path: root/src/exchange/taler-exchange-httpd_withdraw.c

/*
  This file is part of TALER
  Copyright (C) 2014-2023 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_withdraw.c
 * @brief Handle /reserves/$RESERVE_PUB/withdraw requests
 * @author Florian Dold
 * @author Benedikt Mueller
 * @author Christian Grothoff
 */
#include "platform.h"
#include <gnunet/gnunet_util_lib.h>
#include <jansson.h>
#include "taler_json_lib.h"
#include "taler_kyclogic_lib.h"
#include "taler_mhd_lib.h"
#include "taler-exchange-httpd_withdraw.h"
#include "taler-exchange-httpd_responses.h"
#include "taler-exchange-httpd_keys.h"


/**
 * Context for #withdraw_transaction.
 */
struct WithdrawContext
{

  /**
   * Hash of the (blinded) message to be signed by the Exchange.
   */
  struct TALER_BlindedCoinHashP h_coin_envelope;

  /**
   * Blinded planchet.
   */
  struct TALER_BlindedPlanchet blinded_planchet;

  /**
   * Set to the resulting signed coin data to be returned to the client.
   */
  struct TALER_EXCHANGEDB_CollectableBlindcoin collectable;

  /**
   * KYC status for the operation.
   */
  struct TALER_EXCHANGEDB_KycStatus kyc;

  /**
   * Hash of the payto-URI representing the account
   * from which the money was put into the reserve.
   */
  struct TALER_PaytoHashP h_account_payto;

  /**
   * Current time for the DB transaction.
   */
  struct GNUNET_TIME_Timestamp now;

  /**
   * AML decision, #TALER_AML_NORMAL if we may proceed.
   */
  enum TALER_AmlDecisionState aml_decision;

};


/**
 * Function called to iterate over KYC-relevant
 * transaction amounts for a particular time range.
 * Called within a database transaction, so must
 * not start a new one.
 *
 * @param cls closure, identifies the event type and
 *        account to iterate over events for
 * @param limit maximum time-range for which events
 *        should be fetched (timestamp in the past)
 * @param cb function to call on each event found,
 *        events must be returned in reverse chronological
 *        order
 * @param cb_cls closure for @a cb
 */
static void
withdraw_amount_cb (void *cls,
                    struct GNUNET_TIME_Absolute limit,
                    TALER_EXCHANGEDB_KycAmountCallback cb,
                    void *cb_cls)
{
  struct WithdrawContext *wc = cls;
  enum GNUNET_DB_QueryStatus qs;

  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Signaling amount %s for KYC check\n",
              TALER_amount2s (&wc->collectable.amount_with_fee));
  if (GNUNET_OK !=
      cb (cb_cls,
          &wc->collectable.amount_with_fee,
          wc->now.abs_time))
    return;
  qs = TEH_plugin->select_withdraw_amounts_for_kyc_check (
    TEH_plugin->cls,
    &wc->h_account_payto,
    limit,
    cb,
    cb_cls);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
              "Got %d additional transactions for this withdrawal and limit %llu\n",
              qs,
              (unsigned long long) limit.abs_value_us);
  GNUNET_break (qs >= 0);
}


/**
 * Function called on each @a amount that was found to
 * be relevant for the AML check as it was merged into
 * the reserve.
 *
 * @param cls `struct TALER_Amount *` to total up the amounts
 * @param amount encountered transaction amount
 * @param date when was the amount encountered
 * @return #GNUNET_OK to continue to iterate,
 *         #GNUNET_NO to abort iteration
 *         #GNUNET_SYSERR on internal error (also abort itaration)
 */
static enum GNUNET_GenericReturnValue
aml_amount_cb (
  void *cls,
  const struct TALER_Amount *amount,
  struct GNUNET_TIME_Absolute date)
{
  struct TALER_Amount *total = cls;

  GNUNET_assert (0 <=
                 TALER_amount_add (total,
                                   total,
                                   amount));
  return GNUNET_OK;
}


