commit 7ec9a68477d3c5b6937fa39445dc6b95415abb39 Author: George Kadianakis desnacked@riseup.net Date: Mon Jul 12 11:23:00 2021 +0300

Service intro circuits are now 4-hop to avoid linkability by intro

Now the circuits look like this:

client rend: C -> G -> L2 -> Rend client intro: C -> G -> L2 -> M -> Intro client hsdir: C -> G -> L2 -> M -> HSDir service rend: C -> G -> L2 -> M -> Rend service intro: C -> G -> L2 -> M -> Intro service hsdir: C -> G -> L2 -> M -> HSDir --- src/core/or/circuitbuild.c | 11 ++++++----- src/test/test_circuitbuild.c | 2 +- 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/core/or/circuitbuild.c b/src/core/or/circuitbuild.c index 5cb647bd02..84a8bec421 100644 --- a/src/core/or/circuitbuild.c +++ b/src/core/or/circuitbuild.c @@ -1394,16 +1394,14 @@ route_len_for_purpose(uint8_t purpose, extend_info_t *exit_ei) return routelen;

switch (purpose) { - /* These two purposes connect to a router that we chose, so - * DEFAULT_ROUTE_LEN is safe. */ - case CIRCUIT_PURPOSE_S_ESTABLISH_INTRO: - /* hidden service connecting to introduction point */ + /* These purposes connect to a router that we chose, so DEFAULT_ROUTE_LEN + * is safe: */ case CIRCUIT_PURPOSE_TESTING: /* router reachability testing */ known_purpose = 1; break;

- /* These three purposes connect to a router that someone else + /* These purposes connect to a router that someone else * might have chosen, so add an extra hop to protect anonymity. */ case CIRCUIT_PURPOSE_C_GENERAL: case CIRCUIT_PURPOSE_C_HSDIR_GET: @@ -1413,6 +1411,9 @@ route_len_for_purpose(uint8_t purpose, extend_info_t *exit_ei) /* client connecting to introduction point */ case CIRCUIT_PURPOSE_S_CONNECT_REND: /* hidden service connecting to rendezvous point */ + case CIRCUIT_PURPOSE_S_ESTABLISH_INTRO: + /* hidden service connecting to intro point. In this case we want an extra + hop to avoid linkability attacks by the introduction point. */ known_purpose = 1; routelen++; break; diff --git a/src/test/test_circuitbuild.c b/src/test/test_circuitbuild.c index 873391a84f..0a5c3530bd 100644 --- a/src/test/test_circuitbuild.c +++ b/src/test/test_circuitbuild.c @@ -113,7 +113,7 @@ test_new_route_len_safe_exit(void *arg) /* hidden service connecting to introduction point */ r = new_route_len(CIRCUIT_PURPOSE_S_ESTABLISH_INTRO, &dummy_ei, &dummy_nodes); - tt_int_op(DEFAULT_ROUTE_LEN, OP_EQ, r); + tt_int_op(DEFAULT_ROUTE_LEN+1, OP_EQ, r);

/* router testing its own reachability */ r = new_route_len(CIRCUIT_PURPOSE_TESTING, &dummy_ei, &dummy_nodes);