s_client(1)

     S_CLIENT(1)            0.9.6h (2001-02-15)            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] [-nbio_test] [-state] [-nbio] [-crlf] [-ign_eof]
          [-quiet] [-ssl2] [-ssl3] [-tls1] [-no_ssl2] [-no_ssl3]
          [-no_tls1] [-bugs] [-cipher cipherlist] [-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 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

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              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.

          -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 implicitely 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.

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              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.

          -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 renegociated 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

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          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
          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)

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