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>]
110 [B<-serverinfo file>]
111 [B<-no_resumption_on_reneg>]
114 [B<-status_timeout nsec>]
116 [B<-status_file file>]
118 [B<-nextprotoneg protocols>]
124 The B<s_server> command implements a generic SSL/TLS server which listens
125 for connections on a given port using SSL/TLS.
129 In addition to the options below the B<s_server> utility also supports the
130 common and server only options documented in the
131 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
138 Print out a usage message.
142 The TCP port to listen on for connections. If not specified 4433 is used.
146 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
148 =item B<-naccept count>
150 The server will exit after receiving B<number> connections, default unlimited.
154 Unix domain socket to accept on.
158 For -unix, unlink existing socket first.
170 Sets the SSL context id. It can be given any string value. If this option
171 is not present a default value will be used.
173 =item B<-cert certname>
175 The certificate to use, most servers cipher suites require the use of a
176 certificate and some require a certificate with a certain public key type:
177 for example the DSS cipher suites require a certificate containing a DSS
178 (DSA) key. If not specified then the filename "server.pem" will be used.
180 =item B<-certform format>
182 The certificate format to use: DER or PEM. PEM is the default.
184 =item B<-key keyfile>
186 The private key to use. If not specified then the certificate file will
189 =item B<-keyform format>
191 The private format to use: DER or PEM. PEM is the default.
195 The private key password source. For more information about the format of B<arg>
196 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
198 =item B<-dcert filename>, B<-dkey keyname>
200 Specify an additional certificate and private key, these behave in the
201 same manner as the B<-cert> and B<-key> options except there is no default
202 if they are not specified (no additional certificate and key is used). As
203 noted above some cipher suites require a certificate containing a key of
204 a certain type. Some cipher suites need a certificate carrying an RSA key
205 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
206 a server can support clients which only support RSA or DSS cipher suites
207 by using an appropriate certificate.
209 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
211 Additional certificate and private key format and passphrase respectively.
215 If this option is set then no certificate is used. This restricts the
216 cipher suites available to the anonymous ones (currently just anonymous
219 =item B<-dhparam filename>
221 The DH parameter file to use. The ephemeral DH cipher suites generate keys
222 using a set of DH parameters. If not specified then an attempt is made to
223 load the parameters from the server certificate file.
224 If this fails then a static set of parameters hard coded into the B<s_server>
225 program will be used.
229 If this option is set then no DH parameters will be loaded effectively
230 disabling the ephemeral DH cipher suites.
232 =item B<-crl_check>, B<-crl_check_all>
234 Check the peer certificate has not been revoked by its CA.
235 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
236 option all CRLs of all CAs in the chain are checked.
238 =item B<-CApath directory>
240 The directory to use for client certificate verification. This directory
241 must be in "hash format", see B<verify> for more information. These are
242 also used when building the server certificate chain.
244 =item B<-CAfile file>
246 A file containing trusted certificates to use during client authentication
247 and to use when attempting to build the server certificate chain. The list
248 is also used in the list of acceptable client CAs passed to the client when
249 a certificate is requested.
253 Do not load the trusted CA certificates from the default file location.
257 Do not load the trusted CA certificates from the default directory location.
259 =item B<-verify depth>, B<-Verify depth>
261 The verify depth to use. This specifies the maximum length of the
262 client certificate chain and makes the server request a certificate from
263 the client. With the B<-verify> option a certificate is requested but the
264 client does not have to send one, with the B<-Verify> option the client
265 must supply a certificate or an error occurs.
267 If the cipher suite cannot request a client certificate (for example an
268 anonymous cipher suite or PSK) this option has no effect.
270 =item B<-nameopt option>
272 Option which determines how the subject or issuer names are displayed. The
273 B<option> argument can be a single option or multiple options separated by
274 commas. Alternatively the B<-nameopt> switch may be used more than once to
275 set multiple options. See the L<x509(1)> manual page for details.
277 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
278 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
279 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
280 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
281 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
282 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
283 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
285 Set different peer certificate verification options.
286 See the L<verify(1)> manual page for details.
288 =item B<-verify_return_error>
290 Verification errors normally just print a message but allow the
291 connection to continue, for debugging purposes.
