Implementat the ntor handshake

The ntor handshake--described in proposal 216 and in a paper by
Goldberg, Stebila, and Ustaoglu--gets us much better performance than
our current approach.
This commit is contained in:
Nick Mathewson 2012-12-03 21:24:21 -05:00
parent 89ec584805
commit cf4dd5fbcb
5 changed files with 503 additions and 7 deletions

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@ -15,6 +15,12 @@ else
evdns_source=src/ext/eventdns.c
endif
if CURVE25519_ENABLED
onion_ntor_source=src/or/onion_ntor.c
else
onion_ntor_source=
endif
src_or_libtor_a_SOURCES = \
src/or/addressmap.c \
src/or/buffers.c \
@ -65,6 +71,7 @@ src_or_libtor_a_SOURCES = \
src/or/status.c \
$(evdns_source) \
$(tor_platform_source) \
$(onion_ntor_source) \
src/or/config_codedigest.c
#libtor_a_LIBADD = ../common/libor.a ../common/libor-crypto.a \
@ -125,6 +132,7 @@ ORHEADERS = \
src/or/nodelist.h \
src/or/ntmain.h \
src/or/onion.h \
src/or/onion_ntor.h \
src/or/or.h \
src/or/transports.h \
src/or/policies.h \

315
src/or/onion_ntor.c Normal file
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@ -0,0 +1,315 @@
/* Copyright (c) 2012, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#include "orconfig.h"
#include "onion_ntor.h"
#include "crypto.h"
#include "torlog.h"
#include "util.h"
/** Storage held by a client while waiting for an ntor reply from a server. */
struct ntor_handshake_state_t {
/** Identity digest of the router we're talking to. */
uint8_t router_id[DIGEST_LEN];
/** Onion key of the router we're talking to. */
curve25519_public_key_t pubkey_B;
/**
* Short-lived keypair for use with this handshake.
* @{ */
curve25519_secret_key_t seckey_x;
curve25519_public_key_t pubkey_X;
/** @} */
};
/** Free storage held in an ntor handshake state. */
void
ntor_handshake_state_free(ntor_handshake_state_t *state)
{
if (!state)
return;
memwipe(state, 0, sizeof(*state));
tor_free(state);
}
/** Convenience function to represent HMAC_SHA256 as our instantiation of
* ntor's "tweaked hash'. Hash the <b>inp_len</b> bytes at <b>inp</b> into
* a DIGEST256_LEN-byte digest at <b>out</b>, with the hash changing
* depending on the value of <b>tweak</b>. */
static void
h_tweak(uint8_t *out,
const uint8_t *inp, size_t inp_len,
const char *tweak)
{
size_t tweak_len = strlen(tweak);
crypto_hmac_sha256((char*)out, tweak, tweak_len, (const char*)inp, inp_len);
}
/** Wrapper around a set of tweak-values for use with the ntor handshake. */
typedef struct tweakset_t {
const char *t_mac;
const char *t_key;
const char *t_verify;
const char *m_expand;
} tweakset_t;
/** The tweaks to be used with our handshake. */
const tweakset_t proto1_tweaks = {
#define PROTOID "ntor-curve25519-sha256-1"
#define PROTOID_LEN 24
PROTOID ":mac",
PROTOID ":key_extract",
PROTOID ":verify",
PROTOID ":key_expand"
};
/** Convenience macro: copy <b>len</b> bytes from <b>inp</b> to <b>ptr</b>,
* and advance <b>ptr</b> by the number of bytes copied. */
#define APPEND(ptr, inp, len) \
STMT_BEGIN { \
memcpy(ptr, (inp), (len)); \
ptr += len; \
} STMT_END
/**
* Compute the first client-side step of the ntor handshake for communicating
* with a server whose DIGEST_LEN-byte server identity is <b>router_id</b>,
* and whose onion key is <b>router_key</b>. Store the NTOR_ONIONSKIN_LEN-byte
* message in <b>onion_skin_out</b>, and store the handshake state in
* *<b>handshake_state_out</b>. Return 0 on success, -1 on failure.
