/*
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_keystate.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 int
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_REFRESH_MELT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS,
"Failed to compile transaction history");
return TALER_MHD_reply_json_pack (connection,
MHD_HTTP_CONFLICT,
"{s:s, s:I, s:o, s:o, s:o, s:o, s:o}",
"hint",
"insufficient funds",
"code",
(json_int_t)
TALER_EC_REFRESH_MELT_INSUFFICIENT_FUNDS,
"coin_pub",
GNUNET_JSON_from_data_auto (coin_pub),
"original_value",
TALER_JSON_from_amount (coin_value),
"residual_value",
TALER_JSON_from_amount (residual),
"requested_value",
TALER_JSON_from_amount (requested),
"history",
history);
}
/**
* Send a response to a "melt" request.
*
* @param connection the connection to send the response to
* @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_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)
};
if (GNUNET_OK !=
TEH_KS_sign (&body.purpose,
&pub,
&sig))
{
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_BAD_CONFIGURATION,
"no keys");
}
return TALER_MHD_reply_json_pack (
connection,
MHD_HTTP_OK,
"{s:i, s:o, s:o}",
"noreveal_index", (int) noreveal_index,
"exchange_sig", GNUNET_JSON_from_data_auto (&sig),
"exchange_pub", GNUNET_JSON_from_data_auto (&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 #GNUNET_YES 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.
*/
int zombie_required;
};
/**
* 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
* @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 TALER_EXCHANGEDB_Session *session,
struct MeltContext *rmc,
int *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,
session,
&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_REFRESH_MELT_DB_FETCH_ERROR,
"failed to fetch old coin 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 = GNUNET_NO; /* clear flag: was satisfied! */
break;
}
}
if (GNUNET_YES == 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_REFRESH_MELT_COIN_EXPIRED_NO_ZOMBIE,
"denomination expired");
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_REFRESH_MELT_COIN_HISTORY_COMPUTATION_FAILED,
"failed to compute coin transaction history");
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;
GNUNET_assert (GNUNET_SYSERR !=
TALER_amount_subtract (&coin_residual,
&spent,
&rmc->refresh_session.amount_with_fee));
*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 session database session to use
* @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,
struct TALER_EXCHANGEDB_Session *session,
int *mhd_ret)
{
struct MeltContext *rmc = cls;
enum GNUNET_DB_QueryStatus qs;
uint32_t noreveal_index;
/* Check if we already created a matching refresh_session */
qs = TEH_plugin->get_melt_index (TEH_plugin->cls,
session,
&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_REFRESH_MELT_DB_FETCH_ERROR,
"failed to fetch melt index");
return qs;
}
/* check coin has enough funds remaining on it to cover melt cost */
qs = refresh_check_melt (connection,
session,
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,
session,
&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_REFRESH_MELT_DB_STORE_SESSION_ERROR,
"failed to persist melt data");
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 int
handle_melt (struct MHD_Connection *connection,
struct MeltContext *rmc)
{
/* verify signature of coin for melt operation */
{
struct TALER_RefreshMeltCoinAffirmationPS body;
body.purpose.size = htonl (sizeof (struct
TALER_RefreshMeltCoinAffirmationPS));
body.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_MELT);
body.rc = rmc->refresh_session.rc;
TALER_amount_hton (&body.amount_with_fee,
&rmc->refresh_session.amount_with_fee);
TALER_amount_hton (&body.melt_fee,
&rmc->coin_refresh_fee);
body.coin_pub = rmc->refresh_session.coin.coin_pub;
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (
TALER_SIGNATURE_WALLET_COIN_MELT,
&body.purpose,
&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_REFRESH_MELT_COIN_SIGNATURE_INVALID,
"confirm_sig");
}
}
/* run database transaction */
{
int 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 int
check_for_denomination_key (struct MHD_Connection *connection,
