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Diffstat (limited to 'spec/tor-spec/creating-circuits.md')
| -rw-r--r-- | spec/tor-spec/creating-circuits.md | 66 |
1 files changed, 31 insertions, 35 deletions
diff --git a/spec/tor-spec/creating-circuits.md b/spec/tor-spec/creating-circuits.md index f2a1c7d..eb8de36 100644 --- a/spec/tor-spec/creating-circuits.md +++ b/spec/tor-spec/creating-circuits.md @@ -5,44 +5,42 @@ When creating a circuit through the network, the circuit creator (OP) performs the following steps: -```text - 1. Choose an onion router as an end node (R_N): - * N MAY be 1 for non-anonymous directory mirror, introduction point, - or service rendezvous connections. - * N SHOULD be 3 or more for anonymous connections. - Some end nodes accept streams (see 6.1), others are introduction - or rendezvous points (see rend-spec-{v2,v3}.txt). +1. Choose an onion router as an end node (R_N): + * N MAY be 1 for non-anonymous directory mirror, introduction point, + or service rendezvous connections. + * N SHOULD be 3 or more for anonymous connections. + Some end nodes accept streams (see ["Relay Cells"](./relay-cells.md#relay-cells)), + others are introduction or rendezvous points (see the [Rendezvous Spec](../rend-spec/index.md)). - 2. Choose a chain of (N-1) onion routers (R_1...R_N-1) to constitute - the path, such that no router appears in the path twice. +2. Choose a chain of (N-1) onion routers (R_1...R_N-1) to constitute + the path, such that no router appears in the path twice. - 3. If not already connected to the first router in the chain, - open a new connection to that router. +3. If not already connected to the first router in the chain, + open a new connection to that router. - 4. Choose a circID not already in use on the connection with the - first router in the chain; send a CREATE/CREATE2 cell along - the connection, to be received by the first onion router. +4. Choose a circID not already in use on the connection with the + first router in the chain; send a CREATE/CREATE2 cell along + the connection, to be received by the first onion router. - 5. Wait until a CREATED/CREATED2 cell is received; finish the - handshake and extract the forward key Kf_1 and the backward - key Kb_1. +5. Wait until a CREATED/CREATED2 cell is received; finish the + handshake and extract the forward key Kf_1 and the backward + key Kb_1. - 6. For each subsequent onion router R (R_2 through R_N), extend - the circuit to R. -``` +6. For each subsequent onion router R (R_2 through R_N), extend + the circuit to R. To extend the circuit by a single onion router R_M, the OP performs these steps: 1. Create an onion skin, encrypted to R_M's public onion key. -```text - 2. Send the onion skin in a relay EXTEND/EXTEND2 cell along - the circuit (see sections 5.1.2 and 5.5). +2. Send the onion skin in a relay EXTEND/EXTEND2 cell along + the circuit (see + ["EXTEND and EXTENDED cells"](./create-created-cells.md#EXTEND) + and ["Routing relay cells"](./routing-relay-cells.md#routing-relay-cells)). - 3. When a relay EXTENDED/EXTENDED2 cell is received, verify KH, - and calculate the shared keys. The circuit is now extended. -``` +3. When a relay EXTENDED/EXTENDED2 cell is received, verify KH, + and calculate the shared keys. The circuit is now extended. When an onion router receives an EXTEND relay cell, it sends a CREATE cell to the next onion router, with the enclosed onion skin as its @@ -52,7 +50,7 @@ When an onion router receives an EXTEND2 relay cell, it sends a CREATE2 cell to the next onion router, with the enclosed HLEN, HTYPE, and HDATA as its payload. The initiating onion router chooses some circID not yet used on the connection between the two onion routers. (But see section -5.1.1 above, concerning choosing circIDs.) +["Choosing circuit IDs in create cells"](./create-created-cells.md#choosing-circid)) As special cases, if the EXTEND/EXTEND2 cell includes a legacy identity, or identity fingerprint of all zeroes, or asks to extend back to the relay @@ -95,12 +93,10 @@ To prevent this, when an OR gets an extend request, it SHOULD use an existing OR connection if the ID matches, and ANY of the following conditions hold: -```text - - The IP matches the requested IP. - - The OR knows that the IP of the connection it's using is canonical - because it was listed in the NETINFO cell. + - The IP matches the requested IP. + - The OR knows that the IP of the connection it's using is canonical + because it was listed in the NETINFO cell. - ORs SHOULD NOT check the IPs that are listed in the server descriptor. - Trusting server IPs makes it easier to covertly impersonate a relay, after - stealing its keys. -``` +ORs SHOULD NOT check the IPs that are listed in the server descriptor. +Trusting server IPs makes it easier to covertly impersonate a relay, after +stealing its keys. |