Implement scheme to allow ntor requests/responses via older servers (1ed4786d) · Commits · Mike Perry / Tor

src/or/onion.c

+57 −16

Original line number	Diff line number	Diff line
		@@ -337,7 +337,7 @@ onion_skin_server_handshake(int type,
		break;
		case ONION_HANDSHAKE_TYPE_NTOR:
		#ifdef CURVE25519_ENABLED
		if (onionskin_len != NTOR_ONIONSKIN_LEN)
		if (onionskin_len < NTOR_ONIONSKIN_LEN)
		return -1;
		{
		size_t keys_tmp_len = keys_out_len + DIGEST_LEN;
		@@ -409,7 +409,7 @@ onion_skin_client_handshake(int type,
		return 0;
		#ifdef CURVE25519_ENABLED
		case ONION_HANDSHAKE_TYPE_NTOR:
		if (reply_len != NTOR_REPLY_LEN)
		if (reply_len < NTOR_REPLY_LEN)
		return -1;
		{
		size_t keys_tmp_len = keys_out_len + DIGEST_LEN;
		@@ -442,7 +442,8 @@ check_create_cell(const create_cell_t *cell, int unknown_ok)
		{
		switch (cell->cell_type) {
		case CELL_CREATE:
		if (cell->handshake_type != ONION_HANDSHAKE_TYPE_TAP)
		if (cell->handshake_type != ONION_HANDSHAKE_TYPE_TAP &&
		cell->handshake_type != ONION_HANDSHAKE_TYPE_NTOR)
		return -1;
		break;
		case CELL_CREATE_FAST:
		@@ -502,6 +503,14 @@ parse_create2_payload(create_cell_t cell_out, const uint8_t p, size_t p_len)
		return 0;
		}

		/** Magic string which, in a CREATE or EXTEND cell, indicates that a seeming
		* TAP payload is really an ntor payload. We'd do away with this if every
		* relay supported EXTEND2, but we want to be able to extend from A to B with
		* ntor even when A doesn't understand EXTEND2 and so can't generate a
		* CREATE2 cell.
		**/
		#define NTOR_CREATE_MAGIC "ntorNTORntorNTOR"

		/** Parse a CREATE, CREATE_FAST, or CREATE2 cell from <b>cell_in</b> into
		* <b>cell_out</b>. Return 0 on success, -1 on failure. (We reject some
		* syntactically valid CREATE2 cells that we can't generate or react to.) */
		@@ -513,9 +522,16 @@ create_cell_parse(create_cell_t cell_out, const cell_t cell_in)
		switch (cell_in->command) {
		case CELL_CREATE:
		cell_out->cell_type = CELL_CREATE;
		if (tor_memeq(cell_in->payload, NTOR_CREATE_MAGIC, 16)) {
		cell_out->handshake_type = ONION_HANDSHAKE_TYPE_NTOR;
		cell_out->handshake_len = NTOR_ONIONSKIN_LEN;
		memcpy(cell_out->onionskin, cell_in->payload+16, NTOR_ONIONSKIN_LEN);
		} else {
		cell_out->handshake_type = ONION_HANDSHAKE_TYPE_TAP;
		cell_out->handshake_len = TAP_ONIONSKIN_CHALLENGE_LEN;
		memcpy(cell_out->onionskin, cell_in->payload, TAP_ONIONSKIN_CHALLENGE_LEN);
		memcpy(cell_out->onionskin, cell_in->payload,
		TAP_ONIONSKIN_CHALLENGE_LEN);
		}
		break;
		case CELL_CREATE_FAST:
		cell_out->cell_type = CELL_CREATE_FAST;
		@@ -603,7 +619,8 @@ check_extend_cell(const extend_cell_t *cell)
		if (cell->cell_type != RELAY_COMMAND_EXTEND)
		return -1;
		} else if (cell->create_cell.cell_type == CELL_CREATE2) {
		if (cell->cell_type != RELAY_COMMAND_EXTEND2)
		if (cell->cell_type != RELAY_COMMAND_EXTEND2 &&
		cell->cell_type != RELAY_COMMAND_EXTEND)
		return -1;
		} else {
		/* In particular, no CREATE_FAST cells are allowed */
		@@ -647,11 +664,19 @@ extend_cell_parse(extend_cell_t *cell_out, const uint8_t command,
		tor_addr_from_ipv4n(&cell_out->orport_ipv4.addr, get_uint32(payload));
		cell_out->orport_ipv4.port = ntohs(get_uint16(payload+4));
		tor_addr_make_unspec(&cell_out->orport_ipv6.addr);
		if (tor_memeq(payload + 6, NTOR_CREATE_MAGIC, 16)) {
		cell_out->create_cell.cell_type = CELL_CREATE2;
		cell_out->create_cell.handshake_type = ONION_HANDSHAKE_TYPE_NTOR;
		cell_out->create_cell.handshake_len = NTOR_ONIONSKIN_LEN;
		memcpy(cell_out->create_cell.onionskin, payload + 22,
		NTOR_ONIONSKIN_LEN);
		} else {
		cell_out->create_cell.cell_type = CELL_CREATE;
		cell_out->create_cell.handshake_type = ONION_HANDSHAKE_TYPE_TAP;
		cell_out->create_cell.handshake_len = TAP_ONIONSKIN_CHALLENGE_LEN;
		memcpy(cell_out->create_cell.onionskin, payload + 6,
		TAP_ONIONSKIN_CHALLENGE_LEN);
		}
		memcpy(cell_out->node_id, payload + 6 + TAP_ONIONSKIN_CHALLENGE_LEN,
		DIGEST_LEN);
		break;
		@@ -787,17 +812,28 @@ extended_cell_parse(extended_cell_t *cell_out,
		int
		create_cell_format(cell_t cell_out, const create_cell_t cell_in)
		{
		uint8_t *p;
		size_t space;
		if (check_create_cell(cell_in, 0) < 0)
		return -1;

