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>]
37 [B<-attime timestamp>]
56 [B<-verify_depth num>]
57 [B<-verify_return_error>]
58 [B<-verify_email email>]
59 [B<-verify_hostname hostname>]
61 [B<-verify_name name>]
64 [B<-cipher cipherlist>]
85 [B<-no_resumption_on_reneg>]
88 [B<-status_timeout nsec>]
90 [B<-nextprotoneg protocols>]
94 The B<s_server> command implements a generic SSL/TLS server which listens
95 for connections on a given port using SSL/TLS.
99 In addition to the options below the B<s_server> utility also supports the
100 common and server only options documented in the
101 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
106 =item B<-accept port>
108 the TCP port to listen on for connections. If not specified 4433 is used.
110 =item B<-naccept count>
112 The server will exit after receiving B<number> connections, default unlimited.
116 sets the SSL context id. It can be given any string value. If this option
117 is not present a default value will be used.
119 =item B<-cert certname>
121 The certificate to use, most servers cipher suites require the use of a
122 certificate and some require a certificate with a certain public key type:
123 for example the DSS cipher suites require a certificate containing a DSS
124 (DSA) key. If not specified then the filename "server.pem" will be used.
126 =item B<-certform format>
128 The certificate format to use: DER or PEM. PEM is the default.
130 =item B<-key keyfile>
132 The private key to use. If not specified then the certificate file will
135 =item B<-keyform format>
137 The private format to use: DER or PEM. PEM is the default.
141 the private key password source. For more information about the format of B<arg>
142 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
144 =item B<-dcert filename>, B<-dkey keyname>
146 specify an additional certificate and private key, these behave in the
147 same manner as the B<-cert> and B<-key> options except there is no default
148 if they are not specified (no additional certificate and key is used). As
149 noted above some cipher suites require a certificate containing a key of
150 a certain type. Some cipher suites need a certificate carrying an RSA key
151 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
152 a server can support clients which only support RSA or DSS cipher suites
153 by using an appropriate certificate.
155 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
157 additional certificate and private key format and passphrase respectively.
161 if this option is set then no certificate is used. This restricts the
162 cipher suites available to the anonymous ones (currently just anonymous
165 =item B<-dhparam filename>
167 the DH parameter file to use. The ephemeral DH cipher suites generate keys
168 using a set of DH parameters. If not specified then an attempt is made to
169 load the parameters from the server certificate file. If this fails then
170 a static set of parameters hard coded into the s_server program will be used.
174 if this option is set then no DH parameters will be loaded effectively
175 disabling the ephemeral DH cipher suites.
179 if this option is set then no ECDH parameters will be loaded effectively
180 disabling the ephemeral ECDH cipher suites.
184 certain export cipher suites sometimes use a temporary RSA key, this option
185 disables temporary RSA key generation.
187 =item B<-crl_check>, B<-crl_check_all>
189 Check the peer certificate has not been revoked by its CA.
190 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
191 option all CRLs of all CAs in the chain are checked.
193 =item B<-CApath directory>
195 The directory to use for client certificate verification. This directory
196 must be in "hash format", see B<verify> for more information. These are
197 also used when building the server certificate chain.
199 =item B<-CAfile file>
201 A file containing trusted certificates to use during client authentication
202 and to use when attempting to build the server certificate chain. The list
203 is also used in the list of acceptable client CAs passed to the client when
204 a certificate is requested.
206 =item B<-verify depth>, B<-Verify depth>
208 The verify depth to use. This specifies the maximum length of the
209 client certificate chain and makes the server request a certificate from
210 the client. With the B<-verify> option a certificate is requested but the
211 client does not have to send one, with the B<-Verify> option the client
212 must supply a certificate or an error occurs.
214 If the ciphersuite cannot request a client certificate (for example an
215 anonymous ciphersuite or PSK) this option has no effect.
217 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
218 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
219 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
220 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
221 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
222 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
224 Set different peer certificate verification options.
225 See the L<B<verify>|verify(1)> manual page for details.
227 =item B<-verify_return_error>
229 Verification errors normally just print a message but allow the
230 connection to continue, for debugging purposes.
231 If this option is used, then verification errors close the connection.
235 prints out the SSL session states.
239 print extensive debugging information including a hex dump of all traffic.
243 show all protocol messages with hex dump.
247 show verbose trace output of protocol messages. OpenSSL needs to be compiled
248 with B<enable-ssl-trace> for this option to work.
252 file to send output of B<-msg> or B<-trace> to, default standard output.
256 tests non blocking I/O
260 turns on non blocking I/O
264 this option translated a line feed from the terminal into CR+LF.
268 inhibit printing of session and certificate information.
270 =item B<-psk_hint hint>
272 Use the PSK identity hint B<hint> when using a PSK cipher suite.
276 Use the PSK key B<key> when using a PSK cipher suite. The key is
277 given as a hexadecimal number without leading 0x, for example -psk
280 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
282 these options disable the use of certain SSL or TLS protocols. By default
283 the initial handshake uses a method which should be compatible with all
284 servers and permit them to use SSL v3 or TLS as appropriate.
