summaryrefslogtreecommitdiff
path: root/src/lib/exchange_api_deposit.c
blob: 351fa7a105ecc4192528f0abe3819143f1b7ad2d (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
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
/*
  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 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 General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  TALER; see the file COPYING.  If not, see
  <http://www.gnu.org/licenses/>
*/
/**
 * @file lib/exchange_api_deposit.c
 * @brief Implementation of the /deposit request of the exchange's HTTP API
 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
 * @author Christian Grothoff
 */
#include "platform.h"
#include <jansson.h>
#include <microhttpd.h> /* just for HTTP status codes */
#include <gnunet/gnunet_util_lib.h>
#include <gnunet/gnunet_json_lib.h>
#include <gnunet/gnunet_curl_lib.h>
#include "taler_json_lib.h"
#include "taler_auditor_service.h"
#include "taler_exchange_service.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"


/**
 * 1:#AUDITOR_CHANCE is the probability that we report deposits
 * to the auditor.
 *
 * 20==5% of going to auditor. This is possibly still too high, but set
 * deliberately this high for testing
 */
#define AUDITOR_CHANCE 20

/**
 * @brief A Deposit Handle
 */
struct TALER_EXCHANGE_DepositHandle
{

  /**
   * The connection to exchange this request handle will use
   */
  struct TALER_EXCHANGE_Handle *exchange;

  /**
   * The url for this request.
   */
  char *url;

  /**
   * Context for #TEH_curl_easy_post(). Keeps the data that must
   * persist for Curl to make the upload.
   */
  struct TALER_CURL_PostContext ctx;

  /**
   * Handle for the request.
   */
  struct GNUNET_CURL_Job *job;

  /**
   * Function to call with the result.
   */
  TALER_EXCHANGE_DepositResultCallback cb;

  /**
   * Closure for @a cb.
   */
  void *cb_cls;

  /**
   * Information the exchange should sign in response.
   */
  struct TALER_DepositConfirmationPS depconf;

  /**
   * Exchange signature, set for #auditor_cb.
   */
  struct TALER_ExchangeSignatureP exchange_sig;

  /**
   * Exchange signing public key, set for #auditor_cb.
   */
  struct TALER_ExchangePublicKeyP exchange_pub;

  /**
   * Value of the /deposit transaction, including fee.
   */
  struct TALER_Amount amount_with_fee;

  /**
   * @brief Public information about the coin's denomination key.
   * Note that the "key" field itself has been zero'ed out.
   */
  struct TALER_EXCHANGE_DenomPublicKey dki;

  /**
   * Chance that we will inform the auditor about the deposit
   * is 1:n, where the value of this field is "n".
   */
  unsigned int auditor_chance;

};


/**
 * Function called for each auditor to give us a chance to possibly
 * launch a deposit confirmation interaction.
 *
 * @param cls closure
 * @param ah handle to the auditor
 * @param auditor_pub public key of the auditor
 * @return NULL if no deposit confirmation interaction was launched
 */
static struct TEAH_AuditorInteractionEntry *
auditor_cb (void *cls,
            struct TALER_AUDITOR_Handle *ah,
            const struct TALER_AuditorPublicKeyP *auditor_pub)
{
  struct TALER_EXCHANGE_DepositHandle *dh = cls;
  const struct TALER_EXCHANGE_Keys *key_state;
  const struct TALER_EXCHANGE_SigningPublicKey *spk;
  struct TALER_Amount amount_without_fee;
  struct TEAH_AuditorInteractionEntry *aie;

