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Internet JUNKBUSTER Technical Information

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This document is out of date

Development of JunkBuster is ongoing and this document is no longer current. However, it may provide some assistance. If you have problems, please use the Yahoo Groups mailing list (which includes an archive of mail), the SourceForge.net project page, or see the project's home page. Please also bear in mind that versions 2.9.x of JunkBuster are development releases, and are not production quality.

Manual Page

A copy of this page in standard man macro format is included in the tar archive.

Name

junkbuster - The Internet Junkbuster Proxy ^TM

Synopsis

junkbuster configfile (Unix)
junkbstr.exe [configfile] (Windows)

Description

junkbuster is an instrumentable proxy that filters the HTTP stream between web servers and browsers. Its main purposes are to block adverts and enhance privacy.

It is configured using a configuration file and several files listing URL patterns. The configuration file must be specified on the command line. The Windows version will default to using the configuration file junkbstr.ini if it exists and no argument was given.

All files except the main configuration file are checked for changes before each page is fetched, so they may edited without restarting the proxy.

Options

blockfile blockfile

Block requests to URLs matching any pattern given in the lines of the blockfile. The junkbuster instead returns status 202, indicating that the request has been accepted (though not completed), and a message identifying itself (though the browser may display only a broken image icon). The syntax of a pattern is [domain][:port][/path] (the http:// or https:// protocol part is omitted). To decide if a pattern matches a target, the domains are compared first, then the paths.

To compare the domains, the pattern domain and the target domain specified in the URL are each broken into their components. (Components are separated by the . (period) character.) Next each of the target components is compared with the corresponding pattern component: last with last, next-to-last with next-to-last, and so on. (This is called right-anchored matching.) If all of the pattern components find their match in the target, then the domains are considered a match. Case is irrelevant when comparing domain components.

A successfully matching pattern can be an anchored substring of a target, but not vice versa. Thus if a pattern doesn't specify a domain, it matches all domains. Furthermore, when comparing two components, the components must either match in their entirety or up to a wildcard * (star character) in the pattern. The wildcard feature implements only a "prefix" match capability ("abc*" vs. "abcdefg"), not suffix matching ("*efg" vs. "abcdefg") or infix matching ("abc*efg" vs. "abcdefg"). The feature is restricted to the domain component; it is unrelated to the optional regular expression feature in the path (described below).

If a numeric port is specified in the pattern domain, then the target port must match as well. The default port in a target is port 80.

If the domain and port match, then the target URL path is checked for a match against the path in the pattern. Paths are compared with a simple case-sensitive left-anchored substring comparison. Once again, the pattern can be an anchored substring of the target, but not vice versa. A path of / (slash) would match all paths. Wildcards are not considered in path comparisons.

For example, the target URL
    the.yellow-brick-road.com/TinMan/has_no_brain
would be matched (and blocked) by the following patterns
    yellow-brick-road.com
and
   Yellow*.COM
and
   /TinM
but not
    follow.the.yellow-brick-road.com
or
   /tinman

Comments in a blockfile start with a # (hash) character and end at a new line. Blank lines are also ignored.

Lines beginning with a ~ (tilde) character are taken to be exceptions: a URL blocked by previous patterns that matches the rest of the line is let through. (The last match wins.)

Patterns may contain POSIX regular expressions provided the junkbuster was compiled with this option (the default in Version 2.0 on). The idiom /*.*/ad can then be used to match any URL containing /ad (such as http://nomatterwhere.com/images/advert/g3487.gif for example). These expressions don't work in the domain part.

In version 1.3 and later the blockfile and cookiefile are checked for changes before each request.

wafer NAME=VALUE

Specifies a pair to be sent as a cookie with every request to the server. (Such boring cookies are called wafers.) This option may be called more than once to generate multiple wafers. The original Netscape specification prohibited semi-colons, commas and white space; these characters will be URL-encoded if used in wafers. The Path and Domain attributes are not currently supported.

cookiefile cookiefile

Enforce the cookie management policy specified in the cookiefile. If this option is not used all cookies are silently crunched, so that users who never want cookies aren't bothered by browsers asking whether each cookie should be accepted. However, cookies can still get through via JavaScript and SSL, so alerts should be left on.

