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Privoxy User Manual

By: Privoxy Developers

$Id: user-manual.sgml,v 1.60 2002/03/27 01:57:34 hal9 Exp $

The user manual gives users information on how to install, configure and use
Privoxy. Privoxy is a web proxy with advanced filtering capabilities for
protecting privacy, filtering web page content, managing cookies, controlling
access, and removing ads, banners, pop-ups and other obnoxious Internet Junk.
Privoxy has a very flexible configuration and can be customized to suit
individual needs and tastes. Privoxy has application for both stand-alone
systems and multi-user networks.

You can find the latest version of the user manual at http://www.privoxy.org/
user-manual/.

-------------------------------------------------------------------------------

Table of Contents
1. Introduction
   
    1.1. New Features
   
2. Installation
   
    2.1. Source
    2.2. Red Hat
    2.3. SuSE
    2.4. OS/2
    2.5. Windows
    2.6. Other
   
3. Privoxy Configuration
   
    3.1. Controlling Privoxy with Your Web Browser
    3.2. Configuration Files Overview
    3.3. The Main Configuration File
       
        3.3.1. Defining Other Configuration Files
        3.3.2. Other Configuration Options
        3.3.3. Access Control List (ACL)
        3.3.4. Forwarding
        3.3.5. Windows GUI Options
       
    3.4. The Actions File
       
        3.4.1. URL Domain and Path Syntax
        3.4.2. Actions
        3.4.3. Aliases
       
    3.5. The Filter File
    3.6. Templates
   
4. Quickstart to Using Privoxy
   
    4.1. Command Line Options
   
5. Contacting the Developers, Bug Reporting and Feature Requests
6. Copyright and History
   
    6.1. License
    6.2. History
   
7. See also
8. Appendix
   
    8.1. Regular Expressions
    8.2. Privoxy's Internal Pages
    8.3. Anatomy of an Action
   
1. Introduction

Privoxy is a web proxy with advanced filtering capabilities for protecting
privacy, filtering web page content, managing cookies, controlling access, and
removing ads, banners, pop-ups and other obnoxious Internet junk. Privoxy has a
very flexible configuration and can be customized to suit individual needs and
tastes. Privoxy has application for both stand-alone systems and multi-user
networks.

Privoxy is based on the code of the Internet Junkbuster. Junkbuster was
originally written by JunkBusters Corporation, and was released as free
open-source software under the GNU GPL. Stefan Waldherr made many improvements,
and started the SourceForge project to continue development.

Privoxy continues the Junkbuster tradition, but adds many refinements and
enhancements.

This documentation is included with the current BETA version of Privoxy and is
mostly complete at this point. The most up to date reference for the time being
is still the comments in the source files and in the individual configuration
files. Development of version 3.0 is currently nearing completion, and includes
many significant changes and enhancements over earlier versions. The target
release date for stable v3.0 is "soon" ;-)

Since this is a BETA version, not all new features are well tested. This
documentation may be slightly out of sync as a result (especially with CVS
sources). And there may be bugs, though hopefully not many!

-------------------------------------------------------------------------------

1.1. New Features

In addition to Internet Junkbuster's traditional feature of ad and banner
blocking and cookie management, Privoxy provides new features, some of them
currently under development:

  * Integrated browser based configuration and control utility (http://p.p).
    Browser-based tracing of rule and filter effects.
   
  * Blocking of annoying pop-up browser windows.
   
  * HTTP/1.1 compliant (most, but not all 1.1 features are supported).
   
  * Support for Perl Compatible Regular Expressions in the configuration files,
    and generally a more sophisticated and flexible configuration syntax over
    previous versions.
   
  * GIF de-animation.
   
  * Web page content filtering (removes banners based on size, invisible
    "web-bugs", JavaScript, pop-ups, status bar abuse, etc.)
   
  * Bypass many click-tracking scripts (avoids script redirection).
   
  * Multi-threaded (POSIX and native threads).
   
  * Auto-detection and re-reading of config file changes.
   
  * User-customizable HTML templates (e.g. 404 error page).
   
  * Improved cookie management features (e.g. session based cookies).
   
  * Builds from source on most UNIX-like systems. Packages available for: Linux
    (RedHat, SuSE, or Debian), Windows, Sun Solaris, Mac OSX, OS/2, HP-UX 11
    and AmigaOS.
   
  * In addition, the configuration is much more powerful and versatile
    over-all.
   
-------------------------------------------------------------------------------

2. Installation

Privoxy is available as raw source code, or pre-compiled binaries. See the 
Privoxy Home Page for binaries and current release info. Privoxy is also
available via CVS. This is the recommended approach at this time. But please be
aware that CVS is constantly changing, and it may break in mysterious ways.

-------------------------------------------------------------------------------

2.1. Source

For gzipped tar archives, unpack the source:

 tar xzvf privoxy-2.9.13-beta-src* [.tgz or .tar.gz]                           
 cd privoxy-2.9.13-beta                                                        
                                                                               

For retrieving the current CVS sources, you'll need the CVS package installed
first. To download CVS source:

  cvs -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa login          
  cvs -z3 -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa co current 
  cd current                                                                         
                                                                                     

This will create a directory named current/, which will contain the source
tree.

Then, in either case, to build from tarball/CVS source:

 ./configure      (--help to see options)                                      
 make             (the make from gnu, gmake for *BSD)                          
 su                                                                            
 make -n install  (to see where all the files will go)                         
 make install     (to really install)                                          
                                                                               

For Redhat and SuSE Linux RPM packages, see below.

-------------------------------------------------------------------------------

2.2. Red Hat

To build Redhat RPM packages, install source as above. Then:

 autoheader                                                                    
 autoconf                                                                      
 ./configure                                                                   
 make redhat-dist                                                              
                                                                               

This will create both binary and src RPMs in the usual places. Example:

   /usr/src/redhat/RPMS/i686/privoxy-2.9.11-1.i686.rpm

   /usr/src/redhat/SRPMS/privoxy-2.9.11-1.src.rpm

To install, of course:

 rpm -Uvv /usr/src/redhat/RPMS/i686/privoxy-2.9.11-1.i686.rpm                  
                                                                               

This will place the Privoxy configuration files in /etc/privoxy/, and log files
in /var/log/privoxy/.

-------------------------------------------------------------------------------

2.3. SuSE

To build SuSE RPM packages, install source as above. Then:

 autoheader                                                                    
 autoconf                                                                      
 ./configure                                                                   
 make suse-dist                                                                
                                                                               

This will create both binary and src RPMs in the usual places. Example:

   /usr/src/packages/RPMS/i686/privoxy-2.9.11-1.i686.rpm

   /usr/src/packages/SRPMS/privoxy-2.9.11-1.src.rpm

To install, of course:

 rpm -Uvv /usr/src/packages/RPMS/i686/privoxy-2.9.11-1.i686.rpm                
                                                                               

This will place the Privoxy configuration files in /etc/privoxy/, and log files
in /var/log/privoxy/.

-------------------------------------------------------------------------------

2.4. OS/2

Privoxy is packaged in a WarpIN self- installing archive. The self-installing
program will be named depending on the release version, something like:
ijbos2_setup_1.2.3.exe. In order to install it, simply run this executable or
double-click on its icon and follow the WarpIN installation panels. A shadow of
the Privoxy executable will be placed in your startup folder so it will start
automatically whenever OS/2 starts.

The directory you choose to install Privoxy into will contain all of the
configuration files.

If you would like to build binary images on OS/2 yourself, you will need a few
Unix-like tools: autoconf, autoheader and sh. These tools will be used to
create the required config.h file, which is not part of the source distribution
because it differs based on platform. You will also need a compiler. The
distribution has been created using IBM VisualAge compilers, but you can use
any compiler you like. GCC/EMX has the disadvantage of needing to be
single-threaded due to a limitation of EMX's implementation of the select()
socket call.

In addition to needing the source code distribution as outlined earlier, you
will want to extract the os2seutp directory from CVS:

 cvs -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa login           
 cvs -z3 -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa co os2setup 
                                                                                     

This will create a directory named os2setup/, which will contain the
Makefile.vac makefile and os2build.cmd which is used to completely create the
binary distribution. The sequence of events for building the executable for
yourself goes something like this:

 cd current                                                                    
 autoheader                                                                    
 autoconf                                                                      
 sh configure                                                                  
 cd ..\os2setup                                                                
 nmake -f Makefile.vac                                                         
                                                                               

You will see this sequence laid out in os2build.cmd.

-------------------------------------------------------------------------------

2.5. Windows

Click-click. (I need help on this. Not a clue here. Also for configuration
section below. HB.)

-------------------------------------------------------------------------------

2.6. Other

Some quick notes on other Operating Systems.

For FreeBSD (and other *BSDs?), the build will require gmake instead of the
included make. gmake is available from http://www.gnu.org. The rest should be
the same as above for Linux/Unix.

