From e001610c99bea661dbefc693ec173a90fcb3ee5e Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Thu, 31 Oct 2013 16:44:14 -0400 Subject: [PATCH 1/3] Implement proposal 221: Stop sending CREATE_FAST This makes FastFirstHopPK an AUTOBOOL; makes the default "auto"; and makes the behavior of "auto" be "look at the consensus." --- changes/prop221 | 6 ++++++ doc/tor.1.txt | 8 +++++--- src/or/circuitbuild.c | 8 +++++--- src/or/config.c | 2 +- 4 files changed, 17 insertions(+), 7 deletions(-) create mode 100644 changes/prop221 diff --git a/changes/prop221 b/changes/prop221 new file mode 100644 index 0000000000..b2bf44bc37 --- /dev/null +++ b/changes/prop221 @@ -0,0 +1,6 @@ + o Minor features: + - Stop sending the CREATE_FAST cells by default; instead, use a + parameter in the consensus to decide whether to use + CREATE_FAST. This can improve security on connections where + Tor's circuit handshake is stronger than the available TLS + connection security levels. Implements proposal 221. diff --git a/doc/tor.1.txt b/doc/tor.1.txt index 779db61c29..4f3612b102 100644 --- a/doc/tor.1.txt +++ b/doc/tor.1.txt @@ -1119,15 +1119,17 @@ The following options are useful only for clients (that is, if the node "foo". Disabled by default since attacking websites and exit relays can use it to manipulate your path selection. (Default: 0) -[[FastFirstHopPK]] **FastFirstHopPK** **0**|**1**:: +[[FastFirstHopPK]] **FastFirstHopPK** **0**|**1**|**auto**:: When this option is disabled, Tor uses the public key step for the first hop of creating circuits. Skipping it is generally safe since we have already used TLS to authenticate the relay and to establish forward-secure - keys. Turning this option off makes circuit building slower. + + keys. Turning this option off makes circuit building a little + slower. Setting this option to "auto" takes advice from the authorities + in the latest consensus about whether to use this feature. + + Note that Tor will always use the public key step for the first hop if it's operating as a relay, and it will never use the public key step if it - doesn't yet know the onion key of the first hop. (Default: 1) + doesn't yet know the onion key of the first hop. (Default: auto) [[TransPort]] **TransPort** \['address':]__port__|**auto** [_isolation flags_]:: Open this port to listen for transparent proxy connections. Set this to diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c index 2b4d3c3118..4603de071f 100644 --- a/src/or/circuitbuild.c +++ b/src/or/circuitbuild.c @@ -663,16 +663,18 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ) if (!circ->cpath->extend_info->onion_key) return 1; /* our hand is forced: only a create_fast will work. */ - if (!options->FastFirstHopPK) - return 0; /* we prefer to avoid create_fast */ if (public_server_mode(options)) { /* We're a server, and we know an onion key. We can choose. * Prefer to blend our circuit into the other circuits we are * creating on behalf of others. */ return 0; } + if (options->FastFirstHopPK == -1) { + /* option is "auto", so look at the consensus. */ + return networkstatus_get_param(NULL, "usecreatefast", 1, 0, 1); + } - return 1; + return options->FastFirstHopPK; } /** Return true if circ is the type of circuit we want to count diff --git a/src/or/config.c b/src/or/config.c index a2811ebc21..1de91878b7 100644 --- a/src/or/config.c +++ b/src/or/config.c @@ -236,7 +236,7 @@ static config_var_t option_vars_[] = { OBSOLETE("FallbackNetworkstatusFile"), V(FascistFirewall, BOOL, "0"), V(FirewallPorts, CSV, ""), - V(FastFirstHopPK, BOOL, "1"), + V(FastFirstHopPK, AUTOBOOL, "auto"), V(FetchDirInfoEarly, BOOL, "0"), V(FetchDirInfoExtraEarly, BOOL, "0"), V(FetchServerDescriptors, BOOL, "1"), From d5558f00729992a9abeeb1cb1512004de35ec007 Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Thu, 31 Oct 2013 16:53:31 -0400 Subject: [PATCH 2/3] circuit_build_failed: distinguish "first hop chan failed", "CREATE failed" Roger spotted this on tor-dev in his comments on proposal 221. (Actually, detect DESTROY vs everything else, since arma likes network timeout indicating failure but not overload indicating failure.) --- src/or/circuituse.c | 9 +++++---- src/or/command.c | 1 + src/or/or.h | 3 +++ 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/src/or/circuituse.c b/src/or/circuituse.c index c2d2b2e87c..06a51a04a2 100644 --- a/src/or/circuituse.c +++ b/src/or/circuituse.c @@ -1382,10 +1382,11 @@ circuit_build_failed(origin_circuit_t *circ) failed_at_last_hop = 1; } if (circ->cpath && - circ->cpath->state != CPATH_STATE_OPEN) { - /* We failed at the first hop. If there's an OR connection - * to blame, blame it. Also, avoid this relay for a while, and - * fail any one-hop directory fetches destined for it. */ + circ->cpath->state != CPATH_STATE_OPEN && + ! circ->base_.received_destroy) { + /* We failed at the first hop for some reason other than a DESTROY cell. + * If there's an OR connection to blame, blame it. Also, avoid this relay + * for a while, and fail any one-hop directory fetches destined for it. */ const char *n_chan_id = circ->cpath->extend_info->identity_digest; int already_marked = 0; if (circ->base_.n_chan) { diff --git a/src/or/command.c b/src/or/command.c index 699b02fb47..51d07b0485 100644 --- a/src/or/command.c +++ b/src/or/command.c @@ -499,6 +499,7 @@ command_process_destroy_cell(cell_t *cell, channel_t *chan) log_debug(LD_OR,"Received for circID %u.",(unsigned)cell->circ_id); reason = (uint8_t)cell->payload[0]; + circ->received_destroy = 1; if (!CIRCUIT_IS_ORIGIN(circ) && cell->circ_id == TO_OR_CIRCUIT(circ)->p_circ_id) { diff --git a/src/or/or.h b/src/or/or.h index 3eaf3447dc..34f055cf06 100644 --- a/src/or/or.h +++ b/src/or/or.h @@ -2785,6 +2785,9 @@ typedef struct circuit_t { * allowing n_streams to add any more cells. (OR circuit only.) */ unsigned int streams_blocked_on_p_chan : 1; + /** True iff this circuit has received a DESTROY cell in either direction */ + unsigned int received_destroy : 1; + uint8_t state; /**< Current status of this circuit. */ uint8_t purpose; /**< Why are we creating this circuit? */ From 2126feaabc3e07dc8f7ad712256de496fbcfb976 Mon Sep 17 00:00:00 2001 From: Roger Dingledine Date: Fri, 25 Jul 2014 12:22:05 -0400 Subject: [PATCH 3/3] get rid of already-merged prop221 changes file --- changes/prop221 | 6 ------ 1 file changed, 6 deletions(-) delete mode 100644 changes/prop221 diff --git a/changes/prop221 b/changes/prop221 deleted file mode 100644 index b2bf44bc37..0000000000 --- a/changes/prop221 +++ /dev/null @@ -1,6 +0,0 @@ - o Minor features: - - Stop sending the CREATE_FAST cells by default; instead, use a - parameter in the consensus to decide whether to use - CREATE_FAST. This can improve security on connections where - Tor's circuit handshake is stronger than the available TLS - connection security levels. Implements proposal 221.