In Version 1.2 and later this option must be followed by a filename containing instructions on which sites are allowed to receive and set cookies. By default cookies are dropped in both the browser's request and the server's response, unless the URL requested matches an entry in the cookiefile. The matching algorithm is the same as for the blockfile. A leading > character allows server-bound cookies only; a < allows only browser-bound cookies; a ~ character stops cookies in both directions. Thus a cookiefile containing a single line with the two characters >* will pass on all cookies to servers but not give any new ones to the browser.

jarfile jarfile

All Set-cookie attempts by the server are logged to jarfile. If no wafer is specified, one containing a canned notice (the vanilla wafer) is added as an alert to the server unless the suppress-vanilla-wafer option is invoked.

suppress-vanilla-wafer

Suppress the vanilla wafer.

from from

If the browser discloses an email address in the FROM header (most don't), replace it with from. If from is set to . (the period character) the FROM is passed to the server unchanged. The default is to delete the FROM header.

referer referer

Whenever the browser discloses the URL that led to the current request, replace it with referer. If referer is set to . (period) the URL is passed to the server unchanged. If referer is set to @ (at) the URL is sent in cases where the cookiefile specifies that a cookie would be sent. (No way to send bogus referers selectively is provided.) The default is to delete Referer.

Junkbuster also accepts the spelling referrer, which most dictionaries consider correct.

user-agent user-agent

Information disclosed by the browser about itself is replaced with the value user-agent. If user-agent is set to . (period) the User-Agent header is passed to the server unchanged, along with any UA headers produced by MS-IE (which would otherwise be deleted). If user-agent is set to @ (at) these headers are sent unchanged in cases where the cookiefile specifies that a cookie would be sent, otherwise only default User-Agent header is sent. That default is Mozilla/3.0 (Netscape) with an unremarkable Macintosh configuration. If used with a browser less advanced than Mozilla/3.0 or IE-3, the default may encourage pages containing extensions that confuse the browser.

listen-address [host][:port]

If host is specified, bind the junkbuster to that IP address. If a port is specified, use it. The default port is 8000; the default host is localhost.

This default host setting means that you can only connect to the proxy from ther local computer. This is a security measure - if you allow anyone to use the proxy, then hackers or fraudsters could use it to help hide their identity. It also provides a lot of protection against any undiscovered security flaws in JunkBuster - if they can't connect to it, then they can't attack it.

If you change this value, we recommend you either set the host to localhost:
   listen-address localhost:8080
or, if you want to share a single internet connection over your internal network, then set it to the address of your internal ethernet card:
   listen-address 10.1.1.1:8080
(replace 10.1.1.1 with your internal IP address), or set up an aclfile. To make the proxy accessible from everywhere (e.g. if you're using an access control list or if you just don't care about security), specify just the port number - e.g:
   listen-address :8000
(This binds the proxy to all IP addresses (INADDR_ANY)).

forwardfile forwardfile

Junkbuster has a flexible syntax for forwarding HTTP requests. This is used e.g. if you are behind a firewall and need to connect through it, or if you want to use a cacheing proxy to speed up your web browsing.

Every line in the forwardfile consists of four components, seperated by whitespace. These are:

target forward_to via_gateway_type gateway

target is a pattern used to select which line of the forwardfile is used. "*" is the most commonly used value, and matches every URL. As usual, the last matching target wins. (If no pattern matches, a direct connection will be used)

forward_to specifies the HTTP proxy server to use, or "." for none. This is used to connect to a cacheing proxy such as Squid, and for most types of firewall. The port number defaults to 8000 if it is not specified.

Here is a typical line.

*         lpwa.com:8000      .      .

The target domain need not be a fully qualified hostname; it can be a general domain such as com or co.uk or even just a port number. For example, because LPWA does not handle SSL, the line above will typically be followed by a line such as

:443    .      .      .

to allow SSL transactions to proceed directly. The cautious would also add an entry in their blockfile to stop transactions to port 443 for all but specified trusted sites.

Configure with care: no loop detection is performed. When setting up chains of proxies that might loop back, try adding Squid.

via_gateway_type and gateway are used to support SOCKS proxies. Some firewalls provide this type of proxy. If you do not not want to use a SOCKS proxy, specify both of these fields as ".".

Note that JunkBuster is a SOCKS client, not a SOCKS server. The user's browser should not be configured to use SOCKS; the proxy conducts the negotiations, not the browser.

The SOCKS4 protocol may be specified by setting via_gateway_type to socks or socks4. The SOCKS4A protocol is specified as socks4a. The SOCKS5 protocol is not currently supported.

gateway should be the host and port of the SOCKS server. If you just specify a hostname, then the port number defaults to 1080.

The user identification capabilities of SOCKS4 are deliberately not used; the user is always identified to the SOCKS server as userid=anonymous. If the server's policy is to reject requests from anonymous, the proxy will not work. Use a debug value of 3 to see the status returned by the server.