		memset(cell_out->payload, 0, sizeof(cell_out->payload));
		cell_out->command = cell_in->cell_type;

		p = cell_out->payload;
		space = sizeof(cell_out->payload);

		switch (cell_in->cell_type) {
		case CELL_CREATE:
		if (cell_in->handshake_type == ONION_HANDSHAKE_TYPE_NTOR) {
		memcpy(p, NTOR_CREATE_MAGIC, 16);
		p += 16;
		space -= 16;
		}
		/* Fall through */
		case CELL_CREATE_FAST:
		tor_assert(cell_in->handshake_len <= sizeof(cell_out->payload));
		memcpy(cell_out->payload, cell_in->onionskin, cell_in->handshake_len);
		tor_assert(cell_in->handshake_len <= space);
		memcpy(p, cell_in->onionskin, cell_in->handshake_len);
		break;
		case CELL_CREATE2:
		tor_assert(cell_in->handshake_len <= sizeof(cell_out->payload)-4);
		@@ -865,8 +901,13 @@ extend_cell_format(uint8_t command_out, uint16_t len_out,
		*len_out = 6 + TAP_ONIONSKIN_CHALLENGE_LEN + DIGEST_LEN;
		set_uint32(p, tor_addr_to_ipv4n(&cell_in->orport_ipv4.addr));
		set_uint16(p+4, ntohs(cell_in->orport_ipv4.port));
		if (cell_in->create_cell.handshake_type == ONION_HANDSHAKE_TYPE_NTOR) {
		memcpy(p+6, NTOR_CREATE_MAGIC, 16);
		memcpy(p+22, cell_in->create_cell.onionskin, NTOR_ONIONSKIN_LEN);
		} else {
		memcpy(p+6, cell_in->create_cell.onionskin,
		TAP_ONIONSKIN_CHALLENGE_LEN);
		}
		memcpy(p+6+TAP_ONIONSKIN_CHALLENGE_LEN, cell_in->node_id, DIGEST_LEN);
		}
		break;

src/test/test_cell_formats.c

+46 −0

Original line number	Diff line number	Diff line
		@@ -456,6 +456,26 @@ test_cfmt_create_cells(void *arg)
		tt_int_op(-1, ==, create_cell_parse(&cc, &cell));
		#endif

