5 s_server - SSL/TLS server program
24 [B<-certform DER|PEM>]
29 [B<-dcertform DER|PEM>]
31 [B<-dkeyform DER|PEM>]
33 [B<-dhparam filename>]
40 [B<-CApath directory>]
44 [B<-attime timestamp>]
64 [B<-verify_depth num>]
65 [B<-verify_return_error>]
66 [B<-verify_email email>]
67 [B<-verify_hostname hostname>]
69 [B<-verify_name name>]
72 [B<-cipher cipherlist>]
106 [B<-serverinfo file>]
107 [B<-no_resumption_on_reneg>]
110 [B<-status_timeout nsec>]
113 [B<-nextprotoneg protocols>]
117 The B<s_server> command implements a generic SSL/TLS server which listens
118 for connections on a given port using SSL/TLS.
122 In addition to the options below the B<s_server> utility also supports the
123 common and server only options documented in the
124 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
131 Print out a usage message.
135 The TCP port to listen on for connections. If not specified 4433 is used.
139 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
141 =item B<-naccept count>
143 The server will exit after receiving B<number> connections, default unlimited.
147 Unix domain socket to accept on.
151 For -unix, unlink existing socket first.
163 Sets the SSL context id. It can be given any string value. If this option
164 is not present a default value will be used.
166 =item B<-cert certname>
168 The certificate to use, most servers cipher suites require the use of a
169 certificate and some require a certificate with a certain public key type:
170 for example the DSS cipher suites require a certificate containing a DSS
171 (DSA) key. If not specified then the filename "server.pem" will be used.
173 =item B<-certform format>
175 The certificate format to use: DER or PEM. PEM is the default.
177 =item B<-key keyfile>
179 The private key to use. If not specified then the certificate file will
182 =item B<-keyform format>
184 The private format to use: DER or PEM. PEM is the default.
188 The private key password source. For more information about the format of B<arg>
189 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
191 =item B<-dcert filename>, B<-dkey keyname>
193 Specify an additional certificate and private key, these behave in the
194 same manner as the B<-cert> and B<-key> options except there is no default
195 if they are not specified (no additional certificate and key is used). As
196 noted above some cipher suites require a certificate containing a key of
197 a certain type. Some cipher suites need a certificate carrying an RSA key
198 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
199 a server can support clients which only support RSA or DSS cipher suites
200 by using an appropriate certificate.
202 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
204 Additional certificate and private key format and passphrase respectively.
208 If this option is set then no certificate is used. This restricts the
209 cipher suites available to the anonymous ones (currently just anonymous
212 =item B<-dhparam filename>
214 The DH parameter file to use. The ephemeral DH cipher suites generate keys
215 using a set of DH parameters. If not specified then an attempt is made to
216 load the parameters from the server certificate file.
217 If this fails then a static set of parameters hard coded into the B<s_server>
218 program will be used.
222 If this option is set then no DH parameters will be loaded effectively
223 disabling the ephemeral DH cipher suites.
225 =item B<-crl_check>, B<-crl_check_all>
227 Check the peer certificate has not been revoked by its CA.
228 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
229 option all CRLs of all CAs in the chain are checked.
231 =item B<-CApath directory>
233 The directory to use for client certificate verification. This directory
234 must be in "hash format", see B<verify> for more information. These are
235 also used when building the server certificate chain.
237 =item B<-CAfile file>
239 A file containing trusted certificates to use during client authentication
240 and to use when attempting to build the server certificate chain. The list
241 is also used in the list of acceptable client CAs passed to the client when
242 a certificate is requested.
246 Do not load the trusted CA certificates from the default file location
250 Do not load the trusted CA certificates from the default directory location
252 =item B<-verify depth>, B<-Verify depth>
254 The verify depth to use. This specifies the maximum length of the
255 client certificate chain and makes the server request a certificate from
256 the client. With the B<-verify> option a certificate is requested but the
257 client does not have to send one, with the B<-Verify> option the client
258 must supply a certificate or an error occurs.
260 If the ciphersuite cannot request a client certificate (for example an
261 anonymous ciphersuite or PSK) this option has no effect.
