prop224: Build INTRODUCE1 cell and send logic

Add a function in hs_cell.{c|h} for a client to build an INTRODUCE1 cell using
an object that contains all the needed keys to do so.

Add an entry point in hs_client.c that allows a tor client to send an
INTRODUCE1 cell on a given introduction circuit.

It includes the building of the cell, sending it and the setup of the
rendezvous circuit with the circuit identifier.

The entry point function is still unused at this commit.

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/src/or/hs_cell.h b/src/or/hs_cell.h
index f32f7a4216..a72009510c 100644
--- a/src/or/hs_cell.h
+++ b/src/or/hs_cell.h
@@ -12,11 +12,39 @@
 #include "or.h"
 #include "hs_service.h"
 
+/* An INTRODUCE1 cell requires at least this amount of bytes (see section
+ * 3.2.2 of the specification). Below this value, the cell must be padded. */
+#define HS_CELL_INTRODUCE1_MIN_SIZE 246
+
 /* Onion key type found in the INTRODUCE1 cell. */
 typedef enum {
   HS_CELL_ONION_KEY_TYPE_NTOR = 1,
 } hs_cell_onion_key_type_t;
 
+/* This data structure contains data that we need to build an INTRODUCE1 cell
+ * used by the INTRODUCE1 build function. */
+typedef struct hs_cell_introduce1_data_t {
+  /* Is this a legacy introduction point? */
+  unsigned int is_legacy : 1;
+  /* (Legacy only) The encryption key for a legacy intro point. Only set if
+   * is_legacy is true. */
+  const crypto_pk_t *legacy_key;
+  /* Introduction point authentication public key. */
+  const ed25519_public_key_t *auth_pk;
+  /* Introduction point encryption public key. */
+  const curve25519_public_key_t *enc_pk;
+  /* Subcredentials of the service. */
+  const uint8_t *subcredential;
+  /* Onion public key for the ntor handshake. */
+  const curve25519_public_key_t *onion_pk;
+  /* Rendezvous cookie. */
+  const uint8_t *rendezvous_cookie;
+  /* Public key put before the encrypted data (CLIENT_PK). */
+  const curve25519_keypair_t *client_kp;
+  /* Rendezvous point link specifiers. */
+  smartlist_t *link_specifiers;
+} hs_cell_introduce1_data_t;
+
 /* This data structure contains data that we need to parse an INTRODUCE2 cell
  * which is used by the INTRODUCE2 cell parsing function. On a successful
  * parsing, the onion_pk and rendezvous_cookie will be populated with the
@@ -63,6 +91,8 @@ ssize_t hs_cell_build_rendezvous1(const uint8_t *rendezvous_cookie,
                                   const uint8_t *rendezvous_handshake_info,
                                   size_t rendezvous_handshake_info_len,
                                   uint8_t *cell_out);
+ssize_t hs_cell_build_introduce1(const hs_cell_introduce1_data_t *data,
+                                 uint8_t *cell_out);
 
 /* Parse cell API. */
 ssize_t hs_cell_parse_intro_established(const uint8_t *payload,