SSLCLIENT(1)                 DACS Commands Manual                 SSLCLIENT(1)

       sslclient - an SSL client

       sslclient [dacsoptions[1]] [-caf | --ca_cert_file filename]
                 [-cad | --ca_cert_dir dirname]
                 [-ccf | --cert_chain_file filename]
                 [-C | --ciphers cipherstring]
                 [[-dvp] | [--default_verify_paths] cipherstring]
                 [-h | --help] [-kf | --key_file filename]
                 [-kft | --key_file_type pem | asn1]
                 [-p | -sp | [--server_port] portnum]
                 [-r | --random filename]
                 [[-sm | --server_match regex ]...]
                 [-vd | --verify_depth depth]
                 [-vt | --verify_type none | peer] [--] server [:port ]

       This program is part of the DACS suite. It can be used with the usual
       DACS command line options (dacsoptions[1]), provided they all appear
       before the program-specific flags (note that the -un flag can be used
       to suppress configuration file processing).  sslclient is also used by
       the dacshttp(1)[2] command and by requests generated internally by DACS

       The sslclient utility acts as an SSL client. After establishing a
       bidirectional SSL connection with an SSL server, it forwards its
       standard input to the SSL server and writes data produced by the SSL
       server to sslclient's standard output.

       sslclient connects to server (a domain name or IP address). If a port
       number suffix is given (port), it is used; otherwise, if a port number
       is specified as a separate command line argument
       (--server_portportnum), that is used; failing that, the default SSL
       port for https (443)[3] is used.

       The program reads from its standard input and the server asynchronously
       (using non-blocking I/O). Note that the server side might need to see
       end-of-file on its input before its output is returned to sslclient.

       This program's underlying SSL functionality is provided by OpenSSL[4].

       sslclient recognizes these options:

       -caf filename
       --ca_cert_file filename
           This identifies filename as a file of CA certificates in PEM
           format. This is the CAfile argument to the
           OpenSSL[4]SSL_CTX_load_verify_locations()[5] function. It is
           similar to mod_ssl's[6]SSLCACertificateFile[7] directive, except
           that it is used to verify the server's SSL certificate.

       -cad dirname
       --ca_cert_dir dirname
           This identifies dirname as a directory containing CA certificates
           in PEM format, one certificate per file. This is the CApath
           argument to the OpenSSL[4]SSL_CTX_load_verify_locations()[5]
           function. It is similar to mod_ssl's[6]SSLCACertificatePath[8]
           directive, except that it is used to verify the server's

       -ccf filename
       --cert_chain_file filename
           This causes the client certificate chain to be loaded from
           filename, a file containing certificates in PEM format. This is the
           file argument to the
           OpenSSL[4]SSL_CTX_use_certificate_chain_file()[9] function. It is
           similar to mod_ssl's[6]SSLCACertificateChainFile[10] directive,
           except that it is used for the client's chain.

               If you want the client certificate to be sent you must also
               specify the -kf flag.

       -C cipherstring
       --ciphers cipherstring
           This sets the list of ciphers to be used to cipherstring. This is
           the str argument to the OpenSSL[4]SSL_CTX_set_cipher_list()[11]
           function. It is similar to mod_ssl's[6]SSLCipherSuite[12]

           This flag tells sslclient to use default locations for finding CA
           certificates. It results in a call to the
           OpenSSL[4]SSL_CTX_set_default_verify_paths() function.

           Print a usage synopsis.

       -kf filename
       --key_file filename
           This sets sslclient's private key to the first private key found in
           filename. This is the file argument to the
           OpenSSL[4]SSL_CTX_usePrivateKey_file() function. The default
           private key file type is PEM. If the key has been encrypted, the
           program will prompt for the passphrase.

       -kft type
       --key_file_type type
           The private key file type is set to type, which must be either pem
           or asn1 (case insensitive). The default private key file type is

       -p portnum
       -sp portnum
       --server_port portnum
           Unless appended to the server argument, portnum is the port number
           to use, overriding the default port (443).

       -r filename
       --random filename
           Seed material for the PRNG is read from filename. This is the
           filename argument to the OpenSSL[4]RAND_load_file() function.

