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tor

NAME

tor - The second-generation onion router

SYNOPSIS

tor [OPTION value]...

DESCRIPTION

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.

Basically tor 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.

OPTIONS

-h, -help Display a short help message and exit.

-f FILE

FILE contains further "option value" pairs. (Default: /etc/tor/torrc)

--hash-password

Generates a hashed password for control port access.

--list-fingerprint

Generate your keys and output your nickname and fingerprint.

--verify-config

Verify the configuration file is valid.

--nt-service

--service [install|remove|start|stop] Manage the Tor Windows NT/2000/XP service. Current instructions can be found at http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#WinNTService

--list-torrc-options

List all valid options.

--version

Display Tor version and exit.

--quiet

Do not start Tor with a console log unless explicitly requested to do so. (By default, Tor starts out logging messages at level "notice" or higher to the console, until it has parsed its configuration.)

Other options can be specified either on the command-line (--option

value), or in the configuration file (option value or option "value"). Options are case-insensitive. C-style escaped characters are allowed inside quoted values.

BandwidthRate N bytes|KB|MB|GB|TB

A token bucket limits the average incoming bandwidth usage on this node to the specified number of bytes per second, and the average outgoing bandwidth usage to that same value. (Default: 5 MB)

BandwidthBurst N bytes|KB|MB|GB|TB

Limit the maximum token bucket size (also known as the burst) to the given number of bytes in each direction. (Default: 10 MB)

MaxAdvertisedBandwidth N bytes|KB|MB|GB|TB

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.

RelayBandwidthRate N bytes|KB|MB|GB|TB

If defined, a separate token bucket limits the average incoming bandwidth usage for _relayed traffic_ on this node to the specified number of bytes per second, and the average outgoing bandwidth usage to that same value. Relayed traffic currently is calculated to include answers to directory requests, but that may change in future versions. (Default: 0)

RelayBandwidthBurst N bytes|KB|MB|GB|TB

Limit the maximum token bucket size (also known as the burst) for _relayed traffic_ to the given number of bytes in each direction. (Default: 0)

ConnLimit NUM

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)

ConstrainedSockets 0|1

If set, Tor will tell the kernel to attempt to shrink the buffers for all sockets to the size specified in ConstrainedSockSize. This is useful for virtual servers and other environments where system level TCP buffers may be limited. If you're on a virtual server, and you encounter the "Error creating network socket: No buffer space available" message, you are likely experiencing this problem.

The preferred solution is to have the admin increase the buffer pool for the host itself via /proc/sys/net/ipv4/tcp_mem or equivalent facility; this configuration option is a second-resort.

The DirPort option should also not be used if TCP buffers are scarce. The cached directory requests consume additional sockets which exacerbates the problem.

You should not enable this feature unless you encounter the "no buffer space available" issue. Reducing the TCP buffers affects window size for the TCP stream and will reduce throughput in proportion to round trip time on long paths. (Default: 0.)

ConstrainedSockSize N bytes|KB

When ConstrainedSockets is enabled the receive and transmit buffers for all sockets will be set to this limit. Must be a value between 2048 and 262144, in 1024 byte increments. Default of 8192 is recommended.

ControlPort Port

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 HashedControlPassword or CookieAuthentication, setting this option will cause Tor to allow any process on the local host to control it. This option is required for many Tor controllers; most use the value of 9051.

ControlListenAddress IP[:PORT]

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.

ControlSocket Path

Like ControlPort, but listens on a Unix domain socket, rather than a TCP socket. (Unix and Unix-like systems only.)

HashedControlPassword hashed_password

Don't allow any connections on the control port except when the other process knows the password whose one-way hash is hashed_password. You can compute the hash of a password by running "tor --hash-password password". You can provide several acceptable passwords by using more than HashedControlPassword line.

CookieAuthentication 0|1

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 method should only be used on systems with good filesystem security. (Default: 0)

CookieAuthFile Path

If set, this option overrides the default location and file name for Tor's cookie file. (See CookieAuthentication above.)

CookieAuthFileGroupReadable 0|1|GroupName

If this option is set to 0, don't allow the filesystem group to read the cookie file. If the option is set to 1, make the cookie file readable by the default GID. [Making the file readable by other groups is not yet implemented; let us know if you need this for some reason.] (Default: 0).

