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1 # I'm just not gonna write troff :-)
2 
3 =head1 NAME
4 
5  sslh - protocol demultiplexer
6 
7 =head1 SYNOPSIS
8 
9 sslh [B<-F>I<config file>] [ B<-t> I<num> ] [B<--transparent>] [B<-p> I<listening address> [B<-p> I<listening address> ...] [B<--ssl> I<target address for SSL>] [B<--tls> I<target address for TLS>] [B<--ssh> I<target address for SSH>] [B<--openvpn> I<target address for OpenVPN>] [B<--http> I<target address for HTTP>] [B<--xmpp> I<target address for XMPP>] [B<--tinc> I<target address for TINC>] [B<--anyprot> I<default target address>] [B<--on-timeout> I<protocol name>] [B<-u> I<username>] [B<-P> I<pidfile>] [-v] [-i] [-V] [-f] [-n]
10 
11 =head1 DESCRIPTION
12 
13 B<sslh> accepts connections on specified ports, and forwards
14 them further based on tests performed on the first data
15 packet sent by the remote client.
16 
17 Probes for HTTP, SSL, SSH, OpenVPN, tinc, XMPP are
18 implemented, and any other protocol that can be tested using
19 a regular expression, can be recognised. A typical use case
20 is to allow serving several services on port 443 (e.g. to
21 connect to ssh from inside a corporate firewall, which
22 almost never block port 443) while still serving HTTPS on
23 that port. 
24 
25 Hence B<sslh> acts as a protocol demultiplexer, or a
26 switchboard. Its name comes from its original function to
27 serve SSH and HTTPS on the same port.
28 
29 =head2 Libwrap support
30 
31 One drawback of B<sslh> is that the servers do not see the
32 original IP address of the client anymore, as the connection
33 is forwarded through B<sslh>.
34 
35 For this reason, B<sslh> can be compiled with B<libwrap> to
36 check accesses defined in F</etc/hosts.allow> and
37 F</etc/hosts.deny>.  Libwrap services can be defined using
38 the configuration file.
39 
40 =head2 Configuration file
41 
42 A configuration file can be supplied to B<sslh>. Command
43 line arguments override file settings. B<sslh> uses
44 B<libconfig> to parse the configuration file, so the general
45 file format is indicated in
46 L<http://www.hyperrealm.com/libconfig/libconfig_manual.html>.
47 Please refer to the example configuration file provided with
48 B<sslh> for the specific format (Options have the same names
49 as on the command line, except for the list of listen ports
50 and the list of protocols).
51 
52 The configuration file makes it possible to specify
53 protocols using regular expressions: a list of regular
54 expressions is given as the I<regex_patterns> parameter, and if the
55 first packet received from the client matches any of these
56 expressions, B<sslh> connects to that protocol.
57 
58 =head2 Probing protocols
59 
60 When receiving an incoming connection, B<sslh> will read the
61 first bytes sent by the connecting client. It will then
62 probe for the protocol in the order specified on the command
63 line (or the configuration file). Therefore B<--anyprot>
64 should alway be used last, as it always succeeds and further
65 protocols will never be tried.
66 
67 If no data is sent by the client, B<sslh> will eventually
68 time out and connect to the protocol specified with
69 B<--on-timeout>, or I<ssh> if none is specified.
70 
71 =head2 Logging
72 
73 As a security/authorization program, B<sslh> logs to the
74 LOG_AUTH facility, with priority LOG_INFO for normal
75 connections and LOG_ERR for failures.
76 
77 =head1 OPTIONS
78 
79 =over 4
80 
81 =item B<-F>I<filename>, B<--config> I<filename>
82 
83 Uses I<filename> as configuration file. If other
84 command-line options are specified, they will override the
85 configuration file's settings.
86 
87 When using the shorthand version, make sure there should be
88 no space between B<-F> and the I<filename>.
89 
90 =item B<-t> I<num>, B<--timeout> I<num>
91 
92 Timeout before forwarding the connection to the timeout
93 protocol (which should usually be SSH). Default is 2s.
94 
95 =item B<--on-timeout> I<protocol name>
96 
97 Name of the protocol to connect to after the timeout period
98 is over. Default is 'ssh'.
99 
100 =item B<--transparent>
101 
102 Makes B<sslh> behave as a transparent proxy, i.e. the
103 receiving service sees the original client's IP address.
