[or-cvs] checkpoint: revamp relay cell packaging and handling
Roger Dingledine
arma at seul.org
Tue Dec 23 07:45:34 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 command.c connection_edge.c connection_or.c or.h
Log Message:
checkpoint: revamp relay cell packaging and handling
include the infrastructure for inserting padding cells when there's
a relay-recognized conflict, but it does not work currently.
Index: circuit.c
===================================================================
RCS file: /home/or/cvsroot/src/or/circuit.c,v
retrieving revision 1.126
retrieving revision 1.127
diff -u -d -r1.126 -r1.127
--- circuit.c 19 Dec 2003 19:55:02 -0000 1.126
+++ circuit.c 23 Dec 2003 07:45:31 -0000 1.127
@@ -311,7 +311,7 @@
}
/* update digest from the payload of cell. assign integrity part to cell. */
-void relay_set_digest(crypto_digest_env_t *digest, cell_t *cell) {
+static void relay_set_digest(crypto_digest_env_t *digest, cell_t *cell) {
uint32_t integrity;
relay_header_t rh;
@@ -326,7 +326,7 @@
/* 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.
*/
-int relay_check_digest(crypto_digest_env_t *digest, cell_t *cell) {
+static int relay_check_digest(crypto_digest_env_t *digest, cell_t *cell) {
uint32_t received_integrity, calculated_integrity;
relay_header_t rh;
@@ -348,16 +348,40 @@
return 0;
}
-int circuit_deliver_relay_cell(cell_t *cell, circuit_t *circ,
- int cell_direction, crypt_path_t *layer_hint) {
+static int relay_crypt_one_payload(crypto_cipher_env_t *cipher, char *in,
+ int encrypt_mode) {
+ char out[CELL_PAYLOAD_SIZE]; /* 'in' must be this size too */
+ relay_header_t rh;
+
+ relay_header_unpack(&rh, in);
+ log_fn(LOG_INFO,"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());
+ return -1;
+ }
+ memcpy(in,out,CELL_PAYLOAD_SIZE);
+ relay_header_unpack(&rh, in);
+ log_fn(LOG_INFO,"after crypt: %d",rh.recognized);
+ return 0;
+}
+
+/*
+receive a relay cell:
+ - crypt it (encrypt APward, decrypt at AP, decrypt exitward)
+ - check if recognized (if exitward)
+ - if recognized, check digest, find right conn, deliver to edge.
+ - else connection_or_write_cell_to_buf to the right conn
+*/
+int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
+ int cell_direction) {
connection_t *conn=NULL;
+ crypt_path_t *layer_hint=NULL;
char recognized=0;
assert(cell && circ);
assert(cell_direction == CELL_DIRECTION_OUT || cell_direction == CELL_DIRECTION_IN);
- log_fn(LOG_DEBUG,"direction %d, stream_id %d before crypt.", cell_direction, *(uint16_t*)(cell->payload+1));/*XXX*/
-
if(relay_crypt(circ, cell->payload, cell_direction,
&layer_hint, &recognized) < 0) {
log_fn(LOG_WARN,"relay crypt failed. Dropping connection.");
@@ -394,15 +418,17 @@
}
/* not recognized. pass it on. */
- if(cell_direction == CELL_DIRECTION_OUT)
+ if(cell_direction == CELL_DIRECTION_OUT) {
+ cell->circ_id = circ->n_circ_id; /* switch it */
conn = circ->n_conn;
- else
+ } else {
+ cell->circ_id = circ->p_circ_id; /* switch it */
conn = circ->p_conn;
+ }
if(!conn) {
- log_fn(LOG_INFO,"Didn't recognize cell (%d), but circ stops here! Dropping.",
- *(int *)(cell->payload+1));
- return 0;
+ log_fn(LOG_WARN,"Didn't recognize cell, but circ stops here! Dropping.");
+ return 0; /* XXX if this warning never triggers, then return -1 */
