break part of circuit.c into relay.c

svn:r1854

1 files changed, 350 insertions, 0 deletions

diff --git a/src/or/relay.c b/src/or/relay.c
new file mode 100644
index 000000000..9f54d2ed1
--- /dev/null
+++ b/src/or/relay.c
@@ -0,0 +1,350 @@
+/* Copyright 2001 Matej Pfajfar, 2001-2004 Roger Dingledine. */
+/* See LICENSE for licensing information */
+/* $Id$ */
+
+/**
+ * \file relay.c
+ * \brief Handle relay cell encryption/decryption.
+ **/
+
+#include "or.h"
+
+static int relay_crypt(circuit_t *circ, cell_t *cell, int cell_direction,
+                crypt_path_t **layer_hint, char *recognized);
+static connection_t *relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction)
+;
+
+/** Stats: how many relay cells have originated at this hop, or have
+ * been relayed onward (not recognized at this hop)?
+ */
+unsigned long stats_n_relay_cells_relayed = 0;
+/** Stats: how many relay cells have been delivered to streams at this
+ * hop?
+ */
+unsigned long stats_n_relay_cells_delivered = 0;
+
+/** Update digest from the payload of cell. Assign integrity part to
+ * cell.
+ */
+static void relay_set_digest(crypto_digest_env_t *digest, cell_t *cell) {
+  char integrity[4];
+  relay_header_t rh;
+
+  crypto_digest_add_bytes(digest, 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_env_t *digest, cell_t *cell) {
+  char received_integrity[4], calculated_integrity[4];
+  relay_header_t rh;
+  crypto_digest_env_t *backup_digest=NULL;
+
+  backup_digest = crypto_digest_dup(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, cell->payload, CELL_PAYLOAD_SIZE);
+  crypto_digest_get_digest(digest, calculated_integrity, 4);
+
+  if(memcmp(received_integrity, calculated_integrity, 4)) {
+//    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_assign(digest, backup_digest);
+    /* restore the relay header */
+    memcpy(rh.integrity, received_integrity, 4);
+    relay_header_pack(cell->payload, &rh);
+    crypto_free_digest_env(backup_digest);
+    return 0;
+  }
+  crypto_free_digest_env(backup_digest);
+  return 1;
+}
+
+/** Apply <b>cipher</b> to CELL_PAYLOAD_SIZE bytes of <b>in</b>
+ * (in place).
+ *
+ * If <b>encrypt_mode</b> is 1 then encrypt, else decrypt.
+ *
+ * Return -1 if the crypto fails, else return 0.
+ */
+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_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 relay encryption");
+    return -1;
+  }
+  memcpy(in,out,CELL_PAYLOAD_SIZE);
+  relay_header_unpack(&rh, in);
+//  log_fn(LOG_DEBUG,"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 and the digest checks out, then find if there's
+ *    a conn that the cell is intended for, and deliver it to·
+ *    connection_edge.
+ *  - Else connection_or_write_cell_to_buf to the conn on the other
+ *    side of the circuit.
+ */
+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;
+
+  tor_assert(cell && circ);
+  tor_assert(cell_direction == CELL_DIRECTION_OUT || cell_direction == CELL_DIRECTION_IN);
+  if (circ->marked_for_close)
+    return 0;
+
+  if(relay_crypt(circ, cell, cell_direction, &layer_hint, &recognized) < 0) {
+    log_fn(LOG_WARN,"relay crypt failed. Dropping connection.");
+    return -1;
+  }
+
+  if(recognized) {
+    conn = relay_lookup_conn(circ, cell, cell_direction);
+    if(cell_direction == CELL_DIRECTION_OUT) {
+      ++stats_n_relay_cells_delivered;
+      log_fn(LOG_DEBUG,"Sending away from origin.");
+      if (connection_edge_process_relay_cell(cell, circ, conn, NULL) < 0) {
+        log_fn(LOG_WARN,"connection_edge_process_relay_cell (away from origin) failed.");
+        return -1;
+      }
+    }
+    if(cell_direction == CELL_DIRECTION_IN) {
+      ++stats_n_relay_cells_delivered;
+      log_fn(LOG_DEBUG,"Sending to origin.");
+      if (connection_edge_process_relay_cell(cell, circ, conn, layer_hint) < 0) {
+        log_fn(LOG_WARN,"connection_edge_process_relay_cell (at origin) failed.");
+        return -1;
+      }
+    }
+    return 0;
+  }
+
+  /* not recognized. pass it on. */
+  if(cell_direction == CELL_DIRECTION_OUT) {
+    cell->circ_id = circ->n_circ_id; /* switch it */
+    conn = circ->n_conn;
+  } else {
+    cell->circ_id = circ->p_circ_id; /* switch it */
+    conn = circ->p_conn;
+  }
+
+  if(!conn) {
+    if (circ->rend_splice && cell_direction == CELL_DIRECTION_OUT) {
+      tor_assert(circ->purpose == CIRCUIT_PURPOSE_REND_ESTABLISHED);
+      tor_assert(circ->rend_splice->purpose == CIRCUIT_PURPOSE_REND_ESTABLISHED);
+      cell->circ_id = circ->rend_splice->p_circ_id;
+      if (circuit_receive_relay_cell(cell, circ->rend_splice, CELL_DIRECTION_IN)<0) {
+        log_fn(LOG_WARN, "Error relaying cell across rendezvous; closing circuits");
+        circuit_mark_for_close(circ); /* XXXX Do this here, or just return -1? */
+        return -1;
+      }
+      return 0;
+    }
+    log_fn(LOG_WARN,"Didn't recognize cell, but circ stops here! Closing circ.");
+    return -1;
+  }
+
+  log_fn(LOG_DEBUG,"Passing on unrecognized cell.");
+  ++stats_n_relay_cells_relayed;
+  connection_or_write_cell_to_buf(cell, conn);
+  return 0;
+}
+
+/** 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.
+ */
+/* wrap this into receive_relay_cell one day */
+static int relay_crypt(circuit_t *circ, cell_t *cell, int cell_direction,
+                       crypt_path_t **layer_hint, char *recognized) {
+  crypt_path_t *thishop;
+  relay_header_t rh;
+
+  tor_assert(circ && cell && 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. */
+      tor_assert(circ->cpath);
+      thishop = circ->cpath;
+      if(thishop->state != CPATH_STATE_OPEN) {
+        log_fn(LOG_WARN,"Relay cell before first created cell? Closing.");
+        return -1;
+      }
+      do { /* Remember: cpath is in forward order, that is, first hop first. */
+        tor_assert(thishop);
+
+        if(relay_crypt_one_payload(thishop->b_crypto, cell->payload, 0) < 0)
+          return -1;
+
+        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 != circ->cpath && thishop->state == CPATH_STATE_OPEN);
+      log_fn(LOG_WARN,"in-cell at OP not recognized. Closing.");
+      return -1;
+    } else { /* we're in the middle. Just one crypt. */
+      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, cell->payload, 0) < 0)
+      return -1;
+
+    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;
+      }
+    }
+  }
+  return 0;
+}
+
+/** Package a relay cell:
+ *  - Encrypt it to the right layer
+ *  - 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 *thishop; /* counter for repeated crypts */
+
+  if(cell_direction == CELL_DIRECTION_OUT) {
+    conn = circ->n_conn;
+    if(!conn) {
+      log_fn(LOG_WARN,"outgoing relay cell has n_conn==NULL. Dropping.");
+      return 0; /* just drop it */
+    }
+    relay_set_digest(layer_hint->f_digest, cell);
+
+    thishop = layer_hint;
+    /* moving from farthest to nearest hop */
+    do {
+      tor_assert(thishop);
+
+      log_fn(LOG_DEBUG,"crypting a layer of the relay cell.");
+      if(relay_crypt_one_payload(thishop->f_crypto, cell->payload, 1) < 0) {
+        return -1;
+      }
+
+      thishop = thishop->prev;
+    } while (thishop != circ->cpath->prev);
+
+  } else { /* incoming cell */
+    conn = circ->p_conn;
+    if(!conn) {
+      log_fn(LOG_WARN,"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;
+}
+
+/** If cell's stream_id matches the stream_id of any conn that's
+ * attached to circ, return that conn, else return NULL.
+ */
+static connection_t *
+relay_lookup_conn(circuit_t *circ, cell_t *cell, int cell_direction)
+{
+  connection_t *tmpconn;
+  relay_header_t rh;
+
+  relay_header_unpack(&rh, cell->payload);
+
+  if(!rh.stream_id)
+    return NULL;
+
+  /* IN or OUT cells could have come from either direction, now
+   * that we allow rendezvous *to* an OP.
+   */
+
+  for(tmpconn = circ->n_streams; tmpconn; tmpconn=tmpconn->next_stream) {
+    if(rh.stream_id == tmpconn->stream_id) {
+      log_fn(LOG_DEBUG,"found conn for stream %d.", rh.stream_id);
+      if(cell_direction == CELL_DIRECTION_OUT ||
+         connection_edge_is_rendezvous_stream(tmpconn))
+        return tmpconn;
+    }
+  }
+  for(tmpconn = circ->p_streams; tmpconn; tmpconn=tmpconn->next_stream) {
+    if(rh.stream_id == tmpconn->stream_id) {
+      log_fn(LOG_DEBUG,"found conn for stream %d.", rh.stream_id);
+      return tmpconn;
+    }
+  }
+  for(tmpconn = circ->resolving_streams; tmpconn; tmpconn=tmpconn->next_stream) {
+    if(rh.stream_id == tmpconn->stream_id) {
+      log_fn(LOG_DEBUG,"found conn for stream %d.", rh.stream_id);
+      return tmpconn;
+    }
+  }
+  return NULL; /* probably a begin relay cell */
+}
+