=pod =head1 NAME s_server - SSL/TLS server program =head1 SYNOPSIS B B [B<-accept port>] [B<-context id>] [B<-verify depth>] [B<-Verify depth>] [B<-cert filename>] [B<-key keyfile>] [B<-dcert filename>] [B<-dkey keyfile>] [B<-dhparam filename>] [B<-nbio>] [B<-nbio_test>] [B<-crlf>] [B<-debug>] [B<-state>] [B<-CApath directory>] [B<-CAfile filename>] [B<-nocert>] [B<-cipher cipherlist>] [B<-quiet>] [B<-no_tmp_rsa>] [B<-ssl2>] [B<-ssl3>] [B<-tls1>] [B<-no_ssl2>] [B<-no_ssl3>] [B<-no_tls1>] [B<-no_dhe>] [B<-bugs>] [B<-www>] [B<-WWW>] =head1 DESCRIPTION The B command implements a generic SSL/TLS server which listens for connections on a given port using SSL/TLS. =head1 OPTIONS =over 4 =item B<-accept port> the TCP port to listen on for connections. If not specified 4433 is used. =item B<-context id> sets the SSL context id. If a client certificate is being requested then this option must be set. It can be given any string value. =item B<-cert certname> The certificate to use, most servers cipher suites require the use of a certificate and some require a certificate with a certain public key type: for example the DSS cipher suites require a certificate containing a DSS (DSA) key. If not specified then the filename "server.pem" will be used. =item B<-key keyfile> The private key to use. If not specified then the certificate file will be used. =item B<-dcert filename>, B<-dkey keyname> specify an additional certificate and private key, these behave in the same manner as the B<-cert> and B<-key> options except there is no default if they are not specified (no additional certificate and key is used). As noted above some cipher suites require a certificate containing a key of a certain type. Some cipher suites need a certificate carrying an RSA key and some a DSS (DSA) key. By using RSA and DSS certificates and keys a server can support clients which only support RSA or DSS cipher suites by using an appropriate certificate. =item B<-nocert> if this option is set then no certificate is used. This restricts the cipher suites available to the anonymous ones (currently just anonymous DH). =item B<-dhparam filename> the DH parameter file to use. The ephemeral DH cipher suites generate keys using a set of DH parameters. If not specified then an attempt is made to load the parameters from the server certificate file. If this fails then a static set of parameters hard coded into the s_server program will be used. =item B<-nodhe> if this option is set then no DH parameters will be loaded effectively disabling the ephemeral DH cipher suites. =item B<-no_tmp_rsa> certain export cipher suites sometimes use a temporary RSA key, this option disables temporary RSA key generation. =item B<-verify depth>, B<-Verify depth> The verify depth to use. This specifies the maximum length of the client certificate chain and makes the server request a certificate from the client. With the B<-verify> option a certificate is requested but the client does not have to send one, with the B<-Verify> option the client must supply a certificate or an error occurs. =item B<-CApath directory> The directory to use for client certificate verification. This directory must be in "hash format", see B for more information. These are also used when building the server certificate chain. =item B<-CAfile file> A file containing trusted certificates to use during client authentication and to use when attempting to build the server certificate chain. The list is also used in the list of acceptable client CAs passed to the client when a certificate is requested. =item B<-state> prints out the SSL session states. =item B<-debug> print extensive debugging information including a hex dump of all traffic. =item B<-nbio_test> tests non blocking I/O =item B<-nbio> turns on non blocking I/O =item B<-crlf> this option translated a line feed from the terminal into CR+LF. =item B<-quiet> inhibit printing of session and certificate information. =item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1> these options disable the use of certain SSL or TLS protocols. By default the initial handshake uses a method which should be compatible with all servers and permit them to use SSL v3, SSL v2 or TLS as appropriate. =item B<-bugs> there are several known bug in SSL and TLS implementations. Adding this option enables various workarounds. =item B<-cipher cipherlist> this allows the cipher list sent by the client to be modified. See the B command for more information. =item B<-www> sends a status message back to the client when it connects. This includes lots of information about the ciphers used and various session parameters. The output is in HTML format so this option will normally be used with a web browser. =item B<-WWW> emulates a simple web server. Pages will be resolved relative to the current directory, for example if the URL https://myhost/page.html is requested the file ./page.html will be loaded. =back =head1 CONNECTED COMMANDS If a connection request is established with an SSL client and neither the B<-www> nor the B<-WWW> option has been used then any data received from the server is displayed and any key presses will be sent to the server. If the line begins with an B then the session will be renegotiated. If the line begins with a B the connection will be closed down. =head1 NOTES B can be used to debug SSL clients. To accept connections from a web browser the command: openssl s_server -accept 443 -www can be used for example. Most web browsers (in particular Netscape and MSIE) only support RSA cipher suites, so they cannot connect to servers which don't use a certificate carrying an RSA key or a version of OpenSSL with RSA disabled. Although specifying an empty list of CAs when requesting a client certificate is strictly speaking a protocol violation, some SSL clients assume any CA is acceptable. This is useful for debugging purposes. The session parameters can printed out using the B program. =head1 BUGS Because this program has a lot of options and also because some of the techniques used are rather old, the C source of s_server is rather hard to read and not a model of how things should be done. A typical SSL server program would be much simpler. The output of common ciphers is wrong: it just gives the list of ciphers that OpenSSL recognises and the client supports. There should be a way for the B program to print out details of any unknown cipher suites a client says it supports. =head1 SEE ALSO sess_id(1), s_client(1), ciphers(1) =cut