This file belongs into
ijbswa.sourceforge.net:/home/groups/i/ij/ijbswa/htdocs/
- $Id: user-manual.sgml,v 1.123.2.43 2005/05/23 09:59:10 hal9 Exp $
+ $Id: user-manual.sgml,v 2.11 2006/07/18 14:48:51 david__schmidt Exp $
Copyright (C) 2001- 2003 Privoxy Developers <developers@privoxy.org>
See LICENSE.
</subscript>
</pubdate>
-<pubdate>$Id: user-manual.sgml,v 1.123.2.43 2005/05/23 09:59:10 hal9 Exp $</pubdate>
+<pubdate>$Id: user-manual.sgml,v 2.11 2006/07/18 14:48:51 david__schmidt Exp $</pubdate>
<!--
</variablelist>
</sect3>
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="content-type-overwrite">
+<title>content-type-overwrite</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Stop useless download menus from popping up, or change the browser's rendering mode</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Replaces the <quote>Content-Type:</quote> HTTP server header.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ The <quote>Content-Type:</quote> HTTP server header is used by the
+ browser to decide what to do with the document. The value of this
+ header can cause the browser to open a download menu instead of
+ displaying the document by itself, even if the document's format is
+ supported by the browser.
+ </para>
+ <para>
+ The declared content type can also affect which rendering mode
+ the browser chooses. If XHTML is delivered as <quote>text/html</quote>,
+ many browsers treat it as yet another broken HTML document.
+ If it is send as <quote>application/xml</quote>, browsers with
+ XHTML support will only display it, if the syntax is correct.
+ </para>
+ <para>
+ If you see a web site that proudly uses XHTML buttons, but sets
+ <quote>Content-Type: text/html</quote>, you can use Privoxy
+ to overwrite it with <quote>application/xml</quote> and validate
+ the web master's claim inside your XHTML-supporting browser.
+ If the syntax is incorrect, the browser will complain loudly.
+ </para>
+ <para>
+ You can also go the opposite direction: if your browser prints
+ error messages instead of rendering a document falsely declared
+ as XHTML, you can overwrite the content type with
+ <quote>text/html</quote> and have it rendered as broken HTML document.
+ </para>
+ <para>
+ By default <literal>content-type-overwrite</literal> only replaces
+ <quote>Content-Type:</quote> headers that look like some kind of text.
+ If you want to overwrite it unconditionally, you have to combine it with
+ <literal><link linkend="force-text-mode">force-text-mode</link></literal>.
+ This limitation exists for a reason, think twice before circumventing it.
+ </para>
+ <para>
+ Most of the time it's easier to enable
+ <literal><link linkend="filter-server-headers">filter-server-headers</link></literal>
+ and replace this action with a custom regular expression. It allows you
+ to activate it for every document of a certain site and it will still
+ only replace the content types you aimed at.
+ </para>
+ <para>
+ Of course you can apply <literal>content-type-overwrite</literal>
+ to a whole site and then make URL based exceptions, but it's a lot
+ more work to get the same precision.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (sections):</term>
+ <listitem>
+ <para>
+ <screen># Check if www.example.net/ really uses valid XHTML
+{+content-type-overwrite {application/xml}}
+www.example.net/
+# but leave the content type unmodified if the URL looks like a style sheet
+{-content-type-overwrite}
+www.example.net/*.\.css$
+www.example.net/*.style
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="crunch-client-header">
+<title>crunch-server-header</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Remove a client header <application>Privoxy</application> has no dedicated action for.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes every header send by the client that contains the string the user supplied as parameter.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This action allows you to block client headers for which no dedicated
+ <application>Privoxy</application> action exists.
+ <application>Privoxy</application> will remove every client header that
+ contains the string you supplied as parameter.
+ </para>
+ <para>
+ Regular expressions are <emphasis>not supported</emphasis> and you can't
+ use this action to block different headers in the same request, unless
+ they contain the same string.
+ </para>
+ <para>
+ <literal>crunch-client-header</literal> is only meant for quick tests.
+ If you have to block several different headers, or only want to modify
+ parts of them, you should enable
+ <literal><link linkend="filter-client-headers">filter-client-headers</link></literal>
+ and create your own filter.