  if (0 != GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
                                     dh->auditor_chance))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                "Not providing deposit confirmation to auditor\n");
    return NULL;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Will provide deposit confirmation to auditor `%s'\n",
              TALER_B2S (auditor_pub));
  key_state = TALER_EXCHANGE_get_keys (dh->exchange);
  spk = TALER_EXCHANGE_get_signing_key_info (key_state,
                                             &dh->exchange_pub);
  if (NULL == spk)
  {
    GNUNET_break_op (0);
    return NULL;
  }
  TALER_amount_ntoh (&amount_without_fee,
                     &dh->depconf.amount_without_fee);
  aie = GNUNET_new (struct TEAH_AuditorInteractionEntry);
  aie->dch = TALER_AUDITOR_deposit_confirmation (
    ah,
    &dh->depconf.h_wire,
    &dh->depconf.h_contract_terms,
    GNUNET_TIME_absolute_ntoh (dh->depconf.exchange_timestamp),
    GNUNET_TIME_absolute_ntoh (dh->depconf.refund_deadline),
    &amount_without_fee,
    &dh->depconf.coin_pub,
    &dh->depconf.merchant,
    &dh->exchange_pub,
    &dh->exchange_sig,
    &key_state->master_pub,
    spk->valid_from,
    spk->valid_until,
    spk->valid_legal,
    &spk->master_sig,
    &TEAH_acc_confirmation_cb,
    aie);
  return aie;
}


/**
 * Verify that the signature on the "200 OK" response
 * from the exchange is valid.
 *
 * @param dh deposit handle
 * @param json json reply with the signature
 * @param[out] exchange_sig set to the exchange's signature
 * @param[out] exchange_pub set to the exchange's public key
 * @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
 */
static int
verify_deposit_signature_ok (struct TALER_EXCHANGE_DepositHandle *dh,
                             const json_t *json,
                             struct TALER_ExchangeSignatureP *exchange_sig,
                             struct TALER_ExchangePublicKeyP *exchange_pub)
{
  const struct TALER_EXCHANGE_Keys *key_state;
  struct GNUNET_JSON_Specification spec[] = {
    GNUNET_JSON_spec_fixed_auto ("exchange_sig", exchange_sig),
    GNUNET_JSON_spec_fixed_auto ("exchange_pub", exchange_pub),
    GNUNET_JSON_spec_absolute_time_nbo ("exchange_timestamp",
                                        &dh->depconf.exchange_timestamp),
    GNUNET_JSON_spec_end ()
  };

  if (GNUNET_OK !=
      GNUNET_JSON_parse (json,
                         spec,
                         NULL, NULL))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  key_state = TALER_EXCHANGE_get_keys (dh->exchange);
  if (GNUNET_OK !=
      TALER_EXCHANGE_test_signing_key (key_state,
                                       exchange_pub))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_DEPOSIT,
                                  &dh->depconf,
                                  &exchange_sig->eddsa_signature,
                                  &exchange_pub->eddsa_pub))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  dh->exchange_sig = *exchange_sig;
  dh->exchange_pub = *exchange_pub;
  TEAH_get_auditors_for_dc (dh->exchange,
                            &auditor_cb,
                            dh);
  return GNUNET_OK;
}


/**
 * Verify that the signatures on the "403 FORBIDDEN" response from the
 * exchange demonstrating customer double-spending are valid.
 *
 * @param dh deposit handle
 * @param json json reply with the signature(s) and transaction history
 * @return #GNUNET_OK if the signature(s) is valid, #GNUNET_SYSERR if not
 */
static int
verify_deposit_signature_forbidden (
  const struct TALER_EXCHANGE_DepositHandle *dh,
  const json_t *json)
{
  json_t *history;
  struct TALER_Amount total;

  history = json_object_get (json,
                             "history");
  if (GNUNET_OK !=
      TALER_EXCHANGE_verify_coin_history (&dh->dki,
                                          dh->dki.value.currency,
                                          &dh->depconf.coin_pub,
                                          history,
                                          &total))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (0 >
      TALER_amount_add (&total,
                        &total,
                        &dh->amount_with_fee))
  {
    /* clearly not OK if our transaction would have caused
       the overflow... */
    return GNUNET_OK;
  }

  if (0 >= TALER_amount_cmp (&total,
                             &dh->dki.value))
  {
    /* transaction should have still fit */
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  /* everything OK, proof of double-spending was provided */
  return GNUNET_OK;
}


