectrc instead of specifying via environment variables. For\r
167 examle, you can use this feature to switch setting by replacing file\r
168 when network environment is changed. And added SOCKS_DIRECT,\r
169 SOCKS5_DIRECT, SOCKS4_DIRECT, HTTP_DIRECT, SOCKS5_AUTH, environment\r
170 parameters. (Thanks Masatoshi TSUCHIYA)\r
171</dd>\r
172<dt>2002-11-20</dt>\r
173<dd>\r
174Rev. 1.63 supports some old proxies which make response 401 with\r
175 WWW-Authenticate: header. And fixed to use username specified in\r
176 proxy host by -H option correctly. (contributed from Des Herriott, thanks)\r
177</dd>\r
178<dt>2002-10-14</dt>\r
179<dd>\r
180Rev. 1.61 with New option -w for specifying connection timeout.\r
181 Currently, it works on UNIX only. (contributed from Darren Tucker, thanks)\r
182</dd>\r
183<dt>2002-09-29</dt>\r
184<dd>\r
185Add sample script for switching proxy server\r
186 advised from Darren Tucker, thanks.\r
187</dd>\r
188<dt>2002-08-27</dt>\r
189<dd>\r
190connect.c is updataed to rev. 1.60.\r
191</dd>\r
192<dt>2002-04-08</dt>\r
193<dd>\r
194Updated <a href="http://www.imasy.or.jp/~gotoh/ssh/openssh-socks.html">"Using OpenSSH through a SOCKS compatible PROXY on your LAN"</a> written by J. Grant. (version 0.8)\r
195</dd>\r
196<dt>2002-02-20</dt>\r
197<dd>\r
198Add link of new document "Using OpenSSH through a SOCKS compatible PROXY on your LAN"\r
199 written by J. Grant.\r
200</dd>\r
201<dt>2002-01-31</dt>\r
202<dd>\r
203Rev. 1.53 -- On Win32 and with MSVC, handle password\r
204 input from console correctly.\r
205</dd>\r
206<dt>2002-01-30</dt>\r
207<dd>\r
208Rev. 1.50 -- [Security Fix] Do not print secure info in debug mode.\r
209</dd>\r
210<dt>2002-01-09</dt>\r
211<dd>\r
212Web page was made.\r
213 connect.c is rev. 1.48.\r
214</dd>\r
215</dl>\r
216\r
217<h2><a name="sec2">What</a> is 'proxy command'</h2>\r
218\r
219<p>\r
220OpenSSH development team decides to stop supporting SOCKS and any\r
221other tunneling mechanism. It was aimed to separate complexity to\r
222support various mechanism of proxying from core code. And they\r
223recommends more flexible mechanism: '<strong>ProxyCommand</strong>' option\r
224instead.\r
225\r
226</p>\r
227\r
228<p>\r
229Proxy command mechanism is delegation of network stream\r
230communication. If '<strong>ProxyCommand</strong>' options is specified, SSH\r
231invoke specified external command and talk with standard I/O of thid\r
232command. Invoked command undertakes network communication with\r
233relaying to/from standard input/output including iniitial\r
234communication or negotiation for proxying. Thus, ssh can split out\r
235proxying code into external command.\r
236\r
237</p>\r
238\r
239<p>\r
240'<strong>connect.c</strong>' was made for this purpose.\r
241\r
242</p>\r
243\r
244<h2><a name="sec3">How</a> to Use</h2>\r
245\r
246<h3><a name="sec4">Get</a> Source</h3>\r
247\r
248<p>\r
249Download source code from <a href="http://www.imasy.or.jp/~gotoh/ssh/connect.c">here</a>.\r
250<br/>\r
251If you are MS Windows user, you can get pre-compiled binary from\r
252<a href="http://www.imasy.or.jp/~gotoh/ssh/connect.exe">here</a>.\r
253\r
254</p>\r
255\r
256<h3><a name="sec5">Compile</a> and Install</h3>\r
257\r
258<p>\r
