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>]
111 [B<-serverinfo file>]
112 [B<-no_resumption_on_reneg>]
115 [B<-status_timeout nsec>]
117 [B<-status_file file>]
119 [B<-nextprotoneg protocols>]
125 The B<s_server> command implements a generic SSL/TLS server which listens
126 for connections on a given port using SSL/TLS.
130 In addition to the options below the B<s_server> utility also supports the
131 common and server only options documented in the
132 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
139 Print out a usage message.
143 The TCP port to listen on for connections. If not specified 4433 is used.
147 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
149 =item B<-naccept count>
151 The server will exit after receiving B<number> connections, default unlimited.
155 Unix domain socket to accept on.
159 For -unix, unlink existing socket first.
171 Sets the SSL context id. It can be given any string value. If this option
172 is not present a default value will be used.
174 =item B<-cert certname>
176 The certificate to use, most servers cipher suites require the use of a
177 certificate and some require a certificate with a certain public key type:
178 for example the DSS cipher suites require a certificate containing a DSS
179 (DSA) key. If not specified then the filename "server.pem" will be used.
181 =item B<-certform format>
183 The certificate format to use: DER or PEM. PEM is the default.
185 =item B<-key keyfile>
187 The private key to use. If not specified then the certificate file will
190 =item B<-keyform format>
192 The private format to use: DER or PEM. PEM is the default.
196 The private key password source. For more information about the format of B<arg>
197 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
199 =item B<-dcert filename>, B<-dkey keyname>
201 Specify an additional certificate and private key, these behave in the
202 same manner as the B<-cert> and B<-key> options except there is no default
203 if they are not specified (no additional certificate and key is used). As
204 noted above some cipher suites require a certificate containing a key of
205 a certain type. Some cipher suites need a certificate carrying an RSA key
206 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
207 a server can support clients which only support RSA or DSS cipher suites
208 by using an appropriate certificate.
210 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
212 Additional certificate and private key format and passphrase respectively.
216 If this option is set then no certificate is used. This restricts the
217 cipher suites available to the anonymous ones (currently just anonymous
220 =item B<-dhparam filename>
222 The DH parameter file to use. The ephemeral DH cipher suites generate keys
223 using a set of DH parameters. If not specified then an attempt is made to
224 load the parameters from the server certificate file.
225 If this fails then a static set of parameters hard coded into the B<s_server>
226 program will be used.
230 If this option is set then no DH parameters will be loaded effectively
231 disabling the ephemeral DH cipher suites.
233 =item B<-crl_check>, B<-crl_check_all>
235 Check the peer certificate has not been revoked by its CA.
236 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
237 option all CRLs of all CAs in the chain are checked.
239 =item B<-CApath directory>
241 The directory to use for client certificate verification. This directory
242 must be in "hash format", see B<verify> for more information. These are
243 also used when building the server certificate chain.
245 =item B<-CAfile file>
247 A file containing trusted certificates to use during client authentication
248 and to use when attempting to build the server certificate chain. The list
249 is also used in the list of acceptable client CAs passed to the client when
250 a certificate is requested.
254 Do not load the trusted CA certificates from the default file location.
258 Do not load the trusted CA certificates from the default directory location.
260 =item B<-verify depth>, B<-Verify depth>
262 The verify depth to use. This specifies the maximum length of the
263 client certificate chain and makes the server request a certificate from
264 the client. With the B<-verify> option a certificate is requested but the
265 client does not have to send one, with the B<-Verify> option the client
266 must supply a certificate or an error occurs.
268 If the cipher suite cannot request a client certificate (for example an
269 anonymous cipher suite or PSK) this option has no effect.
271 =item B<-nameopt option>
273 Option which determines how the subject or issuer names are displayed. The
274 B<option> argument can be a single option or multiple options separated by
275 commas. Alternatively the B<-nameopt> switch may be used more than once to
276 set multiple options. See the L<x509(1)> manual page for details.
278 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
279 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
280 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
281 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
282 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
283 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
284 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
286 Set different peer certificate verification options.
287 See the L<verify(1)> manual page for details.
289 =item B<-verify_return_error>
291 Verification errors normally just print a message but allow the
292 connection to continue, for debugging purposes.
293 If this option is used, then verification errors close the connection.
297 Prints the SSL session states.
301 Print extensive debugging information including a hex dump of all traffic.
305 Show all protocol messages with hex dump.
309 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
310 with B<enable-ssl-trace> for this option to work.
