5 s_server - SSL/TLS server program
19 [B<-certform DER|PEM>]
24 [B<-dcertform DER|PEM>]
26 [B<-dkeyform DER|PEM>]
28 [B<-dhparam filename>]
35 [B<-CApath directory>]
39 [B<-attime timestamp>]
59 [B<-verify_depth num>]
60 [B<-verify_return_error>]
61 [B<-verify_email email>]
62 [B<-verify_hostname hostname>]
64 [B<-verify_name name>]
67 [B<-cipher cipherlist>]
101 [B<-serverinfo file>]
102 [B<-no_resumption_on_reneg>]
105 [B<-status_timeout nsec>]
108 [B<-nextprotoneg protocols>]
112 The B<s_server> command implements a generic SSL/TLS server which listens
113 for connections on a given port using SSL/TLS.
117 In addition to the options below the B<s_server> utility also supports the
118 common and server only options documented in the
119 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
126 Print out a usage message.
128 =item B<-accept port>
130 The TCP port to listen on for connections. If not specified 4433 is used.
132 =item B<-naccept count>
134 The server will exit after receiving B<number> connections, default unlimited.
138 Sets the SSL context id. It can be given any string value. If this option
139 is not present a default value will be used.
141 =item B<-cert certname>
143 The certificate to use, most servers cipher suites require the use of a
144 certificate and some require a certificate with a certain public key type:
145 for example the DSS cipher suites require a certificate containing a DSS
146 (DSA) key. If not specified then the filename "server.pem" will be used.
148 =item B<-certform format>
150 The certificate format to use: DER or PEM. PEM is the default.
152 =item B<-key keyfile>
154 The private key to use. If not specified then the certificate file will
157 =item B<-keyform format>
159 The private format to use: DER or PEM. PEM is the default.
163 The private key password source. For more information about the format of B<arg>
164 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
166 =item B<-dcert filename>, B<-dkey keyname>
168 Specify an additional certificate and private key, these behave in the
169 same manner as the B<-cert> and B<-key> options except there is no default
170 if they are not specified (no additional certificate and key is used). As
171 noted above some cipher suites require a certificate containing a key of
172 a certain type. Some cipher suites need a certificate carrying an RSA key
173 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
174 a server can support clients which only support RSA or DSS cipher suites
175 by using an appropriate certificate.
177 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
179 Additional certificate and private key format and passphrase respectively.
183 If this option is set then no certificate is used. This restricts the
184 cipher suites available to the anonymous ones (currently just anonymous
187 =item B<-dhparam filename>
189 The DH parameter file to use. The ephemeral DH cipher suites generate keys
190 using a set of DH parameters. If not specified then an attempt is made to
191 load the parameters from the server certificate file.
192 If this fails then a static set of parameters hard coded into the B<s_server>
193 program will be used.
197 If this option is set then no DH parameters will be loaded effectively
198 disabling the ephemeral DH cipher suites.
200 =item B<-crl_check>, B<-crl_check_all>
202 Check the peer certificate has not been revoked by its CA.
203 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
204 option all CRLs of all CAs in the chain are checked.
206 =item B<-CApath directory>
208 The directory to use for client certificate verification. This directory
209 must be in "hash format", see B<verify> for more information. These are
210 also used when building the server certificate chain.
212 =item B<-CAfile file>
214 A file containing trusted certificates to use during client authentication
215 and to use when attempting to build the server certificate chain. The list
216 is also used in the list of acceptable client CAs passed to the client when
217 a certificate is requested.
221 Do not load the trusted CA certificates from the default file location
225 Do not load the trusted CA certificates from the default directory location
227 =item B<-verify depth>, B<-Verify depth>
229 The verify depth to use. This specifies the maximum length of the
230 client certificate chain and makes the server request a certificate from
231 the client. With the B<-verify> option a certificate is requested but the
232 client does not have to send one, with the B<-Verify> option the client
233 must supply a certificate or an error occurs.
235 If the ciphersuite cannot request a client certificate (for example an
236 anonymous ciphersuite or PSK) this option has no effect.
