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S_CLIENT(1)			    OpenSSL			   S_CLIENT(1)

NAME
       s_client - SSL/TLS client program

SYNOPSIS
       openssl s_client [-connect host:port] [-verify depth] [-cert filename]
       [-certform DER|PEM] [-key filename] [-keyform DER|PEM] [-pass arg]
       [-CApath directory] [-CAfile filename] [-reconnect] [-pause]
       [-showcerts] [-debug] [-msg] [-nbio_test] [-state] [-nbio] [-crlf]
       [-ign_eof] [-quiet] [-ssl2] [-ssl3] [-tls1] [-no_ssl2] [-no_ssl3]
       [-no_tls1] [-bugs] [-cipher cipherlist] [-starttls protocol] [-engine
       id] [-tlsextdebug] [-no_ticket] [-sess_out filename] [-sess_in
       filename] [-rand file(s)]

DESCRIPTION
       The s_client command implements a generic SSL/TLS client which connects
       to a remote host using SSL/TLS. It is a very useful diagnostic tool for
       SSL servers.

OPTIONS
       -connect host:port
	   This specifies the host and optional port to connect to. If not
	   specified then an attempt is made to connect to the local host on
	   port 4433.

       -cert certname
	   The certificate to use, if one is requested by the server. The
	   default is not to use a certificate.

       -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).

       -verify depth
	   The verify depth to use. This specifies the maximum length of the
	   server certificate chain and turns on server certificate
	   verification.  Currently the verify operation continues after
	   errors so all the problems with a certificate chain can be seen. As
	   a side effect the connection will never fail due to a server
	   certificate verify failure.

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

       -CAfile file
	   A file containing trusted certificates to use during server
	   authentication and to use when attempting to build the client
	   certificate chain.

       -reconnect
	   reconnects to the same server 5 times using the same session ID,
	   this can be used as a test that session caching is working.

       -pause
	   pauses 1 second between each read and write call.

       -showcerts
	   display the whole server certificate chain: normally only the
	   server certificate itself is displayed.

       -prexit
	   print session information when the program exits. This will always
	   attempt to print out information even if the connection fails.
	   Normally information will only be printed out once if the
	   connection succeeds. This option is useful because the cipher in
	   use may be renegotiated or the connection may fail because a client
	   certificate is required or is requested only after an attempt is
	   made to access a certain URL. Note: the output produced by this
	   option is not always accurate because a connection might never have
	   been established.

       -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 as
	   required by some servers.

       -ign_eof
	   inhibit shutting down the connection when end of file is reached in
	   the input.

       -quiet
	   inhibit printing of session and certificate information.  This
	   implicitly turns on -ign_eof as well.

       -ssl2, -ssl3, -tls1, -no_ssl2, -no_ssl3, -no_tls1
	   these options disable the use of certain SSL or TLS protocols. By
	   default the initial handshake uses a method which should be
	   compatible with all servers and permit them to use SSL v3, SSL v2
	   or TLS as appropriate.

	   Unfortunately there are a lot of ancient and broken servers in use
	   which cannot handle this technique and will fail to connect. Some
	   servers only work if TLS is turned off with the -no_tls option
	   others will only support SSL v2 and may need the -ssl2 option.

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

       -cipher cipherlist
	   this allows the cipher list sent by the client to be modified.
	   Although the server determines which cipher suite is used it should
	   take the first supported cipher in the list sent by the client. See
	   the ciphers command for more information.

       -starttls protocol
	   send the protocol-specific message(s) to switch to TLS for
	   communication.  protocol is a keyword for the intended protocol.
	   Currently, the only supported keywords are "smtp", "pop3", "imap",
	   and "ftp".

       -tlsextdebug
	   print out a hex dump of any TLS extensions received from the
	   server. Note: this option is only available if extension support is
	   explicitly enabled at compile time

       -no_ticket
	   disable RFC4507bis session ticket support. Note: this option is
	   only available if extension support is explicitly enabled at
	   compile time

       -sess_out filename
	   output SSL session to filename

       -sess_in sess.pem
	   load SSL session from filename. The client will attempt to resume a
	   connection from this session.

       -engine id
	   specifying an engine (by it's unique id string) will cause s_client
	   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.

       -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.

CONNECTED COMMANDS
       If a connection is established with an SSL server then any data
       received from the server is displayed and any key presses will be sent
       to the server. When used interactively (which means neither -quiet nor
       -ign_eof have been given), the session will be renegotiated if the line
       begins with an R, and if the line begins with a Q or if end of file is
       reached, the connection will be closed down.

NOTES
       s_client can be used to debug SSL servers. To connect to an SSL HTTP
       server the command:

	openssl s_client -connect servername:443

       would typically be used (https uses port 443). If the connection
       succeeds then an HTTP command can be given such as "GET /" to retrieve
       a web page.

       If the handshake fails then there are several possible causes, if it is
       nothing obvious like no client certificate then the -bugs, -ssl2,
       -ssl3, -tls1, -no_ssl2, -no_ssl3, -no_tls1 options can be tried in case
       it is a buggy server. In particular you should play with these options
       before submitting a bug report to an OpenSSL mailing list.

       A frequent problem when attempting to get client certificates working
       is that a web client complains it has no certificates or gives an empty
       list to choose from. This is normally because the server is not sending
       the clients certificate authority in its "acceptable CA list" when it
       requests a certificate. By using s_client the CA list can be viewed and
       checked. However some servers only request client authentication after
       a specific URL is requested. To obtain the list in this case it is
       necessary to use the -prexit option and send an HTTP request for an
       appropriate page.

       If a certificate is specified on the command line using the -cert
       option it will not be used unless the server specifically requests a
       client certificate. Therefor merely including a client certificate on
       the command line is no guarantee that the certificate works.

       If there are problems verifying a server certificate then the
       -showcerts option can be used to show the whole chain.

       Since the SSLv23 client hello cannot include compression methods or
       extensions these will only be supported if its use is disabled, for
       example by using the -no_sslv2 option.

       TLS extensions are only supported in OpenSSL 0.9.8 if they are
       explictly enabled at compile time using for example the enable-tlsext
       switch.

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_client is rather hard
       to read and not a model of how things should be done. A typical SSL
       client program would be much simpler.

       The -verify option should really exit if the server verification fails.

       The -prexit option is a bit of a hack. We should really report
       information whenever a session is renegotiated.

SEE ALSO
       sess_id(1), s_server(1), ciphers(1)

0.9.8k				  2007-08-23			   S_CLIENT(1)
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