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S_CLIENT(1)				     OpenSSL				      S_CLIENT(1)

       s_client - SSL/TLS client program

       openssl s_client [-connect host:port] [-verify depth] [-cert filename] [-key filename]
       [-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] [-rand file(s)]

       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.

       -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

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

       -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.

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

	   pauses 1 second between each read and write call.

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

	   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.

	   prints out the SSL session states.

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

	   show all protocol messages with hex dump.

	   tests non-blocking I/O

	   turns on non-blocking I/O

	   this option translated a line feed from the terminal into CR+LF as required by some

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

	   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.

	   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" and "pop3".

       -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

       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 renegoti-
       ated 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.

       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 includ-
       ing 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.

       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 ses-
       sion is renegotiated.

       sess_id(1), s_server(1), ciphers(1)

0.9.7d					    2004-05-17				      S_CLIENT(1)
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