gnunet-service-scalarproduct-ecc_alice.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2013-2017 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */
#include "platform.h"
#include <limits.h>
#include <gcrypt.h>
#include "gnunet_util_lib.h"
#include "gnunet_core_service.h"
#include "gnunet_cadet_service.h"
#include "gnunet_applications.h"
#include "gnunet_protocols.h"
#include "gnunet_scalarproduct_service.h"
#include "gnunet_seti_service.h"
#include "scalarproduct.h"
#include "gnunet-service-scalarproduct-ecc.h"

#define LOG(kind, ...) \
  GNUNET_log_from (kind, "scalarproduct-alice", __VA_ARGS__)

#define MAX_RESULT (1024 * 1024)

#define MAX_RAM (1024)

struct MpiElement
{
  const struct GNUNET_HashCode *key;

  gcry_mpi_t value;
};


struct AliceServiceSession
{
  struct GNUNET_HashCode session_id;

  struct GNUNET_PeerIdentity peer;

  struct GNUNET_SERVICE_Client *client;

  struct GNUNET_MQ_Handle *client_mq;

  struct GNUNET_MQ_Handle *cadet_mq;

  struct GNUNET_CONTAINER_MultiHashMap *intersected_elements;

  struct GNUNET_SETI_Handle *intersection_set;

  struct GNUNET_SETI_OperationHandle *intersection_op;

  struct GNUNET_SETI_ListenHandle *intersection_listen;

  struct GNUNET_CADET_Channel *channel;

  struct MpiElement *sorted_elements;

  gcry_mpi_t product;

  uint32_t total;

  uint32_t used_element_count;

  uint32_t client_received_element_count;

  enum GNUNET_SCALARPRODUCT_ResponseStatus status;

  int in_destroy;
};


static const struct GNUNET_CONFIGURATION_Handle *cfg;

static struct GNUNET_CRYPTO_EccDlogContext *edc;

static gcry_mpi_t my_privkey;

static gcry_mpi_t my_privkey_inv;

static struct GNUNET_CADET_Handle *my_cadet;


static int
free_element_cb (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  struct GNUNET_SCALARPRODUCT_Element *e = value;

  GNUNET_free (e);
  return GNUNET_OK;
}


static void
destroy_service_session (struct AliceServiceSession *s)
{
  unsigned int i;

  if (GNUNET_YES == s->in_destroy)
    return;
  s->in_destroy = GNUNET_YES;
  if (NULL != s->client)
  {
    struct GNUNET_SERVICE_Client *c = s->client;

    s->client = NULL;
    GNUNET_SERVICE_client_drop (c);
  }
  if (NULL != s->channel)
  {
    GNUNET_CADET_channel_destroy (s->channel);
    s->channel = NULL;
  }
  if (NULL != s->intersected_elements)
  {
    GNUNET_CONTAINER_multihashmap_iterate (s->intersected_elements,
                                           &free_element_cb,
                                           s);
    GNUNET_CONTAINER_multihashmap_destroy (s->intersected_elements);
    s->intersected_elements = NULL;
  }
  if (NULL != s->intersection_listen)
  {
    GNUNET_SETI_listen_cancel (s->intersection_listen);
    s->intersection_listen = NULL;
  }
  if (NULL != s->intersection_op)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Set intersection, op still ongoing!\n");
    GNUNET_SETI_operation_cancel (s->intersection_op);
    s->intersection_op = NULL;
  }
  if (NULL != s->intersection_set)
  {
    GNUNET_SETI_destroy (s->intersection_set);
    s->intersection_set = NULL;
  }
  if (NULL != s->sorted_elements)
  {
    for (i = 0; i < s->used_element_count; i++)
      gcry_mpi_release (s->sorted_elements[i].value);
    GNUNET_free (s->sorted_elements);
    s->sorted_elements = NULL;
  }
  if (NULL != s->product)
  {
    gcry_mpi_release (s->product);
    s->product = NULL;
  }
  GNUNET_free (s);
}


static void
prepare_client_end_notification (struct AliceServiceSession *session)
{
  struct ClientResponseMessage *msg;
  struct GNUNET_MQ_Envelope *e;

  if (NULL == session->client_mq)
    return; /* no client left to be notified */
  GNUNET_log (
    GNUNET_ERROR_TYPE_DEBUG,
    "Sending session-end notification with status %d to client for session %s\n",
    session->status,
    GNUNET_h2s (&session->session_id));
  e = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SCALARPRODUCT_RESULT);
  msg->product_length = htonl (0);
  msg->status = htonl (session->status);
  GNUNET_MQ_send (session->client_mq, e);
}