259In most environment, you can compile '<strong>connect.c</strong>' simply.\r
260On UNIX environment, you can use cc or gcc.\r
261On Windows environment, you can use Microsoft Visual C, Borland C or Cygwin gcc.\r
262\r
263</p>\r
264\r
265<table border="2" cellpadding="5">\r
266<thead>\r
267<tr>\r
268<th>Compiler</th><th>command line to compile</th>\r
269</tr>\r
270</thead>\r
271<tbody>\r
272<tr>\r
273<td>UNIX cc</td><td>cc connect.c -o connect</td>\r
274</tr>\r
275<tr>\r
276<td>UNIX gcc</td><td>gcc connect.c -o connect</td>\r
277</tr>\r
278<tr>\r
279<td>Solaris</td><td>gcc connect.c -o connect -lnsl -lsocket -lresolv</td>\r
280</tr>\r
281<tr>\r
282<td>Microsoft Visual C/C++</td><td>cl connect.c wsock32.lib advapi32.lib</td>\r
283</tr>\r
284<tr>\r
285<td>Borland C</td><td>bcc32 connect.c wsock32.lib advapi32.lib</td>\r
286</tr>\r
287<tr>\r
288<td>Cygwin gcc</td><td>gcc connect.c -o connect</td>\r
289</tr>\r
290</tbody>\r
291</table>\r
292\r
293<p>\r
294To install '<strong>connect</strong>' command, simply copy compiled binary to directory\r
295in your PATH (ex. /usr/local/bin). Like this:\r
296\r
297</p>\r
298\r
299<pre class="example">\r
300$ cp connect /usr/local/bin\r
301</pre>\r
302\r
303<h3><a name="sec6">Modify</a> your ~/.ssh/config</h3>\r
304\r
305<p>\r
306Modify your <code>~/.ssh/config</code> file to use '<strong>connect</strong>' command as\r
307'<strong>proxy command</strong>'. For the case of SOCKS server is running on\r
308firewall host '<code>socks.local.net</code>' with port 1080, you can add\r
309'<strong>ProxyCommand</strong>' option in <code>~/.ssh/config</code>, like this:\r
310\r
311</p>\r
312\r
313<pre class="example">\r
314Host remote.outside.net\r
315 ProxyCommand connect -S socks.local.net %h %p\r
316</pre>\r
317\r
318<p>\r
319'<code>%h</code>' and '<code>%p</code>' will be replaced on invoking proxy command with\r
320target hostname and port specified to SSH command.\r
321\r
322</p>\r
323\r
324<p>\r
325If you hate writing many entries of remote hosts, following example\r
326may help you.\r
327\r
328</p>\r
329\r
330<pre class="example">\r
331## Outside of the firewall, use connect command with SOCKS conenction.\r
332Host *\r
333 ProxyCommand connect -S socks.local.net %h %p\r
334\r
335## Inside of the firewall, use connect command with direct connection.\r
336Host *.local.net\r
337 ProxyCommand connect %h %p\r
338</pre>\r
339\r
340<p>\r
341If you want to use http proxy, use '<strong>-H</strong>' option instead of '<strong>-S</strong>'\r
342option in examle above, like this:\r
343\r
344</p>\r
345\r
346<pre class="example">\r
347## Outside of the firewall, with HTTP proxy\r
348Host *\r
349 ProxyCommand connect -H proxy.local.net:8080 %h %p\r
350\r
351## Inside of the firewall, direct\r
352Host *.local.net\r
353 ProxyCommand connect %h %p\r
354</pre>\r
355\r
356<h3><a name="sec7">Use</a> SSH</h3>\r
357\r
358<p>\r
359After editing your <code>~/.ssh/config</code> file, you are ready to use ssh.\r
360You can execute ssh without any special options as if remote host is\r
361IP reachable host. Following is an example to execute '<code>hostname</code>'\r
362command on host '<code>remote.outside.net</code>'.\r
363\r
364</p>\r
365\r
366<pre class="example">\r
367$ ssh remote.outside.net hostname\r
368remote.outside.net\r
