Unverified Commit 10aa913a authored by teor (Tim Wilson-Brown)'s avatar teor (Tim Wilson-Brown) Committed by teor
Browse files

Client & HS ignore UseNTorHandshake, all non-HS handshakes use ntor

Rely on onion_populate_cpath to check that we're only using
TAP for the rare hidden service cases.

Check and log if handshakes only support TAP when they should support
ntor.
parent cad90466
o Major bug fixes (circuit building):
- Tor authorities, relays, and clients no longer support
circuit-building using TAP. (The hidden service protocol
still uses TAP.)
- Relays make sure their own descriptor has an ntor key.
- Authorites no longer trust the version a relay claims (if any),
instead, they check specifically for an ntor key.
- Tor authorities, relays, and clients only use ntor, except for
rare cases in the hidden service protocol.
- Authorities, relays and clients specifically check that each
descriptor has an ntor key.
- Clients avoid downloading a descriptor if the relay version is
too old to support ntor.
- Client code ignores nodes without ntor keys: they will not be
selected during circuit-building, or as guards, or as directory
- Client code never chooses nodes without ntor keys: they will not
be selected during circuit-building, or as guards, or as directory
mirrors, or as introduction or rendezvous points.
- Circuit-building code assumes that all hops can use ntor,
except for rare hidden service protocol cases.
- Hidden service client to intro point and service to rendezvous point
connections use the TAP key supplied by the protocol.
Fixes bug 19163; bugfix on 0.2.4.18-rc.
......@@ -1468,16 +1468,6 @@ The following options are useful only for clients (that is, if
"auto" (recommended) then it is on for all clients that do not set
FetchUselessDescriptors. (Default: auto)
[[UseNTorHandshake]] **UseNTorHandshake** **0**|**1**|**auto**::
The "ntor" circuit-creation handshake is faster and (we think) more
secure than the original ("TAP") circuit handshake, but starting to use
it too early might make your client stand out. If this option is 0, your
Tor client won't use the ntor handshake. If it's 1, your Tor client
will use the ntor handshake to extend circuits through servers that
support it. If this option is "auto", then your client
will use the ntor handshake once enough directory authorities recommend
it. (Default: 1)
[[PathBiasCircThreshold]] **PathBiasCircThreshold** __NUM__ +
[[PathBiasNoticeRate]] **PathBiasNoticeRate** __NUM__ +
......
......@@ -58,7 +58,6 @@ static crypt_path_t *onion_next_hop_in_cpath(crypt_path_t *cpath);
static int onion_extend_cpath(origin_circuit_t *circ);
static int count_acceptable_nodes(smartlist_t *routers);
static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);
static int circuits_can_use_ntor(void);
/** This function tries to get a channel to the specified endpoint,
* and then calls command_setup_channel() to give it the right
......@@ -780,10 +779,13 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ)
tor_assert(circ->cpath);
tor_assert(circ->cpath->extend_info);
if (!circ->cpath->extend_info->onion_key)
return 1; /* our hand is forced: only a create_fast will work. */
if (!circuit_has_usable_onion_key(circ)) {
/* We don't have ntor, and we don't have or can't use TAP,
* so our hand is forced: only a create_fast will work. */
return 1;
}
if (public_server_mode(options)) {
/* We're a server, and we know an onion key. We can choose.
/* We're a server, and we have a usable onion key. We can choose.
* Prefer to blend our circuit into the other circuits we are
* creating on behalf of others. */
return 0;
......@@ -808,28 +810,20 @@ circuit_timeout_want_to_count_circ(origin_circuit_t *circ)
&& circ->build_state->desired_path_len == DEFAULT_ROUTE_LEN;
}
/** Return true if the ntor handshake is enabled in the configuration, or if
* it's been set to "auto" in the configuration and it's enabled in the
* consensus. */
static int
circuits_can_use_ntor(void)
{
const or_options_t *options = get_options();
if (options->UseNTorHandshake != -1)
return options->UseNTorHandshake;
return networkstatus_get_param(NULL, "UseNTorHandshake", 0, 0, 1);
}
/** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b>
* directly, and set *<b>cell_type_out</b> and *<b>handshake_type_out</b>
* accordingly. */
* accordingly.
