b197c770a6
(cherry picked from commit cba3f1c739)
Conflicts:
doc/apps/s_client.pod
doc/apps/s_server.pod
338 lines
10 KiB
Text
338 lines
10 KiB
Text
|
|
=pod
|
|
|
|
=head1 NAME
|
|
|
|
s_client - SSL/TLS client program
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
B<openssl> B<s_client>
|
|
[B<-connect host:port>]
|
|
[B<-servername name>]
|
|
[B<-verify depth>]
|
|
[B<-verify_return_error>]
|
|
[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<-no_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<-serverpref>]
|
|
[B<-starttls protocol>]
|
|
[B<-engine id>]
|
|
[B<-tlsextdebug>]
|
|
[B<-no_ticket>]
|
|
[B<-sess_out filename>]
|
|
[B<-sess_in filename>]
|
|
[B<-rand file(s)>]
|
|
[B<-status>]
|
|
|
|
=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<-servername name>
|
|
|
|
Set the TLS SNI (Server Name Indication) extension in the ClientHello message.
|
|
|
|
=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<-verify_return_error>
|
|
|
|
Return verification errors instead of continuing. This will typically
|
|
abort the handshake with a fatal error.
|
|
|
|
=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<-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig>
|
|
|
|
Set various certificate chain valiadition option. See the
|
|
L<B<verify>|verify(1)> manual page for details.
|
|
|
|
=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<-no_ign_eof>
|
|
|
|
shut down the connection when end of file is reached in the input.
|
|
Can be used to override the implicit B<-ign_eof> after B<-quiet>.
|
|
|
|
=item B<-psk_identity identity>
|
|
|
|
Use the PSK identity B<identity> when using a PSK cipher suite.
|
|
|
|
=item B<-psk key>
|
|
|
|
Use the PSK key B<key> when using a PSK cipher suite. The key is
|
|
given as a hexadecimal number without leading 0x, for example -psk
|
|
1a2b3c4d.
|
|
|
|
=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<-serverpref>
|
|
|
|
use the server's cipher preferences; only used for SSLV2.
|
|
|
|
=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.
|
|
|
|
=item B<-no_ticket>
|
|
|
|
disable RFC4507bis session ticket support.
|
|
|
|
=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 its 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.
|
|
|
|
=item B<-status>
|
|
|
|
sends a certificate status request to the server (OCSP stapling). The server
|
|
response (if any) is printed out.
|
|
|
|
=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.
|
|
|
|
The B<s_client> utility is a test tool and is designed to continue the
|
|
handshake after any certificate verification errors. As a result it will
|
|
accept any certificate chain (trusted or not) sent by the peer. None test
|
|
applications should B<not> do this as it makes them vulnerable to a MITM
|
|
attack. This behaviour can be changed by with the B<-verify_return_error>
|
|
option: any verify errors are then returned aborting the handshake.
|
|
|
|
=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<-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
|