/*
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 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
*/
/**
* @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
#include /* just for HTTP status codes */
#include
#include
#include
#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;
/**
* Information the exchange should sign in response.
*/
struct TALER_RefundConfirmationPS depconf;
};
/**
* 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 int
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 !=
GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_EXCHANGE_CONFIRM_REFUND,
&rh->depconf,
&exchange_sig->eddsa_signature,
&exchange_pub->eddsa_pub))
{
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 int
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);
return GNUNET_SYSERR;
}
have_deposit = false;
have_refund = false;
for (size_t off = 0; offdepconf.coin_pub
};
struct TALER_CoinSpendSignatureP sig;
struct GNUNET_JSON_Specification spec[] = {
GNUNET_JSON_spec_fixed_auto ("coin_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&dr.h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("h_wire",
&dr.h_wire),
GNUNET_JSON_spec_fixed_auto ("h_denom_pub",
&dr.h_denom_pub),
TALER_JSON_spec_absolute_time_nbo ("timestamp",
&dr.wallet_timestamp),
TALER_JSON_spec_absolute_time_nbo ("refund_deadline",
&dr.refund_deadline),
TALER_JSON_spec_amount_nbo ("deposit_fee",
&dr.deposit_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&dr.merchant),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (transaction,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
TALER_amount_hton (&dr.amount_with_fee,
&amount);
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_WALLET_COIN_DEPOSIT,
&dr,
&sig.eddsa_signature,
&rh->depconf.coin_pub.eddsa_pub))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if ( (0 != GNUNET_memcmp (&rh->depconf.h_contract_terms,
&dr.h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->depconf.merchant,
&dr.merchant)) )
{
/* deposit information is about a different merchant/contract */
GNUNET_break_op (0);
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);
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_RefundRequestPS rr = {
.purpose.size = htonl (sizeof (rr)),
.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND),
.coin_pub = rh->depconf.coin_pub
};
struct GNUNET_JSON_Specification spec[] = {
TALER_JSON_spec_amount ("refund_fee",
&refund_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&rr.h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&rr.merchant),
GNUNET_JSON_spec_uint64 ("rtransaction_id",
&rr.rtransaction_id), /* Note: converted to NBO below */
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (transaction,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (0 >
TALER_amount_add (&sig_amount,
&refund_fee,
&amount))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
TALER_amount_hton (&rr.refund_amount,
&sig_amount);
rr.rtransaction_id = GNUNET_htonll (rr.rtransaction_id);
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_REFUND,
&rr,
&sig.eddsa_sig,
&rr.merchant.eddsa_pub))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if ( (0 != GNUNET_memcmp (&rh->depconf.h_contract_terms,
&rr.h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->depconf.merchant,
&rr.merchant)) )
{
/* refund is about a different merchant/contract */
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (rr.rtransaction_id == rh->depconf.rtransaction_id)
{
/* Eh, this shows either a dependency failure or idempotency,
but must not happen in a conflict reply. Fail! */
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if (have_refund)
{
if (GNUNET_YES !=
TALER_amount_cmp_currency (&amount,
&rtotal))
{
GNUNET_break_op (0);
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);
return GNUNET_SYSERR;
}
}
{
struct TALER_Amount amount;
TALER_amount_ntoh (&amount,
&rh->depconf.refund_amount);
if (have_refund)
{
if (0 >
TALER_amount_add (&rtotal,
&rtotal,
&amount))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
}
else
{
rtotal = amount;
}
}
if (-1 == TALER_amount_cmp (&dtotal,
&rtotal))
{
/* dtotal < rtotal: good! */
return GNUNET_OK;
}
/* this fails to prove a conflict */
GNUNET_break_op (0);
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 int
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);
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_RefundRequestPS rr = {
.purpose.size = htonl (sizeof (rr)),
.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND),
.coin_pub = rh->depconf.coin_pub
};
uint64_t rtransaction_id;
struct GNUNET_JSON_Specification spec[] = {
TALER_JSON_spec_amount ("amount",
&amount),
GNUNET_JSON_spec_string ("type",
&type),
TALER_JSON_spec_amount ("refund_fee",
&refund_fee),
GNUNET_JSON_spec_fixed_auto ("merchant_sig",
&sig),
GNUNET_JSON_spec_fixed_auto ("h_contract_terms",
&rr.h_contract_terms),
GNUNET_JSON_spec_fixed_auto ("merchant_pub",
&rr.merchant),
GNUNET_JSON_spec_uint64 ("rtransaction_id",
&rtransaction_id),
GNUNET_JSON_spec_end ()
};
if (GNUNET_OK !=
GNUNET_JSON_parse (e,
spec,
NULL, NULL))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
rr.rtransaction_id = GNUNET_htonll (rtransaction_id);
TALER_amount_hton (&rr.refund_amount,
&amount);
if (GNUNET_OK !=
GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_REFUND,
&rr,
&sig.eddsa_sig,
&rh->depconf.merchant.eddsa_pub))
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
if ( (rr.rtransaction_id != rh->depconf.rtransaction_id) ||
(0 != GNUNET_memcmp (&rh->depconf.h_contract_terms,
&rr.h_contract_terms)) ||
(0 != GNUNET_memcmp (&rh->depconf.merchant,
&rr.merchant)) ||
(0 == TALER_amount_cmp_nbo (&rh->depconf.refund_amount,
&rr.refund_amount)) )
{
GNUNET_break_op (0);
return GNUNET_SYSERR;
}
}
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);
}
/**
* Submit a refund request to the exchange and get the exchange's
* response. This API is used by a merchant. Note that
* while we return the response verbatim to the caller for further
* processing, we do already verify that the response is well-formed
* (i.e. that signatures included in the response are all valid). If
* the exchange's reply is not well-formed, we return an HTTP status code
* of zero to @a cb.
