[or-cvs] back out the insert-padding-if-conflict code
Roger Dingledine
arma at seul.org
Fri Dec 26 06:29:59 UTC 2003
Update of /home/or/cvsroot/src/or
In directory moria.mit.edu:/home2/arma/work/onion/cvs/src/or
Modified Files:
circuit.c
Log Message:
back out the insert-padding-if-conflict code
use recognized + digest instead, just assume it's enough bits
Index: circuit.c
===================================================================
RCS file: /home/or/cvsroot/src/or/circuit.c,v
retrieving revision 1.127
retrieving revision 1.128
diff -u -d -r1.127 -r1.128
--- circuit.c 23 Dec 2003 07:45:31 -0000 1.127
+++ circuit.c 26 Dec 2003 06:29:57 -0000 1.128
@@ -6,7 +6,7 @@
extern or_options_t options; /* command-line and config-file options */
-static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
+static int relay_crypt(circuit_t *circ, cell_t *cell, char cell_direction,
crypt_path_t **layer_hint, char *recognized);
static connection_t *relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction);
static void circuit_free_cpath_node(crypt_path_t *victim);
@@ -324,11 +324,15 @@
}
/* update digest from the payload of cell (with the integrity part set
- * to 0). If the integrity part is valid return 0, else return -1.
+ * 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_check_digest(crypto_digest_env_t *digest, cell_t *cell) {
+static int relay_digest_matches(crypto_digest_env_t *digest, cell_t *cell) {
uint32_t received_integrity, calculated_integrity;
relay_header_t rh;
+ crypto_digest_env_t *backup_digest=NULL;
+
+ backup_digest = crypto_digest_dup(digest);
relay_header_unpack(&rh, cell->payload);
received_integrity = rh.integrity;
@@ -341,11 +345,18 @@
crypto_digest_get_digest(digest, (char *)&calculated_integrity, 4);
if(received_integrity != calculated_integrity) {
- log_fn(LOG_WARN,"Integrity check on cell payload failed. Bug or attack. (%d vs %d).",
+ log_fn(LOG_INFO,"Recognized=0 but bad digest. Not recognizing. (%d vs %d).",
received_integrity, calculated_integrity);
- return -1;
+ /* restore digest to its old form */
+ crypto_digest_assign(digest, backup_digest);
+ /* restore the relay header */
+ rh.integrity = received_integrity;
+ relay_header_pack(cell->payload, &rh);
+ crypto_free_digest_env(backup_digest);
+ return 0;
}
- return 0;
+ crypto_free_digest_env(backup_digest);
+ return 1;
}
static int relay_crypt_one_payload(crypto_cipher_env_t *cipher, char *in,
@@ -354,7 +365,7 @@
relay_header_t rh;
relay_header_unpack(&rh, in);
- log_fn(LOG_INFO,"before crypt: %d",rh.recognized);
+ log_fn(LOG_DEBUG,"before crypt: %d",rh.recognized);
if(( encrypt_mode && crypto_cipher_encrypt(cipher, in, CELL_PAYLOAD_SIZE, out)) ||
(!encrypt_mode && crypto_cipher_decrypt(cipher, in, CELL_PAYLOAD_SIZE, out))) {
log_fn(LOG_WARN,"Error during crypt: %s", crypto_perror());
@@ -362,7 +373,7 @@
}
memcpy(in,out,CELL_PAYLOAD_SIZE);
relay_header_unpack(&rh, in);
- log_fn(LOG_INFO,"after crypt: %d",rh.recognized);
+ log_fn(LOG_DEBUG,"after crypt: %d",rh.recognized);
return 0;
}
@@ -382,8 +393,7 @@
assert(cell && circ);
assert(cell_direction == CELL_DIRECTION_OUT || cell_direction == CELL_DIRECTION_IN);
- if(relay_crypt(circ, cell->payload, cell_direction,
- &layer_hint, &recognized) < 0) {
+ if(relay_crypt(circ, cell, cell_direction, &layer_hint, &recognized) < 0) {
log_fn(LOG_WARN,"relay crypt failed. Dropping connection.");
return -1;
}
@@ -391,10 +401,6 @@
if(recognized) {
conn = relay_lookup_conn(circ, cell, cell_direction);
if(cell_direction == CELL_DIRECTION_OUT) {
- if(relay_check_digest(circ->n_digest, cell) < 0) {
- log_fn(LOG_WARN,"outgoing cell failed integrity check. Closing circ.");
- return -1;
- }
++stats_n_relay_cells_delivered;
log_fn(LOG_DEBUG,"Sending to exit.");
