summaryrefslogtreecommitdiff
path: root/src/exchange/taler-exchange-httpd_melt.c
blob: 7276f9a6576952eb2a0c910c281fa96ec0f63b04 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
/*
  This file is part of TALER
  Copyright (C) 2014-2020 Taler Systems SA

  TALER 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, or (at your option) any later version.

  TALER 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
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file taler-exchange-httpd_melt.c
 * @brief Handle melt requests
 * @author Florian Dold
 * @author Benedikt Mueller
 * @author Christian Grothoff
 */
#include "platform.h"
#include <gnunet/gnunet_util_lib.h>
#include <jansson.h>
#include <microhttpd.h>
#include "taler_json_lib.h"
#include "taler_mhd_lib.h"
#include "taler-exchange-httpd_mhd.h"
#include "taler-exchange-httpd_melt.h"
#include "taler-exchange-httpd_responses.h"
#include "taler-exchange-httpd_keys.h"
#include "taler_exchangedb_lib.h"


/**
 * Send a response for a failed "melt" request.  The
 * transaction history of the given coin demonstrates that the
 * @a residual value of the coin is below the @a requested
 * contribution of the coin for the melt.  Thus, the exchange
 * refuses the melt operation.
 *
 * @param connection the connection to send the response to
 * @param coin_pub public key of the coin
 * @param coin_value original value of the coin
 * @param tl transaction history for the coin
 * @param requested how much this coin was supposed to contribute, including fee
 * @param residual remaining value of the coin (after subtracting @a tl)
 * @return a MHD result code
 */
static MHD_RESULT
reply_melt_insufficient_funds (
  struct MHD_Connection *connection,
  const struct TALER_CoinSpendPublicKeyP *coin_pub,
  const struct TALER_Amount *coin_value,
  struct TALER_EXCHANGEDB_TransactionList *tl,
  const struct TALER_Amount *requested,
  const struct TALER_Amount *residual)
{
  json_t *history;

  history = TEH_RESPONSE_compile_transaction_history (coin_pub,
                                                      tl);
  if (NULL == history)
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_EXCHANGE_MELT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS,
                                       NULL);
  return TALER_MHD_reply_json_pack (
    connection,
    MHD_HTTP_CONFLICT,
    "{s:s, s:I, s:o, s:o, s:o, s:o, s:o}",
    "hint",
    TALER_ErrorCode_get_hint (TALER_EC_EXCHANGE_MELT_INSUFFICIENT_FUNDS),
    "code",
    (json_int_t) TALER_EC_EXCHANGE_MELT_INSUFFICIENT_FUNDS,
    "coin_pub",
    GNUNET_JSON_from_data_auto (coin_pub),
    "original_value",
    TALER_JSON_from_amount (coin_value),
    "residual_value",
    TALER_JSON_from_amount (residual),
    "requested_value",
    TALER_JSON_from_amount (requested),
    "history",
    history);
}


/**
 * Send a response to a "melt" request.
 *
 * @param connection the connection to send the response to
 * @param rc value the client committed to
 * @param noreveal_index which index will the client not have to reveal
 * @return a MHD status code
 */
static MHD_RESULT
reply_melt_success (struct MHD_Connection *connection,
                    const struct TALER_RefreshCommitmentP *rc,
                    uint32_t noreveal_index)
{
  struct TALER_ExchangePublicKeyP pub;
  struct TALER_ExchangeSignatureP sig;
  struct TALER_RefreshMeltConfirmationPS body = {
    .purpose.size = htonl (sizeof (body)),
    .purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_MELT),
    .rc = *rc,
    .noreveal_index = htonl (noreveal_index)
  };
  enum TALER_ErrorCode ec;

  if (TALER_EC_NONE !=
      (ec = TEH_keys_exchange_sign (&body,
                                    &pub,
                                    &sig)))
  {
    return TALER_MHD_reply_with_ec (connection,
                                    ec,
                                    NULL);
  }
  return TALER_MHD_reply_json_pack (
    connection,
    MHD_HTTP_OK,
    "{s:i, s:o, s:o}",
    "noreveal_index", (int) noreveal_index,
    "exchange_sig", GNUNET_JSON_from_data_auto (&sig),
    "exchange_pub", GNUNET_JSON_from_data_auto (&pub));
}


