Ubuntu Manpage: ffproxy — filtering HTTP/HTTPS proxy server

NAME

     ffproxy — filtering HTTP/HTTPS proxy server

SYNOPSIS

     ffproxy [-p port] [-c ip|hostname] [-C ip|hostname] [-l children] [-u uid|user -g gid|group]
             [-r dir] [-D datadir] [-x proxyip|proxyhost -X proxyport] [-a ip|hostname] [-A port]
             [-n piddir] [-f configfile] [-ds4bBhv]

DESCRIPTION

ffproxy is a filtering HTTP/HTTPS proxy server. It is able to filter by host, URL, and
header. Custom header entries can be filtered and added. It can even drop its privileges
and optionally chroot(2) to some directory. Logging to syslog(3) is supported, as is using
another auxiliary proxy server. An HTTP accelerator feature (acting as a front-end to an
HTTP server) is included. Contacting IPv6 servers as well as binding to IPv6 is supported
and allows transparent IPv6 over IPv4 browsing (and vice versa).

Remind that there is an alternative to command line options by using configuration files.
See ffproxy.conf(5) and sample.config for details. It allows options that are not available
on command line.

The following command line options are recognized. They specify general settings like IP to
bind to or place of the db/ and html/ directories. Note that arguments to options must be
separated from the option by spaces, as are such options from each other.

-p port Bind to port. Default is 8080.

-c ip|hostname
Bind to IPv4. Default is any IPv4.

-C ip|hostname
Bind to IPv6. Default is any IPv6.

-l children
Maximum number of child processes to be forked. That is, the maximum number of
concurrent requests allowed. Default is 10.

-u uid|user -g gid|group
Change UID and GID. Both options must be used. Default is not changing UID and
GID.

-r dir Change root chroot(7) to dir. Used in conjunction with -u and -g. Because ffproxy
drops its privileges and chroots after reading the configuration files, -D should
be set to . (the current dir). It might need /etc/resolv.conf copied as
etc/resolv.conf in its working directory. Example: ``# cd /var/ffproxy ;
/usr/local/bin/ffproxy -r /var/ffproxy -D . -d -u proxy -g proxy -f ""''

-x ip|hostname
Specify IP (or hostname) of an auxiliary proxy server that the program will forward
requests to. Used together with -X.

-X port Port number of auxiliary proxy.

-D dir Location of the db/ and html/ directories. For example, specifying -D /var/ffproxy
tells the proxy to search for db/ files in /var/ffproxy/db/ and html/ files in
/var/ffproxy/html/.

-a ip|hostname
Auxiliary forward HTTP server to use (see section HTTP ACCELERATOR).

-A port Port to use for above. Defaults to 80.

-n piddir
directory to store file ffproxy.pid with ffproxy pid inside. Default is /var/run

-f configfile
User configuration file to load. Please note that command line options get
overwritten by set configuration file options. Default location is
/etc/ffproxy/ffproxy.conf. Read ffproxy.conf(5) for details. Use -f "" to disable
configuration files.

-d Run as daemon.

-s Be silent. Don't log to syslog.

-4 Use IPv4 only. Do not try contacting servers via IPv6.

-b Don't bind to IPv4. Might be needed under Linux 2.4, due to a ``Feature'' IPv6
binds to IPv4, too. Try using this option or bind to specific IPv6 address via -C.

-B Don't bind to IPv6.

-h Show usage information.

-v Display version number.

THE DB/ DIRECTORY

The db/ directory contains files that control the behaviour of ffproxy. The files for
filtering are prefixed by `filter'. Access to the proxy server is controlled by files with
prefix `host'.

Filtering
Requests or header entries to be filtered are matched by extended regular expressions or
case insensitive by strings.

ffproxy is able to filter requests by host, header, remote header, and URL. The specific
files are

filter.host.match
filter.header.drop
filter.header.entry
filter.header.match
filter.rheader.drop
filter.rheader.entry
filter.rheader.match
filter.url.match

Files ending in `drop' specify requests to be completely filtered (dropped). Files ending
in `entry' specify header entries to be removed from the header. They are matched case
insensitive without extended regular expressions. Files ending in `match' specify extended
regular expressions to be matched against header entries, host, or URL.

Adding custom header entries is also supported. The entries of file filter.header.add will
be added to every outgoing request.

Access Control
Access to the proxy is controlled through the files prefixed `host'.

host.dyndns contains host names with dynamic IPv4 addresses. The host names are resolved to
IPv4 addresses and compared to the client's IP. If it matches, access is granted.

host.ip contains static IPv4 and IPv6 address.

host.name contains official hostnames (reverse lookup).

Except for host.dyndns, the files contain extended regular expressions. If any of the
entries matches, access is granted.