static void
transmit_client_response (struct AliceServiceSession *s)
{
  struct ClientResponseMessage *msg;
  struct GNUNET_MQ_Envelope *e;
  unsigned char *product_exported = NULL;
  size_t product_length = 0;
  int32_t range;
  gcry_error_t rc;
  int sign;
  gcry_mpi_t value;

  if (NULL == s->product)
  {
    GNUNET_break (0);
    prepare_client_end_notification (s);
    return;
  }
  value = gcry_mpi_new (0);
  sign = gcry_mpi_cmp_ui (s->product, 0);
  if (0 > sign)
  {
    range = -1;
    gcry_mpi_sub (value, value, s->product);
  }
  else if (0 < sign)
  {
    range = 1;
    gcry_mpi_add (value, value, s->product);
  }
  else
  {
    /* result is exactly zero */
    range = 0;
  }
  gcry_mpi_release (s->product);
  s->product = NULL;

  if ((0 != range) && (0 != (rc = gcry_mpi_aprint (GCRYMPI_FMT_STD,
                                                   &product_exported,
                                                   &product_length,
                                                   value))))
  {
    LOG_GCRY (GNUNET_ERROR_TYPE_ERROR, "gcry_mpi_scan", rc);
    prepare_client_end_notification (s);
    return;
  }
  gcry_mpi_release (value);
  e = GNUNET_MQ_msg_extra (msg,
                           product_length,
                           GNUNET_MESSAGE_TYPE_SCALARPRODUCT_RESULT);
  msg->status = htonl (GNUNET_SCALARPRODUCT_STATUS_SUCCESS);
  msg->range = htonl (range);
  msg->product_length = htonl (product_length);
  if (NULL != product_exported)
  {
    GNUNET_memcpy (&msg[1], product_exported, product_length);
    GNUNET_free (product_exported);
  }
  GNUNET_MQ_send (s->client_mq, e);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Sent result to client, session %s has ended!\n",
              GNUNET_h2s (&s->session_id));
}


static void
cb_channel_destruction (void *cls, const struct GNUNET_CADET_Channel *channel)
{
  struct AliceServiceSession *s = cls;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Peer disconnected, terminating session %s with peer %s\n",
              GNUNET_h2s (&s->session_id),
              GNUNET_i2s (&s->peer));
  s->channel = NULL;
  if (GNUNET_SCALARPRODUCT_STATUS_ACTIVE == s->status)
  {
    /* We didn't get an answer yet, fail with error */
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    prepare_client_end_notification (s);
  }
}


static gcry_mpi_t
compute_scalar_product (struct AliceServiceSession *session,
                        gcry_mpi_point_t prod_g_i_b_i,
                        gcry_mpi_point_t prod_h_i_b_i)
{
  gcry_mpi_point_t g_i_b_i_a_inv;
  gcry_mpi_point_t g_ai_bi;
  int ai_bi;
  gcry_mpi_t ret;

  g_i_b_i_a_inv =
    GNUNET_CRYPTO_ecc_pmul_mpi (edc, prod_g_i_b_i, my_privkey_inv);
  g_ai_bi = GNUNET_CRYPTO_ecc_add (edc, g_i_b_i_a_inv, prod_h_i_b_i);
  gcry_mpi_point_release (g_i_b_i_a_inv);
  ai_bi = GNUNET_CRYPTO_ecc_dlog (edc, g_ai_bi);
  gcry_mpi_point_release (g_ai_bi);
  if (INT_MAX == ai_bi)
  {
    /* result too big */
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Scalar product result out of range\n");
    return NULL;
  }
  ret = gcry_mpi_new (0);
  if (ai_bi > 0)
  {
    gcry_mpi_set_ui (ret, ai_bi);
  }
  else
  {
    gcry_mpi_set_ui (ret, -ai_bi);
    gcry_mpi_neg (ret, ret);
  }
  return ret;
}


static void
handle_bobs_cryptodata_message (void *cls,
                                const struct EccBobCryptodataMessage *msg)
{
  struct AliceServiceSession *s = cls;
  gcry_mpi_point_t prod_g_i_b_i;
  gcry_mpi_point_t prod_h_i_b_i;
  uint32_t contained;

  contained = ntohl (msg->contained_element_count);
  if (2 != contained)
  {
    GNUNET_break_op (0);
    destroy_service_session (s);
    return;
  }
  if (NULL == s->sorted_elements)
  {
    /* we're not ready yet, how can Bob be? */
    GNUNET_break_op (0);
    destroy_service_session (s);
    return;
  }
  if (s->total != s->client_received_element_count)
  {
    /* we're not ready yet, how can Bob be? */
    GNUNET_break_op (0);
    destroy_service_session (s);
    return;
  }

