1S_SERVER(1) OpenSSL S_SERVER(1)
2
6 openssl-s_server, s_server - SSL/TLS server program
7
9 openssl s_server [-help] [-port +int] [-accept val] [-unix val] [-4]
10 [-6] [-unlink] [-context val] [-verify int] [-Verify int] [-cert
11 infile] [-nameopt val] [-naccept +int] [-serverinfo val] [-certform
12 PEM|DER] [-key infile] [-keyform format] [-pass val] [-dcert infile]
13 [-dcertform PEM|DER] [-dkey infile] [-dkeyform PEM|DER] [-dpass val]
14 [-nbio_test] [-crlf] [-debug] [-msg] [-msgfile outfile] [-state]
15 [-CAfile infile] [-CApath dir] [-no-CAfile] [-no-CApath] [-nocert]
16 [-quiet] [-no_resume_ephemeral] [-www] [-WWW] [-servername]
17 [-servername_fatal] [-cert2 infile] [-key2 infile] [-tlsextdebug]
18 [-HTTP] [-id_prefix val] [-rand file...] [-writerand file]
19 [-keymatexport val] [-keymatexportlen +int] [-CRL infile]
20 [-crl_download] [-cert_chain infile] [-dcert_chain infile]
21 [-chainCApath dir] [-verifyCApath dir] [-no_cache] [-ext_cache]
22 [-CRLform PEM|DER] [-verify_return_error] [-verify_quiet]
23 [-build_chain] [-chainCAfile infile] [-verifyCAfile infile] [-ign_eof]
24 [-no_ign_eof] [-status] [-status_verbose] [-status_timeout int]
25 [-status_url val] [-status_file infile] [-trace] [-security_debug]
26 [-security_debug_verbose] [-brief] [-rev] [-async] [-ssl_config val]
27 [-max_send_frag +int] [-split_send_frag +int] [-max_pipelines +int]
28 [-read_buf +int] [-no_ssl3] [-no_tls1] [-no_tls1_1] [-no_tls1_2]
29 [-no_tls1_3] [-bugs] [-no_comp] [-comp] [-no_ticket] [-num_tickets]
30 [-serverpref] [-legacy_renegotiation] [-no_renegotiation]
31 [-legacy_server_connect] [-no_resumption_on_reneg]
32 [-no_legacy_server_connect] [-allow_no_dhe_kex] [-prioritize_chacha]
33 [-strict] [-sigalgs val] [-client_sigalgs val] [-groups val] [-curves
34 val] [-named_curve val] [-cipher val] [-ciphersuites val] [-dhparam
35 infile] [-record_padding val] [-debug_broken_protocol] [-policy val]
36 [-purpose val] [-verify_name val] [-verify_depth int] [-auth_level int]
37 [-attime intmax] [-verify_hostname val] [-verify_email val]
38 [-verify_ip] [-ignore_critical] [-issuer_checks] [-crl_check]
39 [-crl_check_all] [-policy_check] [-explicit_policy] [-inhibit_any]
40 [-inhibit_map] [-x509_strict] [-extended_crl] [-use_deltas]
41 [-policy_print] [-check_ss_sig] [-trusted_first] [-suiteB_128_only]
42 [-suiteB_128] [-suiteB_192] [-partial_chain] [-no_alt_chains]
43 [-no_check_time] [-allow_proxy_certs] [-xkey] [-xcert] [-xchain]
44 [-xchain_build] [-xcertform PEM|DER] [-xkeyform PEM|DER] [-nbio]
45 [-psk_identity val] [-psk_hint val] [-psk val] [-psk_session file]
46 [-srpvfile infile] [-srpuserseed val] [-ssl3] [-tls1] [-tls1_1]
47 [-tls1_2] [-tls1_3] [-dtls] [-timeout] [-mtu +int] [-listen] [-dtls1]
48 [-dtls1_2] [-sctp] [-sctp_label_bug] [-no_dhe] [-nextprotoneg val]
49 [-use_srtp val] [-alpn val] [-engine val] [-keylogfile outfile]
50 [-max_early_data int] [-early_data] [-anti_replay] [-no_anti_replay]
51
53 The s_server command implements a generic SSL/TLS server which listens
54 for connections on a given port using SSL/TLS.