+ </para>
+ <para>
+ <warning>
+ Don't block any header without understanding the consequences.
+ </warning>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Block the non-existent "Privacy-Violation:" client header
+{+crunch-client-header {Privacy-Violation:}}
+/
+ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="crunch-if-none-match">
+<title>crunch-if-none-match</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent yet another way to track the user's steps between sessions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>If-None-Match:</quote> HTTP client header.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Removing the <quote>If-None-Match:</quote> HTTP client header
+ is useful for filter testing, where you want to force a real
+ reload instead of getting status code <quote>304</quote> which
+ would cause the browser to use a cached copy of the page.
+ </para>
+ <para>
+ It is also useful to make sure the header isn't used as a cookie
+ replacement.
+ </para>
+ <para>
+ Blocking the <quote>If-None-Match:</quote> header shouldn't cause any
+ caching problems, as long as the <quote>If-Modified-Since:</quote> header
+ isn't blocked as well.
+ </para>
+ <para>
+ It is recommended to use this action together with
+ <literal><link linkend="hide-if-modified-since">hide-if-modified-since</link></literal>
+ and
+ <literal><link linkend="overwrite-last-modified">overwrite-last-modified</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Let the browser revalidate cached documents without being tracked across sessions
+{+hide-if-modified-since {-1} \
++overwrite-last-modified {randomize} \
++crunch-if-none-match}
+/ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
<!-- ~~~~~ New section ~~~~~ -->
<sect3 renderas="sect4" id="crunch-incoming-cookies">
<title>crunch-incoming-cookies</title>
</sect3>
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="crunch-server-header">
+<title>crunch-server-header</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Remove a server header <application>Privoxy</application> has no dedicated action for.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes every header send by the server that contains the string the user supplied as parameter.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This action allows you to block server headers for which no dedicated
+ <application>Privoxy</application> action exists. <application>Privoxy</application>
+ will remove every server header that contains the string you supplied as parameter.
+ </para>
+ <para>
+ Regular expressions are <emphasis>not supported</emphasis> and you can't
+ use this action to block different headers in the same request, unless
+ they contain the same string.
+ </para>
+ <para>
+ <literal>crunch-server-header</literal> is only meant for quick tests.
+ If you have to block several different headers, or only want to modify
+ parts of them, you should enable
+ <literal><link linkend="filter-server-headers">filter-server-headers</link></literal>
+ and create your own filter.
+ </para>
+ <para>
+ <warning>
+ Don't block any header without understanding the consequences.
+ </warning>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Crunch server headers that try to prevent caching
+{+crunch-server-header {no-cache}}
+/ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
<!-- ~~~~~ New section ~~~~~ -->
<sect3 renderas="sect4" id="crunch-outgoing-cookies">
<title>crunch-outgoing-cookies</title>
<varlistentry>
<term>Typical use:</term>
<listitem>
- <para>Fool some click-tracking scripts and speed up indirect links</para>
+ <para>Fool some click-tracking scripts and speed up indirect links.</para>
</listitem>
</varlistentry>
<term>Effect:</term>
<listitem>
<para>
- Cut off all but the last valid URL from requests.
+ Detects redirection URLs and redirects the browser without contacting
+ the redirection server first.
</para>
</listitem>
</varlistentry>
<term>Type:</term>
<!-- boolean, parameterized, Multi-value -->
<listitem>
- <para>Boolean.</para>
+ <para>Parameterized.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Parameter:</term>
<listitem>
- <para>
- N/A
- </para>
+ <itemizedlist>
+ <listitem>
+ <para>
+ <quote>simple-check</quote> to just search for the string <quote>http://</quote>
+ to detect redirection URLs.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <quote>check-decoded-url</quote> to decode URLs (if necessary) before searching
+ for redirection URLs.
+ </para>
+ </listitem>
+ </itemizedlist>
</listitem>
</varlistentry>
will link to some script on their own servers, giving the destination as a
parameter, which will then redirect you to the final target. URLs
resulting from this scheme typically look like:
- <emphasis>http://some.place/click-tracker.cgi?target=http://some.where.else</emphasis>.