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received %u crypto values from Bob\n",
              (unsigned int) contained);
  GNUNET_CADET_receive_done (s->channel);
  prod_g_i_b_i = GNUNET_CRYPTO_ecc_bin_to_point (edc, &msg->prod_g_i_b_i);
  prod_h_i_b_i = GNUNET_CRYPTO_ecc_bin_to_point (edc, &msg->prod_h_i_b_i);
  s->product = compute_scalar_product (s, prod_g_i_b_i, prod_h_i_b_i);
  gcry_mpi_point_release (prod_g_i_b_i);
  gcry_mpi_point_release (prod_h_i_b_i);
  transmit_client_response (s);
}


static int
copy_element_cb (void *cls, const struct GNUNET_HashCode *key, void *value)
{
  struct AliceServiceSession *s = cls;
  struct GNUNET_SCALARPRODUCT_Element *e = value;
  gcry_mpi_t mval;
  int64_t val;

  mval = gcry_mpi_new (0);
  val = (int64_t) GNUNET_ntohll (e->value);
  if (0 > val)
    gcry_mpi_sub_ui (mval, mval, -val);
  else
    gcry_mpi_add_ui (mval, mval, val);
  s->sorted_elements[s->used_element_count].value = mval;
  s->sorted_elements[s->used_element_count].key = &e->key;
  s->used_element_count++;
  return GNUNET_OK;
}


static int
element_cmp (const void *a, const void *b)
{
  const struct MpiElement *ma = a;
  const struct MpiElement *mb = b;

  return GNUNET_CRYPTO_hash_cmp (ma->key, mb->key);
}


#define ELEMENT_CAPACITY                          \
  ((GNUNET_CONSTANTS_MAX_CADET_MESSAGE_SIZE - 1   \
    - sizeof(struct EccAliceCryptodataMessage))    \
   / sizeof(struct GNUNET_CRYPTO_EccPoint))


static void
send_alices_cryptodata_message (struct AliceServiceSession *s)
{
  struct EccAliceCryptodataMessage *msg;
  struct GNUNET_MQ_Envelope *e;
  struct GNUNET_CRYPTO_EccPoint *payload;
  gcry_mpi_t r_ia;
  gcry_mpi_t r_ia_ai;
  unsigned int i;
  unsigned int off;
  unsigned int todo_count;

  s->sorted_elements = GNUNET_new_array (GNUNET_CONTAINER_multihashmap_size (
                                           s->intersected_elements),
                                         struct MpiElement);
  s->used_element_count = 0;
  GNUNET_CONTAINER_multihashmap_iterate (s->intersected_elements,
                                         &copy_element_cb,
                                         s);
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Finished intersection, %d items remain\n",
       s->used_element_count);
  qsort (s->sorted_elements,
         s->used_element_count,
         sizeof(struct MpiElement),
         &element_cmp);
  off = 0;
  while (off < s->used_element_count)
  {
    todo_count = s->used_element_count - off;
    if (todo_count > ELEMENT_CAPACITY)
      todo_count = ELEMENT_CAPACITY;
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Sending %u/%u crypto values to Bob\n",
                (unsigned int) todo_count,
                (unsigned int) s->used_element_count);

    e =
      GNUNET_MQ_msg_extra (msg,
                           todo_count * 2
                           * sizeof(struct GNUNET_CRYPTO_EccPoint),
                           GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_ALICE_CRYPTODATA);
    msg->contained_element_count = htonl (todo_count);
    payload = (struct GNUNET_CRYPTO_EccPoint *) &msg[1];
    r_ia = gcry_mpi_new (0);
    r_ia_ai = gcry_mpi_new (0);
    for (i = off; i < off + todo_count; i++)
    {
      gcry_mpi_t r_i;
      gcry_mpi_point_t g_i;
      gcry_mpi_point_t h_i;