104 This works on Linux only and involves B<iptables> settings.
105 Refer to the README for more information.
106 
107 =item B<-p> I<listening address>, B<--listen> I<listening address>
108 
109 Interface and port on which to listen, e.g. I<foobar:443>,
110 where I<foobar> is the name of an interface (typically the
111 IP address on which the Internet connection ends up).
112 
113 This can be specified several times to bind B<sslh> to
114 several addresses.
115 
116 =item B<--ssl> I<target address>
117 
118 =item B<--tls> I<target address>
119 
120 Interface and port on which to forward SSL connection,
121 typically I<localhost:443>.
122 
123 Note that you can set B<sslh> to listen on I<ext_ip:443> and
124 B<httpd> to listen on I<localhost:443>: this allows clients
125 inside your network to just connect directly to B<httpd>.
126 
127 Also, B<sslh> probes for SSLv3 (or TLSv1) handshake and will
128 reject connections from clients requesting SSLv2. This is
129 compliant with RFC6176 which prohibits the usage of SSLv2. If
130 you wish to accept SSLv2, use B<--default> instead.
131 
132 =item B<--ssh> I<target address>
133 
134 Interface and port on which to forward SSH connections,
135 typically I<localhost:22>.
136 
137 =item B<--openvpn> I<target address>
138 
139 Interface and port on which to forward OpenVPN connections,
140 typically I<localhost:1194>.
141 
142 =item B<--xmpp> I<target address>
143 
144 Interface and port on which to forward XMPP connections,
145 typically I<localhost:5222>.
146 
147 =item B<--http> I<target address>
148 
149 Interface and port on which to forward HTTP connections,
150 typically I<localhost:80>.
151 
152 =item B<--tinc> I<target address>
153 
154 Interface and port on which to forward tinc connections,
155 typically I<localhost:655>.
156 
157 This is experimental. If you use this feature, please report
158 the results (even if it works!)
159 
160 =item B<--anyprot> I<target address>
161 
162 Interface and port on which to forward if no other protocol
163 has been found. Because B<sslh> tries protocols in the order
164 specified on the command line, this should be specified
165 last. If no default is specified, B<sslh> will forward
166 unknown protocols to the first protocol specified.
167 
168 =item B<-v>, B<--verbose>
169 
170 Increase verboseness.
171 
172 =item B<-n>, B<--numeric>
173 
174 Do not attempt to resolve hostnames: logs will contain IP
175 addresses. This is mostly useful if the system's DNS is slow
176 and running the I<sslh-select> variant, as DNS requests will
177 hang all connections.
178 
179 =item B<-V>
180 
181 Prints B<sslh> version.
182 
183 =item B<-u> I<username>, B<--user> I<username>
184 
185 Requires to run under the specified username. 
186 
187 =item B<-P> I<pidfile>, B<--pidfile> I<pidfile>
188 
189 Specifies a file in which to write the PID of the main
190 server.
191 
192 =item B<-i>, B<--inetd>
193 
194 Runs as an I<inetd> server. Options B<-P> (PID file), B<-p>
195 (listen address), B<-u> (user) are ignored.
196 
197 =item B<-f>, B<--foreground>
198 
199 Runs in foreground. The server will not fork and will remain connected
200 to the terminal. Messages normally sent to B<syslog> will also be sent
201 to I<stderr>.
202 
203 =item B<--background>
204 
205 Runs in background. This overrides B<foreground> if set in
206 the configuration file (or on the command line, but there is
207 no point setting both on the command line unless you have a
208 personality disorder).
209 
210 =back
211 
212 =head1 FILES
213 
214 =over 4
215 
216 =item F</etc/init.d/sslh>
217 
218 Start-up script. The standard actions B<start>, B<stop> and
219 B<restart> are supported.
220 
221 =item F</etc/default/sslh>
222 
223 Server configuration. These are environment variables
224 loaded by the start-up script and passed to B<sslh> as
225 command-line arguments. Refer to the OPTIONS section for a
226 detailed explanation of the variables used by B<sslh>.
227 
228 =back
229 
230 =head1 SEE ALSO
231 
232 The latest version is available from
233 L<http://www.rutschle.net/tech/sslh>, and can be tracked
234 from L<http://freecode.com/projects/sslh>.
