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@@ -9,6 +9,7 @@
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#define HS_INTROPOINT_PRIVATE
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#include "or.h"
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+#include "config.h"
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#include "circuitlist.h"
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#include "circuituse.h"
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#include "config.h"
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@@ -16,27 +17,52 @@
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#include "rendmid.h"
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#include "rephist.h"
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-#include "hs/cell_establish_intro.h"
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+/* Trunnel */
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+#include "ed25519_cert.h"
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#include "hs/cell_common.h"
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+#include "hs/cell_establish_intro.h"
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+#include "hs/cell_introduce1.h"
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+
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#include "hs_circuitmap.h"
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#include "hs_intropoint.h"
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#include "hs_common.h"
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-/** Extract the authentication key from an ESTABLISH_INTRO <b>cell</b> and
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- * place it in <b>auth_key_out</b>. */
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+/** Extract the authentication key from an ESTABLISH_INTRO or INTRODUCE1 using
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+ * the given <b>cell_type</b> from <b>cell</b> and place it in
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+ * <b>auth_key_out</b>. */
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STATIC void
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-get_auth_key_from_establish_intro_cell(ed25519_public_key_t *auth_key_out,
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- const hs_cell_establish_intro_t *cell)
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+get_auth_key_from_cell(ed25519_public_key_t *auth_key_out,
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+ unsigned int cell_type, const void *cell)
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{
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+ size_t auth_key_len;
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+ const uint8_t *key_array;
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+
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tor_assert(auth_key_out);
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+ tor_assert(cell);
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- const uint8_t *key_array =
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- hs_cell_establish_intro_getconstarray_auth_key(cell);
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+ switch (cell_type) {
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+ case RELAY_COMMAND_ESTABLISH_INTRO:
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+ {
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+ const hs_cell_establish_intro_t *c_cell = cell;
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+ key_array = hs_cell_establish_intro_getconstarray_auth_key(c_cell);
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+ auth_key_len = hs_cell_establish_intro_getlen_auth_key(c_cell);
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+ break;
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+ }
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+ case RELAY_COMMAND_INTRODUCE1:
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+ {
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+ const hs_cell_introduce1_t *c_cell = cell;
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+ key_array = hs_cell_introduce1_getconstarray_auth_key(cell);
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+ auth_key_len = hs_cell_introduce1_getlen_auth_key(c_cell);
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+ break;
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+ }
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+ default:
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+ /* Getting here is really bad as it means we got a unknown cell type from
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+ * this file where every call has an hardcoded value. */
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+ tor_assert(0);
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+ }
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tor_assert(key_array);
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- tor_assert(hs_cell_establish_intro_getlen_auth_key(cell) ==
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- sizeof(auth_key_out->pubkey));
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-
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- memcpy(auth_key_out->pubkey, key_array, cell->auth_key_len);
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+ tor_assert(auth_key_len == sizeof(auth_key_out->pubkey));
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+ memcpy(auth_key_out->pubkey, key_array, auth_key_len);
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}
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/** We received an ESTABLISH_INTRO <b>cell</b>. Verify its signature and MAC,
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@@ -79,7 +105,7 @@ verify_establish_intro_cell(const hs_cell_establish_intro_t *cell,
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memcpy(sig_struct.sig, sig_array, cell->sig_len);
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ed25519_public_key_t auth_key;
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- get_auth_key_from_establish_intro_cell(&auth_key, cell);
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+ get_auth_key_from_cell(&auth_key, RELAY_COMMAND_ESTABLISH_INTRO, cell);
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const size_t sig_msg_len = cell->end_sig_fields - msg;
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int sig_mismatch = ed25519_checksig_prefixed(&sig_struct,
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@@ -154,7 +180,8 @@ handle_verified_establish_intro_cell(or_circuit_t *circ,
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{
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/* Get the auth key of this intro point */
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ed25519_public_key_t auth_key;
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- get_auth_key_from_establish_intro_cell(&auth_key, parsed_cell);
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+ get_auth_key_from_cell(&auth_key, RELAY_COMMAND_ESTABLISH_INTRO,
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+ parsed_cell);
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/* Then notify the hidden service that the intro point is established by
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sending an INTRO_ESTABLISHED cell */
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@@ -232,26 +259,38 @@ handle_establish_intro(or_circuit_t *circ, const uint8_t *request,
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return retval;
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}
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-/* Return True if circuit is suitable for becoming an intro circuit. */
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-int
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-hs_intro_circuit_is_suitable(const or_circuit_t *circ)
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+/* Return True if circuit is suitable for being an intro circuit. */
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+static int
