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>]
112 [B<-status_file file>]
114 [B<-nextprotoneg protocols>]
118 The B<s_server> command implements a generic SSL/TLS server which listens
119 for connections on a given port using SSL/TLS.
123 In addition to the options below the B<s_server> utility also supports the
124 common and server only options documented in the
125 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
132 Print out a usage message.
136 The TCP port to listen on for connections. If not specified 4433 is used.
140 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
142 =item B<-naccept count>
144 The server will exit after receiving B<number> connections, default unlimited.
148 Unix domain socket to accept on.
152 For -unix, unlink existing socket first.
164 Sets the SSL context id. It can be given any string value. If this option
165 is not present a default value will be used.
167 =item B<-cert certname>
169 The certificate to use, most servers cipher suites require the use of a
170 certificate and some require a certificate with a certain public key type:
171 for example the DSS cipher suites require a certificate containing a DSS
172 (DSA) key. If not specified then the filename "server.pem" will be used.
174 =item B<-certform format>
176 The certificate format to use: DER or PEM. PEM is the default.
178 =item B<-key keyfile>
180 The private key to use. If not specified then the certificate file will
183 =item B<-keyform format>
185 The private format to use: DER or PEM. PEM is the default.
189 The private key password source. For more information about the format of B<arg>
190 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
192 =item B<-dcert filename>, B<-dkey keyname>
194 Specify an additional certificate and private key, these behave in the
195 same manner as the B<-cert> and B<-key> options except there is no default
196 if they are not specified (no additional certificate and key is used). As
197 noted above some cipher suites require a certificate containing a key of
198 a certain type. Some cipher suites need a certificate carrying an RSA key
199 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
200 a server can support clients which only support RSA or DSS cipher suites
201 by using an appropriate certificate.
203 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
205 Additional certificate and private key format and passphrase respectively.
209 If this option is set then no certificate is used. This restricts the
210 cipher suites available to the anonymous ones (currently just anonymous
213 =item B<-dhparam filename>
215 The DH parameter file to use. The ephemeral DH cipher suites generate keys
216 using a set of DH parameters. If not specified then an attempt is made to
217 load the parameters from the server certificate file.
218 If this fails then a static set of parameters hard coded into the B<s_server>
219 program will be used.
223 If this option is set then no DH parameters will be loaded effectively
224 disabling the ephemeral DH cipher suites.
226 =item B<-crl_check>, B<-crl_check_all>
228 Check the peer certificate has not been revoked by its CA.
229 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
230 option all CRLs of all CAs in the chain are checked.
232 =item B<-CApath directory>
234 The directory to use for client certificate verification. This directory
235 must be in "hash format", see B<verify> for more information. These are
236 also used when building the server certificate chain.
238 =item B<-CAfile file>
240 A file containing trusted certificates to use during client authentication
241 and to use when attempting to build the server certificate chain. The list
242 is also used in the list of acceptable client CAs passed to the client when
243 a certificate is requested.
247 Do not load the trusted CA certificates from the default file location
251 Do not load the trusted CA certificates from the default directory location
253 =item B<-verify depth>, B<-Verify depth>
255 The verify depth to use. This specifies the maximum length of the
256 client certificate chain and makes the server request a certificate from
257 the client. With the B<-verify> option a certificate is requested but the
258 client does not have to send one, with the B<-Verify> option the client
259 must supply a certificate or an error occurs.
261 If the ciphersuite cannot request a client certificate (for example an
262 anonymous ciphersuite or PSK) this option has no effect.
264 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
265 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
266 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
267 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
268 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
269 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
270 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
272 Set different peer certificate verification options.
273 See the L<verify(1)> manual page for details.
275 =item B<-verify_return_error>
277 Verification errors normally just print a message but allow the
278 connection to continue, for debugging purposes.
279 If this option is used, then verification errors close the connection.
283 Prints the SSL session states.
287 Print extensive debugging information including a hex dump of all traffic.
291 Show all protocol messages with hex dump.
295 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
296 with B<enable-ssl-trace> for this option to work.