-------------------------------------------------------------------------------

3. Privoxy Configuration

All Privoxy configuration is kept in text files. These files can be edited with
a text editor. Many important aspects of Privoxy can also be controlled easily
with a web browser.

-------------------------------------------------------------------------------

3.1. Controlling Privoxy with Your Web Browser

Privoxy can be reached by the special URL http://p.p/ (or alternately http://
www.privoxy.org/config/), which is an internal page. You will see the following
section: 

Please choose from the following options:                                      
                                                                               
    * Show information about the current configuration                         
    * Show the source code version numbers                                     
    * Show the client's request headers.                                       
    * Show which actions apply to a URL and why                                
    * Toggle Privoxy on or off                                                 
    * Edit the actions list                                                    
                                                                               
                                                                               

This should be self-explanatory. Note the last item is an editor for the
"actions list", which is where much of the ad, banner, cookie, and URL blocking
magic is configured as well as other advanced features of Privoxy. This is an
easy way to adjust various aspects of Privoxy configuration. The actions file,
and other configuration files, are explained in detail below. Privoxy will
automatically detect any changes to these files.

"Toggle Privoxy On or Off" is handy for sites that might have problems with
your current actions and filters, or just to test if a site misbehaves, whether
it is Privoxy causing the problem or not. Privoxy continues to run as a proxy
in this case, but all filtering is disabled. 

-------------------------------------------------------------------------------

3.2. Configuration Files Overview

For Unix, *BSD and Linux, all configuration files are located in /etc/privoxy/
by default. For MS Windows, OS/2, and AmigaOS these are all in the same
directory as the Privoxy executable. The name and number of configuration files
has changed from previous versions, and is subject to change as development
progresses.

The installed defaults provide a reasonable starting point, though possibly
aggressive by some standards. For the time being, there are only three default
configuration files (this will change in time):

  * The main configuration file is named config on Linux, Unix, BSD, OS/2, and
    AmigaOS and config.txt on Windows.
   
  * The default.action file is used to define various "actions" relating to
    images, banners, pop-ups, access restrictions, banners and cookies. There
    is a CGI based editor for this file that can be accessed via http://p.p.
    (Other actions files are included as well with differing levels of
    filtering and blocking, e.g. ijb-basic.action.)
   
  * The default.filter file can be used to re-write the raw page content,
    including viewable text as well as embedded HTML and JavaScript, and
    whatever else lurks on any given web page.
   
default.action and default.filter can use Perl style regular expressions for
maximum flexibility. All files use the "#" character to denote a comment. Such
lines are not processed by Privoxy. After making any changes, there is no need
to restart Privoxy in order for the changes to take effect. Privoxy should
detect such changes automatically.

While under development, the configuration content is subject to change. The
below documentation may not be accurate by the time you read this. Also, what
constitutes a "default" setting, may change, so please check all your
configuration files on important issues.

-------------------------------------------------------------------------------

3.3. The Main Configuration File

Again, the main configuration file is named config on Linux/Unix/BSD and OS/2,
and config.txt on Windows. Configuration lines consist of an initial keyword
followed by a list of values, all separated by whitespace (any number of spaces
or tabs). For example:

  blockfile blocklist.ini
   

Indicates that the blockfile is named "blocklist.ini". (A default installation
does not use this.)

A "#" indicates a comment. Any part of a line following a "#" is ignored,
except if the "#" is preceded by a "\".

Thus, by placing a "#" at the start of an existing configuration line, you can
make it a comment and it will be treated as if it weren't there. This is called
"commenting out" an option and can be useful to turn off features: If you
comment out the "logfile" line, Privoxy will not log to a file at all. Watch
for the "default:" section in each explanation to see what happens if the
option is left unset (or commented out).

Long lines can be continued on the next line by using a "\" as the very last
character.

There are various aspects of Privoxy behavior that can be tuned.

-------------------------------------------------------------------------------

3.3.1. Defining Other Configuration Files

Privoxy can use a number of other files to tell it what ads to block, what
cookies to accept, etc. This section of the configuration file tells Privoxy
where to find all those other files.

On Windows and AmigaOS, Privoxy looks for these files in the same directory as
the executable. On Unix and OS/2, Privoxy looks for these files in the current
working directory. In either case, an absolute path name can be used to avoid
problems.

When development goes modular and multi-user, the blocker, filter, and per-user
config will be stored in subdirectories of "confdir". For now, only confdir/
templates is used for storing HTML templates for CGI results.

The location of the configuration files:

  confdir /etc/privoxy       # No trailing /, please.
   

The directory where all logging (i.e. logfile and jarfile) takes place. No
trailing "/", please:

  logdir /var/log/privoxy
   

Note that all file specifications below are relative to the above two
directories!

The "default.action" file contains patterns to specify the actions to apply to
requests for each site. Default: Cookies to and from all destinations are kept
only during the current browser session (i.e. they are not saved to disk).
Pop-ups are disabled for all sites. All sites are filtered through selected
sections of "default.filter". No sites are blocked. Privoxy displays a
checkboard type pattern for filtered ads and other images. The syntax of this
file is explained in detail below. Other "actions" files are included, and you
are free to use any of them. They have varying degrees of aggressiveness.

  actionsfile default.action
   

The "default.filter" file contains content modification rules that use "regular
expressions". These rules permit powerful changes on the content of Web pages,
e.g., you could disable your favorite JavaScript annoyances, re-write the
actual displayed text, or just have some fun replacing "Microsoft" with
"MicroSuck" wherever it appears on a Web page. Default: whatever the developers
are playing with :-/

Filtering requires buffering the page content, which may appear to slow down
page rendering since nothing is displayed until all content has passed the
filters. (It does not really take longer, but seems that way since the page is
not incrementally displayed.) This effect will be more noticeable on slower
connections. 

  filterfile default.filter
   

The logfile is where all logging and error messages are written. The logfile
can be useful for tracking down a problem with Privoxy (e.g., it's not blocking
an ad you think it should block) but in most cases you probably will never look
at it.

Your logfile will grow indefinitely, and you will probably want to periodically
remove it. On Unix systems, you can do this with a cron job (see "man cron").
For Redhat, a logrotate script has been included.

On SuSE Linux systems, you can place a line like "/var/log/privoxy.* +1024k 644
nobody.nogroup" in /etc/logfiles, with the effect that cron.daily will
automatically archive, gzip, and empty the log, when it exceeds 1M size.

Default: Log to the a file named logfile. Comment out to disable logging.

  logfile logfile
   

The "jarfile" defines where Privoxy stores the cookies it intercepts. Note that
if you use a "jarfile", it may grow quite large. Default: Don't store
intercepted cookies.

  #jarfile jarfile
   

If you specify a "trustfile", Privoxy will only allow access to sites that are
named in the trustfile. You can also mark sites as trusted referrers, with the
effect that access to untrusted sites will be granted, if a link from a trusted
referrer was used. The link target will then be added to the "trustfile". This
is a very restrictive feature that typical users most probably want to leave
disabled. Default: Disabled, don't use the trust mechanism.

  #trustfile trust
   

If you use the trust mechanism, it is a good idea to write up some on-line
documentation about your blocking policy and to specify the URL(s) here. They
will appear on the page that your users receive when they try to access
untrusted content. Use multiple times for multiple URLs. Default: Don't display
links on the "untrusted" info page.

  trust-info-url http://www.your-site.com/why_we_block.html
  trust-info-url http://www.your-site.com/what_we_allow.html
   

-------------------------------------------------------------------------------

3.3.2. Other Configuration Options

This part of the configuration file contains options that control how Privoxy
operates.

"Admin-address" should be set to the email address of the proxy administrator.
It is used in many of the proxy-generated pages. Default: fill@me.in.please.

  #admin-address fill@me.in.please
   

"Proxy-info-url" can be set to a URL that contains more info about this Privoxy
installation, it's configuration and policies. It is used in many of the
proxy-generated pages and its use is highly recommended in multi-user
installations, since your users will want to know why certain content is
blocked or modified. Default: Don't show a link to on-line documentation.

  proxy-info-url http://www.your-site.com/proxy.html
   

"Listen-address" specifies the address and port where Privoxy will listen for
connections from your Web browser. The default is to listen on the localhost
port 8118, and this is suitable for most users. (In your web browser, under
proxy configuration, list the proxy server as "localhost" and the port as
"8118").

If you already have another service running on port 8118, or if you want to
serve requests from other machines (e.g. on your local network) as well, you
will need to override the default. The syntax is "listen-address
[<ip-address>]:<port>". If you leave out the IP address, Privoxy will bind to
all interfaces (addresses) on your machine and may become reachable from the
Internet. In that case, consider using access control lists (acl's) (see
"aclfile" above), or a firewall.

