Extract the cryptographic parts of crypt_path_t and or_circuit_t.

Additionally, this change extracts the functions that created and
freed these elements.

These structures had common "forward&reverse stream&digest"
elements, but they were initialized and freed through cpath objects,
and different parts of the code depended on them.  Now all that code
is extacted, and kept in relay_crypto.c

8 files changed, 177 insertions, 136 deletions

diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index b3b543348c..82c3699c4b 100644
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -56,6 +56,7 @@
 #include "onion_fast.h"
 #include "policies.h"
 #include "relay.h"
+#include "relay_crypto.h"
 #include "rendcommon.h"
 #include "rephist.h"
 #include "router.h"
@@ -1336,69 +1337,10 @@ circuit_init_cpath_crypto(crypt_path_t *cpath,
                           const char *key_data, size_t key_data_len,
                           int reverse, int is_hs_v3)
 {
-  crypto_digest_t *tmp_digest;
-  crypto_cipher_t *tmp_crypto;
-  size_t digest_len = 0;
-  size_t cipher_key_len = 0;
 
   tor_assert(cpath);
-  tor_assert(key_data);
-  tor_assert(!(cpath->f_crypto || cpath->b_crypto ||
-             cpath->f_digest || cpath->b_digest));
-
-  /* Basic key size validation */
-  if (is_hs_v3 && BUG(key_data_len != HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN)) {
-    return -1;
-  } else if (!is_hs_v3 && BUG(key_data_len != CPATH_KEY_MATERIAL_LEN)) {
-    return -1;
-  }
-
-  /* If we are using this cpath for next gen onion services use SHA3-256,
-     otherwise use good ol' SHA1 */
-  if (is_hs_v3) {
-    digest_len = DIGEST256_LEN;
-    cipher_key_len = CIPHER256_KEY_LEN;
-    cpath->f_digest = crypto_digest256_new(DIGEST_SHA3_256);
-    cpath->b_digest = crypto_digest256_new(DIGEST_SHA3_256);
-  } else {
-    digest_len = DIGEST_LEN;
-    cipher_key_len = CIPHER_KEY_LEN;
-    cpath->f_digest = crypto_digest_new();
-    cpath->b_digest = crypto_digest_new();
-  }
-
-  tor_assert(digest_len != 0);
-  tor_assert(cipher_key_len != 0);
-  const int cipher_key_bits = (int) cipher_key_len * 8;
-
-  crypto_digest_add_bytes(cpath->f_digest, key_data, digest_len);
-  crypto_digest_add_bytes(cpath->b_digest, key_data+digest_len, digest_len);
-
-  cpath->f_crypto = crypto_cipher_new_with_bits(key_data+(2*digest_len),
-                                                cipher_key_bits);
-  if (!cpath->f_crypto) {
-    log_warn(LD_BUG,"Forward cipher initialization failed.");
-    return -1;
-  }
-
-  cpath->b_crypto = crypto_cipher_new_with_bits(
-                                        key_data+(2*digest_len)+cipher_key_len,
-                                        cipher_key_bits);
-  if (!cpath->b_crypto) {
-    log_warn(LD_BUG,"Backward cipher initialization failed.");
-    return -1;
-  }
-
-  if (reverse) {
-    tmp_digest = cpath->f_digest;
-    cpath->f_digest = cpath->b_digest;
-    cpath->b_digest = tmp_digest;
-    tmp_crypto = cpath->f_crypto;
-    cpath->f_crypto = cpath->b_crypto;
-    cpath->b_crypto = tmp_crypto;
-  }
-
-  return 0;
+  return relay_crypto_init(&cpath->crypto, key_data, key_data_len, reverse,
+                           is_hs_v3);
 }
 
 /** A "created" cell <b>reply</b> came back to us on circuit <b>circ</b>.
@@ -1521,7 +1463,6 @@ onionskin_answer(or_circuit_t *circ,
                  const uint8_t *rend_circ_nonce)
 {
   cell_t cell;
-  crypt_path_t *tmp_cpath;
 
   tor_assert(keys_len == CPATH_KEY_MATERIAL_LEN);
 