300 File to send output of B<-msg> or B<-trace> to, default standard output.
304 Tests non blocking I/O
308 Turns on non blocking I/O
312 This option translated a line feed from the terminal into CR+LF.
316 Inhibit printing of session and certificate information.
318 =item B<-psk_hint hint>
320 Use the PSK identity hint B<hint> when using a PSK cipher suite.
324 Use the PSK key B<key> when using a PSK cipher suite. The key is
325 given as a hexadecimal number without leading 0x, for example -psk
328 =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>
330 These options require or disable the use of the specified SSL or TLS protocols.
331 By default B<s_server> will negotiate the highest mutually supported protocol
333 When a specific TLS version is required, only that version will be accepted
336 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
338 These options make B<s_server> use DTLS protocols instead of TLS.
339 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
340 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
345 This option can only be used in conjunction with one of the DTLS options above.
346 With this option B<s_server> will listen on a UDP port for incoming connections.
347 Any ClientHellos that arrive will be checked to see if they have a cookie in
349 Any without a cookie will be responded to with a HelloVerifyRequest.
350 If a ClientHello with a cookie is received then B<s_server> will connect to
351 that peer and complete the handshake.
355 Switch on asynchronous mode. Cryptographic operations will be performed
356 asynchronously. This will only have an effect if an asynchronous capable engine
357 is also used via the B<-engine> option. For test purposes the dummy async engine
358 (dasync) can be used (if available).
360 =item B<-split_send_frag int>
362 The size used to split data for encrypt pipelines. If more data is written in
363 one go than this value then it will be split into multiple pipelines, up to the
364 maximum number of pipelines defined by max_pipelines. This only has an effect if
365 a suitable ciphersuite has been negotiated, an engine that supports pipelining
366 has been loaded, and max_pipelines is greater than 1. See
367 L<SSL_CTX_set_split_send_fragment(3)> for further information.
369 =item B<-max_pipelines int>
371 The maximum number of encrypt/decrypt pipelines to be used. This will only have
372 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
373 engine) and a suitable ciphersuite has been negotiated. The default value is 1.
374 See L<SSL_CTX_set_max_pipelines(3)> for further information.
376 =item B<-read_buf int>
378 The default read buffer size to be used for connections. This will only have an
379 effect if the buffer size is larger than the size that would otherwise be used
380 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
381 further information).
385 There are several known bug in SSL and TLS implementations. Adding this
386 option enables various workarounds.
390 Enable negotiation of TLS compression.
391 This option was introduced in OpenSSL 1.1.0.
392 TLS compression is not recommended and is off by default as of
397 Disable negotiation of TLS compression.
398 TLS compression is not recommended and is off by default as of
403 Provide a brief summary of connection parameters instead of the normal verbose
406 =item B<-cipher cipherlist>
408 This allows the cipher list used by the server to be modified. When
409 the client sends a list of supported ciphers the first client cipher
410 also included in the server list is used. Because the client specifies
411 the preference order, the order of the server cipherlist irrelevant. See
412 the B<ciphers> command for more information.
416 Use the server's cipher preferences, rather than the client's preferences.
418 =item B<-tlsextdebug>
420 Print a hex dump of any TLS extensions received from the server.
424 Disable RFC4507bis session ticket support.
428 Sends a status message back to the client when it connects. This includes
429 information about the ciphers used and various session parameters.
430 The output is in HTML format so this option will normally be used with a
435 Emulates a simple web server. Pages will be resolved relative to the
436 current directory, for example if the URL https://myhost/page.html is
437 requested the file ./page.html will be loaded.
441 Emulates a simple web server. Pages will be resolved relative to the
442 current directory, for example if the URL https://myhost/page.html is
443 requested the file ./page.html will be loaded. The files loaded are
444 assumed to contain a complete and correct HTTP response (lines that
445 are part of the HTTP response line and headers must end with CRLF).
449 Simple test server which just reverses the text received from the client
450 and sends it back to the server. Also sets B<-brief>.
