The Main Configuration File

The Main Configuration File
Privoxy 4.1.0 User Manual
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7. The Main Configuration File
By default, the main configuration file is named
config
, with the exception of
Windows, where it is named
config.txt
. 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:
confdir /etc/privoxy
Assigns the value
/etc/privoxy
to the option
confdir
and thus
indicates that the configuration directory is named
"/etc/privoxy/"
All options in the config file except for
confdir
and
logdir
are optional. Watch out in the below description for what happens if you leave them unset.
The main config file controls all aspects of
Privoxy
's operation that are not
location dependent (i.e. they apply universally, no matter where you may be surfing). Like the filter and action
files, the config file is a plain text file and can be modified with a text editor like emacs, vim or
notepad.exe.
7.1. Local Set-up Documentation
If you intend to operate
Privoxy
for more users than just yourself, it might
be a good idea to let them know how to reach you, what you block and why you do that, your policies, etc.
7.1.1. user-manual
Specifies:
Location of the
Privoxy
User Manual.
Type of value:
A fully qualified URI
Default value:
Unset
Effect if unset:
version
/user-manual/
will be used, where
version
is the
Privoxy
version.
Notes:
The User Manual URI is the single best source of information on
Privoxy
, and is used for help links from some of the internal CGI pages. The manual
itself is normally packaged with the binary distributions, so you probably want to set this to a locally
installed copy.
Examples:
The best all purpose solution is simply to put the full local
PATH
to where
the
User Manual
is located:
user-manual /usr/share/doc/privoxy/user-manual
The User Manual is then available to anyone with access to
Privoxy
by following the built-in URL:
(or the
shortcut:
).
If the documentation is not on the local system, it can be accessed from a remote server, as:
user-manual http://example.com/privoxy/user-manual/
Warning
If set, this option should be
the first option in
the config file
, because it is used while the config file is being read on
start-up.
7.1.2. trust-info-url
Specifies:
A URL to be displayed in the error page that users will see if access to an untrusted page is
denied.
Type of value:
URL
Default value:
Unset
Effect if unset:
No links are displayed on the "untrusted" error page.
Notes:
The value of this option only matters if the trust mechanism has been activated. (See
trustfile
below.)
If you use the trust mechanism, it is a good idea to write up some on-line documentation about your
trust policy and to specify the URL(s) here. Use multiple times for multiple URLs.
The URL(s) should be added to the trustfile as well, so users don't end up locked out from the
information on why they were locked out in the first place!
7.1.3. admin-address
Specifies:
An email address to reach the
Privoxy
administrator.
Type of value:
Email address
Default value:
Unset
Effect if unset:
No email address is displayed on error pages and the CGI user interface.
Notes:
If both
admin-address
and
proxy-info-url
are unset,
the whole "Local Privoxy Support" box on all generated pages will not be shown.
7.1.4. proxy-info-url
Specifies:
A URL to documentation about the local
Privoxy
setup, configuration
or policies.
Type of value:
URL
Default value:
Unset
Effect if unset:
No link to local documentation is displayed on error pages and the CGI user interface.
Notes:
If both
admin-address
and
proxy-info-url
are unset,
the whole "Local Privoxy Support" box on all generated pages will not be shown.
This URL shouldn't be blocked ;-)
7.2. Configuration and Log File Locations
Privoxy
can (and normally does) use a number of other files for additional
configuration, help and logging. This section of the configuration file tells
Privoxy
where to find those other files.
The user running
Privoxy
, must have read permission for all configuration
files, and write permission to any files that would be modified, such as log files and actions files.
7.2.1. confdir
Specifies:
The directory where the other configuration files are located.
Type of value:
Path name
Default value:
/etc/privoxy (Unix)
or
Privoxy
installation dir (Windows)
Effect if unset:
Mandatory
Notes:
No trailing
, please.
7.2.2. templdir
Specifies:
An alternative directory where the templates are loaded from.
Type of value:
Path name
Default value:
unset
Effect if unset:
The templates are assumed to be located in confdir/template.
Notes:
Privoxy's
original templates are usually overwritten with each
update. Use this option to relocate customized templates that should be kept. As template variables might
change between updates, you shouldn't expect templates to work with
Privoxy
releases other than the one they were part of, though.
7.2.3. temporary-directory
Specifies:
A directory where Privoxy can create temporary files.
Type of value:
Path name
Default value:
unset
Effect if unset:
No temporary files are created, external filters don't work.
Notes:
To execute
external
filters
Privoxy
has to create temporary files. This directive
specifies the directory the temporary files should be written to.
It should be a directory only
Privoxy
(and trusted users) can
access.
7.2.4. logdir
Specifies:
The directory where all logging takes place (i.e. where the
logfile
is
located).
Type of value:
Path name
Default value:
/var/log/privoxy (Unix)
or
Privoxy
installation dir (Windows)
Effect if unset:
Mandatory
Notes:
No trailing
, please.
7.2.5. actionsfile
Specifies:
The
actions file(s)
to use
Type of value:
Complete file name, relative to
confdir
Default values:
match-all.action # Actions that are applied to all sites and maybe overruled later on.
default.action   # Main actions file
user.action      # User customizations
Effect if unset:
No actions are taken at all. More or less neutral proxying.
Notes:
Multiple
actionsfile
lines are permitted, and are in fact recommended!
The default values are
default.action
, which is the
"main"
actions file maintained by the developers, and
user.action
, where you can make your personal additions.
Actions files contain all the per site and per URL configuration for ad blocking, cookie management,
privacy considerations, etc.
7.2.6. filterfile
Specifies:
The
filter file(s)
to use
Type of value:
File name, relative to
confdir
Default value:
default.filter (Unix)
or
default.filter.txt
(Windows)
Effect if unset:
No textual content filtering takes place, i.e. all
filter
name
actions in the
actions files are turned neutral.
Notes:
Multiple
filterfile
lines are permitted.
The
filter files
contain content modification rules that use
regular expressions
. These rules permit powerful changes on the content of Web
pages, and optionally the headers as well, e.g., you could try to disable your favorite JavaScript
annoyances, re-write the actual displayed text, or just have some fun playing buzzword bingo with web
pages.
The
filter
name
actions rely on the relevant filter (
name
) to be defined in a filter file!
A pre-defined filter file called
default.filter
that contains a number of
useful filters for common problems is included in the distribution. See the section on the
filter
action for a list.
It is recommended to place any locally adapted filters into a separate file, such as
user.filter
7.2.7. logfile
Specifies:
The log file to use
Type of value:
File name, relative to
logdir
Default value:
Unset (commented out)
. When activated: logfile
(Unix)
or
privoxy.log (Windows).
Effect if unset:
No logfile is written.
Notes:
The logfile is where all logging and error messages are written. The level of detail and number of
messages are set with the
debug
option (see below). 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) and it can help you to monitor what your browser is doing.
Depending on the debug options below, the logfile may be a privacy risk if third parties can get
access to it. As most users will never look at it,
Privoxy
only logs
fatal errors by default.
For most troubleshooting purposes, you will have to change that, please refer to the debugging section
for details.
Any log files must be writable by whatever user
Privoxy
is being run
as (on Unix, default user id is
"privoxy"
).
To prevent the logfile from growing indefinitely, it is recommended to periodically rotate or shorten
it. Many operating systems support log rotation out of the box, some require additional software to do
it. For details, please refer to the documentation for your operating system.
