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>]
65 [B<-verify_depth num>]
66 [B<-verify_return_error>]
67 [B<-verify_email email>]
68 [B<-verify_hostname hostname>]
70 [B<-verify_name name>]
73 [B<-cipher cipherlist>]
107 [B<-serverinfo file>]
108 [B<-no_resumption_on_reneg>]
111 [B<-status_timeout nsec>]
113 [B<-status_file file>]
115 [B<-nextprotoneg protocols>]
121 The B<s_server> command implements a generic SSL/TLS server which listens
122 for connections on a given port using SSL/TLS.
126 In addition to the options below the B<s_server> utility also supports the
127 common and server only options documented in the
128 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
135 Print out a usage message.
139 The TCP port to listen on for connections. If not specified 4433 is used.
143 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
145 =item B<-naccept count>
147 The server will exit after receiving B<number> connections, default unlimited.
151 Unix domain socket to accept on.
155 For -unix, unlink existing socket first.
167 Sets the SSL context id. It can be given any string value. If this option
168 is not present a default value will be used.
170 =item B<-cert certname>
172 The certificate to use, most servers cipher suites require the use of a
173 certificate and some require a certificate with a certain public key type:
174 for example the DSS cipher suites require a certificate containing a DSS
175 (DSA) key. If not specified then the filename "server.pem" will be used.
177 =item B<-certform format>
179 The certificate format to use: DER or PEM. PEM is the default.
181 =item B<-key keyfile>
183 The private key to use. If not specified then the certificate file will
186 =item B<-keyform format>
188 The private format to use: DER or PEM. PEM is the default.
192 The private key password source. For more information about the format of B<arg>
193 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
195 =item B<-dcert filename>, B<-dkey keyname>
197 Specify an additional certificate and private key, these behave in the
198 same manner as the B<-cert> and B<-key> options except there is no default
199 if they are not specified (no additional certificate and key is used). As
200 noted above some cipher suites require a certificate containing a key of
201 a certain type. Some cipher suites need a certificate carrying an RSA key
202 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
203 a server can support clients which only support RSA or DSS cipher suites
204 by using an appropriate certificate.
206 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
208 Additional certificate and private key format and passphrase respectively.
212 If this option is set then no certificate is used. This restricts the
213 cipher suites available to the anonymous ones (currently just anonymous
216 =item B<-dhparam filename>
218 The DH parameter file to use. The ephemeral DH cipher suites generate keys
219 using a set of DH parameters. If not specified then an attempt is made to
220 load the parameters from the server certificate file.
221 If this fails then a static set of parameters hard coded into the B<s_server>
222 program will be used.
226 If this option is set then no DH parameters will be loaded effectively
227 disabling the ephemeral DH cipher suites.
229 =item B<-crl_check>, B<-crl_check_all>
231 Check the peer certificate has not been revoked by its CA.
232 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
233 option all CRLs of all CAs in the chain are checked.
235 =item B<-CApath directory>
237 The directory to use for client certificate verification. This directory
238 must be in "hash format", see B<verify> for more information. These are
239 also used when building the server certificate chain.
241 =item B<-CAfile file>
243 A file containing trusted certificates to use during client authentication
244 and to use when attempting to build the server certificate chain. The list
245 is also used in the list of acceptable client CAs passed to the client when
246 a certificate is requested.
250 Do not load the trusted CA certificates from the default file location
254 Do not load the trusted CA certificates from the default directory location
256 =item B<-verify depth>, B<-Verify depth>
258 The verify depth to use. This specifies the maximum length of the
259 client certificate chain and makes the server request a certificate from
260 the client. With the B<-verify> option a certificate is requested but the
261 client does not have to send one, with the B<-Verify> option the client
262 must supply a certificate or an error occurs.
264 If the ciphersuite cannot request a client certificate (for example an
265 anonymous ciphersuite or PSK) this option has no effect.
267 =item B<-nameopt option>
269 option which determines how the subject or issuer names are displayed. The
270 B<option> argument can be a single option or multiple options separated by
271 commas. Alternatively the B<-nameopt> switch may be used more than once to
272 set multiple options. See the L<x509(1)> manual page for details.
274 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
275 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
276 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
277 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
278 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
279 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
280 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
282 Set different peer certificate verification options.
283 See the L<verify(1)> manual page for details.
285 =item B<-verify_return_error>
287 Verification errors normally just print a message but allow the
288 connection to continue, for debugging purposes.
