/*
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 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
*/
/**
* @file taler-exchange-httpd_melt.c
* @brief Handle melt requests
* @author Florian Dold
* @author Benedikt Mueller
* @author Christian Grothoff
*/
#include "platform.h"
#include
#include
#include
#include "taler_json_lib.h"
#include "taler_mhd_lib.h"
#include "taler-exchange-httpd_mhd.h"
#include "taler-exchange-httpd_melt.h"
#include "taler-exchange-httpd_responses.h"
#include "taler-exchange-httpd_keys.h"
#include "taler_exchangedb_lib.h"
/**
* Send a response for a failed "melt" request. The
* transaction history of the given coin demonstrates that the
* @a residual value of the coin is below the @a requested
* contribution of the coin for the melt. Thus, the exchange
* refuses the melt operation.
*
* @param connection the connection to send the response to
* @param coin_pub public key of the coin
* @param coin_value original value of the coin
* @param tl transaction history for the coin
* @param requested how much this coin was supposed to contribute, including fee
* @param residual remaining value of the coin (after subtracting @a tl)
* @return a MHD result code
*/
static MHD_RESULT
reply_melt_insufficient_funds (
struct MHD_Connection *connection,
const struct TALER_CoinSpendPublicKeyP *coin_pub,
const struct TALER_Amount *coin_value,
struct TALER_EXCHANGEDB_TransactionList *tl,
const struct TALER_Amount *requested,
const struct TALER_Amount *residual)
{
json_t *history;
history = TEH_RESPONSE_compile_transaction_history (coin_pub,
tl);
if (NULL == history)
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_MELT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS,
NULL);
return TALER_MHD_REPLY_JSON_PACK (
connection,
MHD_HTTP_CONFLICT,
TALER_JSON_pack_ec (TALER_EC_EXCHANGE_MELT_INSUFFICIENT_FUNDS),
GNUNET_JSON_pack_data_auto ("coin_pub",
coin_pub),
TALER_JSON_pack_amount ("original_value",
coin_value),
TALER_JSON_pack_amount ("residual_value",
residual),
TALER_JSON_pack_amount ("requested_value",
requested),
GNUNET_JSON_pack_array_steal ("history",
history));
}
/**
* Send a response to a "melt" request.
*
* @param connection the connection to send the response to
* @param rc value the client committed to
* @param noreveal_index which index will the client not have to reveal
* @return a MHD status code
*/
static MHD_RESULT
reply_melt_success (struct MHD_Connection *connection,
const struct TALER_RefreshCommitmentP *rc,
uint32_t noreveal_index)
{
struct TALER_ExchangePublicKeyP pub;
struct TALER_ExchangeSignatureP sig;
struct TALER_RefreshMeltConfirmationPS body = {
.purpose.size = htonl (sizeof (body)),
.purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_MELT),
.rc = *rc,
.noreveal_index = htonl (noreveal_index)
};
enum TALER_ErrorCode ec;
if (TALER_EC_NONE !=
(ec = TEH_keys_exchange_sign (&body,
&pub,
&sig)))
{
return TALER_MHD_reply_with_ec (connection,
ec,
NULL);
}
return TALER_MHD_REPLY_JSON_PACK (
connection,
MHD_HTTP_OK,
GNUNET_JSON_pack_uint64 ("noreveal_index",
noreveal_index),
GNUNET_JSON_pack_data_auto ("exchange_sig",
&sig),
GNUNET_JSON_pack_data_auto ("exchange_pub",
&pub));
}
/**
* Context for the melt operation.
*/
struct MeltContext
{
/**
* noreveal_index is only initialized during
* #melt_transaction().
*/
struct TALER_EXCHANGEDB_Refresh refresh_session;
/**
* Information about the @e coin's value.
*/
struct TALER_Amount coin_value;
/**
* Information about the @e coin's refresh fee.
*/
struct TALER_Amount coin_refresh_fee;
/**
* Set to true if this coin's denomination was revoked and the operation
* is thus only allowed for zombie coins where the transaction
* history includes a #TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP.
*/
bool zombie_required;
/**
* We already checked and noticed that the coin is known. Hence we
* can skip the "ensure_coin_known" step of the transaction.