For example, suppose you are running Privoxy on a machine which has the address
192.168.0.1 on your local private network (192.168.0.0) and has another outside
connection with a different address. You want it to serve requests from inside
only:

  listen-address 192.168.0.1:8118
   

If you want it to listen on all addresses (including the outside connection):

  listen-address :8118
   

If you do this, consider using ACLs (see "aclfile" above). Note: you will need
to point your browser(s) to the address and port that you have configured here.
Default: localhost:8118 (127.0.0.1:8118).

The debug option sets the level of debugging information to log in the logfile
(and to the console in the Windows version). A debug level of 1 is informative
because it will show you each request as it happens. Higher levels of debug are
probably only of interest to developers.

  debug         1 # GPC   = show each GET/POST/CONNECT request
  debug         2 # CONN  = show each connection status
  debug         4 # IO    = show I/O status
  debug         8 # HDR   = show header parsing
  debug        16 # LOG   = log all data into the logfile
  debug        32 # FRC   = debug force feature
  debug        64 # REF   = debug regular expression filter 
  debug       128 #       = debug fast redirects
  debug       256 #       = debug GIF de-animation
  debug       512 # CLF   = Common Log Format
  debug      1024 #       = debug kill pop-ups
  debug      4096 # INFO  = Startup banner and warnings.
  debug      8192 # ERROR = Non-fatal errors
    

It is highly recommended that you enable ERROR reporting (debug 8192), at least
until v3.0 is released.

The reporting of FATAL errors (i.e. ones which crash Privoxy) is always on and
cannot be disabled.

If you want to use CLF (Common Log Format), you should set "debug 512" ONLY, do
not enable anything else.

Multiple "debug" directives, are OK - they're logical-OR'd together.

  debug 15 # same as setting the first 4 listed above
   

Default:

  debug 1 # URLs
  debug 4096 # Info
  debug 8192 # Errors - *we highly recommended enabling this*
   

Privoxy normally uses "multi-threading", a software technique that permits it
to handle many different requests simultaneously. In some cases you may wish to
disable this -- particularly if you're trying to debug a problem. The
"single-threaded" option forces Privoxy to handle requests sequentially.
Default: Multi-threaded mode.

  #single-threaded
   

"toggle" allows you to temporarily disable all Privoxy's filtering. Just set
"toggle 0".

The Windows version of Privoxy puts an icon in the system tray, which also
allows you to change this option. If you right-click on that icon (or select
the "Options" menu), one choice is "Enable". Clicking on enable toggles Privoxy
on and off. This is useful if you want to temporarily disable Privoxy, e.g., to
access a site that requires cookies which you would otherwise have blocked.
This can also be toggled via a web browser at the Privoxy internal address of 
http://p.p on any platform.

"toggle 1" means Privoxy runs normally, "toggle 0" means that Privoxy becomes a
non-anonymizing non-blocking proxy. Default: 1 (on).

  toggle 1
   

For content filtering, i.e. the "+filter" and "+deanimate-gif" actions, it is
necessary that Privoxy buffers the entire document body. This can be
potentially dangerous, since a server could just keep sending data indefinitely
and wait for your RAM to exhaust. With nasty consequences.

The buffer-limit option lets you set the maximum size in Kbytes that each
buffer may use. When the documents buffer exceeds this size, it is flushed to
the client unfiltered and no further attempt to filter the rest of it is made.
Remember that there may multiple threads running, which might require
increasing the "buffer-limit" Kbytes each, unless you have enabled
"single-threaded" above.

  buffer-limit 4069
   

To enable the web-based default.action file editor set enable-edit-actions to
1, or 0 to disable. Note that you must have compiled Privoxy with support for
this feature, otherwise this option has no effect. This internal page can be
reached at http://p.p.

Security note: If this is enabled, anyone who can use the proxy can edit the
actions file, and their changes will affect all users. For shared proxies, you
probably want to disable this. Default: enabled.

  enable-edit-actions 1
   

Allow Privoxy to be toggled on and off remotely, using your web browser. Set
"enable-remote-toggle"to 1 to enable, and 0 to disable. Note that you must have
compiled Privoxy with support for this feature, otherwise this option has no
effect.

Security note: If this is enabled, anyone who can use the proxy can toggle it
on or off (see http://p.p), and their changes will affect all users. For shared
proxies, you probably want to disable this. Default: enabled.

  enable-remote-toggle 1
   

-------------------------------------------------------------------------------

3.3.3. Access Control List (ACL)

Access controls are included at the request of some ISPs and systems
administrators, and are not usually needed by individual users. Please note the
warnings in the FAQ that this proxy is not intended to be a substitute for a
firewall or to encourage anyone to defer addressing basic security weaknesses.

If no access settings are specified, the proxy talks to anyone that connects.
If any access settings file are specified, then the proxy talks only to IP
addresses permitted somewhere in this file and not denied later in this file.

Summary -- if using an ACL:

Client must have permission to receive service.

LAST match in ACL wins.

Default behavior is to deny service.

The syntax for an entry in the Access Control List is:

  ACTION    SRC_ADDR[/SRC_MASKLEN]    [ DST_ADDR[/DST_MASKLEN] ]
   

Where the individual fields are:

 ACTION      = "permit-access" or "deny-access"

 SRC_ADDR    = client hostname or dotted IP address
 SRC_MASKLEN = number of bits in the subnet mask for the source

 DST_ADDR    = server or forwarder hostname or dotted IP address
 DST_MASKLEN = number of bits in the subnet mask for the target
   

The field separator (FS) is whitespace (space or tab).

IMPORTANT NOTE: If Privoxy is using a forwarder (see below) or a gateway for a
particular destination URL, the DST_ADDR that is examined is the address of the
forwarder or the gateway and NOT the address of the ultimate target. This is
necessary because it may be impossible for the local Privoxy to determine the
address of the ultimate target (that's often what gateways are used for).

Here are a few examples to show how the ACL features work:

"localhost" is OK -- no DST_ADDR implies that ALL destination addresses are OK:

  permit-access localhost
   

A silly example to illustrate permitting any host on the class-C subnet with
Privoxy to go anywhere:

  permit-access www.privoxy.com/24
   

Except deny one particular IP address from using it at all:

  deny-access ident.privoxy.com
   

You can also specify an explicit network address and subnet mask. Explicit
addresses do not have to be resolved to be used.

  permit-access 207.153.200.0/24
   

A subnet mask of 0 matches anything, so the next line permits everyone.

  permit-access 0.0.0.0/0
   

Note, you cannot say:

  permit-access .org
   

to allow all *.org domains. Every IP address listed must resolve fully.

An ISP may want to provide a Privoxy that is accessible by "the world" and yet
restrict use of some of their private content to hosts on its internal network
(i.e. its own subscribers). Say, for instance the ISP owns the Class-B IP
address block 123.124.0.0 (a 16 bit netmask). This is how they could do it:

 permit-access 0.0.0.0/0 0.0.0.0/0   # other clients can go anywhere 
                                       # with the following exceptions:
 
 deny-access   0.0.0.0/0   123.124.0.0/16 # block all external requests for
                                          # sites on the ISP's network

 permit 0.0.0.0/0 www.my_isp.com        # except for the ISP's main 
                                          # web site

 permit 123.124.0.0/16 0.0.0.0/0          # the ISP's clients can go 
                                          # anywhere
   

Note that if some hostnames are listed with multiple IP addresses, the primary
value returned by DNS (via gethostbyname()) is used. Default: Anyone can access
the proxy.

-------------------------------------------------------------------------------

3.3.4. Forwarding

This feature allows chaining of HTTP requests via multiple proxies. It can be
used to better protect privacy and confidentiality when accessing specific
domains by routing requests to those domains to a special purpose filtering
proxy such as lpwa.com. Or to use a caching proxy to speed up browsing.

It can also be used in an environment with multiple networks to route requests
via multiple gateways allowing transparent access to multiple networks without
having to modify browser configurations.

Also specified here are SOCKS proxies. Privoxy SOCKS 4 and SOCKS 4A. The
difference is that SOCKS 4A will resolve the target hostname using DNS on the
SOCKS server, not our local DNS client.

The syntax of each line is:

 forward target_domain[:port] http_proxy_host[:port]
 forward-socks4 target_domain[:port] socks_proxy_host[:port] http_proxy_host[:
port]
 forward-socks4a target_domain[:port] socks_proxy_host[:port] http_proxy_host[:
port]
   

If http_proxy_host is ".", then requests are not forwarded to a HTTP proxy but
are made directly to the web servers.

Lines are checked in sequence, and the last match wins.

There is an implicit line equivalent to the following, which specifies that
anything not finding a match on the list is to go out without forwarding or
gateway protocol, like so:

  forward .* . # implicit
   

In the following common configuration, everything goes to Lucent's LPWA, except
SSL on port 443 (which it doesn't handle):

 forward .* lpwa.com:8000
 forward :443 .
   

Some users have reported difficulties related to LPWA's use of "." as the last
element of the domain, and have said that this can be fixed with this:

  forward lpwa. lpwa.com:8000
   

(NOTE: the syntax for specifying target_domain has changed since the previous
paragraph was written -- it will not work now. More information is welcome.)