DataDirectory DIR

Store working data in DIR (Default: /var/lib/tor)

DirServer [nickname] [flags] address:port fingerprint

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 not set. Tor will use this authority as a bridge authoritative directory if the "bridge" flag is set. If a flag "orport=port" is given, Tor will use the given port when opening encrypted tunnels to the dirserver. Lastly, if a flag "v3ident=fp" is given, the dirserver is a v3 directory authority whose v3 long-term signing key has the fingerprint fp.

If no dirserver 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.

AlternateDirAuthority [nickname] [flags] address:port fingerprint

AlternateHSAuthority [nickname] [flags] address:port fingerprint AlternateBridgeAuthority [nickname] [flags] address:port fingerprint As DirServer, but replaces less of the default directory authorities. Using AlternateDirAuthority replaces the default Tor directory authorities, but leaves the hidden service authorities and bridge authorities in place. Similarly, Using AlternatieHSAuthority replaces the default hidden service authorities, but not the directory or bridge authorities.

FetchDirInfoEarly 0|1 If set to 1, Tor will always fetch directory information like other directory caches, even if you don't meet the normal criteria for fetching early. Normal users should leave it off. (Default: 0)

FetchHidServDescriptors 0|1

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)

FetchServerDescriptors 0|1

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)

FetchUselessDescriptors 0|1

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)

HttpProxy host[:port]

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.

HttpProxyAuthenticator username:password

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.

HttpsProxy host[:port]

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 FascistFirewall to restrict the set of ports you might try to connect to, if your Https proxy only allows connecting to certain ports.

HttpsProxyAuthenticator username:password

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.

KeepalivePeriod NUM

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)

Log minSeverity[-maxSeverity] stderr|stdout|syslog

Send all messages between minSeverity and maxSeverity 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.

Log minSeverity[-maxSeverity] file FILENAME

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.

OutboundBindAddress IP

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.

PidFile FILE

On startup, write our PID to FILE. On clean shutdown, remove FILE.

ProtocolWarnings 0|1

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)

RunAsDaemon 0|1

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)

SafeLogging 0|1

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)

User UID

On startup, setuid to this user and setgid to their primary group.

HardwareAccel 0|1

If non-zero, try to use crypto hardware acceleration when available. This is untested and probably buggy. (Default: 0)

AvoidDiskWrites 0|1

If non-zero, try to write to disk less frequently than we would otherwise. This is useful when running on flash memory or other media that support only a limited number of writes. (Default: 0)

TunnelDirConns 0|1

If non-zero, when a directory server we contact supports it, we will build a one-hop circuit and make an encrypted connection via its ORPort. (Default: 0)

PreferTunneledDirConns 0|1

If non-zero, we will avoid directory servers that don't support tunneled directory connections, when possible. (Default: 0)

CLIENT OPTIONS

The following options are useful only for clients (that is, if SocksPort is non-zero):

AllowInvalidNodes entry|exit|middle|introduction|rendezvous|...

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.

Bridge IP:ORPort [fingerprint]

When set along with UseBridges, instructs Tor to use the relay at "IP:ORPort" as a "bridge" relaying into the Tor network. If "fingerprint" is provided (using the same format as for DirServer), we will verify that the relay running at that location has the right fingerprint. We also use fingerprint to look up the bridge descriptor at the bridge authority, if it's provided and if UpdateBridgesFromAuthority is set too.

CircuitBuildTimeout NUM

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.)

CircuitIdleTimeout NUM

If we have kept 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.)

ClientOnly 0|1

If set to 1, Tor will under no circumstances run as a server or serve directory requests. 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)

ExcludeNodes node,node,...

A list of identity fingerprints or nicknames of nodes to never use when building a circuit.

EntryNodes node,node,...

A list of identity fingerprints or nicknames 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.

ExitNodes node,node,...

A list of identity fingerprints or nicknames 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.

StrictEntryNodes 0|1

If 1, Tor will never use any nodes besides those listed in "EntryNodes" for the first hop of a circuit.

StrictExitNodes 0|1

If 1, Tor will never use any nodes besides those listed in "ExitNodes" for the last hop of a circuit.

FascistFirewall 0|1

If 1, Tor will only create outgoing connections to ORs running on ports that your firewall allows (defaults to 80 and 443; see FirewallPorts). 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. If you prefer more fine-grained control, use ReachableAddresses instead.