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+circuit_is_suitable_intro_point(const or_circuit_t *circ,
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+ const char *log_cell_type_str)
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{
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+ tor_assert(circ);
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+ tor_assert(log_cell_type_str);
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+
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/* Basic circuit state sanity checks. */
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if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
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log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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- "Rejecting ESTABLISH_INTRO on non-OR circuit.");
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+ "Rejecting %s on non-OR circuit.", log_cell_type_str);
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return 0;
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}
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if (circ->base_.n_chan) {
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log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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- "Rejecting ESTABLISH_INTRO on non-edge circuit.");
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+ "Rejecting %s on non-edge circuit.", log_cell_type_str);
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return 0;
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}
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+ /* Suitable. */
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return 1;
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}
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+/* Return True if circuit is suitable for becoming an intro circuit. */
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+int
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+hs_intro_circuit_is_suitable(const or_circuit_t *circ)
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+{
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+ return circuit_is_suitable_intro_point(circ, "ESTABLISH_INTRO");
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+}
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+
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/* We just received an ESTABLISH_INTRO cell in <b>circ</b>. Figure out of it's
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* a legacy or a next gen cell, and pass it to the appropriate handler. */
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int
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@@ -286,3 +325,266 @@ hs_intro_received_establish_intro(or_circuit_t *circ, const uint8_t *request,
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return -1;
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}
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+/* Send an INTRODUCE_ACK cell onto the circuit <b>circ</b> with the status
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+ * value in <b>status</b>. Depending on the status, it can be ACK or a NACK.
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+ * Return 0 on success else a negative value on error which will close the
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+ * circuit. */
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+static int
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+send_introduce_ack_cell(or_circuit_t *circ, hs_intro_ack_status_t status)
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+{
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+ int ret = -1;
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+ uint8_t *encoded_cell = NULL;
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+ ssize_t encoded_len, result_len;
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+ hs_cell_introduce_ack_t *cell;
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+ cell_extension_t *ext;
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+
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+ tor_assert(circ);
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+
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+ /* Setup the INTRODUCE_ACK cell. We have no extensions so the N_EXTENSIONS
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+ * field is set to 0 by default with a new object. */
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+ cell = hs_cell_introduce_ack_new();
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+ ret = hs_cell_introduce_ack_set_status(cell, status);
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+ /* We have no cell extensions in an INTRODUCE_ACK cell. */
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+ ext = cell_extension_new();
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+ cell_extension_set_num(ext, 0);
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+ hs_cell_introduce_ack_set_extensions(cell, ext);
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+ /* A wrong status is a very bad code flow error as this value is controlled
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+ * by the code in this file and not an external input. This means we use a
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+ * code that is not known by the trunnel ABI. */
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+ tor_assert(ret == 0);
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+ /* Encode the payload. We should never fail to get the encoded length. */
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+ encoded_len = hs_cell_introduce_ack_encoded_len(cell);
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+ tor_assert(encoded_len > 0);
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+ encoded_cell = tor_malloc_zero(encoded_len);
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+ result_len = hs_cell_introduce_ack_encode(encoded_cell, encoded_len, cell);
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+ tor_assert(encoded_len == result_len);
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+
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+ ret = relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(circ),
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+ RELAY_COMMAND_INTRODUCE_ACK,
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+ (char *) encoded_cell, encoded_len,
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+ NULL);
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+ /* On failure, the above function will close the circuit. */
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+ hs_cell_introduce_ack_free(cell);
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+ tor_free(encoded_cell);
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+ return ret;
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+}
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+
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+/* Validate a parsed INTRODUCE1 <b>cell</b>. Return 0 if valid or else a
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+ * negative value for an invalid cell that should be NACKed. */
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+static int
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+validate_introduce1_parsed_cell(const hs_cell_introduce1_t *cell)
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+{
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+ size_t legacy_key_id_len;
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+ const uint8_t *legacy_key_id;
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+
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+ tor_assert(cell);
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+
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+ /* This code path SHOULD NEVER be reached if the cell is a legacy type so
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+ * safety net here. The legacy ID must be zeroes in this case. */