369$\r
370</pre>\r
371\r
372<h3><a name="sec8">Have</a> trouble?</h3>\r
373\r
374<p>\r
375If you have trouble, execute '<strong>connect</strong>' command from command line\r
376with '<code>-d</code>' option to see what is happened. Some debug message may\r
377appear and reports progress. This information may tell you what is\r
378wrong. In this example, error has occurred on authentication stage of\r
379SOCKS5 protocol.\r
380\r
381</p>\r
382\r
383<pre class="example">\r
384$ connect -d -S socks.local.net unknown.remote.outside.net 110\r
385DEBUG: relay_method = SOCKS (2)\r
386DEBUG: relay_host=socks.local.net\r
387DEBUG: relay_port=1080\r
388DEBUG: relay_user=gotoh\r
389DEBUG: socks_version=5\r
390DEBUG: socks_resolve=REMOTE (2)\r
391DEBUG: local_type=stdio\r
392DEBUG: dest_host=unknown.remote.outside.net\r
393DEBUG: dest_port=110\r
394DEBUG: Program is $Revision$\r
395DEBUG: connecting to xxx.xxx.xxx.xxx:1080\r
396DEBUG: begin_socks_relay()\r
397DEBUG: atomic_out() [4 bytes]\r
398DEBUG: >>> 05 02 00 02\r
399DEBUG: atomic_in() [2 bytes]\r
400DEBUG: <<< 05 02\r
401DEBUG: auth method: USERPASS\r
402DEBUG: atomic_out() [some bytes]\r
403DEBUG: >>> xx xx xx xx ...\r
404DEBUG: atomic_in() [2 bytes]\r
405DEBUG: <<< 01 01\r
406ERROR: Authentication faield.\r
407FATAL: failed to begin relaying via SOCKS.\r
408</pre>\r
409\r
410<h2><a name="sec9">More</a> Detail</h2>\r
411\r
412<p>\r
413Command line usage is here:\r
414\r
415</p>\r
416\r
417<pre class="example">\r
418usage: connect [-dnhs45] [-R resolve] [-p local-port] [-w sec]\r
419 [-H [user@]proxy-server[:port]]\r
420 [-S [user@]socks-server[:port]]\r
421 host port\r
422</pre>\r
423\r
424<p>\r
425'<strong>host</strong>' and '<strong>port</strong>' is target hostname and port-number to connect.\r
426\r
427</p>\r
428\r
429<p>\r
430'<strong>-H</strong>' option specify hostname and port number of http proxy server to\r
431relay. If port is omitted, 80 is used. You can specify this value by\r
432environment variable <code>HTTP_PROXY</code> and give '<strong>-h</strong>' option to use it.\r
433\r
434</p>\r
435\r
436<p>\r
437'<strong>-S</strong>' option specify hostname and port number of SOCKS server to\r
438relay. Like '<strong>-H</strong>' option, port number can be omit and default is 1080. \r
439You can also specify this value pair by environment variable\r
440<code>SOCKS5_SERVER</code> and give '<strong>-s</strong>' option to use it.\r
441\r
442</p>\r
443\r
444<p>\r
445'<strong>-4</strong>' and '<strong>-5</strong>' is for specifying SOCKS protocol version. It is\r
446valid only using with '<strong>-s</strong>' or '<strong>-S</strong>'. Default is '<strong>-5</strong>'\r
447(protocol version 5)\r
448\r
449</p>\r
450\r
451<p>\r
452'<strong>-R</strong>' is for specifying method to resolve hostname. 3 keywords\r
453('<code>local</code>', '<code>remote</code>', '<code>both</code>') or dot-notation IP address is\r
454allowed. Keyword '<code>both</code>' means; "Try local first, then\r
455remote". If dot-notation IP address is specified, use this host as\r
456nameserver (UNIX only). Default is '<code>remote</code>' for SOCKS5 or '<code>local</code>'\r
457for others. On SOCKS4 protocol, remote resolving method ('<code>remote</code>'\r
