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First (and fragmentary) draft of revised controller protocol.

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$Id$
TC: A Tor control protocol (Version 0)
-1. Deprecation
THIS PROTOCOL IS DEPRECATED. It is still documented here because it is the
only Tor control protocol supported in the Tor implementation right now.
0. Scope
This document describes an implementation-specific protocol that is used
for other programs (such as frontend user-interfaces) to communicate
with a locally running Tor process. It is not part of the Tor onion
routing protocol.
We're trying to be pretty extensible here, but not infinitely
forward-compatible.
1. Protocol outline
TC is a bidirectional message-based protocol. It assumes an underlying
stream for communication between a controlling process (the "client") and
a Tor process (the "server"). The stream may be implemented via TCP,
TLS-over-TCP, a Unix-domain socket, or so on, but it must provide
reliable in-order delivery. For security, the stream should not be
accessible by untrusted parties.
In TC, the client and server send typed variable-length messages to each
other over the underlying stream. By default, all messages from the server
are in response to messages from the client. Some client requests, however,
will cause the server to send messages to the client indefinitely far into
the future.
Servers respond to messages in the order they're received.
2. Message format
The messages take the following format:
Length [2 octets; big-endian]
Type [2 octets; big-endian]
Body [Length octets]
Upon encountering a recognized Type, implementations behave as described in
section 3 below. If the type is not recognized, servers respond with an
"ERROR" message (code UNRECOGNIZED; see 3.1 below), and clients simply ignore
the message.
2.1. Types and encodings
All numbers are given in big-endian (network) order.
OR identities are given in hexadecimal, in the same format as identity key
fingerprints, but without spaces; see tor-spec.txt for more information.
3. Message types
Message types are drawn from the following ranges:
0x0000-0xEFFF : Reserved for use by official versions of this spec.
0xF000-0xFFFF : Unallocated; usable by unofficial extensions.
3.1. ERROR (Type 0x0000)
Sent in response to a message that could not be processed as requested.
The body of the message begins with a 2-byte error code. The following
values are defined:
0x0000 Unspecified error
[]
0x0001 Internal error
[Something went wrong inside Tor, so that the client's
request couldn't be fulfilled.]
0x0002 Unrecognized message type
[The client sent a message type we don't understand.]
0x0003 Syntax error
[The client sent a message body in a format we can't parse.]
0x0004 Unrecognized configuration key
[The client tried to get or set a configuration option we don't
recognize.]
0x0005 Invalid configuration value
[The client tried to set a configuration option to an
incorrect, ill-formed, or impossible value.]
0x0006 Unrecognized byte code
[The client tried to set a byte code (in the body) that
we don't recognize.]
0x0007 Unauthorized.
[The client tried to send a command that requires
authorization, but it hasn't sent a valid AUTHENTICATE
message.]
0x0008 Failed authentication attempt
[The client sent a well-formed authorization message.]
0x0009 Resource exhausted
[The server didn't have enough of a given resource to
fulfill a given request.]
0x000A No such stream
0x000B No such circuit
0x000C No such OR
The rest of the body should be a human-readable description of the error.
In general, new error codes should only be added when they don't fall under
one of the existing error codes.
3.2. DONE (Type 0x0001)
Sent from server to client in response to a request that was successfully
completed, with no more information needed. The body is usually empty but
may contain a message.
3.3. SETCONF (Type 0x0002)
Change the value of a configuration variable. The body contains a list of
newline-terminated key-value configuration lines. An individual key-value
configuration line consists of the key, followed by a space, followed by
the value. The server behaves as though it had just read the key-value pair
in its configuration file.
The server responds with a DONE message on success, or an ERROR message on
failure.
When a configuration options takes multiple values, or when multiple
configuration keys form a context-sensitive group (see below), then
setting _any_ of the options in a SETCONF command is taken to reset all of
the others. For example, if two ORBindAddress values are configured,
and a SETCONF command arrives containing a single ORBindAddress value, the
new command's value replaces the two old values.
To _remove_ all settings for a given option entirely (and go back to its
default value), send a single line containing the key and no value.
3.4. GETCONF (Type 0x0003)
Request the value of a configuration variable. The body contains one or
more NL-terminated strings for configuration keys. The server replies
with a CONFVALUE message.
If an option appears multiple times in the configuration, all of its
key-value pairs are returned in order.
Some options are context-sensitive, and depend on other options with
different keywords. These cannot be fetched directly. Currently there
is only one such option: clients should use the "HiddenServiceOptions"
virtual keyword to get all HiddenServiceDir, HiddenServicePort,
HiddenServiceNodes, and HiddenServiceExcludeNodes option settings.
3.5. CONFVALUE (Type 0x0004)
Sent in response to a GETCONF message; contains a list of "Key Value\n"
(A non-whitespace keyword, a single space, a non-NL value, a NL)
strings.
3.6. SETEVENTS (Type 0x0005)
Request the server to inform the client about interesting events.
The body contains a list of 2-byte event codes (see "event" below).
Any events *not* listed in the SETEVENTS body are turned off; thus, sending
SETEVENTS with an empty body turns off all event reporting.
The server responds with a DONE message on success, and an ERROR message
if one of the event codes isn't recognized. (On error, the list of active
event codes isn't changed.)
