5 openssl-s_server - SSL/TLS server program
23 [B<-serverinfo> I<val>]
24 [B<-certform> B<DER>|B<PEM>]
26 [B<-keyform> I<format>]
29 [B<-dcertform> B<DER>|B<PEM>]
31 [B<-dkeyform> B<DER>|B<PEM>]
37 [B<-msgfile> I<outfile>]
39 [B<-CAfile> I<infile>]
45 [B<-no_resume_ephemeral>]
49 [B<-servername_fatal>]
54 [B<-id_prefix> I<val>]
56 [B<-writerand> I<file>]
57 [B<-keymatexport> I<val>]
58 [B<-keymatexportlen> I<+int>]
61 [B<-cert_chain> I<infile>]
62 [B<-dcert_chain> I<infile>]
63 [B<-chainCApath> I<dir>]
64 [B<-verifyCApath> I<dir>]
67 [B<-CRLform> B<DER>|B<PEM>]
68 [B<-verify_return_error>]
71 [B<-chainCAfile> I<infile>]
72 [B<-verifyCAfile> I<infile>]
77 [B<-status_timeout> I<int>]
78 [B<-status_url> I<val>]
79 [B<-status_file> I<infile>]
82 [B<-security_debug_verbose>]
86 [B<-ssl_config> I<val>]
87 [B<-max_send_frag> I<+int>]
88 [B<-split_send_frag> I<+int>]
89 [B<-max_pipelines> I<+int>]
90 [B<-read_buf> I<+int>]
102 [B<-legacy_renegotiation>]
103 [B<-no_renegotiation>]
104 [B<-legacy_server_connect>]
105 [B<-no_resumption_on_reneg>]
106 [B<-no_legacy_server_connect>]
107 [B<-allow_no_dhe_kex>]
108 [B<-prioritize_chacha>]
111 [B<-client_sigalgs> I<val>]
114 [B<-named_curve> I<val>]
116 [B<-ciphersuites> I<val>]
117 [B<-dhparam> I<infile>]
118 [B<-record_padding> I<val>]
119 [B<-debug_broken_protocol>]
122 [B<-verify_name> I<val>]
123 [B<-verify_depth> I<int>]
124 [B<-auth_level> I<int>]
125 [B<-attime> I<intmax>]
126 [B<-verify_hostname> I<val>]
127 [B<-verify_email> I<val>]
129 [B<-ignore_critical>]
134 [B<-explicit_policy>]
143 [B<-suiteB_128_only>]
149 [B<-allow_proxy_certs>]
154 [B<-xcertform> B<DER>|B<PEM>]
155 [B<-xkeyform> B<DER>|B<PEM>]
157 [B<-psk_identity> I<val>]
158 [B<-psk_hint> I<val>]
160 [B<-psk_session> I<file>]
161 [B<-srpvfile> I<infile>]
162 [B<-srpuserseed> I<val>]
177 [B<-nextprotoneg> I<val>]
178 [B<-use_srtp> I<val>]
181 [B<-keylogfile> I<outfile>]
182 [B<-max_early_data> I<int>]
186 [B<-http_server_binmode>]
188 =for comment ifdef unix 4 6 unlink no_dhe nextprotoneg use_srtp engine
190 =for comment ifdef status status_verbose status_timeout status_url status_file
192 =for comment ifdef psk_hint srpvfile srpuserseed sctp sctp_label_bug
194 =for comment ifdef sctp sctp_label_bug trace mtu timeout listen
196 =for comment ifdef ssl3 tls1 tls1_1 tls1_2 tls1_3 dtls mtu dtls1 dtls1_2
200 The B<s_server> command implements a generic SSL/TLS server which listens
201 for connections on a given port using SSL/TLS.
205 In addition to the options below the B<s_server> utility also supports the
206 common and server only options documented
207 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
214 Print out a usage message.
216 =item B<-port> I<+int>
218 The TCP port to listen on for connections. If not specified 4433 is used.
220 =item B<-accept> I<val>
222 The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
224 =item B<-unix> I<val>
226 Unix domain socket to accept on.
238 For -unix, unlink any existing socket first.
240 =item B<-context> I<val>
242 Sets the SSL context id. It can be given any string value. If this option
243 is not present a default value will be used.
245 =item B<-verify> I<int>, B<-Verify> I<int>
247 The verify depth to use. This specifies the maximum length of the
248 client certificate chain and makes the server request a certificate from
249 the client. With the B<-verify> option a certificate is requested but the
250 client does not have to send one, with the B<-Verify> option the client
251 must supply a certificate or an error occurs.