      r_i = GNUNET_CRYPTO_ecc_random_mod_n (edc);
      g_i = GNUNET_CRYPTO_ecc_dexp_mpi (edc, r_i);
      /* r_ia = r_i * a */
      gcry_mpi_mul (r_ia, r_i, my_privkey);
      gcry_mpi_release (r_i);
      /* r_ia_ai = r_ia + a_i */
      gcry_mpi_add (r_ia_ai, r_ia, s->sorted_elements[i].value);
      h_i = GNUNET_CRYPTO_ecc_dexp_mpi (edc, r_ia_ai);
      GNUNET_CRYPTO_ecc_point_to_bin (edc, g_i, &payload[(i - off) * 2]);
      GNUNET_CRYPTO_ecc_point_to_bin (edc, h_i, &payload[(i - off) * 2 + 1]);
      gcry_mpi_point_release (g_i);
      gcry_mpi_point_release (h_i);
    }
    gcry_mpi_release (r_ia);
    gcry_mpi_release (r_ia_ai);
    off += todo_count;
    GNUNET_MQ_send (s->cadet_mq, e);
  }
}


static void
cb_intersection_element_removed (void *cls,
                                 const struct GNUNET_SETI_Element *element,
                                 uint64_t current_size,
                                 enum GNUNET_SETI_Status status)
{
  struct AliceServiceSession *s = cls;
  struct GNUNET_SCALARPRODUCT_Element *se;

  switch (status)
  {
  case GNUNET_SETI_STATUS_DEL_LOCAL:
    /* this element has been removed from the set */
    se = GNUNET_CONTAINER_multihashmap_get (s->intersected_elements,
                                            element->data);
    GNUNET_assert (NULL != se);
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Intersection removed element with key %s and value %lld\n",
         GNUNET_h2s (&se->key),
         (long long) GNUNET_ntohll (se->value));
    GNUNET_assert (
      GNUNET_YES ==
      GNUNET_CONTAINER_multihashmap_remove (s->intersected_elements,
                                            element->data,
                                            se));
    GNUNET_free (se);
    return;
  case GNUNET_SETI_STATUS_DONE:
    s->intersection_op = NULL;
    if (NULL != s->intersection_set)
    {
      GNUNET_SETI_destroy (s->intersection_set);
      s->intersection_set = NULL;
    }
    send_alices_cryptodata_message (s);
    return;
  case GNUNET_SETI_STATUS_FAILURE:
    /* unhandled status code */
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Set intersection failed!\n");
    if (NULL != s->intersection_listen)
    {
      GNUNET_SETI_listen_cancel (s->intersection_listen);
      s->intersection_listen = NULL;
    }
    s->intersection_op = NULL;
    if (NULL != s->intersection_set)
    {
      GNUNET_SETI_destroy (s->intersection_set);
      s->intersection_set = NULL;
    }
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    prepare_client_end_notification (s);
    return;

  default:
    GNUNET_break (0);
    return;
  }
}


static void
cb_intersection_request_alice (void *cls,
                               const struct GNUNET_PeerIdentity *other_peer,
                               const struct GNUNET_MessageHeader *context_msg,
                               struct GNUNET_SETI_Request *request)
{
  struct AliceServiceSession *s = cls;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Received intersection request from %s!\n",
              GNUNET_i2s (other_peer));
  if (0 != GNUNET_memcmp (other_peer, &s->peer))
  {
    GNUNET_break_op (0);
    return;
  }
  s->intersection_op = GNUNET_SETI_accept (request,
                                           (struct
                                            GNUNET_SETI_Option[]){ { 0 } },
                                           &cb_intersection_element_removed,
                                           s);
  if (NULL == s->intersection_op)
  {
    GNUNET_break (0);
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    prepare_client_end_notification (s);
    return;
  }
  if (GNUNET_OK != GNUNET_SETI_commit (s->intersection_op, s->intersection_set))
  {
    GNUNET_break (0);
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    prepare_client_end_notification (s);
    return;
  }
}


static void
client_request_complete_alice (struct AliceServiceSession *s)
{
  struct GNUNET_MQ_MessageHandler cadet_handlers[] =
  { GNUNET_MQ_hd_fixed_size (bobs_cryptodata_message,
                             GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_BOB_CRYPTODATA,
                             struct EccBobCryptodataMessage,
                             s),
    GNUNET_MQ_handler_end () };
  struct EccServiceRequestMessage *msg;
  struct GNUNET_MQ_Envelope *e;
  struct GNUNET_HashCode set_sid;