314 File to send output of B<-msg> or B<-trace> to, default standard output.
318 Tests non blocking I/O.
322 Turns on non blocking I/O.
326 This option translated a line feed from the terminal into CR+LF.
330 Inhibit printing of session and certificate information.
332 =item B<-psk_hint hint>
334 Use the PSK identity hint B<hint> when using a PSK cipher suite.
336 =item B<-psk_identity identity>
338 Expect the client to send PSK identity B<identity> when using a PSK
339 cipher suite, and warn if they do not. By default, the expected PSK
340 identity is the string "Client_identity".
344 Use the PSK key B<key> when using a PSK cipher suite. The key is
345 given as a hexadecimal number without leading 0x, for example -psk
348 =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>
350 These options require or disable the use of the specified SSL or TLS protocols.
351 By default B<s_server> will negotiate the highest mutually supported protocol
353 When a specific TLS version is required, only that version will be accepted
356 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
358 These options make B<s_server> use DTLS protocols instead of TLS.
359 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
360 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
365 This option can only be used in conjunction with one of the DTLS options above.
366 With this option B<s_server> will listen on a UDP port for incoming connections.
367 Any ClientHellos that arrive will be checked to see if they have a cookie in
369 Any without a cookie will be responded to with a HelloVerifyRequest.
370 If a ClientHello with a cookie is received then B<s_server> will connect to
371 that peer and complete the handshake.
375 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
376 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
377 available where OpenSSL has support for SCTP enabled.
381 Switch on asynchronous mode. Cryptographic operations will be performed
382 asynchronously. This will only have an effect if an asynchronous capable engine
383 is also used via the B<-engine> option. For test purposes the dummy async engine
384 (dasync) can be used (if available).
386 =item B<-max_send_frag int>
388 The maximum size of data fragment to send.
389 See L<SSL_CTX_set_max_send_fragment(3)> for further information.
391 =item B<-split_send_frag int>
393 The size used to split data for encrypt pipelines. If more data is written in
394 one go than this value then it will be split into multiple pipelines, up to the
395 maximum number of pipelines defined by max_pipelines. This only has an effect if
396 a suitable cipher suite has been negotiated, an engine that supports pipelining
397 has been loaded, and max_pipelines is greater than 1. See
398 L<SSL_CTX_set_split_send_fragment(3)> for further information.
400 =item B<-max_pipelines int>
402 The maximum number of encrypt/decrypt pipelines to be used. This will only have
403 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
404 engine) and a suitable cipher suite has been negotiated. The default value is 1.
405 See L<SSL_CTX_set_max_pipelines(3)> for further information.
407 =item B<-read_buf int>
409 The default read buffer size to be used for connections. This will only have an
410 effect if the buffer size is larger than the size that would otherwise be used
411 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
412 further information).
416 There are several known bug in SSL and TLS implementations. Adding this
417 option enables various workarounds.
421 Enable negotiation of TLS compression.
422 This option was introduced in OpenSSL 1.1.0.
423 TLS compression is not recommended and is off by default as of
428 Disable negotiation of TLS compression.
429 TLS compression is not recommended and is off by default as of
434 Provide a brief summary of connection parameters instead of the normal verbose
437 =item B<-client_sigalgs sigalglist>
439 Signature algorithms to support for client certificate authentication
440 (colon-separated list).
442 =item B<-named_curve curve>
444 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
445 For a list of all possible curves, use:
447 $ openssl ecparam -list_curves
449 =item B<-cipher cipherlist>
451 This allows the cipher list used by the server to be modified. When
452 the client sends a list of supported ciphers the first client cipher
453 also included in the server list is used. Because the client specifies
454 the preference order, the order of the server cipherlist irrelevant. See
455 the B<ciphers> command for more information.
459 Use the server's cipher preferences, rather than the client's preferences.
461 =item B<-tlsextdebug>
463 Print a hex dump of any TLS extensions received from the server.
467 Disable RFC4507bis session ticket support.
471 Sends a status message back to the client when it connects. This includes
472 information about the ciphers used and various session parameters.
473 The output is in HTML format so this option will normally be used with a
478 Emulates a simple web server. Pages will be resolved relative to the
479 current directory, for example if the URL https://myhost/page.html is
480 requested the file ./page.html will be loaded.
484 Emulates a simple web server. Pages will be resolved relative to the
485 current directory, for example if the URL https://myhost/page.html is
486 requested the file ./page.html will be loaded. The files loaded are
487 assumed to contain a complete and correct HTTP response (lines that
488 are part of the HTTP response line and headers must end with CRLF).
492 Simple test server which just reverses the text received from the client
493 and sends it back to the server. Also sets B<-brief>.
