DESCRIPTIONThe s_client command implements a generic
SSL/TLS client which connects to a remote host using SSL/TLS. It
can request a page from the server and includes the time to transfer
the payload data in its timing measurements. It measures the number
of connections within a given timeframe, the amount of data transferred
(if any), and calculates the average time spent for one connection. OPTIONS
-connect host:port This specifies the host and optional port to connect to.
-www page This specifies the page to GET from the server. A value of
'/' gets the index.htm[l] page. If this parameter is not specified,
then s_time will only perform the handshake
to establish SSL connections but not transfer any payload data.
-cert certname The certificate to use, if one is requested by the server.
The default is not to use a certificate. The file is in PEM format.
-key keyfile The private key to use. If not specified then the certificate
file will be used. The file is in PEM format.
-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.
-new performs the timing test using a new session ID for each connection.
If neither -new nor -reuse are specified,
they are both on by default and executed in sequence.
-reuse performs the timing test using the same session ID; this can
be used as a test that session caching is working. If neither -new nor -reuse are
specified, they are both on by default and executed in sequence.
-nbio turns on non-blocking I/O.
-ssl2, -ssl3 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.
The timing program is not as rich in options to turn protocols on
and off as the s_client(1) program and may not connect
to all servers. 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 -ssl3 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(1) command
for more information.
-time length specifies how long (in seconds) s_time should
establish connections and optionally transfer payload data from
a server. Server and client performance and the link speed determine
how many connections s_time can establish.
NOTESs_client can be used to measure the performance
of an SSL connection. To connect to an SSL HTTP server and get the
default page the command
would typically be used (https uses port 443). 'commoncipher'
is a cipher to which both client and server can agree, see the ciphers(1) command
for details.
If the handshake fails then there are several possible causes,
if it is nothing obvious like no client certificate then the -bugs, -ssl2, -ssl3 options
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(1) 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 option
of s_client(1) 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.
RestrictionsBecause this program does not have all the options of the s_client(1) program
to turn protocols on and off, you may not be able to measure the
performance of all protocols with all servers.
The -verify option should really exit
if the server verification fails.
HP Open Source Security for OpenVMS Volume 2:... 
OpenSSL Command Line Interface (CLI) Reference