292 If this option is used, then verification errors close the connection.
296 Prints the SSL session states.
300 Print extensive debugging information including a hex dump of all traffic.
304 Show all protocol messages with hex dump.
308 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
309 with B<enable-ssl-trace> for this option to work.
313 File to send output of B<-msg> or B<-trace> to, default standard output.
317 Tests non blocking I/O.
321 Turns on non blocking I/O.
325 This option translated a line feed from the terminal into CR+LF.
329 Inhibit printing of session and certificate information.
331 =item B<-psk_hint hint>
333 Use the PSK identity hint B<hint> when using a PSK cipher suite.
337 Use the PSK key B<key> when using a PSK cipher suite. The key is
338 given as a hexadecimal number without leading 0x, for example -psk
341 =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>
343 These options require or disable the use of the specified SSL or TLS protocols.
344 By default B<s_server> will negotiate the highest mutually supported protocol
346 When a specific TLS version is required, only that version will be accepted
349 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
351 These options make B<s_server> use DTLS protocols instead of TLS.
352 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
353 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
358 This option can only be used in conjunction with one of the DTLS options above.
359 With this option B<s_server> will listen on a UDP port for incoming connections.
360 Any ClientHellos that arrive will be checked to see if they have a cookie in
362 Any without a cookie will be responded to with a HelloVerifyRequest.
363 If a ClientHello with a cookie is received then B<s_server> will connect to
364 that peer and complete the handshake.
368 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
369 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
370 available where OpenSSL has support for SCTP enabled.
374 Switch on asynchronous mode. Cryptographic operations will be performed
375 asynchronously. This will only have an effect if an asynchronous capable engine
376 is also used via the B<-engine> option. For test purposes the dummy async engine
377 (dasync) can be used (if available).
379 =item B<-split_send_frag int>
381 The size used to split data for encrypt pipelines. If more data is written in
382 one go than this value then it will be split into multiple pipelines, up to the
383 maximum number of pipelines defined by max_pipelines. This only has an effect if
384 a suitable cipher suite has been negotiated, an engine that supports pipelining
385 has been loaded, and max_pipelines is greater than 1. See
386 L<SSL_CTX_set_split_send_fragment(3)> for further information.
388 =item B<-max_pipelines int>
390 The maximum number of encrypt/decrypt pipelines to be used. This will only have
391 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
392 engine) and a suitable cipher suite has been negotiated. The default value is 1.
393 See L<SSL_CTX_set_max_pipelines(3)> for further information.
395 =item B<-read_buf int>
397 The default read buffer size to be used for connections. This will only have an
398 effect if the buffer size is larger than the size that would otherwise be used
399 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
400 further information).
404 There are several known bug in SSL and TLS implementations. Adding this
405 option enables various workarounds.
409 Enable negotiation of TLS compression.
410 This option was introduced in OpenSSL 1.1.0.
411 TLS compression is not recommended and is off by default as of
416 Disable negotiation of TLS compression.
417 TLS compression is not recommended and is off by default as of
422 Provide a brief summary of connection parameters instead of the normal verbose
425 =item B<-client_sigalgs sigalglist>
427 Signature algorithms to support for client certificate authentication
428 (colon-separated list).
430 =item B<-named_curve curve>
432 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
433 For a list of all possible curves, use:
435 $ openssl ecparam -list_curves
437 =item B<-cipher cipherlist>
439 This allows the cipher list used by the server to be modified. When
440 the client sends a list of supported ciphers the first client cipher
441 also included in the server list is used. Because the client specifies
442 the preference order, the order of the server cipherlist irrelevant. See
443 the B<ciphers> command for more information.
447 Use the server's cipher preferences, rather than the client's preferences.
449 =item B<-tlsextdebug>
451 Print a hex dump of any TLS extensions received from the server.
455 Disable RFC4507bis session ticket support.
459 Sends a status message back to the client when it connects. This includes
460 information about the ciphers used and various session parameters.
461 The output is in HTML format so this option will normally be used with a
466 Emulates a simple web server. Pages will be resolved relative to the
467 current directory, for example if the URL https://myhost/page.html is
468 requested the file ./page.html will be loaded.
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. The files loaded are
475 assumed to contain a complete and correct HTTP response (lines that
476 are part of the HTTP response line and headers must end with CRLF).
480 Simple test server which just reverses the text received from the client
481 and sends it back to the server. Also sets B<-brief>.