*/
int
onion_skin_ntor_create(const uint8_t *router_id,
const curve25519_public_key_t *router_key,
ntor_handshake_state_t **handshake_state_out,
uint8_t *onion_skin_out)
{
ntor_handshake_state_t *state;
uint8_t *op;
state = tor_malloc_zero(sizeof(ntor_handshake_state_t));
memcpy(state->router_id, router_id, DIGEST_LEN);
memcpy(&state->pubkey_B, router_key, sizeof(curve25519_public_key_t));
curve25519_secret_key_generate(&state->seckey_x, 0);
curve25519_public_key_generate(&state->pubkey_X, &state->seckey_x);
op = onion_skin_out;
APPEND(op, router_id, DIGEST_LEN);
APPEND(op, router_key->public_key, CURVE25519_PUBKEY_LEN);
APPEND(op, state->pubkey_X.public_key, CURVE25519_PUBKEY_LEN);
tor_assert(op == onion_skin_out + NTOR_ONIONSKIN_LEN);
*handshake_state_out = state;
return 0;
}
#define SERVER_STR "Server"
#define SERVER_STR_LEN 6
#define SECRET_INPUT_LEN (CURVE25519_PUBKEY_LEN * 3 + \
CURVE25519_OUTPUT_LEN * 2 + \
DIGEST_LEN + PROTOID_LEN)
#define AUTH_INPUT_LEN (DIGEST256_LEN + DIGEST_LEN + \
CURVE25519_PUBKEY_LEN*3 + \
PROTOID_LEN + SERVER_STR_LEN)
/**
* Perform the server side of an ntor handshake. Given an
* NTOR_ONIONSKIN_LEN-byte message in <b>onion_skin</b>, our own identity
* fingerprint as <b>my_node_id</b>, and an associative array mapping public
* onion keys to curve25519_keypair_t in <b>private_keys</b>, attempt to
* perform the handshake. Write an NTOR_REPLY_LEN-byte message to send back
* to the client into <b>handshake_reply_out</b>, and generate
* <b>key_out_len</b> bytes of key material in <b>key_out</b>. Return 0 on
* success, -1 on failure.
*/
int
onion_skin_ntor_server_handshake(const uint8_t *onion_skin,
const di_digest256_map_t *private_keys,
const uint8_t *my_node_id,
uint8_t *handshake_reply_out,
uint8_t *key_out,
size_t key_out_len)
{
const tweakset_t *T = &proto1_tweaks;
/* Sensitive stack-allocated material. Kept in an anonymous struct to make
* it easy to wipe. */
struct {
uint8_t secret_input[SECRET_INPUT_LEN];
uint8_t auth_input[AUTH_INPUT_LEN];
curve25519_public_key_t pubkey_X;
curve25519_secret_key_t seckey_y;
curve25519_public_key_t pubkey_Y;
uint8_t verify[DIGEST256_LEN];
} s;
uint8_t *si = s.secret_input, *ai = s.auth_input;
const curve25519_keypair_t *keypair_bB;
int bad;
/* Decode the onion skin */
/* XXXX Does this possible early-return business threaten our security? */
if (tor_memneq(onion_skin, my_node_id, DIGEST_LEN))
return -1;
keypair_bB = dimap_search(private_keys, onion_skin + DIGEST_LEN, NULL);
if (!keypair_bB)
return -1;
memcpy(s.pubkey_X.public_key, onion_skin+DIGEST_LEN+DIGEST256_LEN,
CURVE25519_PUBKEY_LEN);
/* Make y, Y */
curve25519_secret_key_generate(&s.seckey_y, 0);
curve25519_public_key_generate(&s.pubkey_Y, &s.seckey_y);
/* NOTE: If we ever use a group other than curve25519, or a different
* representation for its points, we may need to perform different or
* additional checks on X here and on Y in the client handshake, or lose our
* security properties. What checks we need would depend on the properties
* of the group and its representation.