*/
bool coin_is_dirty;
};
/**
* Check that the coin has sufficient funds left for the selected
* melt operation.
*
* @param connection the connection to send errors to
* @param[in,out] rmc melt context
* @param[out] mhd_ret status code to return to MHD on hard error
* @return transaction status code
*/
static enum GNUNET_DB_QueryStatus
refresh_check_melt (struct MHD_Connection *connection,
struct MeltContext *rmc,
MHD_RESULT *mhd_ret)
{
struct TALER_EXCHANGEDB_TransactionList *tl;
struct TALER_Amount spent;
enum GNUNET_DB_QueryStatus qs;
/* Start with cost of this melt transaction */
spent = rmc->refresh_session.amount_with_fee;
/* get historic transaction costs of this coin, including recoups as
we might be a zombie coin */
qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
&rmc->refresh_session.coin.coin_pub,
GNUNET_YES,
&tl);
if (0 > 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,
"coin transaction history");
return qs;
}
if (rmc->zombie_required)
{
/* The denomination key is only usable for a melt if this is a true
zombie coin, i.e. it was refreshed and the resulting fresh coin was
then recouped. Check that this is truly the case. */
for (struct TALER_EXCHANGEDB_TransactionList *tp = tl;
NULL != tp;
tp = tp->next)
{
if (TALER_EXCHANGEDB_TT_OLD_COIN_RECOUP == tp->type)
{
rmc->zombie_required = false; /* clear flag: was satisfied! */
break;
}
}
if (rmc->zombie_required)
{
/* zombie status not satisfied */
GNUNET_break_op (0);
TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
tl);
*mhd_ret = TALER_MHD_reply_with_error (connection,
MHD_HTTP_BAD_REQUEST,
TALER_EC_EXCHANGE_MELT_COIN_EXPIRED_NO_ZOMBIE,
NULL);
return GNUNET_DB_STATUS_HARD_ERROR;
}
}
if (GNUNET_OK !=
TALER_EXCHANGEDB_calculate_transaction_list_totals (tl,
&spent,
&spent))
{
GNUNET_break (0);
TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
tl);
*mhd_ret = TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_MELT_COIN_HISTORY_COMPUTATION_FAILED,
NULL);
return GNUNET_DB_STATUS_HARD_ERROR;
}
/* Refuse to refresh when the coin's value is insufficient
for the cost of all transactions. */
if (0 > TALER_amount_cmp (&rmc->coin_value,
&spent))
{
struct TALER_Amount coin_residual;
struct TALER_Amount spent_already;
/* First subtract the melt cost from 'spent' to
compute the total amount already spent of the coin */
GNUNET_assert (0 <=
TALER_amount_subtract (&spent_already,
&spent,
&rmc->refresh_session.amount_with_fee));
/* The residual coin value is the original coin value minus
what we have spent (before the melt) */
GNUNET_assert (0 <=
TALER_amount_subtract (&coin_residual,
&rmc->coin_value,
&spent_already));
*mhd_ret = reply_melt_insufficient_funds (
connection,
&rmc->refresh_session.coin.coin_pub,
&rmc->coin_value,
tl,
&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);
return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
}
/**
* Execute a "melt". We have been given a list of valid
* coins and a request to melt them into the given @a
* refresh_session_pub. Check that the coins all have the required
* value left and if so, store that they have been melted and confirm
* the melting operation to the client.
*
* 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.