458and '<code>both</code>') use protocol version 4a.\r
459\r
460</p>\r
461\r
462<p>\r
463The '<strong>-p</strong>' option will forward a local TCP port instead of using the\r
464standard input and output.\r
465\r
466</p>\r
467\r
468<p>\r
469The '<strong>-w</strong>' option specifys timeout seconds for making connection with\r
470TARGET host.\r
471\r
472</p>\r
473\r
474<p>\r
475The '<strong>-a</strong>' option specifiys user intended authentication methods\r
476separated by comma. Currently '<code>userpass</code>' and '<code>none</code>' are\r
477supported. Default is '<code>userpass</code>'. You can also specifying this\r
478parameter by the environment variable <code>SOCKS5_AUTH</code>.\r
479\r
480</p>\r
481\r
482<p>\r
483The '<strong>-d</strong>' option is used for debug. If you fail to connect, use this\r
484and check request to and response from server.\r
485\r
486</p>\r
487\r
488<p>\r
489You can omit '<strong>port</strong>' argument when program name is special format\r
490containing port number itself. For example, \r
491\r
492</p>\r
493\r
494<pre class="example">\r
495$ ln -s connect connect-25\r
496$ ./connect-25 smtphost.outside.net\r
497220 smtphost.outside.net ESMTP Sendmail\r
498QUIT\r
499221 2.0.0 smtphost.remote.net closing connection\r
500$\r
501</pre>\r
502\r
503<p>\r
504This example means that the command name "<code>connect-25</code>" contains port number\r
50525 so you can omit 2nd argument (and used if specified explicitly).\r
506\r
507</p>\r
508\r
509<h2><a name="sec10">Limitations</a></h2>\r
510\r
511<h3><a name="sec11">SOCKS5</a> authentication</h3>\r
512\r
513<p>\r
514Only NO-AUTH and USER/PASSWORD authentications are supported.\r
515GSSAPI authentication (RFC 1961) and other draft authentications (CHAP,\r
516EAP, MAF, etc.) is not supported.\r
517\r
518</p>\r
519\r
520<h3><a name="sec12">HTTP</a> authentication</h3>\r
521\r
522<p>\r
523BASIC authentication is supported but DIGEST authentication is not.\r
524\r
525</p>\r
526\r
527<h3><a name="sec13">Switching</a> proxy server</h3>\r
528\r
529<p>\r
530There is no mechanism to switch proxy server regarding to PC environment.\r
531This limitation might be bad news for mobile user.\r
532Since I do not want to make this program complex, I do not want to\r
533support although this feature is already requested. Please advice me\r
534if there is good idea of detecting environment to swich and simple way\r
535to specify conditioned directive of servers.\r
536\r
537</p>\r
538\r
539<p>\r
540One tricky workaround exists. It is replacing ~/.ssh/config file\r
541by script on ppp up/down.\r
542\r
543</p>\r
544\r
545<p>\r
546There's another example of wrapper script (contributed by Darren Tucker).\r
547This script costs executing ifconfig and grep to detect\r
548current environment, but it works. (NOTE: you should modify addresses\r
549if you use it.)\r
550\r
551</p>\r
552\r
553<pre class="example">\r
554#!/bin/sh\r
555## ~/bin/myconnect --- Proxy server switching wrapper\r
556\r
557if ifconfig eth0 |grep "inet addr:192\.168\.1" >/dev/null; then\r
558 opts="-S 192.168.1.1:1080" \r
559elif ifconfig eth0 |grep "inet addr:10\." >/dev/null; then\r
560 opts="-H 10.1.1.1:80"\r
561else\r
562 opts="-s"\r
563fi\r
564exec /usr/local/bin/connect $opts $@\r
