path: root/doc/tor.1.in

.TH TOR 1 "January 2006" "TOR"
.SH NAME
tor \- The second-generation onion router
.SH SYNOPSIS
.B tor
[\fIOPTION value\fR]...
.SH DESCRIPTION
.I tor
is a connection-oriented anonymizing communication
service. Users choose a source-routed path through a set of nodes, and
negotiate a "virtual circuit" through the network, in which each node
knows its predecessor and successor, but no others. Traffic flowing down
the circuit is unwrapped by a symmetric key at each node, which reveals
the downstream node.
.PP
Basically \fItor\fR provides a distributed network of servers ("onion
routers"). Users bounce their TCP streams -- web traffic, ftp, ssh, etc --
around the routers, and recipients, observers, and even the routers
themselves have difficulty tracking the source of the stream.
.SH OPTIONS
\fB-h, -help\fP
Display a short help message and exit.
.LP
.TP
\fB-f \fR\fIFILE\fP
FILE contains further "option value" pairs. (Default: @CONFDIR@/torrc)
.LP
.TP
Other options can be specified either on the command-line (\fI--option
value\fR), or in the configuration file (\fIoption value\fR).
Options are case-insensitive.
.LP
.TP
\fBBandwidthRate \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
A token bucket limits the average incoming bandwidth on this node to
the specified number of bytes per second. (Default: 3 MB)
.LP
.TP
\fBBandwidthBurst \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
Limit the maximum token bucket size (also known as the burst) to the
given number of bytes. (Default: 6 MB)
.LP
.TP
\fBMaxAdvertisedBandwidth \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
If set, we will not advertise more than this amount of bandwidth for our
BandwidthRate. Server operators who want to reduce the number of clients
who ask to build circuits through them (since this is proportional to
advertised bandwidth rate) can thus reduce the CPU demands on their
server without impacting network performance.
.LP
.TP
\fBConnLimit \fR\fINUM\fP
The minimum number of file descriptors that must be available to
the Tor process before it will start. Tor will ask the OS for as
many file descriptors as the OS will allow (you can find this
by "ulimit -H -n"). If this number is less than ConnLimit, then
Tor will refuse to start.