+ <quote>http://www.example.org/click-tracker.cgi?target=http%3a//www.example.net/</quote>.
</para>
<para>
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
+ browser asks the server for one redirect after the other. Plus, it feeds
the advertisers.
</para>
<para>
This feature is currently not very smart and is scheduled for improvement.
- It is likely to break some sites. You should expect to need possibly
- many exceptions to this action, if it is enabled by default in
- <filename>default.action</filename>. Some sites just don't work without
- it.
+ If it is enabled by default, you will have to create some exceptions to
+ this action. It can lead to failures in several ways:
</para>
- </listitem>
- </varlistentry>
-
+ <para>
+ Not every URLs with other URLs as parameters is evil.
+ Some sites offer a real service that requires this information to work.
+ For example a validation service needs to know, which document to validate.
+ <literal>fast-redirects</literal> assumes that every URL parameter that
+ looks like another URL is a redirection target, and will always redirect to
+ the last one. Most of the time the assumption is correct, but if it isn't,
+ the user gets redirected anyway.
+ </para>
+ <para>
+ Another failure occurs if the URL contains other parameters after the URL parameter.
+ The URL:
+ <quote>http://www.example.org/?redirect=http%3a//www.example.net/&foo=bar</quote>.
+ contains the redirection URL <quote>http://www.example.net/</quote>,
+ followed by another parameter. <literal>fast-redirects</literal> doesn't know that
+ and will cause a redirect to <quote>http://www.example.net/&foo=bar</quote>.
+ Depending on the target server configuration, the parameter will be silently ignored
+ or lead to a <quote>page not found</quote> error. It is possible to fix these redirected
+ requests with <literal><link linkend="filter-client-headers">filter-client-headers</link></literal>
+ but it requires a little effort.
+ </para>
+ <para>
+ To detect a redirection URL, <literal>fast-redirects</literal> only
+ looks for the string <quote>http://</quote>, either in plain text
+ (invalid but often used) or encoded as <quote>http%3a//</quote>.
+ Some sites use their own URL encoding scheme, encrypt the address
+ of the target server or replace it with a database id. In theses cases
+ <literal>fast-redirects</literal> is fooled and the request reaches the
+ redirection server where it probably gets logged.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term>Example usage:</term>
<listitem>
<para>
- <screen>{+fast-redirects}</screen>
+ <screen>+fast-redirects{simple-check}</screen>
+ </para>
+ <para>
+ <screen>+fast-redirects{check-decoded-url}</screen>
</para>
</listitem>
</varlistentry>
<screen>+filter{demoronizer} # Fix MS's non-standard use of standard charsets</screen>
</para>
<para>
- <anchor id="filter-shockwave-flash">
- <screen>+filter{shockwave-flash} # Kill embedded Shockwave Flash objects</screen>
- </para>
+ <anchor id="filter-shockwave-flash">
+ <screen>+filter{shockwave-flash} # Kill embedded Shockwave Flash objects</screen>
+ </para>
+ <para>
+ <anchor id="filter-quicktime-kioskmode">
+ <screen>+filter{quicktime-kioskmode} # Make Quicktime movies saveable</screen>
+ </para>
+ <para>
+ <anchor id="filter-fun">
+ <screen>+filter{fun} # Text replacements for subversive browsing fun!</screen>
+ </para>
+ <para>
+ <anchor id="filter-crude-parental">
+ <screen>+filter{crude-parental} # Crude parental filtering (demo only)</screen>
+ </para>
+ <para>
+ <anchor id="filter-ie-exploits">
+ <screen>+filter{ie-exploits} # Disable some known Internet Explorer bug exploits</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="force-text-mode">
+<title>force-text-mode</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Force <application>Privoxy</application> to treat a document as if it was in some kind of text format.</emphasis></para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Declares a document as text, even if the <quote>Content-Type:</quote> isn't detected as such.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ As explained <literal><link linkend="filter">above</link></literal>,
+ <application>Privoxy</application> tries to only filter files that are
+ in some kind of text format. The same restrictions apply to
+ <literal><link linkend="content-type-overwrite">content-type-overwrite</link></literal>.