55
57 In addition to the options below the s_server utility also supports the
58 common and server only options documented in the "Supported Command
59 Line Commands" section of the SSL_CONF_cmd(3) manual page.
60 -help
62 Print out a usage message.
63 -port +int
65 The TCP port to listen on for connections. If not specified 4433 is
66 used.
67 -accept val
69 The optional TCP host and port to listen on for connections. If not
70 specified, *:4433 is used.
71 -unix val
73 Unix domain socket to accept on.
74 -4 Use IPv4 only.
76 -6 Use IPv6 only.
78 -unlink
80 For -unix, unlink any existing socket first.
81 -context val
83 Sets the SSL context id. It can be given any string value. If this
84 option is not present a default value will be used.
85 -verify int, -Verify int
87 The verify depth to use. This specifies the maximum length of the
88 client certificate chain and makes the server request a certificate
89 from the client. With the -verify option a certificate is requested
90 but the client does not have to send one, with the -Verify option
91 the client must supply a certificate or an error occurs.
92 If the cipher suite cannot request a client certificate (for
94 example an anonymous cipher suite or PSK) this option has no
95 effect.
96 -cert infile
98 The certificate to use, most servers cipher suites require the use
99 of a certificate and some require a certificate with a certain
100 public key type: for example the DSS cipher suites require a
101 certificate containing a DSS (DSA) key. If not specified then the
102 filename "server.pem" will be used.
103 -cert_chain
105 A file containing trusted certificates to use when attempting to
106 build the client/server certificate chain related to the
107 certificate specified via the -cert option.
108 -build_chain
110 Specify whether the application should build the certificate chain
111 to be provided to the client.
112 -nameopt val
114 Option which determines how the subject or issuer names are
115 displayed. The val argument can be a single option or multiple
116 options separated by commas. Alternatively the -nameopt switch may
117 be used more than once to set multiple options. See the x509(1)
118 manual page for details.
119 -naccept +int
121 The server will exit after receiving the specified number of
122 connections, default unlimited.
123 -serverinfo val
125 A file containing one or more blocks of PEM data. Each PEM block
126 must encode a TLS ServerHello extension (2 bytes type, 2 bytes
127 length, followed by "length" bytes of extension data). If the
128 client sends an empty TLS ClientHello extension matching the type,
129 the corresponding ServerHello extension will be returned.
130 -certform PEM|DER
132 The certificate format to use: DER or PEM. PEM is the default.
133 -key infile
135 The private key to use. If not specified then the certificate file
136 will be used.
137 -keyform format
139 The private format to use: DER or PEM. PEM is the default.
140 -pass val
142 The private key password source. For more information about the
143 format of val see "Pass Phrase Options" in openssl(1).
144 -dcert infile, -dkey infile
146 Specify an additional certificate and private key, these behave in
147 the same manner as the -cert and -key options except there is no
148 default if they are not specified (no additional certificate and
149 key is used). As noted above some cipher suites require a
150 certificate containing a key of a certain type. Some cipher suites
151 need a certificate carrying an RSA key and some a DSS (DSA) key. By
152 using RSA and DSS certificates and keys a server can support
153 clients which only support RSA or DSS cipher suites by using an
154 appropriate certificate.
155 -dcert_chain
157 A file containing trusted certificates to use when attempting to
158 build the server certificate chain when a certificate specified via
159 the -dcert option is in use.
160 -dcertform PEM|DER, -dkeyform PEM|DER, -dpass val
162 Additional certificate and private key format and passphrase
163 respectively.
164 -xkey infile, -xcert infile, -xchain
166 Specify an extra certificate, private key and certificate chain.
167 These behave in the same manner as the -cert, -key and -cert_chain
168 options. When specified, the callback returning the first valid
169 chain will be in use by the server.