289 If this option is used, then verification errors close the connection.
293 Prints the SSL session states.
297 Print extensive debugging information including a hex dump of all traffic.
301 Show all protocol messages with hex dump.
305 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
306 with B<enable-ssl-trace> for this option to work.
310 File to send output of B<-msg> or B<-trace> to, default standard output.
314 Tests non blocking I/O
318 Turns on non blocking I/O
322 This option translated a line feed from the terminal into CR+LF.
326 Inhibit printing of session and certificate information.
328 =item B<-psk_hint hint>
330 Use the PSK identity hint B<hint> when using a PSK cipher suite.
334 Use the PSK key B<key> when using a PSK cipher suite. The key is
335 given as a hexadecimal number without leading 0x, for example -psk
338 =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>
340 These options require or disable the use of the specified SSL or TLS protocols.
341 By default B<s_server> will negotiate the highest mutually supported protocol
343 When a specific TLS version is required, only that version will be accepted
346 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
348 These options make B<s_server> use DTLS protocols instead of TLS.
349 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
350 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
355 This option can only be used in conjunction with one of the DTLS options above.
356 With this option B<s_server> will listen on a UDP port for incoming connections.
357 Any ClientHellos that arrive will be checked to see if they have a cookie in
359 Any without a cookie will be responded to with a HelloVerifyRequest.
360 If a ClientHello with a cookie is received then B<s_server> will connect to
361 that peer and complete the handshake.
365 Switch on asynchronous mode. Cryptographic operations will be performed
366 asynchronously. This will only have an effect if an asynchronous capable engine
367 is also used via the B<-engine> option. For test purposes the dummy async engine
368 (dasync) can be used (if available).
370 =item B<-split_send_frag int>
372 The size used to split data for encrypt pipelines. If more data is written in
373 one go than this value then it will be split into multiple pipelines, up to the
374 maximum number of pipelines defined by max_pipelines. This only has an effect if
375 a suitable ciphersuite has been negotiated, an engine that supports pipelining
376 has been loaded, and max_pipelines is greater than 1. See
377 L<SSL_CTX_set_split_send_fragment(3)> for further information.
379 =item B<-max_pipelines int>
381 The maximum number of encrypt/decrypt pipelines to be used. This will only have
382 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
383 engine) and a suitable ciphersuite has been negotiated. The default value is 1.
384 See L<SSL_CTX_set_max_pipelines(3)> for further information.
386 =item B<-read_buf int>
388 The default read buffer size to be used for connections. This will only have an
389 effect if the buffer size is larger than the size that would otherwise be used
390 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
391 further information).
395 There are several known bug in SSL and TLS implementations. Adding this
396 option enables various workarounds.
400 Enable negotiation of TLS compression.
401 This option was introduced in OpenSSL 1.1.0.
402 TLS compression is not recommended and is off by default as of
407 Disable negotiation of TLS compression.
408 TLS compression is not recommended and is off by default as of
413 Provide a brief summary of connection parameters instead of the normal verbose
416 =item B<-cipher cipherlist>
418 This allows the cipher list used by the server to be modified. When
419 the client sends a list of supported ciphers the first client cipher
420 also included in the server list is used. Because the client specifies
421 the preference order, the order of the server cipherlist irrelevant. See
422 the B<ciphers> command for more information.
426 Use the server's cipher preferences, rather than the client's preferences.
428 =item B<-tlsextdebug>
430 Print a hex dump of any TLS extensions received from the server.
434 Disable RFC4507bis session ticket support.
438 Sends a status message back to the client when it connects. This includes
439 information about the ciphers used and various session parameters.
440 The output is in HTML format so this option will normally be used with a
445 Emulates a simple web server. Pages will be resolved relative to the
446 current directory, for example if the URL https://myhost/page.html is
447 requested the file ./page.html will be loaded.
451 Emulates a simple web server. Pages will be resolved relative to the
452 current directory, for example if the URL https://myhost/page.html is
453 requested the file ./page.html will be loaded. The files loaded are
454 assumed to contain a complete and correct HTTP response (lines that
455 are part of the HTTP response line and headers must end with CRLF).
459 Simple test server which just reverses the text received from the client
460 and sends it back to the server. Also sets B<-brief>.
