aboutsummaryrefslogtreecommitdiff
path: root/src/lib/exchange_api_melt.c
blob: 1da4184d21bbc11649603c48180e8411e84c6a88 (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) 2015-2023 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_melt.c
 * @brief Implementation of the /coins/$COIN_PUB/melt request
 * @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_exchange_service.h"
#include "exchange_api_common.h"
#include "exchange_api_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"
#include "exchange_api_refresh_common.h"


/**
 * @brief A /coins/$COIN_PUB/melt Handle
 */
struct TALER_EXCHANGE_MeltHandle
{

  /**
   * The keys of the this request handle will use
   */
  struct TALER_EXCHANGE_Keys *keys;

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

  /**
   * The exchange base url.
   */
  char *exchange_url;

  /**
   * Curl context.
   */
  struct GNUNET_CURL_Context *cctx;

  /**
   * 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 refresh melt failure results.
   */
  TALER_EXCHANGE_MeltCallback melt_cb;

  /**
   * Closure for @e result_cb and @e melt_failure_cb.
   */
  void *melt_cb_cls;

  /**
   * Actual information about the melt operation.
   */
  struct MeltData md;

  /**
   * The secret the entire melt operation is seeded from.
   */
  struct TALER_RefreshMasterSecretP rms;

  /**
   * Details about the characteristics of the requested melt operation.
   */
  const struct TALER_EXCHANGE_RefreshData *rd;

  /**
   * Array of `num_fresh_coins` per-coin values
   * returned from melt operation.
   */
  struct TALER_EXCHANGE_MeltBlindingDetail *mbds;

  /**
   * Handle for the preflight request, or NULL.
   */
  struct TALER_EXCHANGE_CsRMeltHandle *csr;

  /**
   * Public key of the coin being melted.
   */
  struct TALER_CoinSpendPublicKeyP coin_pub;

  /**
   * Signature affirming the melt.
   */
  struct TALER_CoinSpendSignatureP coin_sig;

  /**
   * @brief Public information about the coin's denomination key
   */
  const struct TALER_EXCHANGE_DenomPublicKey *dki;

  /**
   * Gamma value chosen by the exchange during melt.
   */
  uint32_t noreveal_index;

  /**
   * True if we need to include @e rms in our melt request.
   */
  bool send_rms;
};


/**
 * Verify that the signature on the "200 OK" response
 * from the exchange is valid.
 *
 * @param[in,out] mh melt handle
 * @param json json reply with the signature
 * @param[out] exchange_pub public key of the exchange used for the signature
 * @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
 */
static enum GNUNET_GenericReturnValue
verify_melt_signature_ok (struct TALER_EXCHANGE_MeltHandle *mh,
                          const json_t *json,
                          struct TALER_ExchangePublicKeyP *exchange_pub)
{
  struct TALER_ExchangeSignatureP exchange_sig;
  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_uint32 ("noreveal_index",
                             &mh->noreveal_index),
    GNUNET_JSON_spec_end ()
  };

  if (GNUNET_OK !=
      GNUNET_JSON_parse (json,
                         spec,
                         NULL, NULL))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  /* check that exchange signing key is permitted */
  key_state = mh->keys;
  if (GNUNET_OK !=
      TALER_EXCHANGE_test_signing_key (key_state,
                                       exchange_pub))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }

  /* check that noreveal index is in permitted range */
  if (TALER_CNC_KAPPA <= mh->noreveal_index)
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }

  if (GNUNET_OK !=
      TALER_exchange_online_melt_confirmation_verify (
        &mh->md.rc,
        mh->noreveal_index,
        exchange_pub,
        &exchange_sig))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Function called when we're done processing the
 * HTTP /coins/$COIN_PUB/melt request.
 *
 * @param cls the `struct TALER_EXCHANGE_MeltHandle`
 * @param response_code HTTP response code, 0 on error
 * @param response parsed JSON result, NULL on error
 */
static void
handle_melt_finished (void *cls,
                      long response_code,
                      const void *response)
{
  struct TALER_EXCHANGE_MeltHandle *mh = cls;
  const json_t *j = response;
  struct TALER_EXCHANGE_MeltResponse mr = {
    .hr.reply = j,
    .hr.http_status = (unsigned int) response_code
  };
  const struct TALER_EXCHANGE_Keys *keys;