497 Specifying an engine (by its unique B<id> string) will cause B<s_server>
498 to attempt to obtain a functional reference to the specified engine,
499 thus initialising it if needed. The engine will then be set as the default
500 for all available algorithms.
502 =item B<-id_prefix arg>
504 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
505 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
506 servers, when each of which might be generating a unique range of session
507 IDs (eg. with a certain prefix).
509 =item B<-rand file(s)>
511 A file or files containing random data used to seed the random number
512 generator, or an EGD socket (see L<RAND_egd(3)>).
513 Multiple files can be specified separated by an OS-dependent character.
514 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
517 =item B<-serverinfo file>
519 A file containing one or more blocks of PEM data. Each PEM block
520 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
521 followed by "length" bytes of extension data). If the client sends
522 an empty TLS ClientHello extension matching the type, the corresponding
523 ServerHello extension will be returned.
525 =item B<-no_resumption_on_reneg>
527 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
531 Enables certificate status request support (aka OCSP stapling).
533 =item B<-status_verbose>
535 Enables certificate status request support (aka OCSP stapling) and gives
536 a verbose printout of the OCSP response.
538 =item B<-status_timeout nsec>
540 Sets the timeout for OCSP response to B<nsec> seconds.
542 =item B<-status_url url>
544 Sets a fallback responder URL to use if no responder URL is present in the
545 server certificate. Without this option an error is returned if the server
546 certificate does not contain a responder address.
548 =item B<-status_file file>
550 Overrides any OCSP responder URLs from the certificate and always provides the
551 OCSP Response stored in the file. The file must be in DER format.
553 =item B<-alpn protocols>, B<-nextprotoneg protocols>
555 These flags enable the Enable the Application-Layer Protocol Negotiation
556 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
557 IETF standard and replaces NPN.
558 The B<protocols> list is a comma-separated list of supported protocol
559 names. The list should contain the most desirable protocols first.
560 Protocol names are printable ASCII strings, for example "http/1.1" or
563 =item B<-keylogfile path>
565 Appends TLS secrets to the specified keylog file such that external programs
566 (like Wireshark) can decrypt TLS connections.
568 =item B<-max_early_data arg>
570 Change the default maximum early data bytes that are specified for new sessions
571 and any incoming early data (when used in conjunction with the B<-early_data>
572 flag). The default value is approximately 16k. The argument must be an integer
573 greater than or equal to 0.
577 Accept early data where possible.
581 =head1 CONNECTED COMMANDS
583 If a connection request is established with an SSL client and neither the
584 B<-www> nor the B<-WWW> option has been used then normally any data received
585 from the client is displayed and any key presses will be sent to the client.
587 Certain single letter commands are also recognized which perform special
588 operations: these are listed below.
594 End the current SSL connection but still accept new connections.
598 End the current SSL connection and exit.
602 Renegotiate the SSL session.
606 Renegotiate the SSL session and request a client certificate.
610 Send some plain text down the underlying TCP connection: this should
611 cause the client to disconnect due to a protocol violation.
615 Print out some session cache status information.
621 B<s_server> can be used to debug SSL clients. To accept connections from
622 a web browser the command:
624 openssl s_server -accept 443 -www
626 can be used for example.
628 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
629 suites, so they cannot connect to servers which don't use a certificate
630 carrying an RSA key or a version of OpenSSL with RSA disabled.
632 Although specifying an empty list of CAs when requesting a client certificate
633 is strictly speaking a protocol violation, some SSL clients interpret this to
634 mean any CA is acceptable. This is useful for debugging purposes.
636 The session parameters can printed out using the B<sess_id> program.
640 Because this program has a lot of options and also because some of the
641 techniques used are rather old, the C source of B<s_server> is rather hard to
642 read and not a model of how things should be done.
643 A typical SSL server program would be much simpler.
645 The output of common ciphers is wrong: it just gives the list of ciphers that
646 OpenSSL recognizes and the client supports.
648 There should be a way for the B<s_server> program to print out details of any
649 unknown cipher suites a client says it supports.
653 L<SSL_CONF_cmd(3)>, L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
654 L<SSL_CTX_set_max_send_fragment(3)>, L<SSL_CTX_set_split_send_fragment(3)>
655 L<SSL_CTX_set_max_pipelines(3)>
659 The -no_alt_chains options was first added to OpenSSL 1.1.0.
663 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
665 Licensed under the OpenSSL license (the "License"). You may not use
666 this file except in compliance with the License. You can obtain a copy
667 in the file LICENSE in the source distribution or at
668 L<https://www.openssl.org/source/license.html>.