fixing #5178

1 files changed, 137 insertions, 569 deletions

diff --git a/src/exchange/taler-exchange-httpd_refresh_melt.c b/src/exchange/taler-exchange-httpd_refresh_melt.c
index 320ec9d8b..400d2bb8c 100644
--- a/src/exchange/taler-exchange-httpd_refresh_melt.c
+++ b/src/exchange/taler-exchange-httpd_refresh_melt.c
@@ -32,38 +32,6 @@
 
 
 /**
- * @brief Details about a melt operation of an individual coin.
- */
-struct TEH_DB_MeltDetails
-{
-
-  /**
-   * Information about the coin being melted.
-   */
-  struct TALER_CoinPublicInfo coin_info;
-
-  /**
-   * Signature allowing the melt (using
-   * a `struct TALER_EXCHANGEDB_RefreshMeltConfirmSignRequestBody`) to sign over.
-   */
-  struct TALER_CoinSpendSignatureP melt_sig;
-
-  /**
-   * How much of the coin's value did the client allow to be melted?
-   * This amount includes the fees, so the final amount contributed
-   * to the melt is this value minus the fee for melting the coin.
-   */
-  struct TALER_Amount melt_amount_with_fee;
-
-  /**
-   * What fee is earned by the exchange?  Set delayed during
-   * #verify_coin_public_info().
-   */
-  struct TALER_Amount melt_fee;
-};
-
-
-/**
  * Send a response for a failed "/refresh/melt" request.  The
  * transaction history of the given coin demonstrates that the
  * @a residual value of the coin is below the @a requested
@@ -116,14 +84,14 @@ reply_refresh_melt_insufficient_funds (struct MHD_Connection *connection,
  * Send a response to a "/refresh/melt" request.
  *
  * @param connection the connection to send the response to
- * @param session_hash hash of the refresh session
+ * @param rc value the client commited to
  * @param noreveal_index which index will the client not have to reveal
  * @return a MHD status code
  */
 static int
 reply_refresh_melt_success (struct MHD_Connection *connection,
-			    const struct GNUNET_HashCode *session_hash,
-			    uint16_t noreveal_index)
+			    const struct TALER_RefreshCommitmentP *rc,
+			    uint32_t noreveal_index)
 {
   struct TALER_RefreshMeltConfirmationPS body;
   struct TALER_ExchangePublicKeyP pub;
@@ -132,9 +100,8 @@ reply_refresh_melt_success (struct MHD_Connection *connection,
 
   body.purpose.size = htonl (sizeof (struct TALER_RefreshMeltConfirmationPS));
   body.purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_MELT);
-  body.session_hash = *session_hash;
-  body.noreveal_index = htons (noreveal_index);
-  body.reserved = htons (0);
+  body.rc = *rc;
+  body.noreveal_index = htonl (noreveal_index);
   if (GNUNET_OK !=
       TEH_KS_sign (&body.purpose,
 		   &pub,
@@ -162,63 +129,22 @@ struct RefreshMeltContext
 {
 
   /**
-   * Key state that can be used to lookup keys.
+   * noreveal_index is only initialized during
+   * #refresh_melt_transaction().
    */
-  struct TEH_KS_StateHandle *key_state;
+  struct TALER_EXCHANGEDB_RefreshSession refresh_session;
 
   /**
-   * Information about the denomination key of the coin being
-   * melted.
+   * Information about the @e coin's denomination.
    */
   struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
 
-  /**
-   * Array of denominations of the fresh coins.
-   */
-  struct TALER_DenominationPublicKey *denom_pubs;
-
-  /**
-   * Number of new coins to be generated in the melt.
-   * Size of the @e denom_pubs array.
-   */
-  unsigned int num_newcoins;
-
-  /**
-   * Details about the coin to be melted.
-   */
-  struct TEH_DB_MeltDetails coin_melt_details;
-
-  /**
-   * Set to the session hash once the @e hash_context has finished.
-   */
-  struct GNUNET_HashCode session_hash;
-
-  /**
-   * Hash operation used to calculate the session hash.
-   */
-  struct GNUNET_HashContext *hash_context;
-
-  /**
-   * Committments to the blinded envelopes for the fresh coins.
-   */
-  struct TALER_EXCHANGEDB_RefreshCommitCoin *commit_coin[TALER_CNC_KAPPA];
-
-  /**
-   * Commmittments to the transfer public keys.
-   */
-  struct TALER_TransferPublicKeyP transfer_pub[TALER_CNC_KAPPA];
-
-  /**
-   * Initialized during #refresh_melt_transaction().
-   */
-  struct TALER_EXCHANGEDB_RefreshSession refresh_session;
-
 };
 
