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S_SERVER(1)                  OpenSSL                  S_SERVER(1)


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 filename] [-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_resumption_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 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.

     -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

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         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 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.

     -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 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.

     -no_dhe
         if this option is set then no DH parameters will be
         loaded effectively 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.

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     -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 information. These are also used
         when building the server certificate chain.

     -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.

     -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

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S_SERVER(1)                  OpenSSL                  S_SERVER(1)

         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.


-no_tls1, -no_tls1_1, -no_tls1_2

     -ssl2, -ssl3, -tls1, -tls1_1, -tls1_2, -no_ssl2, -no_ssl3,
         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
         authentication (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.

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S_SERVER(1)                  OpenSSL                  S_SERVER(1)

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

     -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 correct 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 number generator, or an EGD socket (see
         RAND_egd(3)).  Multiple files can be specified separated
         by a OS-dependent character.  The separator is ; for

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S_SERVER(1)                  OpenSSL                  S_SERVER(1)

         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 Negotiation 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 special operations: these are listed below.

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

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     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 certificate is strictly speaking a protocol
     violation, some SSL clients interpret this to mean any CA is
     acceptable. This is useful for debugging 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.

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See also openssl-s_server(1)

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