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author | Nick Mathewson <nickm@torproject.org> | 2007-01-26 01:59:50 +0000 |
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committer | Nick Mathewson <nickm@torproject.org> | 2007-01-26 01:59:50 +0000 |
commit | 489f6185bff08278e648d944ec1a9b2d03443d21 (patch) | |
tree | ded178e269afc641461a820cb3a387feb3a4069e /doc/rend-spec.txt | |
parent | d996db90b38dac225f6cda6dffdc3807a4c3d822 (diff) | |
download | tor-489f6185bff08278e648d944ec1a9b2d03443d21.tar tor-489f6185bff08278e648d944ec1a9b2d03443d21.tar.gz |
Move specification documents into new doc/spec subdirectory. (Proposals, drafts, and bad ideas still remain in doc.)
svn:r9411
Diffstat (limited to 'doc/rend-spec.txt')
-rw-r--r-- | doc/rend-spec.txt | 449 |
1 files changed, 0 insertions, 449 deletions
diff --git a/doc/rend-spec.txt b/doc/rend-spec.txt deleted file mode 100644 index 8259ecec2..000000000 --- a/doc/rend-spec.txt +++ /dev/null @@ -1,449 +0,0 @@ -$Id$ - - Tor Rendezvous Specification - -0. Overview and preliminaries - - Read http://tor.eff.org/doc/design-paper/tor-design.html#sec:rendezvous - before you read this specification. It will make more sense. - - Rendezvous points provide location-hidden services (server - anonymity) for the onion routing network. With rendezvous points, - Bob can offer a TCP service (say, a webserver) via the onion - routing network, without revealing the IP of that service. - - Bob does this by anonymously advertising a public key for his - service, along with a list of onion routers to act as "Introduction - Points" for his service. He creates forward circuits to those - introduction points, and tells them about his public key. To - connect to Bob, Alice first builds a circuit to an OR to act as - her "Rendezvous Point." She then connects to one of Bob's chosen - introduction points, optionally provides authentication or - authorization information, and asks it to tell him about her Rendezvous - Point (RP). If Bob chooses to answer, he builds a circuit to her - RP, and tells it to connect him to Alice. The RP joins their - circuits together, and begins relaying cells. Alice's 'BEGIN' - cells are received directly by Bob's OP, which passes data to - and from the local server implementing Bob's service. - - Below we describe a network-level specification of this service, - along with interfaces to make this process transparent to Alice - (so long as she is using an OP). - -0.1. Notation, conventions and prerequisites - - In the specifications below, we use the same notation as in - "tor-spec.txt". The service specified here also requires the - existence of an onion routing network as specified in that file. - - H(x) is a SHA1 digest of x. - PKSign(SK,x) is a PKCS.1-padded RSA signature of x with SK. - PKEncrypt(SK,x) is a PKCS.1-padded RSA encryption of x with SK. - Public keys are all RSA, and encoded in ASN.1. - All integers are stored in network (big-endian) order. - All symmetric encryption uses AES in counter mode, except where - otherwise noted. - - In all discussions, "Alice" will refer to a user connecting to a - location-hidden service, and "Bob" will refer to a user running a - location-hidden service. - -0.2. Protocol outline - - 1. Bob->Bob's OP: "Offer IP:Port as - public-key-name:Port". [configuration] - (We do not specify this step; it is left to the implementor of - Bob's OP.) - - 2. Bob's OP generates keypair and rendezvous service descriptor: - "Meet public-key X at introduction point A, B, or C." (signed) - - 3. Bob's OP->Introduction point via Tor: [introduction setup] - "This pk is me." - - 4. Bob's OP->directory service via Tor: publishes Bob's service - descriptor [advertisement] - - 5. Out of band, Alice receives a [x.y.]z.onion:port address. - She opens a SOCKS connection to her OP, and requests - x.y.z.onion:port. - - 6. Alice's OP retrieves Bob's descriptor via Tor. [descriptor lookup.] - - 7. Alice's OP chooses a rendezvous