You probably don't need to adjust this. It has no effect on
Windows since that platform lacks getrlimit(). (Default: 1000)
.LP
.TP
\fBControlPort \fR\fIPort\fP
If set, Tor will accept connections on
this port, and allow those connections to control the Tor process using the
Tor Control Protocol (described in control-spec.txt).  Note: unless you also
specify one of \fBHashedControlPassword\fP or \fBCookieAuthentication\fP,
setting this option will cause Tor to allow any process on the local host to
control it.
.LP
.TP
\fBControlListenAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind the controller listener to this address. If you specify a port,
bind to this port rather than the one specified in ControlPort. We
strongly recommend that you leave this alone unless you know what you're
doing, since giving attackers access to your control listener is really
dangerous. (Default: 127.0.0.1)
This directive can be specified multiple times to bind to multiple
addresses/ports.
.LP
.TP
\fBHashedControlPassword \fR\fIhashed_password\fP
Don't allow any connections on the control port except when the other process
knows the password whose one-way hash is \fIhashed_password\fP.  You can
compute the hash of a password by running "tor --hash-password
\fIpassword\fP".
.LP
.TP
\fBCookieAuthentication \fR\fB0\fR|\fB1\fP
If this option is set to 1, don't allow any connections on the control port
except when the connecting process knows the contents of a file named
"control_auth_cookie", which Tor will create in its data directory.  This
authentication methods should only be used on systems with good filesystem
security. (Default: 0)
.LP
.TP
\fBDataDirectory \fR\fIDIR\fP
Store working data in DIR (Default: @LOCALSTATEDIR@/lib/tor)
.LP
.TP
\fBDirServer \fR[\fInickname\fR] [\fBflags\fR] \fIaddress\fR\fB:\fIport fingerprint\fP
Use a nonstandard authoritative directory server at the provided
address and port, with the specified key fingerprint.  This option can
be repeated many times, for multiple authoritative directory
servers.  Flags are separated by spaces, and determine what kind of an
authority this directory is.  By default, every authority is authoritative
for current ("v2")-style directories, unless the "no-v2" flag is given.  If the "v1" flags is provided, Tor will use this server as an
authority for old-style (v1) directories as well.  (Only directory mirrors
care about this.)  Tor will use this server as an authority for hidden
service information if the "hs" flag is set, or if the "v1" flag is set and
the "no-hs" flag is \fBnot\fP set.
If no \fBdirserver\fP line is given, Tor will use the default
directory servers.  NOTE: this option is intended
for setting up a private Tor network with its own directory authorities.  If
you use it, you will be distinguishable from other users, because you won't
believe the same authorities they do.
.LP
.TP
\fBFetchHidServDescriptors \fR\fB0\fR|\fB1\fR\fP
If set to 0, Tor will never fetch any hidden service descriptors from
the rendezvous directories. This option is only useful if you're using
a Tor controller that handles hidserv fetches for you.
(Default: 1)
.LP
.TP
\fBFetchServerDescriptors \fR\fB0\fR|\fB1\fR\fP
If set to 0, Tor will never fetch any network status summaries or server
descriptors from the directory servers. This option is only useful if
you're using a Tor controller that handles directory fetches for you.
(Default: 1)
.LP
.TP
\fBFetchUselessDescriptors \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor will fetch every non-obsolete descriptor from the
authorities that it hears about. Otherwise, it will avoid fetching
useless descriptors, for example for routers that are not running.
This option is useful if you're using the contributed "exitlist"
script to enumerate Tor nodes that exit to certain addresses.
(Default: 0)
.LP
.TP
\fBGroup \fR\fIGID\fP
On startup, setgid to this user.
.LP
.TP
\fBHttpProxy\fR \fIhost\fR[:\fIport\fR]\fP
Tor will make all its directory requests through this host:port
(or host:80 if port is not specified),
rather than connecting directly to any directory servers.
.LP
.TP
\fBHttpProxyAuthenticator\fR \fIusername:password\fP
If defined, Tor will use this username:password for Basic Http proxy
authentication, as in RFC 2617. This is currently the only form of
Http proxy authentication that Tor supports; feel free to submit a
patch if you want it to support others.
.LP
.TP
\fBHttpsProxy\fR \fIhost\fR[:\fIport\fR]\fP
Tor will make all its OR (SSL) connections through this host:port
(or host:443 if port is not specified), via HTTP CONNECT rather than
connecting directly to servers.  You may want to set \fBFascistFirewall\fR
to restrict the set of ports you might try to connect to, if your Https
proxy only allows connecting to certain ports.
.LP
.TP
\fBHttpsProxyAuthenticator\fR \fIusername:password\fP
If defined, Tor will use this username:password for Basic Https proxy
authentication, as in RFC 2617. This is currently the only form of
Https proxy authentication that Tor supports; feel free to submit a
patch if you want it to support others.
.LP
.TP
\fBKeepalivePeriod \fR\fINUM\fP
To keep firewalls from expiring connections, send a padding keepalive
cell every NUM seconds on open connections that are in use. If the
connection has no open circuits, it will instead be closed after NUM
seconds of idleness. (Default: 5 minutes)
.LP
.TP
\fBLog \fR\fIminSeverity\fR[-\fImaxSeverity\fR] \fBstderr\fR|\fBstdout\fR|\fBsyslog\fR\fP
Send all messages between \fIminSeverity\fR and \fImaxSeverity\fR to
the standard output stream, the standard error stream, or to the system
log. (The "syslog" value is only supported on Unix.)  Recognized
severity levels are debug, info, notice, warn, and err.  We advise using
"notice" in most cases, since anything more verbose may provide sensitive
information to an attacker who obtains the logs.  If only one
severity level is given, all messages of that level or higher will be
sent to the listed destination.
.LP
.TP
\fBLog \fR\fIminSeverity\fR[-\fImaxSeverity\fR] \fBfile\fR \fIFILENAME\fP
As above, but send log messages to the listed filename.  The "Log"
option may appear more than once in a configuration file.  Messages
are sent to all the logs that match their severity level.
.LP
.TP
\fBOutboundBindAddress \fR\fIIP\fP
Make all outbound connections originate from the IP address specified.  This
is only useful when you have multiple network interfaces, and you want all
of Tor's outgoing connections to use a single one.
.LP
.TP
\fBPidFile \fR\fIFILE\fP
On startup, write our PID to FILE. On clean shutdown, remove FILE.
.LP
.TP
\fBProtocolWarnings \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will log with severity 'warn' various cases of other parties
not following the Tor specification. Otherwise, they are logged with
severity 'info'. (Default: 0)
.LP
.TP
\fBRunAsDaemon \fR\fB0\fR|\fB1\fR\fP
If 1, Tor forks and daemonizes to the background. This option has
no effect on Windows; instead you should use the --service command-line
option. (Default: 0)
.LP
.TP
\fBSafeLogging \fR\fB0\fR|\fB1\fP
If 1, Tor replaces potentially sensitive strings in the logs
(e.g. addresses) with the string [scrubbed]. This way logs can still be
useful, but they don't leave behind personally identifying information
about what sites a user might have visited. (Default: 1)
.LP
.TP
\fBUser \fR\fIUID\fP
On startup, setuid to this user.
.LP
.TP
\fBHardwareAccel \fR\fB0\fR|\fB1\fP
If non-zero, try to use crypto hardware acceleration when
available. This is untested and probably buggy. (Default: 0)