565</pre>\r
566\r
567<h2><a name="sec14">Tips</a></h2>\r
568\r
569<h3><a name="sec15">Proxying</a> socket connection</h3>\r
570\r
571<p>\r
572In usual, '<strong>connect.c</strong>' relays network connection to/from standard\r
573input/output. By specifying '<strong>-p</strong>' option, however, '<strong>connect.c</strong>'\r
574relays local network stream instead of standard input/output.\r
575With this option, '<strong>connect</strong>' command waits connection\r
576from other program, then start relaying between both network stream.\r
577\r
578</p>\r
579\r
580<p>\r
581This feature may be useful for the program which is hard to SOCKSify.\r
582\r
583</p>\r
584\r
585<h3><a name="sec16">Use</a> with <code>ssh-askpass</code> command</h3>\r
586\r
587<p>\r
588'<strong>connect.c</strong>' ask you password when authentication is required. If\r
589you are using on tty/pty terminal, connect can input from terminal\r
590with prompt. But you can also use '<code>ssh-askpass</code>' program to input\r
591password. If you are graphical environment like X Window or MS\r
592Windows, and program does not have tty/pty, and environment variable\r
593SSH_ASKPASS is specified, then '<strong>connect.c</strong>' invoke command\r
594specified by environment variable '<code>SSH_ASKPASS</code>' to input password.\r
595<code>ssh-askpass</code> program might be installed if you are using OpenSSH on\r
596UNIX environment. On Windows environment, pre-compiled binary is\r
597available from\r
598<a href="http://www.imasy.or.jp/~gotoh/ssh/ssh-askpass.exe">here</a>.\r
599\r
600</p>\r
601\r
602<p>\r
603This feature is limited on window system environment.\r
604\r
605</p>\r
606\r
607<p>\r
608And also useful on Emacs on MS Windows (NT Emacs or Meadow). It is\r
609hard to send passphrase to '<strong>connect</strong>' command (and also ssh)\r
610because external command is invoked on hidden terminal and do I/O with\r
611this terminal. Using ssh-askpass avoids this problem.\r
612\r
613</p>\r
614\r
615<h3><a name="sec17">Use</a> for Network Stream of Emacs</h3>\r
616\r
617<p>\r
618Although '<strong>connect.c</strong>' is made for OpenSSH, it is generic and\r
619independent from OpenSSH. So we can use this for other purpose. For\r
620example, you can use this command in Emacs to open network connection\r
621with remote host over the firewall via SOCKS or HTTP proxy without\r
622SOCKSifying Emacs itself.\r
623\r
624</p>\r
625\r
626<p>\r
627There is sample code: \r
628<a href="http://www.imasy.or.jp/~gotoh/lisp/relay.el">http://www.imasy.or.jp/~gotoh/lisp/relay.el</a>\r
629\r
630</p>\r
631\r
632<p>\r
633With this code, you can use <code>relay-open-network-stream</code> function\r
634instead of <code>open-network-stream</code> to make network connection. See top\r
635comments of source for more detail.\r
636\r
637</p>\r
638\r
639<h3><a name="sec18">Remote</a> resolver</h3>\r
640\r
641<p>\r
642If you are SOCKS4 user on UNIX environment, you might want specify\r
643nameserver to resolve remote hostname. You can do it specifying\r
644'<strong>-R</strong>' option followed by IP address of resolver.\r
645\r
646</p>\r
647\r
648<h3><a name="sec19">Hopping</a> Connection via SSH</h3>\r
649\r
650<p>\r
651Conbination of ssh and '<strong>connect</strong>' command have more interesting usage.\r