In this fictitious example, everything goes via an ISP's caching proxy, except
requests to that ISP:

 forward .* caching.myisp.net:8000
 forward myisp.net .
   

For the @home network, we're told the forwarding configuration is this:

  forward .* proxy:8080
   

Also, we're told they insist on getting cookies and JavaScript, so you should
allow cookies from home.com. We consider JavaScript a potential security risk.
Java need not be enabled.

In this example direct connections are made to all "internal" domains, but
everything else goes through Lucent's LPWA by way of the company's SOCKS
gateway to the Internet.

 forward-socks4 .* lpwa.com:8000 firewall.my_company.com:1080
 forward my_company.com .
   

This is how you could set up a site that always uses SOCKS but no forwarders:

  forward-socks4a .* . firewall.my_company.com:1080
   

An advanced example for network administrators:

If you have links to multiple ISPs that provide various special content to
their subscribers, you can configure forwarding to pass requests to the
specific host that's connected to that ISP so that everybody can see all of the
content on all of the ISPs.

This is a bit tricky, but here's an example:

host-a has a PPP connection to isp-a.com. And host-b has a PPP connection to
isp-b.com. host-a can run a Privoxy proxy with forwarding like this:

 forward .* .
 forward isp-b.com host-b:8118
   

host-b can run a Privoxy proxy with forwarding like this:

 forward .* .
 forward isp-a.com host-a:8118
   

Now, anyone on the Internet (including users on host-a and host-b) can set
their browser's proxy to either host-a or host-b and be able to browse the
content on isp-a or isp-b.

Here's another practical example, for University of Kent at Canterbury students
with a network connection in their room, who need to use the University's Squid
web cache.

 forward *. ssbcache.ukc.ac.uk:3128  # Use the proxy, except for:
 forward .ukc.ac.uk .  # Anything on the same domain as us
 forward * .  # Host with no domain specified
 forward 129.12.*.* .  # A dotted IP on our /16 network.
 forward 127.*.*.* .  # Loopback address
 forward localhost.localdomain .  # Loopback address
 forward www.ukc.mirror.ac.uk .  # Specific host
   

If you intend to chain Privoxy and squid locally, then chain as browser ->
squid -> privoxy is the recommended way.

Your squid configuration could then look like this:

  # Define Privoxy as parent cache 
  
  cache_peer 127.0.0.1 parent 8118 0 no-query
  
  # Define ACL for protocol FTP 
  acl FTP proto FTP 

  # Do not forward ACL FTP to privoxy
  always_direct allow FTP 

  # Do not forward ACL CONNECT (https) to privoxy
  always_direct allow CONNECT 

  # Forward the rest to privoxy
  never_direct allow all 
   

-------------------------------------------------------------------------------

3.3.5. Windows GUI Options

Privoxy has a number of options specific to the Windows GUI interface:

If "activity-animation" is set to 1, the Privoxy icon will animate when
"Privoxy" is active. To turn off, set to 0.

  activity-animation 1
   

If "log-messages" is set to 1, Privoxy will log messages to the console window:

  log-messages 1
   

If "log-buffer-size" is set to 1, the size of the log buffer, i.e. the amount
of memory used for the log messages displayed in the console window, will be
limited to "log-max-lines" (see below).

Warning: Setting this to 0 will result in the buffer to grow infinitely and eat
up all your memory!

  log-buffer-size 1
   

log-max-lines is the maximum number of lines held in the log buffer. See above.

  log-max-lines 200
   

If "log-highlight-messages" is set to 1, Privoxy will highlight portions of the
log messages with a bold-faced font:

  log-highlight-messages 1
   

The font used in the console window:

  log-font-name Comic Sans MS
   

Font size used in the console window:

  log-font-size 8
   

"show-on-task-bar" controls whether or not Privoxy will appear as a button on
the Task bar when minimized:

  show-on-task-bar 0
   

If "close-button-minimizes" is set to 1, the Windows close button will minimize
Privoxy instead of closing the program (close with the exit option on the File
menu).

  close-button-minimizes 1
   

The "hide-console" option is specific to the MS-Win console version of Privoxy.
If this option is used, Privoxy will disconnect from and hide the command
console.

  #hide-console
   

-------------------------------------------------------------------------------

3.4. The Actions File

The "default.action" file (formerly actionsfile or ijb.action) is used to
define what actions Privoxy takes, and thus determines how images, cookies and
various other aspects of HTTP content and transactions are handled. Images can
be anything you want, including ads, banners, or just some obnoxious URL that
you would rather not see. Cookies can be accepted or rejected, or accepted only
during the current browser session (i.e. not written to disk). Changes to
default.action should be immediately visible to Privoxy without the need to
restart.

The easiest way to edit "actions" file is with a browser by loading http://p.p/
, and then select "Edit Actions List". A text editor can also be used.

To determine which actions apply to a request, the URL of the request is
compared to all patterns in this file. Every time it matches, the list of
applicable actions for the URL is incrementally updated. You can trace this
process by visiting http://p.p/show-url-info.

There are four types of lines in this file: comments (begin with a "#"
character), actions, aliases and patterns, all of which are explained below, as
well as the configuration file syntax that Privoxy understands. 

-------------------------------------------------------------------------------

3.4.1. URL Domain and Path Syntax

Generally, a pattern has the form <domain>/<path>, where both the <domain> and
<path> part are optional. If you only specify a domain part, the "/" can be
left out:

www.example.com - is a domain only pattern and will match any request to
"www.example.com".

www.example.com/ - means exactly the same.

www.example.com/index.html - matches only the single document "/index.html" on
"www.example.com".

/index.html - matches the document "/index.html", regardless of the domain.

index.html - matches nothing, since it would be interpreted as a domain name
and there is no top-level domain called ".html".

The matching of the domain part offers some flexible options: if the domain
starts or ends with a dot, it becomes unanchored at that end. For example:

.example.com - matches any domain that ENDS in ".example.com".

www. - matches any domain that STARTS with "www".

Additionally, there are wild-cards that you can use in the domain names
themselves. They work pretty similar to shell wild-cards: "*" stands for zero
or more arbitrary characters, "?" stands for any single character. And you can
define character classes in square brackets and they can be freely mixed:

ad*.example.com - matches "adserver.example.com", "ads.example.com", etc but
not "sfads.example.com".

*ad*.example.com - matches all of the above, and then some.

.?pix.com - matches "www.ipix.com", "pictures.epix.com", "a.b.c.d.e.upix.com",
etc.

www[1-9a-ez].example.com - matches "www1.example.com", "www4.example.com",
"wwwd.example.com", "wwwz.example.com", etc., but not "wwww.example.com".

If Privoxy was compiled with "pcre" support (default), Perl compatible regular
expressions can be used. See the pcre/docs/ directory or "man perlre" (also
available on http://www.perldoc.com/perl5.6/pod/perlre.html) for details. A
brief discussion of regular expressions is in the Appendix. For instance:

/.*/advert[0-9]+\.jpe?g - would match a URL from any domain, with any path that
includes "advert" followed immediately by one or more digits, then a "." and
ending in either "jpeg" or "jpg". So we match "example.com/ads/advert2.jpg",
and "www.example.com/ads/banners/advert39.jpeg", but not "www.example.com/ads/
banners/advert39.gif" (no gifs in the example pattern).

Please note that matching in the path is case INSENSITIVE by default, but you
can switch to case sensitive at any point in the pattern by using the "(?-i)"
switch:

www.example.com/(?-i)PaTtErN.* - will match only documents whose path starts
with "PaTtErN" in exactly this capitalization.

-------------------------------------------------------------------------------

3.4.2. Actions

Actions are enabled if preceded with a "+", and disabled if preceded with a
"-". Actions are invoked by enclosing the action name in curly braces (e.g.
{+some_action}), followed by a list of URLs to which the action applies. There
are three classes of actions:

  * Boolean (e.g. "+/-block"):
   
      {+name}        # enable this action
      {-name}        # disable this action
         
   
  * parameterized (e.g. "+/-hide-user-agent"):
   
      {+name{param}}  # enable action and set parameter to "param"
      {-name}         # disable action
         
   
  * Multi-value (e.g. "{+/-add-header{Name: value}}", "{+/-wafer{name=value}}
    "):
   
      {+name{param}}   # enable action and add parameter "param"
      {-name{param}}   # remove the parameter "param"
      {-name}          # disable this action totally
         
   
If nothing is specified in this file, no "actions" are taken. So in this case
Privoxy would just be a normal, non-blocking, non-anonymizing proxy. You must
specifically enable the privacy and blocking features you need (although the
provided default default.action file will give a good starting point).

Later defined actions always over-ride earlier ones. For multi-valued actions,
the actions are applied in the order they are specified.