FirewallPorts PORTS

A list of ports that your firewall allows you to connect to. Only used when FascistFirewall is set. This option is deprecated; use ReachableAddresses instead. (Default: 80, 443)

ReachableAddresses ADDR[/MASK][:PORT]...

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 *:*'.)

ReachableDirAddresses ADDR[/MASK][:PORT]...

Like ReachableAddresses, 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 ReachableAddresses is used. If HttpProxy is set then these connections will go through that proxy.

ReachableORAddresses ADDR[/MASK][:PORT]...

Like ReachableAddresses, 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 ReachableAddresses is used. If HttpsProxy is set then these connections will go through that proxy.

The separation between ReachableORAddresses and ReachableDirAddresses is only interesting when you are connecting through proxies (see HttpProxy and HttpsProxy). 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.

LongLivedPorts PORTS

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, 6697, 8300)

MapAddress address newaddress

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 torserver (where torserver is the nickname of the server), use "MapAddress www.indymedia.org www.indymedia.org.torserver.exit".

NewCircuitPeriod NUM

Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds)

MaxCircuitDirtiness NUM

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)

NodeFamily node,node,...

The Tor servers, defined by their identity fingerprints or nicknames, 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.

EnforceDistinctSubnets 0|1

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)

RendNodes node,node,...

A list of identity fingerprints or nicknames of preferred nodes to use for the rendezvous point, if possible.

RendExcludeNodes node,node,...

A list of identity fingerprints or nicknames of nodes to never use when choosing a rendezvous point.

SocksPort PORT

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)

SocksListenAddress IP[:PORT]

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.

SocksPolicy policy,policy,...

Set an entrance policy for this server, to limit who can connect to the SocksPort and DNSPort ports. The policies have the same form as exit policies below.

SocksTimeout NUM

Let a socks connection wait NUM seconds handshaking, and NUM seconds unattached waiting for an appropriate circuit, before we fail it. (Default: 2 minutes.)

TestVia node,node,...

A list of identity fingerprints or nicknames of nodes to prefer for your middle hop when building testing circuits. This option is mainly for debugging reachability problems.

TrackHostExits host,.domain,...

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.

TrackHostExitsExpire NUM

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).

UpdateBridgesFromAuthority 0|1

When set (along with UseBridges), Tor will try to fetch bridge descriptors from the configured bridge authorities when feasible. It will fall back to a direct request if the authority responds with a 404. (Default: 0)

UseBridges 0|1

When set, Tor will fetch descriptors for each bridge listed in the "Bridge" config lines, and use these relays as both entry guards and directory guards. (Default: 0)

UseEntryGuards 0|1

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.)

NumEntryGuards NUM

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.)

SafeSocks 0|1

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.)

TestSocks 0|1

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)

VirtualAddrNetwork Address/bits

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)

When providing proxy server service to a network of computers using a tool like dns-proxy-tor, change this address to "10.192.0.0/10" or "172.16.0.0/12". The default VirtualAddrNetwork address range on a properly configured machine will route to the loopback interface. For local use, no change to the default VirtualAddrNetwork setting is needed.

AllowNonRFC953Hostnames 0|1

When this option is disabled, Tor blocks hostnames containing illegal characters (like @ and :) rather than sending them to an exit node to be resolved. This helps trap accidental attempts to resolve URLs and so on. (Default: 0)

FastFirstHopPK 0|1

When this option is disabled, Tor uses the public key step for the first hop of creating circuits. Skipping it is generally safe since we have already used TLS to authenticate the relay and to establish forward-secure keys. Turning this option off makes circuit building slower.

Note that Tor will always use the public key step for the first hop if it's operating as a relay, and it will never use the public key step if it doesn't yet know the onion key of the first hop. (Default: 1)

TransPort PORT

If non-zero, enables transparent proxy support on PORT (by convention, 9040). Requires OS support for transparent proxies, such as BSDs' pf or Linux's IPTables. If you're planning to use Tor as a transparent proxy for a network, you'll want to examine and change VirtualAddrNetwork from the default setting. You'll also want to set the TransListenAddress option for the network you'd like to proxy. (Default: 0).

TransListenAddress IP[:PORT]

Bind to this address to listen for transparent proxy connections. (Default: 127.0.0.1). This is useful for exporting a transparent proxy server to an entire network.

