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s_client(1) - s_client - SSL/TLS client program - man 1 s_client

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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(1,n)(s)]

       The s_client command implements a generic SSL/TLS client which connects
       to a remote host(1,5) using SSL/TLS. It is a very useful diagnostic tool for
       SSL servers.

       -connect host:port
           This specifies the host(1,5) and optional port to connect to. If not
           specified then an attempt is made to connect to the local host(1,5) on
           port 4433.

       -cert certname
           The certificate to use, if(3,n) 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(1,n)
           will be used.

       -verify depth
           The verify(1,8) depth to use. This specifies the maximum length of the
           server certificate chain and turns on server certificate verifica-
           tion.  Currently the verify(1,8) 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(1,8)

       -CApath directory
           The directory to use for server certificate verification. This
           directory must be in(1,8) "hash format", see verify(1,8) for more informa-
           tion. These are also used when building the client certificate

       -CAfile file(1,n)
           A file(1,n) containing trusted certificates to use during server authen-
           tication and to use when attempting to build the client certificate

           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(2,n,1 builtins) and write(1,2) 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(3,n) the connection fails. Nor-
           mally information will only be printed out once if(3,n) the connection
           succeeds. This option is useful because the cipher in(1,8) use may be
           renegotiated or the connection may fail because a client certifi-
           cate is required or is requested only after an attempt is made to
           access(2,5) a certain URL. Note: the output produced by this option is
           not always accurate because a connection might never have been

           prints out the SSL session states.

           print extensive debugging information including a hex dump of all

           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 servers.

           inhibit shutting down the connection when end of file(1,n) is reached in(1,8)
           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 compat-
           ible 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(1,8) use
           which cannot handle this technique and will fail to connect. Some
           servers only work if(3,n) TLS is turned off with the -no_tls option oth-
           ers will only support SSL v2 and may need the -ssl2 option.

           there are several known bug in(1,8) 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(1,8) the list sent by the client. See
           the ciphers command for more information.

       -starttls protocol
           send(2,n) the protocol-specific message(s) to switch(1,n) to TLS for communi-
           cation.  protocol is a keyword for the intended protocol.  Cur-
           rently, the only supported keywords are "smtp" and "pop3".

       -engine id
           specifying an engine (by it's unique id string(3,n)) will cause s_client
           to attempt to obtain a functional reference to the specified
           engine, thus initialising it if(3,n) needed. The engine will then be set(7,n,1 builtins)
           as the default for all available algorithms.

       -rand file(1,n)(s)
           a file(1,n) or files containing random(3,4,6) data used to seed the random(3,4,6) num-
           ber generator, or an EGD socket(2,7,n) (see RAND_egd(3)).  Multiple files
           can be specified separated by a OS-dependent character.  The sepa-
           rator is ; for MS-Windows, , for OpenVMS, and : for all others.

       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(3,n) the line
       begins with an R, and if(3,n) the line begins with a Q or if(3,n) end of file(1,n) 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 suc-
       ceeds 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(3,n) 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(1,8) 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(1,8) 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(1,8) this case it is nec-
       essary to use the -prexit option and send(2,n) an HTTP request for an appro-
       priate 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.

       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(2,n,1 builtins) 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(3,n,1 builtins) if(3,n) the server verification fails.

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

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

0.9.7d                            2004-01-04                       S_CLIENT(1)

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