February 2021 - tor-commits - lists.torproject.org

[tor/release-0.3.5] exit: Deny re-entry into the network
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit 93ac6ec4d3d19aaff7fed2ea97b0a30528da3767 Author: Roger Dingledine <arma(a)torproject.org> Date: Wed Jan 27 23:48:57 2021 -0500 exit: Deny re-entry into the network Exit relays now reject exit attempts to known relay addresses + ORPort and also to authorities on the ORPort and DirPort. Closes #2667 Signed-off-by: David Goulet <dgoulet(a)torproject.org> --- changes/ticket2667 | 4 ++++ src/core/or/connection_edge.c | 25 +++++++++++++++++++++++++ 2 files changed, 29 insertions(+) diff --git a/changes/ticket2667 b/changes/ticket2667 new file mode 100644 index 0000000000..cc42286ef9 --- /dev/null +++ b/changes/ticket2667 @@ -0,0 +1,4 @@ + o Major feature (exit): + - Re-entry into the network is now denied at the Exit level to all relays' + ORPort and authorities' ORPort+DirPort. This is to help mitigate a series + of attacks. See ticket for more information. Closes ticket 2667. diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c index 67a772be08..f9a9bbdb73 100644 --- a/src/core/or/connection_edge.c +++ b/src/core/or/connection_edge.c @@ -4035,6 +4035,31 @@ connection_exit_connect(edge_connection_t *edge_conn) return; } + /* Next, check for attempts to connect back into the Tor network. We don't + * want to allow these for the same reason we don't want to allow + * infinite-length circuits (see "A Practical Congestion Attack on Tor Using + * Long Paths", Usenix Security 2009). See also ticket 2667. + * + * The TORPROTOCOL reason is used instead of EXITPOLICY so client do NOT + * attempt to retry connecting onto another circuit that will also fail + * bringing considerable more load on the network if so. + * + * Since the address+port set here is a bloomfilter, in very rare cases, the + * check will create a false positive meaning that the destination could + * actually be legit and thus being denied exit. However, sending back a + * reason that makes the client retry results in much worst consequences in + * case of an attack so this is a small price to pay. */ + if (!connection_edge_is_rendezvous_stream(edge_conn) && + nodelist_reentry_probably_contains(&conn->addr, conn->port)) { + log_info(LD_EXIT, "%s:%d tried to connect back to a known relay address. " + "Closing.", escaped_safe_str_client(conn->address), + conn->port); + connection_edge_end(edge_conn, END_STREAM_REASON_TORPROTOCOL); + circuit_detach_stream(circuit_get_by_edge_conn(edge_conn), edge_conn); + connection_free(conn); + return; + } + #ifdef HAVE_SYS_UN_H if (conn->socket_family != AF_UNIX) { #else

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[tor/release-0.3.5] relay: Follow consensus parameter for network reentry
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit ce3af5dd5948cd9c24fc5b5f70814b38cbca46a9 Author: David Goulet <dgoulet(a)torproject.org> Date: Mon Feb 1 08:56:27 2021 -0500 relay: Follow consensus parameter for network reentry Obey the "allow-network-reentry" consensus parameters in order to decide to allow it or not at the Exit. Closes #40268 Signed-off-by: David Goulet <dgoulet(a)torproject.org> --- src/core/or/connection_edge.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c index f9a9bbdb73..b40fa3e567 100644 --- a/src/core/or/connection_edge.c +++ b/src/core/or/connection_edge.c @@ -4003,6 +4003,15 @@ my_exit_policy_rejects(const tor_addr_t *addr, return 0; } +/** Return true iff the consensus allows network reentry. The default value is + * false if the parameter is not found. */ +static bool +network_reentry_is_allowed(void) +{ + /* Default is false, re-entry is not allowed. */ + return !!networkstatus_get_param(NULL, "allow-network-reentry", 0, 0, 1); +} + /** Connect to conn's specified addr and port. If it worked, conn * has now been added to the connection_array. * @@ -4040,6 +4049,8 @@ connection_exit_connect(edge_connection_t *edge_conn) * infinite-length circuits (see "A Practical Congestion Attack on Tor Using * Long Paths", Usenix Security 2009). See also ticket 2667. * + * Skip this if the network reentry is allowed (known from the consensus). + * * The TORPROTOCOL reason is used instead of EXITPOLICY so client do NOT * attempt to retry connecting onto another circuit that will also fail * bringing considerable more load on the network if so. @@ -4050,6 +4061,7 @@ connection_exit_connect(edge_connection_t *edge_conn) * reason that makes the client retry results in much worst consequences in * case of an attack so this is a small price to pay. */ if (!connection_edge_is_rendezvous_stream(edge_conn) && + !network_reentry_is_allowed() && nodelist_reentry_probably_contains(&conn->addr, conn->port)) { log_info(LD_EXIT, "%s:%d tried to connect back to a known relay address. " "Closing.", escaped_safe_str_client(conn->address),