 
 /**
- * Parse coin melt requests from a JSON object and write them to
- * the database.
+ * Check that the coin has sufficient funds left for the selected
+ * melt operation.
  *
  * @param connection the connection to send errors to
  * @param session the database connection
@@ -233,20 +159,19 @@ refresh_check_melt (struct MHD_Connection *connection,
 		    int *mhd_ret)
 {
   struct TALER_EXCHANGEDB_TransactionList *tl;
-  struct TALER_EXCHANGEDB_RefreshMelt *meltp = &rmc->refresh_session.melt;
   struct TALER_Amount coin_value;
-  struct TALER_Amount coin_residual;
   struct TALER_Amount spent;
   enum GNUNET_DB_QueryStatus qs;
 
   TALER_amount_ntoh (&coin_value,
                      &rmc->dki->issue.properties.value);
-  /* fee for THIS transaction; the melt amount includes the fee! */
-  spent = rmc->coin_melt_details.melt_amount_with_fee;
+  /* Start with cost of this melt transaction */
+  spent = rmc->refresh_session.amount_with_fee;
+
   /* add historic transaction costs of this coin */
   qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
                                           session,
-                                          &rmc->coin_melt_details.coin_info.coin_pub,
+                                          &rmc->refresh_session.coin.coin_pub,
 					  &tl);
   if (0 > qs)
   {
@@ -267,33 +192,32 @@ refresh_check_melt (struct MHD_Connection *connection,
 						     TALER_EC_REFRESH_MELT_COIN_HISTORY_COMPUTATION_FAILED);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
+
   /* Refuse to refresh when the coin's value is insufficient
      for the cost of all transactions. */
   if (TALER_amount_cmp (&coin_value,
                         &spent) < 0)
   {
+    struct TALER_Amount coin_residual;
+
     GNUNET_assert (GNUNET_SYSERR !=
                    TALER_amount_subtract (&coin_residual,
                                           &spent,
-                                          &rmc->coin_melt_details.melt_amount_with_fee));
+                                          &rmc->refresh_session.amount_with_fee));
     *mhd_ret = reply_refresh_melt_insufficient_funds (connection,
-						      &rmc->coin_melt_details.coin_info.coin_pub,
+						      &rmc->refresh_session.coin.coin_pub,
 						      coin_value,
 						      tl,
-						      &rmc->coin_melt_details.melt_amount_with_fee,
+						      &rmc->refresh_session.amount_with_fee,
 						      &coin_residual);
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
+
+  /* we're good, coin has sufficient funds to be melted */
   TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                           tl);
-
-  meltp->coin = rmc->coin_melt_details.coin_info;
-  meltp->coin_sig = rmc->coin_melt_details.melt_sig;
-  meltp->session_hash = rmc->session_hash;
-  meltp->amount_with_fee = rmc->coin_melt_details.melt_amount_with_fee;
-  meltp->melt_fee = rmc->coin_melt_details.melt_fee;
   return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
 }
 
@@ -325,17 +249,19 @@ refresh_melt_transaction (void *cls,
 			  int *mhd_ret)
 {
   struct RefreshMeltContext *rmc = cls;
+  struct TALER_EXCHANGEDB_RefreshMelt rm;
   enum GNUNET_DB_QueryStatus qs;
 
-  qs = TEH_plugin->get_refresh_session (TEH_plugin->cls,
-					session,
-					&rmc->session_hash,
-					&rmc->refresh_session);
+  /* Check if we already created such a session */
+  qs = TEH_plugin->get_melt (TEH_plugin->cls,
+                             session,
+                             &rmc->refresh_session.rc,
+                             &rm);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
   {
     *mhd_ret = reply_refresh_melt_success (connection,
-					   &rmc->session_hash,
-					   rmc->refresh_session.noreveal_index);
+					   &rmc->refresh_session.rc,
+					   rm.session.noreveal_index);
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
   if (0 > qs)
@@ -346,12 +272,7 @@ refresh_melt_transaction (void *cls,
     return qs;
   }
 
-  /* store 'global' session data */
-  rmc->refresh_session.num_newcoins = rmc->num_newcoins;
-  rmc->refresh_session.noreveal_index
-    = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
-				TALER_CNC_KAPPA);
-
+  /* check coin has enough funds remaining on it to cover melt cost */
   qs = refresh_check_melt (connection,
 			   session,
 			   rmc,
@@ -359,28 +280,15 @@ refresh_melt_transaction (void *cls,
   if (0 > qs)
     return qs;
 