The list of valid Privoxy "actions" are:

  * Add the specified HTTP header, which is not checked for validity. You may
    specify this many times to specify many different headers:
   
      +add-header{Name: value}
         
   
  * Block this URL totally. In a default installation, a "blocked" URL will
    result in bright red banner that says "BLOCKED", with a reason why it is
    being blocked.
   
      +block
         
   
  * De-animate all animated GIF images, i.e. reduce them to their last frame.
    This will also shrink the images considerably (in bytes, not pixels!). If
    the option "first" is given, the first frame of the animation is used as
    the replacement. If "last" is given, the last frame of the animation is
    used instead, which probably makes more sense for most banner animations,
    but also has the risk of not showing the entire last frame (if it is only a
    delta to an earlier frame).
   
      +deanimate-gifs{last}
      +deanimate-gifs{first}
         
   
  * "+downgrade" will downgrade HTTP/1.1 client requests to HTTP/1.0 and
    downgrade the responses as well. Use this action for servers that use HTTP/
    1.1 protocol features that Privoxy doesn't handle well yet. HTTP/1.1 is
    only partially implemented. Default is not to downgrade requests.
   
      +downgrade
         
   
  * Many sites, like yahoo.com, don't just link to other sites. Instead, they
    will link to some script on their own server, giving the destination as a
    parameter, which will then redirect you to the final target. URLs resulting
    from this scheme typically look like: http://some.place/some_script?http://
    some.where-else.
   
    Sometimes, there are even multiple consecutive redirects encoded in the
    URL. These redirections via scripts make your web browsing more traceable,
    since the server from which you follow such a link can see where you go to.
    Apart from that, valuable bandwidth and time is wasted, while your browser
    ask the server for one redirect after the other. Plus, it feeds the
    advertisers.
   
    The "+fast-redirects" option enables interception of these types of
    requests by Privoxy, who will cut off all but the last valid URL in the
    request and send a local redirect back to your browser without contacting
    the intermediate site(s).
   
      +fast-redirects
         
   
  * Apply the filters in the section_header section of the default.filter file
    to the site(s). default.filter sections are grouped according to like
    functionality.
   
     +filter{section_header}
         
   
    Filter sections that are pre-defined in the supplied default.filter
    include:
   
        html-annoyances: Get rid of particularly annoying HTML abuse.
       
        js-annoyances: Get rid of particularly annoying JavaScript abuse
       
        no-poups: Kill all popups in JS and HTML
       
        frameset-borders: Give frames a border
       
        webbugs: Squish WebBugs (1x1 invisible GIFs used for user tracking)
       
        no-refresh: Automatic refresh sucks on auto-dialup lines
       
        fun: Text replacements for subversive browsing fun!
       
        nimda: Remove (virus) Nimda code.
       
        banners-by-size: Kill banners by size
       
        crude-parental: Kill all web pages that contain the words "sex" or     
        "warez"                                                                
       
  * Block any existing X-Forwarded-for header, and do not add a new one:
   
      +hide-forwarded
         
   
  * If the browser sends a "From:" header containing your e-mail address, this
    either completely removes the header ("block"), or changes it to the
    specified e-mail address.
   
      +hide-from{block}
      +hide-from{spam@sittingduck.xqq}
         
   
  * Don't send the "Referer:" (sic) header to the web site. You can block it,
    forge a URL to the same server as the request (which is preferred because
    some sites will not send images otherwise) or set it to a constant string
    of your choice.
   
      +hide-referer{block}
      +hide-referer{forge}
      +hide-referer{http://nowhere.com}
         
   
  * Alternative spelling of "+hide-referer". It has the same parameters, and
    can be freely mixed with, "+hide-referer". ("referrer" is the correct
    English spelling, however the HTTP specification has a bug - it requires it
    to be spelled "referer".)
   
      +hide-referrer{...}
         
   
  * Change the "User-Agent:" header so web servers can't tell your browser
    type. Warning! This breaks many web sites. Specify the user-agent value you
    want. Example, pretend to be using Netscape on Linux:
   
      +hide-user-agent{Mozilla (X11; I; Linux 2.0.32 i586)}
         
   
  * Treat this URL as an image. This only matters if it's also "+block"ed, in
    which case a "blocked" image can be sent rather than a HTML page. See
    "+image-blocker{}" below for the control over what is actually sent. If you
    want invisible ads, they should be defined as images and blocked. And also,
    "image-blocker" should be set to "blank".
   
      +image
         
   
  * Decides what to do with URLs that end up tagged with "{+block +image}", e.g
    an advertizement. There are five options. "-image-blocker" will send a HTML
    "blocked" page, usually resulting in a "broken image" icon. "+image-blocker
    {blank}" will send a 1x1 transparent GIF image. And finally,
    "+image-blocker{http://xyz.com}" will send a HTTP temporary redirect to the
    specified image. This has the advantage of the icon being being cached by
    the browser, which will speed up the display. "+image-blocker{pattern}"
    will send a checkboard type pattern
   
      +image-blocker{blank}
      +image-blocker{pattern}
      +image-blocker{http://p.p/send-banner}
         
   
  * By default (i.e. in the absence of a "+limit-connect" action), Privoxy will
    only allow CONNECT requests to port 443, which is the standard port for
    https as a precaution.
   
    The CONNECT methods exists in HTTP to allow access to secure websites
    (https:// URLs) through proxies. It works very simply: the proxy connects
    to the server on the specified port, and then short-circuits its
    connections to the client and to the remote proxy. This can be a big
    security hole, since CONNECT-enabled proxies can be abused as TCP relays
    very easily.
   
    If you want to allow CONNECT for more ports than this, or want to forbid
    CONNECT altogether, you can specify a comma separated list of ports and
    port ranges (the latter using dashes, with the minimum defaulting to 0 and
    max to 65K):
   
      +limit-connect{443} # This is the default and need no be specified.
      +limit-connect{80,443} # Ports 80 and 443 are OK.
      +limit-connect{-3, 7, 20-100, 500-} # Port less than 3, 7, 20 to 100
       #and above 500 are OK.
         
   
  * "+no-compression" prevents the website from compressing the data. Some
    websites do this, which can be a problem for Privoxy, since "+filter",
    "+no-popup" and "+gif-deanimate" will not work on compressed data. This
    will slow down connections to those websites, though. Default is
    "nocompression" is turned on.
   
      +nocompression
         
   
  * If the website sets cookies, "no-cookies-keep" will make sure they are
    erased when you exit and restart your web browser. This makes profiling
    cookies useless, but won't break sites which require cookies so that you
    can log in for transactions. Default: on.
   
      +no-cookies-keep
         
   
  * Prevent the website from reading cookies:
   
      +no-cookies-read
         
   
  * Prevent the website from setting cookies:
   
      +no-cookies-set
         
   
  * Filter the website through a built-in filter to disable those obnoxious
    JavaScript pop-up windows via window.open(), etc. The two alternative
    spellings are equivalent.
   
      +no-popup
      +no-popups
         
   
  * This action only applies if you are using a jarfile for saving cookies. It
    sends a cookie to every site stating that you do not accept any copyright
    on cookies sent to you, and asking them not to track you. Of course, this
    is a (relatively) unique header they could use to track you.
   
      +vanilla-wafer
         
   
  * This allows you to add an arbitrary cookie. It can be specified multiple
    times in order to add as many cookies as you like.
   
      +wafer{name=value}
         
   
The meaning of any of the above is reversed by preceding the action with a "-",
in place of the "+".

Some examples:

Turn off cookies by default, then allow a few through for specified sites:

 # Turn off all persistent cookies
 { +no-cookies-read }
 { +no-cookies-set }
 # Allow cookies for this browser session ONLY
 { +no-cookies-keep }

 # Exceptions to the above, sites that benefit from persistent cookies
 { -no-cookies-read }
 { -no-cookies-set }
 { -no-cookies-keep }
 .javasoft.com
 .sun.com
 .yahoo.com
 .msdn.microsoft.com
 .redhat.com

 # Alternative way of saying the same thing
 {-no-cookies-set -no-cookies-read -no-cookies-keep}
 .sourceforge.net
 .sf.net
   

Now turn off "fast redirects", and then we allow two exceptions:

 # Turn them off!
 {+fast-redirects}
 
 # Reverse it for these two sites, which don't work right without it.
 {-fast-redirects}
 www.ukc.ac.uk/cgi-bin/wac\.cgi\?
 login.yahoo.com
   

Turn on page filtering according to rules in the defined sections of
refilterfile, and make one exception for sourceforge:

 # Run everything through the filter file, using only the
 # specified sections:
 +filter{html-annoyances} +filter{js-annoyances} +filter{no-popups}\
 +filter{webbugs} +filter{nimda} +filter{banners-by-size}
              
 # Then disable filtering of code from sourceforge!
 {-filter}
 .cvs.sourceforge.net
   

Now some URLs that we want "blocked", ie we won't see them. Many of these use
regular expressions that will expand to match multiple URLs:

  # Blocklist:
  {+block}
  /.*/(.*[-_.])?ads?[0-9]?(/|[-_.].*|\.(gif|jpe?g))
  /.*/(.*[-_.])?count(er)?(\.cgi|\.dll|\.exe|[?/])
  /.*/(ng)?adclient\.cgi
  /.*/(plain|live|rotate)[-_.]?ads?/
  /.*/(sponsor)s?[0-9]?/
  /.*/_?(plain|live)?ads?(-banners)?/
  /.*/abanners/
  /.*/ad(sdna_image|gifs?)/
  /.*/ad(server|stream|juggler)\.(cgi|pl|dll|exe)
  /.*/adbanners/
  /.*/adserver
  /.*/adstream\.cgi
  /.*/adv((er)?ts?|ertis(ing|ements?))?/
  /.*/banner_?ads/
  /.*/banners?/
  /.*/banners?\.cgi/
  /.*/cgi-bin/centralad/getimage
  /.*/images/addver\.gif
  /.*/images/marketing/.*\.(gif|jpe?g)
  /.*/popupads/
  /.*/siteads/
  /.*/sponsor.*\.gif
  /.*/sponsors?[0-9]?/
  /.*/advert[0-9]+\.jpg
  /Media/Images/Adds/
  /ad_images/
  /adimages/
  /.*/ads/
  /bannerfarm/
  /grafikk/annonse/
  /graphics/defaultAd/
  /image\.ng/AdType
  /image\.ng/transactionID
  /images/.*/.*_anim\.gif # alvin brattli
  /ip_img/.*\.(gif|jpe?g)
  /rotateads/
  /rotations/ 
  /worldnet/ad\.cgi
  /cgi-bin/nph-adclick.exe/
  /.*/Image/BannerAdvertising/
  /.*/ad-bin/
  /.*/adlib/server\.cgi
  /autoads/
   

Note that many of these actions have the potential to cause a page to
misbehave, possibly even not to display at all. There are many ways a site
designer may choose to design his site, and what HTTP header content he may
depend on. There is no way to have hard and fast rules for all sites. See the 
Appendix for a brief example on troubleshooting actions. 

-------------------------------------------------------------------------------

3.4.3. Aliases

Custom "actions", known to Privoxy as "aliases", can be defined by combining
other "actions". These can in turn be invoked just like the built-in "actions".
Currently, an alias can contain any character except space, tab, "=", "{" or "}
". But please use only "a"- "z", "0"-"9", "+", and "-". Alias names are not
case sensitive, and must be defined before anything else in the
default.actionfile ! And there can only be one set of "aliases" defined.

Now let's define a few aliases:

 # Useful customer aliases we can use later. These must come first!
 {{alias}}
 +no-cookies = +no-cookies-set +no-cookies-read
 -no-cookies = -no-cookies-set -no-cookies-read
 fragile     =
 -block -no-cookies -filter -fast-redirects -hide-referer -no-popups
 shop        = -no-cookies -filter -fast-redirects
 +imageblock = +block +image

 #For people who don't like to type too much:  ;-)
 c0 = +no-cookies
 c1 = -no-cookies
 c2 = -no-cookies-set +no-cookies-read
 c3 = +no-cookies-set -no-cookies-read
 #... etc.  Customize to your heart's content.
   

Some examples using our "shop" and "fragile" aliases from above:

 # These sites are very complex and require
 # minimal interference.
 {fragile}
 .office.microsoft.com
 .windowsupdate.microsoft.com
 .nytimes.com

 # Shopping sites - still want to block ads.
 {shop}
 .quietpc.com
 .worldpay.com   # for quietpc.com
 .jungle.com
 .scan.co.uk

 # These shops require pop-ups
 {shop -no-popups}
 .dabs.com
 .overclockers.co.uk
   

-------------------------------------------------------------------------------

3.5. The Filter File

Any web page can be dynamically modified with the filter file. This
modification can be removal, or re-writing, of any web page content, including
tags and non-visible content. The default filter file is default.filter,
located in the config directory.

The included example file is divided into sections. Each section begins with
the FILTER keyword, followed by the identifier for that section, e.g. "FILTER:
webbugs". Each section performs a similar type of filtering, such as
"html-annoyances". 

This file uses regular expressions to alter or remove any string in the target
page. The expressions can only operate on one line at a time. Some examples
from the included default default.filter:

Stop web pages from displaying annoying messages in the status bar by deleting
such references:

 FILTER: html-annoyances

 # New browser windows should be resizeable and have a location and status
 # bar. Make it so.
 #
 s/resizable="?(no|0)"?/resizable=1/ig s/noresize/yesresize/ig
 s/location="?(no|0)"?/location=1/ig s/status="?(no|0)"?/status=1/ig
 s/scrolling="?(no|0|Auto)"?/scrolling=1/ig
 s/menubar="?(no|0)"?/menubar=1/ig 

 # The <BLINK> tag was a crime!
 #
 s*<blink>|</blink>**ig

 # Is this evil? 
 #
 #s/framespacing="?(no|0)"?//ig
 #s/margin(height|width)=[0-9]*//gi
   

Just for kicks, replace any occurrence of "Microsoft" with "MicroSuck", and
have a little fun with topical buzzwords:

 FILTER: fun

 s/microsoft(?!.com)/MicroSuck/ig

 # Buzzword Bingo:
 #
 s/industry-leading|cutting-edge|award-winning/<font color=red><b>BINGO!</b></
font>/ig
   

Kill those pesky little web-bugs:

 # webbugs: Squish WebBugs (1x1 invisible GIFs used for user tracking)
 FILTER: webbugs

 s/<img\s+[^>]*?(width|height)\s*=\s*['"]?1\D[^>]*?(width|height)\s*=\s*['"]?1
(\D[^>]*?)?>/<!-- Squished WebBug -->/sig
   

-------------------------------------------------------------------------------

3.6. Templates

When Privoxy displays one of its internal pages, such as a 404 Not Found error
page, it uses the appropriate template. On Linux, BSD, and Unix, these are
located in /etc/privoxy/templates by default. These may be customized, if
desired. 

-------------------------------------------------------------------------------

4. Quickstart to Using Privoxy

Install package, then run and enjoy! Privoxy is typically started by specifying
the main configuration file to be used on the command line. Example Unix
startup command:

                                                                               
 # /usr/sbin/privoxy /etc/privoxy/config                                       
                                                                               
                                                                               

An init script is provided for SuSE and Redhat.

For for SuSE: /etc/rc.d/privoxy start

For RedHat: /etc/rc.d/init.d/privoxy start

If no configuration file is specified on the command line, Privoxy will look
for a file named config in the current directory. Except on Win32 where it will
try config.txt. If no file is specified on the command line and no default
configuration file can be found, Privoxy will fail to start.

Be sure your browser is set to use the proxy which is by default at localhost,
port 8118. With Netscape (and Mozilla), this can be set under Edit ->
Preferences -> Advanced -> Proxies -> HTTP Proxy. For Internet Explorer: Tools
> Internet Properties -> Connections -> LAN Setting. Then, check "Use Proxy"
and fill in the appropriate info (Address: localhost, Port: 8118). Include if
HTTPS proxy support too.

The included default configuration files should give a reasonable starting
point, though may be somewhat aggressive in blocking junk. You will probably
want to keep an eye out for sites that require persistent cookies, and add
these to default.action as needed. By default, most of these will be accepted
only during the current browser session, until you add them to the
configuration. If you want the browser to handle this instead, you will need to
edit default.action and disable this feature. If you use more than one browser,
it would make more sense to let Privoxy handle this. In which case, the browser
(s) should be set to accept all cookies.

If a particular site shows problems loading properly, try adding it to the
{fragile} section of default.action. This will turn off most actions for this
site.

Privoxy is HTTP/1.1 compliant, but not all 1.1 features are as yet implemented.
If browsers that support HTTP/1.1 (like Mozilla or recent versions of I.E.)
experience problems, you might try to force HTTP/1.0 compatibility. For
Mozilla, look under Edit -> Preferences -> Debug -> Networking. Or set the
"+downgrade" config option in default.action.

After running Privoxy for a while, you can start to fine tune the configuration
to suit your personal, or site, preferences and requirements. There are many,
many aspects that can be customized. "Actions" (as specified in default.action)
can be adjusted by pointing your browser to http://p.p/, and then follow the
link to "edit the actions list". (This is an internal page and does not require
Internet access.)

In fact, various aspects of Privoxy configuration can be viewed from this page,
including current configuration parameters, source code version numbers, the
browser's request headers, and "actions" that apply to a given URL. In addition
to the default.action file editor mentioned above, Privoxy can also be turned
"on" and "off" from this page.

If you encounter problems, please verify it is a Privoxy bug, by disabling
Privoxy, and then trying the same page. Also, try another browser if possible
to eliminate browser or site problems. Before reporting it as a bug, see if
there is not a configuration option that is enabled that is causing the page
not to load. You can then add an exception for that page or site. If a bug,
please report it to the developers (see below).