464 Specifying an engine (by its unique B<id> string) will cause B<s_server>
465 to attempt to obtain a functional reference to the specified engine,
466 thus initialising it if needed. The engine will then be set as the default
467 for all available algorithms.
469 =item B<-id_prefix arg>
471 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
472 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
473 servers, when each of which might be generating a unique range of session
474 IDs (eg. with a certain prefix).
476 =item B<-rand file(s)>
478 A file or files containing random data used to seed the random number
479 generator, or an EGD socket (see L<RAND_egd(3)>).
480 Multiple files can be specified separated by an OS-dependent character.
481 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
484 =item B<-serverinfo file>
486 A file containing one or more blocks of PEM data. Each PEM block
487 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
488 followed by "length" bytes of extension data). If the client sends
489 an empty TLS ClientHello extension matching the type, the corresponding
490 ServerHello extension will be returned.
492 =item B<-no_resumption_on_reneg>
494 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
498 Enables certificate status request support (aka OCSP stapling).
500 =item B<-status_verbose>
502 Enables certificate status request support (aka OCSP stapling) and gives
503 a verbose printout of the OCSP response.
505 =item B<-status_timeout nsec>
507 Sets the timeout for OCSP response to B<nsec> seconds.
509 =item B<-status_url url>
511 Sets a fallback responder URL to use if no responder URL is present in the
512 server certificate. Without this option an error is returned if the server
513 certificate does not contain a responder address.
515 =item B<-status_file file>
517 Overrides any OCSP responder URLs from the certificate and always provides the
518 OCSP Response stored in the file. The file must be in DER format.
520 =item B<-alpn protocols>, B<-nextprotoneg protocols>
522 these flags enable the
523 Enable the Application-Layer Protocol Negotiation or Next Protocol
524 Negotiation extension, respectively. ALPN is the IETF standard and
526 The B<protocols> list is a
527 comma-separated list of supported protocol names.
528 The list should contain most wanted protocols first.
529 Protocol names are printable ASCII strings, for example "http/1.1" or
532 =item B<-max_early_data arg>
534 Change the default maximum early data bytes that are specified for new sessions
535 and any incoming early data (when used in conjunction with the B<-early_data>
536 flag). The default value is approximately 16k. The argument must be an integer
537 greater than or equal to 0.
541 Accept early data where possible.
545 =head1 CONNECTED COMMANDS
547 If a connection request is established with an SSL client and neither the
548 B<-www> nor the B<-WWW> option has been used then normally any data received
549 from the client is displayed and any key presses will be sent to the client.
551 Certain single letter commands are also recognized which perform special
552 operations: these are listed below.
558 end the current SSL connection but still accept new connections.
562 end the current SSL connection and exit.
566 renegotiate the SSL session.
570 renegotiate the SSL session and request a client certificate.
574 send some plain text down the underlying TCP connection: this should
575 cause the client to disconnect due to a protocol violation.
579 print out some session cache status information.
581 =item B<-keylogfile path>
583 Appends TLS secrets to the specified keylog file such that external programs
584 (like Wireshark) can decrypt TLS connections.
590 B<s_server> can be used to debug SSL clients. To accept connections from
591 a web browser the command:
593 openssl s_server -accept 443 -www
595 can be used for example.
597 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
598 suites, so they cannot connect to servers which don't use a certificate
599 carrying an RSA key or a version of OpenSSL with RSA disabled.
601 Although specifying an empty list of CAs when requesting a client certificate
602 is strictly speaking a protocol violation, some SSL clients interpret this to
603 mean any CA is acceptable. This is useful for debugging purposes.
605 The session parameters can printed out using the B<sess_id> program.
609 Because this program has a lot of options and also because some of the
610 techniques used are rather old, the C source of B<s_server> is rather hard to
611 read and not a model of how things should be done.
612 A typical SSL server program would be much simpler.
614 The output of common ciphers is wrong: it just gives the list of ciphers that
615 OpenSSL recognizes and the client supports.
617 There should be a way for the B<s_server> program to print out details of any
618 unknown cipher suites a client says it supports.
623 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
627 The -no_alt_chains options was first added to OpenSSL 1.1.0.
631 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
633 Licensed under the OpenSSL license (the "License"). You may not use
634 this file except in compliance with the License. You can obtain a copy
635 in the file LICENSE in the source distribution or at
636 L<https://www.openssl.org/source/license.html>.