exchange/src/lib/exchange_api_refund.c

812 lines
25 KiB
C

/*
This file is part of TALER
Copyright (C) 2014-2021 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_refund.c
* @brief Implementation of the /refund request of the exchange's HTTP API
* @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_handle.h"
#include "taler_signatures.h"
#include "exchange_api_curl_defaults.h"
/**
* @brief A Refund Handle
*/
struct TALER_EXCHANGE_RefundHandle
{
/**
* The connection to exchange this request handle will use
*/
struct TALER_EXCHANGE_Handle *exchange;
/**
* The url for this request.
*/
char *url;
/**
* 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 the result.
*/
TALER_EXCHANGE_RefundCallback cb;
/**
* Closure for @a cb.
*/
void *cb_cls;
/**
* Hash over the proposal data to identify the contract
* which is being refunded.
*/
struct TALER_PrivateContractHashP h_contract_terms;
/**
* The coin's public key. This is the value that must have been
* signed (blindly) by the Exchange.
*/
struct TALER_CoinSpendPublicKeyP coin_pub;
/**
* The Merchant's public key. Allows the merchant to later refund
* the transaction or to inquire about the wire transfer identifier.
*/
struct TALER_MerchantPublicKeyP merchant;
/**
* Merchant-generated transaction ID for the refund.
*/
uint64_t rtransaction_id;
/**
* Amount to be refunded, including refund fee charged by the
* exchange to the customer.
*/
struct TALER_Amount refund_amount;
};
/**
* Verify that the signature on the "200 OK" response
* from the exchange is valid.
*
* @param[in,out] rh refund handle (refund fee added)
* @param json json reply with the signature
* @param[out] exchange_pub set to the exchange's public key
* @param[out] exchange_sig set to the exchange's signature
* @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
*/
static enum GNUNET_GenericReturnValue
verify_refund_signature_ok (struct TALER_EXCHANGE_RefundHandle *rh,
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_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (json,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
key_state = TALER_EXCHANGE_get_keys (rh->exchange);
if (GNUNET_OK !=
TALER_EXCHANGE_test_signing_key (key_state,
exchange_pub))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (GNUNET_OK !=
TALER_exchange_online_refund_confirmation_verify (
&rh->h_contract_terms,
&rh->coin_pub,
&rh->merchant,
rh->rtransaction_id,
&rh->refund_amount,
exchange_pub,
exchange_sig))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
return GNUNET_OK;
}
/**
* Verify that the information in the "409 Conflict" response
* from the exchange is valid and indeed shows that the refund
* amount requested is too high.
*
* @param[in,out] rh refund handle (refund fee added)
* @param json json reply with the coin transaction history
* @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
*/
static enum GNUNET_GenericReturnValue
verify_conflict_history_ok (struct TALER_EXCHANGE_RefundHandle *rh,
const json_t *json)
{
json_t *history;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_json ("history",
&history),
GNUNET_JSON_spec_end ()
};
size_t len;
struct TALER_Amount dtotal;
bool have_deposit;
struct TALER_Amount rtotal;
bool have_refund;
if (GNUNET_OK !=
GNUNET_JSON_parse (json,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
len = json_array_size (history);
if (0 == len)
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
have_deposit = false;
have_refund = false;
for (size_t off = 0; off<len; off++)
{
json_t *transaction;
struct TALER_Amount amount;
const char *type;
struct GNUNET_JSON_Specification spec_glob[] = {
TALER_JSON_spec_amount_any ("amount",
&amount),
GNUNET_JSON_spec_string ("type",
&type),
GNUNET_JSON_spec_end ()
};
transaction = json_array_get (history,
off);
if (GNUNET_OK !=
GNUNET_JSON_parse (transaction,
spec_glob,
NULL, NULL))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (0 == strcasecmp (type,
"DEPOSIT"))
{
struct TALER_Amount deposit_fee;
struct TALER_MerchantWireHashP h_wire;
struct TALER_PrivateContractHashP h_contract_terms;
struct TALER_AgeCommitmentHash h_age_commitment;
bool no_hac;
// struct TALER_ExtensionContractHashP h_extensions; // FIXME!