-  if ( (0 >=
-	(qs = TEH_plugin->create_refresh_session (TEH_plugin->cls,
-						  session,
-						  &rmc->session_hash,
-						  &rmc->refresh_session))) ||
-       (0 >=
-	(qs = TEH_plugin->insert_refresh_order (TEH_plugin->cls,
-						session,
-						&rmc->session_hash,
-						rmc->num_newcoins,
-						rmc->denom_pubs))) ||
-       (0 >=
-	(qs = TEH_plugin->insert_refresh_commit_coins (TEH_plugin->cls,
-						       session,
-						       &rmc->session_hash,
-						       rmc->num_newcoins,
-						       rmc->commit_coin[rmc->refresh_session.noreveal_index]))) ||
-       (0 >=
-	(qs = TEH_plugin->insert_refresh_transfer_public_key (TEH_plugin->cls,
-							      session,
-							      &rmc->session_hash,
-							      &rmc->transfer_pub[rmc->refresh_session.noreveal_index]))) )
+  /* pick challenge and persist it */
+  rmc->refresh_session.noreveal_index
+    = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
+				TALER_CNC_KAPPA);
+
+  if (0 >=
+      (qs = TEH_plugin->insert_melt (TEH_plugin->cls,
+                                     session,
+                                     &rmc->refresh_session)))
   {
     if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
     {
@@ -395,233 +303,6 @@ refresh_melt_transaction (void *cls,
 