.SH CLIENT OPTIONS
.PP
The following options are useful only for clients (that is, if \fBSocksPort\fP is non-zero):
.LP
.TP
\fBAllowInvalidNodes\fR \fBentry\fR|\fBexit\fR|\fBmiddle\fR|\fBintroduction\fR|\fBrendezvous\fR|...\fP
If some Tor servers are obviously not working right, the directory
authorities can manually mark them as invalid, meaning that it's not
recommended you use them for entry or exit positions in your circuits. You
can opt to use them in some circuit positions, though. The default is
"middle,rendezvous", and other choices are not advised.
.LP
.TP
\fBCircuitBuildTimeout \fR\fINUM\fP
Try for at most NUM seconds when building circuits. If the circuit
isn't open in that time, give up on it.
(Default: 1 minute.)
.LP
.TP
\fBCircuitIdleTimeout \fR\fINUM\fP
If we have keept a clean (never used) circuit around for NUM seconds,
then close it. This way when the Tor client is entirely idle, it can
expire all of its circuits, and then expire its TLS connections. Also,
if we end up making a circuit that is not useful for exiting any of
the requests we're receiving, it won't forever take up a slot in the
circuit list.
(Default: 1 hour.)
.LP
.TP
\fBClientOnly \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor will under no circumstances run as a server. The default
is to run as a client unless ORPort is configured.  (Usually,
you don't need to set this; Tor is pretty smart at figuring out whether
you are reliable and high-bandwidth enough to be a useful server.)
(Default: 0)
.LP
.TP
\fBExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of nodes to never use when building a circuit.
.LP
.TP
\fBEntryNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the first hop in the circuit.
These are treated only as preferences unless StrictEntryNodes (see
below) is also set.
.LP
.TP
\fBExitNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the last hop in the circuit.
These are treated only as preferences unless StrictExitNodes (see
below) is also set.
.LP
.TP
\fBStrictEntryNodes \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will never use any nodes besides those listed in "EntryNodes" for
the first hop of a circuit.
.LP
.TP
\fBStrictExitNodes \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will never use any nodes besides those listed in "ExitNodes" for
the last hop of a circuit.
.LP
.TP
\fBFascistFirewall \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will only create outgoing connections to ORs running on ports that
your firewall allows (defaults to 80 and 443; see \fBFirewallPorts\fR).  This will
allow you to run Tor as a client behind a firewall with restrictive policies,
but will not allow you to run as a server behind such a firewall.
This option is deprecated; use
ReachableAddresses instead.
.LP
.TP
\fBFirewallPorts \fR\fIPORTS\fP
A list of ports that your firewall allows you to connect to.  Only
used when \fBFascistFirewall\fR is set. This option is deprecated; use
ReachableAddresses instead. (Default: 80, 443)
.LP
.TP
\fBReachableAddresses \fR\fIADDR\fP[\fB/\fP\fIMASK\fP][:\fIPORT\fP]...\fP
A comma-separated list of IP addresses and ports that your firewall allows you
to connect to. The format is as
for the addresses in ExitPolicy, except that "accept" is understood
unless "reject" is explicitly provided.  For example, 'ReachableAddresses
99.0.0.0/8, reject 18.0.0.0/8:80, accept *:80' means that your
firewall allows connections to everything inside net 99, rejects port
80 connections to net 18, and accepts connections to port 80 otherwise.
(Default: 'accept *:*'.)
.LP
.TP
\fBReachableDirAddresses \fR\fIADDR\fP[\fB/\fP\fIMASK\fP][:\fIPORT\fP]...\fP
Like \fBReachableAddresses\fP, a list of addresses and ports.  Tor will obey
these restrictions when fetching directory information, using standard HTTP
GET requests. If not set explicitly then the value of \fBReachableAddresses\fP
is used.  If \fBHttpProxy\fR is set then these connections will go through that
proxy.
.LP
.TP
\fBReachableORAddresses \fR\fIADDR\fP[\fB/\fP\fIMASK\fP][:\fIPORT\fP]...\fP
Like \fBReachableAddresses\fP, a list of addresses and ports.  Tor will obey
these restrictions when connecting to Onion Routers, using TLS/SSL.  If not set
explicitly then the value of \fBReachableAddresses\fP is used. If
\fBHttpsProxy\fR is set then these connections will go through that proxy.