+ <literal>force-text-mode</literal> declares a document as text,
+ without looking at the <quote>Content-Type:</quote> first.
+ </para>
+ <warning>
+ <para>
+ Think twice before activating this action. Filtering binary data
+ with regular expressions can cause file damages.
+ </para>
+ </warning>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>
++force-text-mode
+ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="handle-as-empty-document">
+<title>handle-as-empty-document</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Mark URLs that should be replaced by empty documents <emphasis>if they get blocked</emphasis></para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ This action alone doesn't do anything noticeable. It just marks URLs.
+ If the <literal><link linkend="block">block</link></literal> action <emphasis>also applies</emphasis>,
+ the presence or absence of this mark decides whether an HTML <quote>blocked</quote>
+ page, or an empty document will be sent to the client as a substitute for the blocked content.
+ The <q>empty</q> document isn't literally empty, but actually contains a single space.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Some browsers complain about syntax errors if JavaScript documents
+ are blocked with <application>Privoxy's</application>
+ default HTML page; this option can be used to silence them.
+ </para>
+ <para>
+ The content type for the empty document can be specified with
+ <literal><link linkend="content-type-overwrite">content-type-overwrite{}</link></literal>,
+ but usually this isn't necessary.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Block all documents on example.org that end with ".js",
+# but send an empty document instead of the usual HTML message.
+{+block +handle-as-empty-document}
+example.org/.*\.js$
+ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="handle-as-image">
+<title>handle-as-image</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Mark URLs as belonging to images (so they'll be replaced by imagee <emphasis>if they get blocked</emphasis>)</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ This action alone doesn't do anything noticeable. It just marks URLs as images.
+ If the <literal><link linkend="block">block</link></literal> action <emphasis>also applies</emphasis>,
+ the presence or absence of this mark decides whether an HTML <quote>blocked</quote>
+ page, or a replacement image (as determined by the <literal><link
+ linkend="set-image-blocker">set-image-blocker</link></literal> action) will be sent to the
+ client as a substitute for the blocked content.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ The below generic example section is actually part of <filename>default.action</filename>.
+ It marks all URLs with well-known image file name extensions as images and should
+ be left intact.
+ </para>
+ <para>
+ Users will probably only want to use the handle-as-image action in conjunction with
+ <literal><link linkend="block">block</link></literal>, to block sources of banners, whose URLs don't
+ reflect the file type, like in the second example section.
+ </para>
+ <para>
+ Note that you cannot treat HTML pages as images in most cases. For instance, (in-line) ad
+ frames require an HTML page to be sent, or they won't display properly.
+ Forcing <literal>handle-as-image</literal> in this situation will not replace the
+ ad frame with an image, but lead to error messages.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (sections):</term>
+ <listitem>
+ <para>
+ <screen># Generic image extensions:
+#
+{+handle-as-image}
+/.*\.(gif|jpg|jpeg|png|bmp|ico)$
+
+# These don't look like images, but they're banners and should be
+# blocked as images:
+#
+{+block +handle-as-image}
+some.nasty-banner-server.com/junk.cgi?output=trash
+
+# Banner source! Who cares if they also have non-image content?
+ad.doubleclick.net
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-accept-language">
+<title>hide-accept-language</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Pretend to use different language settings.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes or replaces the <quote>Accept-Language:</quote> HTTP header in client requests.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or any user defined value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Faking the browser's language settings can be useful to make a
+ foreign User-Agent set with
+ <literal><link linkend="hide-user-agent">hide-user-agent</link></literal>
+ more believable.
+ </para>
+ <para>
+ However some sites with content in different languages check the
+ <quote>Accept-Language:</quote> to decide which one to take by default.
+ Sometimes it isn't possible to later switch to another language without
+ changing the <quote>Accept-Language:</quote> header first.
+ </para>
+ <para>
+ Therefore it's a good idea to either only change the
+ <quote>Accept-Language:</quote> header to languages you understand,
+ or to languages that aren't widely spread.
+ </para>
+ <para>
+ Before setting the <quote>Accept-Language:</quote> header
+ to a rare language, you should consider that it helps to
+ make your requests unique and thus easier to trace.