*
* In short: if you use anything other than curve25519, this aspect of the
* code will need to be reconsidered carefully. */
/* build secret_input */
curve25519_handshake(si, &s.seckey_y, &s.pubkey_X);
bad = tor_memeq(si,
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00", 32);
si += CURVE25519_OUTPUT_LEN;
curve25519_handshake(si, &keypair_bB->seckey, &s.pubkey_X);
bad |= tor_memeq(si,
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00", 32);
si += CURVE25519_OUTPUT_LEN;
APPEND(si, my_node_id, DIGEST_LEN);
APPEND(si, keypair_bB->pubkey.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, s.pubkey_X.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, s.pubkey_Y.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, PROTOID, PROTOID_LEN);
tor_assert(si == s.secret_input + sizeof(s.secret_input));
/* Compute hashes of secret_input */
h_tweak(s.verify, s.secret_input, sizeof(s.secret_input), T->t_verify);
/* Compute auth_input */
APPEND(ai, s.verify, DIGEST256_LEN);
APPEND(ai, my_node_id, DIGEST_LEN);
APPEND(ai, keypair_bB->pubkey.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, s.pubkey_Y.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, s.pubkey_X.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, PROTOID, PROTOID_LEN);
APPEND(ai, SERVER_STR, SERVER_STR_LEN);
tor_assert(ai == s.auth_input + sizeof(s.auth_input));
/* Build the reply */
memcpy(handshake_reply_out, s.pubkey_Y.public_key, CURVE25519_PUBKEY_LEN);
h_tweak(handshake_reply_out+CURVE25519_PUBKEY_LEN,
s.auth_input, sizeof(s.auth_input),
T->t_mac);
/* Generate the key material */
crypto_expand_key_material_rfc5869_sha256(
s.secret_input, sizeof(s.secret_input),
(const uint8_t*)T->t_key, strlen(T->t_key),
(const uint8_t*)T->m_expand, strlen(T->m_expand),
key_out, key_out_len);
/* Wipe all of our local state */
memwipe(&s, 0, sizeof(s));
return bad ? -1 : 0;
}
/**
* Perform the final client side of the ntor handshake, using the state in
* <b>handshake_state</b> and the server's NTOR_REPLY_LEN-byte reply in
* <b>handshake_reply</b>. Generate <b>key_out_len</b> bytes of key material
* in <b>key_out</b>. Return 0 on success, -1 on failure.
*/
int
onion_skin_ntor_client_handshake(
const ntor_handshake_state_t *handshake_state,
const uint8_t *handshake_reply,
uint8_t *key_out,
size_t key_out_len)
{
const tweakset_t *T = &proto1_tweaks;
/* Sensitive stack-allocated material. Kept in an anonymous struct to make
* it easy to wipe. */
struct {
curve25519_public_key_t pubkey_Y;
uint8_t secret_input[SECRET_INPUT_LEN];
uint8_t verify[DIGEST256_LEN];
uint8_t auth_input[AUTH_INPUT_LEN];
uint8_t auth[DIGEST256_LEN];
} s;
uint8_t *ai = s.auth_input, *si = s.secret_input;
const uint8_t *auth_candidate;
int bad;
/* Decode input */
memcpy(s.pubkey_Y.public_key, handshake_reply, CURVE25519_PUBKEY_LEN);
auth_candidate = handshake_reply + CURVE25519_PUBKEY_LEN;
/* See note in server_handshake above about checking points. The
* circumstances under which we'd need to check Y for membership are
* different than those under which we'd be checking X. */
/* Compute secret_input */
curve25519_handshake(si, &handshake_state->seckey_x, &s.pubkey_Y);
bad = tor_memeq(si,
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00", 32);
si += CURVE25519_OUTPUT_LEN;
curve25519_handshake(si, &handshake_state->seckey_x,
&handshake_state->pubkey_B);
bad |= tor_memeq(si,
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x00\x00\x00\x00\x00\x00\x00", 32);
si += CURVE25519_OUTPUT_LEN;
APPEND(si, handshake_state->router_id, DIGEST_LEN);
APPEND(si, handshake_state->pubkey_B.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, handshake_state->pubkey_X.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, s.pubkey_Y.public_key, CURVE25519_PUBKEY_LEN);
APPEND(si, PROTOID, PROTOID_LEN);
tor_assert(si == s.secret_input + sizeof(s.secret_input));
/* Compute verify from secret_input */
h_tweak(s.verify, s.secret_input, sizeof(s.secret_input), T->t_verify);
/* Compute auth_input */
APPEND(ai, s.verify, DIGEST256_LEN);
APPEND(ai, handshake_state->router_id, DIGEST_LEN);
APPEND(ai, handshake_state->pubkey_B.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, s.pubkey_Y.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, handshake_state->pubkey_X.public_key, CURVE25519_PUBKEY_LEN);
APPEND(ai, PROTOID, PROTOID_LEN);
APPEND(ai, SERVER_STR, SERVER_STR_LEN);
tor_assert(ai == s.auth_input + sizeof(s.auth_input));
/* Compute auth */
h_tweak(s.auth, s.auth_input, sizeof(s.auth_input), T->t_mac);
bad |= tor_memneq(s.auth, auth_candidate, DIGEST256_LEN);
crypto_expand_key_material_rfc5869_sha256(
s.secret_input, sizeof(s.secret_input),
(const uint8_t*)T->t_key, strlen(T->t_key),
(const uint8_t*)T->m_expand, strlen(T->m_expand),
key_out, key_out_len);
memwipe(&s, 0, sizeof(s));
return bad ? -1 : 0;
}

49
src/or/onion_ntor.h Normal file
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@ -0,0 +1,49 @@
/* Copyright (c) 2012, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#ifndef TOR_ONION_NTOR_H
#define TOR_ONION_NTOR_H
#include "torint.h"
#include "crypto_curve25519.h"
#include "di_ops.h"
/** State to be maintained by a client between sending an ntor onionskin
* and receiving a reply. */
typedef struct ntor_handshake_state_t ntor_handshake_state_t;
/** Length of an ntor onionskin, as sent from the client to server. */
#define NTOR_ONIONSKIN_LEN 84
/** Length of an ntor reply, as sent from server to client. */
#define NTOR_REPLY_LEN 64
/** A paired public and private key for curve25519.
