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s_client (1)
  • >> s_client (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • s_client (1) ( Linux man: Команды и прикладные программы пользовательского уровня )


         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] [-nbio_test] [-state] [-nbio] [-crlf] [-ign_eof]
         [-quiet] [-ssl2] [-ssl3] [-tls1] [-no_ssl2] [-no_ssl3]
         [-no_tls1] [-bugs] [-cipher cipherlist] [-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 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.
             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.
             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 is
             reached in the input.
             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.
             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
         -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.


         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.


         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
         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.


         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.


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

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