253 If the cipher suite cannot request a client certificate (for example an
254 anonymous cipher suite or PSK) this option has no effect.
256 =item B<-cert> I<infile>
258 The certificate to use, most servers cipher suites require the use of a
259 certificate and some require a certificate with a certain public key type:
260 for example the DSS cipher suites require a certificate containing a DSS
261 (DSA) key. If not specified then the filename "server.pem" will be used.
265 A file containing trusted certificates to use when attempting to build the
266 client/server certificate chain related to the certificate specified via the
269 =item B<-build_chain>
271 Specify whether the application should build the certificate chain to be
272 provided to the client.
274 =item B<-nameopt> I<val>
276 Option which determines how the subject or issuer names are displayed. The
277 B<val> argument can be a single option or multiple options separated by
278 commas. Alternatively the B<-nameopt> switch may be used more than once to
279 set multiple options. See the L<x509(1)> manual page for details.
281 =item B<-naccept> I<+int>
283 The server will exit after receiving the specified number of connections,
286 =item B<-serverinfo> I<val>
288 A file containing one or more blocks of PEM data. Each PEM block
289 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
290 followed by "length" bytes of extension data). If the client sends
291 an empty TLS ClientHello extension matching the type, the corresponding
292 ServerHello extension will be returned.
294 =item B<-certform> B<DER>|B<PEM>
296 The certificate format to use: DER or PEM. PEM is the default.
298 =item B<-key> I<infile>
300 The private key to use. If not specified then the certificate file will
303 =item B<-keyform> I<format>
305 The private format to use: DER or PEM. PEM is the default.
307 =item B<-pass> I<val>
309 The private key password source. For more information about the format of B<val>
310 see L<openssl(1)/Pass phrase options>.
312 =item B<-dcert> I<infile>, B<-dkey> I<infile>
314 Specify an additional certificate and private key, these behave in the
315 same manner as the B<-cert> and B<-key> options except there is no default
316 if they are not specified (no additional certificate and key is used). As
317 noted above some cipher suites require a certificate containing a key of
318 a certain type. Some cipher suites need a certificate carrying an RSA key
319 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
320 a server can support clients which only support RSA or DSS cipher suites
321 by using an appropriate certificate.
323 =item B<-dcert_chain>
325 A file containing trusted certificates to use when attempting to build the
326 server certificate chain when a certificate specified via the B<-dcert> option
329 =item B<-dcertform> B<DER>|B<PEM>, B<-dkeyform> B<DER>|B<PEM>, B<-dpass> I<val>
331 Additional certificate and private key format and passphrase respectively.
333 =item B<-xkey> I<infile>, B<-xcert> I<infile>, B<-xchain>
335 Specify an extra certificate, private key and certificate chain. These behave
336 in the same manner as the B<-cert>, B<-key> and B<-cert_chain> options. When
337 specified, the callback returning the first valid chain will be in use by
340 =item B<-xchain_build>
342 Specify whether the application should build the certificate chain to be
343 provided to the client for the extra certificates provided via B<-xkey> I<infile>,
344 B<-xcert> I<infile>, B<-xchain> options.
346 =item B<-xcertform> B<DER>|B<PEM>, B<-xkeyform> B<DER>|B<PEM>
348 Extra certificate and private key format respectively.
352 Tests non blocking I/O.
356 This option translated a line feed from the terminal into CR+LF.
360 Print extensive debugging information including a hex dump of all traffic.
364 Show all protocol messages with hex dump.
366 =item B<-msgfile> I<outfile>
368 File to send output of B<-msg> or B<-trace> to, default standard output.
372 Prints the SSL session states.
374 =item B<-CAfile> I<infile>
376 A file containing trusted certificates to use during client authentication
377 and to use when attempting to build the server certificate chain. The list
378 is also used in the list of acceptable client CAs passed to the client when
379 a certificate is requested.
381 =item B<-CApath> I<dir>
383 The directory to use for client certificate verification. This directory
384 must be in "hash format", see L<verify(1)> for more information. These are
385 also used when building the server certificate chain.
387 =item B<-chainCApath> I<dir>
389 The directory to use for building the chain provided to the client. This
390 directory must be in "hash format", see L<verify(1)> for more information.
392 =item B<-chainCAfile> I<file>
394 A file containing trusted certificates to use when attempting to build the
395 server certificate chain.