/**
 * Context for the melt operation.
 */
struct MeltContext
{

  /**
   * noreveal_index is only initialized during
   * #melt_transaction().
   */
  struct TALER_EXCHANGEDB_Refresh refresh_session;

  /**
   * Information about the @e coin's value.
   */
  struct TALER_Amount coin_value;

  /**
   * Information about the @e coin's refresh fee.
   */
  struct TALER_Amount coin_refresh_fee;

  /**
   * Set to true if this coin's denomination was revoked and the operation
   * is thus only allowed for zombie coins where the transaction
   * history includes a #TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP.
   */
  bool zombie_required;

  /**
   * We already checked and noticed that the coin is known. Hence we
   * can skip the "ensure_coin_known" step of the transaction.
   */
  bool coin_is_dirty;

};


/**
 * Check that the coin has sufficient funds left for the selected
 * melt operation.
 *
 * @param connection the connection to send errors to
 * @param session the database connection
 * @param[in,out] rmc melt context
 * @param[out] mhd_ret status code to return to MHD on hard error
 * @return transaction status code
 */
static enum GNUNET_DB_QueryStatus
refresh_check_melt (struct MHD_Connection *connection,
                    struct TALER_EXCHANGEDB_Session *session,
                    struct MeltContext *rmc,
                    MHD_RESULT *mhd_ret)
{
  struct TALER_EXCHANGEDB_TransactionList *tl;
  struct TALER_Amount spent;
  enum GNUNET_DB_QueryStatus qs;

  /* Start with cost of this melt transaction */
  spent = rmc->refresh_session.amount_with_fee;

  /* get historic transaction costs of this coin, including recoups as
     we might be a zombie coin */
  qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
                                          session,
                                          &rmc->refresh_session.coin.coin_pub,
                                          GNUNET_YES,
                                          &tl);
  if (0 > qs)
  {
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      *mhd_ret = TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
                                             "coin transaction history");
    return qs;
  }
  if (rmc->zombie_required)
  {
    /* The denomination key is only usable for a melt if this is a true
       zombie coin, i.e. it was refreshed and the resulting fresh coin was
       then recouped. Check that this is truly the case. */
    for (struct TALER_EXCHANGEDB_TransactionList *tp = tl;
         NULL != tp;
         tp = tp->next)
    {
      if (TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP == tp->type)
      {
        rmc->zombie_required = false; /* clear flag: was satisfied! */
        break;
      }
    }
    if (rmc->zombie_required)
    {
      /* zombie status not satisfied */
      GNUNET_break_op (0);
      TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                              tl);
      *mhd_ret = TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_BAD_REQUEST,
                                             TALER_EC_EXCHANGE_MELT_COIN_EXPIRED_NO_ZOMBIE,
                                             NULL);
      return GNUNET_DB_STATUS_HARD_ERROR;
    }
  }
  if (GNUNET_OK !=
      TALER_EXCHANGEDB_calculate_transaction_list_totals (tl,
                                                          &spent,
                                                          &spent))
  {
    GNUNET_break (0);
    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                            tl);
    *mhd_ret = TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_EXCHANGE_MELT_COIN_HISTORY_COMPUTATION_FAILED,
                                           NULL);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }

  /* Refuse to refresh when the coin's value is insufficient
     for the cost of all transactions. */
  if (0 > TALER_amount_cmp (&rmc->coin_value,
                            &spent))
  {
    struct TALER_Amount coin_residual;
    struct TALER_Amount spent_already;