3.7. EVENT (Type 0x0006)
Sent from the server to the client when an event has occurred and the
client has requested that kind of event. The body contains a 2-byte
event code followed by additional event-dependent information. Event
codes are:
0x0001 -- Circuit status changed
Status [1 octet]
0x00 Launched - circuit ID assigned to new circuit
0x01 Built - all hops finished, can now accept streams
0x02 Extended - one more hop has been completed
0x03 Failed - circuit closed (was not built)
0x04 Closed - circuit closed (was built)
Circuit ID [4 octets]
(Must be unique to Tor process/time)
Path [NUL-terminated comma-separated string]
(For extended/failed, is the portion of the path that is
built)
0x0002 -- Stream status changed
Status [1 octet]
(Sent connect=0,sent resolve=1,succeeded=2,failed=3,
closed=4, new connection=5, new resolve request=6,
stream detached from circuit and still retriable=7)
Stream ID [4 octets]
(Must be unique to Tor process/time)
Target (NUL-terminated address-port string]
0x0003 -- OR Connection status changed
Status [1 octet]
(Launched=0,connected=1,failed=2,closed=3)
OR nickname/identity [NUL-terminated]
0x0004 -- Bandwidth used in the last second
Bytes read [4 octets]
Bytes written [4 octets]
0x0005 -- Notice/warning/error occurred
Message [NUL-terminated]
<obsolete: use 0x0007-0x000B instead.>
0x0006 -- New descriptors available
OR List [NUL-terminated, comma-delimited list of
OR identity]
0x0007 -- Debug message occurred
0x0008 -- Info message occurred
0x0009 -- Notice message occurred
0x000A -- Warning message occurred
0x000B -- Error message occurred
Message [NUL-terminated]
3.8. AUTHENTICATE (Type 0x0007)
Sent from the client to the server. Contains a 'magic cookie' to prove
that client is really allowed to control this Tor process. The server
responds with DONE or ERROR.
The format of the 'cookie' is implementation-dependent; see 4.1 below for
information on how the standard Tor implementation handles it.
3.9. SAVECONF (Type 0x0008)
Sent from the client to the server. Instructs the server to write out
its config options into its torrc. Server returns DONE if successful, or
ERROR if it can't write the file or some other error occurs.
3.10. SIGNAL (Type 0x0009)
Sent from the client to the server. The body contains one byte that
indicates the action the client wishes the server to take.
1 (0x01) -- Reload: reload config items, refetch directory.
2 (0x02) -- Controlled shutdown: if server is an OP, exit immediately.
If it's an OR, close listeners and exit after 30 seconds.
10 (0x0A) -- Dump stats: log information about open connections and
circuits.
12 (0x0C) -- Debug: switch all open logs to loglevel debug.
15 (0x0F) -- Immediate shutdown: clean up and exit now.
The server responds with DONE if the signal is recognized (or simply
closes the socket if it was asked to close immediately), else ERROR.
3.11. MAPADDRESS (Type 0x000A)
Sent from the client to the server. The body contains a sequence of
address mappings, each consisting of the address to be mapped, a single
space, the replacement address, and a NL character.
Addresses may be IPv4 addresses, IPv6 addresses, or hostnames.
The client sends this message to the server in order to tell it that future
SOCKS requests for connections to the original address should be replaced
with connections to the specified replacement address. If the addresses
are well-formed, and the server is able to fulfill the request, the server
replies with a single DONE message containing the source and destination
addresses. If request is malformed, the server replies with a syntax error
message. The server can't fulfill the request, it replies with an internal
ERROR message.
The client may decline to provide a body for the original address, and
instead send a special null address ("0.0.0.0" for IPv4, "::0" for IPv6, or
"." for hostname), signifying that the server should choose the original
address itself, and return that address in the DONE message. The server
should ensure that it returns an element of address space that is unlikely
to be in actual use. If there is already an address mapped to the
destination address, the server may reuse that mapping.
If the original address is already mapped to a different address, the old
mapping is removed. If the original address and the destination address
are the same, the server removes any mapping in place for the original
address.
{Note: This feature is designed to be used to help Tor-ify applications
that need to use SOCKS4 or hostname-less SOCKS5. There are three
approaches to doing this:
1. Somehow make them use SOCKS4a or SOCKS5-with-hostnames instead.
2. Use tor-resolve (or another interface to Tor's resolve-over-SOCKS
feature) to resolve the hostname remotely. This doesn't work
with special addresses like x.onion or x.y.exit.
3. Use MAPADDRESS to map an IP address to the desired hostname, and then
arrange to fool the application into thinking that the hostname
has resolved to that IP.
This functionality is designed to help implement the 3rd approach.}
[XXXX When, if ever, can mappings expire? Should they expire?]
[XXXX What addresses, if any, are safe to use?]
3.12 GETINFO (Type 0x000B)
Sent from the client to the server. The message body is as for GETCONF:
one or more NL-terminated strings. The server replies with an INFOVALUE
message.
Unlike GETCONF, this message is used for data that are not stored in the
Tor configuration file, but instead.
Recognized key and their values include:
"version" -- The version of the server's software, including the name
of the software. (example: "Tor 0.0.9.4")
"desc/id/<OR identity>" or "desc/name/<OR nickname>" -- the latest server
descriptor for a given OR, NUL-terminated. If no such OR is known, the
corresponding value is an empty string.
"network-status" -- a space-separated list of all known OR identities.
This is in the same format as the router-status line in directories;
see tor-spec.txt for details.
"addr-mappings/all"
"addr-mappings/config"
"addr-mappings/cache"
"addr-mappings/control" -- a NL-terminated list of address mappings, each
in the form of "from-address" SP "to-address". The 'config' key
returns those address mappings set in the configuration; the 'cache'
key returns the mappings in the client-side DNS cache; the 'control'
key returns the mappings set via the control interface; the 'all'
target returns the mappings set through any mechanism.
3.13 INFOVALUE (Type 0x000C)
Sent from the server to the client in response to a GETINFO message.
Contains one or more items of the format:
Key [(NUL-terminated string)]
Value [(NUL-terminated string)]
The keys match those given in the GETINFO message.