238 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
239 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
240 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
241 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
242 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
243 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
244 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
246 Set different peer certificate verification options.
247 See the L<verify(1)> manual page for details.
249 =item B<-verify_return_error>
251 Verification errors normally just print a message but allow the
252 connection to continue, for debugging purposes.
253 If this option is used, then verification errors close the connection.
257 Prints the SSL session states.
261 Print extensive debugging information including a hex dump of all traffic.
265 Show all protocol messages with hex dump.
269 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
270 with B<enable-ssl-trace> for this option to work.
274 File to send output of B<-msg> or B<-trace> to, default standard output.
278 Tests non blocking I/O
282 Turns on non blocking I/O
286 This option translated a line feed from the terminal into CR+LF.
290 Inhibit printing of session and certificate information.
292 =item B<-psk_hint hint>
294 Use the PSK identity hint B<hint> when using a PSK cipher suite.
298 Use the PSK key B<key> when using a PSK cipher suite. The key is
299 given as a hexadecimal number without leading 0x, for example -psk
302 =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>
304 These options require or disable the use of the specified SSL or TLS protocols.
305 By default B<s_server> will negotiate the highest mutually supported protocol
307 When a specific TLS version is required, only that version will be accepted
310 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
312 These options make B<s_server> use DTLS protocols instead of TLS.
313 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
314 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
319 This option can only be used in conjunction with one of the DTLS options above.
320 With this option B<s_server> will listen on a UDP port for incoming connections.
321 Any ClientHellos that arrive will be checked to see if they have a cookie in
323 Any without a cookie will be responded to with a HelloVerifyRequest.
324 If a ClientHello with a cookie is received then B<s_server> will connect to
325 that peer and complete the handshake.
329 Switch on asynchronous mode. Cryptographic operations will be performed
330 asynchronously. This will only have an effect if an asynchronous capable engine
331 is also used via the B<-engine> option. For test purposes the dummy async engine
332 (dasync) can be used (if available).
334 =item B<-split_send_frag int>
336 The size used to split data for encrypt pipelines. If more data is written in
337 one go than this value then it will be split into multiple pipelines, up to the
338 maximum number of pipelines defined by max_pipelines. This only has an effect if
339 a suitable ciphersuite has been negotiated, an engine that supports pipelining
340 has been loaded, and max_pipelines is greater than 1. See
341 L<SSL_CTX_set_split_send_fragment(3)> for further information.
343 =item B<-max_pipelines int>
345 The maximum number of encrypt/decrypt pipelines to be used. This will only have
346 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
347 engine) and a suitable ciphersuite has been negotiated. The default value is 1.
348 See L<SSL_CTX_set_max_pipelines(3)> for further information.
350 =item B<-read_buf int>
352 The default read buffer size to be used for connections. This will only have an
353 effect if the buffer size is larger than the size that would otherwise be used
354 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
355 further information).
359 There are several known bug in SSL and TLS implementations. Adding this
360 option enables various workarounds.
364 Enable negotiation of TLS compression.
365 This option was introduced in OpenSSL 1.1.0.
366 TLS compression is not recommended and is off by default as of
371 Disable negotiation of TLS compression.
372 TLS compression is not recommended and is off by default as of
377 Provide a brief summary of connection parameters instead of the normal verbose
380 =item B<-cipher cipherlist>
382 This allows the cipher list used by the server to be modified. When
383 the client sends a list of supported ciphers the first client cipher
384 also included in the server list is used. Because the client specifies
385 the preference order, the order of the server cipherlist irrelevant. See
386 the B<ciphers> command for more information.
390 Use the server's cipher preferences, rather than the client's preferences.
392 =item B<-tlsextdebug>
394 Print a hex dump of any TLS extensions received from the server.
398 Disable RFC4507bis session ticket support.
402 Sends a status message back to the client when it connects. This includes
403 information about the ciphers used and various session parameters.
404 The output is in HTML format so this option will normally be used with a
409 Emulates a simple web server. Pages will be resolved relative to the
410 current directory, for example if the URL https://myhost/page.html is
411 requested the file ./page.html will be loaded.