NATDPort PORT

Allow old versions of ipfw (as included in old versions of FreeBSD, etc.) to send connections through Tor using the NATD protocol. This option is only for people who cannot use TransPort.

NATDListenAddress IP[:PORT]

Bind to this address to listen for NATD connections. (Default: 127.0.0.1).

AutomapHostsOnResolve 0|1

When this option is enabled, and we get a request to resolve an address that ends with one of the suffixes in AutomapHostsSuffixes, we map an unused virtual address to that address, and return the new virtual address. This is handy for making then connect to it. (Default: 0).

AutomapHostsSuffixes SUFFIX,SUFFIX,...

A comma-separated list of suffixes to use with AutomapHostsOnResolve. The "." suffix is equivalent to "all addresses." (Default: .exit,.onion).

DNSPort PORT

If non-zero, Tor listens for UDP DNS requests on this port and resolves them anonymously. (Default: 0).

DNSListenAddress IP[:PORT]

Bind to this address to listen for DNS connections. (Default: 127.0.0.1).

ClientDNSRejectInternalAddresses 0|1

If true, Tor does not believe any anonymously retrieved DNS answer that tells it that an address resolves to an internal address (like 127.0.0.1 or 192.168.0.1). This option prevents certain browser-based attacks; don't turn it off unless you know what you're doing. (Default: 1).

DownloadExtraInfo 0|1

If true, Tor downloads and caches "extra-info" documents. These documents contain information about servers other than the information in their regular router descriptors. Tor does not use this information for anything itself; to save bandwidth, leave this option turned off. (Default: 0).

FallbackNetworkstatusFile FILENAME

If Tor doesn't have a cached networkstatus file, it starts out using this one instead. Even if this file is out of date, Tor can still use it to learn about directory mirrors, so it doesn't need to put load on the authorities. (Default: None).

WarnPlaintextPorts port,port,...

Tells Tor to issue a warnings whenever the user tries to make an anonymous connection to one of these ports. This option is designed to alert users to services that risk sending passwords in the clear. (Default: 23,109,110,143).

RejectPlaintextPorts port,port,...

Like WarnPlaintextPorts, but instead of warning about risky port uses, Tor will instead refuse to make the connection. (Default: None).

SERVER OPTIONS

The following options are useful only for servers (that is, if ORPort is non-zero):

Address address

The IP address or fqdn of this server (e.g. moria.mit.edu). You can leave this unset, and Tor will guess your IP address.

AssumeReachable 0|1

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 AuthoritativeDirectory is also set, this option instructs the dirserver to bypass remote reachability testing too and list all connected servers as running.

BridgeRelay 0|1

Sets the relay to act as a "bridge" with respect to relaying connections from bridge users to the Tor network. Mainly it influences how the relay will cache and serve directory information. Usually used in combination with PublishServerDescriptor.

ContactInfo email_address

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.

ExitPolicy policy,policy,...

Set an exit policy for this server. Each policy is of the form "accept|reject ADDR[/MASK][:PORT]". If /MASK is omitted then this policy just applies to the host given. Instead of giving a host or network you can also use "*" to denote the universe (0.0.0.0/0). PORT can be a single port number, an interval of ports "FROM_PORT-TO_PORT", or "*". If PORT is omitted, that means "*".

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), along with your public IP address, 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:*", though that may also allow connections to your own computer that are addressed to its public (external) IP address. 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:

reject *:25

reject *:119

reject *:135-139

reject *:445

reject *:465

reject *:563

reject *:587

reject *:1214

reject *:4661-4666

reject *:6346-6429

reject *:6699

reject *:6881-6999

accept *:*

ExitPolicyRejectPrivate 0|1

Reject all private (local) networks, along with your own public IP address, at the beginning of your exit policy. See above entry on ExitPolicy. (Default: 1)

MaxOnionsPending NUM

If you have more than this number of onionskins queued for decrypt, reject new ones. (Default: 100)

MyFamily node,node,...

Declare that this Tor server is controlled or administered by a group or organization identical or similar to that of the other servers, defined by their identity fingerprints or nicknames. 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.)

Nickname name

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].

NumCPUs num

How many processes to use at once for decrypting onionskins. (Default: 1)

ORPort PORT

Advertise this port to listen for connections from Tor clients and servers.

ORListenAddress IP[:PORT]

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.

PublishServerDescriptor 0|1|v1|v2|v3|bridge|hidserv, ...