@@ -1532,25 +1473,15 @@ onionskin_answer(or_circuit_t *circ,
   }
   cell.circ_id = circ->p_circ_id;
 
-  tmp_cpath = tor_malloc_zero(sizeof(crypt_path_t));
-  tmp_cpath->magic = CRYPT_PATH_MAGIC;
-
   circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN);
 
   log_debug(LD_CIRC,"init digest forward 0x%.8x, backward 0x%.8x.",
             (unsigned int)get_uint32(keys),
             (unsigned int)get_uint32(keys+20));
-  if (circuit_init_cpath_crypto(tmp_cpath, keys, keys_len, 0, 0)<0) {
+  if (relay_crypto_init(&circ->crypto, keys, keys_len, 0, 0)<0) {
     log_warn(LD_BUG,"Circuit initialization failed");
-    tor_free(tmp_cpath);
     return -1;
   }
-  circ->n_digest = tmp_cpath->f_digest;
-  circ->n_crypto = tmp_cpath->f_crypto;
-  circ->p_digest = tmp_cpath->b_digest;
-  circ->p_crypto = tmp_cpath->b_crypto;
-  tmp_cpath->magic = 0;
-  tor_free(tmp_cpath);
 
   memcpy(circ->rend_circ_nonce, rend_circ_nonce, DIGEST_LEN);
 
diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c
index 29ad9a8ee5..2373bfb842 100644
--- a/src/or/circuitlist.c
+++ b/src/or/circuitlist.c
@@ -76,6 +76,7 @@
 #include "onion_fast.h"
 #include "policies.h"
 #include "relay.h"
+#include "relay_crypto.h"
 #include "rendclient.h"
 #include "rendcommon.h"
 #include "rephist.h"
@@ -1084,10 +1085,7 @@ circuit_free_(circuit_t *circ)
 
     should_free = (ocirc->workqueue_entry == NULL);
 
-    crypto_cipher_free(ocirc->p_crypto);
-    crypto_digest_free(ocirc->p_digest);
-    crypto_cipher_free(ocirc->n_crypto);
-    crypto_digest_free(ocirc->n_digest);
+    relay_crypto_clear(&ocirc->crypto);
 
     if (ocirc->rend_splice) {
       or_circuit_t *other = ocirc->rend_splice;
@@ -1227,10 +1225,7 @@ circuit_free_cpath_node(crypt_path_t *victim)
   if (!victim)
     return;
 
-  crypto_cipher_free(victim->f_crypto);
-  crypto_cipher_free(victim->b_crypto);
-  crypto_digest_free(victim->f_digest);
-  crypto_digest_free(victim->b_digest);
+  relay_crypto_clear(&victim->crypto);
   onion_handshake_state_release(&victim->handshake_state);
   crypto_dh_free(victim->rend_dh_handshake_state);
   extend_info_free(victim->extend_info);
@@ -2588,8 +2583,7 @@ assert_cpath_layer_ok(const crypt_path_t *cp)
   switch (cp->state)
     {
     case CPATH_STATE_OPEN:
-      tor_assert(cp->f_crypto);
-      tor_assert(cp->b_crypto);
+      relay_crypto_assert_ok(&cp->crypto);
       /* fall through */
     case CPATH_STATE_CLOSED:
       /*XXXX Assert that there's no handshake_state either. */
@@ -2679,10 +2673,7 @@ assert_circuit_ok,(const circuit_t *c))
       c->state == CIRCUIT_STATE_GUARD_WAIT) {
     tor_assert(!c->n_chan_create_cell);
     if (or_circ) {
-      tor_assert(or_circ->n_crypto);
-      tor_assert(or_circ->p_crypto);
-      tor_assert(or_circ->n_digest);
-      tor_assert(or_circ->p_digest);
+      relay_crypto_assert_ok(&or_circ->crypto);
     }
   }
   if (c->state == CIRCUIT_STATE_CHAN_WAIT && !c->marked_for_close) {
diff --git a/src/or/or.h b/src/or/or.h
index 045cdd9e14..3e61e1bef6 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -2899,11 +2899,7 @@ typedef struct {
   } u;
 } onion_handshake_state_t;
 