170 -xchain_build
172 Specify whether the application should build the certificate chain
173 to be provided to the client for the extra certificates provided
174 via -xkey infile, -xcert infile, -xchain options.
175 -xcertform PEM|DER, -xkeyform PEM|DER
177 Extra certificate and private key format respectively.
178 -nbio_test
180 Tests non blocking I/O.
181 -crlf
183 This option translated a line feed from the terminal into CR+LF.
184 -debug
186 Print extensive debugging information including a hex dump of all
187 traffic.
188 -msg
190 Show all protocol messages with hex dump.
191 -msgfile outfile
193 File to send output of -msg or -trace to, default standard output.
194 -state
196 Prints the SSL session states.
197 -CAfile infile
199 A file containing trusted certificates to use during client
200 authentication and to use when attempting to build the server
201 certificate chain. The list is also used in the list of acceptable
202 client CAs passed to the client when a certificate is requested.
203 -CApath dir
205 The directory to use for client certificate verification. This
206 directory must be in "hash format", see verify(1) for more
207 information. These are also used when building the server
208 certificate chain.
209 -chainCApath dir
211 The directory to use for building the chain provided to the client.
212 This directory must be in "hash format", see verify(1) for more
213 information.
214 -chainCAfile file
216 A file containing trusted certificates to use when attempting to
217 build the server certificate chain.
218 -no-CAfile
220 Do not load the trusted CA certificates from the default file
221 location.
222 -no-CApath
224 Do not load the trusted CA certificates from the default directory
225 location.
226 -nocert
228 If this option is set then no certificate is used. This restricts
229 the cipher suites available to the anonymous ones (currently just
230 anonymous DH).
231 -quiet
233 Inhibit printing of session and certificate information.
234 -www
236 Sends a status message back to the client when it connects. This
237 includes information about the ciphers used and various session
238 parameters. The output is in HTML format so this option will
239 normally be used with a web browser. Cannot be used in conjunction
240 with -early_data.
241 -WWW
243 Emulates a simple web server. Pages will be resolved relative to
244 the current directory, for example if the URL
245 https://myhost/page.html is requested the file ./page.html will be
246 loaded. Cannot be used in conjunction with -early_data.
247 -tlsextdebug
249 Print a hex dump of any TLS extensions received from the server.
250 -HTTP
252 Emulates a simple web server. Pages will be resolved relative to
253 the current directory, for example if the URL
254 https://myhost/page.html is requested the file ./page.html will be
255 loaded. The files loaded are assumed to contain a complete and
256 correct HTTP response (lines that are part of the HTTP response
257 line and headers must end with CRLF). Cannot be used in conjunction
258 with -early_data.
259 -id_prefix val
261 Generate SSL/TLS session IDs prefixed by val. This is mostly useful
262 for testing any SSL/TLS code (e.g. proxies) that wish to deal with
263 multiple servers, when each of which might be generating a unique
264 range of session IDs (e.g. with a certain prefix).
265 -rand file...
267 A file or files containing random data used to seed the random
268 number generator. Multiple files can be specified separated by an
269 OS-dependent character. The separator is ; for MS-Windows, , for
270 OpenVMS, and : for all others.
271 [-writerand file]
273 Writes random data to the specified file upon exit. This can be
274 used with a subsequent -rand flag.
275 -verify_return_error
277 Verification errors normally just print a message but allow the
278 connection to continue, for debugging purposes. If this option is
279 used, then verification errors close the connection.
280 -status
282 Enables certificate status request support (aka OCSP stapling).
283 -status_verbose
285 Enables certificate status request support (aka OCSP stapling) and
286 gives a verbose printout of the OCSP response.
287 -status_timeout int
289 Sets the timeout for OCSP response to int seconds.
290 -status_url val
292 Sets a fallback responder URL to use if no responder URL is present
293 in the server certificate. Without this option an error is returned
294 if the server certificate does not contain a responder address.
295 -status_file infile
297 Overrides any OCSP responder URLs from the certificate and always
298 provides the OCSP Response stored in the file. The file must be in
299 DER format.
300 -trace
302 Show verbose trace output of protocol messages. OpenSSL needs to be
303 compiled with enable-ssl-trace for this option to work.