       -sm regex
       --server_match regex
           This argument, which may be repeated, specifies a constraint on the
           server's identity by matching an attribute value in the server's
           certificate against regex. These tests are made immediately after
           an SSL connection is established. Each regex is an IEEE Std 1003.2
           ("POSIX.2") regular expression with extended expressions and case
           insensitivity (REG_EXTENDED | REG_ICASE). See below[13] for the
           matching algorithm.

       -vd depth
       --verify_depth depth
           This sets the maximum depth for certificate chain verification to
           depth. This is the depth argument to the
           OpenSSL[4]SSL_CTX_set_verify_depth() function.

       -vt type
       --verify_type type
           This sets the verification mode to type, which must be either none
           or peer (case insensitive). This is the mode argument to the
           OpenSSL[4]SSL_CTX_set_verify() function.

           This argument explicitly marks the end of the flags.

       The DACS-v (or --verbose) flag causes the program to show some of the
       server's SSL certificate, print feedback about regular expression
       matching, and so on. If sslclient is not doing what you expect, try
       using this flag.

   Server Identity Verification
       If the server presents a valid SSL (X.509) certificate, a set of checks
       is applied to it to help ensure that sslclient is communicating with
       the intended entity. Verification is successful and checking is
       terminated as soon as any test is successful. If no test succeeds, the
       program terminates immediately.

           You can use a command like the following one to display an X.509
           certificate to stdout in text form:

               % openssl x509 -noout -text < cert.crt

           Here, cert.crt is the certificate to display.

       The server certificate's subjectAltName extension fields have the
       format field-name:field-value. For each such field, tests are made in
       the following sequence:

        1. the entire field is matched against each of the regular expressions
           given on the command line.

        2. if the previous test failed and field-name is "DNS" (exact match),
           it is compared case insensitively to the server's name (as given on
           the command line).

        3. if the previous test failed and if the field-name is "IP Address"
           (exact match), it is compared to the server's name (exact match),
           which is assumed to be an IP address (as given on the command

       If the above procedure is unsuccessful and the server certificate's
       commonName attribute value is available, it is matched against each of
       the regular expressions given on the command line.

       The following command line attempts to connect to port 443 at and prints to stdout the server's response to a request for
       the home page:

           % perl -e 'printf "GET / HTTP/1.0\n\n";' | sslclient

       When used with DACS logging configured, messages are directed to a log
       file, otherwise error messages and verbose output are written to
       stderr. The program exits 0 if everything was fine, 1 if an error

       A wrapper mode of operation might be useful.

       It would also be useful to have a mode where it listens for an SSL
       connection for input (rather than its standard input) and then relays
       data over that connection to a specified server, possibly but not
       necessarily via SSL. This mode might run on a firewall host to forward
       an approved incoming SSL connection (presumably authenticated by a
       client certificate, and possibly by a DACS ruleset) to a service
       running on an interior host, for instance.

       dacshttp(1)[2], openssl(1)[4], s_client(1)[14], stunnel(1)[15],
       curl(1)[16], sslwrap(1)[17], and others, and regex(3)[18].

       A variety of reference material on SSL/TLS is available. Perhaps best
       is Network Security with OpenSSL by John Viega, Matt Messier, and
       Pravir Chandra, O'Reilly & Associates, Inc., 2002. Also useful are
       SSL/TLS Strong Encryption: An Introduction[19], Netscape SSL 3.0
       Specification[20], and RFC 2246[21].

       Distributed Systems Software ([22])

       Copyright2003-2013 Distributed Systems Software. See the LICENSE[23]
       file that accompanies the distribution for licensing information.

        1. dacsoptions

        2. dacshttp(1)

        3. default SSL port for https (443)

        4. OpenSSL

        5. SSL_CTX_load_verify_locations()

        6. mod_ssl's

        7. SSLCACertificateFile

        8. SSLCACertificatePath

        9. SSL_CTX_use_certificate_chain_file()

       10. SSLCACertificateChainFile

       11. SSL_CTX_set_cipher_list()

       12. SSLCipherSuite

       13. below

       14. s_client(1)

       15. stunnel(1)

       16. curl(1)

       17. sslwrap(1)

       18. regex(3)

       19. SSL/TLS Strong Encryption: An Introduction

       20. Netscape SSL 3.0 Specification

       21. RFC 2246


       23. LICENSE

DACS 1.4.28b                      02/04/2014                      SSLCLIENT(1)