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] [-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] [-engine id] [-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.

       -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 verifica-
	   tion.  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. Nor-
	   mally 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 estab-
	   lished.

       -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 compati-
	   ble 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.

       -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 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 authenti-
       cation after a specific URL is requested. To obtain the list in this case it is necessary to use the -prexit command 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.

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)

0.9.7a								    2001-11-09							       S_CLIENT(1)