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>]
98 [B<-no_resumption_on_reneg>]
101 [B<-status_timeout nsec>]
104 [B<-nextprotoneg protocols>]
108 The B<s_server> command implements a generic SSL/TLS server which listens
109 for connections on a given port using SSL/TLS.
113 In addition to the options below the B<s_server> utility also supports the
114 common and server only options documented in the
115 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
122 Print out a usage message.
124 =item B<-accept port>
126 The TCP port to listen on for connections. If not specified 4433 is used.
128 =item B<-naccept count>
130 The server will exit after receiving B<number> connections, default unlimited.
134 Sets the SSL context id. It can be given any string value. If this option
135 is not present a default value will be used.
137 =item B<-cert certname>
139 The certificate to use, most servers cipher suites require the use of a
140 certificate and some require a certificate with a certain public key type:
141 for example the DSS cipher suites require a certificate containing a DSS
142 (DSA) key. If not specified then the filename "server.pem" will be used.
144 =item B<-certform format>
146 The certificate format to use: DER or PEM. PEM is the default.
148 =item B<-key keyfile>
150 The private key to use. If not specified then the certificate file will
153 =item B<-keyform format>
155 The private format to use: DER or PEM. PEM is the default.
159 The private key password source. For more information about the format of B<arg>
160 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
162 =item B<-dcert filename>, B<-dkey keyname>
164 Specify an additional certificate and private key, these behave in the
165 same manner as the B<-cert> and B<-key> options except there is no default
166 if they are not specified (no additional certificate and key is used). As
167 noted above some cipher suites require a certificate containing a key of
168 a certain type. Some cipher suites need a certificate carrying an RSA key
169 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
170 a server can support clients which only support RSA or DSS cipher suites
171 by using an appropriate certificate.
173 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
175 Additional certificate and private key format and passphrase respectively.
179 If this option is set then no certificate is used. This restricts the
180 cipher suites available to the anonymous ones (currently just anonymous
183 =item B<-dhparam filename>
185 The DH parameter file to use. The ephemeral DH cipher suites generate keys
186 using a set of DH parameters. If not specified then an attempt is made to
187 load the parameters from the server certificate file.
188 If this fails then a static set of parameters hard coded into the B<s_server>
189 program will be used.
193 If this option is set then no DH parameters will be loaded effectively
194 disabling the ephemeral DH cipher suites.
196 =item B<-crl_check>, B<-crl_check_all>
198 Check the peer certificate has not been revoked by its CA.
199 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
200 option all CRLs of all CAs in the chain are checked.
202 =item B<-CApath directory>
204 The directory to use for client certificate verification. This directory
205 must be in "hash format", see B<verify> for more information. These are
206 also used when building the server certificate chain.
208 =item B<-CAfile file>
210 A file containing trusted certificates to use during client authentication
211 and to use when attempting to build the server certificate chain. The list
212 is also used in the list of acceptable client CAs passed to the client when
213 a certificate is requested.
217 Do not load the trusted CA certificates from the default file location
221 Do not load the trusted CA certificates from the default directory location
223 =item B<-verify depth>, B<-Verify depth>
225 The verify depth to use. This specifies the maximum length of the
226 client certificate chain and makes the server request a certificate from
227 the client. With the B<-verify> option a certificate is requested but the
228 client does not have to send one, with the B<-Verify> option the client
229 must supply a certificate or an error occurs.
231 If the ciphersuite cannot request a client certificate (for example an
232 anonymous ciphersuite or PSK) this option has no effect.
234 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
235 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
236 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
237 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
238 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
239 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
240 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
242 Set different peer certificate verification options.
243 See the L<verify(1)> manual page for details.
245 =item B<-verify_return_error>
247 Verification errors normally just print a message but allow the
248 connection to continue, for debugging purposes.
249 If this option is used, then verification errors close the connection.
253 Prints the SSL session states.
257 Print extensive debugging information including a hex dump of all traffic.
261 Show all protocol messages with hex dump.
265 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
266 with B<enable-ssl-trace> for this option to work.