-------------------------------------------------------------------------------

4.1. Command Line Options

Privoxy may be invoked with the following command-line options:

  * --version
   
    Print version info and exit, Unix only.
   
  * --help
   
    Print a short usage info and exit, Unix only.
   
  * --no-daemon
   
    Don't become a daemon, i.e. don't fork and become process group leader,
    don't detach from controlling tty. Unix only.
   
  * --pidfile FILE
   
    On startup, write the process ID to FILE. Delete the FILE on exit. Failiure
    to create or delete the FILE is non-fatal. If no FILE option is given, no
    PID file will be used. Unix only.
   
  * --user USER[.GROUP]
   
    After (optionally) writing the PID file, assume the user ID of USER, and if
    included the GID of GROUP. Exit if the privileges are not sufficient to do
    so. Unix only.
   
  * configfile
   
    If no configfile is included on the command line, Privoxy will look for a
    file named "config" in the current directory (except on Win32 where it will
    look for "config.txt" instead). Specify full path to avoid confusion.
   
-------------------------------------------------------------------------------

5. Contacting the Developers, Bug Reporting and Feature Requests

We value your feedback. However, to provide you with the best support, please
note:

  * Use the Sourceforge support forum to get help.
   
  * Submit bugs only thru our Sourceforge bug forum. Make sure that the bug has
    not already been submitted. Please try to verify that it is a Privoxy bug,
    and not a browser or site bug first. If you are using your own custom
    configuration, please try the stock configs to see if the problem is a
    configuration related bug. And if not using the latest development
    snapshot, please try the latest one. Or even better, CVS sources.
   
  * Submit feature requests only thru our Sourceforge feature request forum.
   
 

For any other issues, feel free to use the mailing lists.

Anyone interested in actively participating in development and related
discussions can join the appropriate mailing list here. Archives are available
here too.

-------------------------------------------------------------------------------

6. Copyright and History

6.1. License

Privoxy is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details, which
is available from the Free Software Foundation, Inc, 59 Temple Place - Suite
330, Boston, MA 02111-1307, USA.

-------------------------------------------------------------------------------

6.2. History

Privoxy is evolved, and derived from, the Internet Junkbuster, with many
improvments and enhancements over the original.

Junkbuster was originally written by Anonymous Coders and Junkbuster's
Corporation, and was released as free open-source software under the GNU GPL. 
Stefan Waldherr made many improvements, and started the SourceForge project
Privoxy to rekindle development. There are now several active developers
contributing. The last stable release of Junkbuster was v2.0.2, which has now
grown whiskers ;-).

-------------------------------------------------------------------------------

7. See also

  http://sourceforge.net/projects/ijbswa, the Project Page for Privoxy.

  http://www.privoxy.org/

  http://p.p/

  http://www.junkbusters.com/ht/en/cookies.html

  http://www.waldherr.org/junkbuster/

  http://privacy.net/analyze/

 http://www.squid-cache.org/

 

-------------------------------------------------------------------------------

8. Appendix

8.1. Regular Expressions

Privoxy can use "regular expressions" in various config files. Assuming support
for "pcre" (Perl Compatible Regular Expressions) is compiled in, which is the
default. Such configuration directives do not require regular expressions, but
they can be used to increase flexibility by matching a pattern with wild-cards
against URLs.

If you are reading this, you probably don't understand what "regular
expressions" are, or what they can do. So this will be a very brief
introduction only. A full explanation would require a book ;-)

"Regular expressions" is a way of matching one character expression against
another to see if it matches or not. One of the "expressions" is a literal
string of readable characters (letter, numbers, etc), and the other is a
complex string of literal characters combined with wild-cards, and other
special characters, called meta-characters. The "meta-characters" have special
meanings and are used to build the complex pattern to be matched against. Perl
Compatible Regular Expressions is an enhanced form of the regular expression
language with backward compatibility.

To make a simple analogy, we do something similar when we use wild-card
characters when listing files with the dir command in DOS. *.* matches all
filenames. The "special" character here is the asterisk which matches any and
all characters. We can be more specific and use ? to match just individual
characters. So "dir file?.text" would match "file1.txt", "file2.txt", etc. We
are pattern matching, using a similar technique to "regular expressions"!

Regular expressions do essentially the same thing, but are much, much more
powerful. There are many more "special characters" and ways of building complex
patterns however. Let's look at a few of the common ones, and then some
examples:

. - Matches any single character, e.g. "a", "A", "4", ":", or "@".

? - The preceding character or expression is matched ZERO or ONE times. Either/
or.                                                                            

+ - The preceding character or expression is matched ONE or MORE times.

* - The preceding character or expression is matched ZERO or MORE times.

\ - The "escape" character denotes that the following character should be taken
literally. This is used where one of the special characters (e.g. ".") needs to
be taken literally and not as a special meta-character.                        

[] - Characters enclosed in brackets will be matched if any of the enclosed    
characters are encountered.                                                    

() - parentheses are used to group a sub-expression, or multiple               
sub-expressions.                                                               

| - The "bar" character works like an "or" conditional statement. A match is   
successful if the sub-expression on either side of "|" matches.                

s/string1/string2/g - This is used to rewrite strings of text. "string1" is    
replaced by "string2" in this example.                                         

These are just some of the ones you are likely to use when matching URLs with
Privoxy, and is a long way from a definitive list. This is enough to get us
started with a few simple examples which may be more illuminating:

/.*/banners/.* - A simple example that uses the common combination of "." and "
*" to denote any character, zero or more times. In other words, any string at
all. So we start with a literal forward slash, then our regular expression
pattern (".*") another literal forward slash, the string "banners", another
forward slash, and lastly another ".*". We are building a directory path here.
This will match any file with the path that has a directory named "banners" in
it. The ".*" matches any characters, and this could conceivably be more forward
slashes, so it might expand into a much longer looking path. For example, this
could match: "/eye/hate/spammers/banners/annoy_me_please.gif", or just "/
banners/annoying.html", or almost an infinite number of other possible
combinations, just so it has "banners" in the path somewhere.

A now something a little more complex:

/.*/adv((er)?ts?|ertis(ing|ements?))?/ - We have several literal forward
slashes again ("/"), so we are building another expression that is a file path
statement. We have another ".*", so we are matching against any conceivable
sub-path, just so it matches our expression. The only true literal that must
match our pattern is adv, together with the forward slashes. What comes after
the "adv" string is the interesting part.

Remember the "?" means the preceding expression (either a literal character or
anything grouped with "(...)" in this case) can exist or not, since this means
either zero or one match. So "((er)?ts?|ertis(ing|ements?))" is optional, as
are the individual sub-expressions: "(er)", "(ing|ements?)", and the "s". The "
|" means "or". We have two of those. For instance, "(ing|ements?)", can expand
to match either "ing" OR "ements?". What is being done here, is an attempt at
matching as many variations of "advertisement", and similar, as possible. So
this would expand to match just "adv", or "advert", or "adverts", or
"advertising", or "advertisement", or "advertisements". You get the idea. But
it would not match "advertizements" (with a "z"). We could fix that by changing
our regular expression to: "/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/", which
would then match either spelling.

/.*/advert[0-9]+\.(gif|jpe?g) - Again another path statement with forward
slashes. Anything in the square brackets "[]" can be matched. This is using
"0-9" as a shorthand expression to mean any digit one through nine. It is the
same as saying "0123456789". So any digit matches. The "+" means one or more of
the preceding expression must be included. The preceding expression here is
what is in the square brackets -- in this case, any digit one through nine.
Then, at the end, we have a grouping: "(gif|jpe?g)". This includes a "|", so
this needs to match the expression on either side of that bar character also. A
simple "gif" on one side, and the other side will in turn match either "jpeg"
or "jpg", since the "?" means the letter "e" is optional and can be matched
once or not at all. So we are building an expression here to match image GIF or
JPEG type image file. It must include the literal string "advert", then one or
more digits, and a "." (which is now a literal, and not a special character,
since it is escaped with "\"), and lastly either "gif", or "jpeg", or "jpg".
Some possible matches would include: "//advert1.jpg", "/nasty/ads/
advert1234.gif", "/banners/from/hell/advert99.jpg". It would not match
"advert1.gif" (no leading slash), or "/adverts232.jpg" (the expression does not
include an "s"), or "/advert1.jsp" ("jsp" is not in the expression anywhere).

s/microsoft(?!.com)/MicroSuck/i - This is a substitution. "MicroSuck" will
replace any occurrence of "microsoft". The "i" at the end of the expression
means ignore case. The "(?!.com)" means the match should fail if "microsoft" is
followed by ".com". In other words, this acts like a "NOT" modifier. In case
this is a hyperlink, we don't want to break it ;-).

