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s_server - SSL/TLS server program
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B<openssl> B<s_server>
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[B<-certform DER|PEM>]
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[B<-dcertform DER|PEM>]
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[B<-dkeyform DER|PEM>]
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[B<-dhparam filename>]
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[B<-CApath directory>]
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[B<-cipher cipherlist>]
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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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the TCP port to listen on for connections. If not specified 4433 is used.
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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<-certform format>
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The certificate format to use: DER or PEM. PEM is the default.
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The private key to use. If not specified then the certificate file will
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=item B<-keyform format>
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The private format to use: DER or PEM. PEM is the default.
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the private key password source. For more information about the format of B<arg>
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see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
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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<-dcertform format>, B<-dkeyform format>, B<-dpass arg>
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addtional certificate and private key format and passphrase respectively.
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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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=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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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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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<-crl_check>, B<-crl_check_all>
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Check the peer certificate has not been revoked by its CA.
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The CRL(s) are appended to the certificate file. With the B<-crl_check_all>
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option all CRLs of all CAs in the chain are checked.
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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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prints out the SSL session states.
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print extensive debugging information including a hex dump of all traffic.
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show all protocol messages with hex dump.
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tests non blocking I/O
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turns on non blocking I/O
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this option translated a line feed from the terminal into CR+LF.
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inhibit printing of session and certificate information.
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=item B<-psk_hint hint>
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Use the PSK identity hint B<hint> when using a PSK cipher suite.
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Use the PSK key B<key> when using a PSK cipher suite. The key is
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given as a hexadecimal number without leading 0x, for example -psk
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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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there are several known bug in SSL and TLS implementations. Adding this
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option enables various workarounds.
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this option enables a further workaround for some some early Netscape
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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<-tlsextdebug>
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print out a hex dump of any TLS extensions received from the server.
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disable RFC4507bis session ticket support.
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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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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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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. The files loaded are
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assumed to contain a complete and correct HTTP response (lines that
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are part of the HTTP response line and headers must end with CRLF).
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specifying an engine (by its unique B<id> string) will cause B<s_server>
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to attempt to obtain a functional reference to the specified engine,
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thus initialising it if needed. The engine will then be set as the default
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for all available algorithms.
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=item B<-id_prefix arg>
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generate SSL/TLS session IDs prefixed by B<arg>. This is mostly useful
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for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple
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servers, when each of which might be generating a unique range of session
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IDs (eg. with a certain prefix).
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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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=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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end the current SSL connection but still accept new connections.
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end the current SSL connection and exit.
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renegotiate the SSL session.
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renegotiate the SSL session and request a client certificate.
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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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print out some session cache status information.
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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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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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L<sess_id(1)|sess_id(1)>, L<s_client(1)|s_client(1)>, L<ciphers(1)|ciphers(1)>
added
removed
.pc/pod_s_server.misspell.patch/doc/apps/s_server.pod