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[tor/release-0.3.5] Merge branch 'maint-0.3.5' into release-0.3.5
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit a5b4ee2a01128a97e5b9ec8f50b975a5aaf40551 Merge: 16bd8c7247 9eba65bd8b Author: David Goulet <dgoulet(a)torproject.org> Date: Wed Feb 3 08:44:19 2021 -0500 Merge branch 'maint-0.3.5' into release-0.3.5 changes/ticket2667 | 4 ++ src/core/or/address_set.c | 74 +++++++++++++++++++++++++++++++++++ src/core/or/address_set.h | 20 +++++++++- src/core/or/connection_edge.c | 25 ++++++++++++ src/feature/nodelist/dirlist.c | 36 +++++++++++++++++ src/feature/nodelist/dirlist.h | 2 + src/feature/nodelist/nodelist.c | 87 +++++++++++++++++++++++++++++++++++------ src/feature/nodelist/nodelist.h | 4 ++ src/test/test_address_set.c | 87 +++++++++++++++++++++++++++++++++++++++++ 9 files changed, 325 insertions(+), 14 deletions(-)

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[tor/release-0.3.5] relay: Double the size of the relay reentry set
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit 98590621bb49cbecd601085f7e03697f8783ff7b Author: David Goulet <dgoulet(a)torproject.org> Date: Mon Feb 1 09:04:50 2021 -0500 relay: Double the size of the relay reentry set This is to minimize false positive and thus deny reentry to Exit connections that were in reality not re-entering. Helps with overall UX. Signed-off-by: David Goulet <dgoulet(a)torproject.org> --- src/feature/nodelist/nodelist.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/src/feature/nodelist/nodelist.c b/src/feature/nodelist/nodelist.c index 9d553ce1f5..22b93762e7 100644 --- a/src/feature/nodelist/nodelist.c +++ b/src/feature/nodelist/nodelist.c @@ -672,8 +672,12 @@ nodelist_set_consensus(networkstatus_t *ns) address_set_free(the_nodelist->node_addrs); addr_port_set_free(the_nodelist->reentry_set); the_nodelist->node_addrs = address_set_new(estimated_addresses); - /* Times two here is for both the ORPort and DirPort. */ - the_nodelist->reentry_set = addr_port_set_new(estimated_addresses * 2); + /* Times two here is for both the ORPort and DirPort. We double it again in + * order to minimize as much as possible the false positive when looking up + * this set. Reason is that Exit streams that are legitimate but end up a + * false positive against this set will thus be considered reentry and be + * rejected which means a bad UX. */ + the_nodelist->reentry_set = addr_port_set_new(estimated_addresses * 2 * 2); SMARTLIST_FOREACH_BEGIN(ns->routerstatus_list, routerstatus_t *, rs) { node_t *node = node_get_or_create(rs->identity_digest);

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[tor/release-0.3.5] Merge branch 'maint-0.3.5' into release-0.3.5
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit bf80465d86832c6ae2faf582d5ada18371b51370 Merge: a5b4ee2a01 98590621bb Author: David Goulet <dgoulet(a)torproject.org> Date: Wed Feb 3 08:51:36 2021 -0500 Merge branch 'maint-0.3.5' into release-0.3.5 src/core/or/connection_edge.c | 12 ++++++++++++ src/feature/nodelist/nodelist.c | 8 ++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)