263 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
264 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
265 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
266 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
267 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
268 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
269 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
271 Set different peer certificate verification options.
272 See the L<verify(1)> manual page for details.
274 =item B<-verify_return_error>
276 Verification errors normally just print a message but allow the
277 connection to continue, for debugging purposes.
278 If this option is used, then verification errors close the connection.
282 Prints the SSL session states.
286 Print extensive debugging information including a hex dump of all traffic.
290 Show all protocol messages with hex dump.
294 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
295 with B<enable-ssl-trace> for this option to work.
299 File to send output of B<-msg> or B<-trace> to, default standard output.
303 Tests non blocking I/O
307 Turns on non blocking I/O
311 This option translated a line feed from the terminal into CR+LF.
315 Inhibit printing of session and certificate information.
317 =item B<-psk_hint hint>
319 Use the PSK identity hint B<hint> when using a PSK cipher suite.
323 Use the PSK key B<key> when using a PSK cipher suite. The key is
324 given as a hexadecimal number without leading 0x, for example -psk
327 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-tls1_1>, B<-tls1_2>, B<-tls1_3>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
329 These options require or disable the use of the specified SSL or TLS protocols.
330 By default B<s_server> will negotiate the highest mutually supported protocol
332 When a specific TLS version is required, only that version will be accepted
335 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
337 These options make B<s_server> use DTLS protocols instead of TLS.
338 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
339 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
344 This option can only be used in conjunction with one of the DTLS options above.
345 With this option B<s_server> will listen on a UDP port for incoming connections.
346 Any ClientHellos that arrive will be checked to see if they have a cookie in
348 Any without a cookie will be responded to with a HelloVerifyRequest.
349 If a ClientHello with a cookie is received then B<s_server> will connect to
350 that peer and complete the handshake.
354 Switch on asynchronous mode. Cryptographic operations will be performed
355 asynchronously. This will only have an effect if an asynchronous capable engine
356 is also used via the B<-engine> option. For test purposes the dummy async engine
357 (dasync) can be used (if available).
359 =item B<-split_send_frag int>
361 The size used to split data for encrypt pipelines. If more data is written in
362 one go than this value then it will be split into multiple pipelines, up to the
363 maximum number of pipelines defined by max_pipelines. This only has an effect if
364 a suitable ciphersuite has been negotiated, an engine that supports pipelining
365 has been loaded, and max_pipelines is greater than 1. See
366 L<SSL_CTX_set_split_send_fragment(3)> for further information.
368 =item B<-max_pipelines int>
370 The maximum number of encrypt/decrypt pipelines to be used. This will only have
371 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
372 engine) and a suitable ciphersuite has been negotiated. The default value is 1.
373 See L<SSL_CTX_set_max_pipelines(3)> for further information.
375 =item B<-read_buf int>
377 The default read buffer size to be used for connections. This will only have an
378 effect if the buffer size is larger than the size that would otherwise be used
379 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
380 further information).
384 There are several known bug in SSL and TLS implementations. Adding this
385 option enables various workarounds.
389 Enable negotiation of TLS compression.
390 This option was introduced in OpenSSL 1.1.0.
391 TLS compression is not recommended and is off by default as of
396 Disable negotiation of TLS compression.
397 TLS compression is not recommended and is off by default as of
402 Provide a brief summary of connection parameters instead of the normal verbose
405 =item B<-cipher cipherlist>
407 This allows the cipher list used by the server to be modified. When
408 the client sends a list of supported ciphers the first client cipher
409 also included in the server list is used. Because the client specifies
410 the preference order, the order of the server cipherlist irrelevant. See
411 the B<ciphers> command for more information.
415 Use the server's cipher preferences, rather than the client's preferences.
417 =item B<-tlsextdebug>
419 Print a hex dump of any TLS extensions received from the server.
423 Disable RFC4507bis session ticket support.
427 Sends a status message back to the client when it connects. This includes
428 information about the ciphers used and various session parameters.
429 The output is in HTML format so this option will normally be used with a
434 Emulates a simple web server. Pages will be resolved relative to the
435 current directory, for example if the URL https://myhost/page.html is
436 requested the file ./page.html will be loaded.