/**
 * Function implementing withdraw transaction.  Runs the
 * transaction logic; 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.
 *
 * Note that "wc->collectable.sig" is set before entering this function as we
 * signed before entering the transaction.
 *
 * @param cls a `struct WithdrawContext *`
 * @param connection MHD request which triggered the transaction
 * @param[out] mhd_ret set to MHD response status for @a connection,
 *             if transaction failed (!)
 * @return transaction status
 */
static enum GNUNET_DB_QueryStatus
withdraw_transaction (void *cls,
                      struct MHD_Connection *connection,
                      MHD_RESULT *mhd_ret)
{
  struct WithdrawContext *wc = cls;
  enum GNUNET_DB_QueryStatus qs;
  bool found = false;
  bool balance_ok = false;
  bool nonce_ok = false;
  uint64_t ruuid;
  const struct TALER_CsNonce *nonce;
  const struct TALER_BlindedPlanchet *bp;
  struct TALER_PaytoHashP reserve_h_payto;

  wc->now = GNUNET_TIME_timestamp_get ();
  /* Do AML check: compute total merged amount and check
     against applicable AML threshold */
  {
    char *reserve_payto;

    reserve_payto = TALER_reserve_make_payto (TEH_base_url,
                                              &wc->collectable.reserve_pub);
    TALER_payto_hash (reserve_payto,
                      &reserve_h_payto);
    GNUNET_free (reserve_payto);
  }
  {
    struct TALER_Amount merge_amount;
    struct TALER_Amount threshold;
    struct GNUNET_TIME_Absolute now_minus_one_month;

    now_minus_one_month
      = GNUNET_TIME_absolute_subtract (wc->now.abs_time,
                                       GNUNET_TIME_UNIT_MONTHS);
    GNUNET_assert (GNUNET_OK ==
                   TALER_amount_set_zero (TEH_currency,
                                          &merge_amount));
    qs = TEH_plugin->select_merge_amounts_for_kyc_check (TEH_plugin->cls,
                                                         &reserve_h_payto,
                                                         now_minus_one_month,
                                                         &aml_amount_cb,
                                                         &merge_amount);
    if (qs < 0)
    {
      GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == 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,
                                               "select_merge_amounts_for_kyc_check");
      return qs;
    }
    qs = TEH_plugin->select_aml_threshold (TEH_plugin->cls,
                                           &reserve_h_payto,
                                           &wc->aml_decision,
                                           &wc->kyc,
                                           &threshold);
    if (qs < 0)
    {
      GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == 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,
                                               "select_aml_threshold");
      return qs;
    }
    if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
    {
      threshold = TEH_aml_threshold; /* use default */
      wc->aml_decision = TALER_AML_NORMAL;
    }

    switch (wc->aml_decision)
    {
    case TALER_AML_NORMAL:
      if (0 >= TALER_amount_cmp (&merge_amount,
                                 &threshold))
      {
        /* merge_amount <= threshold, continue withdraw below */
        break;
      }
      wc->aml_decision = TALER_AML_PENDING;
      qs = TEH_plugin->trigger_aml_process (TEH_plugin->cls,
                                            &reserve_h_payto,
                                            &merge_amount);
      if (qs <= 0)
      {
        GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == 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_STORE_FAILED,
                                                 "trigger_aml_process");
        return qs;
      }
      return qs;
    case TALER_AML_PENDING:
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "AML already pending, doing nothing\n");
      return qs;
    case TALER_AML_FROZEN:
      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                  "Account frozen, doing nothing\n");
      return qs;
    }
  }

  /* Check if the money came from a wire transfer */
  qs = TEH_plugin->reserves_get_origin (TEH_plugin->cls,
                                        &wc->collectable.reserve_pub,
                                        &wc->h_account_payto);
  if (qs < 0)
    return qs;
  /* If no results, reserve was created by merge, in which case no KYC check
     is required as the merge already did that. */
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
  {
    char *kyc_required;