The separation between \fBReachableORAddresses\fP and
\fBReachableDirAddresses\fP is only interesting when you are connecting through
proxies (see \fBHttpProxy\fR and \fBHttpsProxy\fR).  Most proxies limit TLS
connections (which Tor uses to connect to Onion Routers) to port 443, and some
limit HTTP GET requests (which Tor uses for fetching directory information) to
port 80.
.LP
.TP
\fBLongLivedPorts \fR\fIPORTS\fP
A list of ports for services that tend to have long-running connections
(e.g. chat and interactive shells). Circuits for streams that use these
ports will contain only high-uptime nodes, to reduce the chance that a
node will go down before the stream is finished.
(Default: 21, 22, 706, 1863, 5050, 5190, 5222, 5223, 6667, 8300)
.LP
.TP
\fBMapAddress\fR \fIaddress\fR \fInewaddress\fR
When a request for address arrives to Tor, it will rewrite it to
newaddress before processing it. For example, if you always want
connections to www.indymedia.org to exit via \fItorserver\fR (where
\fItorserver\fR is the nickname of the server),
use "MapAddress www.indymedia.org www.indymedia.org.torserver.exit".
.LP
.TP
\fBNewCircuitPeriod \fR\fINUM\fP
Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds)
.LP
.TP
\fBMaxCircuitDirtiness \fR\fINUM\fP
Feel free to reuse a circuit that was first used at most NUM seconds ago,
but never attach a new stream to a circuit that is too old.
(Default: 10 minutes)
.LP
.TP
\fBNodeFamily \fR\fInickname\fR,\fInickname\fR,\fI...\fP
The named Tor servers constitute a "family" of similar or co-administered
servers, so never use any two of them in the same circuit. Defining a
NodeFamily is only needed when a server doesn't list the family itself
(with MyFamily). This option can be used multiple times.
.LP
.TP
\fBEnforceDistinctSubnets \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will not put two servers whose IP addresses are "too
close" on the same circuit.  Currently, two addresses are
"too close" if they lie in the same /16 range. (Default: 1)

.\" \fBPathlenCoinWeight \fR\fI0.0-1.0\fP
.\" Paths are 3 hops plus a geometric distribution centered around this coinweight.
.\" Must be >=0.0 and <1.0. (Default: 0.3) NOT USED CURRENTLY
.\" .TP
.LP
.TP
\fBRendNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the rendezvous point, if possible.
.LP
.TP
\fBRendExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of nodes to never use when choosing a rendezvous point.
.LP
.TP
\fBSocksPort \fR\fIPORT\fP
Advertise this port to listen for connections from Socks-speaking
applications.  Set this to 0 if you don't want to allow application
connections. (Default: 9050)
.LP
.TP
\fBSocksListenAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind to this address to listen for connections from Socks-speaking
applications. (Default: 127.0.0.1) You can also specify a port
(e.g. 192.168.0.1:9100).
This directive can be specified multiple times to bind to multiple
addresses/ports.
.LP
.TP
\fBSocksPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an entrance policy for this server, to limit who can connect to the
Socks ports.
The policies have the same form as exit policies below.
.LP
.TP
\fBSocksTimeout \fR\fINUM\fP
Let a socks connection wait NUM seconds unattached before we fail it.
(Default: 2 minutes.)
.LP
.TP
\fBTestVia \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of nodes to prefer for your middle hop when building testing
circuits. This option is mainly for debugging reachability problems.
.LP
.TP
\fBTrackHostExits \fR\fIhost\fR,\fI.domain\fR,\fI...\fR\fP
For each value in the comma separated list, Tor will track recent connections
to hosts that match this value and attempt to
reuse the same exit node for each. If the value is prepended with a '.', it is
treated as matching an entire domain. If one of the values is just a '.', it
means match everything. This option is useful if you frequently connect to
sites that will expire all your authentication cookies (ie log you out) if
your IP address changes. Note that this option does have the disadvantage of
making it more clear that a given history is
associated with a single user. However, most people who would wish to observe
this will observe it through cookies or other protocol-specific means anyhow.
.LP
.TP
\fBTrackHostExitsExpire \fR\fINUM\fP
Since exit servers go up and down, it is desirable to expire the association
between host and exit server after NUM seconds. The default
is 1800 seconds (30 minutes).
.LP
.TP
\fBUseEntryGuards \fR\fB0\fR|\fB1\fR\fP
If this option is set to 1, we pick a few long-term entry servers, and
try to stick with them.  This is desirable because
constantly changing servers increases the odds that an adversary who owns
some servers will observe a fraction of your paths.
(Defaults to 1.)
.LP
.TP
\fBNumEntryGuards \fR\fINUM\fP
If UseEntryGuards is set to 1, we will try to pick a total of NUM routers
as long-term entries for our circuits.
(Defaults to 3.)
.LP
.TP
\fBSafeSocks \fR\fB0\fR|\fB1\fR\fP
When this option is enabled, Tor will reject application connections that
use unsafe variants of the socks protocol -- ones that only provide an
IP address, meaning the application is doing a DNS resolve first.
Specifically, these are socks4 and socks5 when not doing remote DNS.
(Defaults to 0.)
.LP
.TP
\fBTestSocks \fR\fB0\fR|\fB1\fR\fP
When this option is enabled, Tor will make a notice-level log entry for
each connection to the Socks port indicating whether the request used
a safe socks protocol or an unsafe one (see above entry on SafeSocks).
This helps to determine whether an application using Tor is possibly
leaking DNS requests.
(Default: 0)
.LP
.TP
\fBVirtualAddrNetwork \fR\fIAddress\fB/\fIbits\fP
When a controller asks for a virtual (unused) address with the
'MAPADDRESS' command, Tor picks an unassigned address from this range.
(Default: 127.192.0.0/10)