3.14 EXTENDCIRCUIT (Type 0x000D)
Sent from the client to the server. The message body contains two fields:
Circuit ID [4 octets]
Path [NUL-terminated, comma-delimited string of OR nickname/identity]
This request takes one of two forms: either the Circuit ID is zero, in
which case it is a request for the server to build a new circuit according
to the specified path, or the Circuit ID is nonzero, in which case it is a
request for the server to extend an existing circuit with that ID according
to the specified path.
If the request is successful, the server sends a DONE message containing
a message body consisting of the four-octet Circuit ID of the newly created
circuit.
3.15 ATTACHSTREAM (Type 0x000E)
Sent from the client to the server. The message body contains two fields:
Stream ID [4 octets]
Circuit ID [4 octets]
This message informs the server that the specified stream should be
associated with the specified circuit. Each stream may be associated with
at most one circuit, and multiple streams may share the same circuit.
Streams can only be attached to completed circuits (that is, circuits that
have sent a circuit status 'built' event).
If the circuit ID is 0, responsibility for attaching the given stream is
returned to Tor.
{Implementation note: By default, Tor automatically attaches streams to
circuits itself, unless the configuration variable
"__LeaveStreamsUnattached" is set to "1". Attempting to attach streams
via TC when "__LeaveStreamsUnattached" is false may cause a race between
Tor and the controller, as both attempt to attach streams to circuits.}
3.16 POSTDESCRIPTOR (Type 0x000F)
Sent from the client to the server. The message body contains one field:
Descriptor [NUL-terminated string]
This message informs the server about a new descriptor.
The descriptor, when parsed, must contain a number of well-specified
fields, including fields for its nickname and identity.
If there is an error in parsing the descriptor, the server must send an
appropriate error message. If the descriptor is well-formed but the server
chooses not to add it, it must reply with a DONE message whose body
explains why the server was not added.
3.17 FRAGMENTHEADER (Type 0x0010)
Sent in either direction. Used to encapsulate messages longer than 65535
bytes in length.
Underlying type [2 bytes]
Total Length [4 bytes]
Data [Rest of message]
A FRAGMENTHEADER message MUST be followed immediately by a number of
FRAGMENT messages, such that lengths of the "Data" fields of the
FRAGMENTHEADER and FRAGMENT messages add to the "Total Length" field of the
FRAGMENTHEADER message.
Implementations MUST NOT fragment messages of length less than 65536 bytes.
Implementations MUST be able to process fragmented messages that not
optimally packed.
3.18 FRAGMENT (Type 0x0011)
Data [Entire message]
See FRAGMENTHEADER for more information
3.19 REDIRECTSTREAM (Type 0x0012)
Sent from the client to the server. The message body contains two fields:
Stream ID [4 octets]
Address [variable-length, NUL-terminated.]
Tells the server to change the exit address on the specified stream. No
remapping is performed on the new provided address.
To be sure that the modified address will be used, this event must be sent
after a new stream event is received, and before attaching this stream to
a circuit.
3.20 CLOSESTREAM (Type 0x0013)
Sent from the client to the server. The message body contains three
fields:
Stream ID [4 octets]
Reason [1 octet]
Flags [1 octet]
Tells the server to close the specified stream. The reason should be
one of the Tor RELAY_END reasons given in tor-spec.txt. Flags is not
used currently. Tor may hold the stream open for a while to flush
any data that is pending.
3.21 CLOSECIRCUIT (Type 0x0014)
Sent from the client to the server. The message body contains two
fields:
Circuit ID [4 octets]
Flags [1 octet]
Tells the server to close the specified circuit. If the LSB of the flags
field is nonzero, do not close the circuit unless it is unused.
4. Implementation notes
4.1. Authentication
By default, the current Tor implementation trusts all local users.
If the 'CookieAuthentication' option is true, Tor writes a "magic cookie"
file named "control_auth_cookie" into its data directory. To authenticate,
the controller must send the contents of this file.
If the 'HashedControlPassword' option is set, it must contain the salted
hash of a secret password. The salted hash is computed according to the
S2K algorithm in RFC 2440 (OpenPGP), and prefixed with the s2k specifier.
This is then encoded in hexadecimal, prefixed by the indicator sequence
"16:". Thus, for example, the password 'foo' could encode to:
16:660537E3E1CD49996044A3BF558097A981F539FEA2F9DA662B4626C1C2
++++++++++++++++**^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
salt hashed value
indicator
You can generate the salt of a password by calling
'tor --hash-password <password>'
or by using the example code in the Python and Java controller libraries.
To authenticate under this scheme, the controller sends Tor the original
secret that was used to generate the password.
4.2. Don't let the buffer get too big.
If you ask for lots of events, and 16MB of them queue up on the buffer,
the Tor process will close the socket.

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doc/control-spec.txt
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@ -1,148 +1,146 @@
$Id$
TC: A Tor control protocol
TC: A Tor control protocol (Version 1)
0. Scope
0 Scope
This document describes an implementation-specific protocol that is used
for other programs (such as frontend user-interfaces) to communicate
with a locally running Tor process. It is not part of the Tor onion
routing protocol.
This document describes an implementation-specific protocol that is used
for other programs (such as frontend user-interfaces) to communicate with a
locally running Tor process. It is not part of the Tor onion routing
protocol.
We're trying to be pretty extensible here, but not infinitely
forward-compatible.
This protocol replaces version 0 of TC, which is now deprecated. For
reference, TC is described in "control-spec-v0.txt". Implementors are
recommended to avoid using TC directly, but instead to use a library that
can easily be updated to use the newer protocol.
