6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
20 [B<-certform DER|PEM>]
25 [B<-dcertform DER|PEM>]
27 [B<-dkeyform DER|PEM>]
29 [B<-dhparam filename>]
36 [B<-CApath directory>]
40 [B<-attime timestamp>]
58 [B<-verify_depth num>]
59 [B<-verify_return_error>]
60 [B<-verify_email email>]
61 [B<-verify_hostname hostname>]
63 [B<-verify_name name>]
66 [B<-cipher cipherlist>]
97 [B<-no_resumption_on_reneg>]
100 [B<-status_timeout nsec>]
102 [B<-nextprotoneg protocols>]
106 The B<s_server> command implements a generic SSL/TLS server which listens
107 for connections on a given port using SSL/TLS.
111 In addition to the options below the B<s_server> utility also supports the
112 common and server only options documented in the
113 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
120 Print out a usage message.
122 =item B<-accept port>
124 The TCP port to listen on for connections. If not specified 4433 is used.
126 =item B<-naccept count>
128 The server will exit after receiving B<number> connections, default unlimited.
132 Sets the SSL context id. It can be given any string value. If this option
133 is not present a default value will be used.
135 =item B<-cert certname>
137 The certificate to use, most servers cipher suites require the use of a
138 certificate and some require a certificate with a certain public key type:
139 for example the DSS cipher suites require a certificate containing a DSS
140 (DSA) key. If not specified then the filename "server.pem" will be used.
142 =item B<-certform format>
144 The certificate format to use: DER or PEM. PEM is the default.
146 =item B<-key keyfile>
148 The private key to use. If not specified then the certificate file will
151 =item B<-keyform format>
153 The private format to use: DER or PEM. PEM is the default.
157 The private key password source. For more information about the format of B<arg>
158 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
160 =item B<-dcert filename>, B<-dkey keyname>
162 Specify an additional certificate and private key, these behave in the
163 same manner as the B<-cert> and B<-key> options except there is no default
164 if they are not specified (no additional certificate and key is used). As
165 noted above some cipher suites require a certificate containing a key of
166 a certain type. Some cipher suites need a certificate carrying an RSA key
167 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
168 a server can support clients which only support RSA or DSS cipher suites
169 by using an appropriate certificate.
171 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
173 Additional certificate and private key format and passphrase respectively.
177 If this option is set then no certificate is used. This restricts the
178 cipher suites available to the anonymous ones (currently just anonymous
181 =item B<-dhparam filename>
183 The DH parameter file to use. The ephemeral DH cipher suites generate keys
184 using a set of DH parameters. If not specified then an attempt is made to
185 load the parameters from the server certificate file.
186 If this fails then a static set of parameters hard coded into the B<s_server>
187 program will be used.
191 If this option is set then no DH parameters will be loaded effectively
192 disabling the ephemeral DH cipher suites.
194 =item B<-crl_check>, B<-crl_check_all>
196 Check the peer certificate has not been revoked by its CA.
197 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
198 option all CRLs of all CAs in the chain are checked.
200 =item B<-CApath directory>
202 The directory to use for client certificate verification. This directory
203 must be in "hash format", see B<verify> for more information. These are
204 also used when building the server certificate chain.
206 =item B<-CAfile file>
208 A file containing trusted certificates to use during client authentication
209 and to use when attempting to build the server certificate chain. The list
210 is also used in the list of acceptable client CAs passed to the client when
211 a certificate is requested.
215 Do not load the trusted CA certificates from the default file location
219 Do not load the trusted CA certificates from the default directory location
221 =item B<-verify depth>, B<-Verify depth>
223 The verify depth to use. This specifies the maximum length of the
224 client certificate chain and makes the server request a certificate from
225 the client. With the B<-verify> option a certificate is requested but the
226 client does not have to send one, with the B<-Verify> option the client
227 must supply a certificate or an error occurs.
229 If the ciphersuite cannot request a client certificate (for example an
230 anonymous ciphersuite or PSK) this option has no effect.