point, opens a circuit to that - rendezvous point, and establishes a rendezvous circuit. [rendezvous - setup.] - - 8. Alice connects to the Introduction point via Tor, and tells it about - her rendezvous point and optional authentication/authorization - information. (Encrypted to Bob.) [Introduction 1] - - 9. The Introduction point passes this on to Bob's OP via Tor, along the - introduction circuit. [Introduction 2] - - 10. Bob's OP decides whether to connect to Alice, and if so, creates a - circuit to Alice's RP via Tor. Establishes a shared circuit. - [Rendezvous.] - - 11. Alice's OP sends begin cells to Bob's OP. [Connection] - -0.3. Constants and new cell types - - Relay cell types - 32 -- RELAY_ESTABLISH_INTRO - 33 -- RELAY_ESTABLISH_RENDEZVOUS - 34 -- RELAY_INTRODUCE1 - 35 -- RELAY_INTRODUCE2 - 36 -- RELAY_RENDEZVOUS1 - 37 -- RELAY_RENDEZVOUS2 - 38 -- RELAY_INTRO_ESTABLISHED - 39 -- RELAY_RENDEZVOUS_ESTABLISHED - 40 -- RELAY_COMMAND_INTRODUCE_ACK - -1. The Protocol - -1.1. Bob configures his local OP. - - We do not specify a format for the OP configuration file. However, - OPs SHOULD allow Bob to provide more than one advertised service - per OP, and MUST allow Bob to specify one or more virtual ports per - service. Bob provides a mapping from each of these virtual ports - to a local IP:Port pair. - -1.2. Bob's OP generates service descriptors. - - The first time the OP provides an advertised service, it generates - a public/private keypair (stored locally). Periodically, the OP - generates a pair of service descriptors, one "V1" and one "V0". - - The "V1" descriptor in 0.1.1.6-alpha contains: - - V Format byte: set to 255 [1 octet] - V Version byte: set to 1 [1 octet] - KL Key length [2 octets] - PK Bob's public key [KL octets] - TS A timestamp [4 octets] - PROTO Rendezvous protocol versions: bitmask [2 octets] - NA Number of auth mechanisms accepted [1 octet] - For each auth mechanism: - AUTHT The auth type that is supported [2 octets] - AUTHL Length of auth data [1 octet] - AUTHD Auth data [variable] - NI Number of introduction points [2 octets] - For each introduction point: (as in INTRODUCE2 cells) - ATYPE An address type (typically 4) [1 octet] - ADDR Introduction point's IP address [4 or 16 octets] - PORT Introduction point's OR port [2 octets] - AUTHT The auth type that is supported [2 octets] - AUTHL Length of auth data [1 octet] - AUTHD Auth data [variable] - ID Introduction point identity ID [20 octets] - KLEN Length of onion key [2 octets] - KEY Introduction point onion key [KLEN octets] - SIG Signature of above fields [variable] - - The "V1" descriptor in 0.1.1.5-alpha-cvs contains: - - V Format byte: set to 255 [1 octet] - V Version byte: set to 1 [1 octet] - KL Key length [2 octets] - PK Bob's public key [KL octets] - TS A timestamp [4 octets] - PROTO Protocol versions: bitmask [2 octets] - NI Number of introduction points [2 octets] - For each introduction point: (as in INTRODUCE2 cells) - IP Introduction point's address [4 octets] - PORT Introduction point's OR port [2 octets] - ID Introduction point identity ID [20 octets] - KLEN Length of onion key [2 octets] - KEY Introduction point onion key [KLEN octets] - SIG Signature of above fields [variable] - - The "V0" descriptor contains: - - KL Key length [2 octets] - PK Bob's public key [KL octets] - TS A timestamp [4 octets] - NI Number of introduction points [2 octets] - Ipt A list of NUL-terminated ORs [variable] - SIG Signature of above fields [variable] - - KL is the length of PK, in octets. - TS is the number of seconds elapsed since Jan 1, 1970. - - AUTHT specifies which authentication/authorization mechanism is - required by the hidden service or the introduction point. AUTHD - is arbitrary data that can be associated with an auth approach. - Currently only AUTHT of [00 00] is supported, with an AUTHL of 0. - See section 2 of this document for details on auth mechanisms. - - The members of Ipt may be either (a) nicknames, or (b) identity key - digests, encoded in hex, and prefixed with a '$'. Clients must - accept both forms. Services must only generate the second form. - Once 0.0.9.x is obsoleted, we can drop the first form. - - [It's ok for Bob to advertise 0 introduction points. He might want - to do that if he previously advertised some introduction points, - and now he doesn't have any. -RD] - - [Once Tor 0.1.0.x is obsolete, we can stop generating or using V0 - descriptors. -NM] - -1.3. Bob's OP establishes his introduction points. - - The OP establishes a new introduction circuit to each introduction - point. These circuits MUST NOT be used for anything but rendezvous - introduction. To establish the introduction, Bob sends a - RELAY_ESTABLISH_INTRO cell, containing: - - KL Key length [2 octets] - PK Bob's public key [KL octets] - HS Hash of session info [20 octets] - SIG Signature of above information [variable] - - [XXX011, need to add auth information here. -RD] - - To prevent replay attacks, the HS field contains a SHA-1 hash based on the - shared secret KH between Bob's OP and the introduction point, as - follows: - HS = H(KH | "INTRODUCE") - That is: - HS = H(KH | [49 4E 54 52 4F 44 55 43 45]) - (KH, as specified in tor-spec.txt, is H(g^xy | [00]) .) - - Upon receiving such a cell, the OR first checks that the signature is - correct with the included public key. If so, it checks whether HS is - correct given the shared state between Bob's OP and the OR. If either - check fails, the OP discards the cell; otherwise, it associates the - circuit with Bob's public key, and dissociates any other circuits - currently associated with PK. On success, the OR sends Bob a - RELAY_INTRO_ESTABLISHED cell with an empty payload. - -1.4. Bob's OP advertises his service descriptor(s). - - Bob's OP opens a stream to each directory server's directory port via Tor. - (He may re-use old circuits for this.) Over this stream, Bob's OP makes - an HTTP 'POST' request, to a URL "/tor/rendezvous/publish" relative to the - directory server's root, containing as its body Bob's service descriptor. - - Bob should upload a service descriptor for each version format that - is supported in the current Tor network. - - Upon receiving a descriptor, the directory server checks the signature, - and discards the descriptor if the signature does not match the enclosed - public key. Next, the directory server checks the timestamp. If the - timestamp is more than 24 hours in the past or more than 1 hour in the - future, or the directory server already has a newer descriptor with the - same public key, the server discards the descriptor. Otherwise, the - server discards any older descriptors with the same public key and - version format, and associates the new descriptor with the public key. - The directory server remembers this descriptor for at least 24 hours - after its timestamp. At least every 18 hours, Bob's OP uploads a - fresh descriptor. - -1.5. Alice receives a x.y.z.onion address. - - When Alice receives a pointer to a location-hidden service, it is as a - hostname of the form "z.onion" or "y.z.onion" or "x.y.z.onion", where - z is a base-32 encoding of a 10-octet hash of Bob's service's public - key, computed as follows: - - 1. Let H = H(PK). - 2. Let H' = the first 80 bits of H, considering each octet from - most significant bit to least significant bit. - 2. Generate a 16-character encoding of H', using base32 as defined - in RFC 3548. - - (We only use 80 bits instead of the 160 bits from SHA1 because we - don't need to worry about arbitrary collisions, and because it will - make handling the url's more convenient.) - - The string "x", if present, is the base-32 encoding of the - authentication/authorization required by the introduction point. - The string "y", if present, is the base-32 encoding of the - authentication/authorization required by the hidden service. - Omitting a string is taken to mean auth type [00 00]. - See section 2 of this