6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
18 [B<-certform DER|PEM>]
23 [B<-dcertform DER|PEM>]
25 [B<-dkeyform DER|PEM>]
27 [B<-dhparam filename>]
34 [B<-CApath directory>]
38 [B<-cipher cipherlist>]
60 [B<-no_resumption_on_reneg>]
63 [B<-status_timeout nsec>]
66 [B<-nextprotoneg protocols>]
70 The B<s_server> command implements a generic SSL/TLS server which listens
71 for connections on a given port using SSL/TLS.
79 the TCP port to listen on for connections. If not specified 4433 is used.
83 sets the SSL context id. It can be given any string value. If this option
84 is not present a default value will be used.
86 =item B<-cert certname>
88 The certificate to use, most servers cipher suites require the use of a
89 certificate and some require a certificate with a certain public key type:
90 for example the DSS cipher suites require a certificate containing a DSS
91 (DSA) key. If not specified then the filename "server.pem" will be used.
93 =item B<-certform format>
95 The certificate format to use: DER or PEM. PEM is the default.
99 The private key to use. If not specified then the certificate file will
102 =item B<-keyform format>
104 The private format to use: DER or PEM. PEM is the default.
108 the private key password source. For more information about the format of B<arg>
109 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
111 =item B<-dcert filename>, B<-dkey keyname>
113 specify an additional certificate and private key, these behave in the
114 same manner as the B<-cert> and B<-key> options except there is no default
115 if they are not specified (no additional certificate and key is used). As
116 noted above some cipher suites require a certificate containing a key of
117 a certain type. Some cipher suites need a certificate carrying an RSA key
118 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
119 a server can support clients which only support RSA or DSS cipher suites
120 by using an appropriate certificate.
122 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
124 additional certificate and private key format and passphrase respectively.
128 if this option is set then no certificate is used. This restricts the
129 cipher suites available to the anonymous ones (currently just anonymous
132 =item B<-dhparam filename>
134 the DH parameter file to use. The ephemeral DH cipher suites generate keys
135 using a set of DH parameters. If not specified then an attempt is made to
136 load the parameters from the server certificate file. If this fails then
137 a static set of parameters hard coded into the s_server program will be used.
141 if this option is set then no DH parameters will be loaded effectively
142 disabling the ephemeral DH cipher suites.
146 certain export cipher suites sometimes use a temporary RSA key, this option
147 disables temporary RSA key generation.
149 =item B<-verify depth>, B<-Verify depth>
151 The verify depth to use. This specifies the maximum length of the
152 client certificate chain and makes the server request a certificate from
153 the client. With the B<-verify> option a certificate is requested but the
154 client does not have to send one, with the B<-Verify> option the client
155 must supply a certificate or an error occurs.
157 If the ciphersuite cannot request a client certificate (for example an
158 anonymous ciphersuite or PSK) this option has no effect.
160 =item B<-crl_check>, B<-crl_check_all>
162 Check the peer certificate has not been revoked by its CA.
163 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
164 option all CRLs of all CAs in the chain are checked.
166 =item B<-CApath directory>
168 The directory to use for client certificate verification. This directory
169 must be in "hash format", see B<verify> for more information. These are
170 also used when building the server certificate chain.
172 =item B<-CAfile file>
174 A file containing trusted certificates to use during client authentication
175 and to use when attempting to build the server certificate chain. The list
176 is also used in the list of acceptable client CAs passed to the client when
177 a certificate is requested.
179 =item B<-no_alt_chains>
181 See the L<B<verify>|verify(1)> manual page for details.
185 prints out the SSL session states.
189 print extensive debugging information including a hex dump of all traffic.
193 show all protocol messages with hex dump.
197 tests non blocking I/O
201 turns on non blocking I/O
205 this option translated a line feed from the terminal into CR+LF.
209 inhibit printing of session and certificate information.
211 =item B<-psk_hint hint>
213 Use the PSK identity hint B<hint> when using a PSK cipher suite.
217 Use the PSK key B<key> when using a PSK cipher suite. The key is
218 given as a hexadecimal number without leading 0x, for example -psk
221 =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>
223 These options require or disable the use of the specified SSL or TLS protocols.
224 By default the initial handshake uses a I<version-flexible> method which will
225 negotiate the highest mutually supported protocol version.
229 there are several known bug in SSL and TLS implementations. Adding this
230 option enables various workarounds.