304 -brief
306 Provide a brief summary of connection parameters instead of the
307 normal verbose output.
308 -rev
310 Simple test server which just reverses the text received from the
311 client and sends it back to the server. Also sets -brief. Cannot be
312 used in conjunction with -early_data.
313 -async
315 Switch on asynchronous mode. Cryptographic operations will be
316 performed asynchronously. This will only have an effect if an
317 asynchronous capable engine is also used via the -engine option.
318 For test purposes the dummy async engine (dasync) can be used (if
319 available).
320 -max_send_frag +int
322 The maximum size of data fragment to send. See
323 SSL_CTX_set_max_send_fragment(3) for further information.
324 -split_send_frag +int
326 The size used to split data for encrypt pipelines. If more data is
327 written in one go than this value then it will be split into
328 multiple pipelines, up to the maximum number of pipelines defined
329 by max_pipelines. This only has an effect if a suitable cipher
330 suite has been negotiated, an engine that supports pipelining has
331 been loaded, and max_pipelines is greater than 1. See
332 SSL_CTX_set_split_send_fragment(3) for further information.
333 -max_pipelines +int
335 The maximum number of encrypt/decrypt pipelines to be used. This
336 will only have an effect if an engine has been loaded that supports
337 pipelining (e.g. the dasync engine) and a suitable cipher suite has
338 been negotiated. The default value is 1. See
339 SSL_CTX_set_max_pipelines(3) for further information.
340 -read_buf +int
342 The default read buffer size to be used for connections. This will
343 only have an effect if the buffer size is larger than the size that
344 would otherwise be used and pipelining is in use (see
345 SSL_CTX_set_default_read_buffer_len(3) for further information).
346 -ssl2, -ssl3, -tls1, -tls1_1, -tls1_2, -tls1_3, -no_ssl2, -no_ssl3,
348 -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3
349 These options require or disable the use of the specified SSL or
350 TLS protocols. By default s_server will negotiate the highest
351 mutually supported protocol version. When a specific TLS version
352 is required, only that version will be accepted from the client.
353 Note that not all protocols and flags may be available, depending
354 on how OpenSSL was built.
355 -bugs
357 There are several known bugs in SSL and TLS implementations. Adding
358 this option enables various workarounds.
359 -no_comp
361 Disable negotiation of TLS compression. TLS compression is not
362 recommended and is off by default as of OpenSSL 1.1.0.
363 -comp
365 Enable negotiation of TLS compression. This option was introduced
366 in OpenSSL 1.1.0. TLS compression is not recommended and is off by
367 default as of OpenSSL 1.1.0.
368 -no_ticket
370 Disable RFC4507bis session ticket support. This option has no
371 effect if TLSv1.3 is negotiated. See -num_tickets.
372 -num_tickets
374 Control the number of tickets that will be sent to the client after
375 a full handshake in TLSv1.3. The default number of tickets is 2.
376 This option does not affect the number of tickets sent after a
377 resumption handshake.
378 -serverpref
380 Use the server's cipher preferences, rather than the client's
381 preferences.
382 -prioritize_chacha
384 Prioritize ChaCha ciphers when preferred by clients. Requires
385 -serverpref.
386 -no_resumption_on_reneg
388 Set the SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION option.
389 -client_sigalgs val
391 Signature algorithms to support for client certificate
392 authentication (colon-separated list).
393 -named_curve val
395 Specifies the elliptic curve to use. NOTE: this is single curve,
396 not a list. For a list of all possible curves, use:
397 $ openssl ecparam -list_curves
399 -cipher val
401 This allows the list of TLSv1.2 and below ciphersuites used by the
402 server to be modified. This list is combined with any TLSv1.3
403 ciphersuites that have been configured. When the client sends a
404 list of supported ciphers the first client cipher also included in
405 the server list is used. Because the client specifies the
406 preference order, the order of the server cipherlist is irrelevant.
