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>]
94 [B<-no_resumption_on_reneg>]
97 [B<-status_timeout nsec>]
99 [B<-nextprotoneg protocols>]
103 The B<s_server> command implements a generic SSL/TLS server which listens
104 for connections on a given port using SSL/TLS.
108 In addition to the options below the B<s_server> utility also supports the
109 common and server only options documented in the
110 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
117 Print out a usage message.
119 =item B<-accept port>
121 The TCP port to listen on for connections. If not specified 4433 is used.
123 =item B<-naccept count>
125 The server will exit after receiving B<number> connections, default unlimited.
129 Sets the SSL context id. It can be given any string value. If this option
130 is not present a default value will be used.
132 =item B<-cert certname>
134 The certificate to use, most servers cipher suites require the use of a
135 certificate and some require a certificate with a certain public key type:
136 for example the DSS cipher suites require a certificate containing a DSS
137 (DSA) key. If not specified then the filename "server.pem" will be used.
139 =item B<-certform format>
141 The certificate format to use: DER or PEM. PEM is the default.
143 =item B<-key keyfile>
145 The private key to use. If not specified then the certificate file will
148 =item B<-keyform format>
150 The private format to use: DER or PEM. PEM is the default.
154 The private key password source. For more information about the format of B<arg>
155 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
157 =item B<-dcert filename>, B<-dkey keyname>
159 Specify an additional certificate and private key, these behave in the
160 same manner as the B<-cert> and B<-key> options except there is no default
161 if they are not specified (no additional certificate and key is used). As
162 noted above some cipher suites require a certificate containing a key of
163 a certain type. Some cipher suites need a certificate carrying an RSA key
164 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
165 a server can support clients which only support RSA or DSS cipher suites
166 by using an appropriate certificate.
168 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
170 Additional certificate and private key format and passphrase respectively.
174 If this option is set then no certificate is used. This restricts the
175 cipher suites available to the anonymous ones (currently just anonymous
178 =item B<-dhparam filename>
180 The DH parameter file to use. The ephemeral DH cipher suites generate keys
181 using a set of DH parameters. If not specified then an attempt is made to
182 load the parameters from the server certificate file.
183 If this fails then a static set of parameters hard coded into the B<s_server>
184 program will be used.
188 If this option is set then no DH parameters will be loaded effectively
189 disabling the ephemeral DH cipher suites.
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.
212 Do not load the trusted CA certificates from the default file location
216 Do not load the trusted CA certificates from the default directory location
218 =item B<-verify depth>, B<-Verify depth>
220 The verify depth to use. This specifies the maximum length of the
221 client certificate chain and makes the server request a certificate from
222 the client. With the B<-verify> option a certificate is requested but the
223 client does not have to send one, with the B<-Verify> option the client
224 must supply a certificate or an error occurs.
226 If the ciphersuite cannot request a client certificate (for example an
227 anonymous ciphersuite or PSK) this option has no effect.
229 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
230 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
231 B<-inhibit_map>, B<-no_alt_chains>, B<-partial_chain>, B<-policy>,
232 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
233 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
234 B<-verify_depth>, B<-verify_email>, B<-verify_hostname>, B<-verify_ip>,
235 B<-verify_name>, B<-x509_strict>
237 Set different peer certificate verification options.
238 See the L<verify(1)> manual page for details.
240 =item B<-verify_return_error>
242 Verification errors normally just print a message but allow the
243 connection to continue, for debugging purposes.
244 If this option is used, then verification errors close the connection.
248 Prints the SSL session states.
252 Print extensive debugging information including a hex dump of all traffic.
256 Show all protocol messages with hex dump.
260 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
261 with B<enable-ssl-trace> for this option to work.
265 File to send output of B<-msg> or B<-trace> to, default standard output.
269 Tests non blocking I/O
273 Turns on non blocking I/O
277 This option translated a line feed from the terminal into CR+LF.
281 Inhibit printing of session and certificate information.
283 =item B<-psk_hint hint>
285 Use the PSK identity hint B<hint> when using a PSK cipher suite.
289 Use the PSK key B<key> when using a PSK cipher suite. The key is
290 given as a hexadecimal number without leading 0x, for example -psk
293 =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>
295 These options require or disable the use of the specified SSL or TLS protocols.
296 By default B<s_server> will negotiate the highest mutually supported protocol
298 When a specific TLS version is required, only that version will be accepted
301 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
303 These options make B<s_server> use DTLS protocols instead of TLS.
304 With B<-dtls>, B<s_server> will negotiate any supported DTLS protcol version,
305 whilst B<-dtls1> and B<-dtls1_2> will only support DTLSv1.0 and DTLSv1.2
310 This option can only be used in conjunction with one of the DTLS options above.
311 With this option B<s_server> will listen on a UDP port for incoming connections.
312 Any ClientHellos that arrive will be checked to see if they have a cookie in
314 Any without a cookie will be responded to with a HelloVerifyRequest.
315 If a ClientHello with a cookie is received then B<s_server> will connect to
316 that peer and complete the handshake.