+ If you don't plan to change this header frequently,
+ you should stick to a common language.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Pretend to use Canadian language settings.
+{+hide-accept-language{en-ca} \
++hide-user-agent{Mozilla/5.0 (X11; U; OpenBSD i386; en-CA; rv:1.8.0.4) Gecko/20060628 Firefox/1.5.0.4} \
+}
+/ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-content-disposition">
+<title>hide-content-disposition</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent download menus for content you prefer to view inside the browser.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes or replaces the <quote>Content-Disposition:</quote> HTTP header set by some servers.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or any user defined value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
<para>
- <anchor id="filter-quicktime-kioskmode">
- <screen>+filter{quicktime-kioskmode} # Make Quicktime movies saveable</screen>
+ Some servers set the <quote>Content-Disposition:</quote> HTTP header for
+ documents they assume you want to safe locally before viewing them.
+ The <quote>Content-Disposition:</quote> header contains the file name
+ the browser is supposed to use by default.
</para>
<para>
- <anchor id="filter-fun">
- <screen>+filter{fun} # Text replacements for subversive browsing fun!</screen>
+ In most browser that understand this header, it makes it impossible to
+ <emphasis>just view</emphasis> the document, without downloading it first,
+ even if it's just a simple text file or an image.
</para>
<para>
- <anchor id="filter-crude-parental">
- <screen>+filter{crude-parental} # Crude parental filtering (demo only)</screen>
+ Removing the <quote>Content-Disposition:</quote> header helps
+ to prevent this annoyance, but some browser additionally check the
+ <quote>Content-Type:</quote> header, before they decide if the can
+ display a document without saving it first. In these cases you have
+ to change this header as well, before the browser stops displaying
+ download menus.
</para>
<para>
- <anchor id="filter-ie-exploits">
- <screen>+filter{ie-exploits} # Disable some known Internet Explorer bug exploits</screen>
+ It is also possible to change the server's file name suggestion
+ to another one, but in most cases it isn't worth the time to set
+ it up.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Disarm the download link in Sourceforge's patch tracker
+{-filter\
++content-type-overwrite {text/plain}\
++hide-content-disposition {block} }
+.sourceforge.net/tracker/download.php</screen>
</para>
</listitem>
</varlistentry>
<!-- ~~~~~ New section ~~~~~ -->
-<sect3 renderas="sect4" id="handle-as-image">
-<title>handle-as-image</title>
+<sect3 renderas="sect4" id="hide-if-modified-since">
+<title>hide-if-modified-since</title>
<variablelist>
<varlistentry>
<term>Typical use:</term>
<listitem>
- <para>Mark URLs as belonging to images (so they'll be replaced by images <emphasis>if they get blocked</emphasis>)</para>
+ <para>Prevent yet another way to track the user's steps between sessions.</para>
</listitem>
</varlistentry>
<term>Effect:</term>
<listitem>
<para>
- This action alone doesn't do anything noticeable. It just marks URLs as images.
- If the <literal><link linkend="block">block</link></literal> action <emphasis>also applies</emphasis>,
- the presence or absence of this mark decides whether an HTML <quote>blocked</quote>
- page, or a replacement image (as determined by the <literal><link
- linkend="set-image-blocker">set-image-blocker</link></literal> action) will be sent to the
- client as a substitute for the blocked content.
+ Deletes the <quote>If-Modified-Since:</quote> HTTP client header or modifies its value.
</para>
</listitem>
</varlistentry>
<term>Type:</term>
<!-- Boolean, Parameterized, Multi-value -->
<listitem>
- <para>Boolean.</para>
+ <para>Parameterized.</para>
</listitem>
</varlistentry>
<term>Parameter:</term>
<listitem>
<para>
- N/A
- </para>
+ Keyword: <quote>block</quote>, or a user defined value that specifies a range of hours.
+ </para>
</listitem>
</varlistentry>
<term>Notes:</term>
<listitem>
<para>
- The below generic example section is actually part of <filename>default.action</filename>.
- It marks all URLs with well-known image file name extensions as images and should
- be left intact.