Layout of db/ Files
Every mentioned file above must exist, although it may be empty. Every entry is exactly one
line. Empty lines are ignored, as are lines beginning with a # (comments).

The location of the db/ directory may be specified by an argument to the command line option
-D. If this option and configuration file option db_files_path are not used, ffproxy will
search for db/ and html/ in /usr/share/ffproxy.

ffproxy comes with sample db/ files. They also contain needed and suggested entries, as
described next.

Suggested db/ file entries
The file filter.header.entry should contain following entries for the program's proper
operation

Accept-Encoding:
Accept:
Connection:
Proxy-Connection:
Host:

First two lines are needed for browsers that send out Accept*: Headers but don't understand
encoded data coming back from the proxy. Host: has to be removed, since proxies require
absolute URIs (Host: is redundant).

filter.header.add should contain

Connection: close
Proxy-Connection: close

We removed the two entries through filter.header.entry and now implant our own to force
disconnection after each request.

filter.rheader.entry should contain

Connection:
Proxy-Connection:

Whatever the server answered, we remove it.

THE HTML/ DIRECTORY

     This directory contains files with HTTP header and HTML that are sent to the user's browser
     if either an error occurred or a request was filtered.  In the files, the variable $u will
     be replaced by the URL, $h by the host to connect to, and $c by the hostname of the client.

     Since the files are loaded into memory for faster execution, the size of each file is
     limited to about 8 kB (what is more than enough, the default files are under 1 kB).

     The specific files are (every file must exist)

           connect      Connection failed (503)
           filtered     Request filtered (200)
           invalid      Invalid request (400)
           post         Unable to post data (400)
           resolve      Resolve error (503)

HTTP ACCELERATOR

     ffproxy may also be used as a HTTP accelerator, that is, connecting to just one HTTP server
     and being a front-end to that.  Use accel_host and accel_port in configuration file or
     command line options -a and -A to use this feature.

     Default behaviour is *not* sending Host: header to allow insertion of a custom one via
     filter.header.add (see section THE DB/ DIRECTORY) or keeping the original one used by
     connecting client (`Host:' hast to be removed from default filter.header.entry, of course).
     To change this, use `accel_user_host no' in the configuration file.  ``Host:
     accel_host:accel_port'' will be used then.

TRANSPARENT OPERATION

     It is possible to redirect all HTTP traffic, that is, traffic to port 80, to the proxy's
     listening port.  It will then transparently act as a HTTP proxy, the client not even knowing
     it is connecting to a proxy.

     On OpenBSD one could enable this by adding a line like

           rdr on rl0 proto tcp from any to any port 80 -> 127.0.0.1 port 8080

     to /etc/pf.conf.  In this example, rl0 is the local interface.  All traffic coming from rl0
     directed to port 80 (HTTP standard port) is sent to 127.0.0.1:8080 where ffproxy is supposed
     to be listening.

KEEP ALIVE

     The program supports keep alive on client to proxy connections.  This is used automatically
     by default and may be disabled by setting `use_keep_alive no' in the configuration file.

HTTPS OPERATION

     The proxy allows HTTPS proxying via implementation of the CONNECT request method.  By
     default, only port 443 is allowed for CONNECT.  This may be changed by using
     `unrestricted_connect yes' in the configuration file.  Timeout may also be tuned by
     `timeout_connect seconds'.

RELOADING CONFIGURATION

     Send a SIGHUP to the pid of the ffproxy master process to let it reload db/ files, html/
     files, *and* configuration file.  If no configuration file was specified,
     /etc/ffproxy/ffproxy.conf is tried.  Of course, only some changes to the program can be done
     at runtime.  See ffproxy.conf(5) for details on options that may be changed at runtime.

     ffproxy write its pid file ffproxy.pid in the directory specified by the command line
     parameter -n or the pid_dir setting in config file. Default is /var/run.

LOGGING

     By default, the proxy logs incorrect and filtered requests.  To log all requests, use the
     configuration file keyword `log_all_requests yes'.  Please make sure that you separate the
     programs log output from that of other programs by modifying syslog.conf(5), since the
     output is very noisy.

FILES

     Behaviour of ffproxy is determined by

     •   startup options given either on the command line or read from configuration files --
         /etc/ffproxy/ffproxy.conf is loaded by default.

     •   the files in db/ which specify filtering options and who is allowed to connect and use
         ffproxy

CONTRIBUTORS

     Dobrica Pavlinusic <dpavlin@rot13.org> provided patches for http accelerator feature

VERSION

     This manual documents ffproxy 1.6 (2005-01-05).

     Send bug reports, comments, suggestions to <niklas@noxa.de>

AUTHOR

     Niklas Olmes <niklas@noxa.de>

                                           Jan 5, 2005