399 Do not load the trusted CA certificates from the default file location.
403 Do not load the trusted CA certificates from the default directory location.
407 If this option is set then no certificate is used. This restricts the
408 cipher suites available to the anonymous ones (currently just anonymous
413 Inhibit printing of session and certificate information.
417 Sends a status message back to the client when it connects. This includes
418 information about the ciphers used and various session parameters.
419 The output is in HTML format so this option will normally be used with a
420 web browser. Cannot be used in conjunction with B<-early_data>.
424 Emulates a simple web server. Pages will be resolved relative to the
425 current directory, for example if the URL https://myhost/page.html is
426 requested the file ./page.html will be loaded. Cannot be used in conjunction
429 =item B<-tlsextdebug>
431 Print a hex dump of any TLS extensions received from the server.
435 Emulates a simple web server. Pages will be resolved relative to the
436 current directory, for example if the URL https://myhost/page.html is
437 requested the file ./page.html will be loaded. The files loaded are
438 assumed to contain a complete and correct HTTP response (lines that
439 are part of the HTTP response line and headers must end with CRLF). Cannot be
440 used in conjunction with B<-early_data>.
442 =item B<-id_prefix> I<val>
444 Generate SSL/TLS session IDs prefixed by B<val>. This is mostly useful
445 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
446 servers, when each of which might be generating a unique range of session
447 IDs (eg. with a certain prefix).
449 =item B<-rand> I<file...>
451 A file or files containing random data used to seed the random number
453 Multiple files can be specified separated by an OS-dependent character.
454 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
457 =item B<-writerand> I<file>
459 Writes random data to the specified I<file> upon exit.
460 This can be used with a subsequent B<-rand> flag.
462 =item B<-verify_return_error>
464 Verification errors normally just print a message but allow the
465 connection to continue, for debugging purposes.
466 If this option is used, then verification errors close the connection.
470 Enables certificate status request support (aka OCSP stapling).
472 =item B<-status_verbose>
474 Enables certificate status request support (aka OCSP stapling) and gives
475 a verbose printout of the OCSP response.
477 =item B<-status_timeout> I<int>
479 Sets the timeout for OCSP response to B<int> seconds.
481 =item B<-status_url> I<val>
483 Sets a fallback responder URL to use if no responder URL is present in the
484 server certificate. Without this option an error is returned if the server
485 certificate does not contain a responder address.
487 =item B<-status_file> I<infile>
489 Overrides any OCSP responder URLs from the certificate and always provides the
490 OCSP Response stored in the file. The file must be in DER format.
494 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
495 with B<enable-ssl-trace> for this option to work.
499 Provide a brief summary of connection parameters instead of the normal verbose
504 Simple test server which just reverses the text received from the client
505 and sends it back to the server. Also sets B<-brief>. Cannot be used in
506 conjunction with B<-early_data>.
510 Switch on asynchronous mode. Cryptographic operations will be performed
511 asynchronously. This will only have an effect if an asynchronous capable engine
512 is also used via the B<-engine> option. For test purposes the dummy async engine
513 (dasync) can be used (if available).
515 =item B<-max_send_frag> I<+int>
517 The maximum size of data fragment to send.
518 See L<SSL_CTX_set_max_send_fragment(3)> for further information.
520 =item B<-split_send_frag> I<+int>
522 The size used to split data for encrypt pipelines. If more data is written in
523 one go than this value then it will be split into multiple pipelines, up to the
524 maximum number of pipelines defined by max_pipelines. This only has an effect if
525 a suitable cipher suite has been negotiated, an engine that supports pipelining
526 has been loaded, and max_pipelines is greater than 1. See
527 L<SSL_CTX_set_split_send_fragment(3)> for further information.
529 =item B<-max_pipelines> I<+int>
531 The maximum number of encrypt/decrypt pipelines to be used. This will only have
532 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
533 engine) and a suitable cipher suite has been negotiated. The default value is 1.
534 See L<SSL_CTX_set_max_pipelines(3)> for further information.
536 =item B<-read_buf> I<+int>
538 The default read buffer size to be used for connections. This will only have an
539 effect if the buffer size is larger than the size that would otherwise be used
540 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
541 further information).
543 =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>
545 These options require or disable the use of the specified SSL or TLS protocols.
546 By default B<s_server> will negotiate the highest mutually supported protocol
548 When a specific TLS version is required, only that version will be accepted
550 Note that not all protocols and flags may be available, depending on how
555 There are several known bugs in SSL and TLS implementations. Adding this
556 option enables various workarounds.