    /* First subtract the melt cost from 'spent' to
       compute the total amount already spent of the coin */
    GNUNET_assert (0 <=
                   TALER_amount_subtract (&spent_already,
                                          &spent,
                                          &rmc->refresh_session.amount_with_fee));
    /* The residual coin value is the original coin value minus
       what we have spent (before the melt) */
    GNUNET_assert (0 <=
                   TALER_amount_subtract (&coin_residual,
                                          &rmc->coin_value,
                                          &spent_already));
    *mhd_ret = reply_melt_insufficient_funds (
      connection,
      &rmc->refresh_session.coin.coin_pub,
      &rmc->coin_value,
      tl,
      &rmc->refresh_session.amount_with_fee,
      &coin_residual);
    TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                            tl);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }

  /* we're good, coin has sufficient funds to be melted */
  TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                          tl);
  return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
}


/**
 * Execute a "melt".  We have been given a list of valid
 * coins and a request to melt them into the given @a
 * refresh_session_pub.  Check that the coins all have the required
 * value left and if so, store that they have been melted and confirm
 * the melting operation to the client.
 *
 * If it returns a non-error code, the transaction logic MUST NOT
 * queue a MHD response.  IF it returns an hard error, the transaction
 * logic MUST queue a MHD response and set @a mhd_ret.  If it returns
 * the soft error code, the function MAY be called again to retry and
 * MUST not queue a MHD response.
 *
 * @param cls our `struct MeltContext`
 * @param connection MHD request which triggered the transaction
 * @param session database session to use
 * @param[out] mhd_ret set to MHD response status for @a connection,
 *             if transaction failed (!)
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
melt_transaction (void *cls,
                  struct MHD_Connection *connection,
                  struct TALER_EXCHANGEDB_Session *session,
                  MHD_RESULT *mhd_ret)
{
  struct MeltContext *rmc = cls;
  enum GNUNET_DB_QueryStatus qs;
  uint32_t noreveal_index;

  /* First, make sure coin is 'known' in database */
  if (! rmc->coin_is_dirty)
  {
    qs = TEH_make_coin_known (&rmc->refresh_session.coin,
                              connection,
                              session,
                              mhd_ret);
    if (qs < 0)
      return qs;
  }

  /* Check if we already created a matching refresh_session */
  qs = TEH_plugin->get_melt_index (TEH_plugin->cls,
                                   session,
                                   &rmc->refresh_session.rc,
                                   &noreveal_index);
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
  {
    TALER_LOG_DEBUG ("Coin was previously melted, returning old reply\n");
    *mhd_ret = reply_melt_success (connection,
                                   &rmc->refresh_session.rc,
                                   noreveal_index);
    /* Note: we return "hard error" to ensure the wrapper
       does not retry the transaction, and to also not generate
       a "fresh" response (as we would on "success") */
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  if (0 > qs)
  {
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      *mhd_ret = TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
                                             "melt index");
    return qs;
  }

  /* check coin has enough funds remaining on it to cover melt cost */
  qs = refresh_check_melt (connection,
                           session,
                           rmc,
                           mhd_ret);
  if (0 > qs)
    return qs; /* if we failed, tell caller */

  /* pick challenge and persist it */
  rmc->refresh_session.noreveal_index
    = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
                                TALER_CNC_KAPPA);
  if (0 >=
      (qs = TEH_plugin->insert_melt (TEH_plugin->cls,
                                     session,
                                     &rmc->refresh_session)))
  {
    if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
    {
      *mhd_ret = TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_GENERIC_DB_STORE_FAILED,
                                             "melt");
      return GNUNET_DB_STATUS_HARD_ERROR;
    }
    return qs;
  }
  return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
}


/**
 * Handle a "melt" request after the first parsing has
 * happened.  We now need to validate the coins being melted and the
 * session signature and then hand things of to execute the melt
 * operation.  This function parses the JSON arrays and then passes
 * processing on to #melt_transaction().
 *
 * @param connection the MHD connection to handle
 * @param[in,out] rmc details about the melt request
 * @return MHD result code
 */
static MHD_RESULT
handle_melt (struct MHD_Connection *connection,
             struct MeltContext *rmc)
{
  /* verify signature of coin for melt operation */
  {
    struct TALER_RefreshMeltCoinAffirmationPS body = {
      .purpose.size = htonl (sizeof (body)),
      .purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT),
      .rc = rmc->refresh_session.rc,
      .h_denom_pub = rmc->refresh_session.coin.denom_pub_hash,
      .coin_pub = rmc->refresh_session.coin.coin_pub
    };