*
* The @a exchange must be ready to operate (i.e. have
* finished processing the /keys reply). If this check fails, we do
* NOT initiate the transaction with the exchange and instead return NULL.
*
* @param exchange the exchange handle; the exchange must be ready to operate
* @param amount the amount to be refunded; must be larger than the refund fee
* (as that fee is still being subtracted), and smaller than the amount
* (with deposit fee) of the original deposit contribution of this coin
* @param h_contract_terms hash of the contact of the merchant with the customer that is being refunded
* @param coin_pub coin’s public key of the coin from the original deposit operation
* @param rtransaction_id transaction id for the transaction between merchant and customer (of refunding operation);
* this is needed as we may first do a partial refund and later a full refund. If both
* refunds are also over the same amount, we need the @a rtransaction_id to make the disjoint
* refund requests different (as requests are idempotent and otherwise the 2nd refund might not work).
* @param merchant_priv the private key of the merchant, used to generate signature for refund request
* @param cb the callback to call when a reply for this request is available
* @param cb_cls closure for the above callback
* @return a handle for this request; NULL if the inputs are invalid (i.e.
* signatures fail to verify). In this case, the callback is not called.
*/
struct TALER_EXCHANGE_RefundHandle *
TALER_EXCHANGE_refund (struct TALER_EXCHANGE_Handle *exchange,
const struct TALER_Amount *amount,
const struct GNUNET_HashCode *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_RefundRequestPS rr = {
.purpose.purpose = htonl (TALER_SIGNATURE_MERCHANT_REFUND),
.purpose.size = htonl (sizeof (rr)),
.h_contract_terms = *h_contract_terms,
.rtransaction_id = GNUNET_htonll (rtransaction_id),
.coin_pub = *coin_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,
&rr.merchant.eddsa_pub);
TALER_amount_hton (&rr.refund_amount,
amount);
GNUNET_CRYPTO_eddsa_sign (&merchant_priv->eddsa_priv,
&rr,
&merchant_sig.eddsa_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 = json_pack ("{s:o," /* amount */
" s:o," /* h_contract_terms */
" s:I," /* rtransaction id */
" s:o, s:o}", /* merchant_pub, merchant_sig */
"refund_amount", TALER_JSON_from_amount (amount),
"h_contract_terms", GNUNET_JSON_from_data_auto (
h_contract_terms),
"rtransaction_id", (json_int_t) rtransaction_id,
"merchant_pub", GNUNET_JSON_from_data_auto (
&rr.merchant),
"merchant_sig", GNUNET_JSON_from_data_auto (
&merchant_sig)
);
if (NULL == refund_obj)
{
GNUNET_break (0);
return NULL;
}
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->depconf.purpose.size = htonl (sizeof (struct TALER_RefundConfirmationPS));
rh->depconf.purpose.purpose = htonl (TALER_SIGNATURE_EXCHANGE_CONFIRM_REFUND);
rh->depconf.h_contract_terms = *h_contract_terms;
rh->depconf.coin_pub = *coin_pub;
rh->depconf.merchant = rr.merchant;
rh->depconf.rtransaction_id = GNUNET_htonll (rtransaction_id);
TALER_amount_hton (&rh->depconf.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;
}
/**
* Cancel a refund permission request. This function cannot be used
* on a request handle if a response is already served for it.
*
* @param refund the refund permission request handle
*/
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 */