560 Disable negotiation of TLS compression.
561 TLS compression is not recommended and is off by default as of
566 Enable negotiation of TLS compression.
567 This option was introduced in OpenSSL 1.1.0.
568 TLS compression is not recommended and is off by default as of
573 Disable RFC4507bis session ticket support. This option has no effect if TLSv1.3
574 is negotiated. See B<-num_tickets>.
576 =item B<-num_tickets>
578 Control the number of tickets that will be sent to the client after a full
579 handshake in TLSv1.3. The default number of tickets is 2. This option does not
580 affect the number of tickets sent after a resumption handshake.
584 Use the server's cipher preferences, rather than the client's preferences.
586 =item B<-prioritize_chacha>
588 Prioritize ChaCha ciphers when preferred by clients. Requires B<-serverpref>.
590 =item B<-no_resumption_on_reneg>
592 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
594 =item B<-client_sigalgs> I<val>
596 Signature algorithms to support for client certificate authentication
597 (colon-separated list).
599 =item B<-named_curve> I<val>
601 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
602 For a list of all possible curves, use:
604 $ openssl ecparam -list_curves
606 =item B<-cipher> I<val>
608 This allows the list of TLSv1.2 and below ciphersuites used by the server to be
609 modified. This list is combined with any TLSv1.3 ciphersuites that have been
610 configured. When the client sends a list of supported ciphers the first client
611 cipher also included in the server list is used. Because the client specifies
612 the preference order, the order of the server cipherlist is irrelevant. See
613 the B<ciphers> command for more information.
615 =item B<-ciphersuites> I<val>
617 This allows the list of TLSv1.3 ciphersuites used by the server to be modified.
618 This list is combined with any TLSv1.2 and below ciphersuites that have been
619 configured. When the client sends a list of supported ciphers the first client
620 cipher also included in the server list is used. Because the client specifies
621 the preference order, the order of the server cipherlist is irrelevant. See
622 the B<ciphers> command for more information. The format for this list is a
623 simple colon (":") separated list of TLSv1.3 ciphersuite names.
625 =item B<-dhparam> I<infile>
627 The DH parameter file to use. The ephemeral DH cipher suites generate keys
628 using a set of DH parameters. If not specified then an attempt is made to
629 load the parameters from the server certificate file.
630 If this fails then a static set of parameters hard coded into the B<s_server>
631 program will be used.
633 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
634 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
635 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
636 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
637 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
638 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
639 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
641 Set different peer certificate verification options.
642 See the L<verify(1)> manual page for details.
644 =item B<-crl_check>, B<-crl_check_all>
646 Check the peer certificate has not been revoked by its CA.
647 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
648 option all CRLs of all CAs in the chain are checked.
652 Turns on non blocking I/O.
654 =item B<-psk_identity> I<val>
656 Expect the client to send PSK identity B<val> when using a PSK
657 cipher suite, and warn if they do not. By default, the expected PSK
658 identity is the string "Client_identity".
660 =item B<-psk_hint> I<val>
662 Use the PSK identity hint B<val> when using a PSK cipher suite.
666 Use the PSK key B<val> when using a PSK cipher suite. The key is
667 given as a hexadecimal number without leading 0x, for example -psk
669 This option must be provided in order to use a PSK cipher.
671 =item B<-psk_session> I<file>
673 Use the pem encoded SSL_SESSION data stored in B<file> as the basis of a PSK.
674 Note that this will only work if TLSv1.3 is negotiated.
678 This option can only be used in conjunction with one of the DTLS options above.
679 With this option B<s_server> will listen on a UDP port for incoming connections.
680 Any ClientHellos that arrive will be checked to see if they have a cookie in
682 Any without a cookie will be responded to with a HelloVerifyRequest.
683 If a ClientHello with a cookie is received then B<s_server> will connect to
684 that peer and complete the handshake.
686 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
688 These options make B<s_server> use DTLS protocols instead of TLS.
689 With B<-dtls>, B<s_server> will negotiate any supported DTLS protocol version,
690 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
695 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
696 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
697 available where OpenSSL has support for SCTP enabled.
699 =item B<-sctp_label_bug>
701 Use the incorrect behaviour of older OpenSSL implementations when computing
702 endpoint-pair shared secrets for DTLS/SCTP. This allows communication with
703 older broken implementations but breaks interoperability with correct
704 implementations. Must be used in conjunction with B<-sctp>. This option is only
705 available where OpenSSL has support for SCTP enabled.
