1 2=pod 3 4=head1 NAME 5 6s_server - SSL/TLS server program 7 8=head1 SYNOPSIS 9 10B<openssl> B<s_server> 11[B<-accept port>] 12[B<-context id>] 13[B<-verify depth>] 14[B<-Verify depth>] 15[B<-cert filename>] 16[B<-certform DER|PEM>] 17[B<-key keyfile>] 18[B<-keyform DER|PEM>] 19[B<-pass arg>] 20[B<-dcert filename>] 21[B<-dcertform DER|PEM>] 22[B<-dkey keyfile>] 23[B<-dkeyform DER|PEM>] 24[B<-dpass arg>] 25[B<-dhparam filename>] 26[B<-nbio>] 27[B<-nbio_test>] 28[B<-crlf>] 29[B<-debug>] 30[B<-msg>] 31[B<-state>] 32[B<-CApath directory>] 33[B<-CAfile filename>] 34[B<-nocert>] 35[B<-cipher cipherlist>] 36[B<-quiet>] 37[B<-no_tmp_rsa>] 38[B<-ssl2>] 39[B<-ssl3>] 40[B<-tls1>] 41[B<-no_ssl2>] 42[B<-no_ssl3>] 43[B<-no_tls1>] 44[B<-no_dhe>] 45[B<-bugs>] 46[B<-hack>] 47[B<-www>] 48[B<-WWW>] 49[B<-HTTP>] 50[B<-engine id>] 51[B<-id_prefix arg>] 52[B<-rand file(s)>] 53 54=head1 DESCRIPTION 55 56The B<s_server> command implements a generic SSL/TLS server which listens 57for connections on a given port using SSL/TLS. 58 59=head1 OPTIONS 60 61=over 4 62 63=item B<-accept port> 64 65the TCP port to listen on for connections. If not specified 4433 is used. 66 67=item B<-context id> 68 69sets the SSL context id. It can be given any string value. If this option 70is not present a default value will be used. 71 72=item B<-cert certname> 73 74The certificate to use, most servers cipher suites require the use of a 75certificate and some require a certificate with a certain public key type: 76for example the DSS cipher suites require a certificate containing a DSS 77(DSA) key. If not specified then the filename "server.pem" will be used. 78 79=item B<-certform format> 80 81The certificate format to use: DER or PEM. PEM is the default. 82 83=item B<-key keyfile> 84 85The private key to use. If not specified then the certificate file will 86be used. 87 88=item B<-keyform format> 89 90The private format to use: DER or PEM. PEM is the default. 91 92=item B<-pass arg> 93 94the private key password source. For more information about the format of B<arg> 95see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 96 97=item B<-dcert filename>, B<-dkey keyname> 98 99specify an additional certificate and private key, these behave in the 100same manner as the B<-cert> and B<-key> options except there is no default 101if they are not specified (no additional certificate and key is used). As 102noted above some cipher suites require a certificate containing a key of 103a certain type. Some cipher suites need a certificate carrying an RSA key 104and some a DSS (DSA) key. By using RSA and DSS certificates and keys 105a server can support clients which only support RSA or DSS cipher suites 106by using an appropriate certificate. 107 108=item B<-dcertform format>, B<-dkeyform format>, B<-dpass arg> 109 110addtional certificate and private key format and passphrase respectively. 111 112=item B<-nocert> 113 114if this option is set then no certificate is used. This restricts the 115cipher suites available to the anonymous ones (currently just anonymous 116DH). 117 118=item B<-dhparam filename> 119 120the DH parameter file to use. The ephemeral DH cipher suites generate keys 121using a set of DH parameters. If not specified then an attempt is made to 122load the parameters from the server certificate file. If this fails then 123a static set of parameters hard coded into the s_server program will be used. 124 125=item B<-no_dhe> 126 127if this option is set then no DH parameters will be loaded effectively 128disabling the ephemeral DH cipher suites. 129 130=item B<-no_tmp_rsa> 131 132certain export cipher suites sometimes use a temporary RSA key, this option 133disables temporary RSA key generation. 134 135=item B<-verify depth>, B<-Verify depth> 136 137The verify depth to use. This specifies the maximum length of the 138client certificate chain and makes the server request a certificate from 139the client. With the B<-verify> option a certificate is requested but the 140client does not have to send one, with the B<-Verify> option the client 141must supply a certificate or an error occurs. 142 143=item B<-CApath directory> 144 145The directory to use for client certificate verification. This directory 146must be in "hash format", see B<verify> for more information. These are 147also used when building the server certificate chain. 148 149=item B<-CAfile file> 150 151A file containing trusted certificates to use during client authentication 152and to use when attempting to build the server certificate chain. The list 153is also used in the list of acceptable client CAs passed to the client when 154a certificate is requested. 155 156=item B<-state> 157 158prints out the SSL session states. 159 160=item B<-debug> 161 162print extensive debugging information including a hex dump of all traffic. 163 164=item B<-msg> 165 166show all protocol messages with hex dump. 167 168=item B<-nbio_test> 169 170tests non blocking I/O 171 172=item B<-nbio> 173 174turns on non blocking I/O 175 176=item B<-crlf> 177 178this option translated a line feed from the terminal into CR+LF. 179 180=item B<-quiet> 181 182inhibit printing of session and certificate information. 