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.
190 certain export cipher suites sometimes use a temporary RSA key, this option
191 disables temporary RSA key generation.
193 =item B<-crl_check>, B<-crl_check_all>
195 Check the peer certificate has not been revoked by its CA.
196 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
197 option all CRLs of all CAs in the chain are checked.
199 =item B<-CApath directory>
201 The directory to use for client certificate verification. This directory
202 must be in "hash format", see B<verify> for more information. These are
203 also used when building the server certificate chain.
205 =item B<-CAfile file>
207 A file containing trusted certificates to use during client authentication
208 and to use when attempting to build the server certificate chain. The list
209 is also used in the list of acceptable client CAs passed to the client when
210 a certificate is requested.
214 Do not load the trusted CA certificates from the default file location
218 Do not load the trusted CA certificates from the default directory location
220 =item B<-verify depth>, B<-Verify depth>
222 The verify depth to use. This specifies the maximum length of the
223 client certificate chain and makes the server request a certificate from
224 the client. With the B<-verify> option a certificate is requested but the
225 client does not have to send one, with the B<-Verify> option the client
226 must supply a certificate or an error occurs.
228 If the ciphersuite cannot request a client certificate (for example an
229 anonymous ciphersuite or PSK) this option has no effect.
231 =item B<-attime>, B<-check_ss_sig>, B<explicit_policy>, B<-extended_crl>,
232 B<-ignore_critical>, B<-inhibit_any>, B<-inhibit_map>, B<-issuer_checks>,
233 B<-partial_chain>, B<-policy>, B<-policy_check>, B<-policy_print>, B<-purpose>,
234 B<-suiteB_128>, B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>,
235 B<-no_alt_chains>, B<-use_deltas>, B<-verify_depth>, B<-verify_email>,
236 B<-verify_hostname>, B<-verify_ip>, B<-verify_name>, B<-x509_strict>
238 Set different peer certificate verification options.
239 See the L<verify(1)> manual page for details.
241 =item B<-verify_return_error>
243 Verification errors normally just print a message but allow the
244 connection to continue, for debugging purposes.
245 If this option is used, then verification errors close the connection.
249 prints out the SSL session states.
253 print extensive debugging information including a hex dump of all traffic.
257 show all protocol messages with hex dump.
261 show verbose trace output of protocol messages. OpenSSL needs to be compiled
262 with B<enable-ssl-trace> for this option to work.
266 file to send output of B<-msg> or B<-trace> to, default standard output.
270 tests non blocking I/O
274 turns on non blocking I/O
278 this option translated a line feed from the terminal into CR+LF.
282 inhibit printing of session and certificate information.
284 =item B<-psk_hint hint>
286 Use the PSK identity hint B<hint> when using a PSK cipher suite.
290 Use the PSK key B<key> when using a PSK cipher suite. The key is
291 given as a hexadecimal number without leading 0x, for example -psk
294 =item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>
296 these options disable the use of certain SSL or TLS protocols. By default
297 the initial handshake uses a method which should be compatible with all
298 servers and permit them to use SSL v3 or TLS as appropriate.
300 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
302 these options make s_server use DTLS protocols instead of TLS. With B<-dtls>
303 s_server will negotiate any supported DTLS protcol version, whilst B<-dtls1> and
304 B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 respectively.
308 this option can only be used in conjunction with one of the DTLS options above.
309 With this option s_server will listen on a UDP port for incoming connections.
310 Any ClientHellos that arrive will be checked to see if they have a cookie in
311 them or not. Any without a cookie will be responded to with a
312 HelloVerifyRequest. If a ClientHello with a cookie is received then s_server
313 will connect to that peer and complete the handshake.
317 there are several known bug in SSL and TLS implementations. Adding this
318 option enables various workarounds.
322 only provide a brief summary of connection parameters instead of the
323 normal verbose output.
325 =item B<-cipher cipherlist>
327 this allows the cipher list used by the server to be modified. When
328 the client sends a list of supported ciphers the first client cipher
329 also included in the server list is used. Because the client specifies
330 the preference order, the order of the server cipherlist irrelevant. See
331 the B<ciphers> command for more information.
335 use the server's cipher preferences, rather than the client's preferences.
337 =item B<-tlsextdebug>
339 print out a hex dump of any TLS extensions received from the server.