 
 /**
- * Handle a "/refresh/melt" request after the main JSON parsing has
- * happened.  We now need to validate the coins being melted and the
- * session signature and then hand things of to execute the melt
- * operation.
- *
- * @param connection the MHD connection to handle
- * @param[out] mhd_ret set on failure to return value for MHD
- * @param rmc information about the melt to process
- * @return MHD result code
- */
-static int
-refresh_melt_prepare (struct MHD_Connection *connection,
-		      int *mhd_ret,
-		      struct RefreshMeltContext *rmc)
-{
-  struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dk;
-  struct TALER_EXCHANGEDB_DenominationKeyInformationP *dki;
-  struct TALER_Amount cost;
-  struct TALER_Amount total_cost;
-  struct TALER_Amount value;
-  struct TALER_Amount fee_withdraw;
-  struct TALER_Amount fee_melt;
-  struct TALER_Amount total_melt;
-
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "/refresh/melt request for session %s\n",
-              GNUNET_h2s (&rmc->session_hash));
-
-  GNUNET_assert (GNUNET_OK ==
-                 TALER_amount_get_zero (TEH_exchange_currency_string,
-                                        &total_cost));
-  for (unsigned int i=0;i<rmc->num_newcoins;i++)
-  {
-    dk = TEH_KS_denomination_key_lookup (rmc->key_state,
-                                         &rmc->denom_pubs[i],
-                                         TEH_KS_DKU_WITHDRAW);
-    if (NULL == dk)
-    {
-      GNUNET_break_op (0);
-      *mhd_ret = TEH_RESPONSE_reply_arg_invalid (connection,
-						 TALER_EC_REFRESH_MELT_FRESH_DENOMINATION_KEY_NOT_FOUND,
-						 "new_denoms");
-      return GNUNET_SYSERR;
-    }
-    dki = &dk->issue;
-    TALER_amount_ntoh (&value,
-                       &dki->properties.value);
-    TALER_amount_ntoh (&fee_withdraw,
-                       &dki->properties.fee_withdraw);
-    if ( (GNUNET_OK !=
-          TALER_amount_add (&cost,
-                            &value,
-                            &fee_withdraw)) ||
-         (GNUNET_OK !=
-          TALER_amount_add (&total_cost,
-                            &cost,
-                            &total_cost)) )
-    {
-      GNUNET_break_op (0);
-      *mhd_ret = TEH_RESPONSE_reply_internal_error (connection,
-						    TALER_EC_REFRESH_MELT_COST_CALCULATION_OVERFLOW,
-						    "cost calculation failure");
-      return GNUNET_SYSERR;
-    }
-  }
-
-  dki = &rmc->dki->issue;
-  TALER_amount_ntoh (&fee_melt,
-                     &dki->properties.fee_refresh);
-  if (GNUNET_OK !=
-      TALER_amount_subtract (&total_melt,
-                             &rmc->coin_melt_details.melt_amount_with_fee,
-                             &fee_melt))
-  {
-    GNUNET_break_op (0);
-    *mhd_ret = TEH_RESPONSE_reply_external_error (connection,
-						  TALER_EC_REFRESH_MELT_FEES_EXCEED_CONTRIBUTION,
-						  "Melt contribution below melting fee");
-    return GNUNET_SYSERR;
-  }
-  if (0 !=
-      TALER_amount_cmp (&total_cost,
-                        &total_melt))
-  {
-    GNUNET_break_op (0);
-    /* We require total value of coins being melted and
-       total value of coins being generated to match! */
-    *mhd_ret = TEH_RESPONSE_reply_json_pack (connection,
-					     MHD_HTTP_BAD_REQUEST,
-					     "{s:s, s:I}",
-					     "error", "value mismatch",
-					     "code", (json_int_t) TALER_EC_REFRESH_MELT_FEES_MISSMATCH);
-    return GNUNET_SYSERR;
-  }
-  return TEH_DB_run_transaction (connection,
-				 mhd_ret,
-				 &refresh_melt_transaction,
-				 rmc);
-}
-
-
-/**
- * Extract public coin information from a JSON object.
- *
- * @param connection the connection to send error responses to
- * @param coin_info the JSON object to extract the coin info from
- * @param[out] r_melt_detail set to details about the coin's melting permission (if valid)
- * @return #GNUNET_YES if coin public info in JSON was valid
- *         #GNUNET_NO JSON was invalid, response was generated
- *         #GNUNET_SYSERR on internal error
- */
-static int
-get_coin_public_info (struct MHD_Connection *connection,
-                      const json_t *coin_info,
-                      struct TEH_DB_MeltDetails *r_melt_detail)
-{
-  int ret;
-  struct TALER_CoinSpendSignatureP melt_sig;
-  struct TALER_DenominationSignature sig;
-  struct TALER_DenominationPublicKey pk;
-  struct TALER_Amount amount;
-  struct GNUNET_JSON_Specification spec[] = {
-    GNUNET_JSON_spec_fixed_auto ("coin_pub", &r_melt_detail->coin_info.coin_pub),
-    TALER_JSON_spec_denomination_signature ("denom_sig", &sig),
-    TALER_JSON_spec_denomination_public_key ("denom_pub", &pk),
-    GNUNET_JSON_spec_fixed_auto ("confirm_sig", &melt_sig),
-    TALER_JSON_spec_amount ("value_with_fee", &amount),
-    GNUNET_JSON_spec_end ()
-  };
-
-  ret = TEH_PARSE_json_data (connection,
-                             coin_info,
-                             spec);
-  if (GNUNET_OK != ret)
-  {
-    GNUNET_break_op (0);
-    return ret;
-  }
-  /* check exchange signature on the coin */
-  r_melt_detail->coin_info.denom_sig = sig;
-  r_melt_detail->coin_info.denom_pub = pk;
-  if (GNUNET_OK !=
-      TALER_test_coin_valid (&r_melt_detail->coin_info))
-  {
-    GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    r_melt_detail->coin_info.denom_sig.rsa_signature = NULL;
-    r_melt_detail->coin_info.denom_pub.rsa_public_key = NULL;
-    return (MHD_YES ==
-            TEH_RESPONSE_reply_signature_invalid (connection,
-						  TALER_EC_REFRESH_MELT_DENOMINATION_SIGNATURE_INVALID,
-                                                  "denom_sig"))
-      ? GNUNET_NO : GNUNET_SYSERR;
-  }
-  r_melt_detail->melt_sig = melt_sig;
-  r_melt_detail->melt_amount_with_fee = amount;
-  return GNUNET_OK;
-}
-
-
-/**
- * Release memory from the @a commit_coin array.
- *
- * @param commit_coin array to release
- * @param kappa size of 1st dimension
- * @param num_new_coins size of 2nd dimension
- */
-static void
-free_commit_coins (struct TALER_EXCHANGEDB_RefreshCommitCoin **commit_coin,
-                   unsigned int kappa,
-                   unsigned int num_new_coins)
-{
-  for (unsigned int i=0;i<kappa;i++)
-  {
-    if (NULL == commit_coin[i])
-      break;
-    for (unsigned int j=0;j<num_new_coins;j++)
-      GNUNET_free_non_null (commit_coin[i][j].coin_ev);
-    GNUNET_free (commit_coin[i]);
-    commit_coin[i] = NULL;
-  }
-}
-
-
-/**
- * Cleanup state kept in the @a rmc.
- *
- * @param rmc state to clean up; does not free @a rmc itself
- */
-static void
-cleanup_rmc (struct RefreshMeltContext *rmc)
-{
-  free_commit_coins (rmc->commit_coin,
-                     TALER_CNC_KAPPA,
-                     rmc->num_newcoins);
-  if (NULL != rmc->coin_melt_details.coin_info.denom_pub.rsa_public_key)
-  {
-    GNUNET_CRYPTO_rsa_public_key_free (rmc->coin_melt_details.coin_info.denom_pub.rsa_public_key);
-    rmc->coin_melt_details.coin_info.denom_pub.rsa_public_key = NULL;
-  }
-  if (NULL != rmc->coin_melt_details.coin_info.denom_sig.rsa_signature)
-  {
-    GNUNET_CRYPTO_rsa_signature_free (rmc->coin_melt_details.coin_info.denom_sig.rsa_signature);
-    rmc->coin_melt_details.coin_info.denom_sig.rsa_signature = NULL;
-  }
-  if (NULL != rmc->denom_pubs)
-  {
-    for (unsigned int j=0;j<rmc->num_newcoins;j++)
-      if (NULL != rmc->denom_pubs[j].rsa_public_key)
-        GNUNET_CRYPTO_rsa_public_key_free (rmc->denom_pubs[j].rsa_public_key);
-    GNUNET_free (rmc->denom_pubs);
-    rmc->denom_pubs = NULL;
-  }
-  if (NULL != rmc->hash_context)
-  {
-    GNUNET_CRYPTO_hash_context_abort (rmc->hash_context);
-    rmc->hash_context = NULL;
-  }
-  if (NULL != rmc->key_state)
-  {
-    TEH_KS_release (rmc->key_state);
-    rmc->key_state = NULL;
-  }
-}
-
-
-/**
  * Handle a "/refresh/melt" request after the first parsing has
  * happened.  We now need to validate the coins being melted and the
  * session signature and then hand things of to execute the melt
@@ -629,223 +310,70 @@ cleanup_rmc (struct RefreshMeltContext *rmc)
  * processing on to #handle_refresh_melt_binary().
  *
  * @param connection the MHD connection to handle
- * @param new_denoms array of denomination keys
- * @param melt_coin coin to melt
- * @param transfer_pubs #TALER_CNC_KAPPA-dimensional array of transfer keys
- * @param coin_evs #TALER_CNC_KAPPA-dimensional array of envelopes to sign
+ * @param[in,out] rmc details about the melt request
  * @return MHD result code
  */
 static int
-handle_refresh_melt_json (struct MHD_Connection *connection,
-                          const json_t *new_denoms,
-                          const json_t *melt_coin,
-                          const json_t *transfer_pubs,
-                          const json_t *coin_evs)
+handle_refresh_melt (struct MHD_Connection *connection,
+                     struct RefreshMeltContext *rmc)
 {
-  int res;
-  int mhd_ret;
-  struct RefreshMeltContext rmc;
-
-  memset (&rmc,
-	  0,
-	  sizeof (rmc));
-  /* For the signature check, we hash most of the inputs together
-     (except for the signatures on the coins). */
-  rmc.hash_context = GNUNET_CRYPTO_hash_context_start ();
-  for (unsigned int i = 0; i < TALER_CNC_KAPPA; i++)
-  {
-    struct GNUNET_JSON_Specification trans_spec[] = {
-      GNUNET_JSON_spec_fixed_auto (NULL, &rmc.transfer_pub[i]),
-      GNUNET_JSON_spec_end ()
-    };
-
-    res = TEH_PARSE_json_array (connection,
-                                transfer_pubs,
-                                trans_spec,
-                                i, -1);
-    if (GNUNET_OK != res)
-    {
-      GNUNET_break_op (0);
-      mhd_ret = (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
-      cleanup_rmc (&rmc);
-      return mhd_ret;
-    }
-    GNUNET_CRYPTO_hash_context_read (rmc.hash_context,
-                                     &rmc.transfer_pub[i],
-                                     sizeof (struct TALER_TransferPublicKeyP));
-  }
-
-  rmc.num_newcoins = json_array_size (new_denoms);
-  rmc.denom_pubs = GNUNET_new_array (rmc.num_newcoins,
-				     struct TALER_DenominationPublicKey);
-  for (unsigned int i=0;i<rmc.num_newcoins;i++)
-  {
-    char *buf;
-    size_t buf_size;
-    struct GNUNET_JSON_Specification spec[] = {
-      TALER_JSON_spec_denomination_public_key (NULL,
-                                               &rmc.denom_pubs[i]),
-      GNUNET_JSON_spec_end ()
-    };
-
-    res = TEH_PARSE_json_array (connection,
-                                new_denoms,
-                                spec,
-                                i,
-				-1);
-    if (GNUNET_OK != res)
-    {
-      mhd_ret = (GNUNET_NO == res) ? MHD_YES : MHD_NO;
-      cleanup_rmc (&rmc);
-      return mhd_ret;
-    }
-    buf_size = GNUNET_CRYPTO_rsa_public_key_encode (rmc.denom_pubs[i].rsa_public_key,
-                                                    &buf);
-    GNUNET_CRYPTO_hash_context_read (rmc.hash_context,
-                                     buf,
-                                     buf_size);
-    GNUNET_free (buf);
-  }
-
-  /* decode JSON data on coin to melt and check that this is a
-     valid coin */
+  /* sanity-check that "total melt amount > melt fee" */
   {
-    struct TALER_AmountNBO melt_amount;
+    struct TALER_Amount fee_refresh;
 
