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bfdb93d8bd
tor/doc/control-spec.txt
Nick Mathewson bfdb93d8bd r9272@Kushana: nickm | 2006-10-19 12:52:37 -0400 
Fix an XXX in handling destroy cells: when we get a destroy cell with reason FOO, do not tell the controller REASON=FOO.  Instead, say REASON=DESTROYED REMOTE_REASON=FOO. Suggested by a conversation with Mike Perry.


svn:r8760
2006-10-19 23:04:49 +00:00

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$Id$
TC: A Tor control protocol (Version 1)
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 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. (Version 0 is used by Tor
versions 0.1.0.x; the protocol in this document only works with Tor
versions in the 0.1.1.x series and later.)
1. Protocol outline
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 (or "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 messages to each other over the
underlying stream. The client sends "commands" and the server sends
"replies".
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 as such.
Servers respond to messages in the order messages are received.
2. Message format
2.1. Description format
The message formats listed below use ABNF as described in RFC2234.
The protocol itself is loosely based on SMTP (see RFC 2821).
We use the following nonterminals from RFC2822: atom, qcontent
We define the following general-use nonterminals:
String = DQUOTE *qcontent DQUOTE
There are explicitly no limits on line length. All 8-bit characters are
permitted unless explicitly disallowed.
2.2. Commands from controller to Tor
Command = Keyword Arguments CRLF / "+" Keyword Arguments CRLF Data
Keyword = 1*ALPHA
Arguments = *(SP / VCHAR)
Specific commands and their arguments are described below in section 3.
2.3. Replies from Tor to the controller
Reply = *(MidReplyLine / DataReplyLine) EndReplyLine
MidReplyLine = "-" ReplyLine
DataReplyLine = "+" ReplyLine Data
EndReplyLine = SP ReplyLine
ReplyLine = StatusCode [ SP ReplyText ] CRLF
ReplyText = XXXX
StatusCode = XXXX
Specific replies are mentioned below in section 3, and described more fully
in section 4.
2.4. General-use tokens
; Identifiers for servers.
ServerID = Nickname / Fingerprint
Nickname = 1*19 NicknameChar
NicknameChar = "a"-"z" / "A"-"Z" / "0" - "9"
Fingerprint = "$" 40*HEXDIG
; A "=" indicates that the given nickname is canonical; a "~" indicates
; that the given nickname is not canonical.
LongName = Fingerprint [ ( "=" / "~" ) Nickname ]
; How a controller tells Tor about a particular OR. There are four
; possible formats:
; $Digest -- The router whose identity key hashes to the given digest.
; This is the preferred way to refer to an OR.
; $Digest~Name -- The router whose identity key hashes to the given
; digest, but only if the router has the given nickname.
; $Digest=Name -- The router whose identity key hashes to the given
; digest, but only if the router is Named and has the given
; nickname.
; Name -- The Named router with the given nickname, or, if no such
; router exists, any router whose nickname matches the one given.
; This is not a safe way to refer to routers, since Named status
; could under some circumstances change over time.
ServerSpec = LongName / Nickname
; 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
Address = ip4-address / ip6-address / hostname (XXXX Define these)
; 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
3. Commands
All commands and other keywords are case-insensitive.
3.1. SETCONF
Change the value of one or more configuration variables. The syntax is:
"SETCONF" 1*(SP keyword ["=" String]) CRLF
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 0 or NULL (use RESETCONF if you want
to set it back to its default). SETCONF is all-or-nothing: if there
is an error in any of the configuration settings, Tor sets none of them.
Tor responds with a "250 configuration values set" reply on success.
If some of the listed keywords can't be found, Tor replies with a
"552 Unrecognized option" message. Otherwise, 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 option takes multiple values, or when multiple
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.
3.2. RESETCONF
Remove all settings for a given configuration option entirely, assign
its default value (if any), and then assign the String provided.
Typically the String is left empty, to simply set an option back to
its default. The syntax is:
"RESETCONF" 1*(SP keyword ["=" String]) CRLF
Otherwise it behaves like SETCONF above.
3.3. GETCONF
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 any option is set to a 'default' value semantically different from an
empty string, Tor may reply with a reply line of the form:
250 keyword
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.
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.