1. Protocol outline
1 Protocol outline
TC is a bidirectional message-based protocol. It assumes an underlying
stream for communication between a controlling process (the "client") and
a Tor process (the "server"). The stream may be implemented via TCP,
TLS-over-TCP, a Unix-domain socket, or so on, but it must provide
reliable in-order delivery. For security, the stream should not be
accessible by untrusted parties.
TC is a bidirectional message-based protocol. It assumes an underlying
stream for communication between a controlling process (the "client" or
"controller") and a Tor process (the "server" or "tor process"). The
stream may be implemented via TCP, TLS-over-TCP, a Unix-domain socket, or
so on, but it must provide reliable in-order delivery. For security, the
stream should not be accessible by untrusted parties.
In TC, the client and server send typed variable-length messages to each
other over the underlying stream. By default, all messages from the server
are in response to messages from the client. Some client requests, however,
will cause the server to send messages to the client indefinitely far into
the future.
In TC, the client and server send typed messages to each other over the
underlying stream. The client sends "commands" and the server sends
"replies".
Servers respond to messages in the order they're received.
By default, all messages from the server are in response to messages from
the client. Some client requests, however, will cause the server to send
messages to the client indefinitely far into the future. Such
"asynchronous" replies are marked to such.
2. Message format
Servers respond to messages in the order messages are received.
The messages take the following format:
2 Message format
Length [2 octets; big-endian]
Type [2 octets; big-endian]
Body [Length octets]
2.1 Description format.
Upon encountering a recognized Type, implementations behave as described in
section 3 below. If the type is not recognized, servers respond with an
"ERROR" message (code UNRECOGNIZED; see 3.1 below), and clients simply ignore
the message.
The message formates listed below use ABNF as described in RFC2234.
The protocol itself is loosely based on SMTP (see RFC 2821).
2.1. Types and encodings
We use the following nonterminals from RFC2822: atom, qcontent
All numbers are given in big-endian (network) order.
We define the following general-use nonterminals:
OR identities are given in hexadecimal, in the same format as identity key
fingerprints, but without spaces; see tor-spec.txt for more information.
String = DQUOTE *qcontent DQUOTE
3. Message types
There are explicitly no limits on line length. All 8-bit characters are
permitted unless explicitly disallowed.
Message types are drawn from the following ranges:
2.2 Commands from controller to Tor.
0x0000-0xEFFF : Reserved for use by official versions of this spec.
0xF000-0xFFFF : Unallocated; usable by unofficial extensions.
Command = Keyword Arguments CRLF / "+" Keyword Arguments CRLF Data
Keyword = 1*ALPHA
Arguments = *(SP / VCHAR)
3.1. ERROR (Type 0x0000)
Specific commands and their arguments are described below in section 3.
Sent in response to a message that could not be processed as requested.
2.3 Replies from Tor to the controller
The body of the message begins with a 2-byte error code. The following
values are defined:
Reply = *(MidReplyLine / DataReplyLine) EndReplyLine
0x0000 Unspecified error
[]
MidReplyLine = "-" ReplyLine
DataReplyLine = "+" ReplyLine Data
EndReplyLine = SP ReplyLine
ReplyLine = StatusCode [ SP ReplyText ] CRLF
ReplyText = XXXX
StatusCode = XXXX
0x0001 Internal error
[Something went wrong inside Tor, so that the client's
request couldn't be fulfilled.]
Specific replies are mentioned below in section 3, and described more fully
in section 4.
0x0002 Unrecognized message type
[The client sent a message type we don't understand.]
2.4 General-use tokens
0x0003 Syntax error
[The client sent a message body in a format we can't parse.]
; Identifiers for servers.
ServerID = Nickname / Fingerprint
Nickname = 1*NicknameChar
NicknameChar = "a"-"z" / "A"-"Z" / "0" - "9"
Fingerprint = "$" 40*HEXDIG
0x0004 Unrecognized configuration key
[The client tried to get or set a configuration option we don't
recognize.]
; Unique identifiers for streams or circuits. Currently, Tor only
; uses digits, but this may change
StreamID = 1*16 IDChar
CircuitID = 1*16 IDChar
IDChar = ALPHA / DIGIT
0x0005 Invalid configuration value
[The client tried to set a configuration option to an
incorrect, ill-formed, or impossible value.]
Address = ip4-address / ip6-address / hostname (XXXX Define these)
0x0006 Unrecognized byte code
[The client tried to set a byte code (in the body) that
we don't recognize.]
0x0007 Unauthorized.
[The client tried to send a command that requires
authorization, but it hasn't sent a valid AUTHENTICATE
message.]
; A "Data" section is a sequence of octets concluded by the terminating
; sequence CRLF "." CRLF. The terminating sequence may not appear in the
; body of the data. Leading periods on lines in the data are escaped with
; an additional leading period as in RFC2821 section 4.5.2
Data = *DataLine "." CRLF
DataLine = CRLF / "." 1*LineItem CRLF/ NonDotItem *LineItem CRLF
LineItem = NonCR / 1*CR NonCRLF
NonDotItem = NonDotCR / 1*CR NonCRLF
0x0008 Failed authentication attempt
[The client sent a well-formed authorization message.]
3 Commands
0x0009 Resource exhausted
[The server didn't have enough of a given resource to
fulfill a given request.]
All commands and other keywords are case-insensitive.
0x000A No such stream
3.1 SETCONF
0x000B No such circuit
Change the value of one or more configuration variables. The syntax is:
0x000C No such OR
"SETCONF" 1*(SP keyword ["=" String]) CRLF
The rest of the body should be a human-readable description of the error.
