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<-client_sigalgs sigalglist>]
39 [B<-named_curve curve>]
40 [B<-cipher cipherlist>]
62 [B<-no_resumption_on_reneg>]
65 [B<-status_timeout nsec>]
68 [B<-nextprotoneg protocols>]
72 The B<s_server> command implements a generic SSL/TLS server which listens
73 for connections on a given port using SSL/TLS.
81 the TCP port to listen on for connections. If not specified 4433 is used.
85 sets the SSL context id. It can be given any string value. If this option
86 is not present a default value will be used.
88 =item B<-cert certname>
90 The certificate to use, most servers cipher suites require the use of a
91 certificate and some require a certificate with a certain public key type:
92 for example the DSS cipher suites require a certificate containing a DSS
93 (DSA) key. If not specified then the filename "server.pem" will be used.
95 =item B<-certform format>
97 The certificate format to use: DER or PEM. PEM is the default.
101 The private key to use. If not specified then the certificate file will
104 =item B<-keyform format>
106 The private format to use: DER or PEM. PEM is the default.
110 the private key password source. For more information about the format of B<arg>
111 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
113 =item B<-dcert filename>, B<-dkey keyname>
115 specify an additional certificate and private key, these behave in the
116 same manner as the B<-cert> and B<-key> options except there is no default
117 if they are not specified (no additional certificate and key is used). As
118 noted above some cipher suites require a certificate containing a key of
119 a certain type. Some cipher suites need a certificate carrying an RSA key
120 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
121 a server can support clients which only support RSA or DSS cipher suites
122 by using an appropriate certificate.
124 =item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
126 additional certificate and private key format and passphrase respectively.
130 if this option is set then no certificate is used. This restricts the
131 cipher suites available to the anonymous ones (currently just anonymous
134 =item B<-dhparam filename>
136 the DH parameter file to use. The ephemeral DH cipher suites generate keys
137 using a set of DH parameters. If not specified then an attempt is made to
138 load the parameters from the server certificate file. If this fails then
139 a static set of parameters hard coded into the s_server program will be used.
143 if this option is set then no DH parameters will be loaded effectively
144 disabling the ephemeral DH cipher suites.
148 certain export cipher suites sometimes use a temporary RSA key, this option
149 disables temporary RSA key generation.
151 =item B<-verify depth>, B<-Verify depth>
153 The verify depth to use. This specifies the maximum length of the
154 client certificate chain and makes the server request a certificate from
155 the client. With the B<-verify> option a certificate is requested but the
156 client does not have to send one, with the B<-Verify> option the client
157 must supply a certificate or an error occurs.
159 If the ciphersuite cannot request a client certificate (for example an
160 anonymous ciphersuite or PSK) this option has no effect.
162 =item B<-crl_check>, B<-crl_check_all>
164 Check the peer certificate has not been revoked by its CA.
165 The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
166 option all CRLs of all CAs in the chain are checked.
168 =item B<-CApath directory>
170 The directory to use for client certificate verification. This directory
171 must be in "hash format", see B<verify> for more information. These are
172 also used when building the server certificate chain.
174 =item B<-CAfile file>
176 A file containing trusted certificates to use during client authentication
177 and to use when attempting to build the server certificate chain. The list
178 is also used in the list of acceptable client CAs passed to the client when
179 a certificate is requested.
181 =item B<-no_alt_chains>
183 See the L<B<verify>|verify(1)> manual page for details.
187 prints out the SSL session states.
191 print extensive debugging information including a hex dump of all traffic.
195 show all protocol messages with hex dump.
199 tests non blocking I/O
203 turns on non blocking I/O
207 this option translated a line feed from the terminal into CR+LF.
211 inhibit printing of session and certificate information.
213 =item B<-psk_hint hint>
215 Use the PSK identity hint B<hint> when using a PSK cipher suite.
219 Use the PSK key B<key> when using a PSK cipher suite. The key is
220 given as a hexadecimal number without leading 0x, for example -psk
223 =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>
225 These options require or disable the use of the specified SSL or TLS protocols.
226 By default the initial handshake uses a I<version-flexible> method which will
227 negotiate the highest mutually supported protocol version.
231 there are several known bug in SSL and TLS implementations. Adding this
232 option enables various workarounds.
236 this option enables a further workaround for some some early Netscape
239 =item B<-client_sigalgs sigalglist>
241 Signature algorithms to support for client certificate authentication
242 (colon-separated list)
244 =item B<-named_curve curve>
246 Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
247 For a list of all possible curves, use:
249 $ openssl ecparam -list_curves
251 =item B<-cipher cipherlist>
253 this allows the cipher list used by the server to be modified. When
254 the client sends a list of supported ciphers the first client cipher
255 also included in the server list is used. Because the client specifies
256 the preference order, the order of the server cipherlist irrelevant. See
257 the B<ciphers> command for more information.
