5 s_server - SSL/TLS server program
24 [B<-certform PEM|DER>]
29 [B<-dcertform PEM|DER>]
31 [B<-dkeyform PEM|DER>]
45 [B<-no_resume_ephemeral>]
49 [B<-servername_fatal>]
56 [B<-keymatexport val>]
57 [B<-keymatexportlen +int>]
60 [B<-cert_chain infile>]
61 [B<-dcert_chain infile>]
63 [B<-verifyCApath dir>]
67 [B<-verify_return_error>]
70 [B<-chainCAfile infile>]
71 [B<-verifyCAfile infile>]
76 [B<-status_timeout int>]
78 [B<-status_file infile>]
81 [B<-security_debug_verbose>]
86 [B<-max_send_frag +int>]
87 [B<-split_send_frag +int>]
88 [B<-max_pipelines +int>]
100 [B<-legacy_renegotiation>]
101 [B<-no_renegotiation>]
102 [B<-legacy_server_connect>]
103 [B<-no_resumption_on_reneg>]
104 [B<-no_legacy_server_connect>]
107 [B<-client_sigalgs val>]
110 [B<-named_curve val>]
113 [B<-record_padding val>]
114 [B<-debug_broken_protocol>]
117 [B<-verify_name val>]
118 [B<-verify_depth int>]
121 [B<-verify_hostname val>]
122 [B<-verify_email val>]
124 [B<-ignore_critical>]
129 [B<-explicit_policy>]
138 [B<-suiteB_128_only>]
144 [B<-allow_proxy_certs>]
149 [B<-xcertform PEM|DER>]
150 [B<-xkeyform PEM|DER>]
152 [B<-psk_identity val>]
155 [B<-srpvfile infile>]
156 [B<-srpuserseed val>]
170 [B<-nextprotoneg val>]
174 [B<-keylogfile outfile>]
175 [B<-max_early_data int>]
180 The B<s_server> command implements a generic SSL/TLS server which listens
181 for connections on a given port using SSL/TLS.
185 In addition to the options below the B<s_server> utility also supports the
186 common and server only options documented in the
187 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
194 Print out a usage message.
198 The TCP port to listen on for connections. If not specified 4433 is used.
202 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
206 Unix domain socket to accept on.
218 For -unix, unlink any existing socket first.
220 =item B<-context val>
222 Sets the SSL context id. It can be given any string value. If this option
223 is not present a default value will be used.
225 =item B<-verify int>, B<-Verify int>
227 The verify depth to use. This specifies the maximum length of the
228 client certificate chain and makes the server request a certificate from
229 the client. With the B<-verify> option a certificate is requested but the
230 client does not have to send one, with the B<-Verify> option the client
231 must supply a certificate or an error occurs.
233 If the cipher suite cannot request a client certificate (for example an
234 anonymous cipher suite or PSK) this option has no effect.
236 =item B<-cert infile>
238 The certificate to use, most servers cipher suites require the use of a
239 certificate and some require a certificate with a certain public key type:
240 for example the DSS cipher suites require a certificate containing a DSS
241 (DSA) key. If not specified then the filename "server.pem" will be used.
243 =item B<-nameopt val>
245 Option which determines how the subject or issuer names are displayed. The
246 B<val> argument can be a single option or multiple options separated by
247 commas. Alternatively the B<-nameopt> switch may be used more than once to
248 set multiple options. See the L<x509(1)> manual page for details.
250 =item B<-naccept +int>
252 The server will exit after receiving the specified number of connections,
255 =item B<-serverinfo val>
257 A file containing one or more blocks of PEM data. Each PEM block
258 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
259 followed by "length" bytes of extension data). If the client sends
260 an empty TLS ClientHello extension matching the type, the corresponding
261 ServerHello extension will be returned.
263 =item B<-certform PEM|DER>
265 The certificate format to use: DER or PEM. PEM is the default.
269 The private key to use. If not specified then the certificate file will
272 =item B<-keyform format>
274 The private format to use: DER or PEM. PEM is the default.
278 The private key password source. For more information about the format of B<val>
279 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
281 =item B<-dcert infile>, B<-dkey infile>
283 Specify an additional certificate and private key, these behave in the
284 same manner as the B<-cert> and B<-key> options except there is no default
285 if they are not specified (no additional certificate and key is used). As
286 noted above some cipher suites require a certificate containing a key of
287 a certain type. Some cipher suites need a certificate carrying an RSA key
288 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
289 a server can support clients which only support RSA or DSS cipher suites
290 by using an appropriate certificate.
292 =item B<-dcertform PEM|DER>, B<-dkeyform PEM|DER>, B<-dpass val>
294 Additional certificate and private key format and passphrase respectively.
298 Tests non blocking I/O.
302 This option translated a line feed from the terminal into CR+LF.
306 Print extensive debugging information including a hex dump of all traffic.
310 Show all protocol messages with hex dump.
312 =item B<-msgfile outfile>
314 File to send output of B<-msg> or B<-trace> to, default standard output.
318 Prints the SSL session states.
320 =item B<-CAfile infile>
322 A file containing trusted certificates to use during client authentication
323 and to use when attempting to build the server certificate chain. The list
324 is also used in the list of acceptable client CAs passed to the client when
325 a certificate is requested.