document for details on auth mechanisms. - - [Yes, numbers are allowed at the beginning. See RFC 1123. -NM] - -1.6. Alice's OP retrieves a service descriptor. - - Alice opens a stream to a directory server via Tor, and makes an HTTP GET - request for the document '/tor/rendezvous/<z>' or '/tor/rendezvous1/<z>', - where '<z>' is replaced with the encoding of Bob's public key as described - above. (She may re-use old circuits for this.) The directory replies with - a 404 HTTP response if it does not recognize <z>, and otherwise returns - Bob's most recently uploaded service descriptor. (If Alice requests - 'rendezvous1', the directory server provides a V1 descriptor or a V0 - descriptor if no V1 descriptor is available. If Alice requests - 'rendezvous', the directory server returns a V0 descriptor.) - - If Alice's OP receives a 404 response, it tries the other directory - servers, and only fails the lookup if none recognize the public key hash. - - Upon receiving a service descriptor, Alice verifies with the same process - as the directory server uses, described above in section 1.4. - - The directory server gives a 400 response if it cannot understand Alice's - request. - - Alice should cache the descriptor locally, but should not use - descriptors that are more than 24 hours older than their timestamp. - [Caching may make her partitionable, but she fetched it anonymously, - and we can't very well *not* cache it. -RD] - -1.7. Alice's OP establishes a rendezvous point. - - When Alice requests a connection to a given location-hidden service, - and Alice's OP does not have an established circuit to that service, - the OP builds a rendezvous circuit. It does this by establishing - a circuit to a randomly chosen OR, and sending a - RELAY_ESTABLISH_RENDEZVOUS cell to that OR. The body of that cell - contains: - - RC Rendezvous cookie [20 octets] - - [XXX011 this looks like an auth mechanism. should we generalize here? -RD] - - The rendezvous cookie is an arbitrary 20-byte value, chosen randomly by - Alice's OP. - - Upon receiving a RELAY_ESTABLISH_RENDEZVOUS cell, the OR associates the - RC with the circuit that sent it. It replies to Alice with an empty - RELAY_RENDEZVOUS_ESTABLISHED cell to indicate success. - - Alice's OP MUST NOT use the circuit which sent the cell for any purpose - other than rendezvous with the given location-hidden service. - -1.8. Introduction: from Alice's OP to Introduction Point - - Alice builds a separate circuit to one of Bob's chosen introduction - points, and sends it a RELAY_INTRODUCE1 cell containing: - - Cleartext - PK_ID Identifier for Bob's PK [20 octets] -[XXX011 want to put intro-level auth info here, but no version. crap. -RD] - - Encrypted to Bob's PK: - RP Rendezvous point's nickname [20 octets] - RC Rendezvous cookie [20 octets] - g^x Diffie-Hellman data, part 1 [128 octets] - OR - VER Version byte: set to 1. [1 octet] - RP Rendezvous point nick or ID [42 octets] - RC Rendezvous cookie [20 octets] - g^x Diffie-Hellman data, part 1 [128 octets] - OR - VER Version byte: set to 2. [1 octet] - IP Rendezvous point's address [4 octets] - PORT Rendezvous point's OR port [2 octets] - ID Rendezvous point identity ID [20 octets] - KLEN Length of onion key [2 octets] - KEY Rendezvous point onion key [KLEN octets] - RC Rendezvous cookie [20 octets] - g^x Diffie-Hellman data, part 1 [128 octets] - OR - VER Version byte: set to 3. [1 octet] - ATYPE An address type (typically 4) [1 octet] - ADDR Introduction point's IP address [4 or 16 octets] - PORT Rendezvous point's OR port [2 octets] - AUTHT The auth type that is supported [2 octets] - AUTHL Length of auth data [1 octet] - AUTHD Auth data [variable] - ID Rendezvous point identity ID [20 octets] - KLEN Length of onion key [2 octets] - KEY Rendezvous point onion key [KLEN octets] - RC Rendezvous cookie [20 octets] - g^x Diffie-Hellman data, part 1 [128 octets] - - PK_ID is the hash of Bob's public key. RP is NUL-padded and terminated, - and