* XXXX024 move this structure somewhere smarter.
**/
typedef struct curve25519_keypair_t {
curve25519_public_key_t pubkey;
curve25519_secret_key_t seckey;
} curve25519_keypair_t;
void ntor_handshake_state_free(ntor_handshake_state_t *state);
int onion_skin_ntor_create(const uint8_t *router_id,
const curve25519_public_key_t *router_key,
ntor_handshake_state_t **handshake_state_out,
uint8_t *onion_skin_out);
int onion_skin_ntor_server_handshake(const uint8_t *onion_skin,
const di_digest256_map_t *private_keys,
const uint8_t *my_node_id,
uint8_t *handshake_reply_out,
uint8_t *key_out,
size_t key_out_len);
int onion_skin_ntor_client_handshake(
const ntor_handshake_state_t *handshake_state,
const uint8_t *handshake_reply,
uint8_t *key_out,
size_t key_out_len);
#endif

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@ -21,6 +21,10 @@ const char tor_git_revision[] = "";
#include "onion.h"
#include "relay.h"
#include "config.h"
#ifdef CURVE25519_ENABLED
#include "crypto_curve25519.h"
#include "onion_ntor.h"
#endif
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_PROCESS_CPUTIME_ID)
static uint64_t nanostart;
@ -122,7 +126,7 @@ bench_onion_TAP(void)
crypto_dh_free(dh_out);
}
end = perftime();
printf("Client-side, part 1: %f msec.\n", NANOCOUNT(start, end, iters)/1e6);
printf("Client-side, part 1: %f usec.\n", NANOCOUNT(start, end, iters)/1e3);
onion_skin_create(key, &dh_out, os);
start = perftime();
@ -131,8 +135,8 @@ bench_onion_TAP(void)
onion_skin_server_handshake(os, key, NULL, or, key_out, sizeof(key_out));
}
end = perftime();
printf("Server-side, key guessed right: %f msec\n",
NANOCOUNT(start, end, iters)/1e6);
printf("Server-side, key guessed right: %f usec\n",
NANOCOUNT(start, end, iters)/1e3);
start = perftime();
for (i = 0; i < iters; ++i) {
@ -140,8 +144,8 @@ bench_onion_TAP(void)
onion_skin_server_handshake(os, key2, key, or, key_out, sizeof(key_out));
}
end = perftime();
printf("Server-side, key guessed wrong: %f msec.\n",
NANOCOUNT(start, end, iters)/1e6);
printf("Server-side, key guessed wrong: %f usec.\n",
NANOCOUNT(start, end, iters)/1e3);
start = perftime();
for (i = 0; i < iters; ++i) {
@ -153,12 +157,69 @@ bench_onion_TAP(void)
tor_assert(s == 0);
}
end = perftime();
printf("Client-side, part 2: %f msec.\n",
NANOCOUNT(start, end, iters)/1e6);
printf("Client-side, part 2: %f usec.\n",
NANOCOUNT(start, end, iters)/1e3);
crypto_pk_free(key);
}
#ifdef CURVE25519_ENABLED
static void
bench_onion_ntor(void)
{
const int iters = 1<<10;
int i;
curve25519_keypair_t keypair1, keypair2;
uint64_t start, end;
uint8_t os[NTOR_ONIONSKIN_LEN];
uint8_t or[NTOR_REPLY_LEN];
ntor_handshake_state_t *state = NULL;
uint8_t nodeid[DIGEST_LEN];
di_digest256_map_t *keymap = NULL;
curve25519_secret_key_generate(&keypair1.seckey, 0);
curve25519_public_key_generate(&keypair1.pubkey, &keypair1.seckey);
curve25519_secret_key_generate(&keypair2.seckey, 0);
curve25519_public_key_generate(&keypair2.pubkey, &keypair2.seckey);
dimap_add_entry(&keymap, keypair1.pubkey.public_key, &keypair1);
dimap_add_entry(&keymap, keypair2.pubkey.public_key, &keypair2);
reset_perftime();
start = perftime();
