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 informa-
   tion. These are also used when building the client certificate
   chain.

    -CAfile file
   A file containing trusted certificates to use during server authen-
   tication 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 connec-
   tion succeeds. This option is useful because the cipher in use may
   be renegotiated or the connection may fail because a client cer-
   tificate 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 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 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 oth-
   ers 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 num-
   ber 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 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 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 authentication after
    a specific URL is requested. To obtain the list in this case it is nec-
    essary 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 informa-
    tion whenever a session is renegotiated.

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