3.4. SETEVENTS
Request the server to inform the client about interesting events. The
syntax is:
"SETEVENTS" [SP "EXTENDED"] *(SP EventCode) CRLF
EventCode = "CIRC" / "STREAM" / "ORCONN" / "BW" / "DEBUG" /
"INFO" / "NOTICE" / "WARN" / "ERR" / "NEWDESC" / "ADDRMAP" /
"AUTHDIR_NEWDESCS" / "DESCCHANGED" / "STATUS_GENERAL" /
"STATUS_CLIENT" / "STATUS_SERVER" / "GUARDS"
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 "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.)
If the flag string "EXTENDED" is provided, Tor may provide extra
information with events for this connection; see 4.1 for more information.
NOTE: All events on a given connection will be provided in extended format,
or none.
NOTE: "EXTENDED" is only supported in Tor 0.1.1.9-alpha or later.
Each event is described in more detail in Section 4.1.
3.5. AUTHENTICATE
Sent from the client to the server. The syntax is:
"AUTHENTICATE" [ SP 1*HEXDIG / QuotedString ] CRLF
The server responds with "250 OK" on success or "515 Bad authentication" if
the authentication cookie is incorrect.
The format of the 'cookie' is implementation-dependent; see 5.1 below for
information on how the standard Tor implementation handles it.
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.
3.6. SAVECONF
Sent from the client to the server. The syntax is:
"SAVECONF" CRLF
Instructs the server to write out its config options into its torrc. Server
returns "250 OK" if successful, or "551 Unable to write configuration
to disk" if it can't write the file or some other error occurs.
3.7. SIGNAL
Sent from the client to the server. The syntax is:
"SIGNAL" SP Signal CRLF
Signal = "RELOAD" / "SHUTDOWN" / "DUMP" / "DEBUG" / "HALT" /
"HUP" / "INT" / "USR1" / "USR2" / "TERM" / "NEWNYM"
The meaning of the signals are:
RELOAD -- Reload: reload config items, refetch directory. (like HUP)
SHUTDOWN -- Controlled shutdown: if server is an OP, exit immediately.
If it's an OR, close listeners and exit after 30 seconds.
(like INT)
DUMP -- Dump stats: log information about open connections and
circuits. (like USR1)
DEBUG -- Debug: switch all open logs to loglevel debug. (like USR2)
HALT -- Immediate shutdown: clean up and exit now. (like TERM)
NEWNYM -- Switch to clean circuits, so new application requests
don't share any circuits with old ones.
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.
3.8. MAPADDRESS
Sent from the client to the server. The syntax is:
"MAPADDRESS" 1*(Address "=" Address SP) CRLF
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 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.
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.
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:
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.}
Mappings set by the controller last until the Tor process exits:
they never expire. If the controller wants the mapping to last only
a certain time, then it must explicitly un-map the address when that
time has elapsed.
3.9. GETINFO
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, or a 551 or 552 error.
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 a value must be split over multiple lines, the format is:
250+keyword=
value
.
Recognized keys and their values include:
"version" -- The version of the server's software, including the name
of the software. (example: "Tor 0.0.9.4")
"config-file" -- The location of Tor's configuration file ("torrc").
["exit-policy/prepend" -- The default exit policy lines that Tor will
*prepend* to the ExitPolicy config option.
-- Never implemented. Useful?]
"exit-policy/default" -- The default exit policy lines that Tor will
*append* to the ExitPolicy config option.
"desc/id/<OR identity>" or "desc/name/<OR nickname>" -- the latest
server descriptor for a given OR, NUL-terminated.
"desc/all-recent" -- the latest server descriptor for every router that
Tor knows about.
"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 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.
"address" -- the best guess at our external IP address. If we
have no guess, return a 551 error. (Added in 0.1.2.2-alpha)
"fingerprint" -- the contents of the fingerprint file that Tor
writes as a server, or a 551 if we're not a server currently.
(Added in 0.1.2.3-alpha)
"circuit-status"
A series of lines as for a circuit status event. Each line is of
the form:
CircuitID SP CircStatus [SP Path] CRLF
"stream-status"
A series of lines as for a stream status event. Each is of the form:
StreamID SP StreamStatus SP CircID SP Target CRLF
"orconn-status"
A series of lines as for an OR connection status event. Each is of the
form:
ServerID SP ORStatus CRLF
"entry-guards"
A series of lines listing the currently chosen entry guards, if any.
Each is of the form:
ServerID SP (Status-with-time / Status) CRLF
Status-with-time = ("down" / "unlisted") SP ISOTime
Status = ("up" / "never-connected")
[From 0.1.1.4-alpha to 0.1.1.10-alpha, this was called "helper-nodes".
