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>]
92 [B<-no_resumption_on_reneg>]
95 [B<-status_timeout nsec>]
97 [B<-nextprotoneg protocols>]
101 The B<s_server> command implements a generic SSL/TLS server which listens
102 for connections on a given port using SSL/TLS.
106 In addition to the options below the B<s_server> utility also supports the
107 common and server only options documented in the
108 L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS> manual
113 =item B<-accept port>
115 the TCP port to listen on for connections. If not specified 4433 is used.
117 =item B<-naccept count>
119 The server will exit after receiving B<number> connections, default unlimited.
123 sets the SSL context id. It can be given any string value. If this option
124 is not present a default value will be used.
126 =item B<-cert certname>
128 The certificate to use, most servers cipher suites require the use of a
129 certificate and some require a certificate with a certain public key type:
130 for example the DSS cipher suites require a certificate containing a DSS
131 (DSA) key. If not specified then the filename "server.pem" will be used.
133 =item B<-certform format>
135 The certificate format to use: DER or PEM. PEM is the default.
137 =item B<-key keyfile>
139 The private key to use. If not specified then the certificate file will
142 =item B<-keyform format>
144 The private format to use: DER or PEM. PEM is the default.
148 the private key password source. For more information about the format of B<arg>
149 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
151 =item B<-dcert filename>, B<-dkey keyname>
153 specify an additional certificate and private key, these behave in the
154 same manner as the B<-cert> and B<-key> options except there is no default
155 if they are not specified (no additional certificate and key is used). As
156 noted above some cipher suites require a certificate containing a key of
157 a certain type. Some cipher suites need a certificate carrying an RSA key
158 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
159 a server can support clients which only support RSA or DSS cipher suites
160 by using an appropriate certificate.
162 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
164 additional certificate and private key format and passphrase respectively.
168 if this option is set then no certificate is used. This restricts the
169 cipher suites available to the anonymous ones (currently just anonymous
172 =item B<-dhparam filename>
174 the DH parameter file to use. The ephemeral DH cipher suites generate keys
175 using a set of DH parameters. If not specified then an attempt is made to
176 load the parameters from the server certificate file. If this fails then
177 a static set of parameters hard coded into the s_server program will be used.
181 if this option is set then no DH parameters will be loaded effectively
182 disabling the ephemeral DH cipher suites.
184 =item B<-crl_check>, B<-crl_check_all>
186 Check the peer certificate has not been revoked by its CA.
187 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
188 option all CRLs of all CAs in the chain are checked.
190 =item B<-CApath directory>
192 The directory to use for client certificate verification. This directory
193 must be in "hash format", see B<verify> for more information. These are
194 also used when building the server certificate chain.
196 =item B<-CAfile file>
198 A file containing trusted certificates to use during client authentication
199 and to use when attempting to build the server certificate chain. The list
200 is also used in the list of acceptable client CAs passed to the client when
201 a certificate is requested.
205 Do not load the trusted CA certificates from the default file location
209 Do not load the trusted CA certificates from the default directory location
211 =item B<-verify depth>, B<-Verify depth>
213 The verify depth to use. This specifies the maximum length of the
214 client certificate chain and makes the server request a certificate from
215 the client. With the B<-verify> option a certificate is requested but the
216 client does not have to send one, with the B<-Verify> option the client
217 must supply a certificate or an error occurs.
219 If the ciphersuite cannot request a client certificate (for example an
220 anonymous ciphersuite or PSK) this option has no effect.
222 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
223 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
224 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
225 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
226 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
227 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
229 Set different peer certificate verification options.
230 See the L<verify(1)> manual page for details.
232 =item B<-verify_return_error>
234 Verification errors normally just print a message but allow the
235 connection to continue, for debugging purposes.
236 If this option is used, then verification errors close the connection.
240 prints out the SSL session states.
244 print extensive debugging information including a hex dump of all traffic.
248 show all protocol messages with hex dump.
252 show verbose trace output of protocol messages. OpenSSL needs to be compiled
253 with B<enable-ssl-trace> for this option to work.
257 file to send output of B<-msg> or B<-trace> to, default standard output.
261 tests non blocking I/O
265 turns on non blocking I/O
269 this option translated a line feed from the terminal into CR+LF.
273 inhibit printing of session and certificate information.
275 =item B<-psk_hint hint>
277 Use the PSK identity hint B<hint> when using a PSK cipher suite.
281 Use the PSK key B<key> when using a PSK cipher suite. The key is
282 given as a hexadecimal number without leading 0x, for example -psk
285 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
287 these options disable the use of certain SSL or TLS protocols. By default
288 the initial handshake uses a method which should be compatible with all
289 servers and permit them to use SSL v3 or TLS as appropriate.
291 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
293 these options make s_server use DTLS protocols instead of TLS. With B<-dtls>
294 s_server will negotiate any supported DTLS protcol version, whilst B<-dtls1> and
295 B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 respectively.
299 this option can only be used in conjunction with one of the DTLS options above.
300 With this option s_server will listen on a UDP port for incoming connections.
301 Any ClientHellos that arrive will be checked to see if they have a cookie in
302 them or not. Any without a cookie will be responded to with a
303 HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
304 will connect to that peer and complete the handshake.