if (connection_edge_process_relay_cell(cell, circ, conn, EDGE_EXIT, NULL) < 0) {
@@ -403,10 +409,6 @@
}
}
if(cell_direction == CELL_DIRECTION_IN) {
- if(relay_check_digest(layer_hint->b_digest, cell) < 0) {
- log_fn(LOG_WARN,"incoming cell failed integrity check. Closing circ.");
- return -1;
- }
++stats_n_relay_cells_delivered;
log_fn(LOG_DEBUG,"Sending to AP.");
if (connection_edge_process_relay_cell(cell, circ, conn, EDGE_AP, layer_hint) < 0) {
@@ -438,12 +440,12 @@
}
/* wrap this into receive_relay_cell one day */
-static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
+static int relay_crypt(circuit_t *circ, cell_t *cell, char cell_direction,
crypt_path_t **layer_hint, char *recognized) {
crypt_path_t *thishop;
relay_header_t rh;
- assert(circ && in && recognized);
+ assert(circ && cell && recognized);
assert(cell_direction == CELL_DIRECTION_IN || cell_direction == CELL_DIRECTION_OUT);
if(cell_direction == CELL_DIRECTION_IN) {
@@ -457,14 +459,17 @@
do { /* Remember: cpath is in forward order, that is, first hop first. */
assert(thishop);
- if(relay_crypt_one_payload(thishop->b_crypto, in, 0) < 0)
+ if(relay_crypt_one_payload(thishop->b_crypto, cell->payload, 0) < 0)
return -1;
- relay_header_unpack(&rh, in);
+ relay_header_unpack(&rh, cell->payload);
if(rh.recognized == 0) {
- *recognized = 1;
- *layer_hint = thishop;
- return 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;
@@ -472,93 +477,25 @@
log_fn(LOG_WARN,"in-cell at OP not recognized. Dropping.");
return 0;
} else { /* we're in the middle. Just one crypt. */
- if(relay_crypt_one_payload(circ->p_crypto, in, 1) < 0)
+ if(relay_crypt_one_payload(circ->p_crypto, cell->payload, 1) < 0)
return -1;
log_fn(LOG_DEBUG,"Skipping recognized check, because we're not the OP.");
}
} else /* cell_direction == CELL_DIRECTION_OUT */ {
/* we're in the middle. Just one crypt. */
- if(relay_crypt_one_payload(circ->n_crypto, in, 0) < 0)
- return -1;
-
- relay_header_unpack(&rh, in);
- if (rh.recognized == 0 ||
- (!circ->n_conn && rh.recognized == 11257)) {
- /* as a special exception, hops at the end of the circuit
- * recognize 01 as well. */
- log_fn(LOG_INFO,"Recognized '%d'", rh.recognized);
- *recognized = 1;
- return 0;
- }
- }
- return 0;
-}
-
-/* Helper function for circuit_package_relay_cell().
- * crypt the cell from layer_hint backward. if there's a conflict,
- * set *conflicthop to the nearest conflict, rewind all the ciphers,
- * and restore the digest state.
- *
- * Conflicthop is set to the node whose cipher is going to output
- * recognized=0. That is, the hop after conflicthop needs to receive
- * the dummy cell.
- */
-static int
-relay_try_all_crypts(cell_t *cell, circuit_t *circ, crypt_path_t *layer_hint,
- uint16_t recognized, crypt_path_t **conflicthop)
-{
- crypt_path_t *thishop; /* counter for repeated crypts */
- relay_header_t rh; /* to set/check 'recognized' */
- crypto_digest_env_t *backup_digest=NULL;
-
- backup_digest = crypto_digest_dup(layer_hint->f_digest);
- relay_header_unpack(&rh, cell->payload);
- rh.recognized = recognized;
- relay_header_pack(cell->payload, &rh);
- relay_set_digest(layer_hint->f_digest, cell);
-
- *conflicthop = NULL;
- thishop = layer_hint;
-
- /* moving from farthest to nearest hop */
- do {
- assert(thishop);
-
- log_fn(LOG_INFO,"crypting a layer of the relay cell.");
- if(relay_crypt_one_payload(thishop->f_crypto, cell->payload, 1) < 0) {
- crypto_free_digest_env(backup_digest);
+ if(relay_crypt_one_payload(circ->n_crypto, cell->payload, 0) < 0)
return -1;
- }
- if(thishop != circ->cpath) {
- /* if it's not the nearest hop, make sure it didn't accidentally
- * encrypt recognized to 00. For the nearest hop it doesn't matter
- * because it will be blindly decrypting whatever it gets. */
