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>]
91 [B<-no_resumption_on_reneg>]
94 [B<-status_timeout nsec>]
96 [B<-nextprotoneg protocols>]
100 The B<s_server> command implements a generic SSL/TLS server which listens
101 for connections on a given port using SSL/TLS.
105 In addition to the options below the B<s_server> utility also supports the
106 common and server only options documented in the
107 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
112 =item B<-accept port>
114 the TCP port to listen on for connections. If not specified 4433 is used.
116 =item B<-naccept count>
118 The server will exit after receiving B<number> connections, default unlimited.
122 sets the SSL context id. It can be given any string value. If this option
123 is not present a default value will be used.
125 =item B<-cert certname>
127 The certificate to use, most servers cipher suites require the use of a
128 certificate and some require a certificate with a certain public key type:
129 for example the DSS cipher suites require a certificate containing a DSS
130 (DSA) key. If not specified then the filename "server.pem" will be used.
132 =item B<-certform format>
134 The certificate format to use: DER or PEM. PEM is the default.
136 =item B<-key keyfile>
138 The private key to use. If not specified then the certificate file will
141 =item B<-keyform format>
143 The private format to use: DER or PEM. PEM is the default.
147 the private key password source. For more information about the format of B<arg>
148 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
150 =item B<-dcert filename>, B<-dkey keyname>
152 specify an additional certificate and private key, these behave in the
153 same manner as the B<-cert> and B<-key> options except there is no default
154 if they are not specified (no additional certificate and key is used). As
155 noted above some cipher suites require a certificate containing a key of
156 a certain type. Some cipher suites need a certificate carrying an RSA key
157 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
158 a server can support clients which only support RSA or DSS cipher suites
159 by using an appropriate certificate.
161 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
163 additional certificate and private key format and passphrase respectively.
167 if this option is set then no certificate is used. This restricts the
168 cipher suites available to the anonymous ones (currently just anonymous
171 =item B<-dhparam filename>
173 the DH parameter file to use. The ephemeral DH cipher suites generate keys
174 using a set of DH parameters. If not specified then an attempt is made to
175 load the parameters from the server certificate file. If this fails then
176 a static set of parameters hard coded into the s_server program will be used.
180 if this option is set then no DH parameters will be loaded effectively
181 disabling the ephemeral DH cipher suites.
185 if this option is set then no ECDH parameters will be loaded effectively
186 disabling the ephemeral ECDH cipher suites.
188 =item B<-crl_check>, B<-crl_check_all>
190 Check the peer certificate has not been revoked by its CA.
191 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
192 option all CRLs of all CAs in the chain are checked.
194 =item B<-CApath directory>
196 The directory to use for client certificate verification. This directory
197 must be in "hash format", see B<verify> for more information. These are
198 also used when building the server certificate chain.
200 =item B<-CAfile file>
202 A file containing trusted certificates to use during client authentication
203 and to use when attempting to build the server certificate chain. The list
204 is also used in the list of acceptable client CAs passed to the client when
205 a certificate is requested.
209 Do not load the trusted CA certificates from the default file location
213 Do not load the trusted CA certificates from the default directory location
215 =item B<-verify depth>, B<-Verify depth>
217 The verify depth to use. This specifies the maximum length of the
218 client certificate chain and makes the server request a certificate from
219 the client. With the B<-verify> option a certificate is requested but the
220 client does not have to send one, with the B<-Verify> option the client
221 must supply a certificate or an error occurs.
223 If the ciphersuite cannot request a client certificate (for example an
224 anonymous ciphersuite or PSK) this option has no effect.
226 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
227 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
228 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
229 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
230 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
231 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
233 Set different peer certificate verification options.
234 See the L<verify(1)> manual page for details.
236 =item B<-verify_return_error>
238 Verification errors normally just print a message but allow the
239 connection to continue, for debugging purposes.
240 If this option is used, then verification errors close the connection.
244 prints out the SSL session states.
248 print extensive debugging information including a hex dump of all traffic.
252 show all protocol messages with hex dump.
256 show verbose trace output of protocol messages. OpenSSL needs to be compiled
257 with B<enable-ssl-trace> for this option to work.
261 file to send output of B<-msg> or B<-trace> to, default standard output.
265 tests non blocking I/O
269 turns on non blocking I/O
273 this option translated a line feed from the terminal into CR+LF.
277 inhibit printing of session and certificate information.
279 =item B<-psk_hint hint>
281 Use the PSK identity hint B<hint> when using a PSK cipher suite.
285 Use the PSK key B<key> when using a PSK cipher suite. The key is
286 given as a hexadecimal number without leading 0x, for example -psk
289 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
291 these options disable the use of certain SSL or TLS protocols. By default
292 the initial handshake uses a method which should be compatible with all
293 servers and permit them to use SSL v3 or TLS as appropriate.
295 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
297 these options make s_server use DTLS protocols instead of TLS. With B<-dtls>
298 s_server will negotiate any supported DTLS protcol version, whilst B<-dtls1> and
299 B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 respectively.
303 this option can only be used in conjunction with one of the DTLS options above.