Tor still supports calling it that for now, but support will be
removed in 0.1.3.x.]
"accounting/enabled"
"accounting/hibernating"
"accounting/bytes"
"accounting/bytes-left"
"accounting/interval-start"
"accounting/interval-wake"
"accounting/interval-end"
Information about accounting status. If accounting is enabled,
"enabled" is 1; otherwise it is 0. The "hibernating" field is "hard"
if we are accepting no data; "soft" if we're accepting no new
connections, and "awake" if we're not hibernating at all. The "bytes"
and "bytes-left" fields contain (read-bytes SP write-bytes), for the
start and the rest of the interval respectively. The 'interval-start'
and 'interval-end' fields are the borders of the current interval; the
'interval-wake' field is the time within the current interval (if any)
where we plan[ned] to start being active.
"config/names"
A series of lines listing the available configuration options. Each is
of the form:
OptionName SP OptionType [ SP Documentation ] CRLF
OptionName = Keyword
OptionType = "Integer" / "TimeInterval" / "DataSize" / "Float" /
"Boolean" / "Time" / "CommaList" / "Dependant" / "Virtual" /
"String" / "LineList"
Documentation = Text
"info/names"
A series of lines listing the available GETINFO options. Each is of
one of these forms:
OptionName SP Documentation CRLF
OptionPrefix SP Documentation CRLF
OptionPrefix = OptionName "/*"
"dir/status/authority"
"dir/status/fp/<F>"
"dir/status/fp/<F1>+<F2>+<F3>"
"dir/status/all"
"dir/server/fp/<F>"
"dir/server/fp/<F1>+<F2>+<F3>"
"dir/server/d/<D>"
"dir/server/d/<D1>+<D2>+<D3>"
"dir/server/authority"
"dir/server/all"
A series of lines listing directory contents, provided according to the
specification for the URLs listed in Section 4.4 of dir-spec.txt. Note
that Tor MUST NOT provide private information, such as descriptors for
routers not marked as general-purpose. When asked for 'authority'
information for which this Tor is not authoritative, Tor replies with
an empty string.
"status/circuit-established"
"status/..."
These provide the current internal Tor values for various Tor
states. See Section 4.1.10 for explanations. (Only a few of the
status events are available as getinfo's currently. Let us know if
you want more exposed.)
"status/client"
"status/server"
These two special cases of internal Tor values return a (possibly
empty) list of status events from Section 4.1.10 that Tor believes
are still accurate. Controllers can use them to get a summary of
any current problems with Tor's operation.
[The answers should include notice events, not just warns and
errs, for example so Tor can learn whether any circuits have been
established yet.-RD]
[notice, warn, and errs need to be separated here, though.
Otherwise, when we add a new status event type in the future,
controllers won't know whether it's good or bad. -NM]
[Does this mean that Tor must keep state on its side of all the
statuses it's sent, and recognize when they're cancelled out,
and so on? It's a shame that Tor needs to do this and also Vidalia
needs to do this. -RD]
[Is there a good alternative? If we want controllers who connect
to a running Tor to see its status, I think we need to do this. -NM]
[What is the format of this list? Is it space-separated,
newline-separated? Does it include keywords, arguments, etc? Also,
what about STATUS_GENERAL? -NM]
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
3.10. EXTENDCIRCUIT
Sent from the client to the server. The format is:
"EXTENDCIRCUIT" SP CircuitID SP
ServerSpec *("," ServerSpec) SP
("purpose=" Purpose) CRLF
This request takes one of two forms: either the CircuitID is zero, in
which case it is a request for the server to build a new circuit according
to the specified path, or the CircuitID 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 CircuitID is 0 and "purpose=" is specified, then the circuit's
purpose is set. Two choices are recognized: "general" and
"controller". If not specified, circuits are created as "general".
If the request is successful, the server sends a reply containing a
message body consisting of the CircuitID of the (maybe newly created)
circuit. The syntax is "250" SP "EXTENDED" SP CircuitID CRLF.
3.11. SETCIRCUITPURPOSE
Sent from the client to the server. The format is:
"SETCIRCUITPURPOSE" SP CircuitID SP Purpose CRLF
This changes the circuit's purpose. See EXTENDCIRCUIT above for details.
3.12. SETROUTERPURPOSE
Sent from the client to the server. The format is:
"SETROUTERPURPOSE" SP NicknameOrKey SP Purpose CRLF
This changes the descriptor's purpose. See +POSTDESCRIPTOR below
for details.
