aboutsummaryrefslogtreecommitdiff
path: root/src/lib/exchange_api_withdraw.c
blob: 47c050829e389bf58c0e09ef41867130b3dbcdfe (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
/*
  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_withdraw.c
 * @brief Implementation of the /reserves/$RESERVE_PUB/withdraw requests
 * @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_exchange_service.h"
#include "taler_json_lib.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"


/**
 * @brief A Withdraw Handle
 */
struct TALER_EXCHANGE_WithdrawHandle
{

  /**
   * 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_WithdrawCallback cb;

  /**
   * Secrets of the planchet.
   */
  struct TALER_PlanchetSecretsP ps;

  /**
   * Denomination key we are withdrawing.
   */
  struct TALER_EXCHANGE_DenomPublicKey pk;

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

  /**
   * Hash of the public key of the coin we are signing.
   */
  struct GNUNET_HashCode c_hash;

  /**
   * Public key of the reserve we are withdrawing from.
   */
  struct TALER_ReservePublicKeyP reserve_pub;

};


/**
 * We got a 200 OK response for the /reserves/$RESERVE_PUB/withdraw operation.
 * Extract the coin's signature and return it to the caller.  The signature we
 * get from the exchange is for the blinded value.  Thus, we first must
 * unblind it and then should verify its validity against our coin's hash.
 *
 * If everything checks out, we return the unblinded signature
 * to the application via the callback.
 *
 * @param wh operation handle
 * @param json reply from the exchange
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on errors
 */
static int
reserve_withdraw_ok (struct TALER_EXCHANGE_WithdrawHandle *wh,
                     const json_t *json)
{
  struct GNUNET_CRYPTO_RsaSignature *blind_sig;
  struct TALER_FreshCoin fc;
  struct GNUNET_JSON_Specification spec[] = {
    GNUNET_JSON_spec_rsa_signature ("ev_sig",
                                    &blind_sig),
    GNUNET_JSON_spec_end ()
  };

  if (GNUNET_OK !=
      GNUNET_JSON_parse (json,
                         spec,
                         NULL, NULL))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (GNUNET_OK !=
      TALER_planchet_to_coin (&wh->pk.key,
                              blind_sig,
                              &wh->ps,
                              &wh->c_hash,
                              &fc))
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    return GNUNET_SYSERR;
  }
  GNUNET_JSON_parse_free (spec);

  /* signature is valid, return it to the application */
  wh->cb (wh->cb_cls,
          MHD_HTTP_OK,
          TALER_EC_NONE,
          &fc.sig,
          json);
  /* make sure callback isn't called again after return */
  wh->cb = NULL;
  GNUNET_CRYPTO_rsa_signature_free (fc.sig.rsa_signature);
  return GNUNET_OK;
}


/**
 * We got a 409 CONFLICT response for the /reserves/$RESERVE_PUB/withdraw operation.
 * Check the signatures on the withdraw transactions in the provided
 * history and that the balances add up.  We don't do anything directly
 * with the information, as the JSON will be returned to the application.
 * However, our job is ensuring that the exchange followed the protocol, and
 * this in particular means checking all of the signatures in the history.
 *
 * @param wh operation handle
 * @param json reply from the exchange
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on errors
 */
static int
reserve_withdraw_payment_required (struct
                                   TALER_EXCHANGE_WithdrawHandle *wh,
                                   const json_t *json)
{
  struct TALER_Amount balance;
  struct TALER_Amount balance_from_history;
  struct TALER_Amount requested_amount;
  json_t *history;
  size_t len;
  struct GNUNET_JSON_Specification spec[] = {
    TALER_JSON_spec_amount ("balance", &balance),
    GNUNET_JSON_spec_end ()
  };

  if (GNUNET_OK !=
      GNUNET_JSON_parse (json,
                         spec,
                         NULL, NULL))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  history = json_object_get (json,
                             "history");
  if (NULL == history)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }

  /* go over transaction history and compute
     total incoming and outgoing amounts */
  len = json_array_size (history);
  {
    struct TALER_EXCHANGE_ReserveHistory *rhistory;