    qs = TALER_KYCLOGIC_kyc_test_required (
      TALER_KYCLOGIC_KYC_TRIGGER_WITHDRAW,
      &wc->h_account_payto,
      TEH_plugin->select_satisfied_kyc_processes,
      TEH_plugin->cls,
      &withdraw_amount_cb,
      wc,
      &kyc_required);
    if (qs < 0)
    {
      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      {
        GNUNET_break (0);
        *mhd_ret = TALER_MHD_reply_with_error (connection,
                                               MHD_HTTP_INTERNAL_SERVER_ERROR,
                                               TALER_EC_GENERIC_DB_FETCH_FAILED,
                                               "kyc_test_required");
      }
      return qs;
    }
    if (NULL != kyc_required)
    {
      /* insert KYC requirement into DB! */
      wc->kyc.ok = false;
      qs = TEH_plugin->insert_kyc_requirement_for_account (
        TEH_plugin->cls,
        kyc_required,
        &wc->h_account_payto,
        &wc->kyc.requirement_row);
      GNUNET_free (kyc_required);
      if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      {
        GNUNET_break (0);
        *mhd_ret = TALER_MHD_reply_with_error (connection,
                                               MHD_HTTP_INTERNAL_SERVER_ERROR,
                                               TALER_EC_GENERIC_DB_STORE_FAILED,
                                               "insert_kyc_requirement_for_account");
      }
      return qs;
    }
  }
  wc->kyc.ok = true;
  bp = &wc->blinded_planchet;
  nonce = (TALER_DENOMINATION_CS == bp->cipher)
    ? &bp->details.cs_blinded_planchet.nonce
    : NULL;
  qs = TEH_plugin->do_withdraw (TEH_plugin->cls,
                                nonce,
                                &wc->collectable,
                                wc->now,
                                &found,
                                &balance_ok,
                                &nonce_ok,
                                &ruuid);
  if (0 > qs)
  {
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
    {
      GNUNET_break (0);
      *mhd_ret = TALER_MHD_reply_with_error (connection,
                                             MHD_HTTP_INTERNAL_SERVER_ERROR,
                                             TALER_EC_GENERIC_DB_FETCH_FAILED,
                                             "do_withdraw");
    }
    return qs;
  }
  if (! found)
  {
    *mhd_ret = TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_NOT_FOUND,
                                           TALER_EC_EXCHANGE_GENERIC_RESERVE_UNKNOWN,
                                           NULL);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  if (! balance_ok)
  {
    TEH_plugin->rollback (TEH_plugin->cls);
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                "Balance insufficient for /withdraw\n");
    *mhd_ret = TEH_RESPONSE_reply_reserve_insufficient_balance (
      connection,
      TALER_EC_EXCHANGE_WITHDRAW_INSUFFICIENT_FUNDS,
      &wc->collectable.amount_with_fee,
      &wc->collectable.reserve_pub);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  if (! nonce_ok)
  {
    TEH_plugin->rollback (TEH_plugin->cls);
    *mhd_ret = TALER_MHD_reply_with_error (connection,
                                           MHD_HTTP_CONFLICT,
                                           TALER_EC_EXCHANGE_WITHDRAW_NONCE_REUSE,
                                           NULL);
    return GNUNET_DB_STATUS_HARD_ERROR;
  }
  if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
    TEH_METRICS_num_success[TEH_MT_SUCCESS_WITHDRAW]++;
  return qs;
}


/**
 * Check if the @a rc is replayed and we already have an
 * answer. If so, replay the existing answer and return the
 * HTTP response.
 *
 * @param rc request context
 * @param[in,out] wc parsed request data
 * @param[out] mret HTTP status, set if we return true
 * @return true if the request is idempotent with an existing request
 *    false if we did not find the request in the DB and did not set @a mret
 */
static bool
check_request_idempotent (struct TEH_RequestContext *rc,
                          struct WithdrawContext *wc,
                          MHD_RESULT *mret)
{
  enum GNUNET_DB_QueryStatus qs;