415 Emulates a simple web server. Pages will be resolved relative to the
416 current directory, for example if the URL https://myhost/page.html is
417 requested the file ./page.html will be loaded. The files loaded are
418 assumed to contain a complete and correct HTTP response (lines that
419 are part of the HTTP response line and headers must end with CRLF).
423 Simple test server which just reverses the text received from the client
424 and sends it back to the server. Also sets B<-brief>.
428 Specifying an engine (by its unique B<id> string) will cause B<s_server>
429 to attempt to obtain a functional reference to the specified engine,
430 thus initialising it if needed. The engine will then be set as the default
431 for all available algorithms.
433 =item B<-id_prefix arg>
435 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
436 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
437 servers, when each of which might be generating a unique range of session
438 IDs (eg. with a certain prefix).
440 =item B<-rand file(s)>
442 A file or files containing random data used to seed the random number
443 generator, or an EGD socket (see L<RAND_egd(3)>).
444 Multiple files can be specified separated by an OS-dependent character.
445 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
448 =item B<-serverinfo file>
450 A file containing one or more blocks of PEM data. Each PEM block
451 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
452 followed by "length" bytes of extension data). If the client sends
453 an empty TLS ClientHello extension matching the type, the corresponding
454 ServerHello extension will be returned.
456 =item B<-no_resumption_on_reneg>
458 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
462 Enables certificate status request support (aka OCSP stapling).
464 =item B<-status_verbose>
466 Enables certificate status request support (aka OCSP stapling) and gives
467 a verbose printout of the OCSP response.
469 =item B<-status_timeout nsec>
471 Sets the timeout for OCSP response to B<nsec> seconds.
473 =item B<-status_url url>
475 Sets a fallback responder URL to use if no responder URL is present in the
476 server certificate. Without this option an error is returned if the server
477 certificate does not contain a responder address.
479 =item B<-alpn protocols>, B<-nextprotoneg protocols>
481 these flags enable the
482 Enable the Application-Layer Protocol Negotiation or Next Protocol
483 Negotiation extension, respectively. ALPN is the IETF standard and
485 The B<protocols> list is a
486 comma-separated list of supported protocol names.
487 The list should contain most wanted protocols first.
488 Protocol names are printable ASCII strings, for example "http/1.1" or
493 =head1 CONNECTED COMMANDS
495 If a connection request is established with an SSL client and neither the
496 B<-www> nor the B<-WWW> option has been used then normally any data received
497 from the client is displayed and any key presses will be sent to the client.
499 Certain single letter commands are also recognized which perform special
500 operations: these are listed below.
506 end the current SSL connection but still accept new connections.
510 end the current SSL connection and exit.
514 renegotiate the SSL session.
518 renegotiate the SSL session and request a client certificate.
522 send some plain text down the underlying TCP connection: this should
523 cause the client to disconnect due to a protocol violation.
527 print out some session cache status information.
533 B<s_server> can be used to debug SSL clients. To accept connections from
534 a web browser the command:
536 openssl s_server -accept 443 -www
538 can be used for example.
540 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
541 suites, so they cannot connect to servers which don't use a certificate
542 carrying an RSA key or a version of OpenSSL with RSA disabled.
544 Although specifying an empty list of CAs when requesting a client certificate
545 is strictly speaking a protocol violation, some SSL clients interpret this to
546 mean any CA is acceptable. This is useful for debugging purposes.
548 The session parameters can printed out using the B<sess_id> program.
552 Because this program has a lot of options and also because some of the
553 techniques used are rather old, the C source of B<s_server> is rather hard to
554 read and not a model of how things should be done.
555 A typical SSL server program would be much simpler.
557 The output of common ciphers is wrong: it just gives the list of ciphers that
558 OpenSSL recognizes and the client supports.
560 There should be a way for the B<s_server> program to print out details of any
561 unknown cipher suites a client says it supports.
566 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
570 The -no_alt_chains options was first added to OpenSSL 1.1.0.
574 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
576 Licensed under the OpenSSL license (the "License"). You may not use
577 this file except in compliance with the License. You can obtain a copy
578 in the file LICENSE in the source distribution or at
579 L<https://www.openssl.org/source/license.html>.