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author | marha <marha@users.sourceforge.net> | 2009-06-28 22:07:26 +0000 |
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committer | marha <marha@users.sourceforge.net> | 2009-06-28 22:07:26 +0000 |
commit | 3562e78743202e43aec8727005182a2558117eca (patch) | |
tree | 8f9113a77d12470c5c851a2a8e4cb02e89df7d43 /openssl/doc/apps/s_client.pod | |
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Diffstat (limited to 'openssl/doc/apps/s_client.pod')
-rw-r--r-- | openssl/doc/apps/s_client.pod | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/openssl/doc/apps/s_client.pod b/openssl/doc/apps/s_client.pod new file mode 100644 index 000000000..c44d357cf --- /dev/null +++ b/openssl/doc/apps/s_client.pod @@ -0,0 +1,297 @@ + +=pod + +=head1 NAME + +s_client - SSL/TLS client program + +=head1 SYNOPSIS + +B<openssl> B<s_client> +[B<-connect host:port>] +[B<-verify depth>] +[B<-cert filename>] +[B<-certform DER|PEM>] +[B<-key filename>] +[B<-keyform DER|PEM>] +[B<-pass arg>] +[B<-CApath directory>] +[B<-CAfile filename>] +[B<-reconnect>] +[B<-pause>] +[B<-showcerts>] +[B<-debug>] +[B<-msg>] +[B<-nbio_test>] +[B<-state>] +[B<-nbio>] +[B<-crlf>] +[B<-ign_eof>] +[B<-quiet>] +[B<-ssl2>] +[B<-ssl3>] +[B<-tls1>] +[B<-no_ssl2>] +[B<-no_ssl3>] +[B<-no_tls1>] +[B<-bugs>] +[B<-cipher cipherlist>] +[B<-starttls protocol>] +[B<-engine id>] +[B<-tlsextdebug>] +[B<-no_ticket>] +[B<-sess_out filename>] +[B<-sess_in filename>] +[B<-rand file(s)>] + +=head1 DESCRIPTION + +The B<s_client> command implements a generic SSL/TLS client which connects +to a remote host using SSL/TLS. It is a I<very> useful diagnostic tool for +SSL servers. + +=head1 OPTIONS + +=over 4 + +=item B<-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. + +=item B<-cert certname> + +The certificate to use, if one is requested by the server. The default is +not to use a certificate. + +=item B<-certform format> + +The certificate format to use: DER or PEM. PEM is the default. + +=item B<-key keyfile> + +The private key to use. If not specified then the certificate file will +be used. + +=item B<-keyform format> + +The private format to use: DER or PEM. PEM is the default. + +=item B<-pass arg> + +the private key password source. For more information about the format of B<arg> +see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. + +=item B<-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. + +=item B<-CApath directory> + +The directory to use for server certificate verification. This directory +must be in "hash format", see B<verify> for more information. These are +also used when building the client certificate chain. + +=item B<-CAfile file> + +A file containing trusted certificates to use during server authentication +and to use when attempting to build the client certificate chain. + +=item B<-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. + +=item B<-pause> + +pauses 1 second between each read and write call. + +=item B<-showcerts> + +display the whole server certificate chain: normally only the server +certificate itself is displayed. + +=item B<-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. + +=item B<-state> + +prints out the SSL session states. + +=item B<-debug> + +print extensive debugging information including a hex dump of all traffic. + +=item B<-msg> + +show all protocol messages with hex dump. + +=item B<-nbio_test> + +tests non-blocking I/O + +=item B<-nbio> + +turns on non-blocking I/O + +=item B<-crlf> + +this option translated a line feed from the terminal into CR+LF as required +by some servers. + +=item B<-ign_eof> + +inhibit shutting down the connection when end of file is reached in the +input. + +=item B<-quiet> + +inhibit printing of session and certificate information. This implicitly +turns on B<-ign_eof> as well. + +=item B<-ssl2>, B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-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 B<-no_tls> option others will only +support SSL v2 and may need the B<-ssl2> option. + +=item B<-bugs> + +there are several known bug in SSL and TLS implementations. Adding this +option enables various workarounds. + +=item B<-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 B<ciphers> +command for more information. + +=item B<-starttls protocol> + +send the protocol-specific message(s) to switch to TLS for communication. +B<protocol> is a keyword for the intended protocol. Currently, the only +supported keywords are "smtp", "pop3", "imap", and "ftp". + +=item B<-tlsextdebug> + +print out a hex dump of any TLS extensions received from the server. Note: this +option is only available if extension support is explicitly enabled at compile +time + +=item B<-no_ticket> + +disable RFC4507bis session ticket support. Note: this option is only available +if extension support is explicitly enabled at compile time + +=item B<-sess_out filename> + +output SSL session to B<filename> + +=item B<-sess_in sess.pem> + +load SSL session from B<filename>. The client will attempt to resume a +connection from this session. + +=item B<-engine id> + +specifying an engine (by it's unique B<id> string) will cause B<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. + +=item B<-rand file(s)> + +a file or files containing random data used to seed the random number +generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). +Multiple files can be specified separated by a OS-dependent character. +The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for +all others. + +=back + +=head1 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 B<-quiet> nor B<-ign_eof> +have been given), the session will be renegotiated if the line begins with an +B<R>, and if the line begins with a B<Q> or if end of file is reached, the +connection will be closed down. + +=head1 NOTES + +B<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 B<-bugs>, B<-ssl2>, +B<-ssl3>, B<-tls1>, B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1> options can be tried +in case it is a buggy server. In particular you should play with these +options B<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 B<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 B<-prexit> option and send an HTTP request +for an appropriate page. + +If a certificate is specified on the command line using the B<-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 +B<-showcerts> option can be used to show the whole chain. + +Since the SSLv23 client hello cannot include compression methods or extensions +these will only be supported if its use is disabled, for example by using the +B<-no_sslv2> option. + +TLS extensions are only supported in OpenSSL 0.9.8 if they are explictly +enabled at compile time using for example the B<enable-tlsext> switch. + +=head1 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 B<-verify> option should really exit if the server verification +fails. + +The B<-prexit> option is a bit of a hack. We should really report +information whenever a session is renegotiated. + +=head1 SEE ALSO + +L<sess_id(1)|sess_id(1)>, L<s_server(1)|s_server(1)>, L<ciphers(1)|ciphers(1)> + +=cut |