Tor behaves as though it had just read each of the key-value pairs
from its configuration file. Keywords with no corresponding values have
their configuration values reset to their defaults. SETCONF is
all-or-nothing: if there is an error in any of the configuration settings,
Tor sets none of them.
In general, new error codes should only be added when they don't fall under
one of the existing error codes.
3.2. DONE (Type 0x0001)
Sent from server to client in response to a request that was successfully
completed, with no more information needed. The body is usually empty but
may contain a message.
3.3. SETCONF (Type 0x0002)
Change the value of a configuration variable. The body contains a list of
newline-terminated key-value configuration lines. An individual key-value
configuration line consists of the key, followed by a space, followed by
the value. The server behaves as though it had just read the key-value pair
in its configuration file.
The server responds with a DONE message on success, or an ERROR message on
failure.
Tor responds with a "250 configuration values set" reply on success.
Tor responds with a "513 syntax error in configuration values" reply on
syntax error, or a "553 impossible configuration setting" reply on a
semantic error.
When a configuration options takes multiple values, or when multiple
configuration keys form a context-sensitive group (see below), then
configuration keys form a context-sensitive group (see GETCONF below), then
setting _any_ of the options in a SETCONF command is taken to reset all of
the others. For example, if two ORBindAddress values are configured,
and a SETCONF command arrives containing a single ORBindAddress value, the
new command's value replaces the two old values.
the others. For example, if two ORBindAddress values are configured, and a
SETCONF command arrives containing a single ORBindAddress value, the new
command's value replaces the two old values.
To _remove_ all settings for a given option entirely (and go back to its
default value), send a single line containing the key and no value.
3.4. GETCONF (Type 0x0003)
3.2 GETCONF
Request the value of a configuration variable. The body contains one or
more NL-terminated strings for configuration keys. The server replies
with a CONFVALUE message.
Request the value of a configuration variable. The syntax is:
"GETCONF" 1*(SP keyword) CRLF
If all of the listed keywords exist in the Tor configuration, Tor replies
with a series of reply lines of the form:
250 keyword=value
If some of the listed keywords can't be found, Tor replies with a
"552 unknown configuration keyword" message.
If an option appears multiple times in the configuration, all of its
key-value pairs are returned in order.
@ -153,136 +151,93 @@ the message.
virtual keyword to get all HiddenServiceDir, HiddenServicePort,
HiddenServiceNodes, and HiddenServiceExcludeNodes option settings.
3.5. CONFVALUE (Type 0x0004)
3.3 SETEVENTS
Sent in response to a GETCONF message; contains a list of "Key Value\n"
(A non-whitespace keyword, a single space, a non-NL value, a NL)
strings.
Request the server to inform the client about interesting events. The
syntax is:
3.6. SETEVENTS (Type 0x0005)
"SETEVENTS" *(SP EventCode) CRLF
Request the server to inform the client about interesting events.
The body contains a list of 2-byte event codes (see "event" below).
Any events *not* listed in the SETEVENTS body are turned off; thus, sending
EventCode = "CIRC" / "STREAM" / "ORCONN" / "BW" / "DEBUG" /
"INFO" / "NOTICE" / "WARN" / "ERR" / "NEWDESC"
Any events *not* listed in the SETEVENTS line are turned off; thus, sending
SETEVENTS with an empty body turns off all event reporting.
The server responds with a DONE message on success, and an ERROR message
if one of the event codes isn't recognized. (On error, the list of active
event codes isn't changed.)
The server responds with a "250 OK" reply on success, and a "552
Unrecognized event" reply if one of the event codes isn't recognized. (On
error, the list of active event codes isn't changed.)
3.7. EVENT (Type 0x0006)
3.4 AUTHENTICATE
Sent from the server to the client when an event has occurred and the
client has requested that kind of event. The body contains a 2-byte
event code followed by additional event-dependent information. Event
codes are:
0x0001 -- Circuit status changed
Sent from the client to the server. The syntax is:
"AUTHENTICATE" SP 1*HEXDIG / QuotedString CRLF
Status [1 octet]
0x00 Launched - circuit ID assigned to new circuit
0x01 Built - all hops finished, can now accept streams
0x02 Extended - one more hop has been completed
0x03 Failed - circuit closed (was not built)
0x04 Closed - circuit closed (was built)
Circuit ID [4 octets]
(Must be unique to Tor process/time)
Path [NUL-terminated comma-separated string]
(For extended/failed, is the portion of the path that is
built)
The server responds with "250 OK" on success or "515 Bad authentication" if
the authentication cookie is incorrect.
0x0002 -- Stream status changed
Status [1 octet]
(Sent connect=0,sent resolve=1,succeeded=2,failed=3,
closed=4, new connection=5, new resolve request=6,
stream detached from circuit and still retriable=7)
Stream ID [4 octets]
(Must be unique to Tor process/time)
Target (NUL-terminated address-port string]
0x0003 -- OR Connection status changed
Status [1 octet]
(Launched=0,connected=1,failed=2,closed=3)
OR nickname/identity [NUL-terminated]
0x0004 -- Bandwidth used in the last second
Bytes read [4 octets]
Bytes written [4 octets]
0x0005 -- Notice/warning/error occurred
Message [NUL-terminated]
<obsolete: use 0x0007-0x000B instead.>
0x0006 -- New descriptors available
OR List [NUL-terminated, comma-delimited list of
OR identity]
0x0007 -- Debug message occurred
0x0008 -- Info message occurred
0x0009 -- Notice message occurred
0x000A -- Warning message occurred
0x000B -- Error message occurred
Message [NUL-terminated]
3.8. AUTHENTICATE (Type 0x0007)
Sent from the client to the server. Contains a 'magic cookie' to prove
that client is really allowed to control this Tor process. The server
responds with DONE or ERROR.