7.2.8. trustfile
Specifies:
The name of the trust file to use
Type of value:
File name, relative to
confdir
Default value:
Unset (commented out)
. When activated: trust
(Unix)
or
trust.txt (Windows)
Effect if unset:
The entire trust mechanism is disabled.
Notes:
The trust mechanism is an experimental feature for building white-lists and should be used with care.
It is
NOT
recommended for the casual user.
If you specify a trust file,
Privoxy
will only allow access to sites
that are specified in the trustfile. Sites can be listed in one of two ways:
Prepending a
character limits access to this site only (and any sub-paths
within this site), e.g.
~www.example.com
allows access to
~www.example.com/features/news.html
, etc.
Or, you can designate sites as
trusted
referrers
, by prepending the name with a
character. The effect is
that access to untrusted sites will be granted -- but only if a link from this trusted referrer was used
to get there. The link target will then be added to the
"trustfile"
so that
future, direct accesses will be granted. Sites added via this mechanism do not become trusted referrers
themselves (i.e. they are added with a
designation). There is a limit of 512
such entries, after which new entries will not be made.
If you use the
operator in the trust file, it may grow considerably over
time.
It is recommended that
Privoxy
be compiled with the
--disable-force
--disable-toggle
and
--disable-editor
options, if this feature is to be used.
Possible applications include limiting Internet access for children.
7.3. Debugging
These options are mainly useful when tracing a problem. Note that you might also want to invoke
Privoxy
with the
--no-daemon
command line option when
debugging.
7.3.1. debug
Specifies:
Key values that determine what information gets logged.
Type of value:
Integer values
Default value:
0 (i.e.: only fatal errors (that cause Privoxy to exit) are logged)
Effect if unset:
Default value is used (see above).
Notes:
The available debug levels are:
debug 1 # Log the destination for each request. See also debug 1024.
debug 2 # show each connection status
debug 4 # show tagging-related messages
debug 8 # show header parsing
debug 16 # log all data written to the network
debug 32 # debug force feature
debug 64 # debug regular expression filters
debug 128 # debug redirects
debug 256 # debug GIF de-animation
debug 512 # Common Log Format
debug 1024 # Log the destination for requests
Privoxy
didn't let through, and the reason why.
debug 2048 # CGI user interface
debug 4096 # Startup banner and warnings.
debug 8192 # Non-fatal errors
debug 32768 # log all data read from the network
debug 65536 # Log the applying actions
To select multiple debug levels, you can either add them or use multiple
debug
lines.
A debug level of 1 is informative because it will show you each request as it happens.
1, 1024, 4096 and 8192 are recommended
so that you will notice
when things go wrong. The other levels are probably only of interest if you are hunting down a specific
problem. They can produce a lot of output (especially 16).
If you are used to the more verbose settings, simply enable the debug lines below again.
If you want to use pure CLF (Common Log Format), you should set
"debug 512"
ONLY
and not enable anything else.
Privoxy
has a hard-coded limit for the length of log messages. If
it's reached, messages are logged truncated and marked with
"... [too long,
truncated]"
Please don't file any support requests without trying to reproduce the problem with increased debug
level first. Once you read the log messages, you may even be able to solve the problem on your own.
7.3.2. single-threaded
Specifies:
Whether to run only one server thread.
Type of value:
1 or 0
Default value:
Effect if unset:
Multi-threaded (or, where unavailable: forked) operation, i.e. the ability to serve multiple requests
simultaneously.
Notes:
This option is only there for debugging purposes.
It will
drastically reduce performance.
7.3.3. hostname
Specifies:
The hostname shown on the CGI pages.
Type of value:
Text
Default value:
Unset
Effect if unset:
The hostname provided by the operating system is used.
Notes:
On some misconfigured systems resolving the hostname fails or takes too much time and slows Privoxy
down. Setting a fixed hostname works around the problem.
In other circumstances it might be desirable to show a hostname other than the one returned by the
operating system. For example if the system has several different hostnames and you don't want to use the
first one.
Note that Privoxy does not validate the specified hostname value.
7.4. Access Control and Security
This section of the config file controls the security-relevant aspects of
Privoxy
's configuration.
7.4.1. listen-address
Specifies:
The address and TCP port on which
Privoxy
will listen for client
requests.
Type of value:
IP-Address
]:
Port
Hostname
]:
Port
Default value:
127.0.0.1:8118
Effect if unset:
Bind to 127.0.0.1 (IPv4 localhost), port 8118. This is suitable and recommended for home users who run
Privoxy
on the same machine as their browser.
Notes:
You will need to configure your browser(s) to this proxy address and port.
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.
You can use this statement multiple times to make
Privoxy
listen on
more ports or more
IP
addresses. Suitable if your operating system does not
support sharing
IPv6
and
IPv4
protocols on the
same socket.
If a hostname is used instead of an IP address,
Privoxy
will try to
resolve it to an IP address and if there are multiple, use the first one returned.
If the address for the hostname isn't already known on the system (for example because it's in
/etc/hostname), this may result in DNS traffic.
If the specified address isn't available on the system, or if the hostname can't be resolved,
Privoxy
will fail to start. On GNU/Linux, and other platforms that can
listen on not yet assigned IP addresses, Privoxy will start and will listen on the specified address
whenever the IP address is assigned to the system
IPv6 addresses containing colons have to be quoted by brackets. They can only be used if
Privoxy
has been compiled with IPv6 support. If you aren't sure if your version
supports it, have a look at
Some operating systems will prefer IPv6 to IPv4 addresses even if the system has no IPv6 connectivity
which is usually not expected by the user. Some even rely on DNS to resolve localhost which mean the
"localhost" address used may not actually be local.
It is therefore recommended to explicitly configure the intended IP address instead of relying on the
operating system, unless there's a strong reason not to.
If you leave out the address,
Privoxy
will bind to all IPv4
interfaces (addresses) on your machine and may become reachable from the Internet and/or the local
network. Be aware that some GNU/Linux distributions modify that behaviour without updating the
documentation. Check for non-standard patches if your
Privoxy
version
behaves differently.
If you configure
Privoxy
to be reachable from the network, consider
using
access control lists
(ACL's, see below), and/or a firewall.
If you open
Privoxy
to untrusted users, you should also make sure
that the following actions are disabled:
enable-edit-actions
and
enable-remote-toggle
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
Suppose you are running
Privoxy
on an IPv6-capable machine and you
want it to listen on the IPv6 address of the loopback device:
listen-address [::1]:8118
7.4.2. toggle
Specifies:
Initial state of "toggle" status
Type of value:
1 or 0
Default value:
Effect if unset:
Act as if toggled on
Notes:
If set to 0,
Privoxy
will start in
"toggled
off"
mode, i.e. mostly behave like a normal, content-neutral proxy with both ad blocking and
content filtering disabled. See
enable-remote-toggle
below.
7.4.3. enable-remote-toggle
Specifies:
Whether or not the
web-based toggle
feature
may be used
Type of value:
0 or 1
Default value:
Effect if unset:
The web-based toggle feature is disabled.
Notes:
When toggled off,
Privoxy
mostly acts like a normal, content-neutral
proxy, i.e. doesn't block ads or filter content.
Access to the toggle feature can
not
be
controlled separately by
"ACLs"
or HTTP authentication, so that everybody who
can access
Privoxy
(see
"ACLs"
and
listen-address
above) can toggle it for all users. So this option is
not recommended
for multi-user environments with untrusted
users.