  GNUNET_CRYPTO_hash (&s->session_id,
                      sizeof(struct GNUNET_HashCode),
                      &set_sid);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Creating new channel for session with key %s.\n",
              GNUNET_h2s (&s->session_id));
  s->channel = GNUNET_CADET_channel_create (my_cadet,
                                            s,
                                            &s->peer,
                                            &s->session_id,
                                            NULL,
                                            &cb_channel_destruction,
                                            cadet_handlers);
  if (NULL == s->channel)
  {
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    prepare_client_end_notification (s);
    return;
  }
  s->cadet_mq = GNUNET_CADET_get_mq (s->channel);
  s->intersection_listen = GNUNET_SETI_listen (cfg,
                                               &set_sid,
                                               &cb_intersection_request_alice,
                                               s);
  if (NULL == s->intersection_listen)
  {
    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
    GNUNET_CADET_channel_destroy (s->channel);
    s->channel = NULL;
    prepare_client_end_notification (s);
    return;
  }

  e =
    GNUNET_MQ_msg (msg,
                   GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_SESSION_INITIALIZATION);
  GNUNET_MQ_env_set_options (e, GNUNET_MQ_PRIO_CRITICAL_CONTROL);
  msg->session_id = s->session_id;
  GNUNET_MQ_send (s->cadet_mq, e);
}


static int
check_alice_client_message_multipart (
  void *cls,
  const struct ComputationBobCryptodataMultipartMessage *msg)
{
  struct AliceServiceSession *s = cls;
  uint32_t contained_count;
  uint16_t msize;

  msize = ntohs (msg->header.size);
  contained_count = ntohl (msg->element_count_contained);
  if ((msize !=
       (sizeof(struct ComputationBobCryptodataMultipartMessage)
        + contained_count * sizeof(struct GNUNET_SCALARPRODUCT_Element))) ||
      (0 == contained_count) ||
      (s->total == s->client_received_element_count) ||
      (s->total < s->client_received_element_count + contained_count))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_alice_client_message_multipart (
  void *cls,
  const struct ComputationBobCryptodataMultipartMessage *msg)
{
  struct AliceServiceSession *s = cls;
  uint32_t contained_count;
  const struct GNUNET_SCALARPRODUCT_Element *elements;
  struct GNUNET_SETI_Element set_elem;
  struct GNUNET_SCALARPRODUCT_Element *elem;

  contained_count = ntohl (msg->element_count_contained);
  s->client_received_element_count += contained_count;
  elements = (const struct GNUNET_SCALARPRODUCT_Element *) &msg[1];
  for (uint32_t i = 0; i < contained_count; i++)
  {
    elem = GNUNET_new (struct GNUNET_SCALARPRODUCT_Element);
    GNUNET_memcpy (elem,
                   &elements[i],
                   sizeof(struct GNUNET_SCALARPRODUCT_Element));
    if (GNUNET_SYSERR == GNUNET_CONTAINER_multihashmap_put (
          s->intersected_elements,
          &elem->key,
          elem,
          GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
    {
      GNUNET_break (0);
      GNUNET_free (elem);
      continue;
    }
    set_elem.data = &elem->key;
    set_elem.size = sizeof(elem->key);
    set_elem.element_type = 0;
    GNUNET_SETI_add_element (s->intersection_set, &set_elem, NULL, NULL);
    s->used_element_count++;
  }
  GNUNET_SERVICE_client_continue (s->client);
  if (s->total != s->client_received_element_count)
  {
    /* more to come */
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received client multipart data, waiting for more!\n");
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Launching computation\n");
  client_request_complete_alice (s);
}


static int
check_alice_client_message (void *cls,
                            const struct AliceComputationMessage *msg)
{
  struct AliceServiceSession *s = cls;
  uint16_t msize;
  uint32_t total_count;
  uint32_t contained_count;

  if (NULL != s->intersected_elements)
  {
    /* only one concurrent session per client connection allowed,
       simplifies logic a lot... */
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  msize = ntohs (msg->header.size);
  total_count = ntohl (msg->element_count_total);
  contained_count = ntohl (msg->element_count_contained);
  if ((0 == total_count) || (0 == contained_count) ||
      (msize !=
       (sizeof(struct AliceComputationMessage)
        + contained_count * sizeof(struct GNUNET_SCALARPRODUCT_Element))))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


static void
handle_alice_client_message (void *cls,
                             const struct AliceComputationMessage *msg)
{
  struct AliceServiceSession *s = cls;
  uint32_t contained_count;
  uint32_t total_count;
  const struct GNUNET_SCALARPRODUCT_Element *elements;
  struct GNUNET_SETI_Element set_elem;
  struct GNUNET_SCALARPRODUCT_Element *elem;