The format of the 'cookie' is implementation-dependent; see 4.1 below for
The format of the 'cookie' is implementation-dependent; see 5.1 below for
information on how the standard Tor implementation handles it.
3.9. SAVECONF (Type 0x0008)
If Tor requires authentication and the controller has not yet sent an
AUTHENTICATE message, Tor sends a "514 authentication required" reply to
any other kind of message.
Sent from the client to the server. Instructs the server to write out
its config options into its torrc. Server returns DONE if successful, or
ERROR if it can't write the file or some other error occurs.
3.5 SAVECONF
3.10. SIGNAL (Type 0x0009)
Sent from the client to the server. The syntax is:
"SAVECONF" CRLF
Sent from the client to the server. The body contains one byte that
indicates the action the client wishes the server to take.
Instructs the server to write out its config options into its torrc. Server
returns "250 OK" if successful, or " if it can't write the file or some
other error occurs.
1 (0x01) -- Reload: reload config items, refetch directory.
2 (0x02) -- Controlled shutdown: if server is an OP, exit immediately.
3.6 SIGNAL
Sent from the client to the server. The syntax is:
"SIGNAL" SP Signal CRLF
Signal = "RELOAD" / "SHUTDOWN" / "DUMP" / "DEBUG" / "TERM"
The meaning of the signals are:
RELOAD -- Reload: reload config items, refetch directory. (as for HUP)
SHUTDOWN -- Controlled shutdown: if server is an OP, exit immediately.
If it's an OR, close listeners and exit after 30 seconds.
10 (0x0A) -- Dump stats: log information about open connections and
circuits.
12 (0x0C) -- Debug: switch all open logs to loglevel debug.
15 (0x0F) -- Immediate shutdown: clean up and exit now.
(as for INT)
DUMP -- Dump stats: log information about open connections and
circuits. (as for USR1)
DEBUG -- Debug: switch all open logs to loglevel debug. (as for USR2)
TERM -- Immediate shutdown: clean up and exit now. (as for TERM)
The server responds with DONE if the signal is recognized (or simply
closes the socket if it was asked to close immediately), else ERROR.
The server responds with "250 OK" if the signal is recognized (or simply
closes the socket if it was asked to close immediately), or "552
Unrecognized signal" if the signal is unrecognized.
3.11. MAPADDRESS (Type 0x000A)
3.7 MAPADDRESS
Sent from the client to the server. The body contains a sequence of
address mappings, each consisting of the address to be mapped, a single
space, the replacement address, and a NL character.
Sent from the client to the server. The syntax is:
Addresses may be IPv4 addresses, IPv6 addresses, or hostnames.
"MAPADDRESS" 1*(Address "=" Address SP) CRLF
The client sends this message to the server in order to tell it that future
SOCKS requests for connections to the original address should be replaced
with connections to the specified replacement address. If the addresses
are well-formed, and the server is able to fulfill the request, the server
replies with a single DONE message containing the source and destination
addresses. If request is malformed, the server replies with a syntax error
message. The server can't fulfill the request, it replies with an internal
ERROR message.
The first address in each pair is an "original" address; the second is a
"replacement" address. The client sends this message to the server in
order to tell it that future SOCKS requests for connections to the original
address should be replaced with connections to the specified replacement
address. If the addresses are well-formed, and the server is able to
fulfill the request, the server replies with a 250 message:
250-OldAddress1=NewAddress1
250 OldAddress2=NewAddress2
containing the source and destination addresses. If request is malformed,
the server replies with "512 syntax error in command argument". If the server
can't fulfill the request, it replies with "451 resource exhausted."
The client may decline to provide a body for the original address, and
instead send a special null address ("0.0.0.0" for IPv4, "::0" for IPv6, or
"." for hostname), signifying that the server should choose the original
address itself, and return that address in the DONE message. The server
address itself, and return that address in the reply. The server
should ensure that it returns an element of address space that is unlikely
to be in actual use. If there is already an address mapped to the
destination address, the server may reuse that mapping.
@ -292,6 +247,11 @@ the message.
are the same, the server removes any mapping in place for the original
address.
Example:
C: MAPADDRESS 0.0.0.0=tor.eff.org 1.2.3.4=tor.freehaven.net
S: 250-127.192.10.10=tor.eff.org
S: 250 1.2.3.4=tor.freehaven.net
{Note: This feature is designed to be used to help Tor-ify applications
that need to use SOCKS4 or hostname-less SOCKS5. There are three
approaches to doing this:
@ -305,17 +265,23 @@ the message.
This functionality is designed to help implement the 3rd approach.}
[XXXX When, if ever, can mappings expire? Should they expire?]
[XXXX What addresses, if any, are safe to use?]
3.12 GETINFO (Type 0x000B)
3.8 GETINFO
Sent from the client to the server. The message body is as for GETCONF:
Sent from the client to the server. The syntax is as for GETCONF:
"GETINFO" 1*(SP keyword) CRLF
one or more NL-terminated strings. The server replies with an INFOVALUE
message.
Unlike GETCONF, this message is used for data that are not stored in the
Tor configuration file, but instead.
Unlike GETCONF, this message is used for data that are not stored in the Tor
configuration file, and that may be longer than a single line. On success,
one ReplyLine is sent for each requested value, followed by a final 250 OK
ReplyLine. If a value fits on a single line, the format is:
250-keyword=value
If avalue must be split over multiple lines, the format is:
250+keyword=
value
.
Recognized key and their values include:
"version" -- The version of the server's software, including the name
@ -332,28 +298,38 @@ the message.