  qs = TEH_plugin->get_withdraw_info (TEH_plugin->cls,
                                      &wc->h_coin_envelope,
                                      &wc->collectable);
  if (0 > qs)
  {
    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == qs);
    if (GNUNET_DB_STATUS_HARD_ERROR == qs)
      *mret = TALER_MHD_reply_with_error (rc->connection,
                                          MHD_HTTP_INTERNAL_SERVER_ERROR,
                                          TALER_EC_GENERIC_DB_FETCH_FAILED,
                                          "get_withdraw_info");
    return true; /* well, kind-of */
  }
  if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
    return false;
  /* generate idempotent reply */
  TEH_METRICS_num_requests[TEH_MT_REQUEST_IDEMPOTENT_WITHDRAW]++;
  *mret = TALER_MHD_REPLY_JSON_PACK (
    rc->connection,
    MHD_HTTP_OK,
    TALER_JSON_pack_blinded_denom_sig ("ev_sig",
                                       &wc->collectable.sig));
  TALER_blinded_denom_sig_free (&wc->collectable.sig);
  return true;
}


MHD_RESULT
TEH_handler_withdraw (struct TEH_RequestContext *rc,
                      const struct TALER_ReservePublicKeyP *reserve_pub,
                      const json_t *root)
{
  struct WithdrawContext wc;
  struct GNUNET_JSON_Specification spec[] = {
    GNUNET_JSON_spec_fixed_auto ("reserve_sig",
                                 &wc.collectable.reserve_sig),
    GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
                                 &wc.collectable.denom_pub_hash),
    TALER_JSON_spec_blinded_planchet ("coin_ev",
                                      &wc.blinded_planchet),
    GNUNET_JSON_spec_end ()
  };
  enum TALER_ErrorCode ec;
  struct TEH_DenominationKey *dk;

  memset (&wc,
          0,
          sizeof (wc));
  wc.collectable.reserve_pub = *reserve_pub;
  {
    enum GNUNET_GenericReturnValue res;

    res = TALER_MHD_parse_json_data (rc->connection,
                                     root,
                                     spec);
    if (GNUNET_OK != res)
      return (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
  }
  {
    MHD_RESULT mret;
    struct TEH_KeyStateHandle *ksh;

    ksh = TEH_keys_get_state ();
    if (NULL == ksh)
    {
      if (! check_request_idempotent (rc,
                                      &wc,
                                      &mret))
      {
        GNUNET_JSON_parse_free (spec);
        return TALER_MHD_reply_with_error (rc->connection,
                                           MHD_HTTP_INTERNAL_SERVER_ERROR,
                                           TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
                                           NULL);
      }
      GNUNET_JSON_parse_free (spec);
      return mret;
    }
    dk = TEH_keys_denomination_by_hash2 (ksh,
                                         &wc.collectable.denom_pub_hash,
                                         NULL,
                                         NULL);
    if (NULL == dk)
    {
      if (! check_request_idempotent (rc,
                                      &wc,
                                      &mret))
      {
        GNUNET_JSON_parse_free (spec);
        return TEH_RESPONSE_reply_unknown_denom_pub_hash (
          rc->connection,
          &wc.collectable.denom_pub_hash);
      }
      GNUNET_JSON_parse_free (spec);
      return mret;
    }
    if (GNUNET_TIME_absolute_is_past (dk->meta.expire_withdraw.abs_time))
    {
      /* This denomination is past the expiration time for withdraws */
      if (! check_request_idempotent (rc,
                                      &wc,
                                      &mret))
      {
        GNUNET_JSON_parse_free (spec);
        return TEH_RESPONSE_reply_expired_denom_pub_hash (
          rc->connection,
          &wc.collectable.denom_pub_hash,
          TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
          "WITHDRAW");
      }
      GNUNET_JSON_parse_free (spec);
      return mret;
    }
    if (GNUNET_TIME_absolute_is_future (dk->meta.start.abs_time))
    {
      /* This denomination is not yet valid, no need to check
         for idempotency! */
      GNUNET_JSON_parse_free (spec);
      return TEH_RESPONSE_reply_expired_denom_pub_hash (
        rc->connection,
        &wc.collectable.denom_pub_hash,
        TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
        "WITHDRAW");
    }
    if (dk->recoup_possible)
    {
      /* This denomination has been revoked */
      if (! check_request_idempotent (rc,
                                      &wc,
                                      &mret))
      {
        GNUNET_JSON_parse_free (spec);
        return TEH_RESPONSE_reply_expired_denom_pub_hash (
          rc->connection,
          &wc.collectable.denom_pub_hash,
          TALER_EC_EXCHANGE_GENERIC_DENOMINATION_REVOKED,
          "WITHDRAW");
      }
      GNUNET_JSON_parse_free (spec);
      return mret;
    }
    if (dk->denom_pub.cipher != wc.blinded_planchet.cipher)
    {
      /* denomination cipher and blinded planchet cipher not the same */
      GNUNET_JSON_parse_free (spec);
      return TALER_MHD_reply_with_error (rc->connection,
                                         MHD_HTTP_BAD_REQUEST,
                                         TALER_EC_EXCHANGE_GENERIC_CIPHER_MISMATCH,
                                         NULL);
    }
  }