454 Specifying an engine (by its unique B<id> string) will cause B<s_server>
455 to attempt to obtain a functional reference to the specified engine,
456 thus initialising it if needed. The engine will then be set as the default
457 for all available algorithms.
459 =item B<-id_prefix arg>
461 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
462 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
463 servers, when each of which might be generating a unique range of session
464 IDs (eg. with a certain prefix).
466 =item B<-rand file(s)>
468 A file or files containing random data used to seed the random number
469 generator, or an EGD socket (see L<RAND_egd(3)>).
470 Multiple files can be specified separated by an OS-dependent character.
471 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
474 =item B<-serverinfo file>
476 A file containing one or more blocks of PEM data. Each PEM block
477 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
478 followed by "length" bytes of extension data). If the client sends
479 an empty TLS ClientHello extension matching the type, the corresponding
480 ServerHello extension will be returned.
482 =item B<-no_resumption_on_reneg>
484 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
488 Enables certificate status request support (aka OCSP stapling).
490 =item B<-status_verbose>
492 Enables certificate status request support (aka OCSP stapling) and gives
493 a verbose printout of the OCSP response.
495 =item B<-status_timeout nsec>
497 Sets the timeout for OCSP response to B<nsec> seconds.
499 =item B<-status_url url>
501 Sets a fallback responder URL to use if no responder URL is present in the
502 server certificate. Without this option an error is returned if the server
503 certificate does not contain a responder address.
505 =item B<-status_file file>
507 Overrides any OCSP responder URLs from the certificate and always provides the
508 OCSP Response stored in the file. The file must be in DER format.
510 =item B<-alpn protocols>, B<-nextprotoneg protocols>
512 these flags enable the
513 Enable the Application-Layer Protocol Negotiation or Next Protocol
514 Negotiation extension, respectively. ALPN is the IETF standard and
516 The B<protocols> list is a
517 comma-separated list of supported protocol names.
518 The list should contain most wanted protocols first.
519 Protocol names are printable ASCII strings, for example "http/1.1" or
524 =head1 CONNECTED COMMANDS
526 If a connection request is established with an SSL client and neither the
527 B<-www> nor the B<-WWW> option has been used then normally any data received
528 from the client is displayed and any key presses will be sent to the client.
530 Certain single letter commands are also recognized which perform special
531 operations: these are listed below.
537 end the current SSL connection but still accept new connections.
541 end the current SSL connection and exit.
545 renegotiate the SSL session.
549 renegotiate the SSL session and request a client certificate.
553 send some plain text down the underlying TCP connection: this should
554 cause the client to disconnect due to a protocol violation.
558 print out some session cache status information.
560 =item B<-keylogfile path>
562 Appends TLS secrets to the specified keylog file such that external programs
563 (like Wireshark) can decrypt TLS connections.
569 B<s_server> can be used to debug SSL clients. To accept connections from
570 a web browser the command:
572 openssl s_server -accept 443 -www
574 can be used for example.
576 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
577 suites, so they cannot connect to servers which don't use a certificate
578 carrying an RSA key or a version of OpenSSL with RSA disabled.
580 Although specifying an empty list of CAs when requesting a client certificate
581 is strictly speaking a protocol violation, some SSL clients interpret this to
582 mean any CA is acceptable. This is useful for debugging purposes.
584 The session parameters can printed out using the B<sess_id> program.
588 Because this program has a lot of options and also because some of the
589 techniques used are rather old, the C source of B<s_server> is rather hard to
590 read and not a model of how things should be done.
591 A typical SSL server program would be much simpler.
593 The output of common ciphers is wrong: it just gives the list of ciphers that
594 OpenSSL recognizes and the client supports.
596 There should be a way for the B<s_server> program to print out details of any
597 unknown cipher suites a client says it supports.
602 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
606 The -no_alt_chains options was first added to OpenSSL 1.1.0.
610 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
612 Licensed under the OpenSSL license (the "License"). You may not use
613 this file except in compliance with the License. You can obtain a copy
614 in the file LICENSE in the source distribution or at
615 L<https://www.openssl.org/source/license.html>.