407 See the ciphers command for more information.
408 -ciphersuites val
410 This allows the list of TLSv1.3 ciphersuites used by the server to
411 be modified. This list is combined with any TLSv1.2 and below
412 ciphersuites that have been configured. When the client sends a
413 list of supported ciphers the first client cipher also included in
414 the server list is used. Because the client specifies the
415 preference order, the order of the server cipherlist is irrelevant.
416 See the ciphers command for more information. The format for this
417 list is a simple colon (":") separated list of TLSv1.3 ciphersuite
418 names.
419 -dhparam infile
421 The DH parameter file to use. The ephemeral DH cipher suites
422 generate keys using a set of DH parameters. If not specified then
423 an attempt is made to load the parameters from the server
424 certificate file. If this fails then a static set of parameters
425 hard coded into the s_server program will be used.
426 -attime, -check_ss_sig, -crl_check, -crl_check_all, -explicit_policy,
428 -extended_crl, -ignore_critical, -inhibit_any, -inhibit_map,
429 -no_alt_chains, -no_check_time, -partial_chain, -policy, -policy_check,
430 -policy_print, -purpose, -suiteB_128, -suiteB_128_only, -suiteB_192,
431 -trusted_first, -use_deltas, -auth_level, -verify_depth, -verify_email,
432 -verify_hostname, -verify_ip, -verify_name, -x509_strict
433 Set different peer certificate verification options. See the
434 verify(1) manual page for details.
435 -crl_check, -crl_check_all
437 Check the peer certificate has not been revoked by its CA. The
438 CRL(s) are appended to the certificate file. With the
439 -crl_check_all option all CRLs of all CAs in the chain are checked.
440 -nbio
442 Turns on non blocking I/O.
443 -psk_identity val
445 Expect the client to send PSK identity val when using a PSK cipher
446 suite, and warn if they do not. By default, the expected PSK
447 identity is the string "Client_identity".
448 -psk_hint val
450 Use the PSK identity hint val when using a PSK cipher suite.
451 -psk val
453 Use the PSK key val when using a PSK cipher suite. The key is given
454 as a hexadecimal number without leading 0x, for example -psk
455 1a2b3c4d. This option must be provided in order to use a PSK
456 cipher.
457 -psk_session file
459 Use the pem encoded SSL_SESSION data stored in file as the basis of
460 a PSK. Note that this will only work if TLSv1.3 is negotiated.
461 -listen
463 This option can only be used in conjunction with one of the DTLS
464 options above. With this option s_server will listen on a UDP port
465 for incoming connections. Any ClientHellos that arrive will be
466 checked to see if they have a cookie in them or not. Any without a
467 cookie will be responded to with a HelloVerifyRequest. If a
468 ClientHello with a cookie is received then s_server will connect to
469 that peer and complete the handshake.
470 -dtls, -dtls1, -dtls1_2
472 These options make s_server use DTLS protocols instead of TLS.
473 With -dtls, s_server will negotiate any supported DTLS protocol
474 version, whilst -dtls1 and -dtls1_2 will only support DTLSv1.0 and
475 DTLSv1.2 respectively.
476 -sctp
478 Use SCTP for the transport protocol instead of UDP in DTLS. Must be
479 used in conjunction with -dtls, -dtls1 or -dtls1_2. This option is
480 only available where OpenSSL has support for SCTP enabled.
481 -sctp_label_bug
483 Use the incorrect behaviour of older OpenSSL implementations when
484 computing endpoint-pair shared secrets for DTLS/SCTP. This allows
485 communication with older broken implementations but breaks
486 interoperability with correct implementations. Must be used in
487 conjunction with -sctp. This option is only available where OpenSSL
488 has support for SCTP enabled.
489 -no_dhe
491 If this option is set then no DH parameters will be loaded
492 effectively disabling the ephemeral DH cipher suites.