440 Emulates a simple web server. Pages will be resolved relative to the
441 current directory, for example if the URL https://myhost/page.html is
442 requested the file ./page.html will be loaded. The files loaded are
443 assumed to contain a complete and correct HTTP response (lines that
444 are part of the HTTP response line and headers must end with CRLF).
448 Simple test server which just reverses the text received from the client
449 and sends it back to the server. Also sets B<-brief>.
453 Specifying an engine (by its unique B<id> string) will cause B<s_server>
454 to attempt to obtain a functional reference to the specified engine,
455 thus initialising it if needed. The engine will then be set as the default
456 for all available algorithms.
458 =item B<-id_prefix arg>
460 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
461 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
462 servers, when each of which might be generating a unique range of session
463 IDs (eg. with a certain prefix).
465 =item B<-rand file(s)>
467 A file or files containing random data used to seed the random number
468 generator, or an EGD socket (see L<RAND_egd(3)>).
469 Multiple files can be specified separated by an OS-dependent character.
470 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
473 =item B<-serverinfo file>
475 A file containing one or more blocks of PEM data. Each PEM block
476 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
477 followed by "length" bytes of extension data). If the client sends
478 an empty TLS ClientHello extension matching the type, the corresponding
479 ServerHello extension will be returned.
481 =item B<-no_resumption_on_reneg>
483 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
487 Enables certificate status request support (aka OCSP stapling).
489 =item B<-status_verbose>
491 Enables certificate status request support (aka OCSP stapling) and gives
492 a verbose printout of the OCSP response.
494 =item B<-status_timeout nsec>
496 Sets the timeout for OCSP response to B<nsec> seconds.
498 =item B<-status_url url>
500 Sets a fallback responder URL to use if no responder URL is present in the
501 server certificate. Without this option an error is returned if the server
502 certificate does not contain a responder address.
504 =item B<-alpn protocols>, B<-nextprotoneg protocols>
506 these flags enable the
507 Enable the Application-Layer Protocol Negotiation or Next Protocol
508 Negotiation extension, respectively. ALPN is the IETF standard and
510 The B<protocols> list is a
511 comma-separated list of supported protocol names.
512 The list should contain most wanted protocols first.
513 Protocol names are printable ASCII strings, for example "http/1.1" or
518 =head1 CONNECTED COMMANDS
520 If a connection request is established with an SSL client and neither the
521 B<-www> nor the B<-WWW> option has been used then normally any data received
522 from the client is displayed and any key presses will be sent to the client.
524 Certain single letter commands are also recognized which perform special
525 operations: these are listed below.
531 end the current SSL connection but still accept new connections.
535 end the current SSL connection and exit.
539 renegotiate the SSL session.
543 renegotiate the SSL session and request a client certificate.
547 send some plain text down the underlying TCP connection: this should
548 cause the client to disconnect due to a protocol violation.
552 print out some session cache status information.
558 B<s_server> can be used to debug SSL clients. To accept connections from
559 a web browser the command:
561 openssl s_server -accept 443 -www
563 can be used for example.
565 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
566 suites, so they cannot connect to servers which don't use a certificate
567 carrying an RSA key or a version of OpenSSL with RSA disabled.
569 Although specifying an empty list of CAs when requesting a client certificate
570 is strictly speaking a protocol violation, some SSL clients interpret this to
571 mean any CA is acceptable. This is useful for debugging purposes.
573 The session parameters can printed out using the B<sess_id> program.
577 Because this program has a lot of options and also because some of the
578 techniques used are rather old, the C source of B<s_server> is rather hard to
579 read and not a model of how things should be done.
580 A typical SSL server program would be much simpler.
582 The output of common ciphers is wrong: it just gives the list of ciphers that
583 OpenSSL recognizes and the client supports.
585 There should be a way for the B<s_server> program to print out details of any
586 unknown cipher suites a client says it supports.
591 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
595 The -no_alt_chains options was first added to OpenSSL 1.1.0.
599 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
601 Licensed under the OpenSSL license (the "License"). You may not use
602 this file except in compliance with the License. You can obtain a copy
603 in the file LICENSE in the source distribution or at
604 L<https://www.openssl.org/source/license.html>.