235 
236 =head1 AUTHOR
237 
238 Written by Yves Rutschle.
239

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cel / sslh

Tree: 6cc33820d166bc790c79f8e42aec8f53bcefd2ba

Files: 6cc33820d166bc790c79f8e42aec8f53bcefd2ba / sslh.pod

1	# I'm just not gonna write troff :-)
2
3	=head1 NAME
4
5	sslh - protocol demultiplexer
6
7	=head1 SYNOPSIS
8
9	sslh [B<-F>I<config file>] [ B<-t> I<num> ] [B<--transparent>] [B<-p> I<listening address> [B<-p> I<listening address> ...] [B<--ssl> I<target address for SSL>] [B<--tls> I<target address for TLS>] [B<--ssh> I<target address for SSH>] [B<--openvpn> I<target address for OpenVPN>] [B<--http> I<target address for HTTP>] [B<--xmpp> I<target address for XMPP>] [B<--tinc> I<target address for TINC>] [B<--anyprot> I<default target address>] [B<--on-timeout> I<protocol name>] [B<-u> I<username>] [B<-P> I<pidfile>] [-v] [-i] [-V] [-f] [-n]
10
11	=head1 DESCRIPTION
12
13	B<sslh> accepts connections on specified ports, and forwards
14	them further based on tests performed on the first data
15	packet sent by the remote client.
16
17	Probes for HTTP, SSL, SSH, OpenVPN, tinc, XMPP are
18	implemented, and any other protocol that can be tested using
19	a regular expression, can be recognised. A typical use case
20	is to allow serving several services on port 443 (e.g. to
21	connect to ssh from inside a corporate firewall, which
22	almost never block port 443) while still serving HTTPS on
23	that port.
24
25	Hence B<sslh> acts as a protocol demultiplexer, or a
26	switchboard. Its name comes from its original function to
27	serve SSH and HTTPS on the same port.
28
29	=head2 Libwrap support
30
31	One drawback of B<sslh> is that the servers do not see the
32	original IP address of the client anymore, as the connection
33	is forwarded through B<sslh>.
34
35	For this reason, B<sslh> can be compiled with B<libwrap> to
36	check accesses defined in F</etc/hosts.allow> and
37	F</etc/hosts.deny>. Libwrap services can be defined using
38	the configuration file.
39
40	=head2 Configuration file
41
42	A configuration file can be supplied to B<sslh>. Command
43	line arguments override file settings. B<sslh> uses
44	B<libconfig> to parse the configuration file, so the general
45	file format is indicated in
46	L<http://www.hyperrealm.com/libconfig/libconfig_manual.html>.
47	Please refer to the example configuration file provided with
48	B<sslh> for the specific format (Options have the same names
49	as on the command line, except for the list of listen ports
50	and the list of protocols).
51
52	The configuration file makes it possible to specify
53	protocols using regular expressions: a list of regular
54	expressions is given as the I<regex_patterns> parameter, and if the
55	first packet received from the client matches any of these
56	expressions, B<sslh> connects to that protocol.
57
58	=head2 Probing protocols
59
60	When receiving an incoming connection, B<sslh> will read the
61	first bytes sent by the connecting client. It will then
62	probe for the protocol in the order specified on the command
63	line (or the configuration file). Therefore B<--anyprot>
64	should alway be used last, as it always succeeds and further
65	protocols will never be tried.
66
67	If no data is sent by the client, B<sslh> will eventually
68	time out and connect to the protocol specified with
69	B<--on-timeout>, or I<ssh> if none is specified.
70
71	=head2 Logging
72
73	As a security/authorization program, B<sslh> logs to the
74	LOG_AUTH facility, with priority LOG_INFO for normal
75	connections and LOG_ERR for failures.
76
77	=head1 OPTIONS
78
79	=over 4
80
81	=item B<-F>I<filename>, B<--config> I<filename>
82
83	Uses I<filename> as configuration file. If other
84	command-line options are specified, they will override the
85	configuration file's settings.
86
87	When using the shorthand version, make sure there should be
88	no space between B<-F> and the I<filename>.
89
90	=item B<-t> I<num>, B<--timeout> I<num>
91
92	Timeout before forwarding the connection to the timeout
93	protocol (which should usually be SSH). Default is 2s.
94
95	=item B<--on-timeout> I<protocol name>
96
97	Name of the protocol to connect to after the timeout period
98	is over. Default is 'ssh'.
