From 8e8a34eb744157ae4076d9b29e5b4d7bbff19512 Mon Sep 17 00:00:00 2001 From: Karsten Loesing Date: Tue, 17 Aug 2010 10:02:07 +0200 Subject: [PATCH] Add koryk's modifications to rend-spec. --- doc/spec/rend-spec.txt | 55 +++++++++++++++++++++++------------------- 1 file changed, 30 insertions(+), 25 deletions(-) diff --git a/doc/spec/rend-spec.txt b/doc/spec/rend-spec.txt index d440c8a811..fd15e7b665 100644 --- a/doc/spec/rend-spec.txt +++ b/doc/spec/rend-spec.txt @@ -150,7 +150,7 @@ The first time the OP provides an advertised service, it generates a public/private keypair (stored locally). - The OP choses a small number of Tor servers as introduction points. + The OP chooses a small number of Tor servers as introduction points. The OP establishes a new introduction circuit to each introduction point. These circuits MUST NOT be used for anything but hidden service introduction. To establish the introduction, Bob sends a @@ -238,6 +238,9 @@ permanent-id = H(public-key)[:10] + Note: If Bob's OP has "stealth" authorization enabled (see Section 2.2), + it uses the client key in place of the public hidden service key. + "H(time-period | descriptor-cookie | replica)" is the (possibly secret) id part that is necessary to verify that the hidden service is the true originator of this descriptor and that is therefore contained @@ -668,8 +671,8 @@ circuit. (If the PK_ID is unrecognized, the RELAY_COMMAND_INTRODUCE1 cell is discarded.) - After sending the RELAY_COMMAND_INTRODUCE2 cell, the OR replies to Alice - with an empty RELAY_COMMAND_INTRODUCE_ACK cell. If no + After sending the RELAY_COMMAND_INTRODUCE2 cell to Bob, the OR replies to + Alice with an empty RELAY_COMMAND_INTRODUCE_ACK cell. If no RELAY_COMMAND_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 @@ -759,11 +762,11 @@ 2.1. Service with large-scale client authorization The first client authorization protocol aims at performing access control - while consuming as few additional resources as possible. A service - provider should be able to permit access to a large number of clients - while denying access for everyone else. However, the price for - scalability is that the service won't be able to hide its activity from - unauthorized or formerly authorized clients. + while consuming as few additional resources as possible. This is the "basic" + authorization protocol. A service provider should be able to permit access + to a large number of clients while denying access for everyone else. + However, the price for scalability is that the service won't be able to hide + its activity from unauthorized or formerly authorized clients. The main idea of this protocol is to encrypt the introduction-point part in hidden service descriptors to authorized clients using symmetric keys. @@ -822,19 +825,19 @@ 2.2. Authorization for limited number of clients A second, more sophisticated client authorization protocol goes the extra - mile of hiding service activity from unauthorized clients. With all else - being equal to the preceding authorization protocol, the second protocol - publishes hidden service descriptors for each user separately and gets - along with encrypting the introduction-point part of descriptors to a - single client. This allows the service to stop publishing descriptors for - removed clients. As long as a removed client cannot link descriptors - issued for other clients to the service, it cannot derive service - activity any more. The downside of this approach is limited scalability. - Even though the distributed storage of descriptors (cf. proposal 114) - tackles the problem of limited scalability to a certain extent, this - protocol should not be used for services with more than 16 clients. (In - fact, Tor should refuse to advertise services for more than this number - of clients.) + mile of hiding service activity from unauthorized clients. This is the + "stealth" authorization protocol. With all else being equal to the preceding + authorization protocol, the second protocol publishes hidden service + descriptors for each user separately and gets along with encrypting the + introduction-point part of descriptors to a single client. This allows the + service to stop publishing descriptors for removed clients. As long as a + removed client cannot link descriptors issued for other clients to the + service, it cannot derive service activity any more. The downside of this + approach is limited scalability. Even though the distributed storage of + descriptors (cf. proposal 114) tackles the problem of limited scalability to + a certain extent, this protocol should not be used for services with more + than 16 clients. (In fact, Tor should refuse to advertise services for more + than this number of clients.) A hidden service generates an asymmetric "client key" and a symmetric "descriptor cookie" for each client. The client key is used as @@ -882,14 +885,16 @@ A hidden service that is meant to perform client authorization adds a new option HiddenServiceAuthorizeClient to its hidden service configuration. This option contains the authorization type which is - either "1" for the protocol described in 2.1 or "2" for the protocol in - 2.2 and a comma-separated list of human-readable client names, so that - Tor can create authorization data for these clients: + either "basic" for the protocol described in 2.1 or "stealth" for the + protocol in 2.2 and a comma-separated list of human-readable client + names, so that Tor can create authorization data for these clients: HiddenServiceAuthorizeClient auth-type client-name,client-name,... If this option is configured, HiddenServiceVersion is automatically - reconfigured to contain only version numbers of 2 or higher. + reconfigured to contain only version numbers of 2 or higher. There is + a maximum of 512 client names for basic auth and a maximum of 16 for + stealth auth. Tor stores all generated authorization data for the authorization protocols described in Sections 2.1 and 2.2 in a new file using the