  total_count = ntohl (msg->element_count_total);
  contained_count = ntohl (msg->element_count_contained);
  s->peer = msg->peer;
  s->status = GNUNET_SCALARPRODUCT_STATUS_ACTIVE;
  s->total = total_count;
  s->client_received_element_count = contained_count;
  s->session_id = msg->session_key;
  elements = (const struct GNUNET_SCALARPRODUCT_Element *) &msg[1];
  s->intersected_elements =
    GNUNET_CONTAINER_multihashmap_create (s->total, GNUNET_YES);
  s->intersection_set = GNUNET_SETI_create (cfg);
  for (uint32_t i = 0; i < contained_count; i++)
  {
    if (0 == GNUNET_ntohll (elements[i].value))
      continue;
    elem = GNUNET_new (struct GNUNET_SCALARPRODUCT_Element);
    GNUNET_memcpy (elem,
                   &elements[i],
                   sizeof(struct GNUNET_SCALARPRODUCT_Element));
    if (GNUNET_SYSERR == GNUNET_CONTAINER_multihashmap_put (
          s->intersected_elements,
          &elem->key,
          elem,
          GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
    {
      /* element with same key encountered twice! */
      GNUNET_break (0);
      GNUNET_free (elem);
      continue;
    }
    set_elem.data = &elem->key;
    set_elem.size = sizeof(elem->key);
    set_elem.element_type = 0;
    GNUNET_SETI_add_element (s->intersection_set, &set_elem, NULL, NULL);
    s->used_element_count++;
  }
  GNUNET_SERVICE_client_continue (s->client);
  if (s->total != s->client_received_element_count)
  {
    /* wait for multipart msg */
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "Received partial client request, waiting for more!\n");
    return;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Launching computation\n");
  client_request_complete_alice (s);
}


static void
shutdown_task (void *cls)
{
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Shutting down, initiating cleanup.\n");
  // FIXME: we have to cut our connections to CADET first!
  if (NULL != my_cadet)
  {
    GNUNET_CADET_disconnect (my_cadet);
    my_cadet = NULL;
  }
  if (NULL != edc)
  {
    GNUNET_CRYPTO_ecc_dlog_release (edc);
    edc = NULL;
  }
}


static void *
client_connect_cb (void *cls,
                   struct GNUNET_SERVICE_Client *client,
                   struct GNUNET_MQ_Handle *mq)
{
  struct AliceServiceSession *s;

  s = GNUNET_new (struct AliceServiceSession);
  s->client = client;
  s->client_mq = mq;
  return s;
}


static void
client_disconnect_cb (void *cls,
                      struct GNUNET_SERVICE_Client *client,
                      void *app_cls)
{
  struct AliceServiceSession *s = app_cls;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Client %p disconnected from us.\n",
              client);
  s->client = NULL;
  s->client_mq = NULL;
  destroy_service_session (s);
}


static void
run (void *cls,
     const struct GNUNET_CONFIGURATION_Handle *c,
     struct GNUNET_SERVICE_Handle *service)
{
  cfg = c;
  edc = GNUNET_CRYPTO_ecc_dlog_prepare (MAX_RESULT, MAX_RAM);
  /* Select a random 'a' value for Alice */
  GNUNET_CRYPTO_ecc_rnd_mpi (edc, &my_privkey, &my_privkey_inv);
  my_cadet = GNUNET_CADET_connect (cfg);
  if (NULL == my_cadet)
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, _ ("Connect to CADET failed\n"));
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_SCHEDULER_add_shutdown (&shutdown_task, NULL);
}


GNUNET_SERVICE_MAIN (
  "scalarproduct-alice",
  GNUNET_SERVICE_OPTION_NONE,
  &run,
  &client_connect_cb,
  &client_disconnect_cb,
  NULL,
  GNUNET_MQ_hd_var_size (alice_client_message,
                         GNUNET_MESSAGE_TYPE_SCALARPRODUCT_CLIENT_TO_ALICE,
                         struct AliceComputationMessage,
                         NULL),
  GNUNET_MQ_hd_var_size (
    alice_client_message_multipart,
    GNUNET_MESSAGE_TYPE_SCALARPRODUCT_CLIENT_MULTIPART_ALICE,
    struct ComputationBobCryptodataMultipartMessage,
    NULL),
  GNUNET_MQ_handler_end ());


/* end of gnunet-service-scalarproduct-ecc_alice.c */