270 File to send output of B<-msg> or B<-trace> to, default standard output.
274 Tests non blocking I/O
278 Turns on non blocking I/O
282 This option translated a line feed from the terminal into CR+LF.
286 Inhibit printing of session and certificate information.
288 =item B<-psk_hint hint>
290 Use the PSK identity hint B<hint> when using a PSK cipher suite.
294 Use the PSK key B<key> when using a PSK cipher suite. The key is
295 given as a hexadecimal number without leading 0x, for example -psk
298 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-tls1_1>, B<-tls1_2>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
300 These options require or disable the use of the specified SSL or TLS protocols.
301 By default B<s_server> will negotiate the highest mutually supported protocol
303 When a specific TLS version is required, only that version will be accepted
306 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
308 These options make B<s_server> use DTLS protocols instead of TLS.
309 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
310 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
315 This option can only be used in conjunction with one of the DTLS options above.
316 With this option B<s_server> will listen on a UDP port for incoming connections.
317 Any ClientHellos that arrive will be checked to see if they have a cookie in
319 Any without a cookie will be responded to with a HelloVerifyRequest.
320 If a ClientHello with a cookie is received then B<s_server> will connect to
321 that peer and complete the handshake.
325 Switch on asynchronous mode. Cryptographic operations will be performed
326 asynchronously. This will only have an effect if an asynchronous capable engine
327 is also used via the B<-engine> option. For test purposes the dummy async engine
328 (dasync) can be used (if available).
330 =item B<-split_send_frag int>
332 The size used to split data for encrypt pipelines. If more data is written in
333 one go than this value then it will be split into multiple pipelines, up to the
334 maximum number of pipelines defined by max_pipelines. This only has an effect if
335 a suitable ciphersuite has been negotiated, an engine that supports pipelining
336 has been loaded, and max_pipelines is greater than 1. See
337 L<SSL_CTX_set_split_send_fragment(3)> for further information.
339 =item B<-max_pipelines int>
341 The maximum number of encrypt/decrypt pipelines to be used. This will only have
342 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
343 engine) and a suitable ciphersuite has been negotiated. The default value is 1.
344 See L<SSL_CTX_set_max_pipelines(3)> for further information.
346 =item B<-read_buf int>
348 The default read buffer size to be used for connections. This will only have an
349 effect if the buffer size is larger than the size that would otherwise be used
350 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
351 further information).
355 There are several known bug in SSL and TLS implementations. Adding this
356 option enables various workarounds.
360 Enable negotiation of TLS compression.
361 This option was introduced in OpenSSL 1.1.0.
362 TLS compression is not recommended and is off by default as of
367 Disable negotiation of TLS compression.
368 TLS compression is not recommended and is off by default as of
373 Provide a brief summary of connection parameters instead of the normal verbose
376 =item B<-cipher cipherlist>
378 This allows the cipher list used by the server to be modified. When
379 the client sends a list of supported ciphers the first client cipher
380 also included in the server list is used. Because the client specifies
381 the preference order, the order of the server cipherlist irrelevant. See
382 the B<ciphers> command for more information.
386 Use the server's cipher preferences, rather than the client's preferences.
388 =item B<-tlsextdebug>
390 Print a hex dump of any TLS extensions received from the server.
394 Disable RFC4507bis session ticket support.
398 Sends a status message back to the client when it connects. This includes
399 information about the ciphers used and various session parameters.
400 The output is in HTML format so this option will normally be used with a
405 Emulates a simple web server. Pages will be resolved relative to the
406 current directory, for example if the URL https://myhost/page.html is
407 requested the file ./page.html will be loaded.
411 Emulates a simple web server. Pages will be resolved relative to the
412 current directory, for example if the URL https://myhost/page.html is
413 requested the file ./page.html will be loaded. The files loaded are
414 assumed to contain a complete and correct HTTP response (lines that
415 are part of the HTTP response line and headers must end with CRLF).