288 there are several known bug in SSL and TLS implementations. Adding this
289 option enables various workarounds.
293 only provide a brief summary of connection parameters instead of the
294 normal verbose output.
296 =item B<-cipher cipherlist>
298 this allows the cipher list used by the server to be modified. When
299 the client sends a list of supported ciphers the first client cipher
300 also included in the server list is used. Because the client specifies
301 the preference order, the order of the server cipherlist irrelevant. See
302 the B<ciphers> command for more information.
306 use the server's cipher preferences, rather than the client's preferences.
308 =item B<-tlsextdebug>
310 print out a hex dump of any TLS extensions received from the server.
314 disable RFC4507bis session ticket support.
318 sends a status message back to the client when it connects. This includes
319 lots of information about the ciphers used and various session parameters.
320 The output is in HTML format so this option will normally be used with a
325 emulates a simple web server. Pages will be resolved relative to the
326 current directory, for example if the URL https://myhost/page.html is
327 requested the file ./page.html will be loaded.
331 emulates a simple web server. Pages will be resolved relative to the
332 current directory, for example if the URL https://myhost/page.html is
333 requested the file ./page.html will be loaded. The files loaded are
334 assumed to contain a complete and correct HTTP response (lines that
335 are part of the HTTP response line and headers must end with CRLF).
339 simple test server which just reverses the text received from the client
340 and sends it back to the server. Also sets B<-brief>.
344 specifying an engine (by its unique B<id> string) will cause B<s_server>
345 to attempt to obtain a functional reference to the specified engine,
346 thus initialising it if needed. The engine will then be set as the default
347 for all available algorithms.
349 =item B<-id_prefix arg>
351 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
352 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
353 servers, when each of which might be generating a unique range of session
354 IDs (eg. with a certain prefix).
356 =item B<-rand file(s)>
358 a file or files containing random data used to seed the random number
359 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
360 Multiple files can be specified separated by a OS-dependent character.
361 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
364 =item B<-serverinfo file>
366 a file containing one or more blocks of PEM data. Each PEM block
367 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
368 followed by "length" bytes of extension data). If the client sends
369 an empty TLS ClientHello extension matching the type, the corresponding
370 ServerHello extension will be returned.
372 =item B<-no_resumption_on_reneg>
374 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
378 enables certificate status request support (aka OCSP stapling).
380 =item B<-status_verbose>
382 enables certificate status request support (aka OCSP stapling) and gives
383 a verbose printout of the OCSP response.
385 =item B<-status_timeout nsec>
387 sets the timeout for OCSP response to B<nsec> seconds.
389 =item B<-status_url url>
391 sets a fallback responder URL to use if no responder URL is present in the
392 server certificate. Without this option an error is returned if the server
393 certificate does not contain a responder address.
395 =item B<-nextprotoneg protocols>
397 enable Next Protocol Negotiation TLS extension and provide a
398 comma-separated list of supported protocol names.
399 The list should contain most wanted protocols first.
400 Protocol names are printable ASCII strings, for example "http/1.1" or
405 =head1 CONNECTED COMMANDS
407 If a connection request is established with an SSL client and neither the
408 B<-www> nor the B<-WWW> option has been used then normally any data received
409 from the client is displayed and any key presses will be sent to the client.
411 Certain single letter commands are also recognized which perform special
412 operations: these are listed below.
418 end the current SSL connection but still accept new connections.
422 end the current SSL connection and exit.
426 renegotiate the SSL session.
430 renegotiate the SSL session and request a client certificate.
434 send some plain text down the underlying TCP connection: this should
435 cause the client to disconnect due to a protocol violation.
439 print out some session cache status information.
445 B<s_server> can be used to debug SSL clients. To accept connections from
446 a web browser the command:
448 openssl s_server -accept 443 -www
450 can be used for example.
452 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
453 suites, so they cannot connect to servers which don't use a certificate
454 carrying an RSA key or a version of OpenSSL with RSA disabled.
456 Although specifying an empty list of CAs when requesting a client certificate
457 is strictly speaking a protocol violation, some SSL clients interpret this to
458 mean any CA is acceptable. This is useful for debugging purposes.
460 The session parameters can printed out using the B<sess_id> program.
464 Because this program has a lot of options and also because some of
465 the techniques used are rather old, the C source of s_server is rather
466 hard to read and not a model of how things should be done. A typical
467 SSL server program would be much simpler.
469 The output of common ciphers is wrong: it just gives the list of ciphers that
470 OpenSSL recognizes and the client supports.
472 There should be a way for the B<s_server> program to print out details of any
473 unknown cipher suites a client says it supports.
477 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>
481 The -no_alt_chains options was first added to OpenSSL 1.1.0.