If you specify both a HTTP proxy (with forward_to) and a SOCKS proxy (with gateway) then the SOCKS proxy is used to connect to the HTTP proxy. If you just specify a SOCKS proxy, it is used to connect directly to the websites.

debug N

Set debug mode. The most common value is 1, to pinpoint offensive URLs, so they can be added to the blockfile. The value of N is a bitwise logical-OR of the following values:
1 = URLs (show each URL requested by the browser);
2 = Connections (show each connection to or from the proxy);
4 = I/O (log I/O errors);
8 = Headers (as each header is scanned, show the header and what is done to it);
16 = Log everything (including debugging traces and the contents of the pages).
32 = Record accesses in Common Log Format, as used by most web and proxy servers.

Multiple debug lines are permitted; they are logical OR-ed together.

Because most browsers send several requests in parallel the debugging output may appear intermingled, so the single-threaded option is recommended when using debug with N greater than 1.

add-forwarded-header

Add X-Forwarded-For headers to the server-bound HTTP stream indicating the client IP address to the server, in the new style of Squid 1.1.4. If you want the traditional HTTP_FORWARDED response header, add it manually with the -x option. This also allows other X-Forwarded-For headers to be transmitted - usually they are discarded.

add-header HeaderText

Add the HeaderText verbatim to requests to the server. Typical uses include adding old-style forwarding notices such as Forwarded: by http://pro-privacy-isp.net and reinstating the Proxy-Connection: Keep-Alive header (which the junkbuster deletes so as not to reveal its existence). No checking is done for correctness or plausibility, so it can be used to throw any old trash into the server-bound HTTP stream. Please don't litter.

single-threaded

Doesn't fork() a separate process (or create a separate thread) to handle each connection. Useful when debugging to keep the process single threaded.

logfile logfile

Write all debugging data into logfile. The default logfile is the standard output.

aclfile aclfile

Unless this option is used, the proxy talks to anyone who can connect to it, and everyone who can has equal permissions on where they can go. An access file allows restrictions to be placed on these two policies, by distinguishing some source IP addresses and/or some destination addresses. (If a forwarder or a gateway is being used, its address is considered the destination address, not the ultimate IP address of the URL requested.)

Each line of the access file begins with either the word permit or deny followed by source and (optionally) destination addresses to be matched against those of the HTTP request. The last matching line specifies the result: if it was a deny line or if no line matched, the request will be refused.

A source or destination can be specified as a single numeric IP address, or with a hostname, provided that the host's name can be resolved to a numeric address: this cannot be used to block all .mil domains for example, because there is no single address associated with that domain name. Either form may be followed by a slash and an integer N, specifying a subnet mask of N bits. For example, permit 207.153.200.72/24 matches the entire Class-C subnet from 207.153.200.0 through 207.153.200.255. (A netmask of 255.255.255.0 corresponds to 24 bits of ones in the netmask, as with *_MASKLEN=24.) A value of 16 would be used for a Class-B subnet. A value of zero for N in the subnet mask length will cause any address to match; this can be used to express a default rule. For more information see the example file provided with the distribution.

If you like these access controls you should probably have firewall; they are not intended to replace one.

trustfile trustfile

This feature is experimental, has not been fully documented and is very subject to change. The goal is for parents to be able to choose a page or site whose links they regard suitable for their young children and for the proxy to allow access only to sites mentioned there. To do this the proxy examines the referer variable on each page request to check they resulted from a click on the ``trusted referer'' site: if so the referred site is added to a list of trusted sites, so that the child can then move around that site. There are several uncertainties in this scheme that experience may be able to iron out; check back in the months ahead.

trust_info_url trust_info_url

When access is denied due to lack of a trusted referer, this URL is displayed with a message pointing the user to it for further information.

hide-console

In the Windows command-line version only, instructs the program to disconnect from and hide the command console after starting.

Installation and Use

Browsers must be told where to find the junkbuster (e.g. localhost port 8000). To set the HTTP proxy in Netscape 3.0, go through: Options; Network Preferences; Proxies; Manual Proxy Configuration; View. See the FAQ for other browsers. The Security Proxy should also be set to the same values, otherwise shttp: URLs won't work.

Note the limitations explained in the FAQ.

Checking Options

To allow users to check that a junkbuster is running and how it is configured, it intercepts requests for any URL ending in /show-proxy-args and blocks it, returning instead returns information on its version number and current configuration including the contents of its blockfile. To get an explicit warning that no junkbuster intervened if the proxy was not configured, it's best to point it to a URL that does this, such as http://internet.junkbuster.com/cgi-bin/show-proxy-args on Junkbusters's website.

Copyright and GPL

Written and copyright by the Anonymous Coders and Junkbusters Corporation and made available under the GNU General Public License (GPL). This software comes with NO WARRANTY. Internet Junkbuster Proxy is a trademark of Junkbusters Corporation.