232 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
233 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
234 B<-inhibit_map>, B<-no_alt_chains>, B<-partial_chain>, B<-policy>,
235 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
236 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
237 B<-verify_depth>, B<-verify_email>, B<-verify_hostname>, B<-verify_ip>,
238 B<-verify_name>, B<-x509_strict>
240 Set different peer certificate verification options.
241 See the L<verify(1)> manual page for details.
243 =item B<-verify_return_error>
245 Verification errors normally just print a message but allow the
246 connection to continue, for debugging purposes.
247 If this option is used, then verification errors close the connection.
251 Prints the SSL session states.
255 Print extensive debugging information including a hex dump of all traffic.
259 Show all protocol messages with hex dump.
263 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
264 with B<enable-ssl-trace> for this option to work.
268 File to send output of B<-msg> or B<-trace> to, default standard output.
272 Tests non blocking I/O
276 Turns on non blocking I/O
280 This option translated a line feed from the terminal into CR+LF.
284 Inhibit printing of session and certificate information.
286 =item B<-psk_hint hint>
288 Use the PSK identity hint B<hint> when using a PSK cipher suite.
292 Use the PSK key B<key> when using a PSK cipher suite. The key is
293 given as a hexadecimal number without leading 0x, for example -psk
296 =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>
298 These options require or disable the use of the specified SSL or TLS protocols.
299 By default B<s_server> will negotiate the highest mutually supported protocol
301 When a specific TLS version is required, only that version will be accepted
304 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
306 These options make B<s_server> use DTLS protocols instead of TLS.
307 With B<-dtls>, B<s_server> will negotiate any supported DTLS protcol version,
308 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
313 This option can only be used in conjunction with one of the DTLS options above.
314 With this option B<s_server> will listen on a UDP port for incoming connections.
315 Any ClientHellos that arrive will be checked to see if they have a cookie in
317 Any without a cookie will be responded to with a HelloVerifyRequest.
318 If a ClientHello with a cookie is received then B<s_server> will connect to
319 that peer and complete the handshake.
323 Switch on asynchronous mode. Cryptographic operations will be performed
324 asynchronously. This will only have an effect if an asynchronous capable engine
325 is also used via the B<-engine> option. For test purposes the dummy async engine
326 (dasync) can be used (if available).
328 =item B<-split_send_frag int>
330 The size used to split data for encrypt pipelines. If more data is written in
331 one go than this value then it will be split into multiple pipelines, up to the
332 maximum number of pipelines defined by max_pipelines. This only has an effect if
333 a suitable ciphersuite has been negotiated, an engine that supports pipelining
334 has been loaded, and max_pipelines is greater than 1. See
335 L<SSL_CTX_set_split_send_fragment(3)> for further information.
337 =item B<-max_pipelines int>
339 The maximum number of encrypt/decrypt pipelines to be used. This will only have
340 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
341 engine) and a suiteable ciphersuite has been negotiated. The default value is 1.
342 See L<SSL_CTX_set_max_pipelines(3)> for further information.
344 =item B<-read_buf int>
346 The default read buffer size to be used for connections. This will only have an
347 effect if the buffer size is larger than the size that would otherwise be used
348 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
349 further information).
353 There are several known bug in SSL and TLS implementations. Adding this
354 option enables various workarounds.
358 Enable negotiation of TLS compression.
359 This option was introduced in OpenSSL 1.1.0.
360 TLS compression is not recommended and is off by default as of
365 Disable negotiation of TLS compression.
366 TLS compression is not recommended and is off by default as of
371 Provide a brief summary of connection parameters instead of the normal verbose
374 =item B<-cipher cipherlist>
376 This allows the cipher list used by the server to be modified. When
377 the client sends a list of supported ciphers the first client cipher
378 also included in the server list is used. Because the client specifies
379 the preference order, the order of the server cipherlist irrelevant. See
380 the B<ciphers> command for more information.
384 Use the server's cipher preferences, rather than the client's preferences.
386 =item B<-tlsextdebug>
388 Print a hex dump of any TLS extensions received from the server.
392 Disable RFC4507bis session ticket support.
396 Sends a status message back to the client when it connects. This includes
397 information about the ciphers used and various session parameters.