    /* Use heap allocation as "len" may be very big and thus this may
       not fit on the stack. Use "GNUNET_malloc_large" as a malicious
       exchange may theoretically try to crash us by giving a history
       that does not fit into our memory. */
    rhistory = GNUNET_malloc_large (sizeof (struct
                                            TALER_EXCHANGE_ReserveHistory)
                                    * len);
    if (NULL == rhistory)
    {
      GNUNET_break (0);
      return GNUNET_SYSERR;
    }

    if (GNUNET_OK !=
        TALER_EXCHANGE_parse_reserve_history (wh->exchange,
                                              history,
                                              &wh->reserve_pub,
                                              balance.currency,
                                              &balance_from_history,
                                              len,
                                              rhistory))
    {
      GNUNET_break_op (0);
      TALER_EXCHANGE_free_reserve_history (rhistory,
                                           len);
      return GNUNET_SYSERR;
    }
    TALER_EXCHANGE_free_reserve_history (rhistory,
                                         len);
  }

  if (0 !=
      TALER_amount_cmp (&balance_from_history,
                        &balance))
  {
    /* exchange cannot add up balances!? */
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  /* Compute how much we expected to charge to the reserve */
  if (GNUNET_OK !=
      TALER_amount_add (&requested_amount,
                        &wh->pk.value,
                        &wh->pk.fee_withdraw))
  {
    /* Overflow here? Very strange, our CPU must be fried... */
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  /* Check that funds were really insufficient */
  if (0 >= TALER_amount_cmp (&requested_amount,
                             &balance))
  {
    /* Requested amount is smaller or equal to reported balance,
       so this should not have failed. */
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Function called when we're done processing the
 * HTTP /reserves/$RESERVE_PUB/withdraw request.
 *
 * @param cls the `struct TALER_EXCHANGE_WithdrawHandle`
 * @param response_code HTTP response code, 0 on error
 * @param response parsed JSON result, NULL on error
 */
static void
handle_reserve_withdraw_finished (void *cls,
                                  long response_code,
                                  const void *response)
{
  struct TALER_EXCHANGE_WithdrawHandle *wh = cls;
  const json_t *j = response;

  wh->job = NULL;
  switch (response_code)
  {
  case 0:
    break;
  case MHD_HTTP_OK:
    if (GNUNET_OK !=
        reserve_withdraw_ok (wh,
                             j))
    {
      GNUNET_break_op (0);
      response_code = 0;
    }
    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 */
    break;
  case MHD_HTTP_CONFLICT:
    /* The exchange says that the reserve has insufficient funds;
       check the signatures in the history... */
    if (GNUNET_OK !=
        reserve_withdraw_payment_required (wh,
                                           j))
    {
      GNUNET_break_op (0);
      response_code = 0;
    }
    break;
  case MHD_HTTP_FORBIDDEN:
    GNUNET_break (0);
    /* 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:
    /* Nothing really to verify, the exchange basically just says
       that it doesn't know this reserve.  Can happen if we
       query before the wire transfer went through.
       We should simply pass the JSON reply to the application. */
    break;
  case MHD_HTTP_INTERNAL_SERVER_ERROR:
    /* Server had an internal issue; we should retry, but this API
       leaves this to the application */
    break;
  default:
    /* unexpected response code */
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u\n",
                (unsigned int) response_code);
    GNUNET_break (0);
    response_code = 0;
    break;
  }
  if (NULL != wh->cb)
  {
    wh->cb (wh->cb_cls,
            response_code,
            TALER_JSON_get_error_code (j),
            NULL,
            j);
    wh->cb = NULL;
  }
  TALER_EXCHANGE_withdraw_cancel (wh);
}


/**
 * Helper function for #TALER_EXCHANGE_withdraw2() and
 * #TALER_EXCHANGE_withdraw().
 *
 * @param exchange the exchange handle; the exchange must be ready to operate
 * @param pk kind of coin to create
 * @param reserve_sig signature from the reserve authorizing the withdrawal
 * @param reserve_pub public key of the reserve to withdraw from
 * @param ps secrets of the planchet
 *        caller must have committed this value to disk before the call (with @a pk)
 * @param pd planchet details matching @a ps
 * @param res_cb the callback to call when the final result for this request is available
 * @param res_cb_cls closure for @a res_cb
 * @return NULL
 *         if the inputs are invalid (i.e. denomination key not with this exchange).
 *         In this case, the callback is not called.
 */
struct TALER_EXCHANGE_WithdrawHandle *
reserve_withdraw_internal (struct TALER_EXCHANGE_Handle *exchange,
                           const struct TALER_EXCHANGE_DenomPublicKey *pk,
                           const struct TALER_ReserveSignatureP *reserve_sig,
                           const struct TALER_ReservePublicKeyP *reserve_pub,
                           const struct TALER_PlanchetSecretsP *ps,
                           const struct TALER_PlanchetDetail *pd,
                           TALER_EXCHANGE_WithdrawCallback res_cb,
                           void *res_cb_cls)
{
  struct TALER_EXCHANGE_WithdrawHandle *wh;
  struct GNUNET_CURL_Context *ctx;
  json_t *withdraw_obj;
  CURL *eh;
  struct GNUNET_HashCode h_denom_pub;
  char arg_str[sizeof (struct TALER_ReservePublicKeyP) * 2 + 32];