419 Simple test server which just reverses the text received from the client
420 and sends it back to the server. Also sets B<-brief>.
424 Specifying an engine (by its unique B<id> string) will cause B<s_server>
425 to attempt to obtain a functional reference to the specified engine,
426 thus initialising it if needed. The engine will then be set as the default
427 for all available algorithms.
429 =item B<-id_prefix arg>
431 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
432 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
433 servers, when each of which might be generating a unique range of session
434 IDs (eg. with a certain prefix).
436 =item B<-rand file(s)>
438 A file or files containing random data used to seed the random number
439 generator, or an EGD socket (see L<RAND_egd(3)>).
440 Multiple files can be specified separated by an OS-dependent character.
441 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
444 =item B<-serverinfo file>
446 A file containing one or more blocks of PEM data. Each PEM block
447 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
448 followed by "length" bytes of extension data). If the client sends
449 an empty TLS ClientHello extension matching the type, the corresponding
450 ServerHello extension will be returned.
452 =item B<-no_resumption_on_reneg>
454 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
458 Enables certificate status request support (aka OCSP stapling).
460 =item B<-status_verbose>
462 Enables certificate status request support (aka OCSP stapling) and gives
463 a verbose printout of the OCSP response.
465 =item B<-status_timeout nsec>
467 Sets the timeout for OCSP response to B<nsec> seconds.
469 =item B<-status_url url>
471 Sets a fallback responder URL to use if no responder URL is present in the
472 server certificate. Without this option an error is returned if the server
473 certificate does not contain a responder address.
475 =item B<-alpn protocols>, B<-nextprotoneg protocols>
477 these flags enable the
478 Enable the Application-Layer Protocol Negotiation or Next Protocol
479 Negotiation extension, respectively. ALPN is the IETF standard and
481 The B<protocols> list is a
482 comma-separated list of supported protocol names.
483 The list should contain most wanted protocols first.
484 Protocol names are printable ASCII strings, for example "http/1.1" or
489 =head1 CONNECTED COMMANDS
491 If a connection request is established with an SSL client and neither the
492 B<-www> nor the B<-WWW> option has been used then normally any data received
493 from the client is displayed and any key presses will be sent to the client.
495 Certain single letter commands are also recognized which perform special
496 operations: these are listed below.
502 end the current SSL connection but still accept new connections.
506 end the current SSL connection and exit.
510 renegotiate the SSL session.
514 renegotiate the SSL session and request a client certificate.
518 send some plain text down the underlying TCP connection: this should
519 cause the client to disconnect due to a protocol violation.
523 print out some session cache status information.
529 B<s_server> can be used to debug SSL clients. To accept connections from
530 a web browser the command:
532 openssl s_server -accept 443 -www
534 can be used for example.
536 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
537 suites, so they cannot connect to servers which don't use a certificate
538 carrying an RSA key or a version of OpenSSL with RSA disabled.
540 Although specifying an empty list of CAs when requesting a client certificate
541 is strictly speaking a protocol violation, some SSL clients interpret this to
542 mean any CA is acceptable. This is useful for debugging purposes.
544 The session parameters can printed out using the B<sess_id> program.
548 Because this program has a lot of options and also because some of the
549 techniques used are rather old, the C source of B<s_server> is rather hard to
550 read and not a model of how things should be done.
551 A typical SSL server program would be much simpler.
553 The output of common ciphers is wrong: it just gives the list of ciphers that
554 OpenSSL recognizes and the client supports.
556 There should be a way for the B<s_server> program to print out details of any
557 unknown cipher suites a client says it supports.
562 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
566 The -no_alt_chains options was first added to OpenSSL 1.1.0.
570 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
572 Licensed under the OpenSSL license (the "License"). You may not use
573 this file except in compliance with the License. You can obtain a copy
574 in the file LICENSE in the source distribution or at
575 L<https://www.openssl.org/source/license.html>.