    TALER_amount_hton (&body.amount_with_fee,
                       &rmc->refresh_session.amount_with_fee);
    TALER_amount_hton (&body.melt_fee,
                       &rmc->coin_refresh_fee);

    if (GNUNET_OK !=
        GNUNET_CRYPTO_eddsa_verify (
          TALER_SIGNATURE_WALLET_COIN_MELT,
          &body,
          &rmc->refresh_session.coin_sig.eddsa_signature,
          &rmc->refresh_session.coin.coin_pub.eddsa_pub))
    {
      GNUNET_break_op (0);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_FORBIDDEN,
                                         TALER_EC_EXCHANGE_MELT_COIN_SIGNATURE_INVALID,
                                         NULL);
    }
  }

  /* run database transaction */
  {
    MHD_RESULT mhd_ret;

    if (GNUNET_OK !=
        TEH_DB_run_transaction (connection,
                                "run melt",
                                &mhd_ret,
                                &melt_transaction,
                                rmc))
      return mhd_ret;
  }

  /* Success. Generate ordinary response. */
  return reply_melt_success (connection,
                             &rmc->refresh_session.rc,
                             rmc->refresh_session.noreveal_index);
}


/**
 * Check for information about the melted coin's denomination,
 * extracting its validity status and fee structure.
 *
 * @param connection HTTP connection we are handling
 * @param rmc parsed request information
 * @return MHD status code
 */
static MHD_RESULT
check_for_denomination_key (struct MHD_Connection *connection,
                            struct MeltContext *rmc)
{
  /* Baseline: check if deposits/refreshs are generally
     simply still allowed for this denomination */
  struct TEH_DenominationKey *dk;
  struct GNUNET_TIME_Absolute now;
  MHD_RESULT mret;

  dk = TEH_keys_denomination_by_hash (
    &rmc->refresh_session.coin.denom_pub_hash,
    connection,
    &mret);
  if (NULL == dk)
    return mret;
  now = GNUNET_TIME_absolute_get ();
  (void) GNUNET_TIME_round_abs (&now);
  if (now.abs_value_us >= dk->meta.expire_legal.abs_value_us)
  {
    /* Way too late now, even zombies have expired */
    return TEH_RESPONSE_reply_expired_denom_pub_hash (
      connection,
      &rmc->refresh_session.coin.denom_pub_hash,
      now,
      TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
      "MELT");
  }
  if (now.abs_value_us < dk->meta.start.abs_value_us)
  {
    /* This denomination is not yet valid */
    return TEH_RESPONSE_reply_expired_denom_pub_hash (
      connection,
      &rmc->refresh_session.coin.denom_pub_hash,
      now,
      TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
      "MELT");
  }
  if (now.abs_value_us >= dk->meta.expire_deposit.abs_value_us)
  {
    /* We are past deposit expiration time, but maybe this is a zombie? */
    struct GNUNET_HashCode denom_hash;
    enum GNUNET_DB_QueryStatus qs;

    /* Check that the coin is dirty (we have seen it before), as we will
       not just allow melting of a *fresh* coin where the denomination was
       revoked (those must be recouped) */
    qs = TEH_plugin->get_coin_denomination (
      TEH_plugin->cls,
      NULL,
      &rmc->refresh_session.coin.coin_pub,
      &denom_hash);
    if (0 > qs)
    {
      /* There is no good reason for a serialization failure here: */
      GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
      return TALER_MHD_reply_with_error (connection,
                                         MHD_HTTP_INTERNAL_SERVER_ERROR,
                                         TALER_EC_GENERIC_DB_FETCH_FAILED,
                                         "coin denomination");
    }
    /* sanity check */
    GNUNET_break (0 ==
                  GNUNET_memcmp (&denom_hash,
                                 &rmc->refresh_session.coin.denom_pub_hash));
    if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
    {
      /* We never saw this coin before, so _this_ justification is not OK */
      return TEH_RESPONSE_reply_expired_denom_pub_hash (
        connection,
        &rmc->refresh_session.coin.denom_pub_hash,
        now,
        TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
        "MELT");
    }
    else
    {
      /* Minor optimization: no need to run the
         "ensure_coin_known" part of the transaction */
      rmc->coin_is_dirty = true;
    }
    rmc->zombie_required = true;   /* check later that zombie is satisfied */
  }