.SH SERVER OPTIONS
.PP
The following options are useful only for servers (that is, if \fBORPort\fP is non-zero):
.LP
.TP
\fBAddress \fR\fIaddress\fP
The IP or fqdn of this server (e.g. moria.mit.edu). You can leave this
unset, and Tor will guess your IP.
.LP
.TP
\fBAssumeReachable \fR\fB0\fR|\fB1\fR\fP
This option is used when bootstrapping a new Tor network. If set to 1,
don't do self-reachability testing; just upload your server descriptor
immediately. If \fBAuthoritativeDirectory\fP is also set, this option
instructs the dirserver to bypass remote reachability testing too and
list all connected servers as running.
.LP
.TP
\fBContactInfo \fR\fIemail_address\fP
Administrative contact information for server. This line might get
picked up by spam harvesters, so you may want to obscure the fact
that it's an email address.
.LP
.TP
\fBExitPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an exit policy for this server. Each policy is of the form
"\fBaccept\fP|\fBreject\fP \fIADDR\fP[\fB/\fP\fIMASK\fP]\fB[:\fP\fIPORT\fP]".
If \fB/\fP\fIMASK\fP is omitted then this policy just applies to the host
given.  Instead of giving a host or network you can also use "\fB*\fP" to
denote the universe (0.0.0.0/0).  \fIPORT\fP can be a single port number,
an interval of ports "\fIFROM_PORT\fP\fB-\fP\fITO_PORT\fP", or "\fB*\fP".
If \fIPORT\fP is omitted, that means "\fB*\fP".

For example, "accept 18.7.22.69:*,reject 18.0.0.0/8:*,accept *:*" would
reject any traffic destined for MIT except for web.mit.edu, and
accept anything else.

To specify all internal and link-local networks (including 0.0.0.0/8,
169.254.0.0/16, 127.0.0.0/8, 192.168.0.0/16, 10.0.0.0/8, and
172.16.0.0/12), you can use the "private" alias instead of an address.
These addresses are rejected by default (at the beginning of your
exit policy) unless you set the ExitPolicyRejectPrivate config option
to 0. For example, once you've done that, you could allow HTTP to
127.0.0.1 and block all other connections to internal networks with
"accept
127.0.0.1:80,reject private:*".  See RFC 1918 and RFC 3330 for more
details about internal and reserved IP address space.

This directive can be specified multiple times so you don't have to put
it all on one line.

