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<-client_sigalgs sigalglist>]
74 [B<-named_curve curve>]
75 [B<-cipher cipherlist>]
109 [B<-serverinfo file>]
110 [B<-no_resumption_on_reneg>]
113 [B<-status_timeout nsec>]
115 [B<-status_file file>]
117 [B<-nextprotoneg protocols>]
123 The B<s_server> command implements a generic SSL/TLS server which listens
124 for connections on a given port using SSL/TLS.
128 In addition to the options below the B<s_server> utility also supports the
129 common and server only options documented in the
130 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
137 Print out a usage message.
141 The TCP port to listen on for connections. If not specified 4433 is used.
145 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
147 =item B<-naccept count>
149 The server will exit after receiving B<number> connections, default unlimited.
153 Unix domain socket to accept on.
157 For -unix, unlink existing socket first.
169 Sets the SSL context id. It can be given any string value. If this option
170 is not present a default value will be used.
172 =item B<-cert certname>
174 The certificate to use, most servers cipher suites require the use of a
175 certificate and some require a certificate with a certain public key type:
176 for example the DSS cipher suites require a certificate containing a DSS
177 (DSA) key. If not specified then the filename "server.pem" will be used.
179 =item B<-certform format>
181 The certificate format to use: DER or PEM. PEM is the default.
183 =item B<-key keyfile>
185 The private key to use. If not specified then the certificate file will
188 =item B<-keyform format>
190 The private format to use: DER or PEM. PEM is the default.
194 The private key password source. For more information about the format of B<arg>
195 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
197 =item B<-dcert filename>, B<-dkey keyname>
199 Specify an additional certificate and private key, these behave in the
200 same manner as the B<-cert> and B<-key> options except there is no default
201 if they are not specified (no additional certificate and key is used). As
202 noted above some cipher suites require a certificate containing a key of
203 a certain type. Some cipher suites need a certificate carrying an RSA key
204 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
205 a server can support clients which only support RSA or DSS cipher suites
206 by using an appropriate certificate.
208 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
210 Additional certificate and private key format and passphrase respectively.
214 If this option is set then no certificate is used. This restricts the
215 cipher suites available to the anonymous ones (currently just anonymous
218 =item B<-dhparam filename>
220 The DH parameter file to use. The ephemeral DH cipher suites generate keys
221 using a set of DH parameters. If not specified then an attempt is made to
222 load the parameters from the server certificate file.
223 If this fails then a static set of parameters hard coded into the B<s_server>
224 program will be used.
228 If this option is set then no DH parameters will be loaded effectively
229 disabling the ephemeral DH cipher suites.
231 =item B<-crl_check>, B<-crl_check_all>
233 Check the peer certificate has not been revoked by its CA.
234 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
235 option all CRLs of all CAs in the chain are checked.
237 =item B<-CApath directory>
239 The directory to use for client certificate verification. This directory
240 must be in "hash format", see B<verify> for more information. These are
241 also used when building the server certificate chain.
243 =item B<-CAfile file>
245 A file containing trusted certificates to use during client authentication
246 and to use when attempting to build the server certificate chain. The list
247 is also used in the list of acceptable client CAs passed to the client when
248 a certificate is requested.
252 Do not load the trusted CA certificates from the default file location.
256 Do not load the trusted CA certificates from the default directory location.
258 =item B<-verify depth>, B<-Verify depth>
260 The verify depth to use. This specifies the maximum length of the
261 client certificate chain and makes the server request a certificate from
262 the client. With the B<-verify> option a certificate is requested but the
263 client does not have to send one, with the B<-Verify> option the client
264 must supply a certificate or an error occurs.
266 If the cipher suite cannot request a client certificate (for example an
267 anonymous cipher suite or PSK) this option has no effect.
269 =item B<-nameopt option>
271 Option which determines how the subject or issuer names are displayed. The
272 B<option> argument can be a single option or multiple options separated by
273 commas. Alternatively the B<-nameopt> switch may be used more than once to
274 set multiple options. See the L<x509(1)> manual page for details.
276 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
277 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
278 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
279 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
280 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
281 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
282 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
284 Set different peer certificate verification options.
285 See the L<verify(1)> manual page for details.
287 =item B<-verify_return_error>
289 Verification errors normally just print a message but allow the
290 connection to continue, for debugging purposes.