  rmc->coin_refresh_fee = dk->meta.fee_refresh;
  rmc->coin_value = dk->meta.value;
  /* check client used sane currency */
  if (GNUNET_YES !=
      TALER_amount_cmp_currency (&rmc->refresh_session.amount_with_fee,
                                 &rmc->coin_value) )
  {
    GNUNET_break_op (0);
    return TALER_MHD_reply_with_error (
      connection,
      MHD_HTTP_BAD_REQUEST,
      TALER_EC_GENERIC_CURRENCY_MISMATCH,
      rmc->refresh_session.amount_with_fee.currency);
  }
  /* check coin is actually properly signed */
  if (GNUNET_OK !=
      TALER_test_coin_valid (&rmc->refresh_session.coin,
                             &dk->denom_pub))
  {
    GNUNET_break_op (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_FORBIDDEN,
                                       TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
                                       NULL);
  }

  /* sanity-check that "total melt amount > melt fee" */
  if (0 <
      TALER_amount_cmp (&rmc->coin_refresh_fee,
                        &rmc->refresh_session.amount_with_fee))
  {
    GNUNET_break_op (0);
    return TALER_MHD_reply_with_error (connection,
                                       MHD_HTTP_BAD_REQUEST,
                                       TALER_EC_EXCHANGE_MELT_FEES_EXCEED_CONTRIBUTION,
                                       NULL);
  }
  return handle_melt (connection,
                      rmc);
}


/**
 * Handle a "/coins/$COIN_PUB/melt" request.  Parses the request into the JSON
 * components and then hands things of to #check_for_denomination_key() to
 * validate the melted coins, the signature and execute the melt using
 * handle_melt().

 * @param connection the MHD connection to handle
 * @param coin_pub public key of the coin
 * @param root uploaded JSON data
 * @return MHD result code
 */
MHD_RESULT
TEH_handler_melt (struct MHD_Connection *connection,
                  const struct TALER_CoinSpendPublicKeyP *coin_pub,
                  const json_t *root)
{
  struct MeltContext rmc;
  enum GNUNET_GenericReturnValue ret;
  MHD_RESULT res;
  struct GNUNET_JSON_Specification spec[] = {
    TALER_JSON_spec_denomination_signature ("denom_sig",
                                            &rmc.refresh_session.coin.denom_sig),
    GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
                                 &rmc.refresh_session.coin.denom_pub_hash),
    GNUNET_JSON_spec_fixed_auto ("confirm_sig",
                                 &rmc.refresh_session.coin_sig),
    TALER_JSON_spec_amount ("value_with_fee",
                            &rmc.refresh_session.amount_with_fee),
    GNUNET_JSON_spec_fixed_auto ("rc",
                                 &rmc.refresh_session.rc),
    GNUNET_JSON_spec_end ()
  };

  memset (&rmc,
          0,
          sizeof (rmc));
  rmc.refresh_session.coin.coin_pub = *coin_pub;
  ret = TALER_MHD_parse_json_data (connection,
                                   root,
                                   spec);
  if (GNUNET_OK != ret)
    return (GNUNET_SYSERR == ret) ? MHD_NO : MHD_YES;

  res = check_for_denomination_key (connection,
                                    &rmc);
  GNUNET_JSON_parse_free (spec);
  return res;
}


/* end of taler-exchange-httpd_melt.c */