- relay_header_unpack(&rh, cell->payload);
-// if(rh.recognized == 0) {
- if(rh.recognized < 10000) {
- log_fn(LOG_INFO,"Found conflict");
- *conflicthop = thishop;
+ 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(circ->n_digest, cell)) {
+ *recognized = 1;
+ return 0;
}
}
- thishop = thishop->prev;
- } while (thishop != circ->cpath->prev);
-
- if(*conflicthop) {
- /* 1. Restore the old digest state */
- crypto_digest_assign(layer_hint->f_digest, backup_digest);
-
- /* 2. Restore old state for the ciphers that changed. */
- thishop = layer_hint;
- do {
- log_fn(LOG_INFO,"Rewinding a cipher layer...");
- crypto_cipher_rewind(thishop->f_crypto, CELL_PAYLOAD_SIZE);
- thishop = thishop->prev;
- } while (thishop != circ->cpath->prev);
}
- /* else no conflict. success. */
- crypto_free_digest_env(backup_digest);
return 0;
}
@@ -575,11 +512,7 @@
crypt_path_t *layer_hint)
{
connection_t *conn; /* where to send the cell */
- crypt_path_t *conflicthop; /* for padding to prematurely recognized hops */
- crypt_path_t *tmpconflicthop;
- relay_header_t rh; /* to make the dummy cell */
- /* backup cell and digest if we need to send a dummy instead */
- cell_t backup_cell;
+ crypt_path_t *thishop; /* counter for repeated crypts */
if(cell_direction == CELL_DIRECTION_OUT) {
conn = circ->n_conn;
@@ -587,60 +520,21 @@
log_fn(LOG_INFO,"outgoing relay cell has n_conn==NULL. Dropping.");
return 0; /* just drop it */
}
+ relay_set_digest(layer_hint->f_digest, cell);
- again:
-
- /* copy cell in case we need to send a dummy relay cell instead */
- memcpy(&backup_cell, cell, sizeof(cell_t));
-
- log_fn(LOG_INFO,"Starting to crypt my relay cell.");
- if(relay_try_all_crypts(cell, circ, layer_hint, 0, &conflicthop) < 0) {
- log_fn(LOG_WARN,"relay_try_deliver_cell (1) failed. Closing.");
- return -1;
- }
- if(conflicthop) {
- log_fn(LOG_WARN,"'recognized' conflict found. Sending padding.");
- /* 1a. build and set_digest a padding cell. */
- cell->circ_id = backup_cell.circ_id;
- cell->command = CELL_RELAY;
- rh.command = RELAY_COMMAND_DROP;
- rh.recognized = rh.stream_id = rh.integrity = rh.length = 0;
- relay_header_pack(cell->payload, &rh);
- memset(cell->payload+RELAY_HEADER_SIZE, 0, RELAY_PAYLOAD_SIZE);
-
- /* if conflicthop is the last hop in the circuit... */
- if(conflicthop == circ->cpath->prev ||
- conflicthop->next->state == CPATH_STATE_CLOSED) {
- log_fn(LOG_WARN,"Got a conflict at the end of the circuit, using recognized=1");
- if(relay_try_all_crypts(cell, circ, conflicthop, 11257, &tmpconflicthop) < 0) {
- log_fn(LOG_WARN,"relay_try_deliver_cell (2) failed. Closing.");
- return -1;
- }
- } else {
- log_fn(LOG_WARN,"Got a conflict inside the circuit, using recognized=0");
- if(relay_try_all_crypts(cell, circ, conflicthop->next, 0, &tmpconflicthop) < 0) {
- log_fn(LOG_WARN,"relay_try_deliver_cell (3) failed. Closing.");
- return -1;
- }
- }
+ thishop = layer_hint;
+ /* moving from farthest to nearest hop */
+ do {
+ assert(thishop);
- if(tmpconflicthop) { /* conflict with this one too?! */
- log_fn(LOG_WARN,"Conflict with sending padding relay cell. Closing.");
+ log_fn(LOG_INFO,"crypting a layer of the relay cell.");
+ if(relay_crypt_one_payload(thishop->f_crypto, cell->payload, 1) < 0) {
return -1;
}
- /* send it. */
- ++stats_n_relay_cells_relayed;
- connection_or_write_cell_to_buf(cell, conn);
- log_fn(LOG_INFO,"Delivered my padding cell.");
-
- /* 2. Restore the original relay cell */
- memcpy(cell, &backup_cell, sizeof(cell_t));
+ thishop = thishop->prev;
+ } while (thishop != circ->cpath->prev);
- /* 3. Try again. */
- goto again;
- }
- /* no conflict, we succeeded. send it and be done. */
} else { /* incoming cell */
conn = circ->p_conn;
if(!conn) {
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