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- /* Copyright (c) 2001 Matej Pfajfar.
- * Copyright (c) 2001-2004, Roger Dingledine.
- * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
- * Copyright (c) 2007-2018, The Tor Project, Inc. */
- /* See LICENSE for licensing information */
- #include "or.h"
- #include "config.h"
- #include "relay_crypto.h"
- #include "relay.h"
- /** Update digest from the payload of cell. Assign integrity part to
- * cell.
- */
- static void
- relay_set_digest(crypto_digest_t *digest, cell_t *cell)
- {
- char integrity[4];
- relay_header_t rh;
- crypto_digest_add_bytes(digest, (char*)cell->payload, CELL_PAYLOAD_SIZE);
- crypto_digest_get_digest(digest, integrity, 4);
- // log_fn(LOG_DEBUG,"Putting digest of %u %u %u %u into relay cell.",
- // integrity[0], integrity[1], integrity[2], integrity[3]);
- relay_header_unpack(&rh, cell->payload);
- memcpy(rh.integrity, integrity, 4);
- relay_header_pack(cell->payload, &rh);
- }
- /** Does the digest for this circuit indicate that this cell is for us?
- *
- * Update digest from the payload of cell (with the integrity part set
- * to 0). If the integrity part is valid, return 1, else restore digest
- * and cell to their original state and return 0.
- */
- static int
- relay_digest_matches(crypto_digest_t *digest, cell_t *cell)
- {
- uint32_t received_integrity, calculated_integrity;
- relay_header_t rh;
- crypto_digest_checkpoint_t backup_digest;
- crypto_digest_checkpoint(&backup_digest, digest);
- relay_header_unpack(&rh, cell->payload);
- memcpy(&received_integrity, rh.integrity, 4);
- memset(rh.integrity, 0, 4);
- relay_header_pack(cell->payload, &rh);
- // log_fn(LOG_DEBUG,"Reading digest of %u %u %u %u from relay cell.",
- // received_integrity[0], received_integrity[1],
- // received_integrity[2], received_integrity[3]);
- crypto_digest_add_bytes(digest, (char*) cell->payload, CELL_PAYLOAD_SIZE);
- crypto_digest_get_digest(digest, (char*) &calculated_integrity, 4);
- int rv = 1;
- if (calculated_integrity != received_integrity) {
- // log_fn(LOG_INFO,"Recognized=0 but bad digest. Not recognizing.");
- // (%d vs %d).", received_integrity, calculated_integrity);
- /* restore digest to its old form */
- crypto_digest_restore(digest, &backup_digest);
- /* restore the relay header */
- memcpy(rh.integrity, &received_integrity, 4);
- relay_header_pack(cell->payload, &rh);
- rv = 0;
- }
- memwipe(&backup_digest, 0, sizeof(backup_digest));
- return rv;
- }
- /** Apply <b>cipher</b> to CELL_PAYLOAD_SIZE bytes of <b>in</b>
- * (in place).
- *
- * Note that we use the same operation for encrypting and for decrypting.
- */
- static void
- relay_crypt_one_payload(crypto_cipher_t *cipher, uint8_t *in)
- {
- crypto_cipher_crypt_inplace(cipher, (char*) in, CELL_PAYLOAD_SIZE);
- }
- /** Do the appropriate en/decryptions for <b>cell</b> arriving on
- * <b>circ</b> in direction <b>cell_direction</b>.
- *
- * If cell_direction == CELL_DIRECTION_IN:
- * - If we're at the origin (we're the OP), for hops 1..N,
- * decrypt cell. If recognized, stop.
- * - Else (we're not the OP), encrypt one hop. Cell is not recognized.
- *
- * If cell_direction == CELL_DIRECTION_OUT:
- * - decrypt one hop. Check if recognized.
- *
- * If cell is recognized, set *recognized to 1, and set
- * *layer_hint to the hop that recognized it.
- *
- * Return -1 to indicate that we should mark the circuit for close,
- * else return 0.
- */
- int
- relay_decrypt_cell(circuit_t *circ, cell_t *cell,
- cell_direction_t cell_direction,
- crypt_path_t **layer_hint, char *recognized)
- {
- relay_header_t rh;
- tor_assert(circ);
- tor_assert(cell);
- tor_assert(recognized);
- tor_assert(cell_direction == CELL_DIRECTION_IN ||
- cell_direction == CELL_DIRECTION_OUT);
- if (cell_direction == CELL_DIRECTION_IN) {
- if (CIRCUIT_IS_ORIGIN(circ)) { /* We're at the beginning of the circuit.
- * We'll want to do layered decrypts. */
- crypt_path_t *thishop, *cpath = TO_ORIGIN_CIRCUIT(circ)->cpath;
- thishop = cpath;
- if (thishop->state != CPATH_STATE_OPEN) {
- log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
- "Relay cell before first created cell? Closing.");
- return -1;
- }
- do { /* Remember: cpath is in forward order, that is, first hop first. */
- tor_assert(thishop);
- /* decrypt one layer */
- relay_crypt_one_payload(thishop->b_crypto, cell->payload);
- relay_header_unpack(&rh, cell->payload);
- if (rh.recognized == 0) {
- /* it's possibly recognized. have to check digest to be sure. */
- if (relay_digest_matches(thishop->b_digest, cell)) {
- *recognized = 1;
- *layer_hint = thishop;
- return 0;
- }
- }
- thishop = thishop->next;
- } while (thishop != cpath && thishop->state == CPATH_STATE_OPEN);
- log_fn(LOG_PROTOCOL_WARN, LD_OR,
- "Incoming cell at client not recognized. Closing.");
- return -1;
- } else {
- /* We're in the middle. Encrypt one layer. */
- relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->p_crypto, cell->payload);
- }
- } else /* cell_direction == CELL_DIRECTION_OUT */ {
- /* We're in the middle. Decrypt one layer. */
- relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->n_crypto, cell->payload);
- relay_header_unpack(&rh, cell->payload);
- if (rh.recognized == 0) {
- /* it's possibly recognized. have to check digest to be sure. */
- if (relay_digest_matches(TO_OR_CIRCUIT(circ)->n_digest, cell)) {
- *recognized = 1;
- return 0;
- }
- }
- }
- return 0;
- }
- /**
- * Encrypt a cell <b>cell</b> that we are creating, and sending outbound on
- * <b>circ</b> until the hop corresponding to <b>layer_hint</b>.
- */
- void
- relay_encrypt_cell_outbound(cell_t *cell,
- origin_circuit_t *circ,
- crypt_path_t *layer_hint)
- {
- crypt_path_t *thishop; /* counter for repeated crypts */
- relay_set_digest(layer_hint->f_digest, cell);
- thishop = layer_hint;
- /* moving from farthest to nearest hop */
- do {
- tor_assert(thishop);
- log_debug(LD_OR,"encrypting a layer of the relay cell.");
- relay_crypt_one_payload(thishop->f_crypto, cell->payload);
- thishop = thishop->prev;
- } while (thishop != circ->cpath->prev);
- }
- /**
- * Encrypt a cell <b>cell</b> that we are creating, and sending on
- * <b>circuit</b> to the origin.
- */
- void
- relay_encrypt_cell_inbound(cell_t *cell,
- or_circuit_t *or_circ)
- {
- relay_set_digest(or_circ->p_digest, cell);
- /* encrypt one layer */
- relay_crypt_one_payload(or_circ->p_crypto, cell->payload);
- }
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