709 If this option is set then no DH parameters will be loaded effectively
710 disabling the ephemeral DH cipher suites.
712 =item B<-alpn> I<val>, B<-nextprotoneg> I<val>
714 These flags enable the Enable the Application-Layer Protocol Negotiation
715 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
716 IETF standard and replaces NPN.
717 The B<val> list is a comma-separated list of supported protocol
718 names. The list should contain the most desirable protocols first.
719 Protocol names are printable ASCII strings, for example "http/1.1" or
721 The flag B<-nextprotoneg> cannot be specified if B<-tls1_3> is used.
723 =item B<-engine> I<val>
725 Specifying an engine (by its unique id string in B<val>) will cause B<s_server>
726 to attempt to obtain a functional reference to the specified engine,
727 thus initialising it if needed. The engine will then be set as the default
728 for all available algorithms.
730 =item B<-keylogfile> I<outfile>
732 Appends TLS secrets to the specified keylog file such that external programs
733 (like Wireshark) can decrypt TLS connections.
735 =item B<-max_early_data> I<int>
737 Change the default maximum early data bytes that are specified for new sessions
738 and any incoming early data (when used in conjunction with the B<-early_data>
739 flag). The default value is approximately 16k. The argument must be an integer
740 greater than or equal to 0.
744 Accept early data where possible. Cannot be used in conjunction with B<-www>,
745 B<-WWW>, B<-HTTP> or B<-rev>.
747 =item B<-anti_replay>, B<-no_anti_replay>
749 Switches replay protection on or off, respectively. Replay protection is on by
750 default unless overridden by a configuration file. When it is on, OpenSSL will
751 automatically detect if a session ticket has been used more than once, TLSv1.3
752 has been negotiated, and early data is enabled on the server. A full handshake
753 is forced if a session ticket is used a second or subsequent time. Any early
754 data that was sent will be rejected.
756 =item B<-http_server_binmode>
758 When acting as web-server (using option B<-WWW> or B<-HTTP>) open files requested
759 by the client in binary mode.
763 =head1 CONNECTED COMMANDS
765 If a connection request is established with an SSL client and neither the
766 B<-www> nor the B<-WWW> option has been used then normally any data received
767 from the client is displayed and any key presses will be sent to the client.
769 Certain commands are also recognized which perform special operations. These
770 commands are a letter which must appear at the start of a line. They are listed
777 End the current SSL connection but still accept new connections.
781 End the current SSL connection and exit.
785 Renegotiate the SSL session (TLSv1.2 and below only).
789 Renegotiate the SSL session and request a client certificate (TLSv1.2 and below
794 Send some plain text down the underlying TCP connection: this should
795 cause the client to disconnect due to a protocol violation.
799 Print out some session cache status information.
803 Send a key update message to the client (TLSv1.3 only)
807 Send a key update message to the client and request one back (TLSv1.3 only)
811 Send a certificate request to the client (TLSv1.3 only)
817 B<s_server> can be used to debug SSL clients. To accept connections from
818 a web browser the command:
820 openssl s_server -accept 443 -www
822 can be used for example.
824 Although specifying an empty list of CAs when requesting a client certificate
825 is strictly speaking a protocol violation, some SSL clients interpret this to
826 mean any CA is acceptable. This is useful for debugging purposes.
828 The session parameters can printed out using the B<sess_id> program.
832 Because this program has a lot of options and also because some of the
833 techniques used are rather old, the C source of B<s_server> is rather hard to
834 read and not a model of how things should be done.
835 A typical SSL server program would be much simpler.
837 The output of common ciphers is wrong: it just gives the list of ciphers that
838 OpenSSL recognizes and the client supports.
840 There should be a way for the B<s_server> program to print out details of any
841 unknown cipher suites a client says it supports.
846 L<openssl-sess_id(1)>,
847 L<openssl-s_client(1)>,
848 L<openssl-ciphers(1)>,
850 L<SSL_CTX_set_max_send_fragment(3)>,
851 L<SSL_CTX_set_split_send_fragment(3)>,
852 L<SSL_CTX_set_max_pipelines(3)>
856 The -no_alt_chains option was added in OpenSSL 1.1.0.
859 -allow-no-dhe-kex and -prioritize_chacha options were added in OpenSSL 1.1.1.
863 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
865 Licensed under the Apache License 2.0 (the "License"). You may not use
866 this file except in compliance with the License. You can obtain a copy
867 in the file LICENSE in the source distribution or at
868 L<https://www.openssl.org/source/license.html>.