304 With this option s_server will listen on a UDP port for incoming connections.
305 Any ClientHellos that arrive will be checked to see if they have a cookie in
306 them or not. Any without a cookie will be responded to with a
307 HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
308 will connect to that peer and complete the handshake.
312 switch on asynchronous mode. Cryptographic operations will be performed
313 asynchronously. This will only have an effect if an asynchronous capable engine
314 is also used via the B<-engine> option. For test purposes the dummy async engine
315 (dasync) can be used (if available).
319 there are several known bug in SSL and TLS implementations. Adding this
320 option enables various workarounds.
324 only provide a brief summary of connection parameters instead of the
325 normal verbose output.
327 =item B<-cipher cipherlist>
329 this allows the cipher list used by the server to be modified. When
330 the client sends a list of supported ciphers the first client cipher
331 also included in the server list is used. Because the client specifies
332 the preference order, the order of the server cipherlist irrelevant. See
333 the B<ciphers> command for more information.
337 use the server's cipher preferences, rather than the client's preferences.
339 =item B<-tlsextdebug>
341 print out a hex dump of any TLS extensions received from the server.
345 disable RFC4507bis session ticket support.
349 sends a status message back to the client when it connects. This includes
350 lots of information about the ciphers used and various session parameters.
351 The output is in HTML format so this option will normally be used with a
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.
362 emulates a simple web server. Pages will be resolved relative to the
363 current directory, for example if the URL https://myhost/page.html is
364 requested the file ./page.html will be loaded. The files loaded are
365 assumed to contain a complete and correct HTTP response (lines that
366 are part of the HTTP response line and headers must end with CRLF).
370 simple test server which just reverses the text received from the client
371 and sends it back to the server. Also sets B<-brief>.
375 specifying an engine (by its unique B<id> string) will cause B<s_server>
376 to attempt to obtain a functional reference to the specified engine,
377 thus initialising it if needed. The engine will then be set as the default
378 for all available algorithms.
380 =item B<-id_prefix arg>
382 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
383 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
384 servers, when each of which might be generating a unique range of session
385 IDs (eg. with a certain prefix).
387 =item B<-rand file(s)>
389 a file or files containing random data used to seed the random number
390 generator, or an EGD socket (see L<RAND_egd(3)>).
391 Multiple files can be specified separated by a OS-dependent character.
392 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
395 =item B<-serverinfo file>
397 a file containing one or more blocks of PEM data. Each PEM block
398 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
399 followed by "length" bytes of extension data). If the client sends
400 an empty TLS ClientHello extension matching the type, the corresponding
401 ServerHello extension will be returned.
403 =item B<-no_resumption_on_reneg>
405 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
409 enables certificate status request support (aka OCSP stapling).
411 =item B<-status_verbose>
413 enables certificate status request support (aka OCSP stapling) and gives
414 a verbose printout of the OCSP response.
416 =item B<-status_timeout nsec>
418 sets the timeout for OCSP response to B<nsec> seconds.
420 =item B<-status_url url>
422 sets a fallback responder URL to use if no responder URL is present in the
423 server certificate. Without this option an error is returned if the server
424 certificate does not contain a responder address.
426 =item B<-nextprotoneg protocols>
428 enable Next Protocol Negotiation TLS extension and provide a
429 comma-separated list of supported protocol names.
430 The list should contain most wanted protocols first.
431 Protocol names are printable ASCII strings, for example "http/1.1" or
436 =head1 CONNECTED COMMANDS
438 If a connection request is established with an SSL client and neither the
439 B<-www> nor the B<-WWW> option has been used then normally any data received
440 from the client is displayed and any key presses will be sent to the client.
442 Certain single letter commands are also recognized which perform special
443 operations: these are listed below.
449 end the current SSL connection but still accept new connections.
453 end the current SSL connection and exit.
457 renegotiate the SSL session.
461 renegotiate the SSL session and request a client certificate.
465 send some plain text down the underlying TCP connection: this should
466 cause the client to disconnect due to a protocol violation.
470 print out some session cache status information.
476 B<s_server> can be used to debug SSL clients. To accept connections from
477 a web browser the command:
479 openssl s_server -accept 443 -www
481 can be used for example.
483 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
484 suites, so they cannot connect to servers which don't use a certificate
485 carrying an RSA key or a version of OpenSSL with RSA disabled.
487 Although specifying an empty list of CAs when requesting a client certificate
488 is strictly speaking a protocol violation, some SSL clients interpret this to
489 mean any CA is acceptable. This is useful for debugging purposes.
491 The session parameters can printed out using the B<sess_id> program.
495 Because this program has a lot of options and also because some of
496 the techniques used are rather old, the C source of s_server is rather
497 hard to read and not a model of how things should be done. A typical
498 SSL server program would be much simpler.
500 The output of common ciphers is wrong: it just gives the list of ciphers that
501 OpenSSL recognizes and the client supports.
503 There should be a way for the B<s_server> program to print out details of any
504 unknown cipher suites a client says it supports.
508 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
512 The -no_alt_chains options was first added to OpenSSL 1.1.0.