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S_CLIENT(1)                         OpenSSL                        S_CLIENT(1)

N
       s_client - SSL/TLS client program

S
       ooppeennssssll ss_cclliieenntt [--ccoonnnneecctt host:port>] [--vveerriiffyy ddeepptthh] [--cceerrtt ffiilleennaammee]
       [--kkeeyy ffiilleennaammee] [--CCAAppaatthh ddiirreeccttoorryy] [--CCAAffiillee ffiilleennaammee] [--rreeccoonnnneecctt]
       [--ppaauussee] [--sshhoowwcceerrttss] [--ddeebbuugg] [--mmssgg] [--nnbbiioo_tteesstt] [--ssttaattee] [--nnbbiioo]
       [--ccrrllff] [--iiggnn_eeooff] [--qquuiieett] [--ssssll22] [--ssssll33] [--ttllss11] [--nnoo_ssssll22]
       [--nnoo_ssssll33] [--nnoo_ttllss11] [--bbuuggss] [--cciipphheerr cciipphheerrlliisstt] [--eennggiinnee iidd] [--rraanndd
       file((ss))]

D
       The ss_cclliieenntt 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.

O
       --ccoonnnneecctt hhoosstt::ppoorrtt
           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.

       --cceerrtt cceerrttnnaammee
           The certificate to use, if one is requested by the server. The
           default is not to use a certificate.

       --kkeeyy kkeeyyffiillee
           The private key to use. If not specified then the certificate file
           will be used.

       --vveerriiffyy ddeepptthh
           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.

       --CCAAppaatthh ddiirreeccttoorryy
           The directory to use for server certificate verification. This
           directory must be in "hash format", see vveerriiffyy for more informa-
           tion. These are also used when building the client certificate
           chain.

       --CCAAffiillee ffiillee
           A file containing trusted certificates to use during server authen-
           tication and to use when attempting to build the client certificate
           chain.

       --rreeccoonnnneecctt
           reconnects to the same server 5 times using the same session ID,
           this can be used as a test that session caching is working.

       --ppaauussee
           pauses 1 second between each read and write call.

       --sshhoowwcceerrttss
           display the whole server certificate chain: normally only the
           server certificate itself is displayed.

       --pprreexxiitt
           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 certifi-
           cate 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.

       --ssttaattee
           prints out the SSL session states.

       --ddeebbuugg
           print extensive debugging information including a hex dump of all
           traffic.

       --mmssgg
           show all protocol messages with hex dump.

       --nnbbiioo_tteesstt
           tests non-blocking I/O

       --nnbbiioo
           turns on non-blocking I/O

       --ccrrllff
           this option translated a line feed from the terminal into CR+LF as
           required by some servers.

       --iiggnn_eeooff
           inhibit shutting down the connection when end of file is reached in
           the input.

       --qquuiieett
           inhibit printing of session and certificate information.  This
           implicitly turns on --iiggnn_eeooff as well.

       --ssssll22, --ssssll33, --ttllss11, --nnoo_ssssll22, --nnoo_ssssll33, --nnoo_ttllss11
           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 --nnoo_ttllss option oth-
           ers will only support SSL v2 and may need the --ssssll22 option.

       --bbuuggss
           there are several known bug in SSL and TLS implementations. Adding
           this option enables various workarounds.

       --cciipphheerr cciipphheerrlliisstt
           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 cciipphheerrss command for more information.

       --eennggiinnee iidd
           specifying an engine (by it's unique iidd string) will cause ss_cclliieenntt
           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.

       --rraanndd file((ss))
           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 sepa-
           rator is ;; for MS-Windows, ,, for OpenVMS, and :: for all others.

C
       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 --qquuiieett nor
       --iiggnn_eeooff have been given), the session will be renegotiated if the line
       begins with an RR, and if the line begins with a QQ or if end of file is
       reached, the connection will be closed down.

N
       ss_cclliieenntt 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 --bbuuggss, --ssssll22,
       --ssssll33, --ttllss11, --nnoo_ssssll22, --nnoo_ssssll33, --nnoo_ttllss11 can be tried in case it is a
       buggy server. In particular you should play with these options bbeeffoorree
       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 ss_cclliieenntt 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 --pprreexxiitt command and send an HTTP request for an
       appropriate page.

       If a certificate is specified on the command line using the --cceerrtt
       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
       --sshhoowwcceerrttss option can be used to show the whole chain.

B
       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 --vveerriiffyy option should really exit if the server verification fails.

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

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

3rd Berkeley Distribution           0.9.7a                         S_CLIENT(1)

N | S | D | O | C | N | B | S

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