*
* @param cls our `struct MeltContext`
* @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
melt_transaction (void *cls,
struct MHD_Connection *connection,
MHD_RESULT *mhd_ret)
{
struct MeltContext *rmc = cls;
enum GNUNET_DB_QueryStatus qs;
uint32_t noreveal_index;
/* First, make sure coin is 'known' in database */
if (! rmc->coin_is_dirty)
{
qs = TEH_make_coin_known (&rmc->refresh_session.coin,
connection,
mhd_ret);
if (qs < 0)
return qs;
}
/* Check if we already created a matching refresh_session */
qs = TEH_plugin->get_melt_index (TEH_plugin->cls,
&rmc->refresh_session.rc,
&noreveal_index);
if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
{
TALER_LOG_DEBUG ("Coin was previously melted, returning old reply\n");
*mhd_ret = reply_melt_success (connection,
&rmc->refresh_session.rc,
noreveal_index);
/* Note: we return "hard error" to ensure the wrapper
does not retry the transaction, and to also not generate
a "fresh" response (as we would on "success") */
return GNUNET_DB_STATUS_HARD_ERROR;
}
if (0 > 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,
"melt index");
return qs;
}
/* check coin has enough funds remaining on it to cover melt cost */
qs = refresh_check_melt (connection,
rmc,
mhd_ret);
if (0 > qs)
return qs; /* if we failed, tell caller */
/* 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,
&rmc->refresh_session)))
{
if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
{
*mhd_ret = TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_GENERIC_DB_STORE_FAILED,
"melt");
return GNUNET_DB_STATUS_HARD_ERROR;
}
return qs;
}
return GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
}
/**
* Handle a "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
* operation. This function parses the JSON arrays and then passes
* processing on to #melt_transaction().
*
* @param connection the MHD connection to handle
* @param[in,out] rmc details about the melt request
* @return MHD result code
*/
static MHD_RESULT
handle_melt (struct MHD_Connection *connection,
struct MeltContext *rmc)
{
/* verify signature of coin for melt operation */
{
struct TALER_RefreshMeltCoinAffirmationPS body = {
.purpose.size = htonl (sizeof (body)),
.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT),
.rc = rmc->refresh_session.rc,
.h_denom_pub = rmc->refresh_session.coin.denom_pub_hash,
.coin_pub = rmc->refresh_session.coin.coin_pub
};
TALER_amount_hton (&body.amount_with_fee,
&rmc->refresh_session.amount_with_fee);
TALER_amount_hton (&body.melt_fee,
&rmc->coin_refresh_fee);
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (
TALER_SIGNATURE_WALLET_COIN_MELT,
&body,
&rmc->refresh_session.coin_sig.eddsa_signature,
&rmc->refresh_session.coin.coin_pub.eddsa_pub))
{
GNUNET_break_op (0);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_FORBIDDEN,
TALER_EC_EXCHANGE_MELT_COIN_SIGNATURE_INVALID,
NULL);
}
}
/* run database transaction */
{
MHD_RESULT mhd_ret;
if (GNUNET_OK !=
TEH_DB_run_transaction (connection,
"run melt",
&mhd_ret,
&melt_transaction,
rmc))
return mhd_ret;
}
/* Success. Generate ordinary response. */
return reply_melt_success (connection,
&rmc->refresh_session.rc,
rmc->refresh_session.noreveal_index);
}
/**
* Check for information about the melted coin's denomination,
* extracting its validity status and fee structure.
*
* @param connection HTTP connection we are handling
* @param rmc parsed request information
* @return MHD status code
*/
static MHD_RESULT
check_for_denomination_key (struct MHD_Connection *connection,
struct MeltContext *rmc)
{
/* Baseline: check if deposits/refreshs are generally
simply still allowed for this denomination */
struct TEH_DenominationKey *dk;
MHD_RESULT mret;
dk = TEH_keys_denomination_by_hash (
&rmc->refresh_session.coin.denom_pub_hash,
connection,
&mret);
if (NULL == dk)
return mret;
if (GNUNET_TIME_absolute_is_past (dk->meta.expire_legal))
{
struct GNUNET_TIME_Absolute now;
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* Way too late now, even zombies have expired */