-    res = get_coin_public_info (connection,
-                                melt_coin,
-                                &rmc.coin_melt_details);
-    if (GNUNET_OK != res)
+    TALER_amount_ntoh (&fee_refresh,
+		       &rmc->dki->issue.properties.fee_refresh);
+    if (TALER_amount_cmp (&fee_refresh,
+			  &rmc->refresh_session.amount_with_fee) > 0)
     {
       GNUNET_break_op (0);
-      mhd_ret = (GNUNET_NO == res) ? MHD_YES : MHD_NO;
-      cleanup_rmc (&rmc);
-      return mhd_ret;
-    }
-    TALER_amount_hton (&melt_amount,
-                       &rmc.coin_melt_details.melt_amount_with_fee);
-    GNUNET_CRYPTO_hash_context_read (rmc.hash_context,
-                                     &rmc.coin_melt_details.coin_info.coin_pub,
-                                     sizeof (struct TALER_CoinSpendPublicKeyP));
-    GNUNET_CRYPTO_hash_context_read (rmc.hash_context,
-                                     &melt_amount,
-                                     sizeof (struct TALER_AmountNBO));
-  }
-
-  /* parse JSON arrays into binary arrays and hash everything
-     together for the signature check */
-  for (unsigned int i = 0; i < TALER_CNC_KAPPA; i++)
-  {
-    rmc.commit_coin[i] = GNUNET_new_array (rmc.num_newcoins,
-					   struct TALER_EXCHANGEDB_RefreshCommitCoin);
-    for (unsigned int j = 0; j < rmc.num_newcoins; j++)
-    {
-      struct TALER_EXCHANGEDB_RefreshCommitCoin *rcc = &rmc.commit_coin[i][j];
-      struct GNUNET_JSON_Specification coin_spec[] = {
-        GNUNET_JSON_spec_varsize (NULL,
-                                  (void **) &rcc->coin_ev,
-                                  &rcc->coin_ev_size),
-        GNUNET_JSON_spec_end ()
-      };
-
-      res = TEH_PARSE_json_array (connection,
-                                  coin_evs,
-                                  coin_spec,
-                                  i,
-				  j,
-				  -1);
-      if (GNUNET_OK != res)
-      {
-        GNUNET_break_op (0);
-        mhd_ret = (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
-        cleanup_rmc (&rmc);
-	return mhd_ret;
-      }
-
-      GNUNET_CRYPTO_hash_context_read (rmc.hash_context,
-                                       rcc->coin_ev,
-                                       rcc->coin_ev_size);
+      return TEH_RESPONSE_reply_external_error (connection,
+						TALER_EC_REFRESH_MELT_FEES_EXCEED_CONTRIBUTION,
+						"melt amount smaller than melting fee");
     }
   }
 