Policies are considered first to last, and the first match wins. If
you want to _replace_ the default exit policy, end your exit policy with
either a reject *:* or an accept *:*. Otherwise, you're _augmenting_
(prepending to) the default exit policy. The default exit policy is:
.PD 0
.RS 12
.IP "reject *:25"
.IP "reject *:119"
.IP "reject *:135-139"
.IP "reject *:445"
.IP "reject *:465"
.IP "reject *:587"
.IP "reject *:1214"
.IP "reject *:4661-4666"
.IP "reject *:6346-6429"
.IP "reject *:6699"
.IP "reject *:6881-6999"
.IP "accept *:*"
.RE
.PD
.LP
.TP
\fBExitPolicyRejectPrivate \fR\fB0\fR|\fB1\fR\fP
Reject all private (local) networks at the beginning of your exit
policy. See above entry on ExitPolicy. (Default: 1)
.LP
.TP
\fBMaxOnionsPending \fR\fINUM\fP
If you have more than this number of onionskins queued for decrypt, reject new ones. (Default: 100)
.LP
.TP
\fBMyFamily \fR\fInickname\fR,\fInickname\fR,\fI...\fP
Declare that this Tor server is controlled or administered by a group
or organization identical or similar to that of the other named servers.
When two servers both declare that they are in the same 'family', Tor clients
will not use them in the same circuit.  (Each server only needs to list the
other servers in its family; it doesn't need to list itself, but it won't hurt.)
.LP
.TP
\fBNickname \fR\fIname\fP
Set the server's nickname to 'name'. Nicknames must be between 1
and 19 characters inclusive, and must contain only the characters
[a-zA-Z0-9].
.LP
.TP
\fBNumCPUs \fR\fInum\fP
How many processes to use at once for decrypting onionskins. (Default: 1)
.LP
.TP
\fBORPort \fR\fIPORT\fP
Advertise this port to listen for connections from Tor clients and servers.
.LP
.TP
\fBORListenAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind to this IP address to listen for connections from Tor clients and
servers. If you specify a port, bind to this port rather than the one
specified in ORPort. (Default: 0.0.0.0)
This directive can be specified multiple times to bind to multiple
addresses/ports.
.LP
.TP
\fBPublishServerDescriptor \fR\fB0\fR|\fB1\fR\fP
If set to 0, Tor will act as a server if you have an ORPort
defined, but it will not publish its descriptor to the dirservers. This
option is useful if you're testing out your server, or if you're using
a Tor controller that handles directory publishing for you.
(Default: 1)
.LP
.TP
\fBRedirectExit \fR\fIpattern target\fP
Whenever an outgoing connection tries to connect to one of a given set
of addresses, connect to \fItarget\fP (an \fIaddress:port\fP pair) instead.
The address
pattern is given in the same format as for an exit policy.  The
address translation applies after exit policies are applied.  Multiple
\fBRedirectExit\fP options can be used: once any one has matched
successfully, no subsequent rules are considered.  You can specify that no
redirection is to be performed on a given set of addresses by using the
special target string "pass", which prevents subsequent rules from being
considered.
.LP
.TP
\fBShutdownWaitLength\fR \fINUM\fP
When we get a SIGINT and we're a server, we begin shutting down: we close
listeners and start refusing new circuits. After \fBNUM\fP seconds,
we exit. If we get a second SIGINT, we exit immediately.  (Default:
30 seconds)
.LP
.TP
\fBAccountingMax \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
Never send more than the specified number of bytes in a given
accounting period, or receive more than that number in the period.
For example, with AccountingMax set to 1 GB, a server could send 900 MB
and receive 800 MB and continue running. It will only hibernate once one
of the two reaches 1 GB.
When the number of bytes is exhausted, Tor will hibernate until some
time in the next accounting period.  To prevent all servers from
waking at the same time, Tor will also wait until a random point in
each period before waking up.  If you have bandwidth cost issues,
enabling hibernation is preferable to setting a low bandwidth, since it
provides users with a collection of fast servers that are up some of
the time, which is more useful than a set of slow servers that are
always "available".
.LP
.TP
\fBAccountingStart \fR\fBday\fR|\fBweek\fR|\fBmonth\fR [\fIday\fR] \fIHH:MM\fR\fP
Specify how long accounting periods last.  If \fBmonth\fP is given,
each accounting period runs from the time \fIHH:MM\fR on the
\fIday\fRth day of one month to the same day and time of the next.
(The day must be between 1 and 28.)  If \fBweek\fP is given, each
accounting period runs from the time \fIHH:MM\fR of the \fIday\fRth
day of one week to the same day and time of the next week, with Monday
as day 1 and Sunday as day 7.  If \fBday\fR is given, each accounting
period runs from the time \fIHH:MM\fR each day to the same time on the
next day.  All times are local, and given in 24-hour time.  (Defaults to
"month 1 0:00".)
.LP
.TP
\fBServerDNSResolvConfFile \fR\fIfilename\fP
Overrides the default DNS configuration with the configuration in
\fIfilename\fP.  The file format is the same as the standard Unix
"\fBresolv.conf\fP" file (7).  This option only affects name lookup for
addresses requested by clients; and only takes effect if Tor was built with
eventdns support.  (Defaults to use the system DNS configuration.)
.LP
.TP
\fBServerDNSSearchDomains \fR\fB0\fR|\fB1\fR\fP
If set to \fB1\fP, then we will search for addresses in the local search
domain.  For example, if this system is configured to believe it is in
"example.com", and a client tries to connect to "www", the client will be
connected to "www.example.com".
This option only affects name lookup for addresses requested by clients.
(Defaults to "0".)
.LP
.TP
\fBServerDNSDetectHijacking \fR\fB0\fR|\fB1\fR\fP
When this option is set to 1, we will test periodically to determine whether
our local nameservers have been configured to hijack failing DNS requests
(usually to an advertising site).  If they are, we will attempt to correct
this.  This option only affects name lookup for addresses requested by
clients; and only takes effect if Tor was built with eventdns support.
(Defaults to "1".)

