6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
19 [B<-dhparam filename>]
26 [B<-CApath directory>]
29 [B<-cipher cipherlist>]
49 The B<s_server> command implements a generic SSL/TLS server which listens
50 for connections on a given port using SSL/TLS.
58 the TCP port to listen on for connections. If not specified 4433 is used.
62 sets the SSL context id. It can be given any string value. If this option
63 is not present a default value will be used.
65 =item B<-cert certname>
67 The certificate to use, most servers cipher suites require the use of a
68 certificate and some require a certificate with a certain public key type:
69 for example the DSS cipher suites require a certificate containing a DSS
70 (DSA) key. If not specified then the filename "server.pem" will be used.
74 The private key to use. If not specified then the certificate file will
77 =item B<-dcert filename>, B<-dkey keyname>
79 specify an additional certificate and private key, these behave in the
80 same manner as the B<-cert> and B<-key> options except there is no default
81 if they are not specified (no additional certificate and key is used). As
82 noted above some cipher suites require a certificate containing a key of
83 a certain type. Some cipher suites need a certificate carrying an RSA key
84 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
85 a server can support clients which only support RSA or DSS cipher suites
86 by using an appropriate certificate.
90 if this option is set then no certificate is used. This restricts the
91 cipher suites available to the anonymous ones (currently just anonymous
94 =item B<-dhparam filename>
96 the DH parameter file to use. The ephemeral DH cipher suites generate keys
97 using a set of DH parameters. If not specified then an attempt is made to
98 load the parameters from the server certificate file. If this fails then
99 a static set of parameters hard coded into the s_server program will be used.
103 if this option is set then no DH parameters will be loaded effectively
104 disabling the ephemeral DH cipher suites.
108 certain export cipher suites sometimes use a temporary RSA key, this option
109 disables temporary RSA key generation.
111 =item B<-verify depth>, B<-Verify depth>
113 The verify depth to use. This specifies the maximum length of the
114 client certificate chain and makes the server request a certificate from
115 the client. With the B<-verify> option a certificate is requested but the
116 client does not have to send one, with the B<-Verify> option the client
117 must supply a certificate or an error occurs.
119 =item B<-CApath directory>
121 The directory to use for client certificate verification. This directory
122 must be in "hash format", see B<verify> for more information. These are
123 also used when building the server certificate chain.
125 =item B<-CAfile file>
127 A file containing trusted certificates to use during client authentication
128 and to use when attempting to build the server certificate chain. The list
129 is also used in the list of acceptable client CAs passed to the client when
130 a certificate is requested.
134 prints out the SSL session states.
138 print extensive debugging information including a hex dump of all traffic.
142 show all protocol messages with hex dump.
146 tests non blocking I/O
150 turns on non blocking I/O
154 this option translated a line feed from the terminal into CR+LF.
158 inhibit printing of session and certificate information.
160 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
162 these options disable the use of certain SSL or TLS protocols. By default
163 the initial handshake uses a method which should be compatible with all
164 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
168 there are several known bug in SSL and TLS implementations. Adding this
169 option enables various workarounds.
173 this option enables a further workaround for some some early Netscape
176 =item B<-cipher cipherlist>
178 this allows the cipher list used by the server to be modified. When
179 the client sends a list of supported ciphers the first client cipher
180 also included in the server list is used. Because the client specifies
181 the preference order, the order of the server cipherlist irrelevant. See
182 the B<ciphers> command for more information.
186 sends a status message back to the client when it connects. This includes
187 lots of information about the ciphers used and various session parameters.
188 The output is in HTML format so this option will normally be used with a
193 emulates a simple web server. Pages will be resolved relative to the
194 current directory, for example if the URL https://myhost/page.html is
195 requested the file ./page.html will be loaded.
199 emulates a simple web server. Pages will be resolved relative to the
200 current directory, for example if the URL https://myhost/page.html is
201 requested the file ./page.html will be loaded. The files loaded are
202 assumed to contain a complete and correct HTTP response (lines that
203 are part of the HTTP response line and headers must end with CRLF).
207 specifying an engine (by it's unique B<id> string) will cause B<s_server>
208 to attempt to obtain a functional reference to the specified engine,
209 thus initialising it if needed. The engine will then be set as the default
210 for all available algorithms.
212 =item B<-rand file(s)>
214 a file or files containing random data used to seed the random number
215 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
216 Multiple files can be specified separated by a OS-dependent character.
217 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
222 =head1 CONNECTED COMMANDS
224 If a connection request is established with an SSL client and neither the
225 B<-www> nor the B<-WWW> option has been used then normally any data received
226 from the client is displayed and any key presses will be sent to the client.
228 Certain single letter commands are also recognized which perform special
229 operations: these are listed below.
235 end the current SSL connection but still accept new connections.
239 end the current SSL connection and exit.
243 renegotiate the SSL session.
247 renegotiate the SSL session and request a client certificate.
251 send some plain text down the underlying TCP connection: this should
252 cause the client to disconnect due to a protocol violation.
256 print out some session cache status information.
262 B<s_server> can be used to debug SSL clients. To accept connections from
263 a web browser the command:
265 openssl s_server -accept 443 -www
267 can be used for example.
269 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
270 suites, so they cannot connect to servers which don't use a certificate
271 carrying an RSA key or a version of OpenSSL with RSA disabled.
273 Although specifying an empty list of CAs when requesting a client certificate
274 is strictly speaking a protocol violation, some SSL clients interpret this to
275 mean any CA is acceptable. This is useful for debugging purposes.
277 The session parameters can printed out using the B<sess_id> program.
281 Because this program has a lot of options and also because some of
282 the techniques used are rather old, the C source of s_server is rather
283 hard to read and not a model of how things should be done. A typical
284 SSL server program would be much simpler.
286 The output of common ciphers is wrong: it just gives the list of ciphers that
287 OpenSSL recognizes and the client supports.
289 There should be a way for the B<s_server> program to print out details of any
290 unknown cipher suites a client says it supports.
294 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>