		/* A valid create cell with an ntor payload, in legacy format. */
		memset(&cell, 0, sizeof(cell));
		memset(b, 0, sizeof(b));
		crypto_rand((char*)b, NTOR_ONIONSKIN_LEN);
		cell.command = CELL_CREATE;
		memcpy(cell.payload, "ntorNTORntorNTOR", 16);
		memcpy(cell.payload+16, b, NTOR_ONIONSKIN_LEN);
		#ifdef CURVE25519_ENABLED
		tt_int_op(0, ==, create_cell_parse(&cc, &cell));
		tt_int_op(CELL_CREATE, ==, cc.cell_type);
		tt_int_op(ONION_HANDSHAKE_TYPE_NTOR, ==, cc.handshake_type);
		tt_int_op(NTOR_ONIONSKIN_LEN, ==, cc.handshake_len);
		test_memeq(cc.onionskin, b, NTOR_ONIONSKIN_LEN + 10);
		tt_int_op(0, ==, create_cell_format(&cell2, &cc));
		tt_int_op(cell.command, ==, cell2.command);
		test_memeq(cell.payload, cell2.payload, CELL_PAYLOAD_SIZE);
		#else
		tt_int_op(-1, ==, create_cell_parse(&cc, &cell));
		#endif

		/* == Okay, now let's try to parse some impossible stuff. */

		/* It has to be some kind of a create cell! */
		@@ -573,6 +593,7 @@ test_cfmt_created_cells(void *arg)
		static void
		test_cfmt_extend_cells(void *arg)
		{
		cell_t cell;
		uint8_t b[512];
		extend_cell_t ec;
		create_cell_t *cc = &ec.create_cell;
		@@ -607,6 +628,31 @@ test_cfmt_extend_cells(void *arg)
		tt_int_op(p2_len, ==, 26+TAP_ONIONSKIN_CHALLENGE_LEN);
		test_memeq(p2, p, RELAY_PAYLOAD_SIZE);

		/* Let's do an ntor stuffed in a legacy EXTEND cell */
		memset(p, 0, sizeof(p));
		memset(b, 0, sizeof(b));
		crypto_rand((char*)b, NTOR_ONIONSKIN_LEN);
		memcpy(p, "\x12\xf4\x00\x01\x01\x02", 6); /* 18 244 0 1 : 258 */
		memcpy(p+6,"ntorNTORntorNTOR", 16);
		memcpy(p+22, b, NTOR_ONIONSKIN_LEN);
		memcpy(p+6+TAP_ONIONSKIN_CHALLENGE_LEN, "electroencephalogram", 20);
		tt_int_op(0, ==, extend_cell_parse(&ec, RELAY_COMMAND_EXTEND,
		p, 26+TAP_ONIONSKIN_CHALLENGE_LEN));
		tt_int_op(RELAY_COMMAND_EXTEND, ==, ec.cell_type);
		tt_str_op("18.244.0.1", ==, fmt_addr(&ec.orport_ipv4.addr));
		tt_int_op(258, ==, ec.orport_ipv4.port);
		tt_int_op(AF_UNSPEC, ==, tor_addr_family(&ec.orport_ipv6.addr));
		test_memeq(ec.node_id, "electroencephalogram", 20);
		tt_int_op(cc->cell_type, ==, CELL_CREATE2);
		tt_int_op(cc->handshake_type, ==, ONION_HANDSHAKE_TYPE_NTOR);
		tt_int_op(cc->handshake_len, ==, NTOR_ONIONSKIN_LEN);
		test_memeq(cc->onionskin, b, NTOR_ONIONSKIN_LEN+20);
		tt_int_op(0, ==, extend_cell_format(&p2_cmd, &p2_len, p2, &ec));
		tt_int_op(p2_cmd, ==, RELAY_COMMAND_EXTEND);
		tt_int_op(p2_len, ==, 26+TAP_ONIONSKIN_CHALLENGE_LEN);
		test_memeq(p2, p, RELAY_PAYLOAD_SIZE);
		tt_int_op(0, ==, create_cell_format(&cell, cc));

		/* Now let's do a minimal ntor EXTEND2 cell. */
		memset(&ec, 0xff, sizeof(ec));
		memset(p, 0, sizeof(p));