.SH DIRECTORY SERVER OPTIONS
.PP
The following options are useful only for directory servers (that is, if \fBDirPort\fP is non-zero):
.LP
.TP
\fBAuthoritativeDirectory \fR\fB0\fR|\fB1\fR\fP
When this option is set to 1, Tor operates as an authoritative
directory server.  Instead of caching the directory, it generates its
own list of good servers, signs it, and sends that to the clients.
Unless the clients already have you listed as a trusted directory, you
probably do not want to set this option.  Please coordinate with the other
admins at tor-ops@freehaven.net if you think you should be a directory.
.LP
.TP
\fBV1AuthoritativeDirectory \fR\fB0\fR|\fB1\fR\fP
When this option is set in addition to \fBAuthoritativeDirectory\fP, Tor also
generates a version 1 directory (for Tor clients up to 0.1.0.x).
(As of Tor 0.1.1.12 every (v2) authoritative directory still provides most of
the v1 directory functionality, even without this option set to 1.
This however is expected to change in the future.)
.LP
.TP
\fBVersioningAuthoritativeDirectory \fR\fB0\fR|\fB1\fR\fP
When this option is set to 1, Tor adds information on
which versions of Tor are still believed safe for use to
the published directory.  Each version 1 authority is
automatically a versioning authority; version 2 authorities
provide this service optionally.  See \fBRecommendedVersions\fP,
\fBRecommendedClientVersions\fP, and \fBRecommendedServerVersions\fP.
.LP
.TP
\fBNamingAuthoritativeDirectory \fR\fB0\fR|\fB1\fR\fP
When this option is set to 1, then the server advertises that it has
opinions about nickname-to-fingerprint bindings.  It will include these
opinions in its published network-status pages, by listing servers with
the flag "Named" if a correct binding between that nickname and
fingerprint has been registered with the dirserver.  Naming dirservers
will refuse to accept or publish descriptors that contradict a
registered binding.  See \fBapproved-routers\fP in the \fBFILES\fP
section below.
.LP
.TP
\fBDirPort \fR\fIPORT\fP
Advertise the directory service on this port.
.LP
.TP
\fBDirListenAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind the directory service to this address. If you specify a port, bind
to this port rather than the one specified in DirPort. (Default: 0.0.0.0)
This directive can be specified multiple times to bind to multiple
addresses/ports.
.LP
.TP
\fBDirPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an entrance policy for this server, to limit who can connect to the
directory ports.
The policies have the same form as exit policies above.
.LP
.TP
\fBRecommendedVersions \fR\fISTRING\fP
STRING is a comma-separated list of Tor versions currently believed
to be safe. The list is included in each directory, and nodes which
pull down the directory learn whether they need to upgrade.  This
option can appear multiple times: the values from multiple lines are
spliced together.
When this is set then
\fBVersioningAuthoritativeDirectory\fP should be set too.
.LP
.TP
\fBRecommendedClientVersions \fR\fISTRING\fP
STRING is a comma-separated list of Tor versions currently believed
to be safe for clients to use.  This information is included in version 2
directories.  If this is not set then the value of \fBRecommendedVersions\fR
is used.
When this is set then
\fBVersioningAuthoritativeDirectory\fP should be set too.
.LP
.TP
\fBRecommendedServerVersions \fR\fISTRING\fP
STRING is a comma-separated list of Tor versions currently believed
to be safe for servers to use.  This information is included in version 2
directories.  If this is not set then the value of \fBRecommendedVersions\fR
is used.
When this is set then
\fBVersioningAuthoritativeDirectory\fP should be set too.
.LP
.TP
\fBDirAllowPrivateAddresses \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor will accept router descriptors with arbitrary "Address"
elements. Otherwise, if the address is not an IP or is a private IP,
it will reject the router descriptor. Defaults to 0.
.LP
.TP
\fBRunTesting \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor tries to build circuits through all of the servers it
knows about, so it can tell which are up and which are down.  This
option is only useful for authoritative directories, so you probably
don't want to use it.
.LP
.TP
\fBAuthDirInvalid \fR\fIAddressPattern\fR...\fP
Authoritative directories only. A set of address patterns for servers that
will never be listed as "valid" in any network status document that this
authority publishes.
.LP
.TP
\fBAuthDirReject \fR\fIAddressPattern\fR...\fP
Authoritative directories only.  A set of address patterns for servers that
will never be listed at all in any network status document that this
authority publishes, or accepted as an OR address in any descriptor submitted
for publication by this authority.
.LP
.TP
\fBAuthDirRejectUnlisted \fR\fB0\fR|\fB1\fR\fP
Authoritative directories only.  If set to 1, the directory server
rejects all uploaded server descriptors that aren't explicitly listed
in the fingerprints file. This acts as a "panic button" if we get
Sybiled. (Default: 0)