struct MeltContext *rmc)
{
struct TEH_KS_StateHandle *key_state;
int coin_is_dirty = GNUNET_NO;
key_state = TEH_KS_acquire (GNUNET_TIME_absolute_get ());
if (NULL == key_state)
{
TALER_LOG_ERROR ("Lacking keys to operate\n");
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_INTERNAL_SERVER_ERROR,
TALER_EC_EXCHANGE_BAD_CONFIGURATION,
"no keys");
}
{
/* Baseline: check if deposits/refreshs are generally
simply still allowed for this denomination */
struct TALER_EXCHANGEDB_DenominationKey *dki;
unsigned int hc;
enum TALER_ErrorCode ec;
dki = TEH_KS_denomination_key_lookup_by_hash (
key_state,
&rmc->refresh_session.coin.denom_pub_hash,
TEH_KS_DKU_DEPOSIT,
&ec,
&hc);
/* Consider case that denomination was revoked but
this coin was already seen and thus refresh is OK. */
if (NULL == dki)
{
dki = TEH_KS_denomination_key_lookup_by_hash (
key_state,
&rmc->refresh_session.coin.denom_pub_hash,
TEH_KS_DKU_RECOUP,
&ec,
&hc);
if (NULL != dki)
{
struct GNUNET_HashCode 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,
NULL,
&rmc->refresh_session.coin.coin_pub,
&denom_hash);
if (0 > qs)
{
TEH_KS_release (key_state);
/* 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_REFRESH_MELT_DB_FETCH_ERROR,
"failed to find information about old coin");
}
/* sanity check */
GNUNET_break (0 ==
GNUNET_memcmp (&denom_hash,
&rmc->refresh_session.coin.denom_pub_hash));
if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
{
/* We never saw this coin before, so _this_ justification is not OK */
dki = NULL;
}
else
{
/* Minor optimization: no need to run the
#TEH_DB_know_coin_transaction below */
coin_is_dirty = GNUNET_YES;
}
}
}
/* Consider the case that the denomination expired for deposits, but
recoup of a refreshed coin refilled the balance of the 'zombie' coin
and we should thus allow the refresh during the legal period. */
if (NULL == dki)
{
dki = TEH_KS_denomination_key_lookup_by_hash (key_state,
&rmc->refresh_session.coin.
denom_pub_hash,
TEH_KS_DKU_ZOMBIE,
&ec,
&hc);
if (NULL != dki)
rmc->zombie_required = GNUNET_YES; /* check later that zombie is satisfied */
}
if (NULL == dki)
{
TEH_KS_release (key_state);
return TALER_MHD_reply_with_error (connection,
hc,
ec,
"unknown denomination");
}
TALER_amount_ntoh (&rmc->coin_refresh_fee,
&dki->issue.properties.fee_refresh);
TALER_amount_ntoh (&rmc->coin_value,
&dki->issue.properties.value);
/* check client used sane currency */
if (GNUNET_YES !=
TALER_amount_cmp_currency (&rmc->refresh_session.amount_with_fee,
&rmc->coin_value) )
{
GNUNET_break_op (0);
TEH_KS_release (key_state);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_BAD_REQUEST,
TALER_EC_MELT_CURRENCY_MISSMATCH,
"value_with_fee");
}
/* check coin is actually properly signed */
if (GNUNET_OK !=
TALER_test_coin_valid (&rmc->refresh_session.coin,
&dki->denom_pub))
{
GNUNET_break_op (0);
TEH_KS_release (key_state);
return TALER_MHD_reply_with_error (connection,
MHD_HTTP_FORBIDDEN,
TALER_EC_REFRESH_MELT_DENOMINATION_SIGNATURE_INVALID,
"denom_sig");
}
}
TEH_KS_release (key_state);
/* run actual logic, now that the request was parsed */
/* First, make sure coin is 'known' in database */
if (GNUNET_NO == coin_is_dirty)
{
struct TEH_DB_KnowCoinContext kcc;
int mhd_ret;
kcc.coin = &rmc->refresh_session.coin;
kcc.connection = connection;
if (GNUNET_OK !=
TEH_DB_run_transaction (connection,
"know coin for melt",
&mhd_ret,
&TEH_DB_know_coin_transaction,
&kcc))
return mhd_ret;
}
/* 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_REFRESH_MELT_FEES_EXCEED_CONTRIBUTION,
"melt amount smaller than melting fee");
}
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
*/
int
TEH_handler_melt (struct MHD_Connection *connection,
const struct TALER_CoinSpendPublicKeyP *coin_pub,
const json_t *root)
{
struct MeltContext rmc;
int res;
struct GNUNET_JSON_Specification spec[] = {
TALER_JSON_spec_denomination_signature ("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",
&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;
res = TALER_MHD_parse_json_data (connection,
root,
spec);
if (GNUNET_OK != res)
return (GNUNET_SYSERR == res) ? 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 */