6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
19 [B<-certform DER|PEM>]
24 [B<-dcertform DER|PEM>]
26 [B<-dkeyform DER|PEM>]
28 [B<-dhparam filename>]
35 [B<-CApath directory>]
39 [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>]
90 [B<-no_resumption_on_reneg>]
93 [B<-status_timeout nsec>]
95 [B<-nextprotoneg protocols>]
99 The B<s_server> command implements a generic SSL/TLS server which listens
100 for connections on a given port using SSL/TLS.
104 In addition to the options below the B<s_server> utility also supports the
105 common and server only options documented in the
106 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
111 =item B<-accept port>
113 the TCP port to listen on for connections. If not specified 4433 is used.
115 =item B<-naccept count>
117 The server will exit after receiving B<number> connections, default unlimited.
121 sets the SSL context id. It can be given any string value. If this option
122 is not present a default value will be used.
124 =item B<-cert certname>
126 The certificate to use, most servers cipher suites require the use of a
127 certificate and some require a certificate with a certain public key type:
128 for example the DSS cipher suites require a certificate containing a DSS
129 (DSA) key. If not specified then the filename "server.pem" will be used.
131 =item B<-certform format>
133 The certificate format to use: DER or PEM. PEM is the default.
135 =item B<-key keyfile>
137 The private key to use. If not specified then the certificate file will
140 =item B<-keyform format>
142 The private format to use: DER or PEM. PEM is the default.
146 the private key password source. For more information about the format of B<arg>
147 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
149 =item B<-dcert filename>, B<-dkey keyname>
151 specify an additional certificate and private key, these behave in the
152 same manner as the B<-cert> and B<-key> options except there is no default
153 if they are not specified (no additional certificate and key is used). As
154 noted above some cipher suites require a certificate containing a key of
155 a certain type. Some cipher suites need a certificate carrying an RSA key
156 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
157 a server can support clients which only support RSA or DSS cipher suites
158 by using an appropriate certificate.
160 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
162 additional certificate and private key format and passphrase respectively.
166 if this option is set then no certificate is used. This restricts the
167 cipher suites available to the anonymous ones (currently just anonymous
170 =item B<-dhparam filename>
172 the DH parameter file to use. The ephemeral DH cipher suites generate keys
173 using a set of DH parameters. If not specified then an attempt is made to
174 load the parameters from the server certificate file. If this fails then
175 a static set of parameters hard coded into the s_server program will be used.
179 if this option is set then no DH parameters will be loaded effectively
180 disabling the ephemeral DH cipher suites.
182 =item B<-crl_check>, B<-crl_check_all>
184 Check the peer certificate has not been revoked by its CA.
185 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
186 option all CRLs of all CAs in the chain are checked.
188 =item B<-CApath directory>
190 The directory to use for client certificate verification. This directory
191 must be in "hash format", see B<verify> for more information. These are
192 also used when building the server certificate chain.
194 =item B<-CAfile file>
196 A file containing trusted certificates to use during client authentication
197 and to use when attempting to build the server certificate chain. The list
198 is also used in the list of acceptable client CAs passed to the client when
199 a certificate is requested.
203 Do not load the trusted CA certificates from the default file location
207 Do not load the trusted CA certificates from the default directory location
209 =item B<-verify depth>, B<-Verify depth>
211 The verify depth to use. This specifies the maximum length of the
212 client certificate chain and makes the server request a certificate from
213 the client. With the B<-verify> option a certificate is requested but the
214 client does not have to send one, with the B<-Verify> option the client
215 must supply a certificate or an error occurs.
217 If the ciphersuite cannot request a client certificate (for example an
218 anonymous ciphersuite or PSK) this option has no effect.
220 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
221 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
222 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
223 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
224 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
225 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
227 Set different peer certificate verification options.
228 See the L<verify(1)> manual page for details.
230 =item B<-verify_return_error>
232 Verification errors normally just print a message but allow the
233 connection to continue, for debugging purposes.
234 If this option is used, then verification errors close the connection.
238 prints out the SSL session states.
242 print extensive debugging information including a hex dump of all traffic.
246 show all protocol messages with hex dump.
250 show verbose trace output of protocol messages. OpenSSL needs to be compiled
251 with B<enable-ssl-trace> for this option to work.
255 file to send output of B<-msg> or B<-trace> to, default standard output.
259 tests non blocking I/O
263 turns on non blocking I/O
267 this option translated a line feed from the terminal into CR+LF.
271 inhibit printing of session and certificate information.
273 =item B<-psk_hint hint>
275 Use the PSK identity hint B<hint> when using a PSK cipher suite.
279 Use the PSK key B<key> when using a PSK cipher suite. The key is
280 given as a hexadecimal number without leading 0x, for example -psk
283 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
285 these options disable the use of certain SSL or TLS protocols. By default
286 the initial handshake uses a method which should be compatible with all
287 servers and permit them to use SSL v3 or TLS as appropriate.
289 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
291 these options make s_server use DTLS protocols instead of TLS. With B<-dtls>
292 s_server will negotiate any supported DTLS protcol version, whilst B<-dtls1> and
293 B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 respectively.
297 this option can only be used in conjunction with one of the DTLS options above.