-  GNUNET_CRYPTO_hash_context_finish (rmc.hash_context,
-                                     &rmc.session_hash);
-  rmc.hash_context = NULL;
-
-  rmc.key_state = TEH_KS_acquire ();
-  if (NULL == rmc.key_state)
-  {
-    TALER_LOG_ERROR ("Lacking keys to operate\n");
-    return TEH_RESPONSE_reply_internal_error (connection,
-                                              TALER_EC_EXCHANGE_BAD_CONFIGURATION,
-                                              "no keys");
-  }
-  rmc.dki = TEH_KS_denomination_key_lookup (rmc.key_state,
-					    &rmc.coin_melt_details.coin_info.denom_pub,
-					    TEH_KS_DKU_DEPOSIT);
-  if (NULL == rmc.dki)
-  {
-    TEH_KS_release (rmc.key_state);
-    TALER_LOG_WARNING ("Unknown denomination key in /refresh/melt request\n");
-    return TEH_RESPONSE_reply_arg_unknown (connection,
-					   TALER_EC_REFRESH_MELT_DENOMINATION_KEY_NOT_FOUND,
-                                           "denom_pub");
-  }
-
   /* verify signature of coin for melt operation */
   {
     struct TALER_RefreshMeltCoinAffirmationPS body;
-    struct TALER_Amount fee_refresh;
 