652Following command makes indirect connection to host2:port from your\r
653current host via host1.\r
654\r
655</p>\r
656\r
657<pre class="example">\r
658ssh host1 connect host2 port\r
659</pre>\r
660\r
661<p>\r
662This method is useful for the situations like:\r
663\r
664</p>\r
665\r
666<ul>\r
667<li>You are outside of organizasion now, but you want to access an\r
668 internal host barriered by firewall.\r
669</li>\r
670<li>You want to use some service which is allowed only from some\r
671 limited hosts.\r
672</li>\r
673</ul>\r
674\r
675<p>\r
676For example, I want to use local NetNews service in my office\r
677from home. I cannot make NNTP session directly because NNTP host is\r
678barriered by firewall. Fortunately, I have ssh account on internal\r
679host and allowed using SOCKS5 on firewall from outside. So I use\r
680following command to connect to NNTP service.\r
681\r
682</p>\r
683\r
684<pre class="example">\r
685$ ssh host1 connect news 119\r
686200 news.my-office.com InterNetNews NNRP server INN 2.3.2 ready (posting ok).\r
687quit\r
688205 .\r
689$\r
690</pre>\r
691\r
692<p>\r
693By combinating hopping connection and relay.el, I can read NetNews\r
694using <a href="http://www.gohome.org/wl/">Wanderlust</a> on Emacs at home.\r
695\r
696</p>\r
697\r
698<pre class="example">\r
699 |\r
700 External (internet) | Internal (office)\r
701 |\r
702+------+ +----------+ +-------+ +-----------+\r
703| HOME | | firewall | | host1 | | NNTP host |\r
704+------+ +----------+ +-------+ +-----------+\r
705 emacs <-------------- ssh ---------------> sshd <-- connect --> nntpd\r
706 <-- connect --> socksd <-- SOCKS -->\r
707</pre>\r
708\r
709<h2><a name="sec20">F</a>.Y.I.</h2>\r
710\r
711<h3><a name="sec21">Difference</a> between SOCKS versions.</h3>\r
712\r
713<p>\r
714SOCKS version 4 is first popular implementation which is documented\r
715<a href="http://www.socks.nec.com/protocol/socks4.protocol">here</a>. Since\r
716this protocol provide IP address based requesting, client program\r
717should resolve name of outer host by itself. Version 4a (documented\r
718<a href="http://www.socks.nec.com/protocol/socks4a.protocol">here</a>) is\r
719enhanced to allow request by hostname instead of IP address.\r
720\r
721</p>\r
722\r
723<p>\r
724SOCKS version 5 is re-designed protocol stands on experience of\r
725version 4 and 4a. There is no compativility with previous\r
726versions. Instead, there's some improvement: IPv6 support, request by\r
727hostname, UDP proxying, etc.\r
728\r
729</p>\r
730\r
731<h3><a name="sec22">Configuration</a> to use HTTPS</h3>\r
732\r
733<p>\r
734Many http proxy servers implementation supports https <code>CONNECT</code> method\r
735(SLL). You might add configuration to allow using https. For the\r
736example of <a href="http://www.delegate.org/delegate/">DeleGate</a> (\r
737DeleGate is a multi-purpose application level gateway, or a proxy\r
738server) , you should add '<code>https</code>' to '<code>REMITTABLE</code>' parameter to\r
739allow HTTP-Proxy like this:\r
740\r
741</p>\r
742\r
743<pre class="example">\r
744delegated -Pxxxx ...... REMITTABLE='+,https' ...\r
745</pre>\r
746\r
747<p>\r
748For the case of Squid, you should allow target ports via https by ACL,\r