* Note that TAP handshakes are only used for direct connections:
* - from Tor2web to intro points not in the client's consensus, and
* - from Single Onions to rend points not in the service's consensus.
* This is checked in onion_populate_cpath. */
static void
circuit_pick_create_handshake(uint8_t *cell_type_out,
uint16_t *handshake_type_out,
const extend_info_t *ei)
{
/* XXXX029 Remove support for deciding to use TAP. */
if (extend_info_supports_ntor(ei) && circuits_can_use_ntor()) {
/* XXXX030 Remove support for deciding to use TAP. */
if (extend_info_supports_ntor(ei)) {
*cell_type_out = CELL_CREATE2;
*handshake_type_out = ONION_HANDSHAKE_TYPE_NTOR;
return;
......@@ -841,9 +835,13 @@ circuit_pick_create_handshake(uint8_t *cell_type_out,
/** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b>
* directly, and set *<b>handshake_type_out</b> accordingly. Decide whether,
* in extending through <b>node_prev</b> to do so, we should use an EXTEND2 or
* an EXTEND cell to do so, and set *<b>cell_type_out</b> and
* *<b>create_cell_type_out</b> accordingly. */
* in extending through <b>node</b> to do so, we should use an EXTEND2 or an
* EXTEND cell to do so, and set *<b>cell_type_out</b> and
* *<b>create_cell_type_out</b> accordingly.
* Note that TAP handshakes are only used for extend handshakes:
* - from clients to intro points, and
* - from hidden services to rend points.
* This is checked in onion_populate_cpath. */
static void
circuit_pick_extend_handshake(uint8_t *cell_type_out,
uint8_t *create_cell_type_out,
......@@ -854,18 +852,27 @@ circuit_pick_extend_handshake(uint8_t *cell_type_out,
uint8_t t;
circuit_pick_create_handshake(&t, handshake_type_out, ei);
/* XXXX029 Remove support for deciding to use TAP. */
/* XXXX030 Remove support for deciding to use TAP. */
/* It is an error to extend if there is no previous node. */
tor_assert_nonfatal(node_prev);
/* It is an error for a node with a known version to be so old it does not
* support ntor. */
tor_assert_nonfatal(routerstatus_version_supports_ntor(node_prev->rs, 1));
/* Assume relays without tor versions or routerstatuses support ntor.
* The authorities enforce ntor support, and assuming and failing is better
* than allowing a malicious node to perform a protocol downgrade to TAP. */
if (node_prev &&
*handshake_type_out != ONION_HANDSHAKE_TYPE_TAP &&
(node_has_curve25519_onion_key(node_prev) ||
(node_prev->rs &&
routerstatus_version_supports_ntor(node_prev->rs, 0)))) {
*cell_type_out = RELAY_COMMAND_EXTEND2;
*create_cell_type_out = CELL_CREATE2;
} else {
*cell_type_out = RELAY_COMMAND_EXTEND;
*create_cell_type_out = CELL_CREATE;
}
(routerstatus_version_supports_ntor(node_prev->rs, 1)))) {
*cell_type_out = RELAY_COMMAND_EXTEND2;
*create_cell_type_out = CELL_CREATE2;
} else {
*cell_type_out = RELAY_COMMAND_EXTEND;
*create_cell_type_out = CELL_CREATE;
}
}
/** This is the backbone function for building circuits.
......@@ -2468,6 +2475,15 @@ extend_info_addr_is_allowed(const tor_addr_t *addr)
return 0;
}
/* Does ei have a valid TAP key? */
int
extend_info_supports_tap(const extend_info_t* ei)
{
tor_assert(ei);
/* Valid TAP keys are not NULL */
return ei->onion_key != NULL;
}
/* Does ei have a valid ntor key? */
int
extend_info_supports_ntor(const extend_info_t* ei)
......@@ -2478,3 +2494,46 @@ extend_info_supports_ntor(const extend_info_t* ei)
(const char*)ei->curve25519_onion_key.public_key,
CURVE25519_PUBKEY_LEN);
}
/* Is circuit purpose allowed to use the deprecated TAP encryption protocol?