  mh->job = NULL;
  keys = mh->keys;
  switch (response_code)
  {
  case 0:
    mr.hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
    break;
  case MHD_HTTP_OK:
    if (GNUNET_OK !=
        verify_melt_signature_ok (mh,
                                  j,
                                  &mr.details.ok.sign_key))
    {
      GNUNET_break_op (0);
      mr.hr.http_status = 0;
      mr.hr.ec = TALER_EC_EXCHANGE_MELT_INVALID_SIGNATURE_BY_EXCHANGE;
      break;
    }
    mr.details.ok.noreveal_index = mh->noreveal_index;
    mr.details.ok.num_mbds = mh->rd->fresh_pks_len;
    mr.details.ok.mbds = mh->mbds;
    mh->melt_cb (mh->melt_cb_cls,
                 &mr);
    mh->melt_cb = NULL;
    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 */
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    break;
  case MHD_HTTP_CONFLICT:
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    if (GNUNET_OK !=
        TALER_EXCHANGE_check_coin_conflict_ (
          keys,
          j,
          mh->dki,
          &mh->coin_pub,
          &mh->coin_sig,
          &mh->md.melted_coin.melt_amount_with_fee))
    {
      GNUNET_break_op (0);
      mr.hr.http_status = 0;
      mr.hr.ec = TALER_EC_GENERIC_REPLY_MALFORMED;
      break;
    }
    break;
  case MHD_HTTP_FORBIDDEN:
    /* Nothing really to verify, exchange says one of the signatures is
       invalid; assuming we checked them, this should never happen, we
       should pass the JSON reply to the application */
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    break;
  case MHD_HTTP_NOT_FOUND:
    /* Nothing really to verify, this should never
       happen, we should pass the JSON reply to the application */
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    break;
  case MHD_HTTP_INTERNAL_SERVER_ERROR:
    /* Server had an internal issue; we should retry, but this API
       leaves this to the application */
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    break;
  default:
    /* unexpected response code */
    mr.hr.ec = TALER_JSON_get_error_code (j);
    mr.hr.hint = TALER_JSON_get_error_hint (j);
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Unexpected response code %u/%d for exchange melt\n",
                (unsigned int) response_code,
                mr.hr.ec);
    GNUNET_break_op (0);
    break;
  }
  if (NULL != mh->melt_cb)
    mh->melt_cb (mh->melt_cb_cls,
                 &mr);
  TALER_EXCHANGE_melt_cancel (mh);
}


/**
 * Start the actual melt operation, now that we have
 * the exchange's input values.
 *
 * @param[in,out] mh melt operation to run
 * @return #GNUNET_OK if we could start the operation
 */
static enum GNUNET_GenericReturnValue
start_melt (struct TALER_EXCHANGE_MeltHandle *mh)
{
  const struct TALER_EXCHANGE_Keys *key_state;
  json_t *melt_obj;
  CURL *eh;
  char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];
  struct TALER_DenominationHashP h_denom_pub;
  struct TALER_ExchangeWithdrawValues alg_values[mh->rd->fresh_pks_len];

  for (unsigned int i = 0; i<mh->rd->fresh_pks_len; i++)
    alg_values[i] = mh->mbds[i].alg_value;
  if (GNUNET_OK !=
      TALER_EXCHANGE_get_melt_data_ (&mh->rms,
                                     mh->rd,
                                     alg_values,
                                     &mh->md))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }
  TALER_denom_pub_hash (&mh->md.melted_coin.pub_key,
                        &h_denom_pub);
  TALER_wallet_melt_sign (&mh->md.melted_coin.melt_amount_with_fee,
                          &mh->md.melted_coin.fee_melt,
                          &mh->md.rc,
                          &h_denom_pub,
                          mh->md.melted_coin.h_age_commitment,
                          &mh->md.melted_coin.coin_priv,
                          &mh->coin_sig);
  GNUNET_CRYPTO_eddsa_key_get_public (&mh->md.melted_coin.coin_priv.eddsa_priv,
                                      &mh->coin_pub.eddsa_pub);
  melt_obj = GNUNET_JSON_PACK (
    GNUNET_JSON_pack_data_auto ("denom_pub_hash",
                                &h_denom_pub),
    TALER_JSON_pack_denom_sig ("denom_sig",
                               &mh->md.melted_coin.sig),
    GNUNET_JSON_pack_data_auto ("confirm_sig",
                                &mh->coin_sig),
    TALER_JSON_pack_amount ("value_with_fee",
                            &mh->md.melted_coin.melt_amount_with_fee),
    GNUNET_JSON_pack_data_auto ("rc",
                                &mh->md.rc),
    GNUNET_JSON_pack_allow_null (
      mh->md.melted_coin.h_age_commitment
      ? GNUNET_JSON_pack_data_auto ("age_commitment_hash",
                                    mh->md.melted_coin.h_age_commitment)
      : GNUNET_JSON_pack_string ("age_commitment_hash",
                                 NULL)),
    GNUNET_JSON_pack_allow_null (
      mh->send_rms
      ? GNUNET_JSON_pack_data_auto ("rms",
                                    &mh->rms)
      : GNUNET_JSON_pack_string ("rms",
                                 NULL)));
  {
    char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
    char *end;