291 If this option is used, then verification errors close the connection.
295 Prints the SSL session states.
299 Print extensive debugging information including a hex dump of all traffic.
303 Show all protocol messages with hex dump.
307 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
308 with B<enable-ssl-trace> for this option to work.
312 File to send output of B<-msg> or B<-trace> to, default standard output.
316 Tests non blocking I/O.
320 Turns on non blocking I/O.
324 This option translated a line feed from the terminal into CR+LF.
328 Inhibit printing of session and certificate information.
330 =item B<-psk_hint hint>
332 Use the PSK identity hint B<hint> when using a PSK cipher suite.
336 Use the PSK key B<key> when using a PSK cipher suite. The key is
337 given as a hexadecimal number without leading 0x, for example -psk
340 =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>
342 These options require or disable the use of the specified SSL or TLS protocols.
343 By default B<s_server> will negotiate the highest mutually supported protocol
345 When a specific TLS version is required, only that version will be accepted
348 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
350 These options make B<s_server> use DTLS protocols instead of TLS.
351 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
352 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
357 This option can only be used in conjunction with one of the DTLS options above.
358 With this option B<s_server> will listen on a UDP port for incoming connections.
359 Any ClientHellos that arrive will be checked to see if they have a cookie in
361 Any without a cookie will be responded to with a HelloVerifyRequest.
362 If a ClientHello with a cookie is received then B<s_server> will connect to
363 that peer and complete the handshake.
367 Switch on asynchronous mode. Cryptographic operations will be performed
368 asynchronously. This will only have an effect if an asynchronous capable engine
369 is also used via the B<-engine> option. For test purposes the dummy async engine
370 (dasync) can be used (if available).
372 =item B<-split_send_frag int>
374 The size used to split data for encrypt pipelines. If more data is written in
375 one go than this value then it will be split into multiple pipelines, up to the
376 maximum number of pipelines defined by max_pipelines. This only has an effect if
377 a suitable cipher suite has been negotiated, an engine that supports pipelining
378 has been loaded, and max_pipelines is greater than 1. See
379 L<SSL_CTX_set_split_send_fragment(3)> for further information.
381 =item B<-max_pipelines int>
383 The maximum number of encrypt/decrypt pipelines to be used. This will only have
384 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
385 engine) and a suitable cipher suite has been negotiated. The default value is 1.
386 See L<SSL_CTX_set_max_pipelines(3)> for further information.
388 =item B<-read_buf int>
390 The default read buffer size to be used for connections. This will only have an
391 effect if the buffer size is larger than the size that would otherwise be used
392 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
393 further information).
397 There are several known bug in SSL and TLS implementations. Adding this
398 option enables various workarounds.
402 Enable negotiation of TLS compression.
403 This option was introduced in OpenSSL 1.1.0.
404 TLS compression is not recommended and is off by default as of
409 Disable negotiation of TLS compression.
410 TLS compression is not recommended and is off by default as of
415 Provide a brief summary of connection parameters instead of the normal verbose
418 =item B<-client_sigalgs sigalglist>
420 Signature algorithms to support for client certificate authentication
421 (colon-separated list).
423 =item B<-named_curve curve>
425 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
426 For a list of all possible curves, use:
428 $ openssl ecparam -list_curves
430 =item B<-cipher cipherlist>
432 This allows the cipher list used by the server to be modified. When
433 the client sends a list of supported ciphers the first client cipher
434 also included in the server list is used. Because the client specifies
435 the preference order, the order of the server cipherlist irrelevant. See
436 the B<ciphers> command for more information.
440 Use the server's cipher preferences, rather than the client's preferences.
442 =item B<-tlsextdebug>
444 Print a hex dump of any TLS extensions received from the server.
448 Disable RFC4507bis session ticket support.
452 Sends a status message back to the client when it connects. This includes
453 information about the ciphers used and various session parameters.
454 The output is in HTML format so this option will normally be used with a
459 Emulates a simple web server. Pages will be resolved relative to the
460 current directory, for example if the URL https://myhost/page.html is
461 requested the file ./page.html will be loaded.
465 Emulates a simple web server. Pages will be resolved relative to the
466 current directory, for example if the URL https://myhost/page.html is
467 requested the file ./page.html will be loaded. The files loaded are
468 assumed to contain a complete and correct HTTP response (lines that
469 are part of the HTTP response line and headers must end with CRLF).
473 Simple test server which just reverses the text received from the client
474 and sends it back to the server. Also sets B<-brief>.