398 The output is in HTML format so this option will normally be used with a
403 Emulates a simple web server. Pages will be resolved relative to the
404 current directory, for example if the URL https://myhost/page.html is
405 requested the file ./page.html will be loaded.
409 Emulates a simple web server. Pages will be resolved relative to the
410 current directory, for example if the URL https://myhost/page.html is
411 requested the file ./page.html will be loaded. The files loaded are
412 assumed to contain a complete and correct HTTP response (lines that
413 are part of the HTTP response line and headers must end with CRLF).
417 Simple test server which just reverses the text received from the client
418 and sends it back to the server. Also sets B<-brief>.
422 Specifying an engine (by its unique B<id> string) will cause B<s_server>
423 to attempt to obtain a functional reference to the specified engine,
424 thus initialising it if needed. The engine will then be set as the default
425 for all available algorithms.
427 =item B<-id_prefix arg>
429 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
430 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
431 servers, when each of which might be generating a unique range of session
432 IDs (eg. with a certain prefix).
434 =item B<-rand file(s)>
436 A file or files containing random data used to seed the random number
437 generator, or an EGD socket (see L<RAND_egd(3)>).
438 Multiple files can be specified separated by an OS-dependent character.
439 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
442 =item B<-serverinfo file>
444 A file containing one or more blocks of PEM data. Each PEM block
445 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
446 followed by "length" bytes of extension data). If the client sends
447 an empty TLS ClientHello extension matching the type, the corresponding
448 ServerHello extension will be returned.
450 =item B<-no_resumption_on_reneg>
452 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
456 Enables certificate status request support (aka OCSP stapling).
458 =item B<-status_verbose>
460 Enables certificate status request support (aka OCSP stapling) and gives
461 a verbose printout of the OCSP response.
463 =item B<-status_timeout nsec>
465 Sets the timeout for OCSP response to B<nsec> seconds.
467 =item B<-status_url url>
469 Sets a fallback responder URL to use if no responder URL is present in the
470 server certificate. Without this option an error is returned if the server
471 certificate does not contain a responder address.
473 =item B<-nextprotoneg protocols>
475 Enable Next Protocol Negotiation TLS extension and provide a
476 comma-separated list of supported protocol names.
477 The list should contain most wanted protocols first.
478 Protocol names are printable ASCII strings, for example "http/1.1" or
483 =head1 CONNECTED COMMANDS
485 If a connection request is established with an SSL client and neither the
486 B<-www> nor the B<-WWW> option has been used then normally any data received
487 from the client is displayed and any key presses will be sent to the client.
489 Certain single letter commands are also recognized which perform special
490 operations: these are listed below.
496 end the current SSL connection but still accept new connections.
500 end the current SSL connection and exit.
504 renegotiate the SSL session.
508 renegotiate the SSL session and request a client certificate.
512 send some plain text down the underlying TCP connection: this should
513 cause the client to disconnect due to a protocol violation.
517 print out some session cache status information.
523 B<s_server> can be used to debug SSL clients. To accept connections from
524 a web browser the command:
526 openssl s_server -accept 443 -www
528 can be used for example.
530 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
531 suites, so they cannot connect to servers which don't use a certificate
532 carrying an RSA key or a version of OpenSSL with RSA disabled.
534 Although specifying an empty list of CAs when requesting a client certificate
535 is strictly speaking a protocol violation, some SSL clients interpret this to
536 mean any CA is acceptable. This is useful for debugging purposes.
538 The session parameters can printed out using the B<sess_id> program.
542 Because this program has a lot of options and also because some of the
543 techniques used are rather old, the C source of B<s_server> is rather hard to
544 read and not a model of how things should be done.
545 A typical SSL server program would be much simpler.
547 The output of common ciphers is wrong: it just gives the list of ciphers that
548 OpenSSL recognizes and the client supports.
550 There should be a way for the B<s_server> program to print out details of any
551 unknown cipher suites a client says it supports.
555 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
559 The -no_alt_chains options was first added to OpenSSL 1.1.0.