    end = GNUNET_STRINGS_data_to_string (
      &mh->coin_pub,
      sizeof (struct TALER_CoinSpendPublicKeyP),
      pub_str,
      sizeof (pub_str));
    *end = '\0';
    GNUNET_snprintf (arg_str,
                     sizeof (arg_str),
                     "coins/%s/melt",
                     pub_str);
  }

  key_state = mh->keys;
  mh->dki = TALER_EXCHANGE_get_denomination_key (key_state,
                                                 &mh->md.melted_coin.pub_key);

  /* and now we can at last begin the actual request handling */

  mh->url = TALER_url_join (mh->exchange_url,
                            arg_str,
                            NULL);
  if (NULL == mh->url)
  {
    json_decref (melt_obj);
    return GNUNET_SYSERR;
  }
  eh = TALER_EXCHANGE_curl_easy_get_ (mh->url);
  if ( (NULL == eh) ||
       (GNUNET_OK !=
        TALER_curl_easy_post (&mh->ctx,
                              eh,
                              melt_obj)) )
  {
    GNUNET_break (0);
    if (NULL != eh)
      curl_easy_cleanup (eh);
    json_decref (melt_obj);
    return GNUNET_SYSERR;
  }
  json_decref (melt_obj);
  mh->job = GNUNET_CURL_job_add2 (mh->cctx,
                                  eh,
                                  mh->ctx.headers,
                                  &handle_melt_finished,
                                  mh);
  return GNUNET_OK;
}


/**
 * The melt request @a mh failed, return an error to
 * the application and cancel the operation.
 *
 * @param[in] mh melt request that failed
 * @param ec error code to fail with
 */
static void
fail_mh (struct TALER_EXCHANGE_MeltHandle *mh,
         enum TALER_ErrorCode ec)
{
  struct TALER_EXCHANGE_MeltResponse mr = {
    .hr.ec = ec
  };

  mh->melt_cb (mh->melt_cb_cls,
               &mr);
  TALER_EXCHANGE_melt_cancel (mh);
}


/**
 * Callbacks of this type are used to serve the result of submitting a
 * CS R request to a exchange.
 *
 * @param cls closure with our `struct TALER_EXCHANGE_MeltHandle *`
 * @param csrr response details
 */
static void
csr_cb (void *cls,
        const struct TALER_EXCHANGE_CsRMeltResponse *csrr)
{
  struct TALER_EXCHANGE_MeltHandle *mh = cls;
  unsigned int nks_off = 0;

  mh->csr = NULL;
  if (MHD_HTTP_OK != csrr->hr.http_status)
  {
    struct TALER_EXCHANGE_MeltResponse mr = {
      .hr = csrr->hr
    };

    mr.hr.hint = "/csr-melt failed";
    mh->melt_cb (mh->melt_cb_cls,
                 &mr);
    TALER_EXCHANGE_melt_cancel (mh);
    return;
  }
  for (unsigned int i = 0; i<mh->rd->fresh_pks_len; i++)
  {
    const struct TALER_EXCHANGE_DenomPublicKey *fresh_pk =
      &mh->rd->fresh_pks[i];
    struct TALER_ExchangeWithdrawValues *wv = &mh->mbds[i].alg_value;