+ Removing this header is useful for filter testing, where you want to force a real
+ reload instead of getting status code <quote>304</quote>, which would cause the
+ browser to use a cached copy of the page.
</para>
<para>
- Users will probably only want to use the handle-as-image action in conjunction with
- <literal><link linkend="block">block</link></literal>, to block sources of banners, whose URLs don't
- reflect the file type, like in the second example section.
+ Instead of removing the header, <literal>hide-if-modified-since<literal> can
+ also add or substract a random amount of time to/from the headers value.
+ You specify a range of hours were the random factor should be chosen from and
+ <application>Privoxy</application> does the rest. A negative value means
+ subtracting, a positive value adding.
</para>
<para>
- Note that you cannot treat HTML pages as images in most cases. For instance, (in-line) ad
- frames require an HTML page to be sent, or they won't display properly.
- Forcing <literal>handle-as-image</literal> in this situation will not replace the
- ad frame with an image, but lead to error messages.
+ Randomizing the value of the <quote>If-Modified-Since:</quote> makes
+ sure it isn't used as a cookie replacement, but you will run into
+ caching problems if the random range is to high.
+ </para>
+ <para>
+ It is a good idea to only use a small negative value and let
+ <literal><link linkend="overwrite-last-modified">overwrite-last-modified</link></literal>
+ handle the greater changes.
+ </para>
+ <para>
+ It is also recommended to use this action together with
+ <literal><link linkend="crunch-if-none-match">crunch-if-none-match</link></literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
- <term>Example usage (sections):</term>
+ <term>Example usage (section):</term>
<listitem>
- <para>
- <screen># Generic image extensions:
-#
-{+handle-as-image}
-/.*\.(gif|jpg|jpeg|png|bmp|ico)$
-
-# These don't look like images, but they're banners and should be
-# blocked as images:
-#
-{+block +handle-as-image}
-some.nasty-banner-server.com/junk.cgi?output=trash
-
-# Banner source! Who cares if they also have non-image content?
-ad.doubleclick.net
-</screen>
+ <para>
+ <screen># Let the browser revalidate without being tracked across sessions
+{+hide-if-modified-since {-1}\
++overwrite-last-modified {randomize}\
++crunch-if-none-match}
+/</screen>
</para>
</listitem>
</varlistentry>
<listitem>
<itemizedlist>
<listitem>
- <para><quote>block</quote> to delete the header completely.</para>
+ <para><quote>conditional-block</quote> to delete the header completely if the host has changed.</para>
+ </listitem>
+ <listitem>
+ <para><quote>block</quote> to delete the header unconditionally.</para>
</listitem>
<listitem>
<para><quote>forge</quote> to pretend to be coming from the homepage of the server we are talking to.</para>
<term>Notes:</term>
<listitem>
<para>
- <quote>forge</quote> is the preferred option here, since some servers will
- not send images back otherwise, in an attempt to prevent their valuable
- content from being embedded elsewhere (and hence, without being surrounded
- by <emphasis>their</emphasis> banners).
+ <literal>conditional-block</literal> is the only parameter,
+ that isn't easily detected in the server's log file. If it blocks the
+ referrer, the request will look like the visitor used a bookmark or
+ typed in the address directly.
+ </para>
+ <para>
+ Leaving the referrer unmodified for requests on the same host
+ allows the server owner to see the visitor's <quote>click path</quote>,
+ but in most cases she could also get that information by comparing
+ other parts of the log file: for example the User-Agent if it isn't
+ a very common one, or the user's IP address if it doesn't change between
+ different requests.
+ </para>
+ <para>
+ Always blocking the referrer, or using a custom one, can lead to
+ failures on servers that check the referrer before they answer any
+ requests, in an attempt to prevent their valuable content from being
+ embedded or linked to elsewhere.
+ </para>
+ <para>
+ Both <literal>conditional-block</literal> and <literal>forge</literal>
+ will work with referrer checks, as long as content and valid referring page
+ are on the same host. Most of the time that's the case.
+ </para>
+ <para>
+ <literal>hide-referer</literal> is an alternate spelling of
+ <literal>hide-referrer</literal> and the two can be can be freely
+ substituted with each other. (<quote>referrer</quote> is the
+ correct English spelling, however the HTTP specification has a bug - it
+ requires it to be spelled as <quote>referer</quote>.)