261 use the server's cipher preferences, rather than the client's preferences.
263 =item B<-tlsextdebug>
265 print out a hex dump of any TLS extensions received from the server.
269 disable RFC4507bis session ticket support.
273 sends a status message back to the client when it connects. This includes
274 lots of information about the ciphers used and various session parameters.
275 The output is in HTML format so this option will normally be used with a
280 emulates a simple web server. Pages will be resolved relative to the
281 current directory, for example if the URL https://myhost/page.html is
282 requested the file ./page.html will be loaded.
286 emulates a simple web server. Pages will be resolved relative to the
287 current directory, for example if the URL https://myhost/page.html is
288 requested the file ./page.html will be loaded. The files loaded are
289 assumed to contain a complete and correct HTTP response (lines that
290 are part of the HTTP response line and headers must end with CRLF).
294 specifying an engine (by its unique B<id> string) will cause B<s_server>
295 to attempt to obtain a functional reference to the specified engine,
296 thus initialising it if needed. The engine will then be set as the default
297 for all available algorithms.
299 =item B<-id_prefix arg>
301 generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
302 for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
303 servers, when each of which might be generating a unique range of session
304 IDs (eg. with a certain prefix).
306 =item B<-rand file(s)>
308 a file or files containing random data used to seed the random number
309 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
310 Multiple files can be specified separated by a OS-dependent character.
311 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
314 =item B<-serverinfo file>
316 a file containing one or more blocks of PEM data. Each PEM block
317 must encode a TLS ServerHello extension (2 bytes type, 2 bytes length,
318 followed by "length" bytes of extension data). If the client sends
319 an empty TLS ClientHello extension matching the type, the corresponding
320 ServerHello extension will be returned.
322 =item B<-no_resumption_on_reneg>
324 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.
328 enables certificate status request support (aka OCSP stapling).
330 =item B<-status_verbose>
332 enables certificate status request support (aka OCSP stapling) and gives
333 a verbose printout of the OCSP response.
335 =item B<-status_timeout nsec>
337 sets the timeout for OCSP response to B<nsec> seconds.
339 =item B<-status_url url>
341 sets a fallback responder URL to use if no responder URL is present in the
342 server certificate. Without this option an error is returned if the server
343 certificate does not contain a responder address.
345 =item B<-alpn protocols>, B<-nextprotoneg protocols>
347 these flags enable the
348 Enable the Application-Layer Protocol Negotiation or Next Protocol
349 Negotiation extension, respectively. ALPN is the IETF standard and
351 The B<protocols> list is a
352 comma-separated list of supported protocol names.
353 The list should contain most wanted protocols first.
354 Protocol names are printable ASCII strings, for example "http/1.1" or
359 =head1 CONNECTED COMMANDS
361 If a connection request is established with an SSL client and neither the
362 B<-www> nor the B<-WWW> option has been used then normally any data received
363 from the client is displayed and any key presses will be sent to the client.
365 Certain single letter commands are also recognized which perform special
366 operations: these are listed below.
372 end the current SSL connection but still accept new connections.
376 end the current SSL connection and exit.
380 renegotiate the SSL session.
384 renegotiate the SSL session and request a client certificate.
388 send some plain text down the underlying TCP connection: this should
389 cause the client to disconnect due to a protocol violation.
393 print out some session cache status information.
399 B<s_server> can be used to debug SSL clients. To accept connections from
400 a web browser the command:
402 openssl s_server -accept 443 -www
404 can be used for example.
406 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
407 suites, so they cannot connect to servers which don't use a certificate
408 carrying an RSA key or a version of OpenSSL with RSA disabled.
410 Although specifying an empty list of CAs when requesting a client certificate
411 is strictly speaking a protocol violation, some SSL clients interpret this to
412 mean any CA is acceptable. This is useful for debugging purposes.
414 The session parameters can printed out using the B<sess_id> program.
418 Because this program has a lot of options and also because some of
419 the techniques used are rather old, the C source of s_server is rather
420 hard to read and not a model of how things should be done. A typical
421 SSL server program would be much simpler.
423 The output of common ciphers is wrong: it just gives the list of ciphers that
424 OpenSSL recognizes and the client supports.
426 There should be a way for the B<s_server> program to print out details of any
427 unknown cipher suites a client says it supports.
431 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>
435 The -no_alt_chains options was first added to OpenSSL 1.0.2b.