/**
 * Function called when we're done processing the
 * HTTP /deposit request.
 *
 * @param cls the `struct TALER_EXCHANGE_DepositHandle`
 * @param response_code HTTP response code, 0 on error
 * @param response parsed JSON result, NULL on error
 */
static void
handle_deposit_finished (void *cls,
                         long response_code,
                         const void *response)
{
  struct TALER_EXCHANGE_DepositHandle *dh = cls;
  struct TALER_ExchangeSignatureP exchange_sig;
  struct TALER_ExchangePublicKeyP exchange_pub;
  struct TALER_ExchangeSignatureP *es = NULL;
  struct TALER_ExchangePublicKeyP *ep = NULL;
  const json_t *j = response;
  struct TALER_EXCHANGE_HttpResponse hr = {
    .reply = j,
    .http_status = (unsigned int) response_code
  };

  dh->job = NULL;
  switch (response_code)
  {
  case 0:
    hr.ec = TALER_EC_INVALID_RESPONSE;
    break;
  case MHD_HTTP_OK:
    if (GNUNET_OK !=
        verify_deposit_signature_ok (dh,
                                     j,
                                     &exchange_sig,
                                     &exchange_pub))
    {
      GNUNET_break_op (0);
      hr.http_status = 0;
      hr.ec = TALER_EC_DEPOSIT_INVALID_SIGNATURE_BY_EXCHANGE;
    }
    else
    {
      es = &exchange_sig;
      ep = &exchange_pub;
    }
    break;
  case MHD_HTTP_BAD_REQUEST:
    /* This should never happen, either us or the exchange is buggy
       (or API version conflict); just pass JSON reply to the application */
    hr.ec = TALER_JSON_get_error_code (j);
    hr.hint = TALER_JSON_get_error_hint (j);
    break;
  case MHD_HTTP_CONFLICT:
    /* Double spending; check signatures on transaction history */
    if (GNUNET_OK !=
        verify_deposit_signature_forbidden (dh,
                                            j))
    {
      GNUNET_break_op (0);
      hr.http_status = 0;
      hr.ec = TALER_EC_DEPOSIT_INVALID_SIGNATURE_BY_EXCHANGE;
    }
    else
    {
      hr.ec = TALER_JSON_get_error_code (j);
      hr.hint = TALER_JSON_get_error_hint (j);
    }
    break;
  case MHD_HTTP_FORBIDDEN:
    hr.ec = TALER_JSON_get_error_code (j);
    hr.hint = TALER_JSON_get_error_hint (j);
    /* Nothing really to verify, exchange says one of the signatures is
       invalid; as we checked them, this should never happen, we
       should pass the JSON reply to the application */
    break;
  case MHD_HTTP_NOT_FOUND:
    hr.ec = TALER_JSON_get_error_code (j);
    hr.hint = TALER_JSON_get_error_hint (j);
    /* Nothing really to verify, this should never
     happen, we should pass the JSON reply to the application */
    break;
  case MHD_HTTP_INTERNAL_SERVER_ERROR:
    hr.ec = TALER_JSON_get_error_code (j);
    hr.hint = TALER_JSON_get_error_hint (j);
    /* Server had an internal issue; we should retry, but this API
       leaves this to the application */
    break;
  default:
    /* unexpected response code */
    hr.ec = TALER_JSON_get_error_code (j);
    hr.hint = TALER_JSON_get_error_hint (j);
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u/%d\n",
                (unsigned int) response_code,
                hr.ec);
    GNUNET_break_op (0);
    break;
  }
  dh->cb (dh->cb_cls,
          &hr,
          GNUNET_TIME_absolute_ntoh (dh->depconf.exchange_timestamp),
          es,
          ep);
  TALER_EXCHANGE_deposit_cancel (dh);
}


/**
 * Verify signature information about the deposit.
 *
 * @param dki public key information
 * @param amount the amount to be deposited
 * @param h_wire hash of the merchant’s account details
 * @param h_contract_terms hash of the contact of the merchant with the customer (further details are never disclosed to the exchange)
 * @param coin_pub coin’s public key
 * @param denom_pub denomination key with which the coin is signed
 * @param denom_pub_hash hash of @a denom_pub
 * @param denom_sig exchange’s unblinded signature of the coin
 * @param timestamp timestamp when the deposit was finalized
 * @param merchant_pub the public key of the merchant (used to identify the merchant for refund requests)
 * @param refund_deadline date until which the merchant can issue a refund to the customer via the exchange (can be zero if refunds are not allowed)
 * @param coin_sig the signature made with purpose #TALER_SIGNATURE_WALLET_COIN_DEPOSIT made by the customer with the coin’s private key.
 * @return #GNUNET_OK if signatures are OK, #GNUNET_SYSERR if not
 */
static int
verify_signatures (const struct TALER_EXCHANGE_DenomPublicKey *dki,
                   const struct TALER_Amount *amount,
                   const struct GNUNET_HashCode *h_wire,
                   const struct GNUNET_HashCode *h_contract_terms,
                   const struct TALER_CoinSpendPublicKeyP *coin_pub,
                   const struct TALER_DenominationSignature *denom_sig,
                   const struct TALER_DenominationPublicKey *denom_pub,
                   const struct GNUNET_HashCode *denom_pub_hash,
                   struct GNUNET_TIME_Absolute timestamp,
                   const struct TALER_MerchantPublicKeyP *merchant_pub,
                   struct GNUNET_TIME_Absolute refund_deadline,
                   const struct TALER_CoinSpendSignatureP *coin_sig)
{
  {
    struct TALER_DepositRequestPS dr = {
      .purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_DEPOSIT),
      .purpose.size = htonl (sizeof (dr)),
      .h_contract_terms = *h_contract_terms,
      .h_wire = *h_wire,
      .wallet_timestamp = GNUNET_TIME_absolute_hton (timestamp),
      .refund_deadline = GNUNET_TIME_absolute_hton (refund_deadline),
      .merchant = *merchant_pub,
      .coin_pub = *coin_pub
    };

    TALER_amount_hton (&dr.amount_with_fee,
                       amount);
    TALER_amount_hton (&dr.deposit_fee,
                       &dki->fee_deposit);
    if (GNUNET_OK !=
        GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_DEPOSIT,
                                    &dr,
                                    &coin_sig->eddsa_signature,
                                    &coin_pub->eddsa_pub))
    {
      GNUNET_break_op (0);
      TALER_LOG_WARNING ("Invalid coin signature on /deposit request!\n");
      {
        TALER_LOG_DEBUG ("... amount_with_fee was %s\n",
                         TALER_amount2s (amount));
        TALER_LOG_DEBUG ("... deposit_fee was %s\n",
                         TALER_amount2s (&dki->fee_deposit));
      }
      return GNUNET_SYSERR;
    }
  }

  /* check coin signature */
  {
    struct TALER_CoinPublicInfo coin_info = {
      .coin_pub = *coin_pub,
      .denom_pub_hash = *denom_pub_hash,
      .denom_sig = *denom_sig
    };

    if (GNUNET_YES !=
        TALER_test_coin_valid (&coin_info,
                               denom_pub))
    {
      GNUNET_break_op (0);
      TALER_LOG_WARNING ("Invalid coin passed for /deposit\n");
      return GNUNET_SYSERR;
    }
  }