343 disable RFC4507bis session ticket support.
347 sends a status message back to the client when it connects. This includes
348 lots of information about the ciphers used and various session parameters.
349 The output is in HTML format so this option will normally be used with a
354 emulates a simple web server. Pages will be resolved relative to the
355 current directory, for example if the URL https://myhost/page.html is
356 requested the file ./page.html will be loaded.
360 emulates a simple web server. Pages will be resolved relative to the
361 current directory, for example if the URL https://myhost/page.html is
362 requested the file ./page.html will be loaded. The files loaded are
363 assumed to contain a complete and correct HTTP response (lines that
364 are part of the HTTP response line and headers must end with CRLF).
368 simple test server which just reverses the text received from the client
369 and sends it back to the server. Also sets B<-brief>.
373 specifying an engine (by its unique B<id> string) will cause B<s_server>
374 to attempt to obtain a functional reference to the specified engine,
375 thus initialising it if needed. The engine will then be set as the default
376 for all available algorithms.
378 =item B<-id_prefix arg>
380 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
381 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
382 servers, when each of which might be generating a unique range of session
383 IDs (eg. with a certain prefix).
385 =item B<-rand file(s)>
387 a file or files containing random data used to seed the random number
388 generator, or an EGD socket (see L<RAND_egd(3)>).
389 Multiple files can be specified separated by a OS-dependent character.
390 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
393 =item B<-serverinfo file>
395 a file containing one or more blocks of PEM data. Each PEM block
396 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
397 followed by "length" bytes of extension data). If the client sends
398 an empty TLS ClientHello extension matching the type, the corresponding
399 ServerHello extension will be returned.
401 =item B<-no_resumption_on_reneg>
403 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
407 enables certificate status request support (aka OCSP stapling).
409 =item B<-status_verbose>
411 enables certificate status request support (aka OCSP stapling) and gives
412 a verbose printout of the OCSP response.
414 =item B<-status_timeout nsec>
416 sets the timeout for OCSP response to B<nsec> seconds.
418 =item B<-status_url url>
420 sets a fallback responder URL to use if no responder URL is present in the
421 server certificate. Without this option an error is returned if the server
422 certificate does not contain a responder address.
424 =item B<-nextprotoneg protocols>
426 enable Next Protocol Negotiation TLS extension and provide a
427 comma-separated list of supported protocol names.
428 The list should contain most wanted protocols first.
429 Protocol names are printable ASCII strings, for example "http/1.1" or
434 =head1 CONNECTED COMMANDS
436 If a connection request is established with an SSL client and neither the
437 B<-www> nor the B<-WWW> option has been used then normally any data received
438 from the client is displayed and any key presses will be sent to the client.
440 Certain single letter commands are also recognized which perform special
441 operations: these are listed below.
447 end the current SSL connection but still accept new connections.
451 end the current SSL connection and exit.
455 renegotiate the SSL session.
459 renegotiate the SSL session and request a client certificate.
463 send some plain text down the underlying TCP connection: this should
464 cause the client to disconnect due to a protocol violation.
468 print out some session cache status information.
474 B<s_server> can be used to debug SSL clients. To accept connections from
475 a web browser the command:
477 openssl s_server -accept 443 -www
479 can be used for example.
481 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
482 suites, so they cannot connect to servers which don't use a certificate
483 carrying an RSA key or a version of OpenSSL with RSA disabled.
485 Although specifying an empty list of CAs when requesting a client certificate
486 is strictly speaking a protocol violation, some SSL clients interpret this to
487 mean any CA is acceptable. This is useful for debugging purposes.
489 The session parameters can printed out using the B<sess_id> program.
493 Because this program has a lot of options and also because some of
494 the techniques used are rather old, the C source of s_server is rather
495 hard to read and not a model of how things should be done. A typical
496 SSL server program would be much simpler.
498 The output of common ciphers is wrong: it just gives the list of ciphers that
499 OpenSSL recognizes and the client supports.
501 There should be a way for the B<s_server> program to print out details of any
502 unknown cipher suites a client says it supports.
506 L<sess_id(1)>, L<s_client(1)>, L<ciphers(1)>
510 The -no_alt_chains options was first added to OpenSSL 1.1.0.