NAME¶
autoproxy - Automatic HTTP proxy usage and authentication
SYNOPSIS¶
package require
Tcl 8.2
package require
http ?2.0?
package require
autoproxy ?1.5.1?
::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