</para>
- <para>
- <literal>hide-referer</literal> is an alternate spelling of
- <literal>hide-referrer</literal> and the two can be can be freely
- substituted with each other. (<quote>referrer</quote> is the
- correct English spelling, however the HTTP specification has a bug - it
- requires it to be spelled as <quote>referer</quote>.)
- </para>
</listitem>
</varlistentry>
<listitem>
<warning>
<para>
- This breaks many web sites that depend on looking at this header in order
- to customize their content for different browsers (which, by the
- way, is <emphasis>NOT</emphasis> a <ulink
- url="http://www.javascriptkit.com/javaindex.shtml">smart way to do
+ This can lead to problems on web sites that depend on looking at this header in
+ order to customize their content for different browsers (which, by the
+ way, is <emphasis>NOT</emphasis> the right thing to do: good web sites
+ work browser-independently).
+ <!--
+ <ulink url="http://www.javascriptkit.com/javaindex.shtml">smart way to do
that</ulink>!).
+ -->
</para>
</warning>
<para>
<varlistentry>
<term>Typical use:</term>
<listitem>
- <para>Prevent abuse of <application>Privoxy</application> as a TCP proxy relay</para>
+ <para>Prevent abuse of <application>Privoxy</application> as a TCP proxy relay or disable SSL for untrusted sites</para>
</listitem>
</varlistentry>
abused as TCP relays very easily.
</para>
<para>
- If you don't know what any of this means, there probably is no reason to
- change this one, since the default is already very restrictive.
+ <application>Privoxy</application> relays HTTPS traffic without seeing
+ the decoded content. Websites can leverage this limitation to circumvent Privoxy's
+ filters. By specifying an invalid port range you can disable HTTPS entirely.
+ If you plan to disable SSL by default, consider enabling
+ <literal><link linkend="treat-forbidden-connects-like-blocks ">treat-forbidden-connects-like-blocks</link></literal>
+ as well, to be able to quickly create exceptions.
</para>
</listitem>
</varlistentry>
<screen>+limit-connect{443} # This is the default and need not be specified.
+limit-connect{80,443} # Ports 80 and 443 are OK.
+limit-connect{-3, 7, 20-100, 500-} # Ports less than 3, 7, 20 to 100 and above 500 are OK.
-+limit-connect{-} # All ports are OK (gaping security hole!)</screen>
++limit-connect{-} # All ports are OK
++limit-connect{,} # No HTTPS traffic is allowed</screen>
</para>
</listitem>
</varlistentry>
<listitem>
<para>
Ensure that servers send the content uncompressed, so it can be
- passed through <literal><link linkend="filter">filter</link></literal>s
+ passed through <literal><link linkend="filter">filter</link></literal>s.
</para>
</listitem>
</varlistentry>
<term>Effect:</term>
<listitem>
<para>
- Adds a header to the request that asks for uncompressed transfer.
+ Removes the Accept-Encoding header which can be used to ask for compressed transfer.
</para>
</listitem>
</varlistentry>
</sect3>
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="overwrite-last-modified">
+<title>overwrite-last-modified</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent yet another way to track the user's steps between sessions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>Last-Modified:</quote> HTTP server header or modifies its value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ One of the keywords: <quote>block</quote>, <quote>reset-to-request-time</quote>
+ and <quote>randomize</quote>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Removing the <quote>Last-Modified:</quote> header is useful for filter
+ testing, where you want to force a real reload instead of getting status
+ code <quote>304</quote>, which would cause the browser to reuse the old
+ version of the page.
+ </para>
+ <para>
+ The <quote>randomize</quote> option overwrites the value of the
+ <quote>Last-Modified:</quote> header with a randomly chosen time
+ between the original value and the current time. In theory the server
+ could send each document with a different <quote>Last-Modified:</quote>
+ header to track visits without using cookies. <quote>Randomize</quote>
+ makes it impossible and the browser can still revalidate cached documents.