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

    end = GNUNET_STRINGS_data_to_string (reserve_pub,
                                         sizeof (struct
                                                 TALER_ReservePublicKeyP),
                                         pub_str,
                                         sizeof (pub_str));
    *end = '\0';
    GNUNET_snprintf (arg_str,
                     sizeof (arg_str),
                     "/reserves/%s/withdraw",
                     pub_str);
  }
  wh = GNUNET_new (struct TALER_EXCHANGE_WithdrawHandle);
  wh->exchange = exchange;
  wh->cb = res_cb;
  wh->cb_cls = res_cb_cls;
  wh->pk = *pk;
  wh->pk.key.rsa_public_key
    = GNUNET_CRYPTO_rsa_public_key_dup (pk->key.rsa_public_key);
  wh->reserve_pub = *reserve_pub;
  wh->c_hash = pd->c_hash;
  GNUNET_CRYPTO_rsa_public_key_hash (pk->key.rsa_public_key,
                                     &h_denom_pub);
  withdraw_obj = json_pack ("{s:o, s:o," /* denom_pub_hash and coin_ev */
                            " s:o}",/* reserve_pub and reserve_sig */
                            "denom_pub_hash", GNUNET_JSON_from_data_auto (
                              &h_denom_pub),
                            "coin_ev", GNUNET_JSON_from_data (pd->coin_ev,
                                                              pd->coin_ev_size),
                            "reserve_sig", GNUNET_JSON_from_data_auto (
                              reserve_sig));
  if (NULL == withdraw_obj)
  {
    GNUNET_break (0);
    GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key);
    GNUNET_free (wh);
    return NULL;
  }
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Attempting to withdraw from reserve %s\n",
              TALER_B2S (reserve_pub));
  wh->ps = *ps;
  wh->url = TEAH_path_to_url (exchange,
                              arg_str);
  eh = TALER_EXCHANGE_curl_easy_get_ (wh->url);
  if (GNUNET_OK !=
      TALER_curl_easy_post (&wh->ctx,
                            eh,
                            withdraw_obj))
  {
    GNUNET_break (0);
    curl_easy_cleanup (eh);
    json_decref (withdraw_obj);
    GNUNET_free (wh->url);
    GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key);
    GNUNET_free (wh);
    return NULL;
  }
  json_decref (withdraw_obj);
  ctx = TEAH_handle_to_context (exchange);
  wh->job = GNUNET_CURL_job_add2 (ctx,
                                  eh,
                                  wh->ctx.headers,
                                  &handle_reserve_withdraw_finished,
                                  wh);
  return wh;
}


/**
 * Withdraw a coin from the exchange using a /reserve/withdraw request.  Note
 * that to ensure that no money is lost in case of hardware failures,
 * the caller must have committed (most of) the arguments to disk
 * before calling, and be ready to repeat the request with the same
 * arguments in case of failures.
 *
 * @param exchange the exchange handle; the exchange must be ready to operate
 * @param pk kind of coin to create
 * @param reserve_priv private key of the reserve to withdraw from
 * @param ps secrets of the planchet
 *        caller must have committed this value to disk before the call (with @a pk)
 * @param res_cb the callback to call when the final result for this request is available
 * @param res_cb_cls closure for the above callback
 * @return handle for the operation on success, NULL on error, i.e.
 *         if the inputs are invalid (i.e. denomination key not with this exchange).
 *         In this case, the callback is not called.
 */
struct TALER_EXCHANGE_WithdrawHandle *
TALER_EXCHANGE_withdraw (struct TALER_EXCHANGE_Handle *exchange,
                         const struct TALER_EXCHANGE_DenomPublicKey *pk,
                         const struct
                         TALER_ReservePrivateKeyP *reserve_priv,
                         const struct TALER_PlanchetSecretsP *ps,
                         TALER_EXCHANGE_WithdrawCallback
                         res_cb,
                         void *res_cb_cls)
{
  struct TALER_Amount amount_with_fee;
  struct TALER_ReserveSignatureP reserve_sig;
  struct TALER_WithdrawRequestPS req;
  struct TALER_PlanchetDetail pd;
  struct TALER_EXCHANGE_WithdrawHandle *wh;

