gnunet-service-scalarproduct-ecc_alice.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2013-2017, 2021 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_cadet_service.h"
#include "gnunet_protocols.h"
#include "gnunet_scalarproduct_service.h"
#include "gnunet_seti_service.h"
#include "scalarproduct.h"
#include "gnunet-service-scalarproduct-ecc.h"
#include "gnunet_constants.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;
 
  int64_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;
 
  int 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 struct GNUNET_CRYPTO_EccScalar my_privkey;
 
static struct GNUNET_CRYPTO_EccScalar 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)
{
  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)
  {
    GNUNET_free (s->sorted_elements);
    s->sorted_elements = 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;
  gcry_mpi_t value;
 
  if (INT_MAX == s->product)
  {
    GNUNET_break (0);
    prepare_client_end_notification (s);
    return;
  }
  value = gcry_mpi_new (32);
  if (0 > s->product)
  {
    range = -1;
    gcry_mpi_set_ui (value,
                     -s->product);
  }
  else if (0 < s->product)
  {
    range = 1;
    gcry_mpi_set_ui (value,
                     s->product);
  }
  else
  {
    /* result is exactly zero */
    range = 0;
  }
  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 void
handle_bobs_cryptodata_message (void *cls,
                                const struct EccBobCryptodataMessage *msg)
{
  struct AliceServiceSession *s = cls;
  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);
  {
    struct GNUNET_CRYPTO_EccPoint g_i_b_i_a_inv;
    struct GNUNET_CRYPTO_EccPoint g_ai_bi;
 
    GNUNET_assert (
      GNUNET_OK ==
      GNUNET_CRYPTO_ecc_pmul_mpi (&msg->prod_g_i_b_i,
                                  &my_privkey_inv,
                                  &g_i_b_i_a_inv));
    GNUNET_assert (
      GNUNET_OK ==
      GNUNET_CRYPTO_ecc_add (&g_i_b_i_a_inv,
                             &msg->prod_h_i_b_i,
                             &g_ai_bi));
    s->product = GNUNET_CRYPTO_ecc_dlog (edc,
                                         &g_ai_bi);
    if (INT_MAX == s->product)
    {
      /* result too big */
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                  "Scalar product result out of range\n");
    }
  }
  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;
 
  s->sorted_elements[s->used_element_count].value = (int64_t) GNUNET_ntohll (
    e->value);
  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;
  struct GNUNET_CRYPTO_EccScalar r_ia;
  struct GNUNET_CRYPTO_EccScalar r_ia_ai;
  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];
    for (unsigned int i = off; i < off + todo_count; i++)
    {
      struct GNUNET_CRYPTO_EccScalar r_i;
      struct GNUNET_CRYPTO_EccPoint g_i;
      struct GNUNET_CRYPTO_EccPoint h_i;
 
      /* r_i = random() mod n */
      GNUNET_CRYPTO_ecc_random_mod_n (&r_i);
      /* g_i = g^{r_i} */
      GNUNET_assert (GNUNET_OK ==
                     GNUNET_CRYPTO_ecc_dexp_mpi (&r_i,
                                                 &g_i));
      /* r_ia = r_i * a */
      crypto_core_ed25519_scalar_mul (r_ia.v,
                                      r_i.v,
                                      my_privkey.v);
      /* r_ia_ai = r_ia + a_i */
      {
        int64_t val = s->sorted_elements[i].value;
        struct GNUNET_CRYPTO_EccScalar vali;
 
        GNUNET_assert (INT64_MIN != val);
        GNUNET_CRYPTO_ecc_scalar_from_int (val > 0 ? val : -val,
                                           &vali);
        if (val > 0)
          crypto_core_ed25519_scalar_add (r_ia_ai.v,
                                          r_ia.v,
                                          vali.v);
        else
          crypto_core_ed25519_scalar_sub (r_ia_ai.v,
                                          r_ia.v,
                                          vali.v);
      }
      /* h_i = g^{r_ia_ai} */
      GNUNET_assert (GNUNET_OK ==
                     GNUNET_CRYPTO_ecc_dexp_mpi (&r_ia_ai,
                                                 &h_i));
      memcpy (&payload[(i - off) * 2],
              &g_i,
              sizeof (g_i));
      memcpy (&payload[(i - off) * 2 + 1],
              &h_i,
              sizeof (h_i));
    }
    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);
    *elem = elements[i];
    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 (&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 (
  GNUNET_OS_project_data_gnunet(),
  "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 */