We are barely scratching the surface of regular expressions here so that you
can understand the default Privoxy configuration files, and maybe use this
knowledge to customize your own installation. There is much, much more that can
be done with regular expressions. Now that you know enough to get started, you
can learn more on your own :/

More reading on Perl Compatible Regular expressions: http://www.perldoc.com/
perl5.6/pod/perlre.html

-------------------------------------------------------------------------------

8.2. Privoxy's Internal Pages

Since Privoxy proxies each requested web page, it is easy for Privoxy to trap
certain URLs. In this way, we can talk directly to Privoxy, and see how it is
configured, see how our rules are being applied, change these rules and other
configuration options, and even turn Privoxy's filtering off, all with a web
browser. 

The URLs listed below are the special ones that allow direct access to Privoxy.
Of course, Privoxy must be running to access these. If not, you will get a
friendly error message. Internet access is not necessary either.

  * Privoxy main page:
   
        http://www.privoxy.org/config/
       
    Alternately, this may be reached at http://p.p/, but this variation may not
    work as reliably as the above in some configurations.
   
  * Show information about the current configuration:
   
        http://www.privoxy.org/config/show-status
       
  * Show the source code version numbers:
   
        http://www.privoxy.org/config/show-version
       
  * Show the client's request headers:
   
        http://www.privoxy.org/config/show-request
       
  * Show which actions apply to a URL and why:
   
        http://www.privoxy.org/config/show-url-info
       
  * Toggle Privoxy on or off:
   
        http://www.privoxy.org/config/toggle
       
    Short cuts. Turn off, then on:
   
        http://www.privoxy.org/config/toggle?set=disable
       
        http://www.privoxy.org/config/toggle?set=enable
       
  * Edit the actions list file:
   
        http://www.privoxy.org/config/edit-actions
       
These may be bookmarked for quick reference. 

-------------------------------------------------------------------------------

8.3. Anatomy of an Action

The way Privoxy applies "actions" to any given URL can be complex, and not
always so easy to understand what is happening. And sometimes we need to be
able to see just what Privoxy is doing. Especially, if something Privoxy is
doing is causing us a problem inadvertantly. It can be a little daunting to
look at the actions files themselves, since they tend to be filled with
"regular expressions" whose consequences are not always so obvious. Privoxy
provides the http://www.privoxy.org/config/show-url-info page that can show us
very specifically how actions are being applied to any given URL. This is a big
help for troubleshooting.

First, enter one URL (or partial URL) at the prompt, and then Privoxy will tell
us how the current configuration will handle it. This will not help with
filtering effects from the default.filter file! It also will not tell you about
any other URLs that may be embedded within the URL you are testing. For
instance, images such as ads are expressed as URLs within the raw page source
of HTML pages. So you will only get info for the actual URL that is pasted into
the prompt area -- not any sub-URLs. If you want to know about embedded URLs
like ads, you will have to dig those out of the HTML source. Use your browser's
"View Page Source" option for this.

Let's look at an example, google.com, one section at a time:

 System default actions:                                                       
                                                                               
 { -add-header -block -deanimate-gifs -downgrade -fast-redirects -filter       
   -hide-forwarded -hide-from -hide-referer -hide-user-agent -image            
   -image-blocker -limit-connect -no-compression -no-cookies-keep              
   -no-cookies-read -no-cookies-set -no-popups -vanilla-wafer -wafer }         
                                                                               
                                                                               

This is the top section, and only tells us of the compiled in defaults. This is
basically what Privoxy would do if there were not any "actions" defined, i.e.
it does nothing. Every action is disabled. This is not particularly informative
for our purposes here. OK, next section:

 Matches for http://google.com:                                                
                                                                               
 { -add-header -block +deanimate-gifs -downgrade +fast-redirects               
   +filter{html-annoyances} +filter{js-annoyances} +filter{no-popups}          
   +filter{webbugs} +filter{nimda} +filter{banners-by-size} +filter{hal}       
   +filter{fun} +hide-forwarded +hide-from{block} +hide-referer{forge}         
   -hide-user-agent -image +image-blocker{blank} +no-compression               
   +no-cookies-keep -no-cookies-read -no-cookies-set +no-popups                
   -vanilla-wafer -wafer }                                                     
   /                                                                           
                                                                               
 { -no-cookies-keep -no-cookies-read -no-cookies-set }                         
  .google.com                                                                  
                                                                               
 { -fast-redirects }                                                           
  .google.com                                                                  
                                                                               
                                                                               

This is much more informative, and tells us how we have defined our "actions",
and which ones match for our example, "google.com". The first grouping shows
our default settings, which would apply to all URLs. If you look at your
"actions" file, this would be the section just below the "aliases" section near
the top. This applies to all URLs as signified by the single forward slash -- "
/".

These are the default actions we have enabled. But we can define additional
actions that would be exceptions to these general rules, and then list specific
URLs that these exceptions would apply to. Last match wins. Just below this
then are two explict matches for ".google.com". The first is negating our
various cookie blocking actions (i.e. we will allow cookies here). The second
is allowing "fast-redirects". Note that there is a leading dot here --
".google.com". This will match any hosts and sub-domains, in the google.com
domain also, such as "www.google.com". So, apparently, we have these actions
defined somewhere in the lower part of our actions file, and "google.com" is
referenced in these sections. 

And now we pull it altogether in the bottom section and summarize how Privoxy
is appying all its "actions" to "google.com": 

 Final results:                                                                
                                                                               
 -add-header -block -deanimate-gifs -downgrade -fast-redirects                 
 +filter{html-annoyances} +filter{js-annoyances} +filter{no-popups}            
 +filter{webbugs} +filter{nimda} +filter{banners-by-size} +filter{hal}         
 +filter{fun} +hide-forwarded +hide-from{block} +hide-referer{forge}           
 -hide-user-agent -image +image-blocker{blank} -limit-connect +no-compression  
 -no-cookies-keep -no-cookies-read -no-cookies-set +no-popups -vanilla-wafer   
 -wafer                                                                        
                                                                               
                                                                               

Now another example, "ad.doubleclick.net":

 { +block +image }                                                             
  .ad.doubleclick.net                                                          
                                                                               
 { +block +image }                                                             
  ad*.                                                                         
                                                                               
 { +block +image }                                                             
  .doubleclick.net                                                             
                                                                               
                                                                               

We'll just show the interesting part here, the explicit matches. It is matched
three different times. Each as an "+block +image", which is the expanded form
of one of our aliases that had been defined as: "+imageblock". ("Aliases" are
defined in the first section of the actions file and typically used to combine
more than one action.)

Any one of these would have done the trick and blocked this as an unwanted
image. This is unnecessarily redundant since the last case effectively would
also cover the first. No point in taking chances with these guys though ;-)
Note that if you want an ad or obnoxious URL to be invisible, it should be
defined as "ad.doubleclick.net" is done here -- as both a "+block" and an
"+image". The custom alias "+imageblock" does this for us.

One last example. Let's try "http://www.rhapsodyk.net/adsl/HOWTO/". This one is
giving us problems. We are getting a blank page. Hmmm...

 Matches for http://www.rhapsodyk.net/adsl/HOWTO/:                             
                                                                               
 { -add-header -block +deanimate-gifs -downgrade +fast-redirects               
   +filter{html-annoyances} +filter{js-annoyances} +filter{no-popups}          
   +filter{webbugs} +filter{nimda} +filter{banners-by-size} +filter{hal}       
   +filter{fun} +hide-forwarded +hide-from{block} +hide-referer{forge}         
   -hide-user-agent -image +image-blocker{blank} +no-compression               
   +no-cookies-keep -no-cookies-read -no-cookies-set +no-popups                
   -vanilla-wafer -wafer }                                                     
   /                                                                           
                                                                               
 { +block +image }                                                             
  /ads                                                                         
                                                                               
                                                                               

Ooops, the "/adsl/" is matching "/ads"! But we did not want this at all! Now we
see why we get the blank page. We could now add a new action below this that
explictly does not block (-block) pages with "adsl". There are various ways to
handle such exceptions. Example:

 { -block }                                                                    
  /adsl                                                                        
                                                                               
                                                                               

Now the page displays ;-) 

But now what about a situation where we get no explicit matches like we did
with: 

 { -block }                                                                    
  /adsl                                                                        
                                                                               
                                                                               

That actually was very telling and pointed us quickly to where the problem was.
If you don't get this kind of match, then it means one of the default rules in
the first section is causing the problem. This would require some guesswork,
and maybe a little trial and error to isolate the offending rule. One likely
cause would be one of the "{+filter}" actions. Try adding the URL for the site
to one of aliases that turn off "+filter":

 {shop}                                                                        
 .quietpc.com                                                                  
 .worldpay.com   # for quietpc.com                                             
 .jungle.com                                                                   
 .scan.co.uk                                                                   
 .forbes.com                                                                   
                                                                               
                                                                               

"{shop}" is an "alias" that expands to "{ -filter -no-cookies -no-cookies-keep
}". Or you could do your own exception to negate filtering: 

 {-filter}                                                                     
 .forbes.com