Note that malicious client side code (e.g Java) is also capable of using this option.
As a lot of
Privoxy
users don't read documentation, this feature is
disabled by default.
Note that you must have compiled
Privoxy
with support for this
feature, otherwise this option has no effect.
7.4.4.
enable-remote-http-toggle
Specifies:
Whether or not Privoxy recognizes special HTTP headers to change its behaviour.
Type of value:
0 or 1
Default value:
Effect if unset:
Privoxy ignores special HTTP headers.
Notes:
When toggled on, the client can change
Privoxy's
behaviour by setting
special HTTP headers. Currently the only supported special header is
"X-Filter:
No"
, to disable filtering for the ongoing request, even if it is enabled in one of the action
files.
This feature is disabled by default. If you are using
Privoxy
in a
environment with trusted clients, you may enable this feature at your discretion. Note that malicious
client side code (e.g Java) is also capable of using this feature.
This option will be removed in future releases as it has been obsoleted by the more general header
taggers.
7.4.5. enable-edit-actions
Specifies:
Whether or not the
web-based actions
file editor
may be used
Type of value:
0 or 1
Default value:
Effect if unset:
The web-based actions file editor is disabled.
Notes:
Access to the editor can
not
be controlled
separately by
"ACLs"
or HTTP authentication, so that everybody who can access
Privoxy
(see
"ACLs"
and
listen-address
above) can modify its configuration for all users.
This option is
not recommended
for environments
with untrusted users and as a lot of
Privoxy
users don't read
documentation, this feature is disabled by default.
Note that malicious client side code (e.g Java) is also capable of using the actions editor and you
shouldn't enable this options unless you understand the consequences and are sure your browser is
configured correctly.
Note that you must have compiled
Privoxy
with support for this
feature, otherwise this option has no effect.
7.4.6. enforce-blocks
Specifies:
Whether the user is allowed to ignore blocks and can
"go there anyway"
Type of value:
0 or 1
Default value:
Effect if unset:
Blocks are not enforced.
Notes:
Privoxy
is mainly used to block and filter requests as a service to
the user, for example to block ads and other junk that clogs the pipes.
Privoxy's
configuration isn't perfect and sometimes innocent pages are blocked. In
this situation it makes sense to allow the user to enforce the request and have
Privoxy
ignore the block.
In the default configuration
Privoxy's
"Blocked"
page contains a
"go there anyway"
link to adds a
special string (the force prefix) to the request URL. If that link is used,
Privoxy
will detect the force prefix, remove it again and let the request pass.
Of course
Privoxy
can also be used to enforce a network policy. In
that case the user obviously should not be able to bypass any blocks, and that's what the
"enforce-blocks"
option is for. If it's enabled,
Privoxy
hides the
"go there anyway"
link. If the user adds the force prefix by hand,
it will not be accepted and the circumvention attempt is logged.
Example:
enforce-blocks 1
7.4.7. ACLs: permit-access and deny-access
Specifies:
Who can access what.
Type of value:
src_addr
[:
port
][/
src_masklen
] [
dst_addr
[:
port
][/
dst_masklen
]]
Where
src_addr
and
dst_addr
are IPv4 addresses in dotted decimal notation or valid DNS names,
port
is a port number, and
src_masklen
and
dst_masklen
are subnet masks in CIDR notation, i.e. integer values
from 2 to 30 representing the length (in bits) of the network address. The masks and the whole
destination part are optional.
If your system implements
RFC 3493
then
src_addr
and
dst_addr
can be
IPv6 addresses delimited by brackets,
port
can be a number or a
service name, and
src_masklen
and
dst_masklen
can be a number from 0 to 128.
Default value:
Unset
If no
port
is specified, any port will match. If no
src_masklen
or
src_masklen
is given, the
complete IP address has to match (i.e. 32 bits for IPv4 and 128 bits for IPv6).
Effect if unset:
Don't restrict access further than implied by
listen-address
Notes:
Access controls are included at the request of ISPs and systems administrators, and
are not usually needed by individual users
. For a typical home
user, it will normally suffice to ensure that
Privoxy
only listens on
the localhost (127.0.0.1) or internal (home) network address by means of the
listen-address
option.
Please see the warnings in the FAQ that
Privoxy
is not intended to be
a substitute for a firewall or to encourage anyone to defer addressing basic security weaknesses.
Multiple ACL lines are OK. If any ACLs are specified,
Privoxy
only
talks to IP addresses that match at least one
permit-access
line and don't match
any subsequent
deny-access
line. In other words, the last match wins, with the
default being
deny-access
If
Privoxy
is using a forwarder (see
forward
below) for a particular destination URL, the
dst_addr
that is
examined is the address of the forwarder and
NOT
the address of the ultimate target. This is necessary because it may be impossible for the local
Privoxy
to determine the IP address of the ultimate target (that's often
what gateways are used for).
You should prefer using IP addresses over DNS names, because the address lookups take time. All DNS
names must resolve! You can
not
use domain patterns
like
"*.org"
or partial domain names. If a DNS name resolves to multiple IP
addresses, only the first one is used.
Some systems allow IPv4 clients to connect to IPv6 server sockets. Then the client's IPv4 address will
be translated by the system into IPv6 address space with special prefix ::ffff:0:0/96 (so called IPv4
mapped IPv6 address).
Privoxy
can handle it and maps such ACL addresses
automatically.
Denying access to particular sites by ACL may have undesired side effects if the site in question is
hosted on a machine which also hosts other sites (most sites are).
Examples:
Explicitly define the default behavior if no ACL and
listen-address
are set:
"localhost"
is OK. The absence of a
dst_addr
implies that
all
destination addresses are OK:
permit-access localhost
Allow any host on the same class C subnet as www.privoxy.org access to nothing but www.example.com (or
other domains hosted on the same system):
permit-access www.privoxy.org/24 www.example.com/32
Allow access from any host on the 26-bit subnet 192.168.45.64 to anywhere, with the exception that
192.168.45.73 may not access the IP address behind www.dirty-stuff.example.com:
permit-access 192.168.45.64/26
deny-access 192.168.45.73 www.dirty-stuff.example.com
Allow access from the IPv4 network 192.0.2.0/24 even if listening on an IPv6 wild card address (not
supported on all platforms):
permit-access 192.0.2.0/24
This is equivalent to the following line even if listening on an IPv4 address (not supported on all
platforms):
permit-access [::ffff:192.0.2.0]/120
7.4.8. buffer-limit
Specifies:
Maximum size of the buffer for content filtering.
Type of value:
Size in Kbytes
Default value:
4096
Effect if unset:
Use a 4MB (4096 KB) limit.
Notes:
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. Hence this
option.
When a document buffer size reaches the
buffer-limit
, it is flushed to the
client unfiltered and no further attempt to filter the rest of the document is made. Remember that there
may be multiple threads running, which might require up to
buffer-limit
Kbytes
each
, unless you have enabled
"single-threaded"
above.
7.4.9. enable-proxy-authentication-forwarding
Specifies:
Whether or not proxy authentication through
Privoxy
should work.
Type of value:
0 or 1
Default value:
Effect if unset:
Proxy authentication headers are removed.
Notes:
Privoxy itself does not support proxy authentication, but can allow clients to authenticate against
Privoxy's parent proxy.
By default Privoxy (3.0.21 and later) don't do that and remove Proxy-Authorization headers in requests
and Proxy-Authenticate headers in responses to make it harder for malicious sites to trick inexperienced
users into providing login information.