struct TALER_DenominationHashP h_denom_pub;
struct GNUNET_TIME_Timestamp wallet_timestamp;
struct TALER_MerchantPublicKeyP merchant_pub;
struct GNUNET_TIME_Timestamp refund_deadline;
struct TALER_CoinSpendSignatureP sig;
struct GNUNET_JSON_Specification ispec[] = {
GNUNET_JSON_spec_fixed_auto ("coin_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("h_wire",
&h_wire),
GNUNET_JSON_spec_fixed_auto ("h_denom_pub",
&h_denom_pub),
GNUNET_JSON_spec_mark_optional (
GNUNET_JSON_spec_fixed_auto ("h_age_commitment",
&h_age_commitment),
&no_hac),
GNUNET_JSON_spec_timestamp ("timestamp",
&wallet_timestamp),
GNUNET_JSON_spec_timestamp ("refund_deadline",
&refund_deadline),
TALER_JSON_spec_amount_any ("deposit_fee",
&deposit_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&merchant_pub),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (transaction,
ispec,
NULL, NULL))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (GNUNET_OK !=
TALER_wallet_deposit_verify (&amount,
&deposit_fee,
&h_wire,
&h_contract_terms,
no_hac
? NULL
: &h_age_commitment,
NULL /* FIXME-OEC: h_extensions! */,
&h_denom_pub,
wallet_timestamp,
&merchant_pub,
refund_deadline,
&rh->coin_pub,
&sig))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if ( (0 != GNUNET_memcmp (&rh->h_contract_terms,
&h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->merchant,
&merchant_pub)) )
{
/* deposit information is about a different merchant/contract */
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (have_deposit)
{
/* this cannot really happen, but we conservatively support it anyway */
if (GNUNET_YES !=
TALER_amount_cmp_currency (&amount,
&dtotal))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
GNUNET_break (0 <=
TALER_amount_add (&dtotal,
&dtotal,
&amount));
}
else
{
dtotal = amount;
have_deposit = true;
}
}
else if (0 == strcasecmp (type,
"REFUND"))
{
struct TALER_MerchantSignatureP sig;
struct TALER_Amount refund_fee;
struct TALER_Amount sig_amount;
struct TALER_PrivateContractHashP h_contract_terms;
uint64_t rtransaction_id;
struct TALER_MerchantPublicKeyP merchant_pub;
struct GNUNET_JSON_Specification ispec[] = {
TALER_JSON_spec_amount_any ("refund_fee",
&refund_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&merchant_pub),
GNUNET_JSON_spec_uint64 ("rtransaction_id",
&rtransaction_id),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (transaction,
ispec,
NULL, NULL))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (0 >
TALER_amount_add (&sig_amount,
&refund_fee,
&amount))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (GNUNET_OK !=
TALER_merchant_refund_verify (&rh->coin_pub,
&h_contract_terms,
rtransaction_id,
&sig_amount,
&merchant_pub,
&sig))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if ( (0 != GNUNET_memcmp (&rh->h_contract_terms,
&h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->merchant,
&merchant_pub)) )
{
/* refund is about a different merchant/contract */
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (rtransaction_id == rh->rtransaction_id)
{
/* Eh, this shows either a dependency failure or idempotency,
but must not happen in a conflict reply. Fail! */
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (have_refund)
{
if (GNUNET_YES !=
TALER_amount_cmp_currency (&amount,
&rtotal))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
GNUNET_break (0 <=
TALER_amount_add (&rtotal,
&rtotal,
&amount));
}
else
{
rtotal = amount;
have_refund = true;
}
}
else
{
/* unexpected type, new version on server? */
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Unexpected type `%s' in response for exchange refund\n",
type);
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
}
{
if (have_refund)
{
if (0 >
TALER_amount_add (&rtotal,
&rtotal,
&rh->refund_amount))
{
GNUNET_break (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
}
else
{
rtotal = rh->refund_amount;
}
}
if (-1 == TALER_amount_cmp (&dtotal,
&rtotal))
{
/* dtotal < rtotal: good! */
GNUNET_JSON_parse_free (spec);
return GNUNET_OK;
}
/* this fails to prove a conflict */
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
/**
* Verify that the information on the "412 Dependency Failed" response
* from the exchange is valid and indeed shows that there is a refund
* transaction ID reuse going on.