  if (0 >
      TALER_amount_add (&wc.collectable.amount_with_fee,
                        &dk->meta.value,
                        &dk->meta.fees.withdraw))
  {
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (rc->connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_EXCHANGE_WITHDRAW_AMOUNT_FEE_OVERFLOW,
                                       NULL);
  }

  if (GNUNET_OK !=
      TALER_coin_ev_hash (&wc.blinded_planchet,
                          &wc.collectable.denom_pub_hash,
                          &wc.collectable.h_coin_envelope))
  {
    GNUNET_break (0);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (rc->connection,
                                       MHD_HTTP_INTERNAL_SERVER_ERROR,
                                       TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE,
                                       NULL);
  }

  TEH_METRICS_num_verifications[TEH_MT_SIGNATURE_EDDSA]++;
  if (GNUNET_OK !=
      TALER_wallet_withdraw_verify (&wc.collectable.denom_pub_hash,
                                    &wc.collectable.amount_with_fee,
                                    &wc.collectable.h_coin_envelope,
                                    &wc.collectable.reserve_pub,
                                    &wc.collectable.reserve_sig))
  {
    GNUNET_break_op (0);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_error (rc->connection,
                                       MHD_HTTP_FORBIDDEN,
                                       TALER_EC_EXCHANGE_WITHDRAW_RESERVE_SIGNATURE_INVALID,
                                       NULL);
  }

  {
    struct TEH_CoinSignData csd = {
      .h_denom_pub = &wc.collectable.denom_pub_hash,
      .bp = &wc.blinded_planchet
    };

    /* Sign before transaction! */
    ec = TEH_keys_denomination_sign (
      &csd,
      false,
      &wc.collectable.sig);
  }
  if (TALER_EC_NONE != ec)
  {
    GNUNET_break (0);
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                "Failed to sign coin: %d\n",
                ec);
    GNUNET_JSON_parse_free (spec);
    return TALER_MHD_reply_with_ec (rc->connection,
                                    ec,
                                    NULL);
  }

  /* run transaction */
  {
    MHD_RESULT mhd_ret;

    if (GNUNET_OK !=
        TEH_DB_run_transaction (rc->connection,
                                "run withdraw",
                                TEH_MT_REQUEST_WITHDRAW,
                                &mhd_ret,
                                &withdraw_transaction,
                                &wc))
    {
      /* Even if #withdraw_transaction() failed, it may have created a signature
         (or we might have done it optimistically above). */
      TALER_blinded_denom_sig_free (&wc.collectable.sig);
      GNUNET_JSON_parse_free (spec);
      return mhd_ret;
    }
  }

  /* Clean up and send back final response */
  GNUNET_JSON_parse_free (spec);

  if (! wc.kyc.ok)
    return TEH_RESPONSE_reply_kyc_required (rc->connection,
                                            &wc.h_account_payto,
                                            &wc.kyc);

  if (TALER_AML_NORMAL != wc.aml_decision)
    return TEH_RESPONSE_reply_aml_blocked (rc->connection,
                                           wc.aml_decision);

  {
    MHD_RESULT ret;

    ret = TALER_MHD_REPLY_JSON_PACK (
      rc->connection,
      MHD_HTTP_OK,
      TALER_JSON_pack_blinded_denom_sig ("ev_sig",
                                         &wc.collectable.sig));
    TALER_blinded_denom_sig_free (&wc.collectable.sig);
    return ret;
  }
}


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