-/** Holds accounting information for a single step in the layered encryption
- * performed by a circuit.  Used only at the client edge of a circuit. */
-typedef struct crypt_path_t {
-  uint32_t magic;
-
+typedef struct relay_crypto_t {
   /* crypto environments */
   /** Encryption key and counter for cells heading towards the OR at this
    * step. */
@@ -2917,6 +2913,17 @@ typedef struct crypt_path_t {
   /** Digest state for cells heading away from the OR at this step. */
   crypto_digest_t *b_digest;
 
+} relay_crypto_t;
+
+/** Holds accounting information for a single step in the layered encryption
+ * performed by a circuit.  Used only at the client edge of a circuit. */
+typedef struct crypt_path_t {
+  uint32_t magic;
+
+  /** Cryptographic state used for encrypting and authenticating relay
+   * cells to and from this hop. */
+  relay_crypto_t crypto;
+
   /** Current state of the handshake as performed with the OR at this
    * step. */
   onion_handshake_state_t handshake_state;
@@ -3482,21 +3489,10 @@ typedef struct or_circuit_t {
   /** Linked list of Exit streams associated with this circuit that are
    * still being resolved. */
   edge_connection_t *resolving_streams;
-  /** The cipher used by intermediate hops for cells heading toward the
-   * OP. */
-  crypto_cipher_t *p_crypto;
-  /** The cipher used by intermediate hops for cells heading away from
-   * the OP. */
-  crypto_cipher_t *n_crypto;
-
-  /** The integrity-checking digest used by intermediate hops, for
-   * cells packaged here and heading towards the OP.
-   */
-  crypto_digest_t *p_digest;
-  /** The integrity-checking digest used by intermediate hops, for
-   * cells packaged at the OP and arriving here.
-   */
-  crypto_digest_t *n_digest;
+
+  /** Cryptographic state used for encrypting and authenticating relay
+   * cells to and from this hop. */
+  relay_crypto_t crypto;
 
   /** Points to spliced circuit if purpose is REND_ESTABLISHED, and circuit
    * is not marked for close. */
diff --git a/src/or/relay_crypto.c b/src/or/relay_crypto.c
index e0992a3014..9d61ecd424 100644
--- a/src/or/relay_crypto.c
+++ b/src/or/relay_crypto.c
@@ -6,6 +6,7 @@
 
 #include "or.h"
 #include "config.h"
+#include "hs_ntor.h" // for HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN
 #include "relay_crypto.h"
 #include "relay.h"
 
@@ -126,12 +127,12 @@ relay_decrypt_cell(circuit_t *circ, cell_t *cell,
         tor_assert(thishop);
 
         /* decrypt one layer */
-        relay_crypt_one_payload(thishop->b_crypto, cell->payload);
+        relay_crypt_one_payload(thishop->crypto.b_crypto, cell->payload);
 
         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)) {
+          if (relay_digest_matches(thishop->crypto.b_digest, cell)) {
             *recognized = 1;
             *layer_hint = thishop;
             return 0;
@@ -144,18 +145,20 @@ relay_decrypt_cell(circuit_t *circ, cell_t *cell,
              "Incoming cell at client not recognized. Closing.");
       return -1;
     } else {
+      relay_crypto_t *crypto = &TO_OR_CIRCUIT(circ)->crypto;
       /* We're in the middle. Encrypt one layer. */
-      relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->p_crypto, cell->payload);
+      relay_crypt_one_payload(crypto->b_crypto, cell->payload);
     }
   } else /* cell_direction == CELL_DIRECTION_OUT */ {
     /* We're in the middle. Decrypt one layer. */
+    relay_crypto_t *crypto = &TO_OR_CIRCUIT(circ)->crypto;
 
