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NAME

       openssl-s_server, s_server - SSL/TLS server program


SYNOPSIS

       openssl s_server [-accept port] [-context id] [-verify depth] [-Verify
       depth] [-crl_check] [-crl_check_all] [-cert filename] [-certform
       DER|PEM] [-key keyfile] [-keyform DER|PEM] [-pass arg] [-dcert file-
       name] [-dcertform DER|PEM] [-dkey keyfile] [-dkeyform DER|PEM] [-dpass
       arg] [-dhparam filename] [-nbio] [-nbio_test] [-crlf] [-debug] [-msg]
       [-state] [-CApath directory] [-CAfile filename] [-no_alt_chains]
       [-nocert] [-client_sigalgs sigalglist] [-named_curve curve] [-cipher
       cipherlist] [-serverpref] [-quiet] [-no_tmp_rsa] [-ssl2] [-ssl3]
       [-tls1] [-no_ssl2] [-no_ssl3] [-no_tls1] [-no_dhe] [-no_ecdhe] [-bugs]
       [-hack] [-www] [-WWW] [-HTTP] [-engine id] [-tlsextdebug] [-no_ticket]
       [-id_prefix arg] [-rand file(s)] [-serverinfo file] [-no_resump-
       tion_on_reneg] [-status] [-status_verbose] [-status_timeout nsec]
       [-status_url url] [-alpn protocols] [-nextprotoneg protocols]


DESCRIPTION

       The s_server command implements a generic SSL/TLS server which listens
       for connections on a given port using SSL/TLS.


OPTIONS

       -accept port
           the TCP port to listen on for connections. If not specified 4433 is
           used.

       -context id
           sets the SSL context id. It can be given any string value. If this
           option is not present a default value will be used.

       -cert certname
           The certificate to use, most servers cipher suites require the use
           of a certificate and some require a certificate with a certain pub-
           lic key type: for example the DSS cipher suites require a certifi-
           cate containing a DSS (DSA) key. If not specified then the filename
           "server.pem" will be used.

       -certform format
           The certificate format to use: DER or PEM. PEM is the default.

       -key keyfile
           The private key to use. If not specified then the certificate file
           will be used.

       -keyform format
           The private format to use: DER or PEM. PEM is the default.

       -pass arg
           the private key password source. For more information about the
           format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

       -dcert filename, -dkey keyname
           specify an additional certificate and private key, these behave in
           the same manner as the -cert and -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 certifi-
           cate 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.

       -dcertform format, -dkeyform format, -dpass arg
           additional certificate and private key format and passphrase
           respectively.

       -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).

       -dhparam filename
           the DH parameter file to use. The ephemeral DH cipher suites gener-
           ate 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.

       -no_dhe
           if this option is set then no DH parameters will be loaded effec-
           tively disabling the ephemeral DH cipher suites.

       -no_ecdhe
           if this option is set then no ECDH parameters will be selected,
           effectively disabling the ephemeral ECDH cipher suites.

       -no_tmp_rsa
           certain export cipher suites sometimes use a temporary RSA key,
           this option disables temporary RSA key generation.

       -verify depth, -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 -verify option a certificate is requested
           but the client does not have to send one, with the -Verify option
           the client must supply a certificate or an error occurs.

           If the ciphersuite cannot request a client certificate (for example
           an anonymous ciphersuite or PSK) this option has no effect.

       -crl_check, -crl_check_all
           Check the peer certificate has not been revoked by its CA.  The
           CRL(s) are appended to the certificate file. With the
           -crl_check_all option all CRLs of all CAs in the chain are checked.

       -CApath directory
           The directory to use for client certificate verification. This
           directory must be in "hash format", see verify for more informa-
           tion. These are also used when building the server certificate
           chain.

       -CAfile file
           A file containing trusted certificates to use during client authen-
           tication 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.

       -no_alt_chains
           See the verify manual page for details.

       -state
           prints out the SSL session states.

       -debug
           print extensive debugging information including a hex dump of all
           traffic.

       -msg
           show all protocol messages with hex dump.

       -nbio_test
           tests non blocking I/O

       -nbio
           turns on non blocking I/O

       -crlf
           this option translated a line feed from the terminal into CR+LF.

       -quiet
           inhibit printing of session and certificate information.

       -psk_hint hint
           Use the PSK identity hint hint when using a PSK cipher suite.

       -psk key
           Use the PSK key key when using a PSK cipher suite. The key is given
           as a hexadecimal number without leading 0x, for example -psk
           1a2b3c4d.  This option must be provided in order to use a PSK
           cipher.