478 Specifying an engine (by its unique B<id> string) will cause B<s_server>
479 to attempt to obtain a functional reference to the specified engine,
480 thus initialising it if needed. The engine will then be set as the default
481 for all available algorithms.
483 =item B<-id_prefix arg>
485 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
486 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
487 servers, when each of which might be generating a unique range of session
488 IDs (eg. with a certain prefix).
490 =item B<-rand file(s)>
492 A file or files containing random data used to seed the random number
493 generator, or an EGD socket (see L<RAND_egd(3)>).
494 Multiple files can be specified separated by an OS-dependent character.
495 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
498 =item B<-serverinfo file>
500 A file containing one or more blocks of PEM data. Each PEM block
501 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
502 followed by "length" bytes of extension data). If the client sends
503 an empty TLS ClientHello extension matching the type, the corresponding
504 ServerHello extension will be returned.
506 =item B<-no_resumption_on_reneg>
508 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
512 Enables certificate status request support (aka OCSP stapling).
514 =item B<-status_verbose>
516 Enables certificate status request support (aka OCSP stapling) and gives
517 a verbose printout of the OCSP response.
519 =item B<-status_timeout nsec>
521 Sets the timeout for OCSP response to B<nsec> seconds.
523 =item B<-status_url url>
525 Sets a fallback responder URL to use if no responder URL is present in the
526 server certificate. Without this option an error is returned if the server
527 certificate does not contain a responder address.
529 =item B<-status_file file>
531 Overrides any OCSP responder URLs from the certificate and always provides the
532 OCSP Response stored in the file. The file must be in DER format.
534 =item B<-alpn protocols>, B<-nextprotoneg protocols>
536 These flags enable the Enable the Application-Layer Protocol Negotiation
537 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
538 IETF standard and replaces NPN.
539 The B<protocols> list is a comma-separated list of supported protocol
540 names. The list should contain the most desirable protocols first.
541 Protocol names are printable ASCII strings, for example "http/1.1" or
544 =item B<-keylogfile path>
546 Appends TLS secrets to the specified keylog file such that external programs
547 (like Wireshark) can decrypt TLS connections.
549 =item B<-max_early_data arg>
551 Change the default maximum early data bytes that are specified for new sessions
552 and any incoming early data (when used in conjunction with the B<-early_data>
553 flag). The default value is approximately 16k. The argument must be an integer
554 greater than or equal to 0.
558 Accept early data where possible.
562 =head1 CONNECTED COMMANDS
564 If a connection request is established with an SSL client and neither the
565 B<-www> nor the B<-WWW> option has been used then normally any data received
566 from the client is displayed and any key presses will be sent to the client.
568 Certain single letter commands are also recognized which perform special
569 operations: these are listed below.
575 End the current SSL connection but still accept new connections.
579 End the current SSL connection and exit.
583 Renegotiate the SSL session.
587 Renegotiate the SSL session and request a client certificate.
591 Send some plain text down the underlying TCP connection: this should
592 cause the client to disconnect due to a protocol violation.
596 Print out some session cache status information.
602 B<s_server> can be used to debug SSL clients. To accept connections from
603 a web browser the command:
605 openssl s_server -accept 443 -www
607 can be used for example.
609 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
610 suites, so they cannot connect to servers which don't use a certificate
611 carrying an RSA key or a version of OpenSSL with RSA disabled.
613 Although specifying an empty list of CAs when requesting a client certificate
614 is strictly speaking a protocol violation, some SSL clients interpret this to
615 mean any CA is acceptable. This is useful for debugging purposes.
617 The session parameters can printed out using the B<sess_id> program.
621 Because this program has a lot of options and also because some of the
622 techniques used are rather old, the C source of B<s_server> is rather hard to
623 read and not a model of how things should be done.
624 A typical SSL server program would be much simpler.
626 The output of common ciphers is wrong: it just gives the list of ciphers that
627 OpenSSL recognizes and the client supports.
629 There should be a way for the B<s_server> program to print out details of any
630 unknown cipher suites a client says it supports.
635 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
639 The -no_alt_chains options was first added to OpenSSL 1.1.0.
643 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
645 Licensed under the OpenSSL license (the "License"). You may not use
646 this file except in compliance with the License. You can obtain a copy
647 in the file LICENSE in the source distribution or at
648 L<https://www.openssl.org/source/license.html>.