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[tor/release-0.3.5] relay: Send back CONNECTION_REFUSED on reentry
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit 59f1a41a7fdc03f5008e859e7e56e9c159b8a8d9 Author: David Goulet <dgoulet(a)torproject.org> Date: Mon Feb 1 12:45:32 2021 -0500 relay: Send back CONNECTION_REFUSED on reentry The TORPROTOCOL reason causes the client to close the circuit which is not what we want because other valid streams might be on it. Instead, CONNECTION_REFUSED will leave it open but will not allow more streams to be attached to it. The client then open a new circuit to the destination. Closes #40270 Signed-off-by: David Goulet <dgoulet(a)torproject.org> --- src/core/or/connection_edge.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c index b40fa3e567..895e73ac1b 100644 --- a/src/core/or/connection_edge.c +++ b/src/core/or/connection_edge.c @@ -4066,7 +4066,7 @@ connection_exit_connect(edge_connection_t *edge_conn) log_info(LD_EXIT, "%s:%d tried to connect back to a known relay address. " "Closing.", escaped_safe_str_client(conn->address), conn->port); - connection_edge_end(edge_conn, END_STREAM_REASON_TORPROTOCOL); + connection_edge_end(edge_conn, END_STREAM_REASON_CONNECTREFUSED); circuit_detach_stream(circuit_get_by_edge_conn(edge_conn), edge_conn); connection_free(conn); return;

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[tor/release-0.3.5] Merge branch 'maint-0.3.5' into release-0.3.5
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit c3741d754eed8848b3009f728cb8d33d75c86549 Merge: 4dfada509a a3cef41fc3 Author: David Goulet <dgoulet(a)torproject.org> Date: Wed Feb 3 08:56:38 2021 -0500 Merge branch 'maint-0.3.5' into release-0.3.5 src/core/or/connection_edge.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