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+ legacy_key_id_len = hs_cell_introduce1_getlen_legacy_key_id(cell);
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+ legacy_key_id = hs_cell_introduce1_getconstarray_legacy_key_id(cell);
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+ if (BUG(!tor_mem_is_zero((char *) legacy_key_id, legacy_key_id_len))) {
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+ goto invalid;
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+ }
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+
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+ /* The auth key of an INTRODUCE1 should be of type ed25519 thus leading to a
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+ * known fixed length as well. */
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+ if (hs_cell_introduce1_get_auth_key_type(cell) !=
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+ HS_INTRO_AUTH_KEY_TYPE_ED25519) {
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+ log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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+ "Rejecting invalid INTRODUCE1 cell auth key type. "
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+ "Responding with NACK.");
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+ goto invalid;
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+ }
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+ if (hs_cell_introduce1_get_auth_key_len(cell) != ED25519_PUBKEY_LEN ||
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+ hs_cell_introduce1_getlen_auth_key(cell) != ED25519_PUBKEY_LEN) {
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+ log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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+ "Rejecting invalid INTRODUCE1 cell auth key length. "
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+ "Responding with NACK.");
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+ goto invalid;
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+ }
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+ if (hs_cell_introduce1_getlen_encrypted(cell) == 0) {
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+ log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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+ "Rejecting invalid INTRODUCE1 cell encrypted length. "
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+ "Responding with NACK.");
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+ goto invalid;
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+ }
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+
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+ return 0;
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+ invalid:
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+ return -1;
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+}
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+
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+/* We just received a non legacy INTRODUCE1 cell on <b>client_circ</b> with
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+ * the payload in <b>request</b> of size <b>request_len</b>. Return 0 if
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+ * everything went well, or -1 if an error occured. This function is in charge
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+ * of sending back an INTRODUCE_ACK cell and will close client_circ on error.
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+ */
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+static int
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+handle_introduce1(or_circuit_t *client_circ, const uint8_t *request,
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+ size_t request_len)
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+{
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+ int ret = -1;
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+ or_circuit_t *service_circ;
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+ hs_cell_introduce1_t *parsed_cell;
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+ hs_intro_ack_status_t status = HS_INTRO_ACK_STATUS_SUCCESS;
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+
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+ tor_assert(client_circ);
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+ tor_assert(request);
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+
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+ /* Parse cell. Note that we can only parse the non encrypted section for
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+ * which we'll use the authentication key to find the service introduction
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+ * circuit and relay the cell on it. */
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+ ssize_t cell_size = hs_cell_introduce1_parse(&parsed_cell, request,
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+ request_len);
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+ if (cell_size < 0) {
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+ log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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+ "Rejecting %s INTRODUCE1 cell. Responding with NACK.",
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+ cell_size == -1 ? "invalid" : "truncated");
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+ /* Inform client that the INTRODUCE1 has a bad format. */
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+ status = HS_INTRO_ACK_STATUS_BAD_FORMAT;
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+ goto send_ack;
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+ }
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+
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+ /* Once parsed, validate the cell expected format once parsed. */
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+ if (validate_introduce1_parsed_cell(parsed_cell) < 0) {
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+ /* Inform client that the INTRODUCE1 has bad format. */
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+ status = HS_INTRO_ACK_STATUS_BAD_FORMAT;
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+ goto send_ack;
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+ }
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+
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+ /* Find introduction circuit through our circuit map. */
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+ {
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+ ed25519_public_key_t auth_key;
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+ get_auth_key_from_cell(&auth_key, RELAY_COMMAND_INTRODUCE1, parsed_cell);
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+ service_circ = hs_circuitmap_get_intro_circ_v3(&auth_key);
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+ if (service_circ == NULL) {
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+ char b64_key[ED25519_BASE64_LEN + 1];
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+ ed25519_public_to_base64(b64_key, &auth_key);
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+ log_info(LD_REND, "No intro circuit found for INTRODUCE1 cell "
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+ "with auth key %s from circuit %" PRIu32 ". "
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+ "Responding with NACK.",
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+ safe_str(b64_key), client_circ->p_circ_id);
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+ /* Inform the client that we don't know the requested service ID. */
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+ status = HS_INTRO_ACK_STATUS_UNKNOWN_ID;
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+ goto send_ack;
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+ }
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+ }
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+
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+ /* Relay the cell to the service on its intro circuit with an INTRODUCE2