*
* @param[in,out] rh refund handle (refund fee added)
* @param json json reply with the signature
* @return #GNUNET_OK if the signature is valid, #GNUNET_SYSERR if not
*/
static enum GNUNET_GenericReturnValue
verify_failed_dependency_ok (struct TALER_EXCHANGE_RefundHandle *rh,
const json_t *json)
{
json_t *h;
json_t *e;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_json ("history",
&h),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (json,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if ( (! json_is_array (h)) ||
(1 != json_array_size (h) ) )
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
e = json_array_get (h, 0);
{
struct TALER_Amount amount;
const char *type;
struct TALER_MerchantSignatureP sig;
struct TALER_Amount refund_fee;
struct TALER_PrivateContractHashP h_contract_terms;
uint64_t rtransaction_id;
struct TALER_MerchantPublicKeyP merchant_pub;
struct GNUNET_JSON_Specification ispec[] = {
TALER_JSON_spec_amount_any ("amount",
&amount),
GNUNET_JSON_spec_string ("type",
&type),
TALER_JSON_spec_amount_any ("refund_fee",
&refund_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&merchant_pub),
GNUNET_JSON_spec_uint64 ("rtransaction_id",
&rtransaction_id),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (e,
ispec,
NULL, NULL))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if (GNUNET_OK !=
TALER_merchant_refund_verify (&rh->coin_pub,
&h_contract_terms,
rtransaction_id,
&amount,
&merchant_pub,
&sig))
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
if ( (rtransaction_id != rh->rtransaction_id) ||
(0 != GNUNET_memcmp (&rh->h_contract_terms,
&h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->merchant,
&merchant_pub)) ||
(0 == TALER_amount_cmp (&rh->refund_amount,
&amount)) )
{
GNUNET_break_op (0);
GNUNET_JSON_parse_free (spec);
return GNUNET_SYSERR;
}
}
GNUNET_JSON_parse_free (spec);
return GNUNET_OK;
}
/**
* Function called when we're done processing the
* HTTP /refund request.
*
* @param cls the `struct TALER_EXCHANGE_RefundHandle`
* @param response_code HTTP response code, 0 on error
* @param response parsed JSON result, NULL on error
*/
static void
handle_refund_finished (void *cls,
long response_code,
const void *response)
{
struct TALER_EXCHANGE_RefundHandle *rh = cls;
struct TALER_ExchangePublicKeyP exchange_pub;
struct TALER_ExchangeSignatureP exchange_sig;
struct TALER_ExchangePublicKeyP *ep = NULL;
struct TALER_ExchangeSignatureP *es = NULL;
const json_t *j = response;
struct TALER_EXCHANGE_HttpResponse hr = {
.reply = j,
.http_status = (unsigned int) response_code
};
rh->job = NULL;
switch (response_code)
{
case 0:
hr.ec = TALER_EC_GENERIC_INVALID_RESPONSE;
break;
case MHD_HTTP_OK:
if (GNUNET_OK !=
verify_refund_signature_ok (rh,
j,
&exchange_pub,
&exchange_sig))
{
GNUNET_break_op (0);
hr.http_status = 0;
hr.ec = TALER_EC_EXCHANGE_REFUND_INVALID_SIGNATURE_BY_EXCHANGE;
}
else
{
ep = &exchange_pub;
es = &exchange_sig;
}
break;
case MHD_HTTP_BAD_REQUEST:
/* This should never happen, either us or the exchange is buggy
(or API version conflict); also can happen if the currency
differs (which we should obviously never support).
Just pass JSON reply to the application */
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
break;
case MHD_HTTP_FORBIDDEN:
/* Nothing really to verify, exchange says one of the signatures is
invalid; as we checked them, this should never happen, we
should pass the JSON reply to the application */
hr.ec = TALER_JSON_get_error_code (j);
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 */
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
break;
case MHD_HTTP_CONFLICT:
/* Requested total refunds exceed deposited amount */
if (GNUNET_OK !=
verify_conflict_history_ok (rh,
j))
{
GNUNET_break (0);
hr.http_status = 0;
hr.ec = TALER_EC_EXCHANGE_REFUND_INVALID_FAILURE_PROOF_BY_EXCHANGE;
hr.hint = "conflict information provided by exchange is invalid";
break;
}