This option is only considered if you have an ORPort defined. You can choose multiple arguments, separated by commas.

If set to 0, Tor will act as a server but it will not publish its descriptor to the directory authorities. (This is useful if you're testing out your server, or if you're using a Tor controller that handles directory publishing for you.) Otherwise, Tor will publish its descriptor to all directory authorities of the type(s) specified. The value "1" is treated as a synonym for the default, which is currently "v2,v3".

RedirectExit pattern target

THIS OPTION IS DEPRECATED. It will go away in a future version of Tor. Whenever an outgoing connection tries to connect to one of a given set of addresses, connect to target (an address:port 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 RedirectExit 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.

ShutdownWaitLength NUM

When we get a SIGINT and we're a server, we begin shutting down: we close listeners and start refusing new circuits. After NUM seconds, we exit. If we get a second SIGINT, we exit immediately. (Default: 30 seconds)

AccountingMax N bytes|KB|MB|GB|TB

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".

AccountingStart day|week|month [day] HH:MM

Specify how long accounting periods last. If month is given, each accounting period runs from the time HH:MM on the dayth day of one month to the same day and time of the next. (The day must be between 1 and 28.) If week is given, each accounting period runs from the time HH:MM of the dayth 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 day is given, each accounting period runs from the time HH:MM 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".)

ServerDNSResolvConfFile filename

Overrides the default DNS configuration with the configuration in filename. The file format is the same as the standard Unix "resolv.conf" file (7). This option, like all other ServerDNS options, only affects name lookups that your server does on behalf of clients. Also, it only takes effect if Tor was built with eventdns support. (Defaults to use the system DNS configuration.)

ServerDNSSearchDomains 0|1

If set to 1, 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 lookups that your server does on behalf of clients, and only takes effect if Tor was built with eventdns support. (Defaults to "0".)

ServerDNSDetectHijacking 0|1

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 lookups that your server does on behalf of clients, and only takes effect if Tor was built with eventdns support. (Defaults to "1".)

ServerDNSTestAddresses address,address,...

When we're detecting DNS hijacking, make sure that these valid addresses aren't getting redirected. If they are, then our DNS is completely useless, and we'll reset our exit policy to "reject *:*". This option only affects name lookups that your server does on behalf of clients, and only takes effect if Tor was built with eventdns support. (Defaults to "www.google.com, www.mit.edu, www.yahoo.com, www.slashdot.org".)

ServerDNSAllowNonRFC953Hostnames 0|1

When this option is disabled, Tor does not try to resolve hostnames containing illegal characters (like @ and :) rather than sending them to an exit node to be resolved. This helps trap accidental attempts to resolve URLs and so on. This option only affects name lookups that your server does on behalf of clients, and only takes effect if Tor was built with eventdns support. (Default: 0)

BridgeRecordUsageByCountry 0|1

When this option is enabled and BridgeRelay is also enabled, and we have GeoIP data, Tor keeps a keep a per-country count of how many client addresses have contacted it so that it can help the bridge authority guess which countries have blocked access to it.

GeoIPFile filename

A filename containing GeoIP data, for use with BridgeRecordUsageByCountry.

DIRECTORY SERVER OPTIONS

The following options are useful only for directory servers (that is, if DirPort is non-zero):

AuthoritativeDirectory 0|1

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.

V1AuthoritativeDirectory 0|1

When this option is set in addition to AuthoritativeDirectory, Tor generates version 1 directory and running-routers documents (for legacy Tor clients up to 0.1.0.x).

V2AuthoritativeDirectory 0|1

When this option is set in addition to AuthoritativeDirectory, Tor generates version 2 network statuses and serves descriptors, etc as described in doc/spec/dir-spec-v2.txt (for Tor clients and servers running 0.1.1.x and 0.1.2.x).

V3AuthoritativeDirectory 0|1

When this option is set in addition to AuthoritativeDirectory, Tor generates version 3 network statuses and serves descriptors, etc as described in doc/spec/dir-spec.txt (for Tor clients and servers running at least 0.2.0.x).

VersioningAuthoritativeDirectory 0|1

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 RecommendedVersions, RecommendedClientVersions, and RecommendedServerVersions.

NamingAuthoritativeDirectory 0|1

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 approved-routers in the FILES section below.