If this option is enabled the headers are forwarded.
Enabling this option is
not recommended
if there
is no parent proxy that requires authentication or if the local network between Privoxy and the parent
proxy isn't trustworthy. If proxy authentication is only required for some requests, it is recommended to
use a client header filter to remove the authentication headers for requests where they aren't
needed.
7.4.10. trusted-cgi-referer
Specifies:
A trusted website or webpage whose links can be followed to reach sensitive CGI pages
Type of value:
URL or URL prefix
Default value:
Unset
Effect if unset:
No external pages are considered trusted referers.
Notes:
Before
Privoxy
accepts configuration changes through CGI pages like
client-tags
or the
remote toggle
, it checks the Referer header to see if the request
comes from a trusted source.
By default only the webinterface domains
config.privoxy.org
and
p.p
are considered trustworthy.
Requests originating from other domains are rejected to prevent third-parties from modifiying Privoxy's
state by e.g. embedding images that result in CGI requests.
In some environments it may be desirable to embed links to CGI pages on external pages, for example on
an Intranet homepage the Privoxy admin controls.
The
"trusted-cgi-referer"
option can be used to add that page, or the whole
domain, as trusted source so the resulting requests aren't rejected. Requests are accepted if the
specified trusted-cgi-refer is the prefix of the Referer.
If the trusted source is supposed to access the CGI pages via JavaScript the
cors-allowed-origin
option can be used.
Warning
Declaring pages the admin doesn't control trustworthy may allow malicious third parties to
modify Privoxy's internal state against the user's wishes and without the user's knowledge.
7.4.11. cors-allowed-origin
Specifies:
A trusted website which can access
Privoxy
's CGI pages through
JavaScript.
Type of value:
URL
Default value:
Unset
Effect if unset:
No external sites get access via cross-origin resource sharing.
Notes:
Modern browsers by default prevent cross-origin requests made via JavaScript to
Privoxy
's CGI interface even if
Privoxy
would trust
the referer because it's white listed via the
trusted-cgi-referer
directive.
Cross-origin
resource sharing (CORS)
is a mechanism to allow cross-origin requests.
The
"cors-allowed-origin"
option can be used to specify a domain that is
allowed to make requests to Privoxy CGI interface via JavaScript. It is used in combination with the
trusted-cgi-referer
directive.
Warning
Declaring domains the admin doesn't control trustworthy may allow malicious third parties to
modify Privoxy's internal state against the user's wishes and without the user's knowledge.
7.5. Forwarding
This feature allows routing of HTTP requests through a chain of multiple proxies.
Forwarding can be used to chain Privoxy with a caching proxy to speed up browsing. Using a parent proxy may
also be necessary if the machine that
Privoxy
runs on has no direct Internet
access.
Note that parent proxies can severely decrease your privacy level. For example a parent proxy could add your
IP address to the request headers and if it's a caching proxy it may add the
"Etag"
header to revalidation requests again, even though you configured Privoxy to remove it. It may also ignore
Privoxy's header time randomization and use the original values which could be used by the server as cookie
replacement to track your steps between visits.
Also specified here are SOCKS proxies.
Privoxy
supports the SOCKS 4, SOCKS 4A
and SOCKS 5 protocols.
7.5.1. forward
Specifies:
To which parent HTTP proxy specific requests should be routed.
Type of value:
target_pattern
http_parent
[:
port
where
target_pattern
is a
URL pattern
that specifies to which requests (i.e. URLs) this forward
rule shall apply. Use
to denote
"all URLs"
http_parent
[:
port
] is the DNS
name or IP address of the parent HTTP proxy through which the requests should be forwarded, optionally
followed by its listening port (default: 8000). Use a single dot (
) to denote
"no forwarding"
Default value:
Unset
Effect if unset:
Don't use parent HTTP proxies.
Notes:
If
http_parent
is
"."
, then requests
are not forwarded to another HTTP proxy but are made directly to the web servers.
http_parent
can be a numerical IPv6 address (if
RFC 3493
is implemented). To prevent clashes with
the port delimiter, the whole IP address has to be put into brackets. On the other hand a
target_pattern
containing an IPv6 address has to be put into angle brackets
(normal brackets are reserved for regular expressions already).
Multiple lines are OK, they are checked in sequence, and the last match wins.
Examples:
Everything goes to an example parent proxy, except SSL on port 443 (which it doesn't handle):
forward / parent-proxy.example.org:8080
forward :443 .
Everything goes to our example ISP's caching proxy, except for requests to that ISP's sites:
forward / caching-proxy.isp.example.net:8000
forward .isp.example.net .
Parent proxy specified by an IPv6 address:
forward / [2001:DB8::1]:8000
Suppose your parent proxy doesn't support IPv6:
forward / parent-proxy.example.org:8000
forward ipv6-server.example.org .
forward <[2-3][0-9a-f][0-9a-f][0-9a-f]:*> .
7.5.2. forward-socks4, forward-socks4a, forward-socks5 and
forward-socks5t
Specifies:
Through which SOCKS proxy (and optionally to which parent HTTP proxy) specific requests should be
routed.
Type of value:
target_pattern
user
pass
@]
socks_proxy
[:
port
http_parent
[:
port
where
target_pattern
is a
URL pattern
that specifies to which requests (i.e. URLs) this forward
rule shall apply. Use
to denote
"all URLs"
http_parent
and
socks_proxy
are
IP addresses in dotted decimal notation or valid DNS names (
http_parent
may be
"."
to denote
"no HTTP forwarding"
), and the optional
port
parameters are TCP ports, i.e. integer values from 1 to 65535.
user
and
pass
can be used for SOCKS5 authentication if required.
Default value:
Unset
Effect if unset:
Don't use SOCKS proxies.
Notes:
Multiple lines are OK, they are checked in sequence, and the last match wins.
The difference between
forward-socks4
and
forward-socks4a
is that in the SOCKS 4A protocol, the DNS resolution of the target
hostname happens on the SOCKS server, while in SOCKS 4 it happens locally.
With
forward-socks5
the DNS resolution will happen on the remote server as
well.
forward-socks5t
works like vanilla
forward-socks5
but lets
Privoxy
additionally use Tor-specific SOCKS extensions.
Currently the only supported SOCKS extension is optimistic data which can reduce the latency for the
first request made on a newly created connection.
socks_proxy
and
http_parent
can be a numerical IPv6 address (if
RFC
3493
is implemented). To prevent clashes with the port delimiter, the whole IP address has to be put
into brackets. On the other hand a
target_pattern
containing an IPv6
address has to be put into angle brackets (normal brackets are reserved for regular expressions
already).
If
http_parent
is
"."
, then requests
are not forwarded to another HTTP proxy but are made (HTTP-wise) directly to the web servers, albeit
through a SOCKS proxy.
Examples:
From the company example.com, direct connections are made to all
"internal"
domains, but everything outbound goes through their ISP's proxy by way of example.com's corporate SOCKS
4A gateway to the Internet.
forward-socks4a / socks-gw.example.com:1080 www-cache.isp.example.net:8080
forward .example.com .
A rule that uses a SOCKS 4 gateway for all destinations but no HTTP parent looks like this:
forward-socks4 / socks-gw.example.com:1080 .
To connect SOCKS5 proxy which requires username/password authentication:
forward-socks5 / user:pass@socks-gw.example.com:1080 .
To chain Privoxy and Tor, both running on the same system, you would use something like:
forward-socks5t / 127.0.0.1:9050 .
