s_server(1)



S_SERVER(1SSL)                      OpenSSL                     S_SERVER(1SSL)

NAME
       openssl-s_server, s_server - SSL/TLS server program

SYNOPSIS
       openssl s_server [-help] [-port port] [-accept val] [-naccept count]
       [-unix val] [-unlink] [-4] [-6] [-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-CAfile]
       [-no-CApath] [-attime timestamp] [-check_ss_sig] [-explicit_policy]
       [-extended_crl] [-ignore_critical] [-inhibit_any] [-inhibit_map]
       [-no_check_time] [-partial_chain] [-policy arg] [-policy_check]
       [-policy_print] [-purpose purpose] [-suiteB_128] [-suiteB_128_only]
       [-suiteB_192] [-trusted_first] [-no_alt_chains] [-use_deltas]
       [-auth_level num] [-verify_depth num] [-verify_return_error]
       [-verify_email email] [-verify_hostname hostname] [-verify_ip ip]
       [-verify_name name] [-x509_strict] [-nocert] [-client_sigalgs
       sigalglist] [-named_curve curve] [-cipher cipherlist] [-serverpref]
       [-quiet] [-ssl3] [-tls1] [-tls1_1] [-tls1_2] [-dtls] [-dtls1]
       [-dtls1_2] [-listen] [-async] [-split_send_frag] [-max_pipelines]
       [-read_buf] [-no_ssl3] [-no_tls1] [-no_tls1_1] [-no_tls1_2] [-no_dhe]
       [-bugs] [-comp] [-no_comp] [-brief] [-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
       In addition to the options below the s_server utility also supports the
       common and server only options documented in the in the "Supported
       Command Line Commands" section of the SSL_CONF_cmd(3) manual page.

       -help
           Print out a usage message.

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

       -accept val
           The optional TCP host and port to listen on for connections. If not
           specified, *:4433 is used.

       -naccept count
           The server will exit after receiving number connections, default
           unlimited.

       -unix val
           Unix domain socket to accept on.

       -unlink
           For -unix, unlink existing socket first.

       -4  Use IPv4 only.

       -6  Use IPv6 only.

       -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
           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.

       -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-CAfile
           Do not load the trusted CA certificates from the default file
           location

       -no-CApath
           Do not load the trusted CA certificates from the default directory
           location

       -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.

       -attime, -check_ss_sig, -crl_check, -crl_check_all, -explicit_policy,
       -extended_crl, -ignore_critical, -inhibit_any, -inhibit_map,
       -no_alt_chains, -no_check_time, -partial_chain, -policy, -policy_check,
       -policy_print, -purpose, -suiteB_128, -suiteB_128_only, -suiteB_192,
       -trusted_first, -use_deltas, -auth_level, -verify_depth, -verify_email,
       -verify_hostname, -verify_ip, -verify_name, -x509_strict
           Set different peer certificate verification options.  See the
           verify(1) manual page for details.

       -verify_return_error
           Verification errors normally just print a message but allow the
           connection to continue, for debugging purposes.  If this option is
           used, then verification errors close the connection.

       -state
           Prints the SSL session states.

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

       -msg
           Show all protocol messages with hex dump.

       -trace
           Show verbose trace output of protocol messages. OpenSSL needs to be
           compiled with enable-ssl-trace for this option to work.

       -msgfile
           File to send output of -msg or -trace to, default standard output.

       -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 s_server will negotiate the highest
           mutually supported protocol version.  When a specific TLS version
           is required, only that version will be accepted from the client.

       -dtls, -dtls1, -dtls1_2
           These options make s_server use DTLS protocols instead of TLS.
           With -dtls, s_server will negotiate any supported DTLS protocol
           version, whilst -dtls1 and -dtls1_2 will only support DTLSv1.0 and
           DTLSv1.2 respectively.

       -listen
           This option can only be used in conjunction with one of the DTLS
           options above.  With this option s_server will listen on a UDP port
           for incoming connections.  Any ClientHellos that arrive will be
           checked to see if they have a cookie in them or not.  Any without a
           cookie will be responded to with a HelloVerifyRequest.  If a
           ClientHello with a cookie is received then s_server will connect to
           that peer and complete the handshake.

       -async
           Switch on asynchronous mode. Cryptographic operations will be
           performed asynchronously. This will only have an effect if an
           asynchronous capable engine is also used via the -engine option.
           For test purposes the dummy async engine (dasync) can be used (if
           available).

       -split_send_frag int
           The size used to split data for encrypt pipelines. If more data is
           written in one go than this value then it will be split into
           multiple pipelines, up to the maximum number of pipelines defined
           by max_pipelines. This only has an effect if a suitable ciphersuite
           has been negotiated, an engine that supports pipelining has been
           loaded, and max_pipelines is greater than 1. See
           SSL_CTX_set_split_send_fragment(3) for further information.

       -max_pipelines int
           The maximum number of encrypt/decrypt pipelines to be used. This
           will only have an effect if an engine has been loaded that supports
           pipelining (e.g. the dasync engine) and a suitable ciphersuite has
           been negotiated. The default value is 1.  See
           SSL_CTX_set_max_pipelines(3) for further information.

       -read_buf int
           The default read buffer size to be used for connections. This will
           only have an effect if the buffer size is larger than the size that
           would otherwise be used and pipelining is in use (see
           SSL_CTX_set_default_read_buffer_len(3) for further information).

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

       -comp
           Enable negotiation of TLS compression.  This option was introduced
           in OpenSSL 1.1.0.  TLS compression is not recommended and is off by
           default as of OpenSSL 1.1.0.

       -no_comp
           Disable negotiation of TLS compression.  TLS compression is not
           recommended and is off by default as of OpenSSL 1.1.0.

       -brief
           Provide a brief summary of connection parameters instead of the
           normal verbose output.

       -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.

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

       -tlsextdebug
           Print 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 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).

       -rev
           Simple test server which just reverses the text received from the
           client and sends it back to the server. Also sets -brief.

       -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 an OS-dependent character.  The
           separator 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 the SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION option.

       -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.

       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
       SSL_CONF_cmd(3), sess_id(1), s_client(1), ciphers(1)

HISTORY
       The -no_alt_chains options was first added to OpenSSL 1.1.0.

COPYRIGHT
       Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

1.1.0h                            2018-05-23                    S_SERVER(1SSL)

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