HSAuthoritativeDir 0|1

When this option is set in addition to AuthoritativeDirectory, Tor also accepts and serves hidden service descriptors. (Default: 0)

HSAuthorityRecordStats 0|1

When this option is set in addition to HSAuthoritativeDir, Tor periodically (every 15 minutes) writes statistics about hidden service usage to a file hsusage in its data directory. (Default: 0)

HidServDirectoryV2 0|1

When this option is set, Tor accepts and serves v2 hidden service descriptors. (Default: 0)

BridgeAuthoritativeDir 0|1

When this option is set in addition to AuthoritativeDirectory, Tor accepts and serves router descriptors, but it caches and serves the main networkstatus documents rather than generating its own. (Default: 0)

MinUptimeHidServDirectoryV2 N seconds|minutes|hours|days|weeks

Minimum uptime of a v2 hidden service directory to be accepted as such by authoritative directories. (Default: 24 hours)

DirPort PORT

Advertise the directory service on this port.

DirListenAddress IP[:PORT]

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.

DirPolicy policy,policy,...

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.

DIRECTORY AUTHORITY SERVER OPTIONS

RecommendedVersions STRING 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 VersioningAuthoritativeDirectory should be set too.

RecommendedClientVersions STRING

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 RecommendedVersions is used. When this is set then VersioningAuthoritativeDirectory should be set too.

RecommendedServerVersions STRING

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 RecommendedVersions is used. When this is set then VersioningAuthoritativeDirectory should be set too.

DirAllowPrivateAddresses 0|1

If set to 1, Tor will accept router descriptors with arbitrary "Address" elements. Otherwise, if the address is not an IP address or is a private IP address, it will reject the router descriptor. Defaults to 0.

AuthDirBadDir AddressPattern...

Authoritative directories only. A set of address patterns for servers that will be listed as bad directories in any network status document this authority publishes, if AuthDirListBadDirs is set.

AuthDirBadExit AddressPattern...

Authoritative directories only. A set of address patterns for servers that will be listed as bad exits in any network status document this authority publishes, if AuthDirListBadExits is set.

AuthDirInvalid AddressPattern...

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.

AuthDirReject AddressPattern...

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.

AuthDirListBadDirs 0|1

Authoritative directories only. If set to 1, this directory has some opinion about which nodes are unsuitable as directory caches. (Do not set this to 1 unless you plan to list nonfunctioning directories as bad; otherwise, you are effectively voting in favor of every declared directory.)

AuthDirListBadExits 0|1

Authoritative directories only. If set to 1, this directory has some opinion about which nodes are unsuitable as exit nodes. (Do not set this to 1 unless you plan to list nonfunctioning exits as bad; otherwise, you are effectively voting in favor of every declared exit as an exit.)

AuthDirRejectUnlisted 0|1

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)

AuthDirMaxServersPerAddr NUM

Authoritative directories only. The maximum number of servers that we will list as acceptable on a single IP address. Set this to "0" for "no limit". (Default: 2)

AuthDirMaxServersPerAuthAddr NUM

Authoritative directories only. Like AuthDirMaxServersPerAddr, but applies to addresses shared with directory authorities. (Default: 5)

V3AuthVotingInterval N minutes|hours

V3 authoritative directories only. Configures the server's preferred voting interval. Note that voting will actually happen at an interval chosen by consensus from all the authorities' preferred intervals. This time SHOULD divide evenly into a day. (Default: 1 hour)

V3AuthVoteDelay NUM

V3 authoritative directories only. Configures the server's preferred delay between publishing its vote and assuming it has all the votes from all the other authorities. Note that the actual time used is not the server's preferred time, but the consensus of all preferences. (Default: 5 minutes.)

V3AuthDistDelay NUM

V3 authoritative directories only. Configures the server's preferred delay between publishing its consensus and signature and assuming it has all the signatures from all the other authorities. Note that the actual time used is not the server's preferred time, but the consensus of all preferences. (Default: 5 minutes.)

V3AuthNIntervalsValid NUM

V3 authoritative directories only. Configures the number of VotingIntervals for which each consensus should be valid for. Choosing high numbers increases network partitioning risks; choosing low numbers increases directory traffic. Note that the actual number of intervals used is not the server's preferred number, but the consensus of all preferences. Must be at least 2. (Default: 3.)

HIDDEN SERVICE OPTIONS

The following options are used to configure a hidden service.

HiddenServiceDir DIRECTORY

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.