234 this option enables a further workaround for some some early Netscape
237 =item B<-cipher cipherlist>
239 this allows the cipher list used by the server to be modified. When
240 the client sends a list of supported ciphers the first client cipher
241 also included in the server list is used. Because the client specifies
242 the preference order, the order of the server cipherlist irrelevant. See
243 the B<ciphers> command for more information.
247 use the server's cipher preferences, rather than the client's preferences.
249 =item B<-tlsextdebug>
251 print out a hex dump of any TLS extensions received from the server.
255 disable RFC4507bis session ticket support.
259 sends a status message back to the client when it connects. This includes
260 lots of information about the ciphers used and various session parameters.
261 The output is in HTML format so this option will normally be used with a
266 emulates a simple web server. Pages will be resolved relative to the
267 current directory, for example if the URL https://myhost/page.html is
268 requested the file ./page.html will be loaded.
272 emulates a simple web server. Pages will be resolved relative to the
273 current directory, for example if the URL https://myhost/page.html is
274 requested the file ./page.html will be loaded. The files loaded are
275 assumed to contain a complete and correct HTTP response (lines that
276 are part of the HTTP response line and headers must end with CRLF).
280 specifying an engine (by its unique B<id> string) will cause B<s_server>
281 to attempt to obtain a functional reference to the specified engine,
282 thus initialising it if needed. The engine will then be set as the default
283 for all available algorithms.
285 =item B<-id_prefix arg>
287 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
288 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
289 servers, when each of which might be generating a unique range of session
290 IDs (eg. with a certain prefix).
292 =item B<-rand file(s)>
294 a file or files containing random data used to seed the random number
295 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
296 Multiple files can be specified separated by a OS-dependent character.
297 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
300 =item B<-serverinfo file>
302 a file containing one or more blocks of PEM data. Each PEM block
303 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
304 followed by "length" bytes of extension data). If the client sends
305 an empty TLS ClientHello extension matching the type, the corresponding
306 ServerHello extension will be returned.
308 =item B<-no_resumption_on_reneg>
310 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
314 enables certificate status request support (aka OCSP stapling).
316 =item B<-status_verbose>
318 enables certificate status request support (aka OCSP stapling) and gives
319 a verbose printout of the OCSP response.
321 =item B<-status_timeout nsec>
323 sets the timeout for OCSP response to B<nsec> seconds.
325 =item B<-status_url url>
327 sets a fallback responder URL to use if no responder URL is present in the
328 server certificate. Without this option an error is returned if the server
329 certificate does not contain a responder address.
331 =item B<-alpn protocols>, B<-nextprotoneg protocols>
333 these flags enable the
334 Enable the Application-Layer Protocol Negotiation or Next Protocol
335 Negotiation extension, respectively. ALPN is the IETF standard and
337 The B<protocols> list is a
338 comma-separated list of supported protocol names.
339 The list should contain most wanted protocols first.
340 Protocol names are printable ASCII strings, for example "http/1.1" or
345 =head1 CONNECTED COMMANDS
347 If a connection request is established with an SSL client and neither the
348 B<-www> nor the B<-WWW> option has been used then normally any data received
349 from the client is displayed and any key presses will be sent to the client.
351 Certain single letter commands are also recognized which perform special
352 operations: these are listed below.
358 end the current SSL connection but still accept new connections.
362 end the current SSL connection and exit.
366 renegotiate the SSL session.
370 renegotiate the SSL session and request a client certificate.
374 send some plain text down the underlying TCP connection: this should
375 cause the client to disconnect due to a protocol violation.
379 print out some session cache status information.
385 B<s_server> can be used to debug SSL clients. To accept connections from
386 a web browser the command:
388 openssl s_server -accept 443 -www
390 can be used for example.
392 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
393 suites, so they cannot connect to servers which don't use a certificate
394 carrying an RSA key or a version of OpenSSL with RSA disabled.
396 Although specifying an empty list of CAs when requesting a client certificate
397 is strictly speaking a protocol violation, some SSL clients interpret this to
398 mean any CA is acceptable. This is useful for debugging purposes.
400 The session parameters can printed out using the B<sess_id> program.
404 Because this program has a lot of options and also because some of
405 the techniques used are rather old, the C source of s_server is rather
406 hard to read and not a model of how things should be done. A typical
407 SSL server program would be much simpler.
409 The output of common ciphers is wrong: it just gives the list of ciphers that
410 OpenSSL recognizes and the client supports.
412 There should be a way for the B<s_server> program to print out details of any
413 unknown cipher suites a client says it supports.
417 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>
421 The -no_alt_chains options was first added to OpenSSL 1.0.2b.