"addr-mappings/all"
"addr-mappings/config"
"addr-mappings/cache"
"addr-mappings/control" -- a NL-terminated list of address mappings, each
in the form of "from-address" SP "to-address". The 'config' key
"addr-mappings/control" -- a space-separated list of address mappings, each
in the form of "from-address=to-address". The 'config' key
returns those address mappings set in the configuration; the 'cache'
key returns the mappings in the client-side DNS cache; the 'control'
key returns the mappings set via the control interface; the 'all'
target returns the mappings set through any mechanism.
3.13 INFOVALUE (Type 0x000C)
"circuit-status"
A series of lines as for a circuit status event. Each line is of the form:
CircuitID SP CircStatus SP Path CRLF
Sent from the server to the client in response to a GETINFO message.
Contains one or more items of the format:
"stream-status"
A series of lines as for a stream status event. Each is of the form:
StreamID SP StreamStatus SP Target CRLF
Key [(NUL-terminated string)]
Value [(NUL-terminated string)]
"orconn-status"
A series of lines as for a OR connection status event. Each is of the
form:
ServerID SP ORStatus CRLF
The keys match those given in the GETINFO message.
Examples:
C: GETINFO version desc/name/moria1
S: 250+desc/name/moria=
S: [Descriptor for moria]
S: .
S: 250-version=Tor 0.1.1.0-alpha-cvs
S: 250 OK
3.14 EXTENDCIRCUIT (Type 0x000D)
3.9 EXTENDCIRCUIT
Sent from the client to the server. The message body contains two fields:
Circuit ID [4 octets]
Path [NUL-terminated, comma-delimited string of OR nickname/identity]
Sent from the client to the server. The format is:
"EXTENDCIRCUIT" SP CircuitID SP SeverID *("," ServerID) CRLF
This request takes one of two forms: either the Circuit ID is zero, in
which case it is a request for the server to build a new circuit according
@ -361,15 +337,14 @@ the message.
request for the server to extend an existing circuit with that ID according
to the specified path.
If the request is successful, the server sends a DONE message containing
If the request is successful, the server sends a "250 OK" message containing
a message body consisting of the four-octet Circuit ID of the newly created
circuit.
3.15 ATTACHSTREAM (Type 0x000E)
3.10 ATTACHSTREAM
Sent from the client to the server. The message body contains two fields:
Stream ID [4 octets]
Circuit ID [4 octets]
Sent from the client to the server. The syntax is:
"ATTACHSTREAM" SP StreamID SP CircuitID CRLF
This message informs the server that the specified stream should be
associated with the specified circuit. Each stream may be associated with
@ -380,16 +355,20 @@ the message.
If the circuit ID is 0, responsibility for attaching the given stream is
returned to Tor.
Tor responds with "250 OK" if it can attach the stream, 552 if the circuit
or stream didn't exist, or 551 if the stream couldn't be attached for
another reason.
{Implementation note: By default, Tor automatically attaches streams to
circuits itself, unless the configuration variable
"__LeaveStreamsUnattached" is set to "1". Attempting to attach streams
via TC when "__LeaveStreamsUnattached" is false may cause a race between
Tor and the controller, as both attempt to attach streams to circuits.}
3.16 POSTDESCRIPTOR (Type 0x000F)
3.11 POSTDESCRIPTOR
Sent from the client to the server. The message body contains one field:
Descriptor [NUL-terminated string]
Sent from the client to the server. The syntax is:
"+POSTDESCRIPTOR" CRLF Descriptor CRLF "." CRLF
This message informs the server about a new descriptor.
@ -398,38 +377,13 @@ the message.
If there is an error in parsing the descriptor, the server must send an
appropriate error message. If the descriptor is well-formed but the server
chooses not to add it, it must reply with a DONE message whose body
chooses not to add it, it must reply with a 251 message whose body
explains why the server was not added.
3.17 FRAGMENTHEADER (Type 0x0010)
3.12 REDIRECTSTREAM
Sent in either direction. Used to encapsulate messages longer than 65535
bytes in length.
Underlying type [2 bytes]
Total Length [4 bytes]
Data [Rest of message]
A FRAGMENTHEADER message MUST be followed immediately by a number of
FRAGMENT messages, such that lengths of the "Data" fields of the
FRAGMENTHEADER and FRAGMENT messages add to the "Total Length" field of the
FRAGMENTHEADER message.
Implementations MUST NOT fragment messages of length less than 65536 bytes.
Implementations MUST be able to process fragmented messages that not
optimally packed.
3.18 FRAGMENT (Type 0x0011)
Data [Entire message]
See FRAGMENTHEADER for more information
3.19 REDIRECTSTREAM (Type 0x0012)
Sent from the client to the server. The message body contains two fields:
Stream ID [4 octets]
Address [variable-length, NUL-terminated.]
Sent from the client to the server. The syntax is:
"REDIRECTSTREAM" SP StreamID SP Address CRLF
Tells the server to change the exit address on the specified stream. No
remapping is performed on the new provided address.
@ -438,32 +392,183 @@ the message.
after a new stream event is received, and before attaching this stream to
a circuit.
3.20 CLOSESTREAM (Type 0x0013)
Tor replies with "250 OK" on success.
Sent from the client to the server. The message body contains three
fields:
Stream ID [4 octets]
Reason [1 octet]
Flags [1 octet]
3.13 CLOSESTREAM
Tells the server to close the specified stream. The reason should be
one of the Tor RELAY_END reasons given in tor-spec.txt. Flags is not
used currently. Tor may hold the stream open for a while to flush
any data that is pending.