298 With this option s_server will listen on a UDP port for incoming connections.
299 Any ClientHellos that arrive will be checked to see if they have a cookie in
300 them or not. Any without a cookie will be responded to with a
301 HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
302 will connect to that peer and complete the handshake.
306 switch on asynchronous mode. Cryptographic operations will be performed
307 asynchronously. This will only have an effect if an asynchronous capable engine
308 is also used via the B<-engine> option. For test purposes the dummy async engine
309 (dasync) can be used (if available).
313 there are several known bug in SSL and TLS implementations. Adding this
314 option enables various workarounds.
318 only provide a brief summary of connection parameters instead of the
319 normal verbose output.
321 =item B<-cipher cipherlist>
323 this allows the cipher list used by the server to be modified. When
324 the client sends a list of supported ciphers the first client cipher
325 also included in the server list is used. Because the client specifies
326 the preference order, the order of the server cipherlist irrelevant. See
327 the B<ciphers> command for more information.
331 use the server's cipher preferences, rather than the client's preferences.
333 =item B<-tlsextdebug>
335 print out a hex dump of any TLS extensions received from the server.
339 disable RFC4507bis session ticket support.
343 sends a status message back to the client when it connects. This includes
344 lots of information about the ciphers used and various session parameters.
345 The output is in HTML format so this option will normally be used with a
350 emulates a simple web server. Pages will be resolved relative to the
351 current directory, for example if the URL https://myhost/page.html is
352 requested the file ./page.html will be loaded.
356 emulates a simple web server. Pages will be resolved relative to the
357 current directory, for example if the URL https://myhost/page.html is
358 requested the file ./page.html will be loaded. The files loaded are
359 assumed to contain a complete and correct HTTP response (lines that
360 are part of the HTTP response line and headers must end with CRLF).
364 simple test server which just reverses the text received from the client
365 and sends it back to the server. Also sets B<-brief>.
369 specifying an engine (by its unique B<id> string) will cause B<s_server>
370 to attempt to obtain a functional reference to the specified engine,
371 thus initialising it if needed. The engine will then be set as the default
372 for all available algorithms.
374 =item B<-id_prefix arg>
376 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
377 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
378 servers, when each of which might be generating a unique range of session
379 IDs (eg. with a certain prefix).
381 =item B<-rand file(s)>
383 a file or files containing random data used to seed the random number
384 generator, or an EGD socket (see L<RAND_egd(3)>).
385 Multiple files can be specified separated by a OS-dependent character.
386 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
389 =item B<-serverinfo file>
391 a file containing one or more blocks of PEM data. Each PEM block
392 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
393 followed by "length" bytes of extension data). If the client sends
394 an empty TLS ClientHello extension matching the type, the corresponding
395 ServerHello extension will be returned.
397 =item B<-no_resumption_on_reneg>
399 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
403 enables certificate status request support (aka OCSP stapling).
405 =item B<-status_verbose>
407 enables certificate status request support (aka OCSP stapling) and gives
408 a verbose printout of the OCSP response.
410 =item B<-status_timeout nsec>
412 sets the timeout for OCSP response to B<nsec> seconds.
414 =item B<-status_url url>
416 sets a fallback responder URL to use if no responder URL is present in the
417 server certificate. Without this option an error is returned if the server
418 certificate does not contain a responder address.
420 =item B<-nextprotoneg protocols>
422 enable Next Protocol Negotiation TLS extension and provide a
423 comma-separated list of supported protocol names.
424 The list should contain most wanted protocols first.
425 Protocol names are printable ASCII strings, for example "http/1.1" or
430 =head1 CONNECTED COMMANDS
432 If a connection request is established with an SSL client and neither the
433 B<-www> nor the B<-WWW> option has been used then normally any data received
434 from the client is displayed and any key presses will be sent to the client.
436 Certain single letter commands are also recognized which perform special
437 operations: these are listed below.
443 end the current SSL connection but still accept new connections.
447 end the current SSL connection and exit.
451 renegotiate the SSL session.
455 renegotiate the SSL session and request a client certificate.
459 send some plain text down the underlying TCP connection: this should
460 cause the client to disconnect due to a protocol violation.
464 print out some session cache status information.
470 B<s_server> can be used to debug SSL clients. To accept connections from
471 a web browser the command:
473 openssl s_server -accept 443 -www
475 can be used for example.
477 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
478 suites, so they cannot connect to servers which don't use a certificate
479 carrying an RSA key or a version of OpenSSL with RSA disabled.
481 Although specifying an empty list of CAs when requesting a client certificate
482 is strictly speaking a protocol violation, some SSL clients interpret this to
483 mean any CA is acceptable. This is useful for debugging purposes.
485 The session parameters can printed out using the B<sess_id> program.
489 Because this program has a lot of options and also because some of
490 the techniques used are rather old, the C source of s_server is rather
491 hard to read and not a model of how things should be done. A typical
492 SSL server program would be much simpler.
494 The output of common ciphers is wrong: it just gives the list of ciphers that
495 OpenSSL recognizes and the client supports.
497 There should be a way for the B<s_server> program to print out details of any
498 unknown cipher suites a client says it supports.
502 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
506 The -no_alt_chains options was first added to OpenSSL 1.1.0.