183 184=item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1> 185 186these options disable the use of certain SSL or TLS protocols. By default 187the initial handshake uses a method which should be compatible with all 188servers and permit them to use SSL v3, SSL v2 or TLS as appropriate. 189 190=item B<-bugs> 191 192there are several known bug in SSL and TLS implementations. Adding this 193option enables various workarounds. 194 195=item B<-hack> 196 197this option enables a further workaround for some some early Netscape 198SSL code (?). 199 200=item B<-cipher cipherlist> 201 202this allows the cipher list used by the server to be modified. When 203the client sends a list of supported ciphers the first client cipher 204also included in the server list is used. Because the client specifies 205the preference order, the order of the server cipherlist irrelevant. See 206the B<ciphers> command for more information. 207 208=item B<-www> 209 210sends a status message back to the client when it connects. This includes 211lots of information about the ciphers used and various session parameters. 212The output is in HTML format so this option will normally be used with a 213web browser. 214 215=item B<-WWW> 216 217emulates a simple web server. Pages will be resolved relative to the 218current directory, for example if the URL https://myhost/page.html is 219requested the file ./page.html will be loaded. 220 221=item B<-HTTP> 222 223emulates a simple web server. Pages will be resolved relative to the 224current directory, for example if the URL https://myhost/page.html is 225requested the file ./page.html will be loaded. The files loaded are 226assumed to contain a complete and correct HTTP response (lines that 227are part of the HTTP response line and headers must end with CRLF). 228 229=item B<-engine id> 230 231specifying an engine (by it's unique B<id> string) will cause B<s_server> 232to attempt to obtain a functional reference to the specified engine, 233thus initialising it if needed. The engine will then be set as the default 234for all available algorithms. 235 236=item B<-id_prefix arg> 237 238generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful 239for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple 240servers, when each of which might be generating a unique range of session 241IDs (eg. with a certain prefix). 242 243=item B<-rand file(s)> 244 245a file or files containing random data used to seed the random number 246generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 247Multiple files can be specified separated by a OS-dependent character. 248The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 249all others. 250 251=back 252 253=head1 CONNECTED COMMANDS 254 255If a connection request is established with an SSL client and neither the 256B<-www> nor the B<-WWW> option has been used then normally any data received 257from the client is displayed and any key presses will be sent to the client. 258 259Certain single letter commands are also recognized which perform special 260operations: these are listed below. 261 262=over 4 263 264=item B<q> 265 266end the current SSL connection but still accept new connections. 267 268=item B<Q> 269 270end the current SSL connection and exit. 271 272=item B<r> 273 274renegotiate the SSL session. 275 276=item B<R> 277 278renegotiate the SSL session and request a client certificate. 279 280=item B<P> 281 282send some plain text down the underlying TCP connection: this should 283cause the client to disconnect due to a protocol violation. 284 285=item B<S> 286 287print out some session cache status information. 288 289=back 290 291=head1 NOTES 292 293B<s_server> can be used to debug SSL clients. To accept connections from 294a web browser the command: 295 296 openssl s_server -accept 443 -www 297 298can be used for example. 299 300Most web browsers (in particular Netscape and MSIE) only support RSA cipher 301suites, so they cannot connect to servers which don't use a certificate 302carrying an RSA key or a version of OpenSSL with RSA disabled. 303 304Although specifying an empty list of CAs when requesting a client certificate 305is strictly speaking a protocol violation, some SSL clients interpret this to 306mean any CA is acceptable. This is useful for debugging purposes. 307 308The session parameters can printed out using the B<sess_id> program. 309 310=head1 BUGS 311 312Because this program has a lot of options and also because some of 313the techniques used are rather old, the C source of s_server is rather 314hard to read and not a model of how things should be done. A typical 315SSL server program would be much simpler. 316 317The output of common ciphers is wrong: it just gives the list of ciphers that 318OpenSSL recognizes and the client supports. 319 320There should be a way for the B<s_server> program to print out details of any 321unknown cipher suites a client says it supports. 322 323=head1 SEE ALSO 324 325L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)> 326 327=cut 328