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+ * cell which is the same exact payload. */
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+ if (relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(service_circ),
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+ RELAY_COMMAND_INTRODUCE2,
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+ (char *) request, request_len, NULL)) {
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+ log_warn(LD_REND, "Unable to send INTRODUCE2 cell to the service.");
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+ /* Inform the client that we can't relay the cell. */
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+ status = HS_INTRO_ACK_STATUS_CANT_RELAY;
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+ goto send_ack;
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+ }
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+
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+ /* Success! Send an INTRODUCE_ACK success status onto the client circuit. */
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+ status = HS_INTRO_ACK_STATUS_SUCCESS;
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+ ret = 0;
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+
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+ send_ack:
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+ /* Send the INTRODUCE_ACK cell to the client with a specific status. */
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+ if (send_introduce_ack_cell(client_circ, status) < 0) {
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+ log_warn(LD_REND, "Unable to send an INTRODUCE ACK status %d to client.",
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+ status);
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+ /* Circuit has been closed on failure of transmission. */
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+ goto done;
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+ }
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+ if (status != HS_INTRO_ACK_STATUS_SUCCESS) {
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+ /* We just sent a NACK that is a non success status code so close the
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+ * circuit because it's not useful to keep it open. Remember, a client can
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+ * only send one INTRODUCE1 cell on a circuit. */
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+ circuit_mark_for_close(TO_CIRCUIT(client_circ), END_CIRC_REASON_INTERNAL);
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+ }
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+ done:
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+ hs_cell_introduce1_free(parsed_cell);
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+ return ret;
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+}
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+
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+/* Identify if the encoded cell we just received is a legacy one or not. The
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+ * <b>request</b> should be at least DIGEST_LEN bytes long. */
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+static int
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+introduce1_cell_is_legacy(const uint8_t *request)
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+{
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+ tor_assert(request);
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+
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+ /* If the first 20 bytes of the cell (DIGEST_LEN) are NOT zeroes, it
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+ * indicates a legacy cell (v2). */
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+ if (!tor_mem_is_zero((const char *) request, DIGEST_LEN)) {
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+ /* Legacy cell. */
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+ return 1;
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+ }
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+ /* Not a legacy cell. */
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+ return 0;
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+}
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+
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+/* Return true iff the circuit <b>circ</b> is suitable for receiving an
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+ * INTRODUCE1 cell. */
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+static int
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+circuit_is_suitable_for_introduce1(const or_circuit_t *circ)
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+{
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+ tor_assert(circ);
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+
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+ /* First of all, do we have a valid circuit to be an introduction point? */
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+ if (!circuit_is_suitable_intro_point(circ, "INTRODUCE1")) {
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+ return 0;
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+ }
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+
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+ if (circ->already_received_introduce1) {
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+ log_fn(LOG_PROTOCOL_WARN, LD_REND,
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+ "Blocking multiple introductions on the same circuit. "
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+ "Someone might be trying to attack a hidden service through "
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+ "this relay.");
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+ return 0;
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+ }
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+
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+ return 1;
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+}
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+
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+/* We just received an INTRODUCE1 cell on <b>circ</b>. Figure out which type
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+ * it is and pass it to the appropriate handler. Return 0 on success else a
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+ * negative value and the circuit is closed. */
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+int
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+hs_intro_received_introduce1(or_circuit_t *circ, const uint8_t *request,
|
|
|
+ size_t request_len)
|
|
|
+{
|
|
|
+ int ret;
|
|
|
+
|
|
|
+ tor_assert(circ);
|
|
|
+ tor_assert(request);
|
|
|
+
|
|
|
+ /* A cell that can't hold a DIGEST_LEN is invalid as we need to check if
|
|
|
+ * it's a legacy cell or not using the first DIGEST_LEN bytes. */
|
|
|
+ if (request_len < DIGEST_LEN) {
|
|
|
+ log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Invalid INTRODUCE1 cell length.");
|
|
|
+ goto err;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Make sure we have a circuit that can have an INTRODUCE1 cell on it. */
|
|
|
+ if (!circuit_is_suitable_for_introduce1(circ)) {
|
|
|
+ /* We do not send a NACK because the circuit is not suitable for any kind
|
|
|
+ * of response or transmission as it's a violation of the protocol. */
|
|
|
+ goto err;
|
|
|
+ }
|
|
|
+ /* Mark the circuit that we got this cell. None are allowed after this as a
|
|
|
+ * DoS mitigation since one circuit with one client can hammer a service. */
|
|
|
+ circ->already_received_introduce1 = 1;
|
|
|
+
|
|
|
+ /* We are sure here to have at least DIGEST_LEN bytes. */
|
|
|
+ if (introduce1_cell_is_legacy(request)) {
|
|
|
+ /* Handle a legacy cell. */
|
|
|
+ ret = rend_mid_introduce(circ, request, request_len);
|
|
|
+ } else {
|
|
|
+ /* Handle a non legacy cell. */
|
|
|
+ ret = handle_introduce1(circ, request, request_len);
|
|
|
+ }
|
|
|
+ return ret;
|
|
|
+
|
|
|
+ err:
|
|
|
+ circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
|
|
|
+ return -1;
|
|
|
+}
|