S_SERVER(1)			    OpenSSL			   S_SERVER(1)



NAME
       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] [-trusted_first]
       [-no_alt_chains] [-nocert] [-cipher cipherlist] [-serverpref] [-krb5svc
       service] [-keytab filename] [-quiet] [-no_tmp_rsa] [-ssl3] [-tls1]
       [-tls1_1] [-tls1_2] [-no_ssl3] [-no_tls1] [-no_dhe] [-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
	   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_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
	   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.

       -trusted_first
	   Use certificates in CA file or CA directory before other
	   certificates when building the trust chain to verify client
	   certificates.  This is mainly useful in environments with Bridge CA
	   or Cross-Certified CAs.

       -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.

       -ssl3, -tls1, -tls1_1, -tls1_2, -dtls1, -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 (?).

       -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.

       -krb5svc service
	   the Kerberos service name to use (default "host"). This means
	   s_server will expect a ticket for the principal
	   service/hostname@REALM, and will need keys for that principal in
	   its keytab.

       -keytab filename
	   the Kerberos "keytab" (key table) file, containing keys for the
	   s_server service principal (Kerberos identity; see -krb5svc).

       -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 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.

       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.

       Most web browsers (in particular Netscape and MSIE) only support RSA
       cipher suites, so they cannot connect to servers which don't use a
       certificate carrying an RSA key or a version of OpenSSL with RSA
       disabled.

       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.



1.0.2k				  2023-11-15			   S_SERVER(1)