-    TALER_amount_ntoh (&fee_refresh,
-		       &rmc.dki->issue.properties.fee_refresh);
-    rmc.coin_melt_details.melt_fee = fee_refresh;
     body.purpose.size = htonl (sizeof (struct TALER_RefreshMeltCoinAffirmationPS));
     body.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT);
-    body.session_hash = rmc.session_hash;
+    body.rc = rmc->refresh_session.rc;
     TALER_amount_hton (&body.amount_with_fee,
-		       &rmc.coin_melt_details.melt_amount_with_fee);
-    TALER_amount_hton (&body.melt_fee,
-		       &fee_refresh);
-    body.coin_pub = rmc.coin_melt_details.coin_info.coin_pub;
-    if (TALER_amount_cmp (&fee_refresh,
-			  &rmc.coin_melt_details.melt_amount_with_fee) > 0)
-    {
-      GNUNET_break_op (0);
-      cleanup_rmc (&rmc);
-      return TEH_RESPONSE_reply_external_error (connection,
-						TALER_EC_REFRESH_MELT_AMOUNT_INSUFFICIENT,
-						"melt amount smaller than melting fee");
-    }
+		       &rmc->refresh_session.amount_with_fee);
+    body.melt_fee = rmc->dki->issue.properties.fee_refresh;
+    body.coin_pub = rmc->refresh_session.coin.coin_pub;
 
     if (GNUNET_OK !=
 	GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_MELT,
 				    &body.purpose,
-				    &rmc.coin_melt_details.melt_sig.eddsa_signature,
-				    &rmc.coin_melt_details.coin_info.coin_pub.eddsa_pub))
+				    &rmc->refresh_session.coin_sig.eddsa_signature,
+				    &rmc->refresh_session.coin.coin_pub.eddsa_pub))
     {
       GNUNET_break_op (0);
-      cleanup_rmc (&rmc);
       return TEH_RESPONSE_reply_signature_invalid (connection,
 						   TALER_EC_REFRESH_MELT_COIN_SIGNATURE_INVALID,
 						   "confirm_sig");
     }
   }
 
-  /* prepare commit */
-  if (GNUNET_OK !=
-      refresh_melt_prepare (connection,
-			    &mhd_ret,
-			    &rmc))
+  /* run transaction */
   {
-    cleanup_rmc (&rmc);
-    return mhd_ret;
+    int mhd_ret;
+
+    if (GNUNET_OK !=
+        TEH_DB_run_transaction (connection,
+                                &mhd_ret,
+                                &refresh_melt_transaction,
+                                rmc))
+      return mhd_ret;
   }
-  mhd_ret = reply_refresh_melt_success (connection,
-					&rmc.session_hash,
-					rmc.refresh_session.noreveal_index);
-  cleanup_rmc (&rmc);
-  return mhd_ret;
+
+  /* generate ordinary response */
+  return reply_refresh_melt_success (connection,
+                                     &rmc->refresh_session.rc,
+                                     rmc->refresh_session.noreveal_index);
 }
 