Note that if you got Tor through one of the bundles, you may have to change the port from 9050 to 9150
(or even another one). For details, please check the documentation on the
Tor website
The public
Tor
network can't be used to reach your local network, if
you need to access local servers you therefore might want to make some exceptions:
forward 192.168.*.*/ .
forward 10.*.*.*/ .
forward 127.*.*.*/ .
Unencrypted connections to systems in these address ranges will be as (un)secure as the local network
is, but the alternative is that you can't reach the local network through
Privoxy
at all. Of course this may actually be desired and there is no reason to
make these exceptions if you aren't sure you need them.
If you also want to be able to reach servers in your local network by using their names, you will need
additional exceptions that look like this:
forward localhost/ .
7.5.3. Advanced
Forwarding Examples
If you have links to multiple ISPs that provide various special content only to their subscribers, you can
configure multiple
Privoxies
which have connections to the respective ISPs to
act as forwarders to each other, so that
your
users can
see the internal content of all ISPs.
Assume that host-a has a PPP connection to isp-a.example.net. And host-b has a PPP connection to
isp-b.example.org. Both run
Privoxy
. Their forwarding configuration can look
like this:
host-a:
forward / .
forward .isp-b.example.net host-b:8118
host-b:
forward / .
forward .isp-a.example.org host-a:8118
Now, your users can set their browser's proxy to use either host-a or host-b and be able to browse the
internal content of both isp-a and isp-b.
If you intend to chain
Privoxy
and
squid
locally, then chaining as
browser -> squid -> privoxy
is the recommended
way.
Assuming that
Privoxy
and
squid
run on the
same box, your
squid
configuration could then look like this:
# Define Privoxy as parent proxy (without ICP)
cache_peer 127.0.0.1 parent 8118 7 no-query

# Define ACL for protocol FTP
acl ftp proto FTP

# Do not forward FTP requests to Privoxy
always_direct allow ftp

# Forward all the rest to Privoxy
never_direct allow all
You would then need to change your browser's proxy settings to
squid
's
address and port. Squid normally uses port 3128. If unsure consult
http_port
in
squid.conf
You could just as well decide to only forward requests you suspect of leading to Windows executables through
a virus-scanning parent proxy, say, on
antivir.example.com
, port 8010:
forward / .
forward /.*\.(exe|com|dll|zip)$ antivir.example.com:8010
7.5.4.
forwarded-connect-retries
Specifies:
How often Privoxy retries if a forwarded connection request fails.
Type of value:
Number of retries.
Default value:
Effect if unset:
Connections forwarded through other proxies are treated like direct connections and no retry attempts
are made.
Notes:
forwarded-connect-retries
is mainly interesting for socks4a
connections, where
Privoxy
can't detect why the connections failed. The
connection might have failed because of a DNS timeout in which case a retry makes sense, but it might
also have failed because the server doesn't exist or isn't reachable. In this case the retry will just
delay the appearance of Privoxy's error message.
Note that in the context of this option,
"forwarded connections"
includes
all connections that Privoxy forwards through other proxies. This option is not limited to the HTTP
CONNECT method.
Only use this option, if you are getting lots of forwarding-related error messages that go away when
you try again manually. Start with a small value and check Privoxy's logfile from time to time, to see
how many retries are usually needed.
Example:
forwarded-connect-retries 1
7.6. Miscellaneous
7.6.1.
accept-intercepted-requests
Specifies:
Whether intercepted requests should be treated as valid.
Type of value:
0 or 1
Default value:
Effect if unset:
Only proxy requests are accepted, intercepted requests are treated as invalid.
Notes:
If you don't trust your clients and want to force them to use
Privoxy
, enable this option and configure your packet filter to redirect outgoing
HTTP connections into
Privoxy
Note that intercepting encrypted connections (HTTPS) isn't supported.
Make sure that
Privoxy's
own requests aren't redirected as well.
Additionally take care that
Privoxy
can't intentionally connect to
itself, otherwise you could run into redirection loops if
Privoxy's
listening port is reachable by the outside or an attacker has access to the pages you visit.
If you are running Privoxy as intercepting proxy without being able to intercept all client requests
you may want to adjust the CGI templates to make sure they don't reference content from
config.privoxy.org.
Example:
accept-intercepted-requests 1
7.6.2.
allow-cgi-request-crunching
Specifies:
Whether requests to
Privoxy's
CGI pages can be blocked or
redirected.
Type of value:
0 or 1
Default value:
Effect if unset:
Privoxy
ignores block and redirect actions for its CGI pages.
Notes:
By default
Privoxy
ignores block or redirect actions for its CGI
pages. Intercepting these requests can be useful in multi-user setups to implement fine-grained access
control, but it can also render the complete web interface useless and make debugging problems painful if
done without care.
Don't enable this option unless you're sure that you really need it.
Example:
allow-cgi-request-crunching 1
7.6.3. split-large-forms
Specifies:
Whether the CGI interface should stay compatible with broken HTTP clients.
Type of value:
0 or 1
Default value:
Effect if unset:
The CGI form generate long GET URLs.
Notes:
Privoxy's
CGI forms can lead to rather long URLs. This isn't a
problem as far as the HTTP standard is concerned, but it can confuse clients with arbitrary URL length
limitations.
Enabling split-large-forms causes
Privoxy
to divide big forms into
smaller ones to keep the URL length down. It makes editing a lot less convenient and you can no longer
submit all changes at once, but at least it works around this browser bug.
If you don't notice any editing problems, there is no reason to enable this option, but if one of the
submit buttons appears to be broken, you should give it a try.
Example:
split-large-forms 1
7.6.4. keep-alive-timeout
Specifies:
Number of seconds after which an open connection will no longer be reused.
Type of value:
Time in seconds.
Default value:
None
Effect if unset:
Connections are not kept alive.
Notes:
This option allows clients to keep the connection to
Privoxy
alive.
If the server supports it,
Privoxy
will keep the connection to the
server alive as well. Under certain circumstances this may result in speed-ups.
By default,
Privoxy
will close the connection to the server if the
client connection gets closed, or if the specified timeout has been reached without a new request coming
in. This behaviour can be changed with the
connection-sharing
option.
This option has no effect if
Privoxy
has been compiled without
keep-alive support.
Note that a timeout of five seconds as used in the default configuration file significantly decreases
the number of connections that will be reused. The value is used because some browsers limit the number
of connections they open to a single host and apply the same limit to proxies. This can result in a
single website
"grabbing"
all the connections the browser allows, which means
connections to other websites can't be opened until the connections currently in use time out.
Several users have reported this as a Privoxy bug, so the default value has been reduced. Consider
increasing it to 300 seconds or even more if you think your browser can handle it. If your browser
appears to be hanging, it probably can't.
Example:
keep-alive-timeout 300
7.6.5. tolerate-pipelining
Specifies:
Whether or not pipelined requests should be served.
Type of value:
0 or 1.
Default value:
None
Effect if unset:
If Privoxy receives more than one request at once, it terminates the client connection after serving
the first one.
Notes:
Privoxy
currently doesn't pipeline outgoing requests, thus allowing
pipelining on the client connection is not guaranteed to improve the performance.
By default
Privoxy
tries to discourage clients from pipelining by
discarding aggressively pipelined requests, which forces the client to resend them through a new
connection.
This option lets
Privoxy
tolerate pipelining. Whether or not that
improves performance mainly depends on the client configuration.