3.13. ATTACHSTREAM
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
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 or are listed as built in a
GETINFO circuit-status request).
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: Tor will close unattached streams by itself,
roughly two minutes after they are born. Let the developers know if
that turns out to be a problem.}
{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.}
{Implementation note: You can try to attachstream to a stream that
has already sent a connect or resolve request but hasn't succeeded
yet, in which case Tor will detach the stream from its current circuit
before proceeding with the new attach request.}
3.14. POSTDESCRIPTOR
Sent from the client to the server. The syntax is:
"+POSTDESCRIPTOR" ("purpose=" Purpose) CRLF Descriptor CRLF "." CRLF
This message informs the server about a new descriptor. If Purpose is
specified, it must be either "general" or "controller", else we
return a 552 error.
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 a "554
Invalid descriptor" reply. If the descriptor is well-formed but the server
chooses not to add it, it must reply with a 251 message whose body explains
why the server was not added. If the descriptor is added, Tor replies with
"250 OK".
3.15. REDIRECTSTREAM
Sent from the client to the server. The syntax is:
"REDIRECTSTREAM" SP StreamID SP Address (SP Port) CRLF
Tells the server to change the exit address on the specified stream. If
Port is specified, changes the destination port as well. 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.
Tor replies with "250 OK" on success.
3.16. CLOSESTREAM
Sent from the client to the server. The syntax is:
"CLOSESTREAM" SP StreamID SP Reason *(SP Flag) CRLF
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.
Tor replies with "250 OK" on success, or a 512 if there aren't enough
arguments, or a 552 if it doesn't recognize the StreamID or reason.
3.17. CLOSECIRCUIT
The syntax is:
CLOSECIRCUIT SP CircuitID *(SP Flag) CRLF
Flag = "IfUnused"
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.
Tor replies with "250 OK" on success, or a 512 if there aren't enough
arguments, or a 552 if it doesn't recognize the CircuitID.
3.18. QUIT
Tells the server to hang up on this controller connection. This command
can be used before authenticating.
3.19. USEFEATURE
The syntax is:
"USEFEATURE" *(SP FeatureName) CRLF
FeatureName = 1*(ALPHA / DIGIT / "_" / "-")
Sometimes extensions to the controller protocol break compatibility with
older controllers. In this case, whenever possible, the extensions are
first included in Tor disabled by default, and only enabled on a given
controller connection when the "USEFEATURE" command is given. Once a
"USEFEATURE" command is given, it applies to all subsequent interactions on
the same connection; to disable an enabled feature, a new controller
connection must be opened.
This is a forward-compatibility mechanism; each feature will eventually
become a regular part of the control protocol in some future version of Tor.
Tor will ignore a request to use any feature that is already on by default.
Tor will give a "552" error if any requested feature is not recognized.
Feature names are case-insensitive.
EXTENDED_EVENTS
Same as passing 'EXTENDED' to SETEVENTS; this is the preferred way to
request the extended event syntax.
This will not be always-enabled until at least XXX (or, at least two
stable releases after XXX, the release where it was first used for
anything.)
VERBOSE_NAMES
Instead of ServerID as specified above, the controller should
identify ORs by LongName in events and GETINFO results. This format is
strictly more informative: rather than including Nickname for
known Named routers and Fingerprint for unknown or unNamed routers, the
LongName format includes a Fingerprint, an indication of Named status,
and a Nickname (if one is known).
This will not be always-enabled until at least 0.1.4.x (or at least two
stable releases after 0.1.2.2-alpha, the release where it was first
available.)
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 designating 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.
x5z 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.]
554 Invalid descriptor
555 Unmanaged entity
650 Asynchronous event notification
Unless specified to have specific contents, the human-readable messages
in error replies should not be relied upon to match those in this document.
4.1. Asynchronous 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: GETCONF 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: GETCONF SOCKSPORT ORPORT
S: 250-SOCKSPORT=9050
S: 650 CIRC 1000 EXTENDED moria1,moria2
S: 250 ORPORT=0
Clients SHOULD tolerate more arguments in an asynchonous reply than
expected, and SHOULD tolerate more lines in an asynchronous reply than
expected. For instance, a client that expects a CIRC message like:
650 CIRC 1000 EXTENDED moria1,moria2
should tolerate:
650-CIRC 1000 EXTENDED moria1,moria2 0xBEEF
650-EXTRAMAGIC=99
650 ANONYMITY=high
If clients ask for extended events, then each event line as specified below
will be followed by additional extensions. Clients that do so MUST
tolerate additional arguments and lines. Additional lines will be of the
form
"650" ("-"/" ") KEYWORD ["=" ARGUMENTS] CRLF
Additional arguments will be of the form
SP KEYWORD ["=" ( QuotedString / * NonSpDquote ) ]
Such clients MUST tolerate lines with keywords they do not recognize.