485 Specifying an engine (by its unique B<id> string) will cause B<s_server>
486 to attempt to obtain a functional reference to the specified engine,
487 thus initialising it if needed. The engine will then be set as the default
488 for all available algorithms.
490 =item B<-id_prefix arg>
492 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
493 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
494 servers, when each of which might be generating a unique range of session
495 IDs (eg. with a certain prefix).
497 =item B<-rand file(s)>
499 A file or files containing random data used to seed the random number
500 generator, or an EGD socket (see L<RAND_egd(3)>).
501 Multiple files can be specified separated by an OS-dependent character.
502 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
505 =item B<-serverinfo file>
507 A file containing one or more blocks of PEM data. Each PEM block
508 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
509 followed by "length" bytes of extension data). If the client sends
510 an empty TLS ClientHello extension matching the type, the corresponding
511 ServerHello extension will be returned.
513 =item B<-no_resumption_on_reneg>
515 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
519 Enables certificate status request support (aka OCSP stapling).
521 =item B<-status_verbose>
523 Enables certificate status request support (aka OCSP stapling) and gives
524 a verbose printout of the OCSP response.
526 =item B<-status_timeout nsec>
528 Sets the timeout for OCSP response to B<nsec> seconds.
530 =item B<-status_url url>
532 Sets a fallback responder URL to use if no responder URL is present in the
533 server certificate. Without this option an error is returned if the server
534 certificate does not contain a responder address.
536 =item B<-status_file file>
538 Overrides any OCSP responder URLs from the certificate and always provides the
539 OCSP Response stored in the file. The file must be in DER format.
541 =item B<-alpn protocols>, B<-nextprotoneg protocols>
543 These flags enable the Enable the Application-Layer Protocol Negotiation
544 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
545 IETF standard and replaces NPN.
546 The B<protocols> list is a comma-separated list of supported protocol
547 names. The list should contain the most desirable protocols first.
548 Protocol names are printable ASCII strings, for example "http/1.1" or
551 =item B<-keylogfile path>
553 Appends TLS secrets to the specified keylog file such that external programs
554 (like Wireshark) can decrypt TLS connections.
556 =item B<-max_early_data arg>
558 Change the default maximum early data bytes that are specified for new sessions
559 and any incoming early data (when used in conjunction with the B<-early_data>
560 flag). The default value is approximately 16k. The argument must be an integer
561 greater than or equal to 0.
565 Accept early data where possible.
569 =head1 CONNECTED COMMANDS
571 If a connection request is established with an SSL client and neither the
572 B<-www> nor the B<-WWW> option has been used then normally any data received
573 from the client is displayed and any key presses will be sent to the client.
575 Certain single letter commands are also recognized which perform special
576 operations: these are listed below.
582 End the current SSL connection but still accept new connections.
586 End the current SSL connection and exit.
590 Renegotiate the SSL session.
594 Renegotiate the SSL session and request a client certificate.
598 Send some plain text down the underlying TCP connection: this should
599 cause the client to disconnect due to a protocol violation.
603 Print out some session cache status information.
609 B<s_server> can be used to debug SSL clients. To accept connections from
610 a web browser the command:
612 openssl s_server -accept 443 -www
614 can be used for example.
616 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
617 suites, so they cannot connect to servers which don't use a certificate
618 carrying an RSA key or a version of OpenSSL with RSA disabled.
620 Although specifying an empty list of CAs when requesting a client certificate
621 is strictly speaking a protocol violation, some SSL clients interpret this to
622 mean any CA is acceptable. This is useful for debugging purposes.
624 The session parameters can printed out using the B<sess_id> program.
628 Because this program has a lot of options and also because some of the
629 techniques used are rather old, the C source of B<s_server> is rather hard to
630 read and not a model of how things should be done.
631 A typical SSL server program would be much simpler.
633 The output of common ciphers is wrong: it just gives the list of ciphers that
634 OpenSSL recognizes and the client supports.
636 There should be a way for the B<s_server> program to print out details of any
637 unknown cipher suites a client says it supports.
642 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
646 The -no_alt_chains options was first added to OpenSSL 1.1.0.
650 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
652 Licensed under the OpenSSL license (the "License"). You may not use
653 this file except in compliance with the License. You can obtain a copy
654 in the file LICENSE in the source distribution or at
655 L<https://www.openssl.org/source/license.html>.