for (i = 0; i < iters; ++i) {
onion_skin_ntor_create(nodeid, &keypair1.pubkey, &state, os);
ntor_handshake_state_free(state);
}
end = perftime();
printf("Client-side, part 1: %f usec.\n", NANOCOUNT(start, end, iters)/1e3);
onion_skin_ntor_create(nodeid, &keypair1.pubkey, &state, os);
start = perftime();
for (i = 0; i < iters; ++i) {
uint8_t key_out[CPATH_KEY_MATERIAL_LEN];
onion_skin_ntor_server_handshake(os, keymap, nodeid, or,
key_out, sizeof(key_out));
}
end = perftime();
printf("Server-side: %f usec\n",
NANOCOUNT(start, end, iters)/1e3);
start = perftime();
for (i = 0; i < iters; ++i) {
uint8_t key_out[CPATH_KEY_MATERIAL_LEN];
int s;
s = onion_skin_ntor_client_handshake(state, or, key_out, sizeof(key_out));
tor_assert(s == 0);
}
end = perftime();
printf("Client-side, part 2: %f usec.\n",
NANOCOUNT(start, end, iters)/1e3);
ntor_handshake_state_free(state);
dimap_free(keymap, NULL);
}
#endif
static void
bench_cell_aes(void)
{
@ -325,6 +386,9 @@ static struct benchmark_t benchmarks[] = {
ENT(dmap),
ENT(aes),
ENT(onion_TAP),
#ifdef CURVE25519_ENABLED
ENT(onion_ntor),
#endif
ENT(cell_aes),
ENT(cell_ops),
{NULL,NULL,0}

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@ -57,6 +57,10 @@ double fabs(double x);
#include "policies.h"
#include "rephist.h"
#include "routerparse.h"
#ifdef CURVE25519_ENABLED
#include "crypto_curve25519.h"
#include "onion_ntor.h"
#endif
#ifdef USE_DMALLOC
#include <dmalloc.h>
@ -856,6 +860,59 @@ test_onion_handshake(void)
crypto_pk_free(pk);
}
#ifdef CURVE25519_ENABLED
static void
test_ntor_handshake(void *arg)
{
/* client-side */
ntor_handshake_state_t *c_state = NULL;
uint8_t c_buf[NTOR_ONIONSKIN_LEN];
uint8_t c_keys[400];
/* server-side */
di_digest256_map_t *s_keymap=NULL;
curve25519_keypair_t s_keypair;
uint8_t s_buf[NTOR_REPLY_LEN];
uint8_t s_keys[400];
/* shared */
const curve25519_public_key_t *server_pubkey;
uint8_t node_id[20] = "abcdefghijklmnopqrst";
(void) arg;
/* Make the server some keys */
curve25519_secret_key_generate(&s_keypair.seckey, 0);
curve25519_public_key_generate(&s_keypair.pubkey, &s_keypair.seckey);
dimap_add_entry(&s_keymap, s_keypair.pubkey.public_key, &s_keypair);
server_pubkey = &s_keypair.pubkey;
/* client handshake 1. */
memset(c_buf, 0, NTOR_ONIONSKIN_LEN);
tt_int_op(0, ==, onion_skin_ntor_create(node_id, server_pubkey,
&c_state, c_buf));
/* server handshake */
memset(s_buf, 0, NTOR_REPLY_LEN);
memset(s_keys, 0, 40);
tt_int_op(0, ==, onion_skin_ntor_server_handshake(c_buf, s_keymap, node_id,
s_buf, s_keys, 400));
/* client handshake 2 */
memset(c_keys, 0, 40);
tt_int_op(0, ==, onion_skin_ntor_client_handshake(c_state, s_buf,
c_keys, 400));
test_memeq(c_keys, s_keys, 400);
memset(s_buf, 0, 40);
test_memneq(c_keys, s_buf, 40);
done:
ntor_handshake_state_free(c_state);
dimap_free(s_keymap, NULL);
}
#endif
static void
test_circuit_timeout(void)
{
@ -1947,6 +2004,9 @@ static struct testcase_t test_array[] = {
ENT(buffers),
{ "buffer_copy", test_buffer_copy, 0, NULL, NULL },
ENT(onion_handshake),
#ifdef CURVE25519_ENABLED
{ "ntor_handshake", test_ntor_handshake, 0, NULL, NULL },
#endif
ENT(circuit_timeout),
ENT(policies),
ENT(rend_fns),