329 The directory to use for client certificate verification. This directory
330 must be in "hash format", see B<verify> for more information. These are
331 also used when building the server certificate chain.
335 Do not load the trusted CA certificates from the default file location.
339 Do not load the trusted CA certificates from the default directory location.
343 If this option is set then no certificate is used. This restricts the
344 cipher suites available to the anonymous ones (currently just anonymous
349 Inhibit printing of session and certificate information.
353 Sends a status message back to the client when it connects. This includes
354 information about the ciphers used and various session parameters.
355 The output is in HTML format so this option will normally be used with a
360 Emulates a simple web server. Pages will be resolved relative to the
361 current directory, for example if the URL https://myhost/page.html is
362 requested the file ./page.html will be loaded.
364 =item B<-tlsextdebug>
366 Print a hex dump of any TLS extensions received from the server.
370 Emulates a simple web server. Pages will be resolved relative to the
371 current directory, for example if the URL https://myhost/page.html is
372 requested the file ./page.html will be loaded. The files loaded are
373 assumed to contain a complete and correct HTTP response (lines that
374 are part of the HTTP response line and headers must end with CRLF).
376 =item B<-id_prefix val>
378 Generate SSL/TLS session IDs prefixed by B<val>. This is mostly useful
379 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
380 servers, when each of which might be generating a unique range of session
381 IDs (eg. with a certain prefix).
385 A file or files containing random data used to seed the random number
386 generator, or an EGD socket (see L<RAND_egd(3)>).
387 Multiple files can be specified separated by an OS-dependent character.
388 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
391 =item B<-verify_return_error>
393 Verification errors normally just print a message but allow the
394 connection to continue, for debugging purposes.
395 If this option is used, then verification errors close the connection.
399 Enables certificate status request support (aka OCSP stapling).
401 =item B<-status_verbose>
403 Enables certificate status request support (aka OCSP stapling) and gives
404 a verbose printout of the OCSP response.
406 =item B<-status_timeout int>
408 Sets the timeout for OCSP response to B<int> seconds.
410 =item B<-status_url val>
412 Sets a fallback responder URL to use if no responder URL is present in the
413 server certificate. Without this option an error is returned if the server
414 certificate does not contain a responder address.
416 =item B<-status_file infile>
418 Overrides any OCSP responder URLs from the certificate and always provides the
419 OCSP Response stored in the file. The file must be in DER format.
423 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
424 with B<enable-ssl-trace> for this option to work.
428 Provide a brief summary of connection parameters instead of the normal verbose
433 Simple test server which just reverses the text received from the client
434 and sends it back to the server. Also sets B<-brief>.
438 Switch on asynchronous mode. Cryptographic operations will be performed
439 asynchronously. This will only have an effect if an asynchronous capable engine
440 is also used via the B<-engine> option. For test purposes the dummy async engine
441 (dasync) can be used (if available).
443 =item B<-max_send_frag +int>
445 The maximum size of data fragment to send.
446 See L<SSL_CTX_set_max_send_fragment(3)> for further information.
448 =item B<-split_send_frag +int>
450 The size used to split data for encrypt pipelines. If more data is written in
451 one go than this value then it will be split into multiple pipelines, up to the
452 maximum number of pipelines defined by max_pipelines. This only has an effect if
453 a suitable cipher suite has been negotiated, an engine that supports pipelining
454 has been loaded, and max_pipelines is greater than 1. See
455 L<SSL_CTX_set_split_send_fragment(3)> for further information.
457 =item B<-max_pipelines +int>
459 The maximum number of encrypt/decrypt pipelines to be used. This will only have
460 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
461 engine) and a suitable cipher suite has been negotiated. The default value is 1.
462 See L<SSL_CTX_set_max_pipelines(3)> for further information.
464 =item B<-read_buf +int>
466 The default read buffer size to be used for connections. This will only have an
467 effect if the buffer size is larger than the size that would otherwise be used
468 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
469 further information).
471 =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>
473 These options require or disable the use of the specified SSL or TLS protocols.
474 By default B<s_server> will negotiate the highest mutually supported protocol
476 When a specific TLS version is required, only that version will be accepted
481 There are several known bug in SSL and TLS implementations. Adding this
482 option enables various workarounds.
486 Disable negotiation of TLS compression.
487 TLS compression is not recommended and is off by default as of
492 Enable negotiation of TLS compression.
493 This option was introduced in OpenSSL 1.1.0.
494 TLS compression is not recommended and is off by default as of
499 Disable RFC4507bis session ticket support.
503 Use the server's cipher preferences, rather than the client's preferences.
505 =item B<-no_resumption_on_reneg>
507 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
509 =item B<-client_sigalgs val>
511 Signature algorithms to support for client certificate authentication
512 (colon-separated list).
514 =item B<-named_curve val>
516 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
517 For a list of all possible curves, use:
519 $ openssl ecparam -list_curves
523 This allows the cipher list used by the server to be modified. When
524 the client sends a list of supported ciphers the first client cipher
525 also included in the server list is used. Because the client specifies
526 the preference order, the order of the server cipherlist irrelevant. See
527 the B<ciphers> command for more information.