4.1.1. Circuit status changed
The syntax is:
"650" SP "CIRC" SP CircuitID SP CircStatus [SP Path]
[SP "REASON=" Reason [SP "REMOTE_REASON=" Reason]] CRLF
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)
Reason = "NONE" / "TORPROTOCOL" / "INTERNAL" / "REQUESTED" /
"HIBERNATING" / "RESOURCELIMIT" / "CONNECTFAILED" /
"OR_IDENTITY" / "OR_CONN_CLOSED" / "TIMEOUT" /
"FINISHED" / "DESTROYED" / "NOPATH" / "NOSUCHSERVICE"
The path is provided only when the circuit has been extended at least one
hop.
The "REASON" field is provided only for FAILED and CLOSED events, and only
if extended events are enabled (see 3.19). Clients MUST accept reasons
not listed above. Reasons are as given in tor-spec.txt, except for:
NOPATH (Not enough nodes to make circuit)
The "REMOTE_REASON" field is provided only when we receive a DESTROY or
TRUNCATE cell, and only if extended events are enabled. It contains the
actual reason given by the remote OR for closing the circuit. Clients MUST
accept reasons not listed above. Reasons are as listed in tor-spec.txt.
4.1.2. Stream status changed
The syntax is:
"650" SP "STREAM" SP StreamID SP StreamStatus SP CircID 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 reply; stream established
"FAILED" / ; Stream failed and not retriable
"CLOSED" / ; Stream closed
"DETACHED" ; Detached from circuit; still retriable
Target = Address ":" Port
The circuit ID designates which circuit this stream is attached to. If
the stream is unattached, the circuit ID "0" is given.
4.1.3. OR Connection status changed
The syntax is:
"650" SP "ORCONN" SP (ServerID / Target) SP ORStatus
ORStatus = "NEW" / "LAUNCHED" / "CONNECTED" / "FAILED" / "CLOSED"
NEW is for incoming connections, and LAUNCHED is for outgoing
connections. CONNECTED means the TLS handshake has finished (in
either direction). FAILED means a connection is being closed that
hasn't finished its handshake, and CLOSED is for connections that
have handshaked.
A ServerID is specified unless it's a NEW connection, in which
case we don't know what server it is yet, so we use Address:Port.
4.1.4. Bandwidth used in the last second
The syntax is:
"650" SP "BW" SP BytesRead SP BytesWritten
BytesRead = 1*DIGIT
BytesWritten = 1*DIGIT
4.1.5. Log messages
The syntax is:
"650" SP Severity SP ReplyText
or
"650+" Severity CRLF Data
Severity = "DEBUG" / "INFO" / "NOTICE" / "WARN"/ "ERR"
4.1.6. New descriptors available
Syntax:
"650" SP "NEWDESC" 1*(SP ServerID)
4.1.7. New Address mapping
Syntax:
"650" SP "ADDRMAP" SP Address SP Address SP Expiry
Expiry = DQOUTE ISOTime DQUOTE / "NEVER"
4.1.8. Descriptors uploaded to us in our role as authoritative dirserver
Syntax:
"650" "+" "AUTHDIR_NEWDESCS" CRLF Action CRLF Message CRLF
Descriptor CRLF "." CRLF
Action = "ACCEPTED" / "DROPPED" / "REJECTED"
Message = Text
4.1.9. Our descriptor changed
Syntax:
"650" SP "DESCCHANGED"
[First added in 0.1.2.2-alpha.]
4.1.10. Status events
[Don't rely on any of these until we work out more of the details. -RD]
Syntax:
"650" SP Type SP Severity SP Action SP Arguments
Type = "STATUS_GENERAL" / "STATUS_CLIENT" / "STATUS_SERVER"
Severity = "NOTICE" / "WARN" / "ERR"
Action is a string, and Arguments is a series of key=value
pairs on the same line.
The reserved keyword "message" can optionally be used to provide a
string describing the nature of the action. Message strings MUST
NOT include items that a controller might be tempted to parse,
such as numbers.