99
100	=item B<--transparent>
101
102	Makes B<sslh> behave as a transparent proxy, i.e. the
103	receiving service sees the original client's IP address.
104	This works on Linux only and involves B<iptables> settings.
105	Refer to the README for more information.
106
107	=item B<-p> I<listening address>, B<--listen> I<listening address>
108
109	Interface and port on which to listen, e.g. I<foobar:443>,
110	where I<foobar> is the name of an interface (typically the
111	IP address on which the Internet connection ends up).
112
113	This can be specified several times to bind B<sslh> to
114	several addresses.
115
116	=item B<--ssl> I<target address>
117
118	=item B<--tls> I<target address>
119
120	Interface and port on which to forward SSL connection,
121	typically I<localhost:443>.
122
123	Note that you can set B<sslh> to listen on I<ext_ip:443> and
124	B<httpd> to listen on I<localhost:443>: this allows clients
125	inside your network to just connect directly to B<httpd>.
126
127	Also, B<sslh> probes for SSLv3 (or TLSv1) handshake and will
128	reject connections from clients requesting SSLv2. This is
129	compliant with RFC6176 which prohibits the usage of SSLv2. If
130	you wish to accept SSLv2, use B<--default> instead.
131
132	=item B<--ssh> I<target address>
133
134	Interface and port on which to forward SSH connections,
135	typically I<localhost:22>.
136
137	=item B<--openvpn> I<target address>
138
139	Interface and port on which to forward OpenVPN connections,
140	typically I<localhost:1194>.
141
142	=item B<--xmpp> I<target address>
143
144	Interface and port on which to forward XMPP connections,
145	typically I<localhost:5222>.
146
147	=item B<--http> I<target address>
148
149	Interface and port on which to forward HTTP connections,
150	typically I<localhost:80>.
151
152	=item B<--tinc> I<target address>
153
154	Interface and port on which to forward tinc connections,
155	typically I<localhost:655>.
156
157	This is experimental. If you use this feature, please report
158	the results (even if it works!)
159
160	=item B<--anyprot> I<target address>
161
162	Interface and port on which to forward if no other protocol
163	has been found. Because B<sslh> tries protocols in the order
164	specified on the command line, this should be specified
165	last. If no default is specified, B<sslh> will forward
166	unknown protocols to the first protocol specified.
167
168	=item B<-v>, B<--verbose>
169
170	Increase verboseness.
171
172	=item B<-n>, B<--numeric>
173
174	Do not attempt to resolve hostnames: logs will contain IP
175	addresses. This is mostly useful if the system's DNS is slow
176	and running the I<sslh-select> variant, as DNS requests will
177	hang all connections.
178
179	=item B<-V>
180
181	Prints B<sslh> version.
182
183	=item B<-u> I<username>, B<--user> I<username>
184
185	Requires to run under the specified username.
186
187	=item B<-P> I<pidfile>, B<--pidfile> I<pidfile>
188
189	Specifies a file in which to write the PID of the main
190	server.
191
192	=item B<-i>, B<--inetd>
193
194	Runs as an I<inetd> server. Options B<-P> (PID file), B<-p>
195	(listen address), B<-u> (user) are ignored.
196
197	=item B<-f>, B<--foreground>
198
199	Runs in foreground. The server will not fork and will remain connected
200	to the terminal. Messages normally sent to B<syslog> will also be sent
201	to I<stderr>.
202
203	=item B<--background>
204
205	Runs in background. This overrides B<foreground> if set in
206	the configuration file (or on the command line, but there is
207	no point setting both on the command line unless you have a
208	personality disorder).
209
210	=back
211
212	=head1 FILES
213
214	=over 4
215
216	=item F</etc/init.d/sslh>
217
218	Start-up script. The standard actions B<start>, B<stop> and
219	B<restart> are supported.
220
221	=item F</etc/default/sslh>
222
223	Server configuration. These are environment variables
224	loaded by the start-up script and passed to B<sslh> as
225	command-line arguments. Refer to the OPTIONS section for a
226	detailed explanation of the variables used by B<sslh>.
227
228	=back
229
230	=head1 SEE ALSO
231
232	The latest version is available from
233	L<http://www.rutschle.net/tech/sslh>, and can be tracked
234	from L<http://freecode.com/projects/sslh>.
235
236	=head1 AUTHOR
237
238	Written by Yves Rutschle.
239

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