6 s_server - SSL/TLS server program
10 B<openssl> B<s_server>
19 [B<-dhparam filename>]
25 [B<-CApath directory>]
28 [B<-cipher cipherlist>]
46 The B<s_server> command implements a generic SSL/TLS server which listens
47 for connections on a given port using SSL/TLS.
55 the TCP port to listen on for connections. If not specified 4433 is used.
59 sets the SSL context id. It can be given any string value. If this option
60 is not present a default value will be used.
62 =item B<-cert certname>
64 The certificate to use, most servers cipher suites require the use of a
65 certificate and some require a certificate with a certain public key type:
66 for example the DSS cipher suites require a certificate containing a DSS
67 (DSA) key. If not specified then the filename "server.pem" will be used.
71 The private key to use. If not specified then the certificate file will
74 =item B<-dcert filename>, B<-dkey keyname>
76 specify an additional certificate and private key, these behave in the
77 same manner as the B<-cert> and B<-key> options except there is no default
78 if they are not specified (no additional certificate and key is used). As
79 noted above some cipher suites require a certificate containing a key of
80 a certain type. Some cipher suites need a certificate carrying an RSA key
81 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
82 a server can support clients which only support RSA or DSS cipher suites
83 by using an appropriate certificate.
87 if this option is set then no certificate is used. This restricts the
88 cipher suites available to the anonymous ones (currently just anonymous
91 =item B<-dhparam filename>
93 the DH parameter file to use. The ephemeral DH cipher suites generate keys
94 using a set of DH parameters. If not specified then an attempt is made to
95 load the parameters from the server certificate file. If this fails then
96 a static set of parameters hard coded into the s_server program will be used.
100 if this option is set then no DH parameters will be loaded effectively
101 disabling the ephemeral DH cipher suites.
105 certain export cipher suites sometimes use a temporary RSA key, this option
106 disables temporary RSA key generation.
108 =item B<-verify depth>, B<-Verify depth>
110 The verify depth to use. This specifies the maximum length of the
111 client certificate chain and makes the server request a certificate from
112 the client. With the B<-verify> option a certificate is requested but the
113 client does not have to send one, with the B<-Verify> option the client
114 must supply a certificate or an error occurs.
116 =item B<-CApath directory>
118 The directory to use for client certificate verification. This directory
119 must be in "hash format", see B<verify> for more information. These are
120 also used when building the server certificate chain.
122 =item B<-CAfile file>
124 A file containing trusted certificates to use during client authentication
125 and to use when attempting to build the server certificate chain. The list
126 is also used in the list of acceptable client CAs passed to the client when
127 a certificate is requested.
131 prints out the SSL session states.
135 print extensive debugging information including a hex dump of all traffic.
139 tests non blocking I/O
143 turns on non blocking I/O
147 this option translated a line feed from the terminal into CR+LF.
151 inhibit printing of session and certificate information.
153 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
155 these options disable the use of certain SSL or TLS protocols. By default
156 the initial handshake uses a method which should be compatible with all
157 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
161 there are several known bug in SSL and TLS implementations. Adding this
162 option enables various workarounds.
166 this option enables a further workaround for some some early Netscape
169 =item B<-cipher cipherlist>
171 this allows the cipher list used by the server to be modified. When
172 the client sends a list of supported ciphers the first client cipher
173 also included in the server list is used. Because the client specifies
174 the preference order, the order of the server cipherlist irrelevant. See
175 the B<ciphers> command for more information.
179 sends a status message back to the client when it connects. This includes
180 lots of information about the ciphers used and various session parameters.
181 The output is in HTML format so this option will normally be used with a
186 emulates a simple web server. Pages will be resolved relative to the
187 current directory, for example if the URL https://myhost/page.html is
188 requested the file ./page.html will be loaded.
192 specifying an engine (by it's unique B<id> string) will cause B<s_server>
193 to attempt to obtain a functional reference to the specified engine,
194 thus initialising it if needed. The engine will then be set as the default
195 for all available algorithms.
199 =head1 CONNECTED COMMANDS
201 If a connection request is established with an SSL client and neither the
202 B<-www> nor the B<-WWW> option has been used then normally any data received
203 from the client is displayed and any key presses will be sent to the client.
205 Certain single letter commands are also recognized which perform special
206 operations: these are listed below.
212 end the current SSL connection but still accept new connections.
216 end the current SSL connection and exit.
220 renegotiate the SSL session.
224 renegotiate the SSL session and request a client certificate.
228 send some plain text down the underlying TCP connection: this should
229 cause the client to disconnect due to a protocol violation.
233 print out some session cache status information.
239 B<s_server> can be used to debug SSL clients. To accept connections from
240 a web browser the command:
242 openssl s_server -accept 443 -www
244 can be used for example.
246 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
247 suites, so they cannot connect to servers which don't use a certificate
248 carrying an RSA key or a version of OpenSSL with RSA disabled.
250 Although specifying an empty list of CAs when requesting a client certificate
251 is strictly speaking a protocol violation, some SSL clients interpret this to
252 mean any CA is acceptable. This is useful for debugging purposes.
254 The session parameters can printed out using the B<sess_id> program.
258 Because this program has a lot of options and also because some of
259 the techniques used are rather old, the C source of s_server is rather
260 hard to read and not a model of how things should be done. A typical
261 SSL server program would be much simpler.
263 The output of common ciphers is wrong: it just gives the list of ciphers that
264 OpenSSL recognizes and the client supports.
266 There should be a way for the B<s_server> program to print out details of any
267 unknown cipher suites a client says it supports.
271 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>