 
@@ -870,16 +398,22 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
                                   size_t *upload_data_size)
 {
   json_t *root;
-  json_t *new_denoms;
-  json_t *melt_coin;
-  json_t *coin_evs;
-  json_t *transfer_pubs;
+  struct RefreshMeltContext rmc;
   int res;
+  struct TEH_KS_StateHandle *key_state;
   struct GNUNET_JSON_Specification spec[] = {
-    GNUNET_JSON_spec_json ("new_denoms", &new_denoms),
-    GNUNET_JSON_spec_json ("melt_coin", &melt_coin),
-    GNUNET_JSON_spec_json ("coin_evs", &coin_evs),
-    GNUNET_JSON_spec_json ("transfer_pubs", &transfer_pubs),
+    GNUNET_JSON_spec_fixed_auto ("coin_pub",
+                                 &rmc.refresh_session.coin.coin_pub),
+    TALER_JSON_spec_denomination_signature ("denom_sig",
+                                            &rmc.refresh_session.coin.denom_sig),
+    TALER_JSON_spec_denomination_public_key ("denom_pub",
+                                             &rmc.refresh_session.coin.denom_pub),
+    GNUNET_JSON_spec_fixed_auto ("confirm_sig",
+                                 &rmc.refresh_session.coin_sig),
+    TALER_JSON_spec_amount ("value_with_fee",
+                            &rmc.refresh_session.amount_with_fee),
+    GNUNET_JSON_spec_fixed_auto ("rc",
+                                 &rmc.refresh_session.rc),
     GNUNET_JSON_spec_end ()
   };
 
@@ -894,6 +428,9 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
        (NULL == root) )
     return MHD_YES;
 
+  memset (&rmc,
+          0,
+          sizeof (rmc));
   res = TEH_PARSE_json_data (connection,
                              root,
                              spec);
@@ -901,29 +438,60 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
   if (GNUNET_OK != res)
     return (GNUNET_SYSERR == res) ? MHD_NO : MHD_YES;
 
-  /* Determine dimensionality of the request (kappa, #old and #new coins) */
-  if (TALER_CNC_KAPPA != json_array_size (coin_evs))
+  if (GNUNET_OK !=
+      TALER_test_coin_valid (&rmc.refresh_session.coin))
   {
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
-    return TEH_RESPONSE_reply_arg_invalid (connection,
-					   TALER_EC_REFRESH_MELT_CNC_COIN_ARRAY_SIZE_INVALID,
-                                           "coin_evs");
+    return TEH_RESPONSE_reply_signature_invalid (connection,
+                                                 TALER_EC_REFRESH_MELT_DENOMINATION_SIGNATURE_INVALID,
+                                                 "denom_sig");
   }
-  if (TALER_CNC_KAPPA != json_array_size (transfer_pubs))
+
+  /* run actual logic, now that the request was parsed */
+  key_state = TEH_KS_acquire ();
+  if (NULL == key_state)
   {
-    GNUNET_break_op (0);
-    GNUNET_JSON_parse_free (spec);
-    return TEH_RESPONSE_reply_arg_invalid (connection,
-					   TALER_EC_REFRESH_MELT_CNC_TRANSFER_ARRAY_SIZE_INVALID,
-                                           "transfer_pubs");
+    TALER_LOG_ERROR ("Lacking keys to operate\n");
+    res = TEH_RESPONSE_reply_internal_error (connection,
+                                             TALER_EC_EXCHANGE_BAD_CONFIGURATION,
+                                             "no keys");
+    goto cleanup;
+  }
+  rmc.dki = TEH_KS_denomination_key_lookup (key_state,
+                                            &rmc.refresh_session.coin.denom_pub,
+                                            TEH_KS_DKU_DEPOSIT);
+  if (NULL == rmc.dki)
+  {
+    TALER_LOG_WARNING ("Unknown denomination key in /refresh/melt request\n");
+    res = TEH_RESPONSE_reply_arg_unknown (connection,
+                                          TALER_EC_REFRESH_MELT_DENOMINATION_KEY_NOT_FOUND,
+                                          "denom_pub");
+    goto cleanup;
+  }
+
+  res = handle_refresh_melt (connection,
+                             &rmc);
+
+
+ cleanup:
+  if (NULL != key_state)
+  {
+    TEH_KS_release (key_state);
+    key_state = NULL;
+  }
+  if (NULL != rmc.refresh_session.coin.denom_pub.rsa_public_key)
+  {
+    GNUNET_CRYPTO_rsa_public_key_free (rmc.refresh_session.coin.denom_pub.rsa_public_key);
+    rmc.refresh_session.coin.denom_pub.rsa_public_key = NULL;
+  }
+  if (NULL != rmc.refresh_session.coin.denom_sig.rsa_signature)
+  {
+    GNUNET_CRYPTO_rsa_signature_free (rmc.refresh_session.coin.denom_sig.rsa_signature);
+    rmc.refresh_session.coin.denom_sig.rsa_signature = NULL;
   }
-  res = handle_refresh_melt_json (connection,
-                                  new_denoms,
-                                  melt_coin,
-                                  transfer_pubs,
-                                  coin_evs);
   GNUNET_JSON_parse_free (spec);
+
   return res;
 }