  /* Check coin does make a contribution */
  if (0 < TALER_amount_cmp (&dki->fee_deposit,
                            amount))
  {
    GNUNET_break_op (0);
    TALER_LOG_WARNING ("Deposit amount smaller than fee\n");
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Sign a deposit permission.  Function for wallets.
 *
 * @param amount the amount to be deposited
 * @param deposit_fee the deposit fee we expect to pay
 * @param h_wire hash of the merchant’s account details
 * @param h_contract_terms hash of the contact of the merchant with the customer (further details are never disclosed to the exchange)
 * @param coin_priv coin’s private key
 * @param wallet_timestamp timestamp when the contract was finalized, must not be too far in the future
 * @param merchant_pub the public key of the merchant (used to identify the merchant for refund requests)
 * @param refund_deadline date until which the merchant can issue a refund to the customer via the exchange (can be zero if refunds are not allowed); must not be after the @a wire_deadline
 * @param[out] coin_sig set to the signature made with purpose #TALER_SIGNATURE_WALLET_COIN_DEPOSIT
 */
void
TALER_EXCHANGE_deposit_permission_sign (
  const struct TALER_Amount *amount,
  const struct TALER_Amount *deposit_fee,
  const struct GNUNET_HashCode *h_wire,
  const struct GNUNET_HashCode *h_contract_terms,
  const struct TALER_CoinSpendPrivateKeyP *coin_priv,
  struct GNUNET_TIME_Absolute wallet_timestamp,
  const struct TALER_MerchantPublicKeyP *merchant_pub,
  struct GNUNET_TIME_Absolute refund_deadline,
  struct TALER_CoinSpendSignatureP *coin_sig)
{
  struct TALER_DepositRequestPS dr = {
    .purpose.size = htonl
                      (sizeof (dr)),
    .purpose.purpose = htonl
                         (TALER_SIGNATURE_WALLET_COIN_DEPOSIT),
    .h_contract_terms = *h_contract_terms,
    .h_wire = *h_wire,
    .wallet_timestamp = GNUNET_TIME_absolute_hton (wallet_timestamp),
    .refund_deadline = GNUNET_TIME_absolute_hton (refund_deadline),
    .merchant = *merchant_pub
  };

  GNUNET_assert (GNUNET_OK ==
                 GNUNET_TIME_round_abs (&wallet_timestamp));
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_TIME_round_abs (&refund_deadline));
  GNUNET_CRYPTO_eddsa_key_get_public (&coin_priv->eddsa_priv,
                                      &dr.coin_pub.eddsa_pub);
  TALER_amount_hton (&dr.amount_with_fee,
                     amount);
  TALER_amount_hton (&dr.deposit_fee,
                     deposit_fee);
  GNUNET_CRYPTO_eddsa_sign (&coin_priv->eddsa_priv,
                            &dr,
                            &coin_sig->eddsa_signature);
}


/**
 * Submit a deposit permission to the exchange and get the exchange's response.
 * Note that while we return the response verbatim to the caller for
 * further processing, we do already verify that the response is
 * well-formed (i.e. that signatures included in the response are all
 * valid).  If the exchange's reply is not well-formed, we return an
 * HTTP status code of zero to @a cb.
 *
 * We also verify that the @a coin_sig is valid for this deposit
 * request, and that the @a ub_sig is a valid signature for @a
 * coin_pub.  Also, the @a exchange must be ready to operate (i.e.  have
 * finished processing the /keys reply).  If either check fails, we do
 * NOT initiate the transaction with the exchange and instead return NULL.
 *
 * @param exchange the exchange handle; the exchange must be ready to operate
 * @param amount the amount to be deposited
 * @param wire_deadline date until which the merchant would like the exchange to settle the balance (advisory, the exchange cannot be
 *        forced to settle in the past or upon very short notice, but of course a well-behaved exchange will limit aggregation based on the advice received)
 * @param wire_details the merchant’s account details, in a format supported by the exchange
 * @param h_contract_terms hash of the contact of the merchant with the customer (further details are never disclosed to the exchange)
 * @param coin_pub coin’s public key
 * @param denom_pub denomination key with which the coin is signed
 * @param denom_sig exchange’s unblinded signature of the coin
 * @param timestamp timestamp when the contract was finalized, must not be too far in the future
 * @param merchant_pub the public key of the merchant (used to identify the merchant for refund requests)
 * @param refund_deadline date until which the merchant can issue a refund to the customer via the exchange (can be zero if refunds are not allowed); must not be after the @a wire_deadline
 * @param coin_sig the signature made with purpose #TALER_SIGNATURE_WALLET_COIN_DEPOSIT made by the customer with the coin’s private key.
 * @param cb the callback to call when a reply for this request is available
 * @param cb_cls closure for the above callback
 * @return a handle for this request; NULL if the inputs are invalid (i.e.
 *         signatures fail to verify).  In this case, the callback is not called.
 */
struct TALER_EXCHANGE_DepositHandle *
TALER_EXCHANGE_deposit (struct TALER_EXCHANGE_Handle *exchange,
                        const struct TALER_Amount *amount,
                        struct GNUNET_TIME_Absolute wire_deadline,
                        json_t *wire_details,
                        const struct GNUNET_HashCode *h_contract_terms,
                        const struct TALER_CoinSpendPublicKeyP *coin_pub,
                        const struct TALER_DenominationSignature *denom_sig,
                        const struct TALER_DenominationPublicKey *denom_pub,
                        struct GNUNET_TIME_Absolute timestamp,
                        const struct TALER_MerchantPublicKeyP *merchant_pub,
                        struct GNUNET_TIME_Absolute refund_deadline,
                        const struct TALER_CoinSpendSignatureP *coin_sig,
                        TALER_EXCHANGE_DepositResultCallback cb,
                        void *cb_cls)
{
  const struct TALER_EXCHANGE_Keys *key_state;
  const struct TALER_EXCHANGE_DenomPublicKey *dki;
  struct TALER_EXCHANGE_DepositHandle *dh;
  struct GNUNET_CURL_Context *ctx;
  json_t *deposit_obj;
  CURL *eh;
  struct GNUNET_HashCode h_wire;
  struct GNUNET_HashCode denom_pub_hash;
  struct TALER_Amount amount_without_fee;
  char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];