-    relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->n_crypto, cell->payload);
+    relay_crypt_one_payload(crypto->f_crypto, cell->payload);
 
     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(TO_OR_CIRCUIT(circ)->n_digest, cell)) {
+      if (relay_digest_matches(crypto->f_digest, cell)) {
         *recognized = 1;
         return 0;
       }
@@ -174,14 +177,14 @@ relay_encrypt_cell_outbound(cell_t *cell,
                             crypt_path_t *layer_hint)
 {
   crypt_path_t *thishop; /* counter for repeated crypts */
-  relay_set_digest(layer_hint->f_digest, cell);
+  relay_set_digest(layer_hint->crypto.f_digest, cell);
 
   thishop = layer_hint;
   /* moving from farthest to nearest hop */
   do {
     tor_assert(thishop);
     log_debug(LD_OR,"encrypting a layer of the relay cell.");
-    relay_crypt_one_payload(thishop->f_crypto, cell->payload);
+    relay_crypt_one_payload(thishop->crypto.f_crypto, cell->payload);
 
     thishop = thishop->prev;
   } while (thishop != circ->cpath->prev);
@@ -195,8 +198,123 @@ void
 relay_encrypt_cell_inbound(cell_t *cell,
                            or_circuit_t *or_circ)
 {
-  relay_set_digest(or_circ->p_digest, cell);
+  relay_set_digest(or_circ->crypto.b_digest, cell);
   /* encrypt one layer */
-  relay_crypt_one_payload(or_circ->p_crypto, cell->payload);
+  relay_crypt_one_payload(or_circ->crypto.b_crypto, cell->payload);
+}
+
+/**
+ * Release all storage held inside <b>crypto</b>, but do not free
+ * <b>crypto</b> itself: it lives inside another object.
+ */
+void
+relay_crypto_clear(relay_crypto_t *crypto)
+{
+  if (BUG(!crypto))
+    return;
+  crypto_cipher_free(crypto->f_crypto);
+  crypto_cipher_free(crypto->b_crypto);
+  crypto_digest_free(crypto->f_digest);
+  crypto_digest_free(crypto->b_digest);
+}
+
+/** Initialize <b>crypto</b> from the key material in key_data.
+ *
+ * If <b>is_hs_v3</b> is set, this cpath will be used for next gen hidden
+ * service circuits and <b>key_data</b> must be at least
+ * HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN bytes in length.
+ *
+ * If <b>is_hs_v3</b> is not set, key_data must contain CPATH_KEY_MATERIAL_LEN
+ * bytes, which are used as follows:
+ *   - 20 to initialize f_digest
+ *   - 20 to initialize b_digest
+ *   - 16 to key f_crypto
+ *   - 16 to key b_crypto
+ *
+ * (If 'reverse' is true, then f_XX and b_XX are swapped.)
+ *
+ * Return 0 if init was successful, else -1 if it failed.
+ */
+int
+relay_crypto_init(relay_crypto_t *crypto,
+                  const char *key_data, size_t key_data_len,
+                  int reverse, int is_hs_v3)
+{
+  crypto_digest_t *tmp_digest;
+  crypto_cipher_t *tmp_crypto;
+  size_t digest_len = 0;
+  size_t cipher_key_len = 0;
+
+  tor_assert(crypto);
+  tor_assert(key_data);
+  tor_assert(!(crypto->f_crypto || crypto->b_crypto ||
+             crypto->f_digest || crypto->b_digest));
+
+  /* Basic key size validation */
+  if (is_hs_v3 && BUG(key_data_len != HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN)) {
+    goto err;
+  } else if (!is_hs_v3 && BUG(key_data_len != CPATH_KEY_MATERIAL_LEN)) {
+    goto err;
+  }
+
+  /* If we are using this crypto for next gen onion services use SHA3-256,
+     otherwise use good ol' SHA1 */
+  if (is_hs_v3) {
+    digest_len = DIGEST256_LEN;
+    cipher_key_len = CIPHER256_KEY_LEN;
+    crypto->f_digest = crypto_digest256_new(DIGEST_SHA3_256);
+    crypto->b_digest = crypto_digest256_new(DIGEST_SHA3_256);
+  } else {
+    digest_len = DIGEST_LEN;
+    cipher_key_len = CIPHER_KEY_LEN;
+    crypto->f_digest = crypto_digest_new();
+    crypto->b_digest = crypto_digest_new();
+  }
+
+  tor_assert(digest_len != 0);
+  tor_assert(cipher_key_len != 0);
+  const int cipher_key_bits = (int) cipher_key_len * 8;
+
+  crypto_digest_add_bytes(crypto->f_digest, key_data, digest_len);
+  crypto_digest_add_bytes(crypto->b_digest, key_data+digest_len, digest_len);
+
+  crypto->f_crypto = crypto_cipher_new_with_bits(key_data+(2*digest_len),
+                                                cipher_key_bits);
+  if (!crypto->f_crypto) {
+    log_warn(LD_BUG,"Forward cipher initialization failed.");
+    goto err;
+  }
+
+  crypto->b_crypto = crypto_cipher_new_with_bits(
+                                        key_data+(2*digest_len)+cipher_key_len,
+                                        cipher_key_bits);
+  if (!crypto->b_crypto) {
+    log_warn(LD_BUG,"Backward cipher initialization failed.");
+    goto err;
+  }
+
+  if (reverse) {
+    tmp_digest = crypto->f_digest;
+    crypto->f_digest = crypto->b_digest;
+    crypto->b_digest = tmp_digest;
+    tmp_crypto = crypto->f_crypto;
+    crypto->f_crypto = crypto->b_crypto;
+    crypto->b_crypto = tmp_crypto;
+  }
+
+  return 0;
+ err:
+  relay_crypto_clear(crypto);
+  return -1;
+}
+
+/** Assert that <b>crypto</b> is valid and set. */
+void
+relay_crypto_assert_ok(const relay_crypto_t *crypto)
+{
+  tor_assert(crypto->f_crypto);
+  tor_assert(crypto->b_crypto);
+  tor_assert(crypto->f_digest);
+  tor_assert(crypto->b_digest);
 }
 