}
log_fn(LOG_DEBUG,"Passing on unrecognized cell.");
@@ -411,10 +437,10 @@
return 0;
}
+/* wrap this into receive_relay_cell one day */
static int relay_crypt(circuit_t *circ, char *in, char cell_direction,
crypt_path_t **layer_hint, char *recognized) {
crypt_path_t *thishop;
- char out[CELL_PAYLOAD_SIZE]; /* 'in' must be this size too */
relay_header_t rh;
assert(circ && in && recognized);
@@ -431,16 +457,11 @@
do { /* Remember: cpath is in forward order, that is, first hop first. */
assert(thishop);
- log_fn(LOG_DEBUG,"before decrypt: %d",*(uint16_t*)(in+1));
- /* decrypt */
- if(crypto_cipher_decrypt(thishop->b_crypto, in, CELL_PAYLOAD_SIZE, out)) {
- log_fn(LOG_WARN,"Error performing onion decryption: %s", crypto_perror());
+ if(relay_crypt_one_payload(thishop->b_crypto, in, 0) < 0)
return -1;
- }
- memcpy(in,out,CELL_PAYLOAD_SIZE);
- log_fn(LOG_DEBUG,"after decrypt: %d",*(uint16_t*)(in+1));
- if(*(uint16_t*)(in+1) == 0) { /* XXX */
+ relay_header_unpack(&rh, in);
+ if(rh.recognized == 0) {
*recognized = 1;
*layer_hint = thishop;
return 0;
@@ -448,59 +469,196 @@
thishop = thishop->next;
} while(thishop != circ->cpath && thishop->state == CPATH_STATE_OPEN);
- log_fn(LOG_INFO,"in-cell at OP not recognized. Dropping.");
+ log_fn(LOG_WARN,"in-cell at OP not recognized. Dropping.");
return 0;
} else { /* we're in the middle. Just one crypt. */
-
- log_fn(LOG_DEBUG,"before encrypt: %d",*(uint16_t*)(in+1));
- if(crypto_cipher_encrypt(circ->p_crypto, in, CELL_PAYLOAD_SIZE, out)) {
- log_fn(LOG_WARN,"Onion encryption failed for circID %u: %s",
- circ->p_circ_id, crypto_perror());
+ if(relay_crypt_one_payload(circ->p_crypto, in, 1) < 0)
return -1;
- }
- memcpy(in,out,CELL_PAYLOAD_SIZE);
- log_fn(LOG_DEBUG,"after encrypt: %d",*(uint16_t*)(in+1));
-
log_fn(LOG_DEBUG,"Skipping recognized check, because we're not the OP.");
- /* don't check for recognized. only the OP can recognize a stream on the way back. */
}
} else /* cell_direction == CELL_DIRECTION_OUT */ {
- if(circ->cpath) { /* we're at the beginning of the circuit. We'll want to do layered crypts. */
+ /* we're in the middle. Just one crypt. */
- thishop = *layer_hint; /* we already know which layer, from when we package_raw_inbuf'ed */
- /* moving from last to first hop */
- do {
- assert(thishop);
+ if(relay_crypt_one_payload(circ->n_crypto, in, 0) < 0)
+ return -1;
- log_fn(LOG_DEBUG,"before encrypt: %d",*(uint16_t*)(in+1));
- if(crypto_cipher_encrypt(thishop->f_crypto, in, CELL_PAYLOAD_SIZE, out)) {
- log_fn(LOG_WARN,"Error performing encryption: %s", crypto_perror());
+ 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);
+ 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;
+ }
+ }
+ 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;
+}
+
+/*
+package a relay cell:
+ - if from AP: encrypt it to the right conn if 'recognized' doesn't
+ conflict, else insert dummies first as appropriate
+ - if from exit: encrypt it
+ - connection_or_write_cell_to_buf to the right conn
+*/
+int
+circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
+ int cell_direction,
+ 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;
+
+ if(cell_direction == CELL_DIRECTION_OUT) {
+ conn = circ->n_conn;
+ if(!conn) {