529 =item B<-dhparam infile>
531 The DH parameter file to use. The ephemeral DH cipher suites generate keys
532 using a set of DH parameters. If not specified then an attempt is made to
533 load the parameters from the server certificate file.
534 If this fails then a static set of parameters hard coded into the B<s_server>
535 program will be used.
537 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
538 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
539 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
540 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
541 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
542 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
543 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
545 Set different peer certificate verification options.
546 See the L<verify(1)> manual page for details.
548 =item B<-crl_check>, B<-crl_check_all>
550 Check the peer certificate has not been revoked by its CA.
551 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
552 option all CRLs of all CAs in the chain are checked.
556 Turns on non blocking I/O.
558 =item B<-psk_identity val>
560 Expect the client to send PSK identity B<val> when using a PSK
561 cipher suite, and warn if they do not. By default, the expected PSK
562 identity is the string "Client_identity".
564 =item B<-psk_hint val>
566 Use the PSK identity hint B<val> when using a PSK cipher suite.
570 Use the PSK key B<val> when using a PSK cipher suite. The key is
571 given as a hexadecimal number without leading 0x, for example -psk
573 This option must be provided in order to use a PSK cipher.
577 This option can only be used in conjunction with one of the DTLS options above.
578 With this option B<s_server> will listen on a UDP port for incoming connections.
579 Any ClientHellos that arrive will be checked to see if they have a cookie in
581 Any without a cookie will be responded to with a HelloVerifyRequest.
582 If a ClientHello with a cookie is received then B<s_server> will connect to
583 that peer and complete the handshake.
585 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
587 These options make B<s_server> use DTLS protocols instead of TLS.
588 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
589 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
594 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
595 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
596 available where OpenSSL has support for SCTP enabled.
600 If this option is set then no DH parameters will be loaded effectively
601 disabling the ephemeral DH cipher suites.
603 =item B<-alpn val>, B<-nextprotoneg val>
605 These flags enable the Enable the Application-Layer Protocol Negotiation
606 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
607 IETF standard and replaces NPN.
608 The B<val> list is a comma-separated list of supported protocol
609 names. The list should contain the most desirable protocols first.
610 Protocol names are printable ASCII strings, for example "http/1.1" or
612 The flag B<-nextprotoneg> cannot be specified if B<-tls1_3> is used.
616 Specifying an engine (by its unique id string in B<val>) will cause B<s_server>
617 to attempt to obtain a functional reference to the specified engine,
618 thus initialising it if needed. The engine will then be set as the default
619 for all available algorithms.
621 =item B<-keylogfile outfile>
623 Appends TLS secrets to the specified keylog file such that external programs
624 (like Wireshark) can decrypt TLS connections.
626 =item B<-max_early_data int>
628 Change the default maximum early data bytes that are specified for new sessions
629 and any incoming early data (when used in conjunction with the B<-early_data>
630 flag). The default value is approximately 16k. The argument must be an integer
631 greater than or equal to 0.
635 Accept early data where possible.
639 =head1 CONNECTED COMMANDS
641 If a connection request is established with an SSL client and neither the
642 B<-www> nor the B<-WWW> option has been used then normally any data received
643 from the client is displayed and any key presses will be sent to the client.
645 Certain single letter commands are also recognized which perform special
646 operations: these are listed below.
652 End the current SSL connection but still accept new connections.
656 End the current SSL connection and exit.
660 Renegotiate the SSL session.
664 Renegotiate the SSL session and request a client certificate.
668 Send some plain text down the underlying TCP connection: this should
669 cause the client to disconnect due to a protocol violation.
673 Print out some session cache status information.
679 B<s_server> can be used to debug SSL clients. To accept connections from
680 a web browser the command:
682 openssl s_server -accept 443 -www
684 can be used for example.
686 Although specifying an empty list of CAs when requesting a client certificate
687 is strictly speaking a protocol violation, some SSL clients interpret this to
688 mean any CA is acceptable. This is useful for debugging purposes.
690 The session parameters can printed out using the B<sess_id> program.
694 Because this program has a lot of options and also because some of the
695 techniques used are rather old, the C source of B<s_server> is rather hard to
696 read and not a model of how things should be done.
697 A typical SSL server program would be much simpler.
699 The output of common ciphers is wrong: it just gives the list of ciphers that
700 OpenSSL recognizes and the client supports.
702 There should be a way for the B<s_server> program to print out details of any
703 unknown cipher suites a client says it supports.
707 L<SSL_CONF_cmd(3)>, L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
708 L<SSL_CTX_set_max_send_fragment(3)>, L<SSL_CTX_set_split_send_fragment(3)>
709 L<SSL_CTX_set_max_pipelines(3)>
713 The -no_alt_chains options was first added to OpenSSL 1.1.0.
717 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
719 Licensed under the OpenSSL license (the "License"). You may not use
720 this file except in compliance with the License. You can obtain a copy
721 in the file LICENSE in the source distribution or at
722 L<https://www.openssl.org/source/license.html>.