275 lines
7.6 KiB
Plaintext
275 lines
7.6 KiB
Plaintext
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=pod
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=head1 NAME
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s_server - SSL/TLS server program
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=head1 SYNOPSIS
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B<openssl> B<s_server>
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[B<-accept port>]
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[B<-context id>]
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[B<-verify depth>]
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[B<-Verify depth>]
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[B<-cert filename>]
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[B<-key keyfile>]
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[B<-dcert filename>]
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[B<-dkey keyfile>]
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[B<-dhparam filename>]
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[B<-nbio>]
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[B<-nbio_test>]
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[B<-crlf>]
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[B<-debug>]
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[B<-state>]
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[B<-CApath directory>]
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[B<-CAfile filename>]
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[B<-nocert>]
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[B<-cipher cipherlist>]
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[B<-quiet>]
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[B<-no_tmp_rsa>]
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[B<-ssl2>]
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[B<-ssl3>]
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[B<-tls1>]
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[B<-no_ssl2>]
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[B<-no_ssl3>]
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[B<-no_tls1>]
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[B<-no_dhe>]
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[B<-bugs>]
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[B<-hack>]
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[B<-www>]
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[B<-WWW>]
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[B<-rand file(s)>]
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=head1 DESCRIPTION
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The B<s_server> command implements a generic SSL/TLS server which listens
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for connections on a given port using SSL/TLS.
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=head1 OPTIONS
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=over 4
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=item B<-accept port>
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the TCP port to listen on for connections. If not specified 4433 is used.
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=item B<-context id>
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sets the SSL context id. It can be given any string value. If this option
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is not present a default value will be used.
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=item B<-cert certname>
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The certificate to use, most servers cipher suites require the use of a
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certificate and some require a certificate with a certain public key type:
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for example the DSS cipher suites require a certificate containing a DSS
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(DSA) key. If not specified then the filename "server.pem" will be used.
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=item B<-key keyfile>
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The private key to use. If not specified then the certificate file will
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be used.
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=item B<-dcert filename>, B<-dkey keyname>
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specify an additional certificate and private key, these behave in the
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same manner as the B<-cert> and B<-key> options except there is no default
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if they are not specified (no additional certificate and key is used). As
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noted above some cipher suites require a certificate containing a key of
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a certain type. Some cipher suites need a certificate carrying an RSA key
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and some a DSS (DSA) key. By using RSA and DSS certificates and keys
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a server can support clients which only support RSA or DSS cipher suites
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by using an appropriate certificate.
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=item B<-nocert>
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if this option is set then no certificate is used. This restricts the
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cipher suites available to the anonymous ones (currently just anonymous
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DH).
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=item B<-dhparam filename>
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the DH parameter file to use. The ephemeral DH cipher suites generate keys
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using a set of DH parameters. If not specified then an attempt is made to
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load the parameters from the server certificate file. If this fails then
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a static set of parameters hard coded into the s_server program will be used.
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=item B<-no_dhe>
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if this option is set then no DH parameters will be loaded effectively
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disabling the ephemeral DH cipher suites.
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=item B<-no_tmp_rsa>
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certain export cipher suites sometimes use a temporary RSA key, this option
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disables temporary RSA key generation.
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=item B<-verify depth>, B<-Verify depth>
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The verify depth to use. This specifies the maximum length of the
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client certificate chain and makes the server request a certificate from
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the client. With the B<-verify> option a certificate is requested but the
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client does not have to send one, with the B<-Verify> option the client
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must supply a certificate or an error occurs.
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=item B<-CApath directory>
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The directory to use for client certificate verification. This directory
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must be in "hash format", see B<verify> for more information. These are
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also used when building the server certificate chain.
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=item B<-CAfile file>
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A file containing trusted certificates to use during client authentication
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and to use when attempting to build the server certificate chain. The list
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is also used in the list of acceptable client CAs passed to the client when
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a certificate is requested.
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=item B<-state>
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prints out the SSL session states.
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=item B<-debug>
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print extensive debugging information including a hex dump of all traffic.
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=item B<-nbio_test>
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tests non blocking I/O
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=item B<-nbio>
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turns on non blocking I/O
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=item B<-crlf>
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this option translated a line feed from the terminal into CR+LF.
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=item B<-quiet>
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inhibit printing of session and certificate information.
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=item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>
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these options disable the use of certain SSL or TLS protocols. By default
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the initial handshake uses a method which should be compatible with all
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servers and permit them to use SSL v3, SSL v2 or TLS as appropriate.
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=item B<-bugs>
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there are several known bug in SSL and TLS implementations. Adding this
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option enables various workarounds.
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=item B<-hack>
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this option enables a further workaround for some some early Netscape
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SSL code (?).
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=item B<-cipher cipherlist>
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this allows the cipher list used by the server to be modified. When
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the client sends a list of supported ciphers the first client cipher
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also included in the server list is used. Because the client specifies
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the preference order, the order of the server cipherlist irrelevant. See
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the B<ciphers> command for more information.
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=item B<-www>
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sends a status message back to the client when it connects. This includes
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lots of information about the ciphers used and various session parameters.
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The output is in HTML format so this option will normally be used with a
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web browser.
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=item B<-WWW>
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emulates a simple web server. Pages will be resolved relative to the
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current directory, for example if the URL https://myhost/page.html is
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requested the file ./page.html will be loaded.
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=item B<-rand file(s)>
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a file or files containing random data used to seed the random number
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generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>).
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Multiple files can be specified separated by a OS-dependent character.
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The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
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all others.
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=back
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=head1 CONNECTED COMMANDS
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If a connection request is established with an SSL client and neither the
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B<-www> nor the B<-WWW> option has been used then normally any data received
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from the client is displayed and any key presses will be sent to the client.
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Certain single letter commands are also recognized which perform special
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operations: these are listed below.
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=over 4
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=item B<q>
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end the current SSL connection but still accept new connections.
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=item B<Q>
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end the current SSL connection and exit.
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=item B<r>
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renegotiate the SSL session.
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=item B<R>
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renegotiate the SSL session and request a client certificate.
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=item B<P>
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send some plain text down the underlying TCP connection: this should
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cause the client to disconnect due to a protocol violation.
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=item B<S>
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print out some session cache status information.
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=back
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=head1 NOTES
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B<s_server> can be used to debug SSL clients. To accept connections from
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a web browser the command:
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openssl s_server -accept 443 -www
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can be used for example.
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Most web browsers (in particular Netscape and MSIE) only support RSA cipher
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suites, so they cannot connect to servers which don't use a certificate
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carrying an RSA key or a version of OpenSSL with RSA disabled.
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Although specifying an empty list of CAs when requesting a client certificate
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is strictly speaking a protocol violation, some SSL clients interpret this to
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mean any CA is acceptable. This is useful for debugging purposes.
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The session parameters can printed out using the B<sess_id> program.
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=head1 BUGS
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Because this program has a lot of options and also because some of
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the techniques used are rather old, the C source of s_server is rather
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hard to read and not a model of how things should be done. A typical
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SSL server program would be much simpler.
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The output of common ciphers is wrong: it just gives the list of ciphers that
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OpenSSL recognizes and the client supports.
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There should be a way for the B<s_server> program to print out details of any
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unknown cipher suites a client says it supports.
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=head1 SEE ALSO
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L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>
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=cut
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