return TEH_RESPONSE_reply_expired_denom_pub_hash (
connection,
&rmc->refresh_session.coin.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
"MELT");
}
if (GNUNET_TIME_absolute_is_future (dk->meta.start))
{
struct GNUNET_TIME_Absolute now;
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* This denomination is not yet valid */
return TEH_RESPONSE_reply_expired_denom_pub_hash (
connection,
&rmc->refresh_session.coin.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_VALIDITY_IN_FUTURE,
"MELT");
}
if (GNUNET_TIME_absolute_is_past (dk->meta.expire_deposit))
{
/* We are past deposit expiration time, but maybe this is a zombie? */
struct TALER_DenominationHash denom_hash;
enum GNUNET_DB_QueryStatus qs;
/* Check that the coin is dirty (we have seen it before), as we will
not just allow melting of a *fresh* coin where the denomination was
revoked (those must be recouped) */
qs = TEH_plugin->get_coin_denomination (
TEH_plugin->cls,
&rmc->refresh_session.coin.coin_pub,
&denom_hash);
if (0 > qs)
{
/* There is no good reason for a serialization failure here: */
GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_GENERIC_DB_FETCH_FAILED,
"coin denomination");
}
/* sanity check */
GNUNET_break (0 ==
GNUNET_memcmp (&denom_hash,
&rmc->refresh_session.coin.denom_pub_hash));
if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
{
struct GNUNET_TIME_Absolute now;
now = GNUNET_TIME_absolute_get ();
(void) GNUNET_TIME_round_abs (&now);
/* We never saw this coin before, so _this_ justification is not OK */
return TEH_RESPONSE_reply_expired_denom_pub_hash (
connection,
&rmc->refresh_session.coin.denom_pub_hash,
now,
TALER_EC_EXCHANGE_GENERIC_DENOMINATION_EXPIRED,
"MELT");
}
else
{
/* Minor optimization: no need to run the
"ensure_coin_known" part of the transaction */
rmc->coin_is_dirty = true;
}
rmc->zombie_required = true; /* check later that zombie is satisfied */
}
rmc->coin_refresh_fee = dk->meta.fee_refresh;
rmc->coin_value = dk->meta.value;
/* check coin is actually properly signed */
if (GNUNET_OK !=
TALER_test_coin_valid (&rmc->refresh_session.coin,
&dk->denom_pub))
{
GNUNET_break_op (0);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_FORBIDDEN,
TALER_EC_EXCHANGE_DENOMINATION_SIGNATURE_INVALID,
NULL);
}
/* sanity-check that "total melt amount > melt fee" */
if (0 <
TALER_amount_cmp (&rmc->coin_refresh_fee,
&rmc->refresh_session.amount_with_fee))
{
GNUNET_break_op (0);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_BAD_REQUEST,
TALER_EC_EXCHANGE_MELT_FEES_EXCEED_CONTRIBUTION,
NULL);
}
return handle_melt (connection,
rmc);
}
/**
* Handle a "/coins/$COIN_PUB/melt" request. Parses the request into the JSON
* components and then hands things of to #check_for_denomination_key() to
* validate the melted coins, the signature and execute the melt using
* handle_melt().
* @param connection the MHD connection to handle
* @param coin_pub public key of the coin
* @param root uploaded JSON data
* @return MHD result code
*/
MHD_RESULT
TEH_handler_melt (struct MHD_Connection *connection,
const struct TALER_CoinSpendPublicKeyP *coin_pub,
const json_t *root)
{
struct MeltContext rmc;
enum GNUNET_GenericReturnValue ret;
MHD_RESULT res;
struct GNUNET_JSON_Specification spec[] = {
TALER_JSON_spec_denom_sig ("denom_sig",
&rmc.refresh_session.coin.denom_sig),
GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
&rmc.refresh_session.coin.denom_pub_hash),
GNUNET_JSON_spec_fixed_auto ("confirm_sig",
&rmc.refresh_session.coin_sig),
TALER_JSON_spec_amount ("value_with_fee",
TEH_currency,
&rmc.refresh_session.amount_with_fee),
GNUNET_JSON_spec_fixed_auto ("rc",
&rmc.refresh_session.rc),
GNUNET_JSON_spec_end ()
};
memset (&rmc,
0,
sizeof (rmc));
rmc.refresh_session.coin.coin_pub = *coin_pub;
ret = TALER_MHD_parse_json_data (connection,
root,
spec);
if (GNUNET_OK != ret)
return (GNUNET_SYSERR == ret) ? MHD_NO : MHD_YES;
res = check_for_denomination_key (connection,
&rmc);
GNUNET_JSON_parse_free (spec);
return res;
}
/* end of taler-exchange-httpd_melt.c */