  {
    char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
    char *end;

    end = GNUNET_STRINGS_data_to_string (
      coin_pub,
      sizeof (struct TALER_CoinSpendPublicKeyP),
      pub_str,
      sizeof (pub_str));
    *end = '\0';
    GNUNET_snprintf (arg_str,
                     sizeof (arg_str),
                     "/coins/%s/deposit",
                     pub_str);
  }
  (void) GNUNET_TIME_round_abs (&wire_deadline);
  (void) GNUNET_TIME_round_abs (&refund_deadline);
  if (refund_deadline.abs_value_us > wire_deadline.abs_value_us)
  {
    GNUNET_break (0);
    return NULL;
  }
  GNUNET_assert (GNUNET_YES ==
                 TEAH_handle_is_ready (exchange));
  /* initialize h_wire */
  if (GNUNET_OK !=
      TALER_JSON_merchant_wire_signature_hash (wire_details,
                                               &h_wire))
  {
    GNUNET_break (0);
    return NULL;
  }
  key_state = TALER_EXCHANGE_get_keys (exchange);
  dki = TALER_EXCHANGE_get_denomination_key (key_state,
                                             denom_pub);
  if (NULL == dki)
  {
    GNUNET_break (0);
    return NULL;
  }
  if (0 >
      TALER_amount_subtract (&amount_without_fee,
                             amount,
                             &dki->fee_deposit))
  {
    GNUNET_break_op (0);
    return NULL;
  }
  GNUNET_CRYPTO_rsa_public_key_hash (denom_pub->rsa_public_key,
                                     &denom_pub_hash);
  if (GNUNET_OK !=
      verify_signatures (dki,
                         amount,
                         &h_wire,
                         h_contract_terms,
                         coin_pub,
                         denom_sig,
                         denom_pub,
                         &denom_pub_hash,
                         timestamp,
                         merchant_pub,
                         refund_deadline,
                         coin_sig))
  {
    GNUNET_break_op (0);
    return NULL;
  }

