[vset VERSION 1.8.1]
[manpage_begin autoproxy n [vset VERSION]]
[see_also http(n)]
[keywords authentication]
[keywords http]
[keywords proxy]
[moddesc   {HTTP protocol helper modules}]
[titledesc {Automatic HTTP proxy usage and authentication}]
[category  Networking]
[require Tcl "8.5 9"]
[require http [opt 2.0]]
[require autoproxy [opt [vset VERSION]]]
[description]
[para]

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.

[para]

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.

[para]

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.

[include autoproxy-tls-security-notes.inc]

[section "COMMANDS"]

[list_begin definitions]

[call [cmd ::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.

[call [cmd ::autoproxy::cget] [arg "-option"]]

Retrieve individual package configuration options. See [sectref OPTIONS].

[call [cmd ::autoproxy::configure] [opt "-option [arg value]"]]

Configure the autoproxy package. Calling [cmd configure] with no
options will return a list of all option names and values.
See [sectref OPTIONS].

[call [cmd ::autoproxy::tls_connect] [arg 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 [cmd tls_socket].
[para]
The [arg args] list may contain any of the options
supported by the specific TLS package that is in use but
must end with the host and port as the last two items.

[call [cmd ::autoproxy::tunnel_connect] [arg args]]

Connect to a target host throught a proxy. This uses the same CONNECT
HTTP command as the [cmd tls_connect] but does not promote the link
security once the connection is established.
[para]
The [arg args] list may contain any of the options
supported by the specific TLS package that is in use but
must end with the host and port as the last two items.

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

[call [cmd ::autoproxy::tls_socket] [arg 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.

[list_end]

[section {OPTIONS}]

[list_begin options]

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

[opt_def -port number]
[opt_def -proxy_port number]
Set the proxy port number. This is normally set up by [cmd init].
e.g. [cmd configure] [option -port] [arg 3128]

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

[opt_def -authProc procedure]
This option may be used to set an application defined procedure to be
called when [cmd configure] [option -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.

[opt_def -basic]
Following options are for configuring the Basic authentication
scheme parameters. See [sectref "Basic Authentication"].
To unset the proxy authentication information retained from a previous
call of this function either "--" or no additional parameters can be
supplied. This will remove the existing authentication information.

[opt_def -tls_package packagename]
This option may be used to configure the Tcl package to use for
TLS support. Valid package names are [const tls] (default)
and [const twapi].

[list_end]

[section "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.

[para]

The following options exists for this scheme:
[list_begin options]
[opt_def "-username" "name"]
The username required to authenticate with the configured proxy.
[opt_def "-password" "password"]
The password required for the username specified.
[opt_def "-realm" "realm"]
This option is not used by this package but may be used in requesting
authentication details from the user.
[opt_def "--"]
The end-of-options indicator may be used alone to unset any
authentication details currently enabled.

[list_end]

[section "EXAMPLES"]

[para]
[example {
package require autoproxy
autoproxy::init
autoproxy::configure -basic -username ME -password SEKRET
set tok [http::geturl http://wiki.tcl.tk/]
http::data $tok
}]

[example {
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/]
}]

[section {REFERENCES}]

[list_begin enumerated]

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

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

[list_end]

[section {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.

[section AUTHORS]
Pat Thoyts

[vset CATEGORY {http :: autoproxy}]
[include ../common-text/feedback.inc]
[manpage_end]
