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.
338 Use the PSK key B<key> when using a PSK cipher suite. The key is
339 given as a hexadecimal number without leading 0x, for example -psk
342 =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>
344 These options require or disable the use of the specified SSL or TLS protocols.
345 By default B<s_server> will negotiate the highest mutually supported protocol
347 When a specific TLS version is required, only that version will be accepted
350 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
352 These options make B<s_server> use DTLS protocols instead of TLS.
353 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
354 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
359 This option can only be used in conjunction with one of the DTLS options above.
360 With this option B<s_server> will listen on a UDP port for incoming connections.
361 Any ClientHellos that arrive will be checked to see if they have a cookie in
363 Any without a cookie will be responded to with a HelloVerifyRequest.
364 If a ClientHello with a cookie is received then B<s_server> will connect to
365 that peer and complete the handshake.
369 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
370 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
371 available where OpenSSL has support for SCTP enabled.
375 Switch on asynchronous mode. Cryptographic operations will be performed
376 asynchronously. This will only have an effect if an asynchronous capable engine
377 is also used via the B<-engine> option. For test purposes the dummy async engine
378 (dasync) can be used (if available).
380 =item B<-max_send_frag int>
382 The maximum size of data fragment to send.
383 See L<SSL_CTX_set_max_send_fragment(3)> for further information.
385 =item B<-split_send_frag int>
387 The size used to split data for encrypt pipelines. If more data is written in
388 one go than this value then it will be split into multiple pipelines, up to the
389 maximum number of pipelines defined by max_pipelines. This only has an effect if
390 a suitable cipher suite has been negotiated, an engine that supports pipelining
391 has been loaded, and max_pipelines is greater than 1. See
392 L<SSL_CTX_set_split_send_fragment(3)> for further information.
394 =item B<-max_pipelines int>
396 The maximum number of encrypt/decrypt pipelines to be used. This will only have
397 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
398 engine) and a suitable cipher suite has been negotiated. The default value is 1.
399 See L<SSL_CTX_set_max_pipelines(3)> for further information.
401 =item B<-read_buf int>
403 The default read buffer size to be used for connections. This will only have an
404 effect if the buffer size is larger than the size that would otherwise be used
405 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
406 further information).
410 There are several known bug in SSL and TLS implementations. Adding this
411 option enables various workarounds.
415 Enable negotiation of TLS compression.
416 This option was introduced in OpenSSL 1.1.0.
417 TLS compression is not recommended and is off by default as of
422 Disable negotiation of TLS compression.
423 TLS compression is not recommended and is off by default as of
428 Provide a brief summary of connection parameters instead of the normal verbose
431 =item B<-client_sigalgs sigalglist>
433 Signature algorithms to support for client certificate authentication
434 (colon-separated list).
436 =item B<-named_curve curve>
438 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
439 For a list of all possible curves, use:
441 $ openssl ecparam -list_curves
443 =item B<-cipher cipherlist>
445 This allows the cipher list used by the server to be modified. When
446 the client sends a list of supported ciphers the first client cipher
447 also included in the server list is used. Because the client specifies
448 the preference order, the order of the server cipherlist irrelevant. See
449 the B<ciphers> command for more information.
453 Use the server's cipher preferences, rather than the client's preferences.
455 =item B<-tlsextdebug>
457 Print a hex dump of any TLS extensions received from the server.
461 Disable RFC4507bis session ticket support.
465 Sends a status message back to the client when it connects. This includes
466 information about the ciphers used and various session parameters.
467 The output is in HTML format so this option will normally be used with a
472 Emulates a simple web server. Pages will be resolved relative to the
473 current directory, for example if the URL https://myhost/page.html is
474 requested the file ./page.html will be loaded.
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. The files loaded are
481 assumed to contain a complete and correct HTTP response (lines that
482 are part of the HTTP response line and headers must end with CRLF).
486 Simple test server which just reverses the text received from the client
487 and sends it back to the server. Also sets B<-brief>.
491 Specifying an engine (by its unique B<id> string) will cause B<s_server>
492 to attempt to obtain a functional reference to the specified engine,
493 thus initialising it if needed. The engine will then be set as the default
494 for all available algorithms.