  deposit_obj = json_pack ("{s:o, s:O," /* f/wire */
                           " s:o, s:o," /* h_wire, h_contract_terms */
                           " s:o," /* denom_pub */
                           " s:o, s:o," /* ub_sig, timestamp */
                           " s:o," /* merchant_pub */
                           " s:o, s:o," /* refund_deadline, wire_deadline */
                           " s:o}",     /* coin_sig */
                           "contribution", TALER_JSON_from_amount (amount),
                           "wire", wire_details,
                           "h_wire", GNUNET_JSON_from_data_auto (&h_wire),
                           "h_contract_terms", GNUNET_JSON_from_data_auto (
                             h_contract_terms),
                           "denom_pub_hash", GNUNET_JSON_from_data_auto (
                             &denom_pub_hash),
                           "ub_sig", GNUNET_JSON_from_rsa_signature (
                             denom_sig->rsa_signature),
                           "timestamp", GNUNET_JSON_from_time_abs (timestamp),
                           "merchant_pub", GNUNET_JSON_from_data_auto (
                             merchant_pub),
                           "refund_deadline", GNUNET_JSON_from_time_abs (
                             refund_deadline),
                           "wire_transfer_deadline", GNUNET_JSON_from_time_abs (
                             wire_deadline),
                           "coin_sig", GNUNET_JSON_from_data_auto (coin_sig)
                           );
  if (NULL == deposit_obj)
  {
    GNUNET_break (0);
    return NULL;
  }

  dh = GNUNET_new (struct TALER_EXCHANGE_DepositHandle);
  dh->auditor_chance = AUDITOR_CHANCE;
  dh->exchange = exchange;
  dh->cb = cb;
  dh->cb_cls = cb_cls;
  dh->url = TEAH_path_to_url (exchange,
                              arg_str);
  dh->depconf.purpose.size = htonl (sizeof (struct
                                            TALER_DepositConfirmationPS));
  dh->depconf.purpose.purpose = htonl (
    TALER_SIGNATURE_EXCHANGE_CONFIRM_DEPOSIT);
  dh->depconf.h_contract_terms = *h_contract_terms;
  dh->depconf.h_wire = h_wire;
  /* dh->depconf.exchange_timestamp; -- initialized later from exchange reply! */
  dh->depconf.refund_deadline = GNUNET_TIME_absolute_hton (refund_deadline);
  TALER_amount_hton (&dh->depconf.amount_without_fee,
                     &amount_without_fee);
  dh->depconf.coin_pub = *coin_pub;
  dh->depconf.merchant = *merchant_pub;
  dh->amount_with_fee = *amount;
  dh->dki = *dki;
  dh->dki.key.rsa_public_key = NULL; /* lifetime not warranted, so better
                                        not copy the pointer */

  eh = TALER_EXCHANGE_curl_easy_get_ (dh->url);
  if ( (NULL == eh) ||
       (GNUNET_OK !=
        TALER_curl_easy_post (&dh->ctx,
                              eh,
                              deposit_obj)) )
  {
    GNUNET_break (0);
    if (NULL != eh)
      curl_easy_cleanup (eh);
    json_decref (deposit_obj);
    GNUNET_free (dh->url);
    GNUNET_free (dh);
    return NULL;
  }
  json_decref (deposit_obj);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "URL for deposit: `%s'\n",
              dh->url);
  ctx = TEAH_handle_to_context (exchange);
  dh->job = GNUNET_CURL_job_add2 (ctx,
                                  eh,
                                  dh->ctx.headers,
                                  &handle_deposit_finished,
                                  dh);
  return dh;
}


/**
 * Change the chance that our deposit confirmation will be given to the
 * auditor to 100%.
 *
 * @param deposit the deposit permission request handle
 */
void
TALER_EXCHANGE_deposit_force_dc (struct TALER_EXCHANGE_DepositHandle *deposit)
{
  deposit->auditor_chance = 1;
}


/**
 * Cancel a deposit permission request.  This function cannot be used
 * on a request handle if a response is already served for it.
 *
 * @param deposit the deposit permission request handle
 */
void
TALER_EXCHANGE_deposit_cancel (struct TALER_EXCHANGE_DepositHandle *deposit)
{
  if (NULL != deposit->job)
  {
    GNUNET_CURL_job_cancel (deposit->job);
    deposit->job = NULL;
  }
  GNUNET_free (deposit->url);
  TALER_curl_easy_post_finished (&deposit->ctx);
  GNUNET_free (deposit);
}


/* end of exchange_api_deposit.c */