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
break;
case MHD_HTTP_GONE:
/* Kind of normal: the money was already sent to the merchant
(it was too late for the refund). */
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
break;
case MHD_HTTP_PRECONDITION_FAILED:
if (GNUNET_OK !=
verify_failed_dependency_ok (rh,
j))
{
GNUNET_break (0);
hr.http_status = 0;
hr.ec = TALER_EC_EXCHANGE_REFUND_INVALID_FAILURE_PROOF_BY_EXCHANGE;
hr.hint = "failed precondition proof returned by exchange is invalid";
break;
}
/* Two different refund requests were made about the same deposit, but
carrying identical refund transaction ids. */
hr.ec = TALER_JSON_get_error_code (j);
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 */
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
break;
default:
/* unexpected response code */
GNUNET_break_op (0);
hr.ec = TALER_JSON_get_error_code (j);
hr.hint = TALER_JSON_get_error_hint (j);
GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
"Unexpected response code %u/%d for exchange refund\n",
(unsigned int) response_code,
hr.ec);
break;
}
rh->cb (rh->cb_cls,
&hr,
ep,
es);
TALER_EXCHANGE_refund_cancel (rh);
}
struct TALER_EXCHANGE_RefundHandle *
TALER_EXCHANGE_refund (
struct TALER_EXCHANGE_Handle *exchange,
const struct TALER_Amount *amount,
const struct TALER_PrivateContractHashP *h_contract_terms,
const struct TALER_CoinSpendPublicKeyP *coin_pub,
uint64_t rtransaction_id,
const struct TALER_MerchantPrivateKeyP *merchant_priv,
TALER_EXCHANGE_RefundCallback cb,
void *cb_cls)
{
struct TALER_MerchantPublicKeyP merchant_pub;
struct TALER_MerchantSignatureP merchant_sig;
struct TALER_EXCHANGE_RefundHandle *rh;
struct GNUNET_CURL_Context *ctx;
json_t *refund_obj;
CURL *eh;
char arg_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2 + 32];
GNUNET_assert (GNUNET_YES ==
TEAH_handle_is_ready (exchange));
GNUNET_CRYPTO_eddsa_key_get_public (&merchant_priv->eddsa_priv,
&merchant_pub.eddsa_pub);
TALER_merchant_refund_sign (coin_pub,
h_contract_terms,
rtransaction_id,
amount,
merchant_priv,
&merchant_sig);
{
char pub_str[sizeof (struct TALER_CoinSpendPublicKeyP) * 2];
char *end;
end = GNUNET_STRINGS_data_to_string (
coin_pub,
sizeof (struct TALER_CoinSpendPublicKeyP),
pub_str,
sizeof (pub_str));
*end = '\0';
GNUNET_snprintf (arg_str,
sizeof (arg_str),
"/coins/%s/refund",
pub_str);
}
refund_obj = GNUNET_JSON_PACK (
TALER_JSON_pack_amount ("refund_amount",
amount),
GNUNET_JSON_pack_data_auto ("h_contract_terms",
h_contract_terms),
GNUNET_JSON_pack_uint64 ("rtransaction_id",
rtransaction_id),
GNUNET_JSON_pack_data_auto ("merchant_pub",
&merchant_pub),
GNUNET_JSON_pack_data_auto ("merchant_sig",
&merchant_sig));
rh = GNUNET_new (struct TALER_EXCHANGE_RefundHandle);
rh->exchange = exchange;
rh->cb = cb;
rh->cb_cls = cb_cls;
rh->url = TEAH_path_to_url (exchange,
arg_str);
if (NULL == rh->url)
{
json_decref (refund_obj);
GNUNET_free (rh);
return NULL;
}
rh->h_contract_terms = *h_contract_terms;
rh->coin_pub = *coin_pub;
rh->merchant = merchant_pub;
rh->rtransaction_id = rtransaction_id;
rh->refund_amount = *amount;
eh = TALER_EXCHANGE_curl_easy_get_ (rh->url);
if ( (NULL == eh) ||
(GNUNET_OK !=
TALER_curl_easy_post (&rh->ctx,
eh,
refund_obj)) )
{
GNUNET_break (0);
if (NULL != eh)
curl_easy_cleanup (eh);
json_decref (refund_obj);
GNUNET_free (rh->url);
GNUNET_free (rh);
return NULL;
}
json_decref (refund_obj);
GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
"URL for refund: `%s'\n",
rh->url);
ctx = TEAH_handle_to_context (exchange);
rh->job = GNUNET_CURL_job_add2 (ctx,
eh,
rh->ctx.headers,
&handle_refund_finished,
rh);
return rh;
}
void
TALER_EXCHANGE_refund_cancel (struct TALER_EXCHANGE_RefundHandle *refund)
{
if (NULL != refund->job)
{
GNUNET_CURL_job_cancel (refund->job);
refund->job = NULL;
}
GNUNET_free (refund->url);
TALER_curl_easy_post_finished (&refund->ctx);
GNUNET_free (refund);
}
/* end of exchange_api_refund.c */