* The hidden service protocol still uses TAP for some connections, because
* ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
static int
circuit_purpose_can_use_tap_impl(uint8_t purpose)
{
return (purpose == CIRCUIT_PURPOSE_S_CONNECT_REND ||
purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
}
/* Is circ allowed to use the deprecated TAP encryption protocol?
* The hidden service protocol still uses TAP for some connections, because
* ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
int
circuit_can_use_tap(const origin_circuit_t *circ)
{
tor_assert(circ);
tor_assert(circ->cpath);
tor_assert(circ->cpath->extend_info);
return (circuit_purpose_can_use_tap_impl(circ->base_.purpose) &&
extend_info_supports_tap(circ->cpath->extend_info));
}
/* Does circ have an onion key which it's allowed to use? */
int
circuit_has_usable_onion_key(const origin_circuit_t *circ)
{
tor_assert(circ);
tor_assert(circ->cpath);
tor_assert(circ->cpath->extend_info);
return (extend_info_supports_ntor(circ->cpath->extend_info) ||
circuit_can_use_tap(circ));
}
/* Does ei have an onion key which it would prefer to use?
* Currently, we prefer ntor keys*/
int
extend_info_has_preferred_onion_key(const extend_info_t* ei)
{
tor_assert(ei);
return extend_info_supports_ntor(ei);
}
......@@ -54,7 +54,11 @@ extend_info_t *extend_info_from_node(const node_t *r, int for_direct_connect);
extend_info_t *extend_info_dup(extend_info_t *info);
void extend_info_free(extend_info_t *info);
int extend_info_addr_is_allowed(const tor_addr_t *addr);
int extend_info_supports_tap(const extend_info_t* ei);
int extend_info_supports_ntor(const extend_info_t* ei);
int circuit_can_use_tap(const origin_circuit_t *circ);
int circuit_has_usable_onion_key(const origin_circuit_t *circ);
int extend_info_has_preferred_onion_key(const extend_info_t* ei);
const node_t *build_state_get_exit_node(cpath_build_state_t *state);
const char *build_state_get_exit_nickname(cpath_build_state_t *state);
......
......@@ -438,7 +438,7 @@ static config_var_t option_vars_[] = {
V(UseEntryGuardsAsDirGuards, BOOL, "1"),
V(UseGuardFraction, AUTOBOOL, "auto"),
V(UseMicrodescriptors, AUTOBOOL, "auto"),
V(UseNTorHandshake, AUTOBOOL, "1"),
OBSOLETE("UseNTorHandshake"),
V(User, STRING, NULL),
V(UserspaceIOCPBuffers, BOOL, "0"),
V(AuthDirSharedRandomness, BOOL, "1"),
......
......@@ -1196,6 +1196,9 @@ microdesc_has_curve25519_onion_key(const microdesc_t *md)
int
node_has_curve25519_onion_key(const node_t *node)
{
if (!node)
return 0;
if (node->ri)
return routerinfo_has_curve25519_onion_key(node->ri);
else if (node->md)
......
......@@ -4456,9 +4456,6 @@ typedef struct {
char *TLSECGroup; /**< One of "P256", "P224", or nil for auto */
/** Autobool: should we use the ntor handshake if we can? */
int UseNTorHandshake;
/** Fraction: */
double PathsNeededToBuildCircuits;
......
......@@ -1351,8 +1351,13 @@ rend_client_get_random_intro_impl(const rend_cache_entry_t *entry,
i = crypto_rand_int(smartlist_len(usable_nodes));
intro = smartlist_get(usable_nodes, i);
if (BUG(!intro->extend_info)) {
/* This should never happen, but it isn't fatal, just try another */
smartlist_del(usable_nodes, i);
goto again;
}
/* Do we need to look up the router or is the extend info complete? */
if (!intro->extend_info->onion_key) {
if (!extend_info_supports_tap(intro->extend_info)) {
const node_t *node;
extend_info_t *new_extend_info;
if (tor_digest_is_zero(intro->extend_info->identity_digest))
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment