From 04e8dc90262d9ccc5ef6932cfe86feac24fde997 Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 5 Apr 2004 20:53:50 +0000
Subject: [PATCH] Implement response to RENDEZVOUS2 cell.

svn:r1490
---
 src/or/or.h          |  4 ++--
 src/or/rendclient.c  | 44 ++++++++++++++++++++++++++++++++++++++++----
 src/or/rendservice.c |  2 +-
 3 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/src/or/or.h b/src/or/or.h
index 81f67c9e37..4458550032 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -501,7 +501,7 @@ struct crypt_path_t {
   int deliver_window;
 };
 
-#define DH_KEY_LEN CRYPTO_DH_SIZE
+#define DH_KEY_LEN DH_BYTES
 #define ONIONSKIN_CHALLENGE_LEN (16+DH_KEY_LEN)
 #define ONIONSKIN_REPLY_LEN (DH_KEY_LEN+20)
 #define REND_COOKIE_LEN DIGEST_LEN
@@ -732,7 +732,7 @@ void circuit_n_conn_open(connection_t *or_conn);
 int circuit_send_next_onion_skin(circuit_t *circ);
 int circuit_extend(cell_t *cell, circuit_t *circ);
 #define CPATH_KEY_MATERIAL_LEN (20*2+16*2)
-int circuit_init_cpath_crypto(crypt_path_t *cpath, char *key_data);
+int circuit_init_cpath_crypto(crypt_path_t *cpath, char *key_data,int reverse);
 int circuit_finish_handshake(circuit_t *circ, char *reply);
 int circuit_truncated(circuit_t *circ, crypt_path_t *layer);
 
diff --git a/src/or/rendclient.c b/src/or/rendclient.c
index d02e7521fd..f7b89ca138 100644
--- a/src/or/rendclient.c
+++ b/src/or/rendclient.c
@@ -160,6 +160,10 @@ int
 rend_client_receive_rendezvous(circuit_t *circ, const char *request, int request_len)
 {
   connection_t *apconn;
+  crypt_path_t *hop;
+  char keys[DIGEST_LEN+CPATH_KEY_MATERIAL_LEN];
+  char buf[DIGEST_LEN+9];
+  char expected_digest[DIGEST_LEN];
 
   if(circ->purpose != CIRCUIT_PURPOSE_C_REND_READY ||
      !circ->build_state->pending_final_cpath) {
@@ -168,17 +172,49 @@ rend_client_receive_rendezvous(circuit_t *circ, const char *request, int request
     return -1;
   }
 
-  /* XXX
-   * take 'request' and 'circ->build_state->pending_final_cpath'
-   * and do the right thing to circ
-   */
+  if (request_len != DH_KEY_LEN+DIGEST_LEN) {
+    log_fn(LOG_WARN,"Incorrect length (%d) on RENDEZVOUS2 cell.",request_len);
+    goto err;
+  }
 
+  /* first DH_KEY_LEN bytes are g^y from bob. Finish the dh handshake...*/
+  assert(circ->build_state && circ->build_state->pending_final_cpath);
+  hop = circ->build_state->pending_final_cpath;
+  assert(hop->handshake_state);
+  if (crypto_dh_compute_secret(hop->handshake_state, request, DH_KEY_LEN,
+                               keys, DIGEST_LEN+CPATH_KEY_MATERIAL_LEN)<0) {
+    log_fn(LOG_WARN, "Couldn't complete DH handshake");
+    goto err;
+  }
+  /* ... and set up cpath. */
+  if (circuit_init_cpath_crypto(hop, keys+DIGEST_LEN, 0)<0)
+    goto err;
+
+  /* Check whether the digest is right... */
+  memcpy(buf, keys, DIGEST_LEN);
+  memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
+  if (crypto_digest(buf, DIGEST_LEN+9, expected_digest)) {
+    log_fn(LOG_WARN, "Error computing digest");
+    goto err;
+  }
+  if (memcmp(expected_digest, request+DH_KEY_LEN, DIGEST_LEN)) {
+    log_fn(LOG_WARN, "Incorrect digest of key material");
+    goto err;
+  }
+
+  /* All is well. Extend the circuit. */
   circ->purpose = CIRCUIT_PURPOSE_C_REND_JOINED;
+  onion_append_to_cpath(&circ->cpath, hop);
+  circ->build_state->pending_final_cpath = NULL; /* prevent double-free */
+
   for(apconn = circ->p_streams; apconn; apconn = apconn->next_stream) {
     if(connection_ap_handshake_send_begin(apconn, circ) < 0)
       return -1;
   }
   return 0;
+ err:
+  circuit_mark_for_close(circ);
+  return -1;
 }
 
 /* Find all the apconns in state AP_CONN_STATE_RENDDESC_WAIT that
diff --git a/src/or/rendservice.c b/src/or/rendservice.c
index b4898a3f50..b865d01e9e 100644
--- a/src/or/rendservice.c
+++ b/src/or/rendservice.c
@@ -414,7 +414,7 @@ rend_service_introduce(circuit_t *circuit, const char *request, int request_len)
 
   cpath->handshake_state = dh;
   dh = NULL;
-  if (circuit_init_cpath_crypto(cpath,keys+20)<0)
+  if (circuit_init_cpath_crypto(cpath,keys+20,1)<0)
     goto err;
   memcpy(cpath->handshake_digest, keys, 20);