If you are seeing problems with pages not properly loading, disabling this option could work around
the problem.
Example:
tolerate-pipelining 1
7.6.6.
default-server-timeout
Specifies:
Assumed server-side keep-alive timeout if not specified by the server.
Type of value:
Time in seconds.
Default value:
None
Effect if unset:
Connections for which the server didn't specify the keep-alive timeout are not reused.
Notes:
Enabling this option significantly increases the number of connections that are reused, provided the
keep-alive-timeout
option is also enabled.
While it also increases the number of connections problems when
Privoxy
tries to reuse a connection that already has been closed on the server side,
or is closed while
Privoxy
is trying to reuse it, this should only be a
problem if it happens for the first request sent by the client. If it happens for requests on reused
client connections,
Privoxy
will simply close the connection and the
client is supposed to retry the request without bothering the user.
Enabling this option is therefore only recommended if the
connection-sharing
option is disabled.
It is an error to specify a value larger than the
keep-alive-timeout
value.
This option has no effect if
Privoxy
has been compiled without
keep-alive support.
Example:
default-server-timeout 60
7.6.7. connection-sharing
Specifies:
Whether or not outgoing connections that have been kept alive should be shared between different
incoming connections.
Type of value:
0 or 1
Default value:
None
Effect if unset:
Connections are not shared.
Notes:
This option has no effect if
Privoxy
has been compiled without
keep-alive support, or if it's disabled.
Notes:
Note that reusing connections doesn't necessary cause speedups. There are also a few privacy
implications you should be aware of.
If this option is enabled, outgoing connections are shared between clients (if there are more than
one) and closing the browser that initiated the outgoing connection does not affect the connection
between
Privoxy
and the server unless the client's request hasn't been
completed yet.
If the outgoing connection is idle, it will not be closed until either
Privoxy's
or the server's timeout is reached. While it's open, the server knows that
the system running
Privoxy
is still there.
If there are more than one client (maybe even belonging to multiple users), they will be able to reuse
each others connections. This is potentially dangerous in case of authentication schemes like NTLM where
only the connection is authenticated, instead of requiring authentication for each request.
If there is only a single client, and if said client can keep connections alive on its own, enabling
this option has next to no effect. If the client doesn't support connection keep-alive, enabling this
option may make sense as it allows
Privoxy
to keep outgoing connections
alive even if the client itself doesn't support it.
You should also be aware that enabling this option increases the likelihood of getting the "No server
or forwarder data" error message, especially if you are using a slow connection to the Internet.
This option should only be used by experienced users who understand the risks and can weight them
against the benefits.
Example:
connection-sharing 1
7.6.8. socket-timeout
Specifies:
Number of seconds after which a socket times out if no data is received.
Type of value:
Time in seconds.
Default value:
None
Effect if unset:
A default value of 300 seconds is used.
Notes:
The default is quite high and you probably want to reduce it. If you aren't using an occasionally slow
proxy like Tor, reducing it to a few seconds should be fine.
Warning
When a TLS library is being used to read or write data from a socket with
https-inspection
enabled the socket-timeout currently isn't applied and the timeout used depends on the library
(which may not even use a timeout).
Example:
socket-timeout 300
7.6.9.
max-client-connections
Specifies:
Maximum number of client connections that will be served.
Type of value:
Positive number.
Default value:
128
Notes:
Connections are served until a resource limit is reached.
Privoxy
creates one thread (or process) for every incoming client
connection that isn't rejected based on the access control settings.
If the system is powerful enough,
Privoxy
can theoretically deal with
several hundred (or thousand) connections at the same time, but some operating systems enforce resource
limits by shutting down offending processes and their default limits may be below the ones
Privoxy
would require under heavy load.
Configuring
Privoxy
to enforce a connection limit below the thread or
process limit used by the operating system makes sure this doesn't happen. Simply increasing the
operating system's limit would work too, but if
Privoxy
isn't the only
application running on the system, you may actually want to limit the resources used by
Privoxy
If
Privoxy
is only used by a single trusted user, limiting the number
of client connections is probably unnecessary. If there are multiple possibly untrusted users you
probably still want to additionally use a packet filter to limit the maximal number of incoming
connections per client. Otherwise a malicious user could intentionally create a high number of
connections to prevent other users from using
Privoxy
Obviously using this option only makes sense if you choose a limit below the one enforced by the
operating system.
One most POSIX-compliant systems
Privoxy
can't properly deal with
more than FD_SETSIZE file descriptors if
Privoxy
has been configured to
use select() and has to reject connections if the limit is reached. When using select() this limit
therefore can't be increased without recompiling
Privoxy
with a
different FD_SETSIZE limit unless
Privoxy
is running on Windows with
_WIN32 defined.
When
Privoxy
has been configured to use poll() the FD_SETSIZE limit
does not apply.
Example:
max-client-connections 256
7.6.10. listen-backlog
Specifies:
Connection queue length requested from the operating system.
Type of value:
Number.
Default value:
128
Effect if unset:
A connection queue length of 128 is requested from the operating system.
Notes:
Under high load incoming connection may queue up before Privoxy gets around to serve them. The queue
length is limited by the operating system. Once the queue is full, additional connections are dropped
before Privoxy can accept and serve them.
Increasing the queue length allows Privoxy to accept more incoming connections that arrive roughly at
the same time.
Note that Privoxy can only request a certain queue length, whether or not the requested length is
actually used depends on the operating system which may use a different length instead.
On many operating systems a limit of -1 can be specified to instruct the operating system to use the
maximum queue length allowed. Check the listen man page to see if your platform allows this.
On some platforms you can use "netstat -Lan -p tcp" to see the effective queue length.
Effectively using a value above 128 usually requires changing the system configuration as well. On
FreeBSD-based system the limit is controlled by the kern.ipc.soacceptqueue sysctl.
Example:
listen-backlog 4096
7.6.11.
enable-accept-filter
Specifies:
Whether or not Privoxy should use an accept filter
Type of value:
0 or 1
Default value:
Effect if unset:
No accept filter is enabled.
Notes:
Accept filters reduce the number of context switches by not passing sockets for new connections to
Privoxy until a complete HTTP request is available.
As a result, Privoxy can process the whole request right away without having to wait for additional
data first.
For this option to work, Privoxy has to be compiled with FEATURE_ACCEPT_FILTER and the operating
system has to support it (which may require loading a kernel module).
Currently accept filters are only supported on FreeBSD-based systems. Check the
accf_http(9) man page
to learn
how to enable the support in the operating system.
Example:
enable-accept-filter 1
7.6.12.
handle-as-empty-doc-returns-ok
Specifies:
The status code Privoxy returns for pages blocked with
+handle-as-empty-document
Type of value:
0 or 1
Default value:
Effect if unset:
Privoxy returns a status 403(forbidden) for all blocked pages.
Effect if set:
Privoxy returns a status 200(OK) for pages blocked with +handle-as-empty-document and a status
403(Forbidden) for all other blocked pages.
Notes:
This directive was added as a work-around for Firefox bug 492459:
"Websites are no
longer rendered if SSL requests for JavaScripts are blocked by a proxy."
), the bug has been fixed for quite some
time, but this directive is also useful to make it harder for websites to detect whether or not resources
are being blocked.
7.6.13. enable-compression
Specifies:
Whether or not buffered content is compressed before delivery.
Type of value:
0 or 1
Default value:
Effect if unset:
Privoxy does not compress buffered content.
