NAME

       autoproxy - Automatic HTTP proxy usage and authentication

SYNOPSIS

       package require Tcl  8.2

       package require http  ?2.0?

       package require autoproxy  ?1.5.3?

       ::autoproxy::init

       ::autoproxy::cget -option

       ::autoproxy::configure ?-option value?

       ::autoproxy::tls_connect args

       ::autoproxy::tunnel_connect args

       ::autoproxy::tls_socket args

_________________________________________________________________

DESCRIPTION

       This  package  attempts to automate the use of HTTP proxy servers in Tcl HTTP client code.
       It tries to initialize the web access settings from system standard locations and  can  be
       configured to negotiate authentication with the proxy if required.

       On  Unix  the  standard for identifying the local HTTP proxy server seems to be to use the
       environment variable http_proxy or ftp_proxy and no_proxy to  list  those  domains  to  be
       excluded  from proxying.  On Windows we can retrieve the Internet Settings values from the
       registry to obtain pretty much the same information.  With this information we can setup a
       suitable  filter  procedure  for the Tcl http package and arrange for automatic use of the
       proxy.

       There seem to be a number of ways that the http_proxy environment variable may be set  up.
       Either  a  plain  host:port  or  more  commonly  a  URL  and sometimes the URL may contain
       authentication parameters or these  may  be  requested  from  the  user  or  provided  via
       http_proxy_user and http_proxy_pass. This package attempts to deal with all these schemes.
       It will do it's best to get the required parameters from the environment or  registry  and
       if it fails can be reconfigured.

COMMANDS

       ::autoproxy::init
              Initialize  the  autoproxy  package from system resources. Under unix this means we
              look for environment variables. Under windows we  look  for  the  same  environment
              variables but also look at the registry settings used by Internet Explorer.

       ::autoproxy::cget -option
              Retrieve individual package configuration options. See OPTIONS.

       ::autoproxy::configure ?-option value?
              Configure  the  autoproxy  package. Calling configure with no options will return a
              list of all option names and values.  See OPTIONS.

       ::autoproxy::tls_connect args
              Connect to a secure socket through a proxy. HTTP proxy servers permit  the  use  of
              the  CONNECT  HTTP  command to open a link through the proxy to the target machine.
              This function hides the details. For use with the http package see tls_socket.

              The args list may contain any of the tls package options but must end with the host
              and port as the last two items.

       ::autoproxy::tunnel_connect args
              Connect  to a target host throught a proxy. This uses the same CONNECT HTTP command
              as the tls_connect but does not promote the link security once  the  connection  is
              established.

              The args list may contain any of the tls package options but must end with the host
              and port as the last two items.

              Note that many proxy servers will permit CONNECT calls to a limited set of ports  -
              typically only port 443 (the secure HTTP port).

       ::autoproxy::tls_socket args
              This function is to be used to register a proxy-aware secure socket handler for the
              https protocol. It may only be used  with  the  Tcl  http  package  and  should  be
              registered  using  the  http::register command (see the examples below). The job of
              actually creating the tunnelled connection is done by the tls_connect  command  and
              this may be used when not registering with the http package.

OPTIONS

       -host hostname

       -proxy_host hostname
              Set  the proxy hostname. This is normally set up by init but may be configured here
              as well.

       -port number

       -proxy_port number
              Set the proxy port number. This is normally set up by init.  e.g.  configure  -port
              3128

       -no_proxy list
              You  may  manipulate  the  no_proxy  list that was setup by init. The value of this
              option is a tcl list of strings that are matched  against  the  http  request  host
              using  the  tcl  string  match command. Therefore glob patterns are permitted.  For
              instance, configure -no_proxy *.localdomain

       -authProc procedure
              This option may be used to set an application defined procedure to be  called  when
              configure  -basic  is called with either no or insufficient authentication details.
              This can be used to present  a  dialog  to  the  user  to  request  the  additional
              information.

       -basic Following  options  are for configuring the Basic authentication scheme parameters.
              See Basic Authentication.

BASIC AUTHENTICATION

       Basic is the simplest and most commonly  use  HTTP  proxy  authentication  scheme.  It  is
       described  in  (1 section 11) and also in (2). It offers no privacy whatsoever and its use
       should be discouraged in favour of more secure alternatives like Digest. To perform  Basic
       authentication  the client base64 encodes the username and plaintext password separated by
       a colon. This encoded text is prefixed with the word "Basic" and a space.

       The following options exists for this scheme:

       -username name
              The username required to authenticate with the configured proxy.

       -password password
              The password required for the username specified.

       -realm realm
              This option is not used.

EXAMPLES

              package require autoproxy
              autoproxy::init
              autoproxy::configure -basic -username ME -password SEKRET
              set tok [http::geturl http://wiki.tcl.tk/]
              http::data $tok
              package require http
              package require tls
              package require autoproxy
              autoproxy::init
              http::register https 443 autoproxy::tls_socket
              set tok [http::geturl https://www.example.com/]

REFERENCES

       [1]    Berners-Lee, T., Fielding R. and  Frystyk,  H.   "Hypertext  Transfer  Protocol  --
              HTTP/1.0", RFC 1945, May 1996, (http://www.rfc-editor.org/rfc/rfc1945.txt)

       [2]    Franks,  J.  et al.  "HTTP Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999 (http://www.rfc-editor.org/rfc/rfc2617.txt)

BUGS

       At this time only Basic authentication (1) (2) is supported. It is planned to add  support
       for Digest (2) and NTLM in the future.

AUTHORS

       Pat Thoyts

BUGS, IDEAS, FEEDBACK

       This  document,  and  the  package  it  describes, will undoubtedly contain bugs and other
       problems.  Please report such in the category http :: autoproxy of the Tcllib SF  Trackers
       [http://sourceforge.net/tracker/?group_id=12883].    Please  also  report  any  ideas  for
       enhancements you may have for either package and/or documentation.

SEE ALSO

       http(3tcl)

KEYWORDS

       authentication, http, proxy

CATEGORY

       Networking