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>]
37 [B<-attime timestamp>]
56 [B<-verify_depth num>]
57 [B<-verify_return_error>]
58 [B<-verify_email email>]
59 [B<-verify_hostname hostname>]
61 [B<-verify_name name>]
64 [B<-cipher cipherlist>]
89 [B<-no_resumption_on_reneg>]
92 [B<-status_timeout nsec>]
94 [B<-nextprotoneg protocols>]
98 The B<s_server> command implements a generic SSL/TLS server which listens
99 for connections on a given port using SSL/TLS.
103 In addition to the options below the B<s_server> utility also supports the
104 common and server only options documented in the
105 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
110 =item B<-accept port>
112 the TCP port to listen on for connections. If not specified 4433 is used.
114 =item B<-naccept count>
116 The server will exit after receiving B<number> connections, default unlimited.
120 sets the SSL context id. It can be given any string value. If this option
121 is not present a default value will be used.
123 =item B<-cert certname>
125 The certificate to use, most servers cipher suites require the use of a
126 certificate and some require a certificate with a certain public key type:
127 for example the DSS cipher suites require a certificate containing a DSS
128 (DSA) key. If not specified then the filename "server.pem" will be used.
130 =item B<-certform format>
132 The certificate format to use: DER or PEM. PEM is the default.
134 =item B<-key keyfile>
136 The private key to use. If not specified then the certificate file will
139 =item B<-keyform format>
141 The private format to use: DER or PEM. PEM is the default.
145 the private key password source. For more information about the format of B<arg>
146 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
148 =item B<-dcert filename>, B<-dkey keyname>
150 specify an additional certificate and private key, these behave in the
151 same manner as the B<-cert> and B<-key> options except there is no default
152 if they are not specified (no additional certificate and key is used). As
153 noted above some cipher suites require a certificate containing a key of
154 a certain type. Some cipher suites need a certificate carrying an RSA key
155 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
156 a server can support clients which only support RSA or DSS cipher suites
157 by using an appropriate certificate.
159 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
161 additional certificate and private key format and passphrase respectively.
165 if this option is set then no certificate is used. This restricts the
166 cipher suites available to the anonymous ones (currently just anonymous
169 =item B<-dhparam filename>
171 the DH parameter file to use. The ephemeral DH cipher suites generate keys
172 using a set of DH parameters. If not specified then an attempt is made to
173 load the parameters from the server certificate file. If this fails then
174 a static set of parameters hard coded into the s_server program will be used.
178 if this option is set then no DH parameters will be loaded effectively
179 disabling the ephemeral DH cipher suites.
183 if this option is set then no ECDH parameters will be loaded effectively
184 disabling the ephemeral ECDH cipher suites.
188 certain export cipher suites sometimes use a temporary RSA key, this option
189 disables temporary RSA key generation.
191 =item B<-crl_check>, B<-crl_check_all>
193 Check the peer certificate has not been revoked by its CA.
194 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
195 option all CRLs of all CAs in the chain are checked.
197 =item B<-CApath directory>
199 The directory to use for client certificate verification. This directory
200 must be in "hash format", see B<verify> for more information. These are
201 also used when building the server certificate chain.
203 =item B<-CAfile file>
205 A file containing trusted certificates to use during client authentication
206 and to use when attempting to build the server certificate chain. The list
207 is also used in the list of acceptable client CAs passed to the client when
208 a certificate is requested.
210 =item B<-verify depth>, B<-Verify depth>
212 The verify depth to use. This specifies the maximum length of the
213 client certificate chain and makes the server request a certificate from
214 the client. With the B<-verify> option a certificate is requested but the
215 client does not have to send one, with the B<-Verify> option the client
216 must supply a certificate or an error occurs.
218 If the ciphersuite cannot request a client certificate (for example an
219 anonymous ciphersuite or PSK) this option has no effect.
221 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
222 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
223 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
224 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
225 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
226 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
228 Set different peer certificate verification options.
229 See the L<verify(1)> manual page for details.
231 =item B<-verify_return_error>
233 Verification errors normally just print a message but allow the
234 connection to continue, for debugging purposes.
235 If this option is used, then verification errors close the connection.
239 prints out the SSL session states.
243 print extensive debugging information including a hex dump of all traffic.
247 show all protocol messages with hex dump.
251 show verbose trace output of protocol messages. OpenSSL needs to be compiled
252 with B<enable-ssl-trace> for this option to work.
256 file to send output of B<-msg> or B<-trace> to, default standard output.
260 tests non blocking I/O
264 turns on non blocking I/O
268 this option translated a line feed from the terminal into CR+LF.
272 inhibit printing of session and certificate information.
274 =item B<-psk_hint hint>
276 Use the PSK identity hint B<hint> when using a PSK cipher suite.
280 Use the PSK key B<key> when using a PSK cipher suite. The key is
281 given as a hexadecimal number without leading 0x, for example -psk
284 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
286 these options disable the use of certain SSL or TLS protocols. By default
287 the initial handshake uses a method which should be compatible with all
288 servers and permit them to use SSL v3 or TLS as appropriate.