Effect if set:
Privoxy compresses buffered content before delivering it to the client, provided the client supports
it.
Notes:
This directive is only supported if Privoxy has been compiled with FEATURE_COMPRESSION, which should
not to be confused with FEATURE_ZLIB.
Compressing buffered content is mainly useful if Privoxy and the client are running on different
systems. If they are running on the same system, enabling compression is likely to slow things down. If
you didn't measure otherwise, you should assume that it does and keep this option disabled.
Privoxy will not compress buffered content below a certain length.
7.6.14. compression-level
Specifies:
The compression level that is passed to the zlib library when compressing buffered content.
Type of value:
Positive number ranging from 0 to 9.
Default value:
Notes:
Compressing the data more takes usually longer than compressing it less or not compressing it at all.
Which level is best depends on the connection between Privoxy and the client. If you can't be bothered to
benchmark it for yourself, you should stick with the default and keep compression disabled.
If compression is disabled, the compression level is irrelevant.
Examples:
# Best speed (compared to the other levels)
compression-level 1

# Best compression
compression-level 9

# No compression. Only useful for testing as the added header
# slightly increases the amount of data that has to be sent.
# If your benchmark shows that using this compression level
# is superior to using no compression at all, the benchmark
# is likely to be flawed.
compression-level 0
7.6.15. client-header-order
Specifies:
The order in which client headers are sorted before forwarding them.
Type of value:
Client header names delimited by spaces or tabs
Default value:
None
Notes:
By default
Privoxy
leaves the client headers in the order they were
sent by the client. Headers are modified in-place, new headers are added at the end of the already
existing headers.
The header order can be used to fingerprint client requests independently of other headers like the
User-Agent.
This directive allows to sort the headers differently to better mimic a different User-Agent. Client
headers will be emitted in the order given, headers whose name isn't explicitly specified are added at
the end.
Note that sorting headers in an uncommon way will make fingerprinting actually easier. Encrypted
headers are not affected by this directive unless
https-inspection
is enabled.
7.6.16. client-specific-tag
Specifies:
The name of a tag that will always be set for clients that requested it through the webinterface.
Type of value:
Tag name followed by a description that will be shown in the
webinterface
Default value:
None
Notes:
Client-specific tags allow Privoxy admins to create different profiles and let the users chose which
one they want without impacting other users.
One use case is allowing users to circumvent certain blocks without having to allow them to circumvent
all blocks. This is not possible with the
enable-remote-toggle
feature
because it would bluntly disable all blocks for all users and also affect other actions like
filters. It also is set globally which renders it useless in most multi-user setups.
After a client-specific tag has been defined with the client-specific-tag directive, action sections
can be activated based on the tag by using a
CLIENT-TAG
pattern. The CLIENT-TAG pattern is evaluated at the same priority as URL patterns,
as a result the last matching pattern wins. Tags that are created based on client or server headers are
evaluated later on and can overrule CLIENT-TAG and URL patterns!
The tag is set for all requests that come from clients that requested it to be set. Note that
"clients" are differentiated by IP address, if the IP address changes the tag has to be requested
again.
Clients can request tags to be set by using the CGI interface
. The
specific tag description is only used on the web page and should be phrased in away that the user
understands the effect of the tag.
Examples:
# Define a couple of tags, the described effect requires action sections
# that are enabled based on CLIENT-TAG patterns.
client-specific-tag circumvent-blocks Overrule blocks but do not affect other actions
client-specific-tag disable-content-filters Disable content-filters but do not affect other actions
client-specific-tag overrule-redirects Overrule redirect sections
client-specific-tag allow-cookies Do not crunch cookies in either direction
client-specific-tag change-tor-socks-port Change forward-socks5 settings to use a different Tor socks port (and circuits)
client-specific-tag no-https-inspection Disable HTTPS inspection
client-specific-tag no-tls-verification Don't verify certificates when http-inspection is enabled
7.6.17. client-tag-lifetime
Specifies:
How long a temporarily enabled tag remains enabled.
Type of value:
Time in seconds.
Default value:
60
Notes:
In case of some tags users may not want to enable them permanently, but only for a short amount of
time, for example to circumvent a block that is the result of an overly-broad URL pattern.
The CGI interface
therefore provides a "enable this tag temporarily"
option. If it is used, the tag will be set until the client-tag-lifetime is over.
Example:
# Increase the time to life for temporarily enabled tags to 3 minutes
client-tag-lifetime 180
7.6.18.
trust-x-forwarded-for
Specifies:
Whether or not Privoxy should use IP addresses specified with the X-Forwarded-For header
Type of value:
0 or one
Default value:
Notes:
If clients reach Privoxy through another proxy, for example a load balancer, Privoxy can't tell the
client's IP address from the connection. If multiple clients use the same proxy, they will share the same
client tag settings which is usually not desired.
This option lets Privoxy use the X-Forwarded-For header value as client IP address. If the proxy sets
the header, multiple clients using the same proxy do not share the same client tag settings.
This option should only be enabled if Privoxy can only be reached through a proxy and if the proxy can
be trusted to set the header correctly. It is recommended that ACL are used to make sure only trusted
systems can reach Privoxy.
If access to Privoxy isn't limited to trusted systems, this option would allow malicious clients to
change the client tags for other clients or increase Privoxy's memory requirements by registering lots of
client tag settings for clients that don't exist.
Example:
# Allow systems that can reach Privoxy to provide the client
# IP address with a X-Forwarded-For header.
trust-x-forwarded-for 1
7.6.19. receive-buffer-size
Specifies:
The size of the buffer Privoxy uses to receive data from the server.
Type of value:
Size in bytes
Default value:
5000
Notes:
Increasing the receive-buffer-size increases Privoxy's memory usage but can lower the number of
context switches and thereby reduce the cpu usage and potentially increase the throughput.
This is mostly relevant for fast network connections and large downloads that don't require
filtering.
Reducing the buffer size reduces the amount of memory Privoxy needs to handle the request but
increases the number of systemcalls and may reduce the throughput.
A dtrace command like:
"sudo dtrace -n 'syscall::read:return /execname ==
"privoxy"/ { @[execname] = llquantize(arg0, 10, 0, 5, 20); @m = max(arg0)}'"
can be used to
properly tune the receive-buffer-size. On systems without dtrace, strace or truss may be used as less
convenient alternatives.
If the buffer is too large it will increase Privoxy's memory footprint without any benefit. As the
memory is (currently) cleared before using it, a buffer that is too large can actually reduce the
throughput.
Example:
# Increase the receive buffer size
receive-buffer-size 32768
7.7. HTTPS
Inspection
HTTPS inspection allows to filter encrypted requests and responses. This is only supported when
Privoxy
has been built with FEATURE_HTTPS_INSPECTION. If you aren't sure if your version
supports it, have a look at
7.7.1. ca-directory
Specifies:
Directory with the CA key, the CA certificate and the trusted CAs file.
Type of value:
Text
Default value:
./CA
Effect if unset:
Default value is used.
Notes:
This directive specifies the directory where the CA key, the CA certificate and the trusted CAs file
are located.
The permissions should only let
Privoxy
and the
Privoxy
admin access the directory.
Example:
ca-directory /usr/local/etc/privoxy/CA
7.7.2. ca-cert-file
Specifies:
The CA certificate file in ".crt" format.
Type of value:
Text
Default value:
cacert.crt
Effect if unset:
Default value is used.
Notes:
This directive specifies the name of the CA certificate file in ".crt" format.