.SH HIDDEN SERVICE OPTIONS
.PP
The following options are used to configure a hidden service.
.LP
.TP
\fBHiddenServiceDir \fR\fIDIRECTORY\fP
Store data files for a hidden service in DIRECTORY.  Every hidden
service must have a separate directory.  You may use this option multiple
times to specify multiple services.
.LP
.TP
\fBHiddenServicePort \fR\fIVIRTPORT \fR[\fITARGET\fR]\fP
Configure a virtual port VIRTPORT for a hidden service.  You may use this
option multiple times; each time applies to the service using the most recent
hiddenservicedir.  By default, this option maps the virtual port to the
same port on 127.0.0.1.  You may override the target port, address, or both
by specifying a target of addr, port, or addr:port.
.LP
.TP
\fBHiddenServiceNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
If possible, use the specified nodes as introduction points for the hidden
service. If this is left unset, Tor will be smart and pick some reasonable
ones; most people can leave this unset.
.LP
.TP
\fBHiddenServiceExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
Do not use the specified nodes as introduction points for the hidden
service. In normal use there is no reason to set this.
.LP
.TP
\fBPublishHidServDescriptors \fR\fB0\fR|\fB1\fR\fP
If set to 0, Tor will run any hidden services you configure, but it won't
advertise them to the rendezvous directory. This option is only useful
if you're using a Tor controller that handles hidserv publishing for you.
(Default: 1)
.LP
.TP
\fBRendPostPeriod \fR\fIN\fR \fBseconds\fR|\fBminutes\fR|\fBhours\fR|\fBdays\fR|\fBweeks\fP
Every time the specified period elapses, Tor uploads any rendezvous
service descriptors to the directory servers.  This information is also
uploaded whenever it changes.  (Default: 20 minutes)

.\" UNDOCUMENTED
.\" ignoreversion

.SH SIGNALS
Tor catches the following signals:
.LP
.TP
\fBSIGTERM\fR
Tor will catch this, clean up and sync to disk if necessary, and exit.
.LP
.TP
\fBSIGINT\fR
Tor clients behave as with SIGTERM; but Tor servers will do a controlled
slow shutdown, closing listeners and waiting 30 seconds before exiting.
(The delay can be configured with the ShutdownWaitLength config option.)
.LP
.TP
\fBSIGHUP\fR
The signal instructs Tor to reload its configuration (including closing
and reopening logs), fetch a new directory, and kill and restart its
helper processes if applicable.
.LP
.TP
\fBSIGUSR1\fR
Log statistics about current connections, past connections, and
throughput.
.LP
.TP
\fBSIGUSR2\fR
Switch all logs to loglevel debug. You can go back to the old loglevels
by sending a SIGHUP.
.LP
.TP
\fBSIGCHLD\fR
Tor receives this signal when one of its helper processes has exited,
so it can clean up.
.LP
.TP
\fBSIGPIPE\fR
Tor catches this signal and ignores it.
.LP
.TP
\fBSIGXFSZ\fR
If this signal exists on your platform, Tor catches and ignores it.

.SH FILES
.LP
.TP
.B @CONFDIR@/torrc
The configuration file, which contains "option value" pairs.
.LP
.TP
.B @LOCALSTATEDIR@/lib/tor/
The tor process stores keys and other data here.
.LP
.TP
.B \fIDataDirectory\fP/approved-routers
Only for naming authoritative directory servers
(see \fBNamingAuthoritativeDirectory\fP).
This file lists nickname to identity bindings.  Each line lists a
nickname and a fingerprint seperated by whitespace.  See your
\fBfingerprint\fP file in the \fIDataDirectory\fP for an example line.
If the nickname is \fB!reject\fP then descriptors from the given
identity (fingerprint) are rejected by the authoritative directory
server. If it is \fB!invalid\fP then descriptors are accepted but marked
in the directory as not valid, that is, not recommended.
.SH SEE ALSO
.BR privoxy (1),
.BR tsocks (1),
.BR torify (1)

.BR http://tor.eff.org/

.SH BUGS
Plenty, probably. Tor is still in development. Please report them.
.SH AUTHORS
Roger Dingledine <arma@mit.edu>, Nick Mathewson <nickm@alum.mit.edu>.