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[tor/release-0.3.5] node: Move reentry set to use a digestmap_t
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit c2cee6c780a1329a6906e91dc6f7854635727691 Author: David Goulet <dgoulet(a)torproject.org> Date: Mon Feb 1 12:20:39 2021 -0500 node: Move reentry set to use a digestmap_t Any lookup now will be certain and not probabilistic as the bloomfilter. Closes #40269 Signed-off-by: David Goulet <dgoulet(a)torproject.org> --- src/core/or/connection_edge.c | 2 +- src/feature/nodelist/nodelist.c | 63 ++++++++++++++++++++++++++++++++--------- src/feature/nodelist/nodelist.h | 3 +- src/test/test_address_set.c | 12 ++++---- 4 files changed, 57 insertions(+), 23 deletions(-) diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c index b40fa3e567..4727a0ad66 100644 --- a/src/core/or/connection_edge.c +++ b/src/core/or/connection_edge.c @@ -4062,7 +4062,7 @@ connection_exit_connect(edge_connection_t *edge_conn) * case of an attack so this is a small price to pay. */ if (!connection_edge_is_rendezvous_stream(edge_conn) && !network_reentry_is_allowed() && - nodelist_reentry_probably_contains(&conn->addr, conn->port)) { + nodelist_reentry_contains(&conn->addr, conn->port)) { log_info(LD_EXIT, "%s:%d tried to connect back to a known relay address. " "Closing.", escaped_safe_str_client(conn->address), conn->port); diff --git a/src/feature/nodelist/nodelist.c b/src/feature/nodelist/nodelist.c index 22b93762e7..9d56f2c3aa 100644 --- a/src/feature/nodelist/nodelist.c +++ b/src/feature/nodelist/nodelist.c @@ -136,7 +136,7 @@ typedef struct nodelist_t { /* Set of addresses + port that belong to nodes we know and that we don't * allow network re-entry towards them. */ - addr_port_set_t *reentry_set; + digestmap_t *reentry_set; /* The valid-after time of the last live consensus that initialized the * nodelist. We use this to detect outdated nodelists that need to be @@ -488,6 +488,42 @@ node_add_to_address_set(const node_t *node) } } +/** Build a construction for the reentry set consisting of an address and port + * pair. + * + * If the given address is _not_ AF_INET or AF_INET6, then the item is an + * array of 0s. + * + * Return a pointer to a static buffer containing the item. Next call to this + * function invalidates its previous content. */ +static char * +build_addr_port_item(const tor_addr_t *addr, const uint16_t port) +{ + /* At most 16 bytes are put in this (IPv6) and then 2 bytes for the port + * which is within the maximum of 20 bytes (DIGEST_LEN). */ + static char data[DIGEST_LEN]; + + memset(data, 0, sizeof(data)); + switch (tor_addr_family(addr)) { + case AF_INET: + memcpy(data, &addr->addr.in_addr.s_addr, 4); + break; + case AF_INET6: + memcpy(data, &addr->addr.in6_addr.s6_addr, 16); + break; + case AF_UNSPEC: + /* Leave the 0. */ + break; + default: + /* LCOV_EXCL_START */ + tor_fragile_assert(); + /* LCOV_EXCL_STOP */ + } + + memcpy(data + 16, &port, sizeof(port)); + return data; +} + /** Add the given address into the nodelist address set. */ void nodelist_add_addr_to_address_set(const tor_addr_t *addr, @@ -501,10 +537,12 @@ nodelist_add_addr_to_address_set(const tor_addr_t *addr, } address_set_add(the_nodelist->node_addrs, addr); if (or_port != 0) { - addr_port_set_add(the_nodelist->reentry_set, addr, or_port); + digestmap_set(the_nodelist->reentry_set, + build_addr_port_item(addr, or_port), (void*) 1); } if (dir_port != 0) { - addr_port_set_add(the_nodelist->reentry_set, addr, dir_port); + digestmap_set(the_nodelist->reentry_set, + build_addr_port_item(addr, dir_port), (void*) 1); } } @@ -525,7 +563,7 @@ nodelist_probably_contains_address(const tor_addr_t *addr) /** Return true if <b>addr</b> is the address of some node in the nodelist and * corresponds also to the given port. If not, probably return false. */ bool -nodelist_reentry_probably_contains(const tor_addr_t *addr, uint16_t port) +nodelist_reentry_contains(const tor_addr_t *addr, uint16_t port) { if (BUG(!addr) || BUG(!port)) return false; @@ -533,8 +571,8 @@ nodelist_reentry_probably_contains(const tor_addr_t *addr, uint16_t port) if (!the_nodelist || !the_nodelist->reentry_set) return false; - return addr_port_set_probably_contains(the_nodelist->reentry_set, - addr, port); + return digestmap_get(the_nodelist->reentry_set, + build_addr_port_item(addr, port)) != NULL; } /** Add <b>ri</b> to an appropriate node in the nodelist. If we replace an @@ -669,15 +707,12 @@ nodelist_set_consensus(networkstatus_t *ns) get_estimated_address_per_node(); estimated_addresses += (get_n_authorities(V3_DIRINFO | BRIDGE_DIRINFO) * get_estimated_address_per_node()); + /* Clear our sets because we will repopulate them with what this new + * consensus contains. */ address_set_free(the_nodelist->node_addrs); - addr_port_set_free(the_nodelist->reentry_set); the_nodelist->node_addrs = address_set_new(estimated_addresses); - /* Times two here is for both the ORPort and DirPort. We double it again in - * order to minimize as much as possible the false positive when looking up - * this set. Reason is that Exit streams that are legitimate but end up a - * false positive against this set will thus be considered reentry and be - * rejected which means a bad UX. */ - the_nodelist->reentry_set = addr_port_set_new(estimated_addresses * 2 * 2); + digestmap_free(the_nodelist->reentry_set, NULL); + the_nodelist->reentry_set = digestmap_new(); SMARTLIST_FOREACH_BEGIN(ns->routerstatus_list, routerstatus_t *, rs) { node_t *node = node_get_or_create(rs->identity_digest); @@ -904,7 +939,7 @@ nodelist_free_all(void) address_set_free(the_nodelist->node_addrs); the_nodelist->node_addrs = NULL; - addr_port_set_free(the_nodelist->reentry_set); + digestmap_free(the_nodelist->reentry_set, NULL); the_nodelist->reentry_set = NULL; tor_free(the_nodelist); diff --git a/src/feature/nodelist/nodelist.h b/src/feature/nodelist/nodelist.h index 4c4ee6fe83..bc09731ce2 100644 --- a/src/feature/nodelist/nodelist.h +++ b/src/feature/nodelist/nodelist.h @@ -35,8 +35,7 @@ node_t *nodelist_add_microdesc(microdesc_t *md); void nodelist_set_consensus(networkstatus_t *ns); void nodelist_ensure_freshness(networkstatus_t *ns); int nodelist_probably_contains_address(const tor_addr_t *addr); -bool nodelist_reentry_probably_contains(const tor_addr_t *addr, - uint16_t port); +bool nodelist_reentry_contains(const tor_addr_t *addr, uint16_t port); void nodelist_add_addr_to_address_set(const tor_addr_t *addr, uint16_t or_port, uint16_t dir_port); diff --git a/src/test/test_address_set.c b/src/test/test_address_set.c index 6d9fab67ab..4e55d71ff4 100644 --- a/src/test/test_address_set.c +++ b/src/test/test_address_set.c @@ -210,8 +210,8 @@ test_exit_no_reentry(void *arg) nodelist_set_consensus(dummy_ns); /* The address set is empty. Try it anyway */ - tt_assert(!nodelist_reentry_probably_contains(&addr_v4, 244)); - tt_assert(!nodelist_reentry_probably_contains(&addr_v6, 244)); + tt_assert(!nodelist_reentry_contains(&addr_v4, 244)); + tt_assert(!nodelist_reentry_contains(&addr_v6, 244)); /* Now let's populate the network */ md = tor_malloc_zero(sizeof(*md)); @@ -238,12 +238,12 @@ test_exit_no_reentry(void *arg) /* First let's try an address that is on the no-reentry list, but with a different port */ - tt_assert(!nodelist_reentry_probably_contains(&addr_v4, 666)); - tt_assert(!nodelist_reentry_probably_contains(&addr_v6, 444)); + tt_assert(!nodelist_reentry_contains(&addr_v4, 666)); + tt_assert(!nodelist_reentry_contains(&addr_v6, 444)); /* OK now let's try with the right address and right port */ - tt_assert(nodelist_reentry_probably_contains(&addr_v4, 444)); - tt_assert(nodelist_reentry_probably_contains(&addr_v6, 666)); + tt_assert(nodelist_reentry_contains(&addr_v4, 444)); + tt_assert(nodelist_reentry_contains(&addr_v6, 666)); done: routerstatus_free(rs); routerinfo_free(ri); microdesc_free(md);

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[tor/release-0.3.5] Merge branch 'ticket40270_035_01' into maint-0.3.5
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit a3cef41fc375b3a004eca3d090be0ebe9801cdb0 Merge: c2cee6c780 59f1a41a7f Author: David Goulet <dgoulet(a)torproject.org> Date: Wed Feb 3 08:56:30 2021 -0500 Merge branch 'ticket40270_035_01' into maint-0.3.5 src/core/or/connection_edge.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

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[tor/release-0.3.5] Merge branch 'maint-0.3.5' into release-0.3.5
by dgoulet＠torproject.org 03 Feb '21

03 Feb '21

commit 4dfada509a1ebf21aecc35af28308cd8675f31e8 Merge: bf80465d86 c2cee6c780 Author: David Goulet <dgoulet(a)torproject.org> Date: Wed Feb 3 08:54:40 2021 -0500 Merge branch 'maint-0.3.5' into release-0.3.5 src/core/or/connection_edge.c | 2 +- src/feature/nodelist/nodelist.c | 63 ++++++++++++++++++++++++++++++++--------- src/feature/nodelist/nodelist.h | 3 +- src/test/test_address_set.c | 12 ++++---- 4 files changed, 57 insertions(+), 23 deletions(-)

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