The file is used by
Privoxy
to generate website certificates when
https inspection is enabled with the
https-inspection
action.
Privoxy
clients should import the certificate so that they can
validate the generated certificates.
The file can be generated with:
openssl req -new -x509 -extensions v3_ca -keyout
cakey.pem -out cacert.crt -days 3650
Example:
ca-cert-file root.crt
7.7.3. ca-key-file
Specifies:
The CA key file in ".pem" format.
Type of value:
Text
Default value:
cacert.pem
Effect if unset:
Default value is used.
Notes:
This directive specifies the name of the CA key file in ".pem" format. The
ca-cert-file section
contains a command to generate it.
The CA key is used by
Privoxy
to sign generated certificates.
Access to the key should be limited to Privoxy.
Example:
ca-key-file cakey.pem
7.7.4. ca-password
Specifies:
The password for the CA keyfile.
Type of value:
Text
Default value:
Empty string
Effect if unset:
Default value is used.
Notes:
This directive specifies the password for the CA keyfile that is used when Privoxy generates
certificates for intercepted requests.
Warning
Note that the password is shown on the CGI page so don't reuse an important one.
If disclosure of the password is a compliance issue consider blocking the relevant CGI
requests after enabling the
enforce-blocks
and
allow-cgi-request-crunching
Example:
ca-password blafasel
7.7.5.
certificate-directory
Specifies:
Directory to save generated keys and certificates.
Type of value:
Text
Default value:
./certs
Effect if unset:
Default value is used.
Notes:
This directive specifies the directory where generated TLS/SSL keys and certificates are saved when
https inspection is enabled with the
https-inspection
action.
The keys and certificates currently have to be deleted manually when changing the
ca-cert-file
and the
ca-cert-key
The permissions should only let
Privoxy
and the
Privoxy
admin access the directory.
Warning
Privoxy
currently does not garbage-collect obsolete keys and
certificates and does not keep track of how may keys and certificates exist.
Privoxy
admins should monitor the size of the directory
and/or make sure there is sufficient space available. A cron job to limit the number of keys and
certificates to a certain number may be worth considering.
Example:
certificate-directory /usr/local/var/privoxy/certs
7.7.6. cipher-list
Specifies:
A list of ciphers to use in TLS handshakes
Type of value:
Text
Default value:
None
Effect if unset:
A default value is inherited from the TLS library.
Notes:
This directive allows to specify a non-default list of ciphers to use in TLS handshakes with clients
and servers.
Ciphers are separated by colons. Which ciphers are supported depends on the TLS library. When using
OpenSSL, unsupported ciphers are skipped. When using MbedTLS they are rejected.
Warning
Specifying an unusual cipher list makes fingerprinting easier. Note that the default list
provided by the TLS library may be unusual when compared to the one used by modern browsers as
well.
Examples:
# Explicitly set a couple of ciphers with names used by MbedTLS
cipher-list cipher-list TLS-ECDHE-RSA-WITH-CHACHA20-POLY1305-SHA256:\
TLS-ECDHE-ECDSA-WITH-CHACHA20-POLY1305-SHA256:\
TLS-DHE-RSA-WITH-CHACHA20-POLY1305-SHA256:\
TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256:\
TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384:\
TLS-ECDHE-ECDSA-WITH-AES-256-CCM:\
TLS-ECDHE-ECDSA-WITH-AES-256-CCM-8:\
TLS-ECDHE-ECDSA-WITH-AES-128-CCM:\
TLS-ECDHE-ECDSA-WITH-AES-128-CCM-8:\
TLS-ECDHE-ECDSA-WITH-CAMELLIA-128-GCM-SHA256:\
TLS-ECDHE-ECDSA-WITH-CAMELLIA-256-GCM-SHA384:\
TLS-ECDHE-RSA-WITH-AES-128-GCM-SHA256:\
TLS-ECDHE-RSA-WITH-AES-256-GCM-SHA384:\
TLS-ECDHE-RSA-WITH-CAMELLIA-128-GCM-SHA256:\
TLS-ECDHE-RSA-WITH-CAMELLIA-256-GCM-SHA384:\
TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:\
TLS-DHE-RSA-WITH-AES-128-GCM-SHA256:\
TLS-DHE-RSA-WITH-AES-256-CCM:\
TLS-DHE-RSA-WITH-AES-256-CCM-8:\
TLS-DHE-RSA-WITH-AES-128-CCM:\
TLS-DHE-RSA-WITH-AES-128-CCM-8:\
TLS-DHE-RSA-WITH-CAMELLIA-128-GCM-SHA256:\
TLS-DHE-RSA-WITH-CAMELLIA-256-GCM-SHA384:\
TLS-ECDH-RSA-WITH-AES-128-GCM-SHA256:\
TLS-ECDH-RSA-WITH-AES-256-GCM-SHA384:\
TLS-ECDH-RSA-WITH-CAMELLIA-128-GCM-SHA256:\
TLS-ECDH-RSA-WITH-CAMELLIA-256-GCM-SHA384:\
TLS-ECDH-ECDSA-WITH-AES-128-GCM-SHA256:\
TLS-ECDH-ECDSA-WITH-AES-256-GCM-SHA384:\
TLS-ECDH-ECDSA-WITH-CAMELLIA-128-GCM-SHA256:\
TLS-ECDH-ECDSA-WITH-CAMELLIA-256-GCM-SHA384
# Explicitly set a couple of ciphers with names used by OpenSSL
cipher-list ECDHE-RSA-AES256-GCM-SHA384:\
ECDHE-ECDSA-AES256-GCM-SHA384:\
DH-DSS-AES256-GCM-SHA384:\
DHE-DSS-AES256-GCM-SHA384:\
DH-RSA-AES256-GCM-SHA384:\
DHE-RSA-AES256-GCM-SHA384:\
ECDH-RSA-AES256-GCM-SHA384:\
ECDH-ECDSA-AES256-GCM-SHA384:\
ECDHE-RSA-AES128-GCM-SHA256:\
ECDHE-ECDSA-AES128-GCM-SHA256:\
DH-DSS-AES128-GCM-SHA256:\
DHE-DSS-AES128-GCM-SHA256:\
DH-RSA-AES128-GCM-SHA256:\
DHE-RSA-AES128-GCM-SHA256:\
ECDH-RSA-AES128-GCM-SHA256:\
ECDH-ECDSA-AES128-GCM-SHA256:\
ECDHE-RSA-AES256-GCM-SHA384:\
AES128-SHA
# Use keywords instead of explicitly naming the ciphers (Does not work with MbedTLS)
cipher-list ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
7.7.7. trusted-cas-file
Specifies:
The trusted CAs file in ".pem" format.
Type of value:
File name relative to ca-directory
Default value:
trustedCAs.pem
Effect if unset:
Default value is used.
Notes:
This directive specifies the trusted CAs file that is used when validating certificates for
intercepted TLS/SSL requests.
An example file can be downloaded from
. If you want to create the file yourself, please see:
Example:
trusted-cas-file trusted_cas_file.pem
7.8. 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
If
"log-messages"
is set to 1,
Privoxy
copies log
messages to the console window. The log detail depends on the
debug
directive.
log-messages
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
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
The font used in the console window:
log-font-name Comic Sans
MS
Font size used in the console window:
log-font-size
"show-on-task-bar"
controls whether or not
Privoxy
will appear as a button on the Task bar when minimized:
show-on-task-bar
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
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
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