+ log_fn(LOG_INFO,"outgoing relay cell has n_conn==NULL. Dropping.");
+ return 0; /* just drop it */
+ }
+
+ 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;
}
- memcpy(in,out,CELL_PAYLOAD_SIZE);
- log_fn(LOG_DEBUG,"after encrypt: %d",*(uint16_t*)(in+1));
-
- thishop = thishop->prev;
- } while(thishop != circ->cpath->prev);
- } else { /* we're in the middle. Just one crypt. */
+ } 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;
+ }
+ }
- if(crypto_cipher_decrypt(circ->n_crypto,in, CELL_PAYLOAD_SIZE, out)) {
- log_fn(LOG_WARN,"Decryption failed for circID %u: %s",
- circ->n_circ_id, crypto_perror());
+ if(tmpconflicthop) { /* conflict with this one too?! */
+ log_fn(LOG_WARN,"Conflict with sending padding relay cell. Closing.");
return -1;
}
- memcpy(in,out,CELL_PAYLOAD_SIZE);
- if(*(uint16_t*)(in+1) == 0) { /* XXX */
- *recognized = 1;
- return 0;
- }
+ /* 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));
+
+ /* 3. Try again. */
+ goto again;
}
+ /* no conflict, we succeeded. send it and be done. */
+ } else { /* incoming cell */
+ conn = circ->p_conn;
+ if(!conn) {
+ log_fn(LOG_INFO,"incoming relay cell has p_conn==NULL. Dropping.");
+ return 0; /* just drop it */
+ }
+ relay_set_digest(circ->p_digest, cell);
+ if(relay_crypt_one_payload(circ->p_crypto, cell->payload, 1) < 0)
+ return -1;
}
+ ++stats_n_relay_cells_relayed;
+ connection_or_write_cell_to_buf(cell, conn);
return 0;
}
-static connection_t *relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction) {
+static connection_t *
+relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction)
+{
connection_t *tmpconn;
relay_header_t rh;
@@ -916,7 +1074,7 @@
* it to a create cell and then send to hop */
if(connection_edge_send_command(NULL, circ, RELAY_COMMAND_EXTEND,
payload, sizeof(payload), hop->prev) < 0)
- return -1; /* circuit is closed */
+ return 0; /* circuit is closed */
hop->state = CPATH_STATE_AWAITING_KEYS;
}
Index: command.c
===================================================================
RCS file: /home/or/cvsroot/src/or/command.c,v
retrieving revision 1.51
retrieving revision 1.52
diff -u -d -r1.51 -r1.52
--- command.c 17 Dec 2003 21:09:31 -0000 1.51
+++ command.c 23 Dec 2003 07:45:31 -0000 1.52
@@ -168,16 +168,14 @@
}
if(cell->circ_id == circ->p_circ_id) { /* it's an outgoing cell */
- cell->circ_id = circ->n_circ_id; /* switch it */
- if(circuit_deliver_relay_cell(cell, circ, CELL_DIRECTION_OUT, conn->cpath_layer) < 0) {
- log_fn(LOG_WARN,"circuit_deliver_relay_cell (forward) failed. Closing.");
+ if(circuit_receive_relay_cell(cell, circ, CELL_DIRECTION_OUT) < 0) {
+ log_fn(LOG_WARN,"circuit_receive_relay_cell (forward) failed. Closing.");
circuit_close(circ);
return;
}
} else { /* it's an ingoing cell */
- cell->circ_id = circ->p_circ_id; /* switch it */
- if(circuit_deliver_relay_cell(cell, circ, CELL_DIRECTION_IN, NULL) < 0) {
- log_fn(LOG_WARN,"circuit_deliver_relay_cell (backward) failed. Closing.");
+ if(circuit_receive_relay_cell(cell, circ, CELL_DIRECTION_IN) < 0) {
+ log_fn(LOG_WARN,"circuit_receive_relay_cell (backward) failed. Closing.");
circuit_close(circ);
return;
}
Index: connection_edge.c
===================================================================
RCS file: /home/or/cvsroot/src/or/connection_edge.c,v
retrieving revision 1.82
retrieving revision 1.83
diff -u -d -r1.82 -r1.83
--- connection_edge.c 19 Dec 2003 21:25:43 -0000 1.82
+++ connection_edge.c 23 Dec 2003 07:45:31 -0000 1.83
@@ -171,16 +171,11 @@
if(payload_len)
memcpy(cell.payload+RELAY_HEADER_SIZE, payload, payload_len);
- if(cell_direction == CELL_DIRECTION_OUT) /* AP */
- relay_set_digest(cpath_layer->f_digest, &cell);
- else /* exit */
- relay_set_digest(circ->p_digest, &cell);
-
log_fn(LOG_DEBUG,"delivering %d cell %s.", relay_command,
cell_direction == CELL_DIRECTION_OUT ? "forward" : "backward");
- if(circuit_deliver_relay_cell(&cell, circ, cell_direction, cpath_layer) < 0) {
- log_fn(LOG_WARN,"circuit_deliver_relay_cell failed. Closing.");
+ if(circuit_package_relay_cell(&cell, circ, cell_direction, cpath_layer) < 0) {
+ log_fn(LOG_WARN,"circuit_package_relay_cell failed. Closing.");
circuit_close(circ);
return -1;
}
@@ -226,6 +221,9 @@
}
switch(rh.command) {
+ case RELAY_COMMAND_DROP:
+ log_fn(LOG_INFO,"Got a relay-level padding cell. Dropping.");
+ return 0;
case RELAY_COMMAND_BEGIN:
if(edge_type == EDGE_AP) {
log_fn(LOG_WARN,"relay begin request unsupported at AP. Dropping.");
Index: connection_or.c
===================================================================
RCS file: /home/or/cvsroot/src/or/connection_or.c,v
retrieving revision 1.81
retrieving revision 1.82
diff -u -d -r1.81 -r1.82
--- connection_or.c 17 Dec 2003 21:09:31 -0000 1.81
+++ connection_or.c 23 Dec 2003 07:45:31 -0000 1.82
@@ -241,13 +241,14 @@
/* ********************************** */
-void connection_or_write_cell_to_buf(const cell_t *cellp, connection_t *conn) {
+void connection_or_write_cell_to_buf(const cell_t *cell, connection_t *conn) {
char networkcell[CELL_NETWORK_SIZE];
char *n = networkcell;
+ assert(cell && conn);
assert(connection_speaks_cells(conn));
- cell_pack(n, cellp);
+ cell_pack(n, cell);
connection_write_to_buf(n, CELL_NETWORK_SIZE, conn);
}
Index: or.h
===================================================================
RCS file: /home/or/cvsroot/src/or/or.h,v
retrieving revision 1.214
retrieving revision 1.215
diff -u -d -r1.214 -r1.215
--- or.h 19 Dec 2003 21:25:44 -0000 1.214
+++ or.h 23 Dec 2003 07:45:31 -0000 1.215
@@ -565,9 +565,9 @@
int circuit_count_building(void);
int circuit_stream_is_being_handled(connection_t *conn);
-void relay_set_digest(crypto_digest_env_t *digest, cell_t *cell);
-int relay_check_digest(crypto_digest_env_t *digest, cell_t *cell);
-int circuit_deliver_relay_cell(cell_t *cell, circuit_t *circ,
+int circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
+ int cell_direction);
+int circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
int cell_direction, crypt_path_t *layer_hint);
void circuit_resume_edge_reading(circuit_t *circ, int edge_type, crypt_path_t *layer_hint);
@@ -695,7 +695,7 @@
int connection_tls_start_handshake(connection_t *conn, int receiving);
int connection_tls_continue_handshake(connection_t *conn);
-void connection_or_write_cell_to_buf(const cell_t *cellp, connection_t *conn);
+void connection_or_write_cell_to_buf(const cell_t *cell, connection_t *conn);
/********************************* cpuworker.c *****************************/
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