must contain EITHER a nickname, or an identity key digest, encoded in - hex, and prefixed with a '$'. - - Implementations SHOULD accept all variants, and list the variants they - accept in their V1 descriptor. Implementations should only generate the - variants listed in the service's V1 descriptor; if no V1 descriptor is - available, only the first variant should be generated. No version should - generate the second variant (version byte=1). - - The hybrid encryption to Bob's PK works just like the hybrid - encryption in CREATE cells (see main spec). Thus the payload of the - RELAY_INTRODUCE1 cell on the wire will contain 20+42+16+20+20+128=246 - bytes. [XXXX not really] - -1.9. Introduction: From the Introduction Point to Bob's OP - - If the Introduction Point recognizes PK_ID as a public key which has - established a circuit for introductions as in 1.3 above, it sends the body - of the cell in a new RELAY_INTRODUCE2 cell down the corresponding circuit. - (If the PK_ID is unrecognized, the RELAY_INTRODUCE1 cell is discarded.) - - After sending the RELAY_INTRODUCE2 cell, the OR replies to Alice with an - empty RELAY_COMMAND_INTRODUCE_ACK cell. If no RELAY_INTRODUCE2 cell can - be sent, the OR replies to Alice with a non-empty cell to indicate an - error. (The semantics of the cell body may be determined later; the - current implementation sends a single '1' byte on failure.) - - When Bob's OP receives the RELAY_INTRODUCE2 cell, it decrypts it with - the private key for the corresponding hidden service, and extracts the - rendezvous point's nickname, the rendezvous cookie, and the value of g^x - chosen by Alice. - -1.10. Rendezvous - - Bob's OP builds a new Tor circuit ending at Alice's chosen rendezvous - point, and sends a RELAY_RENDEZVOUS1 cell along this circuit, containing: - RC Rendezvous cookie [20 octets] - g^y Diffie-Hellman [128 octets] - KH Handshake digest [20 octets] - - (Bob's OP MUST NOT use this circuit for any other purpose.) - - If the RP recognizes RC, it relays the rest of the cell down the - corresponding circuit in a RELAY_RENDEZVOUS2 cell, containing: - - g^y Diffie-Hellman [128 octets] - KH Handshake digest [20 octets] - - (If the RP does not recognize the RC, it discards the cell and - tears down the circuit.) - - When Alice's OP receives a RELAY_RENDEZVOUS2 cell on a circuit which - has sent a RELAY_ESTABLISH_RENDEZVOUS cell but which has not yet received - a reply, it uses g^y and H(g^xy) to complete the handshake as in the Tor - circuit extend process: they establish a 60-octet string as - K = SHA1(g^xy | [00]) | SHA1(g^xy | [01]) | SHA1(g^xy | [02]) - and generate - KH = K[0..15] - Kf = K[16..31] - Kb = K[32..47] - - Subsequently, the rendezvous point passes relay cells, unchanged, from - each of the two circuits to the other. When Alice's OP sends - RELAY cells along the circuit, it first encrypts them with the - Kf, then with all of the keys for the ORs in Alice's side of the circuit; - and when Alice's OP receives RELAY cells from the circuit, it decrypts - them with the keys for the ORs in Alice's side of the circuit, then - decrypts them with Kb. Bob's OP does the same, with Kf and Kb - interchanged. - -1.11. Creating streams - - To open TCP connections to Bob's location-hidden service, Alice's OP sends - a RELAY_BEGIN cell along the established circuit, using the special - address "", and a chosen port. Bob's OP chooses a destination IP and - port, based on the configuration of the service connected to the circuit, - and opens a TCP stream. From then on, Bob's OP treats the stream as an - ordinary exit connection. - [ Except he doesn't include addr in the connected cell or the end - cell. -RD] - - Alice MAY send multiple RELAY_BEGIN cells along the circuit, to open - multiple streams to Bob. Alice SHOULD NOT send RELAY_BEGIN cells for any - other address along her circuit to Bob; if she does, Bob MUST reject them. - -2.0. Authentication and authorization. - -Foo. - |