320 Switch on asynchronous mode. Cryptographic operations will be performed
321 asynchronously. This will only have an effect if an asynchronous capable engine
322 is also used via the B<-engine> option. For test purposes the dummy async engine
323 (dasync) can be used (if available).
327 There are several known bug in SSL and TLS implementations. Adding this
328 option enables various workarounds.
332 Enable negotiation of TLS compression.
333 This option was introduced in OpenSSL 1.1.0.
334 TLS compression is not recommended and is off by default as of
339 Disable negotiation of TLS compression.
340 TLS compression is not recommended and is off by default as of
345 Provide a brief summary of connection parameters instead of the normal verbose
348 =item B<-cipher cipherlist>
350 This allows the cipher list used by the server to be modified. When
351 the client sends a list of supported ciphers the first client cipher
352 also included in the server list is used. Because the client specifies
353 the preference order, the order of the server cipherlist irrelevant. See
354 the B<ciphers> command for more information.
358 Use the server's cipher preferences, rather than the client's preferences.
360 =item B<-tlsextdebug>
362 Print a hex dump of any TLS extensions received from the server.
366 Disable RFC4507bis session ticket support.
370 Sends a status message back to the client when it connects. This includes
371 information about the ciphers used and various session parameters.
372 The output is in HTML format so this option will normally be used with a
377 Emulates a simple web server. Pages will be resolved relative to the
378 current directory, for example if the URL https://myhost/page.html is
379 requested the file ./page.html will be loaded.
383 Emulates a simple web server. Pages will be resolved relative to the
384 current directory, for example if the URL https://myhost/page.html is
385 requested the file ./page.html will be loaded. The files loaded are
386 assumed to contain a complete and correct HTTP response (lines that
387 are part of the HTTP response line and headers must end with CRLF).
391 Simple test server which just reverses the text received from the client
392 and sends it back to the server. Also sets B<-brief>.
396 Specifying an engine (by its unique B<id> string) will cause B<s_server>
397 to attempt to obtain a functional reference to the specified engine,
398 thus initialising it if needed. The engine will then be set as the default
399 for all available algorithms.
401 =item B<-id_prefix arg>
403 Generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
404 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
405 servers, when each of which might be generating a unique range of session
406 IDs (eg. with a certain prefix).
408 =item B<-rand file(s)>
410 A file or files containing random data used to seed the random number
411 generator, or an EGD socket (see L<RAND_egd(3)>).
412 Multiple files can be specified separated by a OS-dependent character.
413 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
416 =item B<-serverinfo file>
418 A file containing one or more blocks of PEM data. Each PEM block
419 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
420 followed by "length" bytes of extension data). If the client sends
421 an empty TLS ClientHello extension matching the type, the corresponding
422 ServerHello extension will be returned.
424 =item B<-no_resumption_on_reneg>
426 Set the B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> option.
430 Enables certificate status request support (aka OCSP stapling).
432 =item B<-status_verbose>
434 Enables certificate status request support (aka OCSP stapling) and gives
435 a verbose printout of the OCSP response.
437 =item B<-status_timeout nsec>
439 Sets the timeout for OCSP response to B<nsec> seconds.
441 =item B<-status_url url>
443 Sets a fallback responder URL to use if no responder URL is present in the
444 server certificate. Without this option an error is returned if the server
445 certificate does not contain a responder address.
447 =item B<-nextprotoneg protocols>
449 Enable Next Protocol Negotiation TLS extension and provide a
450 comma-separated list of supported protocol names.
451 The list should contain most wanted protocols first.
452 Protocol names are printable ASCII strings, for example "http/1.1" or
457 =head1 CONNECTED COMMANDS
459 If a connection request is established with an SSL client and neither the
460 B<-www> nor the B<-WWW> option has been used then normally any data received
461 from the client is displayed and any key presses will be sent to the client.
463 Certain single letter commands are also recognized which perform special
464 operations: these are listed below.
470 end the current SSL connection but still accept new connections.
474 end the current SSL connection and exit.
478 renegotiate the SSL session.
482 renegotiate the SSL session and request a client certificate.
486 send some plain text down the underlying TCP connection: this should
487 cause the client to disconnect due to a protocol violation.
491 print out some session cache status information.
497 B<s_server> can be used to debug SSL clients. To accept connections from
498 a web browser the command:
500 openssl s_server -accept 443 -www
502 can be used for example.
504 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
505 suites, so they cannot connect to servers which don't use a certificate
506 carrying an RSA key or a version of OpenSSL with RSA disabled.
508 Although specifying an empty list of CAs when requesting a client certificate
509 is strictly speaking a protocol violation, some SSL clients interpret this to
510 mean any CA is acceptable. This is useful for debugging purposes.
512 The session parameters can printed out using the B<sess_id> program.
516 Because this program has a lot of options and also because some of the
517 techniques used are rather old, the C source of B<s_server> is rather hard to
518 read and not a model of how things should be done.
519 A typical SSL server program would be much simpler.
521 The output of common ciphers is wrong: it just gives the list of ciphers that
522 OpenSSL recognizes and the client supports.
524 There should be a way for the B<s_server> program to print out details of any
525 unknown cipher suites a client says it supports.
529 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
533 The -no_alt_chains options was first added to OpenSSL 1.1.0.