1 files changed, 123 insertions, 0 deletions
diff --git a/src/or/onion_fast.c b/src/or/onion_fast.c
new file mode 100644
index 0000000000..c1a05233e0
--- /dev/null
+++ b/src/or/onion_fast.c
@@ -0,0 +1,123 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2012, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file onion_fast.c
+ * \brief Functions implement the CREATE_FAST circuit handshake.
+ **/
+
+#include "or.h"
+#include "onion_fast.h"
+
+/** Release all state held in <b>victim</b>. */
+void
+fast_handshake_state_free(fast_handshake_state_t *victim)
+{
+  if (! victim)
+    return;
+  memwipe(victim, 0, sizeof(fast_handshake_state_t));
+  tor_free(victim);
+}
+
+/** Create the state needed to perform a CREATE_FAST hasnshake. Return 0
+ * on success, -1 on failure. */
+int
+fast_onionskin_create(fast_handshake_state_t **handshake_state_out,
+                      uint8_t *handshake_out)
+{
+  fast_handshake_state_t *s;
+  *handshake_state_out = s = tor_malloc(sizeof(fast_handshake_state_t));
+  if (crypto_rand((char*)s->state, sizeof(s->state)) < 0) {
+    tor_free(s);
+    return -1;
+  }
+  memcpy(handshake_out, s->state, DIGEST_LEN);
+  return 0;
+}
+
+/** Implement the server side of the CREATE_FAST abbreviated handshake.  The
+ * client has provided DIGEST_LEN key bytes in <b>key_in</b> ("x").  We
+ * generate a reply of DIGEST_LEN*2 bytes in <b>key_out</b>, consisting of a
+ * new random "y", followed by H(x|y) to check for correctness.  We set
+ * <b>key_out_len</b> bytes of key material in <b>key_out</b>.
+ * Return 0 on success, &lt;0 on failure.
+ **/
+int
+fast_server_handshake(const uint8_t *key_in, /* DIGEST_LEN bytes */
+                      uint8_t *handshake_reply_out, /* DIGEST_LEN*2 bytes */
+                      uint8_t *key_out,
+                      size_t key_out_len)
+{
+  uint8_t tmp[DIGEST_LEN+DIGEST_LEN];
+  uint8_t *out = NULL;
+  size_t out_len;
+  int r = -1;
+
+  if (crypto_rand((char*)handshake_reply_out, DIGEST_LEN)<0)
+    return -1;
+
+  memcpy(tmp, key_in, DIGEST_LEN);
+  memcpy(tmp+DIGEST_LEN, handshake_reply_out, DIGEST_LEN);
+  out_len = key_out_len+DIGEST_LEN;
+  out = tor_malloc(out_len);
+  if (crypto_expand_key_material_TAP(tmp, sizeof(tmp), out, out_len)) {
+    goto done;
+  }
+  memcpy(handshake_reply_out+DIGEST_LEN, out, DIGEST_LEN);
+  memcpy(key_out, out+DIGEST_LEN, key_out_len);
+  r = 0;
+ done:
+  memwipe(tmp, 0, sizeof(tmp));
+  memwipe(out, 0, out_len);
+  tor_free(out);
+  return r;
+}
+
+/** Implement the second half of the client side of the CREATE_FAST handshake.
+ * We sent the server <b>handshake_state</b> ("x") already, and the server
+ * told us <b>handshake_reply_out</b> (y|H(x|y)).  Make sure that the hash is
+ * correct, and generate key material in <b>key_out</b>.  Return 0 on success,
+ * true on failure.
+ *
+ * NOTE: The "CREATE_FAST" handshake path is distinguishable from regular
+ * "onionskin" handshakes, and is not secure if an adversary can see or modify
+ * the messages.  Therefore, it should only be used by clients, and only as
+ * the first hop of a circuit (since the first hop is already authenticated
+ * and protected by TLS).
+ */
+int
+fast_client_handshake(const fast_handshake_state_t *handshake_state,
+                      const uint8_t *handshake_reply_out,/*DIGEST_LEN*2 bytes*/
+                      uint8_t *key_out,
+                      size_t key_out_len)
+{
+  uint8_t tmp[DIGEST_LEN+DIGEST_LEN];
+  uint8_t *out;
+  size_t out_len;
+  int r = -1;
+
+  memcpy(tmp, handshake_state->state, DIGEST_LEN);
+  memcpy(tmp+DIGEST_LEN, handshake_reply_out, DIGEST_LEN);
+  out_len = key_out_len+DIGEST_LEN;
+  out = tor_malloc(out_len);
+  if (crypto_expand_key_material_TAP(tmp, sizeof(tmp), out, out_len)) {
+    goto done;
+  }
+  if (tor_memneq(out, handshake_reply_out+DIGEST_LEN, DIGEST_LEN)) {
+    /* H(K) does *not* match. Something fishy. */
+    log_warn(LD_PROTOCOL,"Digest DOES NOT MATCH on fast handshake. "
+             "Bug or attack.");
+    goto done;
+  }
+  memcpy(key_out, out+DIGEST_LEN, key_out_len);
+  r = 0;
+ done:
+  memwipe(tmp, 0, sizeof(tmp));
+  memwipe(out, 0, out_len);
+  tor_free(out);
+  return r;
+}
+