496 =item B<-id_prefix arg>
498 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
499 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
500 servers, when each of which might be generating a unique range of session
501 IDs (eg. with a certain prefix).
503 =item B<-rand file(s)>
505 A file or files containing random data used to seed the random number
506 generator, or an EGD socket (see L<RAND_egd(3)>).
507 Multiple files can be specified separated by an OS-dependent character.
508 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
511 =item B<-serverinfo file>
513 A file containing one or more blocks of PEM data. Each PEM block
514 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
515 followed by "length" bytes of extension data). If the client sends
516 an empty TLS ClientHello extension matching the type, the corresponding
517 ServerHello extension will be returned.
519 =item B<-no_resumption_on_reneg>
521 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
525 Enables certificate status request support (aka OCSP stapling).
527 =item B<-status_verbose>
529 Enables certificate status request support (aka OCSP stapling) and gives
530 a verbose printout of the OCSP response.
532 =item B<-status_timeout nsec>
534 Sets the timeout for OCSP response to B<nsec> seconds.
536 =item B<-status_url url>
538 Sets a fallback responder URL to use if no responder URL is present in the
539 server certificate. Without this option an error is returned if the server
540 certificate does not contain a responder address.
542 =item B<-status_file file>
544 Overrides any OCSP responder URLs from the certificate and always provides the
545 OCSP Response stored in the file. The file must be in DER format.
547 =item B<-alpn protocols>, B<-nextprotoneg protocols>
549 These flags enable the Enable the Application-Layer Protocol Negotiation
550 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
551 IETF standard and replaces NPN.
552 The B<protocols> list is a comma-separated list of supported protocol
553 names. The list should contain the most desirable protocols first.
554 Protocol names are printable ASCII strings, for example "http/1.1" or
557 =item B<-keylogfile path>
559 Appends TLS secrets to the specified keylog file such that external programs
560 (like Wireshark) can decrypt TLS connections.
562 =item B<-max_early_data arg>
564 Change the default maximum early data bytes that are specified for new sessions
565 and any incoming early data (when used in conjunction with the B<-early_data>
566 flag). The default value is approximately 16k. The argument must be an integer
567 greater than or equal to 0.
571 Accept early data where possible.
575 =head1 CONNECTED COMMANDS
577 If a connection request is established with an SSL client and neither the
578 B<-www> nor the B<-WWW> option has been used then normally any data received
579 from the client is displayed and any key presses will be sent to the client.
581 Certain single letter commands are also recognized which perform special
582 operations: these are listed below.
588 End the current SSL connection but still accept new connections.
592 End the current SSL connection and exit.
596 Renegotiate the SSL session.
600 Renegotiate the SSL session and request a client certificate.
604 Send some plain text down the underlying TCP connection: this should
605 cause the client to disconnect due to a protocol violation.
609 Print out some session cache status information.
615 B<s_server> can be used to debug SSL clients. To accept connections from
616 a web browser the command:
618 openssl s_server -accept 443 -www
620 can be used for example.
622 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
623 suites, so they cannot connect to servers which don't use a certificate
624 carrying an RSA key or a version of OpenSSL with RSA disabled.
626 Although specifying an empty list of CAs when requesting a client certificate
627 is strictly speaking a protocol violation, some SSL clients interpret this to
628 mean any CA is acceptable. This is useful for debugging purposes.
630 The session parameters can printed out using the B<sess_id> program.
634 Because this program has a lot of options and also because some of the
635 techniques used are rather old, the C source of B<s_server> is rather hard to
636 read and not a model of how things should be done.
637 A typical SSL server program would be much simpler.
639 The output of common ciphers is wrong: it just gives the list of ciphers that
640 OpenSSL recognizes and the client supports.
642 There should be a way for the B<s_server> program to print out details of any
643 unknown cipher suites a client says it supports.
647 L<SSL_CONF_cmd(3)>, L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
648 L<SSL_CTX_set_max_send_fragment(3)>, L<SSL_CTX_set_split_send_fragment(3)>
649 L<SSL_CTX_set_max_pipelines(3)>
653 The -no_alt_chains options was first added to OpenSSL 1.1.0.
657 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
659 Licensed under the OpenSSL license (the "License"). You may not use
660 this file except in compliance with the License. You can obtain a copy
661 in the file LICENSE in the source distribution or at
662 L<https://www.openssl.org/source/license.html>.