mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-27 22:03:31 +01:00
back out the insert-padding-if-conflict code
use recognized + digest instead, just assume it's enough bits svn:r959
This commit is contained in:
Roger Dingledine
parent
43fcb70bad
commit
71739b486a
192
src/or/circuit.c
192
src/or/circuit.c
@ -6,7 +6,7 @@
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extern or_options_t options; /* command-line and config-file options */
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static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
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static int relay_crypt(circuit_t *circ, cell_t *cell, char cell_direction,
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crypt_path_t **layer_hint, char *recognized);
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static connection_t *relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction);
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static void circuit_free_cpath_node(crypt_path_t *victim);
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@ -324,11 +324,15 @@ static void relay_set_digest(crypto_digest_env_t *digest, cell_t *cell) {
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}
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/* update digest from the payload of cell (with the integrity part set
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* to 0). If the integrity part is valid return 0, else return -1.
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* to 0). If the integrity part is valid return 1, else restore digest
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* and cell to their original state and return 0.
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*/
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static int relay_check_digest(crypto_digest_env_t *digest, cell_t *cell) {
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static int relay_digest_matches(crypto_digest_env_t *digest, cell_t *cell) {
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uint32_t received_integrity, calculated_integrity;
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relay_header_t rh;
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crypto_digest_env_t *backup_digest=NULL;
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backup_digest = crypto_digest_dup(digest);
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relay_header_unpack(&rh, cell->payload);
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received_integrity = rh.integrity;
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@ -341,11 +345,18 @@ static int relay_check_digest(crypto_digest_env_t *digest, cell_t *cell) {
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crypto_digest_get_digest(digest, (char *)&calculated_integrity, 4);
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if(received_integrity != calculated_integrity) {
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log_fn(LOG_WARN,"Integrity check on cell payload failed. Bug or attack. (%d vs %d).",
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log_fn(LOG_INFO,"Recognized=0 but bad digest. Not recognizing. (%d vs %d).",
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received_integrity, calculated_integrity);
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return -1;
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}
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/* restore digest to its old form */
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crypto_digest_assign(digest, backup_digest);
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/* restore the relay header */
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rh.integrity = received_integrity;
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relay_header_pack(cell->payload, &rh);
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crypto_free_digest_env(backup_digest);
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return 0;
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}
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crypto_free_digest_env(backup_digest);
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return 1;
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}
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static int relay_crypt_one_payload(crypto_cipher_env_t *cipher, char *in,
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@ -354,7 +365,7 @@ static int relay_crypt_one_payload(crypto_cipher_env_t *cipher, char *in,
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relay_header_t rh;
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relay_header_unpack(&rh, in);
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log_fn(LOG_INFO,"before crypt: %d",rh.recognized);
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log_fn(LOG_DEBUG,"before crypt: %d",rh.recognized);
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if(( encrypt_mode && crypto_cipher_encrypt(cipher, in, CELL_PAYLOAD_SIZE, out)) ||
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(!encrypt_mode && crypto_cipher_decrypt(cipher, in, CELL_PAYLOAD_SIZE, out))) {
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log_fn(LOG_WARN,"Error during crypt: %s", crypto_perror());
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@ -362,7 +373,7 @@ static int relay_crypt_one_payload(crypto_cipher_env_t *cipher, char *in,
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}
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memcpy(in,out,CELL_PAYLOAD_SIZE);
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relay_header_unpack(&rh, in);
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log_fn(LOG_INFO,"after crypt: %d",rh.recognized);
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log_fn(LOG_DEBUG,"after crypt: %d",rh.recognized);
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return 0;
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}
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@ -382,8 +393,7 @@ int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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assert(cell && circ);
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assert(cell_direction == CELL_DIRECTION_OUT || cell_direction == CELL_DIRECTION_IN);
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if(relay_crypt(circ, cell->payload, cell_direction,
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&layer_hint, &recognized) < 0) {
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if(relay_crypt(circ, cell, cell_direction, &layer_hint, &recognized) < 0) {
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log_fn(LOG_WARN,"relay crypt failed. Dropping connection.");
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return -1;
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}
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@ -391,10 +401,6 @@ int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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if(recognized) {
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conn = relay_lookup_conn(circ, cell, cell_direction);
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if(cell_direction == CELL_DIRECTION_OUT) {
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if(relay_check_digest(circ->n_digest, cell) < 0) {
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log_fn(LOG_WARN,"outgoing cell failed integrity check. Closing circ.");