HiddenServicePort VIRTPORT [TARGET]

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. You may also have multiple lines with the same VIRTPORT: when a user connects to that VIRTPORT, one of the TARGETs from those lines will be chosen at random.

HiddenServiceNodes node,node,...

If possible, use the specified nodes, defined by their identity fingerprints or nicknames, 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.

HiddenServiceExcludeNodes node,node,...

Do not use the specified nodes, defined by their identity fingerprints or nicknames, as introduction points for the hidden service. In normal use there is no reason to set this.

PublishHidServDescriptors 0|1

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)

HiddenServiceVersion version,version,...

A list of rendezvous service descriptor versions to publish for the hidden service. Possible version numbers are 0 and 2. (Default: 0, 2)

RendPostPeriod N seconds|minutes|hours|days|weeks

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)

SIGNALS

Tor catches the following signals:

SIGTERM

Tor will catch this, clean up and sync to disk if necessary, and exit.

SIGINT

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.)

SIGHUP

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.

SIGUSR1

Log statistics about current connections, past connections, and throughput.

SIGUSR2

Switch all logs to loglevel debug. You can go back to the old loglevels by sending a SIGHUP.

SIGCHLD

Tor receives this signal when one of its helper processes has exited, so it can clean up.

SIGPIPE

Tor catches this signal and ignores it.

SIGXFSZ

If this signal exists on your platform, Tor catches and ignores it.

FILES

/etc/tor/torrc

The configuration file, which contains "option value" pairs.

/var/lib/tor/

The tor process stores keys and other data here.

DataDirectory/cached-status/*

The most recently downloaded network status document for each authority. Each file holds one such document; the filenames are the hexadecimal identity key fingerprints of the directory authorities.

DataDirectory/cached-descriptors and cached-descriptors.new

These files hold downloaded router statuses. Some routers may appear more than once; if so, the most recently published descriptor is used. Lines beginning with @-signs are annotations that contain more information about a given router. The ".new" file is an append-only journal; when it gets too large, all entries are merged into a new cached-routers file.

DataDirectory/cached-routers and cached-routers.new

Obsolete versions of cached-descriptors and cached-descriptors.new. When Tor can't find the newer files, it looks here instead.

DataDirectory/state

A set of persistent key-value mappings. These are documented in the file. These include:

- The current entry guards and their status.

- The current bandwidth accounting values (unused so far; see below).

- When the file was last written

- What version of Tor generated the state file

- A short history of bandwidth usage, as produced in the router descriptors.

DataDirectory/bw_accounting

Used to track bandwidth accounting values (when the current period starts and ends; how much has been read and written so far this period). This file is obsolete, and the data is now stored in the 'state' file as well. Only used when bandwidth accounting is enabled.

DataDirectory/hsusage

Used to track hidden service usage in terms of fetch and publish requests to this hidden service authoritative directory. Only used when recording of statistics is enabled.

DataDirectory/control_auth_cookie

Used for cookie authentication with the controller. Location can be overridden by the CookieAuthFile config option. Regenerated on startup. See control-spec.txt for details. Only used when cookie authentication is enabled.

DataDirectory/keys/*

Only used by servers. Holds identity keys and onion keys.

DataDirectory/fingerprint

Only used by servers. Holds the fingerprint of the server's identity key.

DataDirectory/approved-routers

Only for naming authoritative directory servers (see NamingAuthoritativeDirectory). This file lists nickname to identity bindings. Each line lists a nickname and a fingerprint separated by whitespace. See your fingerprint file in the DataDirectory for an example line. If the nickname is !reject then descriptors from the given identity (fingerprint) are rejected by this server. If it is !invalid then descriptors are accepted but marked in the directory as not valid, that is, not recommended.

DataDirectory/router-stability

Only used by authoritative directory servers. Tracks measurements for router mean-time-between-failures so that authorities have a good idea of how to set their Stable flags.

HiddenServiceDirectory/hostname

The <base32-encoded-fingerprint>.onion domain name for this hidden service.

HiddenServiceDirectory/private_key

The private key for this hidden service.

SEE ALSO

privoxy(1), tsocks(1), torify(1)

https://www.torproject.org/

BUGS

Plenty, probably. Tor is still in development. Please report them.

AUTHORS

Roger Dingledine <arma@mit.edu>, Nick Mathewson <nickm@alum.mit.edu>.