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 B<SUPPORTED COMMAND LINE OPTIONS> section in L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)>.
75 the TCP port to listen on for connections. If not specified 4433 is used.
77 =item B<-naccept count>
79 The server will exit after receiving B<number> connections, default unlimited.
83 sets the SSL context id. It can be given any string value. If this option
84 is not present a default value will be used.
86 =item B<-cert certname>
88 The certificate to use, most servers cipher suites require the use of a
89 certificate and some require a certificate with a certain public key type:
90 for example the DSS cipher suites require a certificate containing a DSS
91 (DSA) key. If not specified then the filename "server.pem" will be used.
93 =item B<-certform format>
95 The certificate format to use: DER or PEM. PEM is the default.
99 The private key to use. If not specified then the certificate file will
102 =item B<-keyform format>
104 The private format to use: DER or PEM. PEM is the default.
108 the private key password source. For more information about the format of B<arg>
109 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
111 =item B<-dcert filename>, B<-dkey keyname>
113 specify an additional certificate and private key, these behave in the
114 same manner as the B<-cert> and B<-key> options except there is no default
115 if they are not specified (no additional certificate and key is used). As
116 noted above some cipher suites require a certificate containing a key of
117 a certain type. Some cipher suites need a certificate carrying an RSA key
118 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
119 a server can support clients which only support RSA or DSS cipher suites
120 by using an appropriate certificate.
122 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
124 addtional certificate and private key format and passphrase respectively.
128 if this option is set then no certificate is used. This restricts the
129 cipher suites available to the anonymous ones (currently just anonymous
132 =item B<-dhparam filename>
134 the DH parameter file to use. The ephemeral DH cipher suites generate keys
135 using a set of DH parameters. If not specified then an attempt is made to
136 load the parameters from the server certificate file. If this fails then
137 a static set of parameters hard coded into the s_server program will be used.
141 if this option is set then no DH parameters will be loaded effectively
142 disabling the ephemeral DH cipher suites.
146 certain export cipher suites sometimes use a temporary RSA key, this option
147 disables temporary RSA key generation.
149 =item B<-verify depth>, B<-Verify depth>
151 The verify depth to use. This specifies the maximum length of the
152 client certificate chain and makes the server request a certificate from
153 the client. With the B<-verify> option a certificate is requested but the
154 client does not have to send one, with the B<-Verify> option the client
155 must supply a certificate or an error occurs.
157 =item B<-crl_check>, B<-crl_check_all>
159 Check the peer certificate has not been revoked by its CA.
160 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
161 option all CRLs of all CAs in the chain are checked.
163 =item B<-CApath directory>
165 The directory to use for client certificate verification. This directory
166 must be in "hash format", see B<verify> for more information. These are
167 also used when building the server certificate chain.
169 =item B<-CAfile file>
171 A file containing trusted certificates to use during client authentication
172 and to use when attempting to build the server certificate chain. The list
173 is also used in the list of acceptable client CAs passed to the client when
174 a certificate is requested.
178 prints out the SSL session states.
182 print extensive debugging information including a hex dump of all traffic.
186 show all protocol messages with hex dump.
190 show verbose trace output of protocol messages. OpenSSL needs to be compiled
191 with B<enable-ssl-trace> for this option to work.
195 file to send output of B<-msg> or B<-trace> to, default standard output.
199 tests non blocking I/O
203 turns on non blocking I/O
207 this option translated a line feed from the terminal into CR+LF.
211 inhibit printing of session and certificate information.
213 =item B<-psk_hint hint>
215 Use the PSK identity hint B<hint> when using a PSK cipher suite.
219 Use the PSK key B<key> when using a PSK cipher suite. The key is
220 given as a hexadecimal number without leading 0x, for example -psk
223 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
225 these options disable the use of certain SSL or TLS protocols. By default
226 the initial handshake uses a method which should be compatible with all
227 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
231 there are several known bug in SSL and TLS implementations. Adding this
232 option enables various workarounds.
236 only provide a brief summary of connection parameters instead of the
237 normal verbose output.
241 this option enables a further workaround for some some early Netscape
244 =item B<-cipher cipherlist>
246 this allows the cipher list used by the server to be modified. When
247 the client sends a list of supported ciphers the first client cipher
248 also included in the server list is used. Because the client specifies
249 the preference order, the order of the server cipherlist irrelevant. See
250 the B<ciphers> command for more information.
252 =item B<-tlsextdebug>
254 print out a hex dump of any TLS extensions received from the server.
258 disable RFC4507bis session ticket support.
262 sends a status message back to the client when it connects. This includes
263 lots of information about the ciphers used and various session parameters.
264 The output is in HTML format so this option will normally be used with a
269 emulates a simple web server. Pages will be resolved relative to the
270 current directory, for example if the URL https://myhost/page.html is
271 requested the file ./page.html will be loaded.
275 emulates a simple web server. Pages will be resolved relative to the
276 current directory, for example if the URL https://myhost/page.html is
277 requested the file ./page.html will be loaded. The files loaded are
278 assumed to contain a complete and correct HTTP response (lines that
279 are part of the HTTP response line and headers must end with CRLF).
283 simple test server which just reverses the text received from the client
284 and sends it back to the server. Also sets B<-brief>.
288 specifying an engine (by its unique B<id> string) will cause B<s_server>
289 to attempt to obtain a functional reference to the specified engine,
290 thus initialising it if needed. The engine will then be set as the default
291 for all available algorithms.
293 =item B<-id_prefix arg>
295 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
296 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
297 servers, when each of which might be generating a unique range of session
298 IDs (eg. with a certain prefix).
300 =item B<-rand file(s)>
302 a file or files containing random data used to seed the random number
303 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
304 Multiple files can be specified separated by a OS-dependent character.
305 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
310 =head1 CONNECTED COMMANDS
312 If a connection request is established with an SSL client and neither the
313 B<-www> nor the B<-WWW> option has been used then normally any data received
314 from the client is displayed and any key presses will be sent to the client.
316 Certain single letter commands are also recognized which perform special
317 operations: these are listed below.
323 end the current SSL connection but still accept new connections.
327 end the current SSL connection and exit.
331 renegotiate the SSL session.
335 renegotiate the SSL session and request a client certificate.
339 send some plain text down the underlying TCP connection: this should
340 cause the client to disconnect due to a protocol violation.
344 print out some session cache status information.
350 B<s_server> can be used to debug SSL clients. To accept connections from
351 a web browser the command:
353 openssl s_server -accept 443 -www
355 can be used for example.
357 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
358 suites, so they cannot connect to servers which don't use a certificate
359 carrying an RSA key or a version of OpenSSL with RSA disabled.
361 Although specifying an empty list of CAs when requesting a client certificate
362 is strictly speaking a protocol violation, some SSL clients interpret this to
363 mean any CA is acceptable. This is useful for debugging purposes.
365 The session parameters can printed out using the B<sess_id> program.
369 Because this program has a lot of options and also because some of
370 the techniques used are rather old, the C source of s_server is rather
371 hard to read and not a model of how things should be done. A typical
372 SSL server program would be much simpler.
374 The output of common ciphers is wrong: it just gives the list of ciphers that
375 OpenSSL recognizes and the client supports.
377 There should be a way for the B<s_server> program to print out details of any
378 unknown cipher suites a client says it supports.
382 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>