290 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
292 these options make s_server use DTLS protocols instead of TLS. With B<-dtls>
293 s_server will negotiate any supported DTLS protcol version, whilst B<-dtls1> and
294 B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 respectively.
298 this option can only be used in conjunction with one of the DTLS options above.
299 With this option s_server will listen on a UDP port for incoming connections.
300 Any ClientHellos that arrive will be checked to see if they have a cookie in
301 them or not. Any without a cookie will be responded to with a
302 HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
303 will connect to that peer and complete the handshake.
307 there are several known bug in SSL and TLS implementations. Adding this
308 option enables various workarounds.
312 only provide a brief summary of connection parameters instead of the
313 normal verbose output.
315 =item B<-cipher cipherlist>
317 this allows the cipher list used by the server to be modified. When
318 the client sends a list of supported ciphers the first client cipher
319 also included in the server list is used. Because the client specifies
320 the preference order, the order of the server cipherlist irrelevant. See
321 the B<ciphers> command for more information.
325 use the server's cipher preferences, rather than the client's preferences.
327 =item B<-tlsextdebug>
329 print out a hex dump of any TLS extensions received from the server.
333 disable RFC4507bis session ticket support.
337 sends a status message back to the client when it connects. This includes
338 lots of information about the ciphers used and various session parameters.
339 The output is in HTML format so this option will normally be used with a
344 emulates a simple web server. Pages will be resolved relative to the
345 current directory, for example if the URL https://myhost/page.html is
346 requested the file ./page.html will be loaded.
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. The files loaded are
353 assumed to contain a complete and correct HTTP response (lines that
354 are part of the HTTP response line and headers must end with CRLF).
358 simple test server which just reverses the text received from the client
359 and sends it back to the server. Also sets B<-brief>.
363 specifying an engine (by its unique B<id> string) will cause B<s_server>
364 to attempt to obtain a functional reference to the specified engine,
365 thus initialising it if needed. The engine will then be set as the default
366 for all available algorithms.
368 =item B<-id_prefix arg>
370 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
371 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
372 servers, when each of which might be generating a unique range of session
373 IDs (eg. with a certain prefix).
375 =item B<-rand file(s)>
377 a file or files containing random data used to seed the random number
378 generator, or an EGD socket (see L<RAND_egd(3)>).
379 Multiple files can be specified separated by a OS-dependent character.
380 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
383 =item B<-serverinfo file>
385 a file containing one or more blocks of PEM data. Each PEM block
386 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
387 followed by "length" bytes of extension data). If the client sends
388 an empty TLS ClientHello extension matching the type, the corresponding
389 ServerHello extension will be returned.
391 =item B<-no_resumption_on_reneg>
393 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
397 enables certificate status request support (aka OCSP stapling).
399 =item B<-status_verbose>
401 enables certificate status request support (aka OCSP stapling) and gives
402 a verbose printout of the OCSP response.
404 =item B<-status_timeout nsec>
406 sets the timeout for OCSP response to B<nsec> seconds.
408 =item B<-status_url url>
410 sets a fallback responder URL to use if no responder URL is present in the
411 server certificate. Without this option an error is returned if the server
412 certificate does not contain a responder address.
414 =item B<-nextprotoneg protocols>
416 enable Next Protocol Negotiation TLS extension and provide a
417 comma-separated list of supported protocol names.
418 The list should contain most wanted protocols first.
419 Protocol names are printable ASCII strings, for example "http/1.1" or
424 =head1 CONNECTED COMMANDS
426 If a connection request is established with an SSL client and neither the
427 B<-www> nor the B<-WWW> option has been used then normally any data received
428 from the client is displayed and any key presses will be sent to the client.
430 Certain single letter commands are also recognized which perform special
431 operations: these are listed below.
437 end the current SSL connection but still accept new connections.
441 end the current SSL connection and exit.
445 renegotiate the SSL session.
449 renegotiate the SSL session and request a client certificate.
453 send some plain text down the underlying TCP connection: this should
454 cause the client to disconnect due to a protocol violation.
458 print out some session cache status information.
464 B<s_server> can be used to debug SSL clients. To accept connections from
465 a web browser the command:
467 openssl s_server -accept 443 -www
469 can be used for example.
471 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
472 suites, so they cannot connect to servers which don't use a certificate
473 carrying an RSA key or a version of OpenSSL with RSA disabled.
475 Although specifying an empty list of CAs when requesting a client certificate
476 is strictly speaking a protocol violation, some SSL clients interpret this to
477 mean any CA is acceptable. This is useful for debugging purposes.
479 The session parameters can printed out using the B<sess_id> program.
483 Because this program has a lot of options and also because some of
484 the techniques used are rather old, the C source of s_server is rather
485 hard to read and not a model of how things should be done. A typical
486 SSL server program would be much simpler.
488 The output of common ciphers is wrong: it just gives the list of ciphers that
489 OpenSSL recognizes and the client supports.
491 There should be a way for the B<s_server> program to print out details of any
492 unknown cipher suites a client says it supports.
496 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
500 The -no_alt_chains options was first added to OpenSSL 1.1.0.