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>]
47 The B<s_server> command implements a generic SSL/TLS server which listens
48 for connections on a given port using SSL/TLS.
56 the TCP port to listen on for connections. If not specified 4433 is used.
60 sets the SSL context id. It can be given any string value. If this option
61 is not present a default value will be used.
63 =item B<-cert certname>
65 The certificate to use, most servers cipher suites require the use of a
66 certificate and some require a certificate with a certain public key type:
67 for example the DSS cipher suites require a certificate containing a DSS
68 (DSA) key. If not specified then the filename "server.pem" will be used.
72 The private key to use. If not specified then the certificate file will
75 =item B<-dcert filename>, B<-dkey keyname>
77 specify an additional certificate and private key, these behave in the
78 same manner as the B<-cert> and B<-key> options except there is no default
79 if they are not specified (no additional certificate and key is used). As
80 noted above some cipher suites require a certificate containing a key of
81 a certain type. Some cipher suites need a certificate carrying an RSA key
82 and some a DSS (DSA) key. By using RSA and DSS certificates and keys
83 a server can support clients which only support RSA or DSS cipher suites
84 by using an appropriate certificate.
88 if this option is set then no certificate is used. This restricts the
89 cipher suites available to the anonymous ones (currently just anonymous
92 =item B<-dhparam filename>
94 the DH parameter file to use. The ephemeral DH cipher suites generate keys
95 using a set of DH parameters. If not specified then an attempt is made to
96 load the parameters from the server certificate file. If this fails then
97 a static set of parameters hard coded into the s_server program will be used.
101 if this option is set then no DH parameters will be loaded effectively
102 disabling the ephemeral DH cipher suites.
106 certain export cipher suites sometimes use a temporary RSA key, this option
107 disables temporary RSA key generation.
109 =item B<-verify depth>, B<-Verify depth>
111 The verify depth to use. This specifies the maximum length of the
112 client certificate chain and makes the server request a certificate from
113 the client. With the B<-verify> option a certificate is requested but the
114 client does not have to send one, with the B<-Verify> option the client
115 must supply a certificate or an error occurs.
117 =item B<-CApath directory>
119 The directory to use for client certificate verification. This directory
120 must be in "hash format", see B<verify> for more information. These are
121 also used when building the server certificate chain.
123 =item B<-CAfile file>
125 A file containing trusted certificates to use during client authentication
126 and to use when attempting to build the server certificate chain. The list
127 is also used in the list of acceptable client CAs passed to the client when
128 a certificate is requested.
132 prints out the SSL session states.
136 print extensive debugging information including a hex dump of all traffic.
140 tests non blocking I/O
144 turns on non blocking I/O
148 this option translated a line feed from the terminal into CR+LF.
152 inhibit printing of session and certificate information.
154 =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
156 these options disable the use of certain SSL or TLS protocols. By default
157 the initial handshake uses a method which should be compatible with all
158 servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
162 there are several known bug in SSL and TLS implementations. Adding this
163 option enables various workarounds.
167 this option enables a further workaround for some some early Netscape
170 =item B<-cipher cipherlist>
172 this allows the cipher list used by the server to be modified. When
173 the client sends a list of supported ciphers the first client cipher
174 also included in the server list is used. Because the client specifies
175 the preference order, the order of the server cipherlist irrelevant. See
176 the B<ciphers> command for more information.
180 sends a status message back to the client when it connects. This includes
181 lots of information about the ciphers used and various session parameters.
182 The output is in HTML format so this option will normally be used with a
187 emulates a simple web server. Pages will be resolved relative to the
188 current directory, for example if the URL https://myhost/page.html is
189 requested the file ./page.html will be loaded.
193 specifying an engine (by it's unique B<id> string) will cause B<s_server>
194 to attempt to obtain a functional reference to the specified engine,
195 thus initialising it if needed. The engine will then be set as the default
196 for all available algorithms.
198 =item B<-rand file(s)>
200 a file or files containing random data used to seed the random number
201 generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
202 Multiple files can be specified separated by a OS-dependent character.
203 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
208 =head1 CONNECTED COMMANDS
210 If a connection request is established with an SSL client and neither the
211 B<-www> nor the B<-WWW> option has been used then normally any data received
212 from the client is displayed and any key presses will be sent to the client.
214 Certain single letter commands are also recognized which perform special
215 operations: these are listed below.
221 end the current SSL connection but still accept new connections.
225 end the current SSL connection and exit.
229 renegotiate the SSL session.
233 renegotiate the SSL session and request a client certificate.
237 send some plain text down the underlying TCP connection: this should
238 cause the client to disconnect due to a protocol violation.
242 print out some session cache status information.
248 B<s_server> can be used to debug SSL clients. To accept connections from
249 a web browser the command:
251 openssl s_server -accept 443 -www
253 can be used for example.
255 Most web browsers (in particular Netscape and MSIE) only support RSA cipher
256 suites, so they cannot connect to servers which don't use a certificate
257 carrying an RSA key or a version of OpenSSL with RSA disabled.
259 Although specifying an empty list of CAs when requesting a client certificate
260 is strictly speaking a protocol violation, some SSL clients interpret this to
261 mean any CA is acceptable. This is useful for debugging purposes.
263 The session parameters can printed out using the B<sess_id> program.
267 Because this program has a lot of options and also because some of
268 the techniques used are rather old, the C source of s_server is rather
269 hard to read and not a model of how things should be done. A typical
270 SSL server program would be much simpler.
272 The output of common ciphers is wrong: it just gives the list of ciphers that
273 OpenSSL recognizes and the client supports.
275 There should be a way for the B<s_server> program to print out details of any
276 unknown cipher suites a client says it supports.
280 L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>