diff --git a/src/or/relay_crypto.h b/src/or/relay_crypto.h
index 8d09179417..66ae02cee9 100644
--- a/src/or/relay_crypto.h
+++ b/src/or/relay_crypto.h
@@ -12,6 +12,10 @@
 #ifndef TOR_RELAY_CRYPTO_H
 #define TOR_RELAY_CRYPTO_H
 
+int relay_crypto_init(relay_crypto_t *crypto,
+                      const char *key_data, size_t key_data_len,
+                      int reverse, int is_hs_v3);
+
 int relay_decrypt_cell(circuit_t *circ, cell_t *cell,
                        cell_direction_t cell_direction,
                        crypt_path_t **layer_hint, char *recognized);
@@ -19,5 +23,9 @@ void relay_encrypt_cell_outbound(cell_t *cell, origin_circuit_t *or_circ,
                             crypt_path_t *layer_hint);
 void relay_encrypt_cell_inbound(cell_t *cell, or_circuit_t *or_circ);
 
+void relay_crypto_clear(relay_crypto_t *crypto);
+
+void relay_crypto_assert_ok(const relay_crypto_t *crypto);
+
 #endif /* !defined(TOR_RELAY_CRYPTO_H) */
 
diff --git a/src/test/bench.c b/src/test/bench.c
index 67e127311a..c0d430e052 100644
--- a/src/test/bench.c
+++ b/src/test/bench.c
@@ -505,10 +505,10 @@ bench_cell_ops(void)
   char key1[CIPHER_KEY_LEN], key2[CIPHER_KEY_LEN];
   crypto_rand(key1, sizeof(key1));
   crypto_rand(key2, sizeof(key2));
-  or_circ->p_crypto = crypto_cipher_new(key1);
-  or_circ->n_crypto = crypto_cipher_new(key2);
-  or_circ->p_digest = crypto_digest_new();
-  or_circ->n_digest = crypto_digest_new();
+  or_circ->crypto.f_crypto = crypto_cipher_new(key1);
+  or_circ->crypto.b_crypto = crypto_cipher_new(key2);
+  or_circ->crypto.f_digest = crypto_digest_new();
+  or_circ->crypto.b_digest = crypto_digest_new();
 
   reset_perftime();
 