493 -alpn val, -nextprotoneg val
495 These flags enable the Application-Layer Protocol Negotiation or
496 Next Protocol Negotiation (NPN) extension, respectively. ALPN is
497 the IETF standard and replaces NPN. The val list is a comma-
498 separated list of supported protocol names. The list should
499 contain the most desirable protocols first. Protocol names are
500 printable ASCII strings, for example "http/1.1" or "spdy/3". The
501 flag -nextprotoneg cannot be specified if -tls1_3 is used.
502 -engine val
504 Specifying an engine (by its unique id string in val) will cause
505 s_server to attempt to obtain a functional reference to the
506 specified engine, thus initialising it if needed. The engine will
507 then be set as the default for all available algorithms.
508 -keylogfile outfile
510 Appends TLS secrets to the specified keylog file such that external
511 programs (like Wireshark) can decrypt TLS connections.
512 -max_early_data int
514 Change the default maximum early data bytes that are specified for
515 new sessions and any incoming early data (when used in conjunction
516 with the -early_data flag). The default value is approximately 16k.
517 The argument must be an integer greater than or equal to 0.
518 -early_data
520 Accept early data where possible. Cannot be used in conjunction
521 with -www, -WWW, -HTTP or -rev.
522 -anti_replay, -no_anti_replay
524 Switches replay protection on or off, respectively. Replay
525 protection is on by default unless overridden by a configuration
526 file. When it is on, OpenSSL will automatically detect if a session
527 ticket has been used more than once, TLSv1.3 has been negotiated,
528 and early data is enabled on the server. A full handshake is forced
529 if a session ticket is used a second or subsequent time. Any early
530 data that was sent will be rejected.
531
533 If a connection request is established with an SSL client and neither
534 the -www nor the -WWW option has been used then normally any data
535 received from the client is displayed and any key presses will be sent
536 to the client.
537 Certain commands are also recognized which perform special operations.
539 These commands are a letter which must appear at the start of a line.
540 They are listed below.
541 q End the current SSL connection but still accept new connections.
543 Q End the current SSL connection and exit.
545 r Renegotiate the SSL session (TLSv1.2 and below only).
547 R Renegotiate the SSL session and request a client certificate
549 (TLSv1.2 and below only).
550 P Send some plain text down the underlying TCP connection: this
552 should cause the client to disconnect due to a protocol violation.
553 S Print out some session cache status information.
555 B Send a heartbeat message to the client (DTLS only)
557 k Send a key update message to the client (TLSv1.3 only)
559 K Send a key update message to the client and request one back
561 (TLSv1.3 only)
562 c Send a certificate request to the client (TLSv1.3 only)
564
566 s_server can be used to debug SSL clients. To accept connections from a
567 web browser the command:
568 openssl s_server -accept 443 -www
570 can be used for example.
572 Although specifying an empty list of CAs when requesting a client
574 certificate is strictly speaking a protocol violation, some SSL clients
575 interpret this to mean any CA is acceptable. This is useful for
576 debugging purposes.
577 The session parameters can printed out using the sess_id program.
579
581 Because this program has a lot of options and also because some of the
582 techniques used are rather old, the C source of s_server is rather hard
583 to read and not a model of how things should be done. A typical SSL
584 server program would be much simpler.
585 The output of common ciphers is wrong: it just gives the list of
587 ciphers that OpenSSL recognizes and the client supports.
588 There should be a way for the s_server program to print out details of
590 any unknown cipher suites a client says it supports.
591
593 SSL_CONF_cmd(3), sess_id(1), s_client(1), ciphers(1)
594 SSL_CTX_set_max_send_fragment(3), SSL_CTX_set_split_send_fragment(3),
595 SSL_CTX_set_max_pipelines(3)
596
598 The -no_alt_chains option was added in OpenSSL 1.1.0.
599 The -allow-no-dhe-kex and -prioritize_chacha options were added in
601 OpenSSL 1.1.1.
602
604 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
605 Licensed under the OpenSSL license (the "License"). You may not use
607 this file except in compliance with the License. You can obtain a copy
608 in the file LICENSE in the source distribution or at
609 <https://www.openssl.org/source/license.html>.
6101.1.1l 2021-09-15 S_SERVER(1)