  GNUNET_CRYPTO_eddsa_key_get_public (&reserve_priv->eddsa_priv,
                                      &req.reserve_pub.eddsa_pub);
  req.purpose.size = htonl (sizeof (struct TALER_WithdrawRequestPS));
  req.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW);
  if (GNUNET_OK !=
      TALER_amount_add (&amount_with_fee,
                        &pk->fee_withdraw,
                        &pk->value))
  {
    /* exchange gave us denomination keys that overflow like this!? */
    GNUNET_break_op (0);
    return NULL;
  }
  TALER_amount_hton (&req.amount_with_fee,
                     &amount_with_fee);
  TALER_amount_hton (&req.withdraw_fee,
                     &pk->fee_withdraw);
  if (GNUNET_OK !=
      TALER_planchet_prepare (&pk->key,
                              ps,
                              &pd))
  {
    GNUNET_break_op (0);
    return NULL;
  }
  req.h_denomination_pub = pd.denom_pub_hash;
  GNUNET_CRYPTO_hash (pd.coin_ev,
                      pd.coin_ev_size,
                      &req.h_coin_envelope);
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CRYPTO_eddsa_sign (&reserve_priv->eddsa_priv,
                                           &req.purpose,
                                           &reserve_sig.eddsa_signature));
  wh = reserve_withdraw_internal (exchange,
                                  pk,
                                  &reserve_sig,
                                  &req.reserve_pub,
                                  ps,
                                  &pd,
                                  res_cb,
                                  res_cb_cls);
  GNUNET_free (pd.coin_ev);
  return wh;
}


/**
 * Withdraw a coin from the exchange using a /reserve/withdraw
 * request.  This API is typically used by a wallet to withdraw a tip
 * where the reserve's signature was created by the merchant already.
 *
 * Note that to ensure that no money is lost in case of hardware
 * failures, the caller must have committed (most of) the arguments to
 * disk before calling, and be ready to repeat the request with the
 * same arguments in case of failures.
 *
 * @param exchange the exchange handle; the exchange must be ready to operate
 * @param pk kind of coin to create
 * @param reserve_sig signature from the reserve authorizing the withdrawal
 * @param reserve_pub public key of the reserve to withdraw from
 * @param ps secrets of the planchet
 *        caller must have committed this value to disk before the call (with @a pk)
 * @param res_cb the callback to call when the final result for this request is available
 * @param res_cb_cls closure for @a res_cb
 * @return NULL
 *         if the inputs are invalid (i.e. denomination key not with this exchange).
 *         In this case, the callback is not called.
 */
struct TALER_EXCHANGE_WithdrawHandle *
TALER_EXCHANGE_withdraw2 (struct TALER_EXCHANGE_Handle *exchange,
                          const struct
                          TALER_EXCHANGE_DenomPublicKey *pk,
                          const struct
                          TALER_ReserveSignatureP *reserve_sig,
                          const struct
                          TALER_ReservePublicKeyP *reserve_pub,
                          const struct TALER_PlanchetSecretsP *ps,
                          TALER_EXCHANGE_WithdrawCallback
                          res_cb,
                          void *res_cb_cls)
{
  struct TALER_EXCHANGE_WithdrawHandle *wh;
  struct TALER_PlanchetDetail pd;

  if (GNUNET_OK !=
      TALER_planchet_prepare (&pk->key,
                              ps,
                              &pd))
  {
    GNUNET_break_op (0);
    return NULL;
  }
  wh = reserve_withdraw_internal (exchange,
                                  pk,
                                  reserve_sig,
                                  reserve_pub,
                                  ps,
                                  &pd,
                                  res_cb,
                                  res_cb_cls);
  GNUNET_free (pd.coin_ev);
  return wh;
}


/**
 * Cancel a withdraw status request.  This function cannot be used
 * on a request handle if a response is already served for it.
 *
 * @param wh the withdraw sign request handle
 */
void
TALER_EXCHANGE_withdraw_cancel (struct TALER_EXCHANGE_WithdrawHandle *wh)
{
  if (NULL != wh->job)
  {
    GNUNET_CURL_job_cancel (wh->job);
    wh->job = NULL;
  }
  GNUNET_free (wh->url);
  TALER_curl_easy_post_finished (&wh->ctx);
  GNUNET_CRYPTO_rsa_public_key_free (wh->pk.key.rsa_public_key);
  GNUNET_free (wh);
}