6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
19 [B<-certform DER|PEM>]
24 [B<-dcertform DER|PEM>]
26 [B<-dkeyform DER|PEM>]
28 [B<-dhparam filename>]
35 [B<-CApath directory>]
38 [B<-cipher cipherlist>]
62 The B<s_server> command implements a generic SSL/TLS server which listens
63 for connections on a given port using SSL/TLS.
67 In addition to the options below the B<s_server> utility also supports the
68 common and server only options documented in the
69 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
76 the TCP port to listen on for connections. If not specified 4433 is used.
78 =item B<-naccept count>
80 The server will exit after receiving B<number> connections, default unlimited.
84 sets the SSL context id. It can be given any string value. If this option
85 is not present a default value will be used.
87 =item B<-cert certname>
89 The certificate to use, most servers cipher suites require the use of a
90 certificate and some require a certificate with a certain public key type:
91 for example the DSS cipher suites require a certificate containing a DSS
92 (DSA) key. If not specified then the filename "server.pem" will be used.
94 =item B<-certform format>
96 The certificate format to use: DER or PEM. PEM is the default.
100 The private key to use. If not specified then the certificate file will
103 =item B<-keyform format>
105 The private format to use: DER or PEM. PEM is the default.
109 the private key password source. For more information about the format of B<arg>
110 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
112 =item B<-dcert filename>, B<-dkey keyname>
114 specify an additional certificate and private key, these behave in the
115 same manner as the B<-cert> and B<-key> options except there is no default
116 if they are not specified (no additional certificate and key is used). As
117 noted above some cipher suites require a certificate containing a key of
118 a certain type. Some cipher suites need a certificate carrying an RSA key
119 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
120 a server can support clients which only support RSA or DSS cipher suites
121 by using an appropriate certificate.
123 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
125 addtional certificate and private key format and passphrase respectively.
129 if this option is set then no certificate is used. This restricts the
130 cipher suites available to the anonymous ones (currently just anonymous
133 =item B<-dhparam filename>
135 the DH parameter file to use. The ephemeral DH cipher suites generate keys
136 using a set of DH parameters. If not specified then an attempt is made to
137 load the parameters from the server certificate file. If this fails then
138 a static set of parameters hard coded into the s_server program will be used.
142 if this option is set then no DH parameters will be loaded effectively
143 disabling the ephemeral DH cipher suites.
147 certain export cipher suites sometimes use a temporary RSA key, this option
148 disables temporary RSA key generation.
150 =item B<-verify depth>, B<-Verify depth>
152 The verify depth to use. This specifies the maximum length of the
153 client certificate chain and makes the server request a certificate from
154 the client. With the B<-verify> option a certificate is requested but the
155 client does not have to send one, with the B<-Verify> option the client
156 must supply a certificate or an error occurs.
158 =item B<-crl_check>, B<-crl_check_all>
160 Check the peer certificate has not been revoked by its CA.
161 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
162 option all CRLs of all CAs in the chain are checked.
164 =item B<-CApath directory>
166 The directory to use for client certificate verification. This directory
167 must be in "hash format", see B<verify> for more information. These are
168 also used when building the server certificate chain.
170 =item B<-CAfile file>
172 A file containing trusted certificates to use during client authentication
173 and to use when attempting to build the server certificate chain. The list
174 is also used in the list of acceptable client CAs passed to the client when
175 a certificate is requested.
179 prints out the SSL session states.
183 print extensive debugging information including a hex dump of all traffic.
187 show all protocol messages with hex dump.
191 show verbose trace output of protocol messages. OpenSSL needs to be compiled
192 with B<enable-ssl-trace> for this option to work.
196 file to send output of B<-msg> or B<-trace> to, default standard output.
200 tests non blocking I/O
204 turns on non blocking I/O
208 this option translated a line feed from the terminal into CR+LF.
212 inhibit printing of session and certificate information.