@@ -528,10 +528,7 @@ bench_cell_ops(void)
            NANOCOUNT(start,end,iters*CELL_PAYLOAD_SIZE));
   }
 
-  crypto_digest_free(or_circ->p_digest);
-  crypto_digest_free(or_circ->n_digest);
-  crypto_cipher_free(or_circ->p_crypto);
-  crypto_cipher_free(or_circ->n_crypto);
+  relay_crypto_clear(&or_circ->crypto);
   tor_free(or_circ);
   tor_free(cell);
 }
diff --git a/src/test/test_hs_client.c b/src/test/test_hs_client.c
index 7ee7210bc9..58e12abca0 100644
--- a/src/test/test_hs_client.c
+++ b/src/test/test_hs_client.c
@@ -213,12 +213,12 @@ test_e2e_rend_circuit_setup_legacy(void *arg)
   tt_int_op(retval, OP_EQ, 1);
 
   /* Check the digest algo */
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->f_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.f_digest),
             OP_EQ, DIGEST_SHA1);
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->b_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.b_digest),
             OP_EQ, DIGEST_SHA1);
-  tt_assert(or_circ->cpath->f_crypto);
-  tt_assert(or_circ->cpath->b_crypto);
+  tt_assert(or_circ->cpath->crypto.f_crypto);
+  tt_assert(or_circ->cpath->crypto.b_crypto);
 
   /* Ensure that circ purpose was changed */
   tt_int_op(or_circ->base_.purpose, OP_EQ, CIRCUIT_PURPOSE_C_REND_JOINED);
@@ -283,12 +283,12 @@ test_e2e_rend_circuit_setup(void *arg)
   tt_int_op(retval, OP_EQ, 1);
 
   /* Check that the crypt path has prop224 algorithm parameters */
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->f_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.f_digest),
             OP_EQ, DIGEST_SHA3_256);
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->b_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.b_digest),
             OP_EQ, DIGEST_SHA3_256);
-  tt_assert(or_circ->cpath->f_crypto);
-  tt_assert(or_circ->cpath->b_crypto);
+  tt_assert(or_circ->cpath->crypto.f_crypto);
+  tt_assert(or_circ->cpath->crypto.b_crypto);
 
   /* Ensure that circ purpose was changed */
   tt_int_op(or_circ->base_.purpose, OP_EQ, CIRCUIT_PURPOSE_C_REND_JOINED);
diff --git a/src/test/test_hs_service.c b/src/test/test_hs_service.c
index 7fade6379d..ed9f9814f0 100644
--- a/src/test/test_hs_service.c
+++ b/src/test/test_hs_service.c
@@ -173,12 +173,12 @@ test_e2e_rend_circuit_setup(void *arg)
   tt_int_op(retval, OP_EQ, 1);
 
   /* Check the digest algo */
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->f_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.f_digest),
             OP_EQ, DIGEST_SHA3_256);
-  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->b_digest),
+  tt_int_op(crypto_digest_get_algorithm(or_circ->cpath->crypto.b_digest),
             OP_EQ, DIGEST_SHA3_256);
-  tt_assert(or_circ->cpath->f_crypto);
-  tt_assert(or_circ->cpath->b_crypto);
+  tt_assert(or_circ->cpath->crypto.f_crypto);
+  tt_assert(or_circ->cpath->crypto.b_crypto);
 
   /* Ensure that circ purpose was changed */
   tt_int_op(or_circ->base_.purpose, OP_EQ, CIRCUIT_PURPOSE_S_REND_JOINED);