Sent from the client to the server. The syntax is:
3.21 CLOSECIRCUIT (Type 0x0014)
"CLOSESTREAM" SP StreamID SP Reason *(SP Flag) CRLF
Sent from the client to the server. The message body contains two
fields:
Circuit ID [4 octets]
Flags [1 octet]
Tells the server to close the specified stream. The reason should be one
of the Tor RELAY_END reasons given in tor-spec.txt, as a decimal. Flags is
not used currently; Tor servers SHOULD ignore unrecognized flags. Tor may
hold the stream open for a while to flush any data that is pending.
Tells the server to close the specified circuit. If the LSB of the flags
field is nonzero, do not close the circuit unless it is unused.
3.14 CLOSECIRCUIT
4. Implementation notes
The syntax is:
CLOSECIRCUIT SP CircuitID *(SP Flag) CRLF
Flag = "IfUnused"
4.1. Authentication
Tells the server to close the specified circuit. If "IfUnused" is
provided, do not close the circuit unless it is unused.
Other flags may be defined in the future; Tor SHOULD ignore unrecognized
flags.
4 Replies
Reply codes follow the same 3-character format as used by SMTP, with the
first character defining a status, the second character defining a
subsystem, and the third designates fine-grained information.
The TC protocol currently uses the following first characters:
2yz Positive Completion Reply
The command was successful; a new request can be started.
4yz Temporary Negative Completion reply
The command was unsuccessful but might be reattempted later.
5yz Permanent Negative Completion Reply
The command was unsuccessful; the client should not try exactly
that sequence of commands again.
6yz Asynchronous Reply
Sent out-of-order in response to an earlier SETEVENTS command.
The following second characters are used:
x0z Syntax
Sent in response to ill-formed or nonsensical commands.
x1z Protocol
Refers to operations of the Tor Control protocol.
x2z Tor
Refers to actual operations of Tor system.
The following codes are defined:
250 OK
251 Operation was unnecessary
[Tor has declined to perform the operation, but no harm was done.]
451 Resource exhausted
500 Syntax error: protocol
510 Unrecognized command
511 Unimplemented command
512 Syntax error in command argument
513 Unrecognized command argument
514 Authentication required
515 Bad authentication
550 Unspecified Tor error
551 Internal error
[Something went wrong inside Tor, so that the client's
request couldn't be fulfilled.]
552 Unrecognized entity
[A configuration key, a stream ID, circuit ID, event,
mentioned in the command did not actually exist.]
553 Invalid configuration value
[The client tried to set a configuration option to an
incorrect, ill-formed, or impossible value.]
650 Asynchronous event notification
4.1 Anynchronous events
These replies can be sent after a corresponding SETEVENTS command has been
received. They will not be interleaved with other Reply elements, but they
can appear between a command and its corresponding reply. For example,
this sequence is possible:
C: SETEVENTS CIRC
S: 250 OK
C: GETCONFIG SOCKSPORT ORPORT
S: 650 CIRC 1000 EXTENDED moria1,moria2
S: 250-SOCKSPORT=9050
S: 250 ORPORT=0
But this sequence is disallowed:
C: SETEVENTS CIRC
S: 250 OK
C: GETCONFIG SOCKSPORT ORPORT
S: 250-SOCKSPORT=9050
S: 650 CIRC 1000 EXTENDED moria1,moria2
S: 250 ORPORT=0
4.1.1 Circuit status changed
The syntax is:
"650" SP "CIRC" SP CircuitID SP CircStatus SP Path
CircStatus =
"LAUNCHED" / ; circuit ID assigned to new circuit
"BUILT" / ; all hops finished, can now accept streams
"EXTENDED" / ; one more hop has been completed
"FAILED" / ; circuit closed (was not built)
"CLOSED" ; circuit closed (was built)
Path = ServerID *("," ServerID)
4.1.2. Stream status changed
The syntax is:
"650" SP "STREAM" SP StreamID SP StreamStatus SP Target
StreamStatus =
"NEW" / ; New request to connect
"NEWRESOLVE" / ; New request to resolve an address
"SENTCONNECT" / ; Sent a connect cell along a circuit
"SENTRESOLVE" / ; Sent a resolve cell along a circuit
"SUCCEEDED" / ; Received a successful reply; stream established
"FAILED" / ; Stream failed and not retriable.
"CLOSED" / ; Stream closed
"DETACHED" ; Stream detached from circuit; still retriable
Target = Address ":" Port
4.1.3 OR Connection status changed
The syntax is:
"650" SP "ORCONN" SP ServerID SP ORStatus
ORStatus = "LAUNCHED" / "CONNECTED" / "FAILED" / "CLOSED"
4.1.3 Bandwidth used in the last second
The syntax is:
"650" SP "BW" SP BytesRead SP BytesWritten
BytesRead = 1*DIGIT
BytesWritten = 1*DIGIT
4.1.4 Log message
The syntax is:
"650" SP Severity SP ReplyText
or
"650+" Severity CRLF Data
Severity = "DEBUG" / "INFO" / "NOTICE" / "WARN"/ "ERR"
4.1.5 New descriptors available
Syntax:
"650" SP "NEWDESC" 1*(SP ServerID)
5. Implementation notes
5.1. Authentication
By default, the current Tor implementation trusts all local users.
@ -486,8 +591,14 @@ the message.
To authenticate under this scheme, the controller sends Tor the original
secret that was used to generate the password.
4.2. Don't let the buffer get too big.
5.2. Don't let the buffer get too big.
If you ask for lots of events, and 16MB of them queue up on the buffer,
the Tor process will close the socket.
5.3. Backward compatibility
For backward compatibility with the "version 0" control protocol, Tor checks
whether the third byte the first command is zero. If it is, Tor
assumes that version 0 is in use. This feature is deprecated, and will be
removed in the 0.1.2.x Tor development series.