214 =item B<-psk_hint hint>
216 Use the PSK identity hint B<hint> when using a PSK cipher suite.
220 Use the PSK key B<key> when using a PSK cipher suite. The key is
221 given as a hexadecimal number without leading 0x, for example -psk
224 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
226 these options disable the use of certain SSL or TLS protocols. By default
227 the initial handshake uses a method which should be compatible with all
228 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
232 there are several known bug in SSL and TLS implementations. Adding this
233 option enables various workarounds.
237 only provide a brief summary of connection parameters instead of the
238 normal verbose output.
242 this option enables a further workaround for some some early Netscape
245 =item B<-cipher cipherlist>
247 this allows the cipher list used by the server to be modified. When
248 the client sends a list of supported ciphers the first client cipher
249 also included in the server list is used. Because the client specifies
250 the preference order, the order of the server cipherlist irrelevant. See
251 the B<ciphers> command for more information.
253 =item B<-tlsextdebug>
255 print out a hex dump of any TLS extensions received from the server.
259 disable RFC4507bis session ticket support.
263 sends a status message back to the client when it connects. This includes
264 lots of information about the ciphers used and various session parameters.
265 The output is in HTML format so this option will normally be used with a
270 emulates a simple web server. Pages will be resolved relative to the
271 current directory, for example if the URL https://myhost/page.html is
272 requested the file ./page.html will be loaded.
276 emulates a simple web server. Pages will be resolved relative to the
277 current directory, for example if the URL https://myhost/page.html is
278 requested the file ./page.html will be loaded. The files loaded are
279 assumed to contain a complete and correct HTTP response (lines that
280 are part of the HTTP response line and headers must end with CRLF).
284 simple test server which just reverses the text received from the client
285 and sends it back to the server. Also sets B<-brief>.
289 specifying an engine (by its unique B<id> string) will cause B<s_server>
290 to attempt to obtain a functional reference to the specified engine,
291 thus initialising it if needed. The engine will then be set as the default
292 for all available algorithms.
294 =item B<-id_prefix arg>
296 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
297 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
298 servers, when each of which might be generating a unique range of session
299 IDs (eg. with a certain prefix).
301 =item B<-rand file(s)>
303 a file or files containing random data used to seed the random number
304 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
305 Multiple files can be specified separated by a OS-dependent character.
306 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
311 =head1 CONNECTED COMMANDS
313 If a connection request is established with an SSL client and neither the
314 B<-www> nor the B<-WWW> option has been used then normally any data received
315 from the client is displayed and any key presses will be sent to the client.
317 Certain single letter commands are also recognized which perform special
318 operations: these are listed below.
324 end the current SSL connection but still accept new connections.
328 end the current SSL connection and exit.
332 renegotiate the SSL session.
336 renegotiate the SSL session and request a client certificate.
340 send some plain text down the underlying TCP connection: this should
341 cause the client to disconnect due to a protocol violation.
345 print out some session cache status information.
351 B<s_server> can be used to debug SSL clients. To accept connections from
352 a web browser the command:
354 openssl s_server -accept 443 -www
356 can be used for example.
358 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
359 suites, so they cannot connect to servers which don't use a certificate
360 carrying an RSA key or a version of OpenSSL with RSA disabled.
362 Although specifying an empty list of CAs when requesting a client certificate
363 is strictly speaking a protocol violation, some SSL clients interpret this to
364 mean any CA is acceptable. This is useful for debugging purposes.
366 The session parameters can printed out using the B<sess_id> program.
370 Because this program has a lot of options and also because some of
371 the techniques used are rather old, the C source of s_server is rather
372 hard to read and not a model of how things should be done. A typical
373 SSL server program would be much simpler.
375 The output of common ciphers is wrong: it just gives the list of ciphers that
376 OpenSSL recognizes and the client supports.
378 There should be a way for the B<s_server> program to print out details of any
379 unknown cipher suites a client says it supports.
383 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>