    switch (fresh_pk->key.cipher)
    {
    case TALER_DENOMINATION_INVALID:
      GNUNET_break (0);
      fail_mh (mh,
               TALER_EC_GENERIC_CLIENT_INTERNAL_ERROR);
      return;
    case TALER_DENOMINATION_RSA:
      GNUNET_assert (TALER_DENOMINATION_RSA == wv->cipher);
      break;
    case TALER_DENOMINATION_CS:
      GNUNET_assert (TALER_DENOMINATION_CS == wv->cipher);
      *wv = csrr->details.ok.alg_values[nks_off];
      nks_off++;
      break;
    }
  }
  mh->send_rms = true;
  if (GNUNET_OK !=
      start_melt (mh))
  {
    GNUNET_break (0);
    fail_mh (mh,
             TALER_EC_GENERIC_CLIENT_INTERNAL_ERROR);
    return;
  }
}


struct TALER_EXCHANGE_MeltHandle *
TALER_EXCHANGE_melt (
  struct GNUNET_CURL_Context *ctx,
  const char *url,
  struct TALER_EXCHANGE_Keys *keys,
  const struct TALER_RefreshMasterSecretP *rms,
  const struct TALER_EXCHANGE_RefreshData *rd,
  TALER_EXCHANGE_MeltCallback melt_cb,
  void *melt_cb_cls)
{
  struct TALER_EXCHANGE_NonceKey nks[GNUNET_NZL (rd->fresh_pks_len)];
  unsigned int nks_off = 0;
  struct TALER_EXCHANGE_MeltHandle *mh;

  if (0 == rd->fresh_pks_len)
  {
    GNUNET_break (0);
    return NULL;
  }
  mh = GNUNET_new (struct TALER_EXCHANGE_MeltHandle);
  mh->noreveal_index = TALER_CNC_KAPPA; /* invalid value */
  mh->cctx = ctx;
  mh->exchange_url = GNUNET_strdup (url);
  mh->rd = rd;
  mh->rms = *rms;
  mh->melt_cb = melt_cb;
  mh->melt_cb_cls = melt_cb_cls;
  mh->mbds = GNUNET_new_array (rd->fresh_pks_len,
                               struct TALER_EXCHANGE_MeltBlindingDetail);
  for (unsigned int i = 0; i<rd->fresh_pks_len; i++)
  {
    const struct TALER_EXCHANGE_DenomPublicKey *fresh_pk = &rd->fresh_pks[i];
    struct TALER_ExchangeWithdrawValues *wv = &mh->mbds[i].alg_value;

    switch (fresh_pk->key.cipher)
    {
    case TALER_DENOMINATION_INVALID:
      GNUNET_break (0);
      GNUNET_free (mh->mbds);
      GNUNET_free (mh);
      return NULL;
    case TALER_DENOMINATION_RSA:
      wv->cipher = TALER_DENOMINATION_RSA;
      break;
    case TALER_DENOMINATION_CS:
      wv->cipher = TALER_DENOMINATION_CS;
      nks[nks_off].pk = fresh_pk;
      nks[nks_off].cnc_num = nks_off;
      nks_off++;
      break;
    }
  }
  mh->keys = TALER_EXCHANGE_keys_incref (keys);
  if (0 != nks_off)
  {
    mh->csr = TALER_EXCHANGE_csr_melt (ctx,
                                       url,
                                       rms,
                                       nks_off,
                                       nks,
                                       &csr_cb,
                                       mh);
    if (NULL == mh->csr)
    {
      GNUNET_break (0);
      TALER_EXCHANGE_melt_cancel (mh);
      return NULL;
    }
    return mh;
  }
  if (GNUNET_OK !=
      start_melt (mh))
  {
    GNUNET_break (0);
    TALER_EXCHANGE_melt_cancel (mh);
    return NULL;
  }
  return mh;
}


void
TALER_EXCHANGE_melt_cancel (struct TALER_EXCHANGE_MeltHandle *mh)
{
  if (NULL != mh->job)
  {
    GNUNET_CURL_job_cancel (mh->job);
    mh->job = NULL;
  }
  if (NULL != mh->csr)
  {
    TALER_EXCHANGE_csr_melt_cancel (mh->csr);
    mh->csr = NULL;
  }
  TALER_EXCHANGE_free_melt_data_ (&mh->md); /* does not free 'md' itself */
  GNUNET_free (mh->mbds);
  GNUNET_free (mh->url);
  GNUNET_free (mh->exchange_url);
  TALER_curl_easy_post_finished (&mh->ctx);
  TALER_EXCHANGE_keys_decref (mh->keys);
  GNUNET_free (mh);
}


/* end of exchange_api_melt.c */