autoproxy - Automatic HTTP proxy usage and authentication

package require Tcl 8.2 package require http ?2.0? package require autoproxy ?1.2.0? ::autoproxy::init ::autoproxy::cget -optionname ::autoproxy::configure ?-option value?

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.

::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 -optionname

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.

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 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.

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

[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)

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

Pat Thoyts

http(n)

authentication, http, proxy