6 s_server - SSL/TLS server program
10 B<openssl> B<s_client>
19 [B<-dhparam filename>]
25 [B<-CApath directory>]
28 [B<-cipher cipherlist>]
45 The B<s_server> command implements a generic SSL/TLS server which listens
46 for connections on a given port using SSL/TLS.
54 the TCP port to listen on for connections. If not specified 4433 is used.
58 sets the SSL context id. It can be given any string value. If this option
59 is not present a default value will be used.
61 =item B<-cert certname>
63 The certificate to use, most servers cipher suites require the use of a
64 certificate and some require a certificate with a certain public key type:
65 for example the DSS cipher suites require a certificate containing a DSS
66 (DSA) key. If not specified then the filename "server.pem" will be used.
70 The private key to use. If not specified then the certificate file will
73 =item B<-dcert filename>, B<-dkey keyname>
75 specify an additional certificate and private key, these behave in the
76 same manner as the B<-cert> and B<-key> options except there is no default
77 if they are not specified (no additional certificate and key is used). As
78 noted above some cipher suites require a certificate containing a key of
79 a certain type. Some cipher suites need a certificate carrying an RSA key
80 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
81 a server can support clients which only support RSA or DSS cipher suites
82 by using an appropriate certificate.
86 if this option is set then no certificate is used. This restricts the
87 cipher suites available to the anonymous ones (currently just anonymous
90 =item B<-dhparam filename>
92 the DH parameter file to use. The ephemeral DH cipher suites generate keys
93 using a set of DH parameters. If not specified then an attempt is made to
94 load the parameters from the server certificate file. If this fails then
95 a static set of parameters hard coded into the s_server program will be used.
99 if this option is set then no DH parameters will be loaded effectively
100 disabling the ephemeral DH cipher suites.
104 certain export cipher suites sometimes use a temporary RSA key, this option
105 disables temporary RSA key generation.
107 =item B<-verify depth>, B<-Verify depth>
109 The verify depth to use. This specifies the maximum length of the
110 client certificate chain and makes the server request a certificate from
111 the client. With the B<-verify> option a certificate is requested but the
112 client does not have to send one, with the B<-Verify> option the client
113 must supply a certificate or an error occurs.
115 =item B<-CApath directory>
117 The directory to use for client certificate verification. This directory
118 must be in "hash format", see B<verify> for more information. These are
119 also used when building the server certificate chain.
121 =item B<-CAfile file>
123 A file containing trusted certificates to use during client authentication
124 and to use when attempting to build the server certificate chain. The list
125 is also used in the list of acceptable client CAs passed to the client when
126 a certificate is requested.
130 prints out the SSL session states.
134 print extensive debugging information including a hex dump of all traffic.
138 tests non blocking I/O
142 turns on non blocking I/O
146 this option translated a line feed from the terminal into CR+LF.
150 inhibit printing of session and certificate information.
152 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
154 these options disable the use of certain SSL or TLS protocols. By default
155 the initial handshake uses a method which should be compatible with all
156 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
160 there are several known bug in SSL and TLS implementations. Adding this
161 option enables various workarounds.
165 this option enables a further workaround for some some early Netscape
168 =item B<-cipher cipherlist>
170 this allows the cipher list sent by the client to be modified. See the
171 B<ciphers> command for more information.
175 sends a status message back to the client when it connects. This includes
176 lots of information about the ciphers used and various session parameters.
177 The output is in HTML format so this option will normally be used with a
182 emulates a simple web server. Pages will be resolved relative to the
183 current directory, for example if the URL https://myhost/page.html is
184 requested the file ./page.html will be loaded.
188 =head1 CONNECTED COMMANDS
190 If a connection request is established with an SSL client and neither the
191 B<-www> nor the B<-WWW> option has been used then normally any data received
192 from the client is displayed and any key presses will be sent to the client.
194 Certain single letter commands are also recognised which perform special
195 operations: these are listed below.
201 end the current SSL connection but still accept new connections.
205 end the current SSL connection and exit.
209 renegotiate the SSL session.
213 renegotiate the SSL session and request a client certificate.
217 send some plain text down the underlying TCP connection: this should
218 cause the client to disconnect due to a protocol violation.
222 print out some session cache status information.
228 B<s_server> can be used to debug SSL clients. To accept connections from
229 a web browser the command:
231 openssl s_server -accept 443 -www
233 can be used for example.
235 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
236 suites, so they cannot connect to servers which don't use a certificate
237 carrying an RSA key or a version of OpenSSL with RSA disabled.
239 Although specifying an empty list of CAs when requesting a client certificate
240 is strictly speaking a protocol violation, some SSL clients interpret this to
241 mean any CA is acceptable. This is useful for debugging purposes.
243 The session parameters can printed out using the B<sess_id> program.
247 Because this program has a lot of options and also because some of
248 the techniques used are rather old, the C source of s_server is rather
249 hard to read and not a model of how things should be done. A typical
250 SSL server program would be much simpler.
252 The output of common ciphers is wrong: it just gives the list of ciphers that
253 OpenSSL recognizes and the client supports.
255 There should be a way for the B<s_server> program to print out details of any
256 unknown cipher suites a client says it supports.
260 sess_id(1), s_client(1), ciphers(1)