       -ssl2, -ssl3, -tls1, -tls1_1, -tls1_2, -no_ssl2, -no_ssl3, -no_tls1,
       -no_tls1_1, -no_tls1_2
           These options require or disable the use of the specified SSL or
           TLS protocols.  By default the initial handshake uses a version-
           flexible method which will negotiate the highest mutually supported
           protocol version.

       -bugs
           there are several known bug in SSL and TLS implementations. Adding
           this option enables various workarounds.

       -hack
           this option enables a further workaround for some some early
           Netscape SSL code (?).

       -client_sigalgs sigalglist
           Signature algorithms to support for client certificate authentica-
           tion (colon-separated list)

       -named_curve curve
           Specifies the elliptic curve to use. NOTE: this is single curve,
           not a list.  For a list of all possible curves, use:

               $ openssl ecparam -list_curves

       -cipher cipherlist
           this allows the cipher list used by the server to be modified.
           When the client sends a list of supported ciphers the first client
           cipher also included in the server list is used. Because the client
           specifies the preference order, the order of the server cipherlist
           irrelevant. See the ciphers command for more information.

       -serverpref
           use the server's cipher preferences, rather than the client's pref-
           erences.

       -tlsextdebug
           print out a hex dump of any TLS extensions received from the
           server.

       -no_ticket
           disable RFC4507bis session ticket support.

       -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.

       -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.

       -HTTP
           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. The files loaded are assumed to contain a complete and cor-
           rect HTTP response (lines that are part of the HTTP response line
           and headers must end with CRLF).

       -engine id
           specifying an engine (by its unique id string) will cause s_server
           to attempt to obtain a functional reference to the specified
           engine, thus initialising it if needed. The engine will then be set
           as the default for all available algorithms.

       -id_prefix arg
           generate SSL/TLS session IDs prefixed by arg. This is mostly useful
           for testing any SSL/TLS code (eg. proxies) that wish to deal with
           multiple servers, when each of which might be generating a unique
           range of session IDs (eg. with a certain prefix).

       -rand file(s)
           a file or files containing random data used to seed the random num-
           ber generator, or an EGD socket (see RAND_egd(3)).  Multiple files
           can be specified separated by a OS-dependent character.  The sepa-
           rator is ; for MS-Windows, , for OpenVMS, and : for all others.

       -serverinfo file
           a file containing one or more blocks of PEM data.  Each PEM block
           must encode a TLS ServerHello extension (2 bytes type, 2 bytes
           length, followed by "length" bytes of extension data).  If the
           client sends an empty TLS ClientHello extension matching the type,
           the corresponding ServerHello extension will be returned.

       -no_resumption_on_reneg
           set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag.

       -status
           enables certificate status request support (aka OCSP stapling).

       -status_verbose
           enables certificate status request support (aka OCSP stapling) and
           gives a verbose printout of the OCSP response.

       -status_timeout nsec
           sets the timeout for OCSP response to nsec seconds.

       -status_url url
           sets a fallback responder URL to use if no responder URL is present
           in the server certificate. Without this option an error is returned
           if the server certificate does not contain a responder address.

       -alpn protocols, -nextprotoneg protocols
           these flags enable the Enable the Application-Layer Protocol Nego-
           tiation or Next Protocol Negotiation extension, respectively. ALPN
           is the IETF standard and replaces NPN.  The protocols list is a
           comma-separated list of supported protocol names.  The list should
           contain most wanted protocols first.  Protocol names are printable
           ASCII strings, for example "http/1.1" or "spdy/3".


CONNECTED COMMANDS

       If a connection request is established with an SSL client and neither
       the -www nor the -WWW option has been used then normally any data
       received from the client is displayed and any key presses will be sent
       to the client.

       Certain single letter commands are also recognized which perform spe-
       cial operations: these are listed below.

       q   end the current SSL connection but still accept new connections.

       Q   end the current SSL connection and exit.

       r   renegotiate the SSL session.

       R   renegotiate the SSL session and request a client certificate.

       P   send some plain text down the underlying TCP connection: this
           should cause the client to disconnect due to a protocol violation.

       S   print out some session cache status information.


NOTES

       s_server 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.

       Although specifying an empty list of CAs when requesting a client cer-
       tificate is strictly speaking a protocol violation, some SSL clients
       interpret this to mean any CA is acceptable. This is useful for debug-
       ging purposes.

       The session parameters can printed out using the sess_id program.


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 recognizes and the client supports.

       There should be a way for the s_server program to print out details of
       any unknown cipher suites a client says it supports.


SEE ALSO

       sess_id(1), s_client(1), ciphers(1)


HISTORY

       The -no_alt_chains options was first added to OpenSSL 1.0.2b.

1.0.2t                            2019-09-10                       S_SERVER(1)
See also s_server(1)

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