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return -1;
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}
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++stats_n_relay_cells_delivered;
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log_fn(LOG_DEBUG,"Sending to exit.");
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if (connection_edge_process_relay_cell(cell, circ, conn, EDGE_EXIT, NULL) < 0) {
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@ -403,10 +409,6 @@ int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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}
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}
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if(cell_direction == CELL_DIRECTION_IN) {
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if(relay_check_digest(layer_hint->b_digest, cell) < 0) {
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log_fn(LOG_WARN,"incoming cell failed integrity check. Closing circ.");
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return -1;
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}
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++stats_n_relay_cells_delivered;
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log_fn(LOG_DEBUG,"Sending to AP.");
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if (connection_edge_process_relay_cell(cell, circ, conn, EDGE_AP, layer_hint) < 0) {
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@ -438,12 +440,12 @@ int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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}
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/* wrap this into receive_relay_cell one day */
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static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
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static int relay_crypt(circuit_t *circ, cell_t *cell, char cell_direction,
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crypt_path_t **layer_hint, char *recognized) {
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crypt_path_t *thishop;
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relay_header_t rh;
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assert(circ && in && recognized);
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assert(circ && cell && recognized);
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assert(cell_direction == CELL_DIRECTION_IN || cell_direction == CELL_DIRECTION_OUT);
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if(cell_direction == CELL_DIRECTION_IN) {
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@ -457,108 +459,43 @@ static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
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do { /* Remember: cpath is in forward order, that is, first hop first. */
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assert(thishop);
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if(relay_crypt_one_payload(thishop->b_crypto, in, 0) < 0)
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if(relay_crypt_one_payload(thishop->b_crypto, cell->payload, 0) < 0)
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return -1;
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relay_header_unpack(&rh, in);
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relay_header_unpack(&rh, cell->payload);
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if(rh.recognized == 0) {
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/* it's possibly recognized. have to check digest to be sure. */
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if(relay_digest_matches(thishop->b_digest, cell)) {
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*recognized = 1;
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*layer_hint = thishop;
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return 0;
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}
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}
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thishop = thishop->next;
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} while(thishop != circ->cpath && thishop->state == CPATH_STATE_OPEN);
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log_fn(LOG_WARN,"in-cell at OP not recognized. Dropping.");
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return 0;
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} else { /* we're in the middle. Just one crypt. */
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if(relay_crypt_one_payload(circ->p_crypto, in, 1) < 0)
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if(relay_crypt_one_payload(circ->p_crypto, cell->payload, 1) < 0)
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return -1;
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log_fn(LOG_DEBUG,"Skipping recognized check, because we're not the OP.");
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}
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} else /* cell_direction == CELL_DIRECTION_OUT */ {
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/* we're in the middle. Just one crypt. */
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if(relay_crypt_one_payload(circ->n_crypto, in, 0) < 0)
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if(relay_crypt_one_payload(circ->n_crypto, cell->payload, 0) < 0)
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return -1;
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relay_header_unpack(&rh, in);
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if (rh.recognized == 0 ||
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(!circ->n_conn && rh.recognized == 11257)) {
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/* as a special exception, hops at the end of the circuit
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* recognize 01 as well. */
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log_fn(LOG_INFO,"Recognized '%d'", rh.recognized);
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relay_header_unpack(&rh, cell->payload);
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if (rh.recognized == 0) {
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/* it's possibly recognized. have to check digest to be sure. */
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if(relay_digest_matches(circ->n_digest, cell)) {
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*recognized = 1;
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return 0;
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}
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}
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return 0;
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}
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/* Helper function for circuit_package_relay_cell().
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* crypt the cell from layer_hint backward. if there's a conflict,
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* set *conflicthop to the nearest conflict, rewind all the ciphers,
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* and restore the digest state.
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*
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* Conflicthop is set to the node whose cipher is going to output
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* recognized=0. That is, the hop after conflicthop needs to receive
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* the dummy cell.