749and so on.\r
750\r
751</p>\r
752\r
753<h3><a name="sec23">SOCKS5</a> Servers</h3>\r
754\r
755<dl>\r
756<dt><a href="http://www.socks.nec.com/refsoftware.html">NEC SOCKS Reference Implementation</a></dt>\r
757<dd>\r
758Reference implementation of SOKCS server and library.\r
759</dd>\r
760<dt><a href="http://www.inet.no/dante/index.html">Dante</a></dt>\r
761<dd>\r
762Dante is free implementation of SOKCS server and library.\r
763 Many enhancements and modulalized.\r
764</dd>\r
765<dt><a href="http://www.delegate.org/delegate/">DeleGate</a></dt>\r
766<dd>\r
767DeleGate is multi function proxy service provider.\r
768 DeleGate 5.x.x or earlier can be SOCKS4 server,\r
769 and 6.x.x can be SOCKS5 and SOCKS4 server.\r
770 and 7.7.0 or later can be SOCKS5 and SOCKS4a server.\r
771</dd>\r
772</dl>\r
773\r
774<h3><a name="sec24">Specifications</a></h3>\r
775\r
776<dl>\r
777<dt><a href="http://www.socks.nec.com/protocol/socks4.protocol">socks4.protocol.txt</a></dt>\r
778<dd>\r
779SOCKS: A protocol for TCP proxy across firewalls\r
780</dd>\r
781<dt><a href="http://www.socks.nec.com/protocol/socks4a.protocol">socks4a.protocol.txt</a></dt>\r
782<dd>\r
783SOCKS 4A: A Simple Extension to SOCKS 4 Protocol\r
784</dd>\r
785<dt><a href="http://www.socks.nec.com/rfc/rfc1928.txt">RFC 1928</a></dt>\r
786<dd>\r
787SOCKS Protocol Version 5\r
788</dd>\r
789<dt><a href="http://www.socks.nec.com/rfc/rfc1929.txt">RFC 1929</a></dt>\r
790<dd>\r
791Username/Password Authentication for SOCKS V5\r
792</dd>\r
793<dt><a href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</a></dt>\r
794<dd>\r
795Hypertext Transfer Protocol -- HTTP/1.1\r
796</dd>\r
797<dt><a href="http://www.ietf.org/rfc/rfc2617.txt">RFC 2617</a></dt>\r
798<dd>\r
799HTTP Authentication: Basic and Digest Access Authentication\r
800</dd>\r
801</dl>\r
802\r
803<h3><a name="sec25">Related</a> Links</h3>\r
804\r
805<ul>\r
806<li><a href="http://www.openssh.org">OpenSSH Home</a>\r
807</li>\r
808<li><a href="http://www.ssh.com/">Proprietary SSH</a>\r
809</li>\r
810<li><a href="http://www.imasy.or.jp/~gotoh/ssh/openssh-socks.html">Using OpenSSH through a SOCKS compatible PROXY on your LAN</a> (J. Grant)\r
811</li>\r
812</ul>\r
813\r
814<h3><a name="sec26">Similars</a></h3>\r
815\r
816<ul>\r
817<li><a href="http://proxytunnel.sourceforge.net/">Proxy Tunnel</a> -- Proxying command using https CONNECT.\r
818</li>\r
819<li><a href="http://www.snurgle.org/~griffon/ssh-https-tunnel">stunnel</a> -- Proxy through an https tunnel (Perl script)\r
820</li>\r
821</ul>\r
822<br>\r
823\r
824 <!-- Page published by Emacs Wiki ends here -->\r
825 <div class="navfoot">\r
826 <hr/>\r
827 <table width="100%" border="0" summary="Footer navigation">\r
828 <tbody><tr>\r
829 <td width="50%" align="left">\r
830 <span class="footdate">Last Updated: 2003-06-17</span><br/>\r
831 </td>\r
832 <td width="50%" align="right">\r
833 This page is authored by <a href="mailto:gotoh@taiyo.co.jp">Shun-ichi GOTO</a>\r
834 using <a href="http://repose.cx/emacs/wiki">emacs-wiki.el</a><br/>\r
835 </td>\r
836 </tr></tbody>\r
837 </table>\r
838 </div>\r
839 </body>\r
840</html>\r
OpenSSH free Secure Shell (SSH) implementation
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