+ </para>
+ <para>
+ <quote>reset-to-request-time</quote> overwrites the value of the
+ <quote>Last-Modified:</quote> header with the current time. You could use
+ this option together with
+ <literal><link linkend="hide-if-modified-since">hided-if-modified-since</link></literal>
+ to further customize your random range.
+ </para>
+ <para>
+ The preferred parameter here is <quote>randomize</quote>. It is safe
+ to use, as long as the time settings are more or less correct.
+ If the server sets the <quote>Last-Modified:</quote> header to the time
+ of the request, the random range becomes zero and the value stays the same.
+ Therefore you should later randomize it a second time with
+ <literal><link linkend="hide-if-modified-since">hided-if-modified-since</link></literal>,
+ just to be sure.
+ </para>
+ <para>
+ It is also recommended to use this action together with
+ <literal><link linkend="crunch-if-none-match">crunch-if-none-match</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Let the browser revalidate without being tracked across sessions
+{+hide-if-modified-since {-1}\
++overwrite-last-modified {randomize}\
++crunch-if-none-match}
+/</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="redirect">
+<title>redirect</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Redirect requests to other sites.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Convinces the browser that the requested document has been moved
+ to another location and the browser should get it from there.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any URL.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This action is useful to replace whole documents with your own
+ ones. For that to work, they have to be available on another server.
+ </para>
+ <para>
+ You can do the same by combining the actions
+ <literal><link linkend="block">block</link></literal>,
+ <literal><link linkend="handle-as-image">handle-as-image</link></literal> and
+ <literal><link linkend="set-image-blocker">set-image-blocker{URL}</link></literal>.
+ It doesn't sound right for non-image documents, and that's why this action
+ was created.
+ </para>
+ <para>
+ This action will be ignored if you use it together with
+ <literal><link linkend="block">block</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Replace example.com's style sheet with another one
+{+redirect{http://localhost/css-replacements/example.com.css}}
+example.com/stylesheet.css</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+</variablelist>
+</sect3>
+
+
<!-- ~~~~~ New section ~~~~~ -->
<sect3 renderas="sect4" id="send-vanilla-wafer">
<title>send-vanilla-wafer</title>
</sect3>
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="treat-forbidden-connects-like-blocks">
+<title>treat-forbidden-connects-like-blocks</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Block forbidden connects with an easy to find error message.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ If this action is enabled, <application>Privoxy</application> no longer
+ makes a difference between forbidden connects and ordinary blocks.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>N/A</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ By default <application>Privoxy</application> answers
+ <link linkend="limit-connect">forbidden <quote>Connect</quote> requests</link>
+ with a short error message inside the headers. If the browser doesn't display
+ headers (most don't), you just see an empty page.
+ </para>
+ <para>
+ With this action enabled, <application>Privoxy</application> displays
+ the message that is used for ordinary blocks instead. If you decide
+ to make an exception for the page in question, you can do so by
+ following the <quote>See why</quote> link.
+ </para>
+ <para>
+ For <quote>Connect</quote> requests the clients tell
+ <application>Privoxy</application> which host they are interested
+ in, but not which document they plan to get later. As a result, the
+ <quote>Go there anyway</quote> link becomes rather useless:
+ it lets the client request the home page of the forbidden host
+ through unencrypted HTTP, still using the port of the last request.
+ </para>
+ <para>
+ If you previously configured <application>Privoxy</application> to do the
+ request through a SSL tunnel, everything will work. Most likely you haven't
+ and the server will responds with an error message because it is expecting
+ HTTPS.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <para>
+ <screen>+treat-forbidden-connects-like-blocks</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
<!-- ~~~~~ New section ~~~~~ -->
<sect3>
<title>Summary</title>
Temple Place - Suite 330, Boston, MA 02111-1307, USA.
$Log: user-manual.sgml,v $
+ Revision 2.11 2006/07/18 14:48:51 david__schmidt
+ Reorganizing the repository: swapping out what was HEAD (the old 3.1 branch)
+ with what was really the latest development (the v_3_0_branch branch)
+
Revision 1.123.2.43 2005/05/23 09:59:10 hal9
Fix typo 'loose'
projects / privoxy.git / commitdiff