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*/
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static int
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relay_try_all_crypts(cell_t *cell, circuit_t *circ, crypt_path_t *layer_hint,
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uint16_t recognized, crypt_path_t **conflicthop)
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{
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crypt_path_t *thishop; /* counter for repeated crypts */
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relay_header_t rh; /* to set/check 'recognized' */
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crypto_digest_env_t *backup_digest=NULL;
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backup_digest = crypto_digest_dup(layer_hint->f_digest);
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relay_header_unpack(&rh, cell->payload);
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rh.recognized = recognized;
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relay_header_pack(cell->payload, &rh);
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relay_set_digest(layer_hint->f_digest, cell);
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*conflicthop = NULL;
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thishop = layer_hint;
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/* moving from farthest to nearest hop */
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do {
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assert(thishop);
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log_fn(LOG_INFO,"crypting a layer of the relay cell.");
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if(relay_crypt_one_payload(thishop->f_crypto, cell->payload, 1) < 0) {
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crypto_free_digest_env(backup_digest);
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return -1;
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}
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if(thishop != circ->cpath) {
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/* if it's not the nearest hop, make sure it didn't accidentally
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* encrypt recognized to 00. For the nearest hop it doesn't matter
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* because it will be blindly decrypting whatever it gets. */
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relay_header_unpack(&rh, cell->payload);
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// if(rh.recognized == 0) {
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if(rh.recognized < 10000) {
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log_fn(LOG_INFO,"Found conflict");
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*conflicthop = thishop;
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}
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}
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thishop = thishop->prev;
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} while (thishop != circ->cpath->prev);
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if(*conflicthop) {
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/* 1. Restore the old digest state */
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crypto_digest_assign(layer_hint->f_digest, backup_digest);
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/* 2. Restore old state for the ciphers that changed. */
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thishop = layer_hint;
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do {
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log_fn(LOG_INFO,"Rewinding a cipher layer...");
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crypto_cipher_rewind(thishop->f_crypto, CELL_PAYLOAD_SIZE);
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thishop = thishop->prev;
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} while (thishop != circ->cpath->prev);
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}
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/* else no conflict. success. */
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crypto_free_digest_env(backup_digest);
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return 0;
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}
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@ -575,11 +512,7 @@ circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
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crypt_path_t *layer_hint)
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{
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connection_t *conn; /* where to send the cell */
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crypt_path_t *conflicthop; /* for padding to prematurely recognized hops */
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crypt_path_t *tmpconflicthop;
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relay_header_t rh; /* to make the dummy cell */
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/* backup cell and digest if we need to send a dummy instead */
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cell_t backup_cell;
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crypt_path_t *thishop; /* counter for repeated crypts */
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if(cell_direction == CELL_DIRECTION_OUT) {
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conn = circ->n_conn;
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@ -587,60 +520,21 @@ circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
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log_fn(LOG_INFO,"outgoing relay cell has n_conn==NULL. Dropping.");
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return 0; /* just drop it */
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}
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relay_set_digest(layer_hint->f_digest, cell);
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again:
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thishop = layer_hint;
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/* moving from farthest to nearest hop */
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do {
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assert(thishop);
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/* copy cell in case we need to send a dummy relay cell instead */
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memcpy(&backup_cell, cell, sizeof(cell_t));
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log_fn(LOG_INFO,"Starting to crypt my relay cell.");
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if(relay_try_all_crypts(cell, circ, layer_hint, 0, &conflicthop) < 0) {
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log_fn(LOG_WARN,"relay_try_deliver_cell (1) failed. Closing.");
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return -1;
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}
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if(conflicthop) {
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log_fn(LOG_WARN,"'recognized' conflict found. Sending padding.");
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/* 1a. build and set_digest a padding cell. */
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cell->circ_id = backup_cell.circ_id;
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cell->command = CELL_RELAY;
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rh.command = RELAY_COMMAND_DROP;
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rh.recognized = rh.stream_id = rh.integrity = rh.length = 0;
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relay_header_pack(cell->payload, &rh);
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memset(cell->payload+RELAY_HEADER_SIZE, 0, RELAY_PAYLOAD_SIZE);
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/* if conflicthop is the last hop in the circuit... */
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if(conflicthop == circ->cpath->prev ||
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conflicthop->next->state == CPATH_STATE_CLOSED) {
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log_fn(LOG_WARN,"Got a conflict at the end of the circuit, using recognized=1");
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if(relay_try_all_crypts(cell, circ, conflicthop, 11257, &tmpconflicthop) < 0) {
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log_fn(LOG_WARN,"relay_try_deliver_cell (2) failed. Closing.");
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return -1;
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}
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} else {
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log_fn(LOG_WARN,"Got a conflict inside the circuit, using recognized=0");
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if(relay_try_all_crypts(cell, circ, conflicthop->next, 0, &tmpconflicthop) < 0) {
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log_fn(LOG_WARN,"relay_try_deliver_cell (3) failed. Closing.");
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return -1;
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}
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}
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if(tmpconflicthop) { /* conflict with this one too?! */
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log_fn(LOG_WARN,"Conflict with sending padding relay cell. Closing.");
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log_fn(LOG_INFO,"crypting a layer of the relay cell.");
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if(relay_crypt_one_payload(thishop->f_crypto, cell->payload, 1) < 0) {
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return -1;
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}
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/* send it. */
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++stats_n_relay_cells_relayed;
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connection_or_write_cell_to_buf(cell, conn);
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log_fn(LOG_INFO,"Delivered my padding cell.");
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thishop = thishop->prev;
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} while (thishop != circ->cpath->prev);
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/* 2. Restore the original relay cell */
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memcpy(cell, &backup_cell, sizeof(cell_t));
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/* 3. Try again. */
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goto again;
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}
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/* no conflict, we succeeded. send it and be done. */
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} else { /* incoming cell */
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conn = circ->p_conn;
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if(!conn) {
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