308 switch on asynchronous mode. Cryptographic operations will be performed
309 asynchronously. This will only have an effect if an asynchronous capable engine
310 is also used via the B<-engine> option. For test purposes the dummy async engine
311 (dasync) can be used (if available).
315 there are several known bug in SSL and TLS implementations. Adding this
316 option enables various workarounds.
320 Enable negotiation of TLS compression.
321 This option was introduced in OpenSSL 1.1.0.
322 TLS compression is not recommended and is off by default as of
327 Disable negotiation of TLS compression.
328 TLS compression is not recommended and is off by default as of
333 only provide a brief summary of connection parameters instead of the
334 normal verbose output.
336 =item B<-cipher cipherlist>
338 this allows the cipher list used by the server to be modified. When
339 the client sends a list of supported ciphers the first client cipher
340 also included in the server list is used. Because the client specifies
341 the preference order, the order of the server cipherlist irrelevant. See
342 the B<ciphers> command for more information.
346 use the server's cipher preferences, rather than the client's preferences.
348 =item B<-tlsextdebug>
350 print out a hex dump of any TLS extensions received from the server.
354 disable RFC4507bis session ticket support.
358 sends a status message back to the client when it connects. This includes
359 lots of information about the ciphers used and various session parameters.
360 The output is in HTML format so this option will normally be used with a
365 emulates a simple web server. Pages will be resolved relative to the
366 current directory, for example if the URL https://myhost/page.html is
367 requested the file ./page.html will be loaded.
371 emulates a simple web server. Pages will be resolved relative to the
372 current directory, for example if the URL https://myhost/page.html is
373 requested the file ./page.html will be loaded. The files loaded are
374 assumed to contain a complete and correct HTTP response (lines that
375 are part of the HTTP response line and headers must end with CRLF).
379 simple test server which just reverses the text received from the client
380 and sends it back to the server. Also sets B<-brief>.
384 specifying an engine (by its unique B<id> string) will cause B<s_server>
385 to attempt to obtain a functional reference to the specified engine,
386 thus initialising it if needed. The engine will then be set as the default
387 for all available algorithms.
389 =item B<-id_prefix arg>
391 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
392 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
393 servers, when each of which might be generating a unique range of session
394 IDs (eg. with a certain prefix).
396 =item B<-rand file(s)>
398 a file or files containing random data used to seed the random number
399 generator, or an EGD socket (see L<RAND_egd(3)>).
400 Multiple files can be specified separated by a OS-dependent character.
401 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
404 =item B<-serverinfo file>
406 a file containing one or more blocks of PEM data. Each PEM block
407 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
408 followed by "length" bytes of extension data). If the client sends
409 an empty TLS ClientHello extension matching the type, the corresponding
410 ServerHello extension will be returned.
412 =item B<-no_resumption_on_reneg>
414 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
418 enables certificate status request support (aka OCSP stapling).
420 =item B<-status_verbose>
422 enables certificate status request support (aka OCSP stapling) and gives
423 a verbose printout of the OCSP response.
425 =item B<-status_timeout nsec>
427 sets the timeout for OCSP response to B<nsec> seconds.
429 =item B<-status_url url>
431 sets a fallback responder URL to use if no responder URL is present in the
432 server certificate. Without this option an error is returned if the server
433 certificate does not contain a responder address.
435 =item B<-nextprotoneg protocols>
437 enable Next Protocol Negotiation TLS extension and provide a
438 comma-separated list of supported protocol names.
439 The list should contain most wanted protocols first.
440 Protocol names are printable ASCII strings, for example "http/1.1" or
445 =head1 CONNECTED COMMANDS
447 If a connection request is established with an SSL client and neither the
448 B<-www> nor the B<-WWW> option has been used then normally any data received
449 from the client is displayed and any key presses will be sent to the client.
451 Certain single letter commands are also recognized which perform special
452 operations: these are listed below.
458 end the current SSL connection but still accept new connections.
462 end the current SSL connection and exit.
466 renegotiate the SSL session.
470 renegotiate the SSL session and request a client certificate.
474 send some plain text down the underlying TCP connection: this should
475 cause the client to disconnect due to a protocol violation.
479 print out some session cache status information.
485 B<s_server> can be used to debug SSL clients. To accept connections from
486 a web browser the command:
488 openssl s_server -accept 443 -www
490 can be used for example.
492 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
493 suites, so they cannot connect to servers which don't use a certificate
494 carrying an RSA key or a version of OpenSSL with RSA disabled.
496 Although specifying an empty list of CAs when requesting a client certificate
497 is strictly speaking a protocol violation, some SSL clients interpret this to
498 mean any CA is acceptable. This is useful for debugging purposes.
500 The session parameters can printed out using the B<sess_id> program.
504 Because this program has a lot of options and also because some of
505 the techniques used are rather old, the C source of s_server is rather
506 hard to read and not a model of how things should be done. A typical
507 SSL server program would be much simpler.
509 The output of common ciphers is wrong: it just gives the list of ciphers that
510 OpenSSL recognizes and the client supports.
512 There should be a way for the B<s_server> program to print out details of any
513 unknown cipher suites a client says it supports.
517 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
521 The -no_alt_chains options was first added to OpenSSL 1.1.0.