Actions for STATUS_GENERAL severity NOTICE events can be as follows:
[none yet]
Actions for STATUS_GENERAL severity WARN events can be as follows:
DANGEROUS_VERSION
"current=version"
"recommended=version,version,..."
"reason=new/old/unrecommended"
CLOCK_JUMPED
"time=NUM"
Tor spent enough time without CPU cycles that it has closed all
its circuits and will establishing them anew. This typically
happens when a laptop goes to sleep and then wakes up again. It
also happens when the system is swapping so heavily that Tor is
starving. The "time" argument includes the number of seconds Tor
thinks it was unconscious for.
[This status event can generally be ignored by the controller,
since we don't really know what the user should do anyway. Hm.]
TOO_MANY_CONNECTIONS
"limit=NUM"
Tor has reached its ulimit -n or whatever the native limit is on
file descriptors or sockets. The user should really do something
about this. The "limit" argument shows the number of connections
currently open.
BUG
"reason=STRING"
Tor has encountered a situation that its developers never expected,
and the developers would like to learn that it happened. Perhaps
the controller can explain this to the user and encourage her to
file a bug report?
[The following two are sent as WARNs if CIRCUIT_ESTABLISHED and
not DIR_ALL_UNREACHABLE, else as ERRs:]
BAD_DIR_RESPONSE
// unexpected dir response. behind a hotel/airport firewall?
CLOCK_SKEWED
// (either from talking to a dir authority, or from perusing a
// network-status timestamp)
Actions for STATUS_GENERAL severity ERR events can be as follows:
BAD_PROXY
// bad http or https proxy?
DIR_ALL_UNREACHABLE
Tor believes that none of the known directory servers are
reachable -- this is most likely because the local network is
down or otherwise not working, and might help to explain for the
user why Tor appears to be broken.
Actions for STATUS_CLIENT severity NOTICE events can be as follows:
CIRCUIT_ESTABLISHED
Tor is able to establish circuits for client use. This event will
only be sent if we just built a circuit that changed our mind --
that is, prior to this event we didn't know whether we could
establish circuits.
ENOUGH_DIR_INFO
Tor now knows enough network-status documents and enough server
descriptors that it's going to start trying to build circuits now.
Actions for STATUS_CLIENT severity WARN events can be as follows:
DANGEROUS_SOCKS
"protocol=socks4/socks4a/socks5"
"address=IP:port"
SOCKS_UNKNOWN_PROTOCOL
A connection was made to Tor's SOCKS port that tried to use it
for something other than the SOCKS protocol. Perhaps the user is
using Tor as an HTTP proxy?
BAD_HOSTNAME
// a nickname we asked for is unavailable. no need for this
// quite yet, since no end-user controllers let you configure that.
Actions for STATUS_CLIENT severity ERR events can be as follows:
[none yet]
Actions for STATUS_SERVER severity NOTICE events can be as follows:
EXTERNAL_ADDRESS
"address=IP"
"method=guessed/resolved/..."
// hibernating
CHECKING_REACHABILITY
"oraddress=IP:port"
"diraddress=IP:port"
"timeout=NUM"
GOOD_SERVER_DESCRIPTOR
We successfully uploaded our server descriptor to each of the
directory authorities, with no complaints.
Actions for STATUS_SERVER severity WARN events can be as follows:
// something about failing to parse our address?
// from resolve_my_address() in config.c
// sketchy libevent, sketchy OS, sketchy threading
// too many onions queued. threading problem or slow cpu?
// eventdns statements. like, hijacked dns.
BAD_SERVER_DESCRIPTOR
"dirauth=nickname"
// dir authorities didn't like my descriptor
Actions for STATUS_SERVER severity ERR events can be as follows:
REACHABILITY_FAILED
"oraddress=IP:port"
"diraddress=IP:port"
Controllers must tolerate hearing about actions that they don't
recognize.
4.1.11. Our set of guard nodes has changed
Syntax:
"650" SP "GUARDS" SP Type SP ...
Type = "ENTRY"
...
[needs to be fleshed out; not implemented yet]
5. Implementation notes
5.1. 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, encoded in hexadecimal.
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.
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 with v0 control protocol.
For backward compatibility with the "version 0" control protocol, Tor checks
whether the third octet 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 0.1.3.x Tor development series.
In order to detect which version of the protocol is supported controllers
should send the sequence [00 00 0D 0A]. This is a valid and unrecognized
command in both protocol versions, and implementations can detect which
error they have received.
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